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Technical guides for owner/manager of an air conditioning system: volume 10

Successful Case Studies in AuditAC

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Authors of this volume José Luís ALEXANDRE (University of Porto, Portugal) André POÇAS (INEGI, Portugal) Emanuel SÁ (INEGI, Portugal) �

The sole responsibility for the content of this publication lies with the authors. It does not represent the opinion of the European Communities. The European Commission is not responsible for any use that may be made of the information contained therein.

AustriaAustrian Energy Agency

BelgiumUniversité de Liège

ItalyPolitecnico di Torino

PortugalUniversity of Porto

AustriaAustrian Energy Agency

AustriaAustrian Energy Agency

BelgiumUniversité de Liège

BelgiumUniversité de Liège

ItalyPolitecnico di Torino

ItalyPolitecnico di Torino

PortugalUniversity of Porto

PortugalUniversity of Porto

SloveniaUniversity of Ljubljana

UKAssociation of Building

Engineers

BRE (Building Research Establishment Ltd)

Welsh School of Architecture

SloveniaUniversity of Ljubljana

SloveniaUniversity of Ljubljana

UKAssociation of Building

Engineers

UKAssociation of Building

Engineers

BRE (Building Research Establishment Ltd)

BRE (Building Research Establishment Ltd)

Welsh School of Architecture

Welsh School of Architecture

Eurovent-CertificationEurovent-Certification

Team

France (Project coordinator)Armines - Mines de Paris

France (Project coordinator)Armines - Mines de Paris

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CONTENTS

SCOPE OF THE PROJECT ...................................................................................4

INTRODUCTION OF CASE STUDIES ..................................................................4

HIGHLIGHTS FROM CASE STUDIES..................................................................7

Office Buildings ............................................................................................................................................ 7

Hospital Buildings .......................................................................................................................................11

Commercial Building ..................................................................................................................................12

Other Service Buildings ..............................................................................................................................12

WELL DOCUMENTED CASE STUDIES..............................................................15

RESULTS AND ENERGY POTENCIAL IMPROVES............................................27

General energy Improves............................................................................................................................27

Equipment Replacement.............................................................................................................................28

DETAILED INFORMATION FOR AC CASE STUDIES .......................................29

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SCOPE OF THE PROJECT The Propose of the AuditAC The aim is to demonstrate how much advantage can be taken from the implementation of the inspection of air conditioning systems. More than the inspection itself, the project promotes audit procedures as the real and effective method to reach such energy savings. The inspection characteristics are analyzed and an effort is made, in collaboration with the European standardization body CEN, to modify and adapt the standard inspection for detecting actual system’s problems. A number of tools are developed to help auditors; inspectors and energy managers identify the most important energy conservation opportunities in existing AC systems and to avoid the most common errors that lead to a waste of energy. Moreover, AuditAC attempts to reach all actors of the air-conditioning market (manufacturers, installers, maintenance staff, etc.), in order to involve them in the procedure of equipment auditing, make the audit procedure easier and, furthermore, improve the acceptance of the audit itself. Throughout all project a database called AUDIBAC was developed for the building owners and respective systems. This data base will inform the users about the best solution to increase the efficiency in what concerns to energy of the buildings system. It is a tool of great importance for the effective accomplishment of the auditing procedures in AC systems. This tool will be responsible for the creation of results in line with the EPBD requirements, from the viewpoint of both the customer and the auditor.

INTRODUCTION OF CASE STUDIES To develop this data base, it became extremely necessary to know well different cases of application of air conditioned systems at a European level. In fact that Europe present different climatic areas and consequently different types of building envelope turns the knowledge of the system operation for each case very important. The case studies for the database were developed by the several partners in the AuditAC project, Austria, Belgium, France (project coordinator), Italy, Portugal e Slovenia and UK.

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No Name and Location

Off

ice

Hos

pita

l

Info

rmat

ics

Aud

itoriu

m

Libr

ary

Labo

rato

ry

Res

earc

h C

ente

r

Com

mer

cial

Arc

hive

Cul

tura

l Dpt

.

1 ACS-1 Salzburg, Austria ● 2 ACS-2 Linz, Austria ● 3 BCS-1 Namur, Belgium ● 4 BCS-2 Brussels, Belgium ● 5 BCS-3 Liège, Belgium ● 6 FCS-1 Orleans, France ● 7 FCS-2 Paris, France ● 8 ICS-1 Turin, Italy ● 9 ICS-2 Vercelli, Italy ●

10 ICS-3 Oderzo, Italy ● 11 ICS-4 Bologna, Italy ● 12 PCS-1 Porto, Portugal ● 13 PCS-2 Porto, Portugal ● 14 PCS-3 Porto, Portugal ● 15 PCS-4 Porto, Portugal ● 16 PCS-5 Porto, Portugal ● 17 SCS-1 Maribor, Slovenia ● 18 UKCS-1 Leicester, UK ● 19 UKCS-2 Westminster, UK ● 20 UKCS-3 Cardiff, UK ● 21 UKCS-4 Cardiff, UK ● 22 UKCS-5 Cardiff, UK ● 23 UKCS-6 Oxford, UK ● 24 UKCS-7 London, UK ● 25 UKCS-8 London, UK ● 26 UKCS-9 London, UK ●

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Case studies will concern different sizes and types of buildings, which are classified by building type (functionality) and by type of HVAC system. This classification makes possible the comparison between the different case studies and allow for the first time to estimate on a statistical basis the magnitude of the gains possible on European A/C installations as well as to give a list of possible malfunctions of the equipment, which the auditor can probably find during the audit phase. Building type Classification:

Office buildings (O) Hospitals (H) Commercial (C) Other Service Buildings (S)

HVAC system Classification:

Centralized Primary system (PS)

- Chiller - Boiler - Heat Pump - Thermal Storage

Secondary system (SS) - Air base system - Water based system

Non Centralized DX system

- Split - Multi Split

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- VRF - Heat Pump

HIGHLIGHTS FROM CASE STUDIES Office Buildings

BCS 1 – Namur Case: This case aimed at assessing and managing the HVAC system installed in an office building located in the center of the town of Namur. Installed HVAC system: Heating – three gas boilers with variable flow to feed radiators and AHU’s. Cooling – two chillers with reciprocating compressors and air condensers with variable flow to feed AHU’s and fan-coils. HVAC system modifications: During the audit phase the cooling and ventilation performances were not as expected. Alteration of the control strategy, the implementation of new parameters and administration rules, the regulation of the set points and of the VAV boxes thermostats were some of the modifications for this case. Lessons learned: After commissioning, most of the errors were eliminated but some of the problems continue to exist. Modeling some retrofit opportunities can increase further more the heating and cooling performances of the installed system.

BC

S 1

Nam

ur

FCS

– 1

Orle

ans

PCS

5 - P

orto

SCS

– 1

Mar

ibor

UK

CS

1 Le

ices

ter

AC

S-2

- Lin

z

ICS-

2 - V

erce

lli

ICS-

3 - O

derz

o

PCS-

1 -

Porto

PCS-

2 - P

orto

PCS-

3 - P

orto

PCS-

4 - P

orto

AC

S-1

- Sal

zbur

g

ICS-

1 - T

urin

BC

S-2

- Bru

ssel

s

UK

CS-

3 - C

ardi

ff

BC

S-3

- Lie

ge

UK

CS-

2 - W

estm

inst

er

UK

CS-

4 - C

ardi

ff

UK

CS-

5 - C

ardi

ff

UK

CS-

6 - O

xfor

d

UK

CS-

7 - L

ondo

n

UK

CS-

8 - L

ondo

n

UK

CS-

9 - L

ondo

n

FCS-

2 - P

aris

O O O O O H H H S S S S S S O S S O C O O O O O O

- Chiller • • • • • • • • • • • •

- Boiler • • • • • •

- Heat pump • PS

- Thermal storage • •

- Air based system • • • • • • • • • • • • • •

Centralized

SS - Water based system • • • • • • • • • •

Not Centralized

- Split • • •

- Multi Split •

- VRF • • • • •

HV

AC

Sys

tem

Typ

e

DX system

- Heat pump •

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BCS 2 – Brussels Case: This case is about a 13 story office building. Installed HVAC system: The installed HVAC system is composed by 4-pipe terminal units, AHU’s, Chiller, boiler, cooling towers and circulation pumps. HVAC system modifications: There are some suggestions made in order to improve the system performance. The AHU’s were partially renovated and all induction units and thermostatic valves were replacement. The replacement of existing induction units by more efficient devices (other induction units or fan coils), should make possible to run the system with higher chilled water temperature and therefore better COP. Lessons learned: Other options can always be considered to improve the systems efficiency; even small ones can produce a big effect when you have a big building with a large system.

NO PHOTO AVAILABLE

FCS 1 – Orleans Case: This case is about a refrigeration plant of a commercial company. They started having problems with the high energy bills, so the target to start reducing the energy consumption was the cooling production unit. Installed HVAC system: The system installed was composed by centrifugal compressors groups functioning in stages. This system was oversized and used forbidden refrigerant according with the actual regulations. HVAC system modifications: The modifications consisted on the substitution of the cold production unit by one other, adapted to the cold demand and modulated in stages. Lessons learned: The real saving reached 56 % of the electricity from the cold production groups.

FCS 2 – Paris Case: audit preformed to an office building located in the Paris suburbs. The building has one floor and a basement. Its overall clear surface is 1140 m ². The building can be divided into three types of spaces: circulation zones, conference offices and rooms. Installed HVAC system: The five conference rooms are climatized by an AHU and a group of cold water production. About thirty offices have AC based on 2-pipe fancoils and natural ventilation. The cold water that feeds the loop of the AHU and the fancoil is produced in a non-reversible alternative Chiller. The system operates 24 h /24 and 7 days/7. HVAC system modifications: Two main improvement scenarios were foreseen: the first scenario consist in keeping air conditioning in summer and the heating with Joule effect in winter; the second scenario would be the replacement of the refrigeration unit by a reversible heat pump with an average seasonal COP of 2,5. Associated with these two scenarios other measures were proposed in order to reduce the energy consumption: Change the water loop set points, change the functioning schedules, reduce the internal gains etc. Lessons learned: This study shows that the improvement scenarios combined with other measures can result in a decrease from 30% to 77% of the HVAC system energy consumption.

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SCS 1 – Maribor Case: This case relates a high efficient system for an office building. At minimal energy consumption, thermal comfort and good work conditions are achieved. The investment costs are similar with the traditional buildings. Installed HVAC system: The building is heated with a combined heat-pump (water-water) which provides heating and cooling energy. As a support for heating there is also a low temperature condensing gas boiler. Whole space is ventilated with high energy efficient ventilation / air conditioning units with energy recovery more than 90%. There is also a possibility of direct cooling with ground water. In summer period, it has a temperature of 15 – 16ºC. HVAC system modifications: This study only intents to present a case of good performance, so there are no modifications. Lessons learned: It is possible to have a high efficient HVAC and obtain good levels of comfort without much more than an usual building.

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UKCS 1 – Leicester Case: This case illustrates an exceptionally energy efficient/low energy air conditioning system. This is a 4 storey office building. Installed HVAC system: The HVAC cooling system consists on chilled beams. The cold water production unit is a package air cooled chilled using R407c as refrigerant. HVAC system modifications: There are no modifications suggested Lessons learned: This building seems to be very energy efficient according to is overall annual energy consumption/m2 when compared to national benchmarks.

NO PHOTO AVAILABLE

UKCS 2 – Westminster Case: This case study aimed at assessing the energy performance and its potential for improvement, of a comfort cooling system installed in a UK office building. The building comprises six-storeys (Ground plus 5) of mainly small cellular offices and a lower ground containing support and storage areas. Installed HVAC system: The basic system configuration features passive chilled ceilings and perimeter passive beams with night-time ice storage and some DX systems serving computer rooms and conference suites. Ventilation is provided mechanically via centralised AHU’s and heating is provided by perimeter radiators. HVAC system modifications: This case study focus on the actual system analysis, thus no modifications were implemented. Lessons learned: Detail thermal simulation tool can be very helpful to predict HVAC system consumption and consequently avoid some errors in the project or correcting them during an Audit.

UKCS 3 – Cardiff Case: This case study compares the energy consumption values obtained using thermal simulation tools such as EnergyPlus with real energy measurements. Installed HVAC system: The HVAC system installed is a 2-pipe Multi-Split DX system. This system has the possibility to free cool the spaces. HVAC system modifications: This study focus on the actual system analysis, thus no modifications were tested. Lessons learned: Detailed thermal simulation tool can be very helpful to predict HVAC system consumption and consequently avoid some errors in the project.

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NO PHOTO AVAILABLE

UKCS 5 – Cardiff Case: This case study aimed at assessing the energy performance and its potential for improvement, of a comfort cooling system installed in a small administrative office, located in a historic building of Cardiff University. Installed HVAC system: The office has a DX split comfort cooling system with a roof mounted condenser and a 4-way ceiling mounted cassette. HVAC system modifications: This case study focus on the actual system analysis, thus no modifications were implemented. Lessons learned: Detail thermal simulation tool can be very helpful to predict HVAC system consumption and consequently avoid some errors in the project or correcting them during an Audit.

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UKCS 6 – Oxford Case: This case study aimed at assessing the energy performance and its potential for improvement, of a comfort cooling system installed in a light industrial building on a small rural estate near Oxford. The conditioned area consists of a large open plan office, 3 cellular spaces of executive offices, a conference room and a production area room. Installed HVAC system: This area is serviced by VRF indoor units, ceiling mounted, from external condensers on a 2-pipe heating and cooling “change over” only basis. The supply AHU consist of an in-duct axial fan, filter pack and electric heater battery. The system has plenum return ventilation with ducted supply and partial recirculation in the fan-coil units. HVAC system modifications: This case study focus on the actual system analysis, thus no modifications were implemented. Lessons learned: Detail thermal simulation tool can be very helpful to predict HVAC system consumption and consequently avoid some errors in the project or correcting them during an Audit.

NO PHOTO AVAILABLE

UKCS 7 – London Case: This case study aimed at assessing the energy performance and its potential for improvement, of a comfort cooling system installed in the ground floor of a 2 storey office block. The conditioned area consists of open plans and cellular office rooms, meeting rooms, training rooms and a reception. Installed HVAC system: The conditioned area has a 2-pipe fan-coil system with the electrical reheat, supplied by two reverse cycle air-cooled chillers. The indoor units are a 2-pipe ceiling mounted cassettes with multi-speed fans and electrical reheat in the perimeter units. HVAC system modifications: This case study focus on the actual system analysis, thus no modifications were implemented. Lessons learned: Detail thermal simulation tool can be very helpful to predict HVAC system consumption and consequently avoid some errors in the project or correcting them during an Audit.

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UKCS 8 – London Case: This case study aimed at assessing the energy performance and its potential for improvement, of a comfort cooling system installed in the first floor of a 2 storey office block. The conditioned area consists of open plans and cellular office rooms, meeting rooms. Installed HVAC system: 3 pipe heat recovery VRF units with roof mounted condensers and internal ceiling mounted cassettes. The cassettes draw air from the ceiling void that is also supplied with fresh tempered air from the mechanical ventilation system. The entire building is mechanically ventilated with a 2-duct supply and return system, within the air handling unit located in the roof top plant room. HVAC system modifications: This case study focus on the actual system analysis, thus no modifications were implemented. Lessons learned: Detail thermal simulation tool can be very helpful to predict HVAC system consumption and consequently avoid some errors in the project or correcting them during an Audit.

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NO PHOTO AVAILABLE

UKCS 9 – London Case: This case study aimed at assessing the energy performance and its potential for improvement, of a comfort cooling system installed in a 2 storey office block. The conditioned area consists of open plans and cellular office rooms, meeting rooms. Installed HVAC system: The conditioned area has a custom Built AHU. The packaged roof top units are VRV condensers with 3 pipe Heating/Cooling and heat-recovery unit, believed to be operating as modular banks of 7 per floor. The ground and first floor ceiling voids contain in total 56 Daikin VRV 3-pipe heat and cooling ceiling cassettes. HVAC system modifications: This case study focus on the actual system analysis, thus no modifications were implemented. Lessons learned: Detail thermal simulation tool can be very helpful to predict HVAC system consumption and consequently avoid some errors in the project or correcting them during an Audit.

PCS 5 – Porto Case: This case is about the INESC building located in the campus of Porto’s faculty of engineering. This is a typical 4 stories service building. Installed HVAC system: The HVAC system is centralized and composed by a boiler, a chiller and two ice storage tanks. The air distribution is done by using fan coil units. HVAC system modifications: The main tested alteration consists on the reprogramming of the central control unit in order to provide the use of free cooling whenever possible. Lessons learned: The use of free cooling is estimated to offer an energy saving potential by the order of 28% year.

Hospital Buildings

ACS 2 – Linz Case: This case concerns with the optimization of the refrigeration plant existent in the central hospital of Linz. Installed HVAC system: The refrigeration plant is equipped with a 6-cilynder 2-stage compressor. The heat rejected can be collected and used for heating water. HVAC system modifications: The modification was basically the replacement of the 6-piston compressor for a 6 screw compressor with 40% more of cooling capacity. Lessons learned: The saving potential was even higher than estimated, achieving 30-35%.

ICS 2 – Vercelli Case: This case intents to show the optimization of a hospital AHU that treats the air from a surgery room. Measurements were done and the data collected will be used to assess the system’s efficiency. Installed HVAC system: The actual installed HVAC is a centralized system (with AHU, chiller and water loops). HVAC system modifications: In order to improve the system’s efficiency several solutions were studied, such as the substitution of the chiller, the capability to use free cooling and the heat recovery from the condenser units. Lessons learned: Several economic and energetic analyses were done. The use of two new chillers in partial load instead of three installed ones can achieve savings on the order of 1460 €/yr. Savings associated to a one degree variation in the limit temperature at which the chillers are shut off and free cooling is adopted (23°C vs 22°C) are approximately equal to 50000 kWh/yr (with negligible differences between existing and new chillers), i.e. on the order of 12%.This demonstrates that there is an opportunity for cost effective energy saving measures.

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NO PHOTO AVAILABLE

ICS 3 – Oderzo Case: This case is about a 3-storey hospital building. Installed HVAC system: 100% external air AHU. This unit has humidifier, fans, HEPA filters, cooling coil and heating coil. HVAC system modifications: In order to improve the system’s efficiency several solutions were studied such as free-cooling with an achieved energy reduction of 16% and heat recovery. The average thermal effectiveness of the intermediate-fluid heat recovery system turned out to be on the order of 58% (based on measurements) and for an air-to-air heat exchanger 65%. Lessons learned: This case study has allowed a quantification of the impact of AHU operation on the electrical energy consumption of an all-air AC system for a hospital. It shows as well that some energy saving measures can be implemented with good results.

Commercial Building

NO PHOTO AVAILABLE

UKCS 4 – Cardiff Case: This case study aimed at assessing the energy performance and its potential for improvement, of a comfort cooling system installed in a small commercial architectural practice operating as part of the Welsh School of Architecture (WSA). Installed HVAC system: DX splits were installed for comfort cooling. The system has roof mounted condensers and wall mounted slim-line cassettes. HVAC system modifications: This case study focus on the actual system analysis, thus no modifications were implemented. Lessons learned: Detail thermal simulation tool can be very helpful to predict HVAC system consumption and consequently avoid some errors in the project or correcting them during an Audit.

Other Service Buildings

BCS 3 – Liège Case: This case is about a laboratory located in Liege, Belgium. The conditioned floor area is 4000 m2. This building contents a set o offices, meeting rooms, dinning hall and laboratories. Installed HVAC system: The installed HVAC system is composed by Terminal Units such as Fan coils and a AHU that supplies conditioned fresh air using textiles diffusers. The AHU and the Fan coil units are fed by water loops. The hot water is produced by a boiler and the cold water by chillers. HVAC system modifications: This study only indicates retrofit opportunities no modifications were made in the installed system. Lessons learned: Better distribution of the hot water temperature to the actual space heating demand and another mode of sanitary hot water production seems to provide reduce de gas consumption. A recovery heat pump could be used with extracted air as cold source in order to enhance heat recovery from AHU.

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PCS 1 – Porto: Case: This case is about a computer center existing in the Faculty of Engineering of Porto University. The rooms in analysis are 4 and are in function all year to guarantee the functioning of the faculty’s computer network and internet. Installed HVAC system: the system installed is not centralized. Each room has independent cooling units. The units existent are basically DX close control and single split units. HVAC system modifications: The proposed modification for this case consists on the substitution of the actual DX units for a centralized system, being the chilled water loop fed by a chiller and the hot water loop fed by a boiler. One other fundamental change was the introduction of the possibility for the system to free cool the spaces given favorable outdoor temperature conditions. Lessons learned: The main achievement was the use of free cooling as well as the savings due to the increase of the chiller efficiency (EER). These measures result in a 70 % decrease of the compressors functioning hours and in an overall 30% electric energy reduction.

PCS 2 – Porto: Case: This is the case of three auditoriums existent on the Faculty of engineering. These auditoriums are equipped with an Air-Air type system. The analysis done to this rooms was merely acoustic. Installed HVAC system: This air-to-air system is composed by roof-top units (one per room) and heat pumps to provide the heating and cooling energy. This unit mixes fresh air with return air. Given favorable conditions, the control strategy is prepared to allow free-cooling. HVAC system modifications: The proposed modifications are focused on the ventilation system. Some modifications were done in order to reduce the noise level inside the rooms. Modifications like the displacement of the mixing box or the placement of acoustic attenuators were tested. Lessons learned: The acoustic comfort can be achieved with parallel improvements on the indoor air quality and energy efficiency.

PCS 3 – Porto: Case: This case relates to library in the Porto’s faculty of engineering. This is an 8 stories building that works from Monday to Friday. This case study intents to assess and resolve a comfort problem reported by the library users. Installed HVAC system: the system installed is centralized. There’s a boiler and a chiller on the roof that feed the chilled and hot water loops respectively. The air loop is handled by an air handling unit. HVAC system modifications: The proposed modification for this case consists on the use of CO2 as the fresh air control indicator, the change of the lighting density to 8 W/m2, use of vertical and horizontal shading devices on the south facing windows and the alteration of the set-point temperatures. Lessons learned: All these measures resulted in energy savings. By combining some of these actions the building can archive 43 % energy reduction.

PCS-4 – Porto: Case: These case intents to study the influence of the AHU filters conditions on the ventilation energy consumption in a laboratory room located within FEUP. Installed HVAC system: The studied AHU is composed by two fans, electric resistances for heating and a DX system for cooling. The filters tested were placed on the fresh air inlet side. HVAC system modifications: The modification done was basically to substitute a dirty filter by a new one, and monitor the fan motor energy consumption. Lessons learned: The lack of the filters maintenance reduces the indoor air quality, and leads to energy waste by the fan motors.

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ACS 1 – Salzburg Case: This case relates the energy consumption changes in a new archive building along with the years and with several interventions in the system in order to decrease the energy consumption. Installed HVAC system: There’s no pertinent information about the cooling system. HVAC system modifications: The modifications done were mainly on the system control and management. Lessons learned: A good management of the system can, without further equipment modification, achieve much higher energy efficiency. In this case energy savings achieved 70%.

ICS 1 – Turin Case: This case is about an office building in Turim that renewed the HVAC system. However this new system seemed to be inadequate. Thermal simulation tools were used to assess other HVAC equipments in terms of energy consumption and thermal comfort. Installed HVAC system: The HVAC system installed is composed by embedded floor radiant panels and AHU’s. HVAC system modifications: The most important simulated modification were basically the use of AHU with fan-coil units instead of radiant floor and the substitution of the heating oil burner for a natural gas boiler connect the system to the gas network. Lessons learned: The results obtained using simulation show that a 25% of the HVAC energy saving can be spared.

ICS 4 – Bologne Case: This case study was aimed at analyzing the performance of a water-to-water reversible heat pump installed in a research center located in Apennine mountain. Installed HVAC system: The AC is an air-and-water system type (primary air and two-pope fan coils). Hot and chilled water is produced with a water-to-water reversible heat pump, using treated lake water that feeds the AHU and FCU’s. HVAC system modifications: This study focus on the actual system analysis, thus no modifications were implemented. Lessons learned: The presence of a BEMS makes it possible to monitor and record the main system operational parameters. The seasonal average COP for the installed system is equal to 3.9 and a good correlation between daily cooling energy and outdoor dry-bulb air temperature was identified.

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WELL DOCUMENTED CASE STUDIES Twenty Six case studies were analyzed. Among these, 6 were considered to be the well document case studies. This selection was carefully made so that we could extrapolate AC systems in terms of typology of the buildings allover Europe. Below are the case studies considered to be the best document examples and their location.

CICA - Informatics Center • FEUP, Porto The building has three floors and the ground floor is the centre of informatics resources. The function of this building is mainly to ensure and make available all the informatics services for the FEUP community and to uphold its innovation and use. The cooling power installed in these spaces is not enough to remove the total load that occurs inside the building, which causes a high indoor air temperature leading to harmful situations, causing damages and reducing the performance of the informatics hardware. The original HVAC is a non centralized VRF system where the local cooling units are ceiling splits and close control units with an outdoor condenser unit. Problems

• Actual HVAC system is not adjusted to the demand • The internal loads are higher than the installed HVAC system, causing the

damage and reducing of the performance of the informatics hardware.

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• In summer the indoor comfort is more challenging

Solutions – Major Modifications The solution proposed is, in energetic and environmental field, the most adjusted since it is a centralized system and has a higher efficiency. This solution also allows the power increase without major costs.

The considered HVAC system can be defined as an air/water system. It will be composed by a cold-water central producer (chiller), located in the building covering, and by a cold water distribution net with two pipes, for supply and return. This circuit will supply the existing cooling coils in the independent Close Control units. These units are located inside the acclimatized spaces or, guarantee the indoor air quality. This system will also include the possibility of free-cool the spaces, given the adequate exterior air conditions.

The following equipments form the proposed system:

- Chiller with scroll compressor with 100 kW of cooling capacity; - Four Close Control units supplied with cold water which integrates system of

humidification and electric resistance for heating; - Ventilation, piping and control system

Accomplished improvements: The energetic and power consumptions of the existing Close Control units in the 4 zones, obtained through dynamic simulation, are 128 MWhe/year. It should be noted that this analyses considers the consumption of the compressor, the ventilation, the reheat coils and humidification. Using once again the dynamic simulation, the obtained energy consumption for the proposed solution is 87 MWhe/year.

The new system with free-cooling and electrical reheat is much more effective than the others, except the system which uses hot water for reheat. However this system would require a boiler so the system would consequently become more complex and expensive.

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As it is verified the energy earnings, of the floor -1, with the substitution of the current system for the proposed, they are of 41 MWh. This value corresponds to 2.870,00 Euros a year of economic won (the price of the electric energy was esteemed in 0,070 €/kWh). The proposed solution presents certain advantages when compared with the existing system:

The cooling capacity can be increased with the connection of one or more chillers. According to the type of equipment, it is possible to connect them and optimize its functioning. All these systems allow a centralized management and partial loads according to the thermal needs. The circulation fluid is water, which do not present any restriction or danger as refrigerant fluids. When necessary, the upgrade of the indoor power is simple and easy to implement. The terminal units could be independent of the cold unit production, in what refers to the mark, model or type. The lifetime of this equipment is always higher then that of splits units.

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Office Building • Maribor The energy system of an office business building is presented, where at minimal energy consumption, optimal working conditions are achieved. The investment costs are in the same range as the investment costs for a traditional building. Building is heated with a combined heat pump (water – water), which prepares heating and cooling medium for the whole building. Heating source is ground water from a spring. Heat and cooling energy are partly transmitted into the object by thermal activation of concrete construction and by supplied air of ventilation units. Local regulation of temperature is possible through local heating coils, built in special displacement air distributors. Whole space is ventilated with high energy efficient ventilation / air conditioning units with energy recovery more than 90%. Problems There are no problems reported for this building. In fact, this case study aims to report that is possible to combine technology, comfort and reasonable expenses.

Accomplishments: As said, the building was designed to achieve high energy performance thus reducing the energy consumption. This global goal was approached by several sides: the building envelope [sun exposure and wall and glazing materials] and the HVAC systems installed. The glazing is a two – layer glass type, argon filled. It is combined with high quality aluminium profiles, with interrupted thermal bridges, thermal insulated. There is also a lot of innovative details of interruption of thermal bridges at connections glazing to concrete constructions. Performance of the cooling system is optimized for lowest possible energy consumption. Big amount of sensible heat is cooled with thermal activation of concrete construction it goes on large surface area, which means high cooling medium temperature – low energy consumption.

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The basic heat source is underground water. In winter it has a temperature around 10-13°C,o on the other side, we have thermal activated concrete construction with large heat areas, which means extremely low temperature heat medium of 25 – 26ºC, which assures that the heat pump works with a excellent coefficient of performance (COP) 5-6. Comfortable working conditions for employees are also achieved with a permanent supply of fresh air into the rooms with three air-changes per hour. Ventilation with 100% of fresh outside air wouldn’t be rational if it wasn’t done with ventilation and air conditioning units that have heat recovery of 92 % and humidity recovery of 87% at the lowest outside temperatures. In summer the air conditioning units also dehumidify the outside - inlet air when it is necessary, which assures comfortable working conditions even at extreme conditions of the outside air. All these design characteristics led to a real high energy performance. The results obtained after 24 month of operation revealed that the building is indeed efficient.

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Office Building • Brussels Description: This is a medium size office building (28 000 m2) erected in centre of Brussels at end of the sixties. This building is constituted by open plan offices and (a few) meeting rooms. The whole building has an air conditioned system with the exception of the car park. The original HVAC system is four pipe induction units in all offices and CAV/VAV systems in other zones. Classical heating and cooling plant, with fuel oil boilers and vapor compressions chillers with cooling towers. Control Strategy: The building is equipped with a classical BEMS with two levels: a set of local control units and a PC for supervisory management. The comfort must be satisfied from 7 am to 8:30 pm, five days per week. The BEMS is imposing an earlier re-start, according to weather conditions. There are also some special requirements for the (prestigious) ground floor: the air conditioning is required there all along the year in order to protect the (exotic wood) decoration! Indoor air temperatures are measured at three different locations of each floor (except for floors 5 and 6). The average of all these temperatures is used by the BEMS in order to fix the primary air temperature. The primary air is only supplied during pre-heating and occupancy time. Outside that time, if the weather is very cold, the induction units are still used in free convection mode, by supplying hot water to the heating coils.

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Accomplished improvements and Retrofit Opportunities: An attempt of free chilling was done sometime ago, by adding a water-to-water heat exchanger between the condenser and the evaporator circuits (in parallel to the chillers). For reasons still to be investigated, this experience failed and the system was dismantled. The AHU’s were partially renovated and the replacement of all induction units and thermostatic valves is now projected. The replacement of existing induction units by more efficient devices (other induction units or fan coils), if fitting in the small space available, should make possible to run the system with higher chilled water temperature and therefore better COP. The environmental control should also be made more accurate. More indoor temperature sensors will be installed in the occupancy zone for better control of set-points. But much other retrofit potential should be considered: - Variable rotation speed for pumps and fans - Optimal control of chilled water temperature - Energy recovery loops between supply and exhaust air circuits - Air recirculation - Optimal control of cooling towers - Free chilling (again!) - Chiller condensers heat recovery - Use of chillers in heat pump mode (when no more used for cooling)

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Archive Building • Salzburg Description: This case study relates to a building built in 2003/04. This building has it the energy consumption measured online by an energy monitoring system. In the first months high energy consumption was registered. It was thought that this high energy consumption was due to the fact that the building had been recently constructed. Optimization measures were taken in order to reduce the energy consumption. It was possible to reduce the consumption by about 40%. During August and September the regulation and cooling system companies cooperated in order to increase energy efficiency in the system. From this cooperation resulted a 60% reduction in the energy consumption. The year of 2005 brought the evidence that is possible to reduce the consumption by more than 70% Problems: The main problem detected in this building was the high energy consumption. The systems were not functioning properly. It was realised that the range for the air was too small. When the room temperature was too high, the climate cabin started to cool the room. The result was that the room became too colt and than the heating system had to start heating the room. The system was continuously cycling between on and of mode.

Accomplishments: After the detection of the problem several modifications were made. The combined work of both regulation systems and cooling system companies resulted in an energy consumption decrease of about 70%

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Cultural Building • Turin Description: The building of the culture department is situated in the historic centre of Turin has five floors, building houses administration offices of the City Council and a library. The old building was renovated in 1996 when a new HVAC was installed, but over the years this system has been seen to be inefficient and not adequate for the building’s needs.

The actual HVAC system is constituted by: primary air plant, embedded floor radiant panels supplied with warm water in winter and cold in the summer. Problems:

The HVAC system is formed by embedded floor radiant panels that cool the environment, without relative humidity control. The humidity is controlled by different AHU’s in the building. In winter this system works well, in fact the air is heated and humidified by the AHU and the embedded floor radiant panels function correctly. In summer, however, the temperature of the water circulating in the panels cannot go under 18°C or there are problems of condensation and mildew and the single primary air plant cannot maintain the correct environmental conditions. The distribution of air produced by the various AHU, located on each floor of building, passes through rectangular or circular channels with run in the corridors. In summer, the distribution of air in areas distant from the AHU’s is not enough to guarantee maintenance of optimal temperature and air control conditions, in fact the people that work inside these offices experience some problems.

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Proposed Solutions: Change the embedded floor radiant panels to fan-coils. The new HVAC system can still be defined as air/water system but, it will be composed of AHU’s for ventilation, and cold – hot water distribution for the fan-coils. Use a suitable BMS, the system is already predisposed with a specific control console and suitable software. Strengthen the fan of the various AHU’s because the existing fans are insufficient to force air to the offices distant from the AHU Intensify the maintenance of the fittings that is currently performed by an external firm and the inspection of the components by the administration. Use electricity meters to download electric consumption on an hourly and daily basis, in order to collect further information for an effective audit of the building. Change the burner that is currently installed (heating oil) to a methane model and connect the system to the gas distribution network.

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Archway House – Office Building • Cardiff Description This building, located in Cardiff-Wales, is an office building with the respective office functioning profile. This case studied intents to assess whether or not thermal simulation tools can provide an interesting and reliable tool in energy auditing. The building here presented is equipped with VRF multi/split systems with the capability to use free/cooling whenever possible. Electrical energy consumption data was collected for June, July ad August. The aim is to simulate the building in a thermal simulation tool and then compared the simulated values with the real ones. To see if values obtained by simulation are reliable, and thus The software used was the EnergyPlus and the weather data used was real data for the same period as the electric measurements. The heating was not assessed; the aim is only to assess the cooling performance. Only one of the spaces, AC_zone, has a cooling system. It is intended an internal temperature of 24 ºC, during the labor hours. There is a 2-pipe cooling Multi-split DX system with the following known characteristics: Rated Power Consumption: 35.4 kW Total Cooling Capacity: 75 kW There is also a free-cooling system, on whenever the outdoor temperature is lower than 17.5 ºC. This system allows a great energy saving, especially in locations with low summer temperatures, as it is the case of Cardiff.

Solutions encountered using simulation software:

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From the breakdown analysis it can be concluded that the following ECOs could be used to help reduce the cooling energy demand in the building:

- ECO E4.5 – Replace electrical equipment with Energy Star or low consumption types.

- ECO E4.9 – Move equipments (copiers, printers, etc.) to non conditioned zones. Electrical equipment loads are the highest loads among the internal gains in this case, therefore any possibility to reduce the amount of energy they use and release should be considered. Most of the copiers and printers, etc in this case are in the conditioned zone, relocation to non conditioned areas could also be considered to reduce the cooling loads.

- ECO E4.7 – Modify lighting switches according to daylight contribution to different areas.

- ECO E4.8 – Introduce daylight/occupation sensors to operate lighting switches. Electrical lighting seems to be on all the time according to the survey and its contribution to the cooling demand is considerable.

- ECO E2.1 – Generate possibility to open/close windows and doors to match

climate. Ventilation should be used as much as possible as a free cooling source as the outside air temperature tends to be lower that the inside air temperature.

- ECO E1.1 – Install window film or tinted glass.

- ECO E1.3 – Operate shutters, blinds, shades, screens or drapes.

Solar control should be used to reduce the cooling loads, even though it is not the highest contributor to it.

- ECO O2.2 - Shut off A/C equipments when not needed.

The ancillary equipment to the A/C system is apparently consuming 3kW even when then system is providing no cooling. The relatively short period of time that this system provides cooling means that this load becomes a very significant component of the overall energy use, and reduces the overall COP dramatically.

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RESULTS AND ENERGY POTENCIAL IMPROVES General energy Improves In general overview, the observed potential energy savings in different real examples can be subdivided in a few audit strategies, such as:

1. management system control optimization 2. efficiency control of the equipment energy consumptions 3. lighting efficiency control 4. new strategies of recovery energy 5. free-cooling strategy implementation 6. simply chiller equipment replace

To achieve a good Potential Energy savings strategy the building’s owner (or auditor) must to know well the energy utilization such as:

• running hours of AC and the length of pre-cool period; • internal comfort conditions, ie temperature, humidity, lighting levels; • localization of the unnecessary AC and lighting, I e unoccupied zones; • chillers/pumps schedules and settings; • specific equipment energy consuming • lighting energy consuming • the areas of high energy consumptions

In Europe, and in particular countries, it is possible to have an idea of the energy utilization for the office building sector. Therefore, the auditor know, in the first approach, how is the potential energy saving that can achieve if applied different strategies that presented above. The figure shows the average energy end-user breakdown typical for the European office building sector.

Lights33%

Equipments40%

HVAC27%

Energy end-user breakdown from Belgium CS1

HVAC 25% - 30%LIGHT 30% - 45%Equip 25% - 40% Average Energy end-user breakdown for EU office building

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Some audit cases had energy improvements only with a new lighting strategy control, for example the PCS-31 the reduction the light to 8 W/m2 it had have double effect on the energy consumption, first in direct electricity consumption and second in the reduction of internal loads, ie peak cooling power. At the end, with global strategy control for the AC system, the global system achieves 43% of energy reduction. Of course it is not only the lighting effect but all control strategy. Good control and management of the system in same cases can reaches a high save energy. This was happen in the ACS-12 case study when the total save energy it was up to 70%. This is an excellent example but the average control management has less energy efficiency indeed. The use of free potential energy (free-cooling) is used in some cases with excellent results in same cases the energy profits can achieve from 30% to 60% reduction of the total energy consumption. This solution is well dependent fro the weather conditions and the countries with cool climates are more suitable for this kind of solution.

Equipment Replacement There are a significant number of examples, in AdiBAC, based in replacement cool equipment, ie change the old chiller by a new one with high efficiency. The CS shows some examples were the energy saves can be up to 35% of total energy (ACS-2)4, and other when the energy saves reach 56% of the energy used for the cooling system (FRCS-1)3. It is quite possible to make an idea how energy we can save if we make chiller equipment replacement, in average point of view. Based upon the EER evolution in the last ten years, that means ± 30% increase efficiency on average (EECCAC), therefore it is possible to forecast the potential energy save for the next days in the AC systems. The "cases" in the data base are real installations which are described under the format that the various existing reference frames request in order to make them comparable. For part of the existing case studies it will be necessary to supplement information available by complementary measurements and / or by calculations so that all the methods become applicable. Besides their use in further work packages, the case studies in the data base will allow for the first time to estimate on a statistical basis the magnitude of the gains possible on European A/C installations.

1 AuditAC Case Studies Brochure: Case studies: Portuguese, n3 2 Auditac Case Studies Brochure: Case studies : Austrian, nº 1and nº2 3 Auditac Case Studies Brochure: Case Studies: French , nº1

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DETAILED INFORMATION FOR AC CASE STUDIES

Austrian Case Study 1 ACS1 City Archive

Georg Benke Austrian Energy Agency – Austria Date: December 2006

There’s no pertinent information about the cooling system

Introduction The new city archive was built in 2003/2004 and started to “operate” in March 2004. As all buildings owned by the city of Salzburg, the energy consumption was measured online by an energy monitoring system (EMS), measuring the energy and water consumption in 15 minutes intervals. In the first months (until End of July) it was thought, that the high energy consumption was due to the present situation, the building was new and the materials were just brought in, causing the constant opening of the doors. In the last week of July 2004 the installers of the ventilation systems were order to optimize the system. It was possible to reduce the energy consumption by about 40 %. During August and September two teams (one for the regulation system and one for the cooling system) tried to optimize the system but only achieved the expected result, a 60 % reduction at the beginning of November. The year 2005 brought the evidence that it was possible to reduce the consumption by more than 70 %. Building Description The Building was built in the year 2003-2004 to be the official Archive for all the information, documents and papers of the City of Salzburg. It is situated in the north – west of the Kapuzinerberg hill and is usually in the shadow of this small hill. (See map and also pictures below). About 20 people work in the building. The building is heated by the district heating system. The working places are situated in front of the four floors high storage area

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Design Details The regulation system of the company controls 9 different storage areas and provides this information to the air climate cabin. If the air is outside a certain range (f.e. 18°C / 50 % Humidity) the air climate cabin or the heating system starts to operated. It was acknowledged that the range for the air was too small. When the room temperature was too high, the climate cabin started to cool the room. As a result the room became too cold and the heating system had to start heating the room. The system was continuously cycling between on and off mode

Building Energy Performance The energy consumption (electricity) for the whole building:

2004 2005 kWh kWh

January - 7.282 February - 5.125 March 13.270 4.110 April 17.805 4.009 May 20.129 4.233 June 18.014 4.684 July 23.522 4.723 August 13.360 4.859 September 10.008 3.161 October 10.342 4.773 November 10.008 3.197 December 5.871 -

142.329 50.156

0

5

10

15

20

25

Janu

ary

Februa

ry

March

April

MayJu

ne July

Augus

t

Septem

ber

Octobe

r

Novembe

r

Decembe

rEne

rgy

Com

sum

ptio

n (K

Wh)

20042005

Cooling and Ventilation Performance There is a Central Ventilation system – situated on the roof which brings the air to the nine Climate storage areas, each have a different temperature (between 14-21°C). The heating / cooling is done decentralise for each area, which have also 9 heat exchangers. The humidity should be 50% (45% - 55%). There is no CO2 sensor in the storage area. Summary It was not so easy to solve the problem previously described because in the beginning the companies did not try to solve the problem together. Each company tried to find a solution on his own. When they start to cooperate, they realized that the range for the quality of the air was too small. The range was made larger an the energy consumption could be reduced by 70 %.

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Austrian Case Study 2 ACS2 Hospital

Georg Benke Austrian Energy Agency – Austria Date: December 2006

The refrigeration plant is equipped with a 6-cilynder 2-stage compressor. The heat rejected can be collected and used for heating water.

Introduction This case study is aimed at optimizing the operation of the refrigerating equipment present in the General Hospital of Linz, a general hospital with 1000 beds, serving 188,968 inhabitants. There are 6 Piston compressor engine (Kolbenkompressormaschinen) in two station (three per station) from the year 1985 and 1987, Refrigerant R22) which were on their cooling limit (2500 KW). It was made a forecast for the year 2008, and as a result of this study the cooling needs would reach the 3600 kW. A decision was made in order to replace all 6 engines with 6 Screw compressors (Schraubenkompressoren), which have up to 40 % more cooling capacity and need less energy.

Building Data

General Hospital Linz / Upper-Austria

Space Activity 1000 beds 45.000 ambulant patients (year) 28.000 operations per year

Nr. of employees 2000

Design Details Initial Situation There are 6 Piston compressor engine (Kolbenkompressormaschinen) in two station (three per station) from the year 1985 and 1987, Refrigerant R22) which were on their cooling limit (2500 KW). The system was designed in the way, that the waste heat of the compressor could be used to heat hot water or the Reheating register of the ventilation system. But in the situation, when the highest amount of heat was available, nobody need it. During summer, when the temperature outside was higher than 30 °C, the inlet temperature was 48°C and the outlet temperature was 54°C in this case the COP was less than 2,5. Implemented Situation

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The 6 piston compressors were replaced by 6 Screw compressors (Schraubenkompressoren), which have up to 40 % more cooling capacity and need less energy. Control Strategy There were also smaller changes within the control system of the cooling centre. There was no change in the kind of cooling consumption all over the hospital. Date of the new screw compressor:

Type: 30HXC190-PH3 Cooling capacity: 622 kW Electricity consumption: 130 kW Evaporator capacity: 622 kW COP: 4, 78 Performance levels: 6 Minimum level: 21 % Refrigerant: R134a

Within the control systems of the cooling centre the following changes are possible: An own program make a calculation about the energy consumption (Cooling, heating) within the next 24 h. Based on these results, it is possible the change the cooling demand in time. If the outside temperature is less than 18°C and the enthalpie about 45 kJ, it is possible to raise the Cooler outlet temperature to 7 or 8 °C. (Otherwise it is 6°C). This goes hand in hand with the weather forecast. To optimize the efficiency of the cooling engine, they try to operate always with 100 % or 50% per engine. Cooling Performance Characteristic data from the screw compressor

Performace level

Condensor inlet temperature

Cooling Capacity

Electric Capacity COP

% °C kW KW 100 31°C 622 130 4,78 86 31°C 532 123 4,33 71 31°C 436 109 4,00 50 31°C 316 67 4,72 36 31°C 218 54 4,04 21 31°C 155 47 3,30

To optimize the production of cool on a hot summer day, an extra Heat exchanger unit was fixed on the roof. With this heat exchange unit it is possible to reduce the inlet temperature from 48°C to 38 – 40°C. During winter they will use free cooling, when the outside temperature is less than 8°C. The heat exchanger on the roof should be enough the offer a cooling demand of 150 to 200 kW (reduction). Summary The first part of the renovation was done in May 2003. Concerning to calculation it was expected that the electricity consumption will be reduced by about 20 to 30 %. The maximum power load will be reduced by about 180 kW and the energy saving is up to 500.000 kWh. First result showed that there is a saving even between 30 to 35% - in this happened in the hot summer 2002.

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Belgium Case Study 1 BCS1 Office Building

Corinne ROGIEST-LEJEUNE Philippe ANDRE University of Liège - Belgium Date: December 2006

Heating – three gas boilers with variable flow to feed radiators and AHU’s. Cooling – two chillers with reciprocating compressors and air condensers with variable flow to feed AHU’s and fan-coils.

Introduction The building is located in the center of the town of Namur where it must be integrated in the city landscape. The building has been defined in modules in order to take into account the slope of the street. The commissioning and the management of the HVAC system have been monitored by the University of Liège. Building description Project Data Location: Namur (Belguim). Altitude: 90 m Year of construction: 1997/1999 Costs in €: 52 500 000 Number of working spaces: 884 Degree days: (15/15) 2240 Kd Heated floor area: 31440m2

Heated space: 105000 m3 Inst. heating capacity: 3150 kW Inst. cooling capacity: 1825 kW

Brief description of the type of building in study: Big size (68000 m² with 32000 m² offices) office building. Modular architecture: 11 blocs. Most of the useful area of the building consists in offices.

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Figure 2: sketch of the building at design stage

Description of the building layout: Two big (300 meters long) rectangular buildings (South wing and North wing) connected together by an atrium except for the central bloc that is the entrance hall. 3 levels under ground (parking and road tunnel). 3 levels in the North wing and 5 levels in the South wing, for offices. The atrium has no level and is covered by glass.

Figure 3: lateral facades of the building

Figure 4 : building section

Design Concept Building Envelope Detailed description of the building envelope: Per office: South: 0.08 m² heavy opaque concrete structure 3.02 m² triple glazing 0.76 m² wooden frame North: 7.35 m² heavy opaque concrete structure 5.21 m² double glazing 1.30 m² wooden frame Atrium North and South: 4.87 m² heavy opaque concrete structure 1.76 m² insulating metallic panel 5.78 m² double glazing 1.45 m² wooden frame Physical properties of the walls, slabs and roofs layers: external North wall (ventilated): natural stone +insulation (polystyrene)

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+ reinforced concrete U=0.47 W/m²K office floor: heavy reinforced concrete +light concrete +linoleum U= 1.07 W/m²K office ceiling: linoleum +light concrete +heavy reinforced concrete U= 1.07 W/m²K internal wall: plaster +acoustic insulation (rock wool)+plaster U= 0.35 W/m²K corridor ceiling: paving (gres)+light concrete+reinforced concrete U= 1.89 W/m²K corridor floor: reinforced concrete +light concrete +paving (gres) U = 1.89 W/m²K atrium wall: natural stone (pierre bleue)+ air+reinforced concrete U= 1.80 W/m²K external wall South: crepi +insulation (polystyrene)+reinforced concrete U= 0.43 W/m²K simple glazing (to interior street): U=3.88 W/m²K double gazing (North):glazing + air +glazing U=2.81 W/m²K external wooden frame: U=2.86 W/m²K internal wooden frame: U=2.45 W/m²K atrium frame: U=2.86 W/m²K atrium glazing: glazing +air +glazing U=2.83 W/m²K Solar and Overheating Protection Passive technology: Atrium between the two buildings to increase solar gains during winter. In North façade, windows are large because of no noise from the road. In South façade, windows are smaller to limit solar gains and noise from the station. There is an external metallic structure to shade the top of each level in the South facade.

Figure 6: view of solar protections

Design Details Global description of HVAC system type: Central heating production by 3 natural gas boilers (operating in cascade) with hot water loop with variable flow (to feed radiator circuit and AHU). Central cooling production by 2 chillers (reciprocating compressors with air condensers) with cool water loop with variable flow (to feed AHU and fan-coils). Heating and cooling power is distributed through huge collectors feeding the substations. There are 5 groups (substation) for each set of two architectural modules. Substations feed terminal units in offices, meeting rooms and atrium. The terminal units are VAV boxes (cooling and ventilation), fan-coils (heating and cooling in the meeting rooms) or radiators (only in the offices). Thermostatic valves or VAV terminals provide local control. Terminal units

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In the offices:

Figure 7: view of the terminal units

About 1 500 terminal units with VAV (Variable air volume) installed in the ceiling of all offices. These ventilation boxes are used for both air renewal and cooling. The temperature set point is selected by the occupants. Radiators with thermostatic valves installed in each office. The supply water temperature in to the radiators is regulated by a three-way valve in function of the ambient temperature In the atrium: Terminal units with CAV In the meeting rooms: Some rooms (meeting rooms) are provided with fan-coils which supply air, pre-heated at 20°C. Air handling units There are 5 AHUs (substation) for each set of two architectural modules (example G-H): - “S1” for offices in South wing - “S2” for the atrium, South side - “N1” for offices in North wing - “N2” for atrium, North side - “N3” for meeting rooms (located between the 2 modules in the North side).

Figure 8: organization of the AHUs distribution

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For group S1 and N1, the AHU feeds the offices with fresh air at fixed air volume (4300 m³/h) and re-circulated air with variable air flow (8600 to 18900 m³/h). For group S2 and N2, a fixed (constant air volume) part of the air extracted from the offices (3400 m³/h) is injected in the atrium after cooling and-or heating in the AHU. Difference between fresh air and air injected in the atrium air is extracted through the corridors to the sanitary by extraction fans.

M.E.T. Namur Ventilation Rue Intérieure Bloc

CdeEtatDis.

p

CdeEtatDis.

t

t p

CdeEtatDis.

CdeCdeEtatDis.

p p t h

p

t h

P

Atrium

Offices

CAV

VAV

Fresh

Air

Figure 9: detailed view of a typical Air Handling Unit

GS1 is constituted from: GS2 is constituted from: Register Register Filter Filter Heating coil (68 kW) Heating coil (16 kW) Cooling coil (123 kW) Cooling coil (22 kW) Humidification battery Fan with constant flow (3400 m³/h) Fan with variable flow (8600 - 18900 m³/h) GN1 is constituted from: GN2 is constituted from: Register Register Filter Filter Heating coil (54 kW) Heating coil (18 kW) Cooling coil (83 kW) Cooling coil (23 kW) Humidification battery Fan with constant flow (3400 m³/h) Fan with variable flow (8600 - 18900 m³/h) GN3 is constituted from: Register Filter Heating coil (17 kW) Fan with constant flow (1600 m³/h) Cooling plant The cooling plant is composed of two chillers, which have nominal capacity of 869.5kW and 956.5kW respectively. Each chiller is composed of: 3 or 4 screw compressors 1 water heated evaporator 2 air-cooled condensers 2 electronic expansion valves (one per condenser) 3 or 4 oil separators (one per compressor)

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3 or 4 oil cooler (one per compressor) 3 or 4 filters (one per compressor)

Both chillers use two independent refrigerant circuits, which are connected to the same evaporator

Figure 11: scheme of the chiller circuits

Figure 12: distribution of cold water

Chiller 1 is located in the west side of the building and chiller 2 at the opposite in the East side of the building. Chiller 1 has 4 twin screws, direct drive compressors, 2 for each refrigerant circuit; chiller 2 has 3 screw compressors, 2 for the first circuit and one for the other. The cold water circuit is divided in “primary” and “secondary” water networks.

Control Strategy Global control Electricity and HVAC are controlled separately. Supervision software is used to

- adapt the hourly settings - manage automatic cut off of electrical circuits - visualize process control - manage the alarms - record electrical consumptions

The management of HVAC system is based on one central unit and several control stations. central unit: - supervision of all of the HVAC system in DCC - collection information from collect units, analyze - optimize HVAC performance to reduce energetic costs - facilitate maintenance control station: - function modules The control system is different for heating and for cooling and, for both cases, shows a hierarchical nature, starting from the control of the rooms, then considering control of the secondary units (HVAC) and ending with control of the primary plants (boilers and chillers). Specific control systems: Boilers: - set point temperature in relation with external temperature - cascade operation activated by temperature sensor on in and out water

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Chillers: Chillers are designed to operate simultaneously. There is a control on the water temperature at the inlet and outlet of the evaporator. The 6 distribution pumps (3 for each chiller) operate in cascade to maintain pressure in the cool water distribution network. Air handling units for the offices: - constant fresh air flow - constant pressure in diffuser supply pipe - air temperature controlled by three-way valves from cool and hot battery, in accordance to office temperature - heating coil: - power control by water-in temperature control - cooling coil: - power control by water flow control - humidity (in winter): humidity sensor in supply and return duct with high limit. Description of offices temperature control law:

TmpExt

PcmTmpRep(virtuel)

TmpRep

TmpExt

TmpPul

CompEté

DAT controller

++

CompHiver

PcmTmpPul

CompTmpRep

Y(Valve controlSignal)

PccTmpRep

RT controller

++

CompTmpPul PccTmpPul

Figure 13: block-diagram of the supply temperature control strategy

Air handling units for the atrium: - air temperature controlled in accordance to exterior temperature - heating coil: power regulation by water flow control - cooling coil: power regulation by water flow control Regulation in winter: - chiller off - local hot water regulation in terminal units (radiator) by 3-ways valves - in- air temperature regulation function of out air temperature Regulation in summer: - in-air temperature regulation function of out air temperature Temperatures and humidity set points: In cool period: 21°C and 50% In hot period: 24°C and 60 %. Cooling and/or heating are activated from 9 AM to 5 PM, 5 days a week, the whole year.

Performance data The data analysis leads to the following comments: - The design of the components is quite good but the installation and the tuning, at the start of the project, were not optimal. - Selection, localization and validation of the measurement have not been studied enough during design, installation and commissioning phases.

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- The choice of the parameters and administration rules are not strict enough. - The energy management system of this building has good performances but the information from the sensors is not always right and the control laws not adapted. - This BEMS is very complex so it is underemployed. It is often the case in that type of building. - Fans are too noisy. - Chiller COP is reduced due to bad ventilation of the condensers. - There is a bad tuning of the VAV boxes thermostats. - The air distribution system is undersized. Building Energy performance Electricity consumption estimated: peak of electrical power: lighting 260 kW "small" power (.distributed in all zones) 170kW "main" power (lifts, escalators, kitchen, computers,..) 680 kW HVAC (chillers, fans, pumps) 840 kW Total 1950 kW Electricity consumption estimated related to use: lighting 3000 h/year 780 Mwh "small" power 1500h/year 255 Mwh "main" power 1000h/year 680 Mwh HVAC 1 (chillers) 500h/year 310Mwh HVAC 2 (fans, pumps) 1500 h/year 330Mwh Total 2410 Mwh Cooling performance The cooling performances of the building are not fulfilled. The temperature is too high or/and the fan noise too important. The AHUs fan electric power at nominal flow rate is given as follows: CAV AHUs: 55.7kW VAV AHUs: 122.4 kW Total AHUs: 178.1KW Cooling power distribution: fan-coils: 173 kW CAV AHUs cooling foils: 269 kW VAV AHUs cooling foils: 1474 kW Total cooling power: 1916 kW Chillers consumption given by the manufacturer: 100% load 618 kW 75% load 423 kW 50 % load 250 kW 25 % load 130 kW Heating performance The heating performances, in term of comfort, for this building are good.

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Ventilation performance To maintain the right pressure upstream the fan boxes, fans must be operated at the maximum power. So they are too noisy. A solution could be to improve the air distribution (decrease pressure drop and air leakage). A high upstream pressure is necessary to operate the flow air regulation system. Another solution is to change this control system. Construction and operating costs Operating costs: one person employed full time to maintain HVAC system Consumptions: Natural gas: 10327 Gj Electricity: 2431Mwh price electricity: 250000 €/an gas price: 87000 €/an Summary and retrofit opportunities Summary: A lot of studies were carried out on this building to improve the comfort conditions, mainly in summer. After commissioning, most of the errors were eliminated but some problems continue to exist. List of retrofit opportunities: Retrofit opportunities proposed by WP4 and applicable to this case study, ability to realize and to simulate are as follows easy to realize easy to simulate Envelope and loads: Solar gains reduction / daylight control improvement E 1.1 Tinted or reflective coated film XXXXX XXXXX E 1.2 E 1.3 XXXXX XXXXX Envelope insulation improvement E 3.5 Insulation of the parking ceiling XXXXX XXXXX Other actions aimed to load reduction E 4.7 E 4.8 X X Plant Cooling equipment / free cooling

Lighting management system

Interior shading

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P 2.5 P 2.6 X XXXX P 2.13 Ice storage system XX XXXX Air handling / heat recovery / air distribution P 3.8 Fresh air-to-exhaust air heat pump X XXX P 3.12 air duct sealing XX X Operation & Maintenance General HVAC system O 2.2 O 2.3 Reduced unoccupied ventilation XXXXX XXX O 2.6 O 2.2 O 2.3 Optimize Start/Stop XX XX O 2.7 O 2.5 Control chilled water temperature XXXXX XXXX Cooling equipment O 3.1 Optimize start / stop XX XX O 3.4 Control chilled temperature XXXXX XXXX Fluid (air and water) handling and distribution O 4.1 Control chilled water temperature XXXXX XXXX O 4.2 O 4.7 XXX XXXX O 4.9 Reduce unoccupied ventilation XXXXX XXX O 4.15 Air duct insulation XX XXX O 4.6 O 4.11 XX X O 4.8 O 4.9 Improve design and balance X XX O 4.17 of air duct system O 4.10 O 4.19 Improve design and balance XX XXX O 4.22 of chilled water duct system Modeling of some retrofit opportunities A number of those retrofit opportunities were evaluated by a building simulation: 1. Heating and cooling demand (base case) with ideal control 2. Heating and cooling demand with free cooling 3. Heating and cooling supply with realistic control law 4. No thermal isolation of the air pipe distribution 5. Air leakage in the air pipe distribution 6. Modification of the offices occupancy: 7. Reflective glazing 8. Change of the supply temperature control law

cooling tower

Free cooling

Air duct sealing

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5.89E+09 5.90E+096.24E+09 6.24E+09 6.29E+09

2.78E+09

5.47E+09

6.35E+09

1.30E+091.07E+09

1.26E+09 1.24E+091.44E+09

3.69E+08

7.64E+081.07E+09

0.00E+00

1.00E+09

2.00E+09

3.00E+09

4.00E+09

5.00E+09

6.00E+09

7.00E+09

demande, consignechaud, f roid

demande, consignechaud, f roid avec

f ree-cooling

BASE loi MET Air pipe t hermal nonisulat ion

Air leakage of f ices var iableoccupancy

Ref lect ive glazing ot her regulat ion law

Heat ing power

cooling power

Figure 14: comparison of heating and cooling performances (annual demand)

References Belgian "Case study" The QG-MET building (Namur), Design analysis: Synthesis report, October 1994, Jean Lebrun, Pierre Nusgens, Stefan Stanescu, Philippe André QG-MET building in Namur: simulation-based analysis of energy management strategy and commissioning, Philippe André, Patrick Lacote, Jean Lebrun, Andrei Ternoveanu avil 1999 Première analyse du système de gestion énergétique du bâtiment QG-Met à Namur, Philippe André, Jean-Pascal Bourdouxhe, février 1998 CA-MET: Energy-Efficiency. Measures List. Christophe Adam-Ulg. 4M Brussels-27/10/2005. Etude de cas CA-MET, Poursuite et finalisation des travaux Jean Lebrun, Christian Cuevas, Nestor Fonseca, Philippe André, Christophe Adam, Patrice Lacôte, Novembre 2002 Re-commissionning of a VAV air-distribution system. Philippe andré, Cleide Aparecida Silva, Nestor Fonseca, Jean Lebrun, Jules Hannay, Patrick Lacôte Commissionning-orientated building loads calculations. application to the CA-MET building in Namur. Christophe Adam, Philippe André, Cleide Aprarecida Silva, Jules Hannay, Jean Lebrun Gestion optimale de la climatisation d'un immeuble de bureaux; Jean Lebrun, Philippe André, Patrick Lacôte

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Belgium Case Study 2 BCS2 Office Building

Cleide Aparecida Silva Jules Hannay Jean Lebrun University of Liège - Belgium Date: December 2006

The installed HVAC system is composed by 4-pipe terminal units, AHU’s, Chiller, boiler, cooling towers and circulation pumps.

Introduction Brief description of the type of building in study: This is a medium size office building (28 000 m2) erected in centre of Brussels at end of the sixties. This building is constituted by open plan offices and (a few) meeting rooms. The whole building has an air conditioned system with the exception of the car park. Global description of HVAC system type: Old four pipe induction units in all offices and CAV/VAV systems in other zones. Classical heating and cooling plant, with fuel oil boilers and vapor compressions chillers with cooling towers. Renovation of the all HVAC system in way… Building Description Description of the building layout:

“H” horizontal shape, with, a total of 13 floors: -5 to –1 floors for parking, 0 for reception, mess and meeting rooms 1 to 7 for offices. The first level has a mezzanine. Fully glazed frontages with double glazing (without thermal break) at upper floors and single glazing at ground floor.

Occupants: 1 100 to 1 200 (rather constant) Costs in €: not yet known Consumptions: Fuel oil: 450 000 to 550 000 liters per year Electricity: not yet known

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Design Concept General Energy Concept Description of passive technologies present in the building: - External windows curtains - Curtains positions (open or closed) automatically controlled according to sunshine. - Most of the offices are open-plan (example shown in Figure 2) - The building works in all fresh air, with slight over-pressure. - The air extracted from offices is supplied to the parking. - No recirculation and no heat recovery.

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Figure 2 - Office view

Building Envelope Detailed description of the building envelope: “Curtain walls” with all glazing, from floor to ceiling. Physical properties of the walls, slabs and roofs layers: Almost no insulation. Poorly insulated cavities at periphery of each floor for induction units. U values of the envelope in W/m2K and envelope areas: Probably around 3 W/(m2.K) for double glazing; Envelope area still to be calculated. Solar and Overheating Protection Transparent glazings. Solar factor: Probably around 0.75 with curtain open and near to zero with curtain closed. Design Details Terminal units About 1 000 induction units, installed in the floors of all offices (Figure 3): 4 pipes with heating and cooling coils in “V“position and double thermostatic valves (one for two units). Nothing to prevent the air of passing across the coil which is not used. Occasional condensation on cooling coils. (depends on air primary…) Poor air diffusion: to high air speed induced near the floor and too short jet bearing in cooling regime. One big CAV AHU unit is used to supply a total of about 100 000 m3/h of primary air to all induction units. Other zones are supplied by a set of about 20 CAV and VAV AHU’s.

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Figure 3 - Induction unit views (internal view, location an thermostatic valve)

Air handling units The big “primary” AHU counts wit the following components: Dampers, filters, preheating, adiabatic humidifier, cooling, post heating, and two fans in parallel (Figure 4). Both fans are equipped with frequency drivers (in order to protect the motors of the fans and to reduce the instantaneous electrical peak of the system). All what is downstream of the humidifier has been renovated recently. All other AHU’s are also working in full fresh air, except for two, supplying the mezzanine and first floor.

Figure 4 - Schematic of the primary air handling unit

Cooling plant There are two machines mounted in series (but the circuits can be changed) with water cooled condensers. Each condenser has its cooling tower (renovated in early nineties). Each cooling tower (Figure 5) is equipped with a two speed axial fan. The slide valve of the screw chiller (Figure 6) needs enough pressure to work. The control strategy is the following, according to return water temperature: Up to 24 °C: water spray Up to 27 °C: an in low speed

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Up to 29°C: fan in high speed. The nominal water temperatures at condensers supplies are 32 and 34 °C. Each chiller has its own condenser pump, but no evaporator pump (the chiller water is circulated by the distribution pump). The chilled water temperature regime is 6 -12 °C in nominal conditions. The set point is supposed to move bit accruing to outside conditions. After renovation of the induction units, it’s expected to get the possibility of rising that temperature. NB: the (very old) circulation pumps are still at constant speed, with bypass. They might be, soon or later, replaced by variable speed…

Figure 5 - The two cooling towers

Figure 6 - The screw chiller

Control Strategy The building is equipped with a classical BEMS with two levels: a set of local control units and a PC for supervisory management (Figure 7). This system is relatively “open”: control strategies can be modified without the help of a specialist. But the data storage capacity is limited: one day to one week, according to the amount of measuring points registered. These records are only available as printed tables or diagrams. The data file cannot be transferred to anther computer. The comfort must be satisfied from 7AM to 8:30PM, five days per week. The BEMS is imposing an earlier re-start, according to weather conditions. In order to get comfort on a winter Monday morning, the system may have to be re-started Sunday evening. There are also some special requirements for the (prestigious) ground floor: the air conditioning is required there all along the year in order to protect the (exotic wood) decoration! Indoor air temperatures are measured at three different locations of each floor (except for floors 5 and 6). The average of all these temperatures is used by the BEMS in order to fix the primary air temperature. The set point is passing from 14 to 25°C, when the indoor temperature is moving from 25 to 21°C. But there is degradation if the indoor environment is too cold in the morning: the air is then supplied 25°C. The primary air is only supplied during pre-heating and occupancy time.

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Outside that time, if the weather is very cold, the induction units are still used in free convection mode, by supplying hot water to the heating coils.

Figure 7 - Examples of data visualization on BEMS computer

Retrofit Opportunities Some retrofits were already made on the plant and on the AHU’s: An attempt of free chilling was done sometime ago, by adding a water-to-water heat exchanger between the condenser and the evaporator circuits (in parallel to the chillers). For reasons still to be investigated, this experience failed and the system was dismantled. The AHU’s were partially renovated and the replacement of all induction units and thermostatic valves is now projected. This is urgent because of water leakage and of a lot of problems encountered with the thermostatic valves. The replacement of existing induction units by more efficient devices (other induction units or fan coils), if fitting in the small space available, should make possible to run the system with higher chilled water temperature and therefore better COP. The environmental control should also be made more accurate. More indoor temperature sensors will be installed in the occupancy zone. But much other retrofit potential should be considered: - Variable rotation speed for pumps and fans - Optimal control of chilled water temperature - Energy recovery loops between supply and exhaust air circuits - Air recirculation - Optimal control of cooling towers - Free chilling (again!) - Chiller condensers heat recovery - Use of chillers in heat pump mode (when no more used for cooling) - Etc.

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Belgium Case Study 3 BCS3 Laboratory

Cleide Aparecida Silva Jules Hannay Jean Lebrun University of Liège - Belgium Date: December 2006

HVAC system is composed by Terminal Units such as Fan coils and a AHU that supplies conditioned fresh air using textiles diffusers. The AHU and the Fan coil units are fed by water loops. The hot water is produced by a boiler and the cold water by chillers.

Introduction The audit of the HVAC system consists in analyzing the information available about actual energy performances and in identifying the most attractive retrofit opportunities. The case study presented here concerns a laboratory building erected in 2003 in the region of Liège (latitude 50.35°N and longitude 5.34°E, altitude 240 m). Building description Design concept The building is located at an open site, surrounded by a forest... The Liège climate can be characterized by the following data: Heating sizing temperature: - 12° Cooling sizing temperature and relative humidity: 30 °C and 50 % 15/15 heating degree-days: 2000 K*d. The building considered is of small size: around 4000 m² of air-conditioned floor area and 1900 m² of technical space distributed on three levels. It contents a set of offices, meeting rooms, dining hall and laboratories distributed on “ground” and “second” floors. Below the “ground” floor, there is an open parking area. The first floor corresponds to a technical space. The building envelope is made of glazing (100% for the offices and 77% for the laboratories) and of weatherboarding for the other walls (Figure 1). The floor area distribution is: 27% for the offices, 32% for the technical room and 21% for the laboratories.

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Occupancy and comfort requirements At working time, there should be 120 occupants in the building. The occupation period is 8:00 to 17:00 h., 5 days per week, all the year for the offices. The building has 95 and 5% of daily and night occupations respectively. The laboratories work 24h/24h, except one week per year for maintenance at the end of year. Ventilation strategy The laboratories are supplied all the time with “all fresh air”. For the offices there is some re-circulation and the system works according to the occupation period. By adding the contributions of all AHU’s in use inside the building, the total fresh airflow rate can be estimated at 40 000 m³/h. The ventilation system is equipped with heat recovery coils, interconnected by a glycol-water circulation loop. Heat transfer coefficients and nominal heat losses The heat transmission coefficients of the building enveloppe are presented in Table 1.

The thermal capacity flow rate of the ventilation corresponds to 13.4 kW/K, with a heat recovery potential of 5.7 kW/K. This means that the net ventilation heating demand is 13.4 – 5.7 = 7.7 kW/K. The global heating demand can be estimated by adding transmission and ventilation terms; this gives about 13.7 kW/K. This order of magnitude is in fair agreement with the slope (14 kW/K) of the building heating “signature” as shown in Figure 2. In this building, humidification is only provided by an eletrical humidifier. Therefore, latent heating is not included in the building signature, but represented as a separate curve (square points) in Figure 2. The building nominal power installed is equal to 600 kW. In nominal heating conditions ( -12°C, 90% / 23°C, 50% ) and for an air flow rate of 23000 m³/h, the humidification would require a power of 147 kW. The transmission and ventilation losses (with heat recovery taken into account) would be of 235 and 277 kW, respectively.

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HVAC system Terminal units Fan-coils (Figure 3) with (non-humidified) fresh air injection are used in all office and meeting rooms; they are working from 7 to 22 h.

Fully conditioned fresh (22°C, 50%) air is supplied to the laboratories through textiles diffusers (Figure 4). Industrial fan-coils are used to heat the technical room (Figure 5).

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Figure 5 : Heating network of the technical room

Air handling units AHU unit are used to supply a total of about 40000 m3/h of conditioned air (23000 m³/h humidified and 17000 m³/h non-humidified). Each AHU counts with the following components: Filters, heat recovery loop, cooling coil, heating coil , steam humidifier (for the two AHU of 11500 m³/h air flow rate) and fans (Figures 6 and 7). Fans are equiped with frequency drivers. All these AHU’s are working with full fresh air.

Figure 6 : Laboratory AHU

Figure 7 : AHU 4 supplying meeting and office rooms (through the fan-coils)

Flow rates, pressure drops and corresponding pumps powers of the different water distribution loops are given in Table 3.

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Table 3 – Water distribution loops.

Heating and cooling plants The hot water distribution and production subsystems are shown in Figure 8 and 9, respectively.

Two condensing boilers of 300 kW are used for hot water production. The chilled water is produced by an air-cooled chiller of 400 kW (Figure 10).

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Control strategy The building is equipped with a “building management system” (BEMS). All the information recorded by the BEMS can be read on the screen, but an (expensive) intervention of the BEMS manufacturer would be necessary in order to make the data files available for off line analysis. The ventilation of the laboratories is working continuously (day and night), from Sunday 22h to Friday 22h. The fan-coils are also used during working days, but only from 7 to 22h (with a “pre-start” on Sunday, from 17 to 22h). A thermostat was recently added in each office. Data analysis Electricity and fuel consumptions As usually, records of electricity and fuel (natural gas) consumptions are only available on a monthly basis. The records made on gas consumption from December 2003 to October 2006 are plotted in Figure 11.

The records made on electricity consumptions are given in Figure 12.

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Monthly averages of day and night (and weekend) electrical powers are plotted from January 2005 to July 2006 in Figure 13.

On the whole year, the averages of day and night electrical powers are of 205.5 and 146.5 kW, respectively. Monthly averages of electrical powers are also plotted in Figure 14 as function of the outside air temperature (each points corresponds here to the ratio between the consumed electrical energy and the number of hours of the month considered). The linear regression identified with these few points available has a negative slope, which can be explained by the fact that (winter) steam humidification is much more consuming than (summer) cooling. This interpretation is confirmed by the estimations already made on the consumptions of the steam humidification and of other equipment as shown in Figure 14.

Figure 14 : Electricity consumptions; measured and estimated values

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More detailed records would be required to go further in this analysis: hourly records and/off separate records for HVAC and non-HVAC consumptions… Retrofit opportunities 1) The gas consumption is very high. Solutions: • Provide another mode of sanitary hot water production. • Improve the control strategy: adapt better the hot water distribution temperature to the actual space heating demand. 2) The temperature and humidity set points are very high (23°C/50%) in the laboratories. Solution: verify if the needs for humidification are justified. They might be correlated to the presence of inert particles in the air (due to the high air flow rate supplied and the utilization of the textile ducts for the air diffusion). 3) The AHU’s functioning in full fresh air mode are equipped with heat recovery exchangers that recover approximately 40% of sensible heat. Improvement: a recovery heat pump could be used with extracted air as cold source. The whole heating power required in nominal winter conditions (-12 °C) could be provided by the existing chiller used in heat pump mode. A possible arrangement is suggested in Figure 15: The chiller air-cooled condenser is supposed to be replaced by a water-cooled one. The hot water is circulated through both existing heating and cooling coils of each AHU. Two supplementary coils are also to be added in the extracted air duct, downstream of the existing heat recovery coil.

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French Case Study 1 FCS1 Office Building

J. Adnot, D.Bory, M.Dupont D.Marchio, Ph. Rivière Armines – Ecole des Mines de Paris Date: December 2006

The system installed was composed by centrifugal compressors groups functioning in stages. This system was oversized and used forbidden refrigerant according with the actual regulations.

Introduction The Lexmark group manufacture and commercialize toners and it is located in Orleans. This group has 570 employers. Once the electricity invoice was excessive, the company made an energetic audit and concluded that the air-conditioning system was inadequately managed (supplied power exceeds the demand). The cold produced is used for air-conditioning system in different spaces.

Building Description Project Data Location: Orleans, France Number of working spaces: 570 Costs in €: 274k€ (1.80MF)

Design Details Until 1996, the cold production was ensured by three centrifugal groups, functioning in large power stages. This situation generated unnecessary costs (variable cold production, supplied power exceeds the demand, contract problems - EDF). Moreover, the refrigerating fluids (R11 and R12) used in the centrifugal compressor groups did not fulfill the regulation on the CFC’s emissions. To reduce the wasted energy and to be in compliance with the requirements of security and environmental protection, the company decided to replace the cold groups installed. Building Energy Performance

- Annual electricity consumption: 13 GWh; - Annual gas consumption: 5 GWh; - Consumption before audit: 1 220 MWh/year (271 tep/ year) of electricity to the

cold groups.

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Proposed Solution In 1996, they invested in two modulated cold production machines that are adjusted, if necessary, in modulated power stages, and have a nominal capacity that corresponds to the total demand. One of the machines has five power stages and the other is equipped with eight.

Construction and Operating Costs - Assembling investment: 247 k€ (1.80 MF); - Payback: 6 years; - Profit: 15k€/year (100 kF/year) related to the decrease of the maintenance costs; - Non-financial profit: advantages relative to the EDF contract or any other

supplier; - Financial profit related to energy saving: 30k€/year (200 kF/year).

Energy Savings Consumption after audit: 540 MWh/year (120 tep/year) of electricity to supply the

cold groups; Direct profit: 680 MWh/year (151 tep/year) which corresponds to 56 % of energy

saving Environment: the refrigerating fluids used are less harmful.

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French Case Studied 2 FCS2 Office Building

J. Adnot, D.Bory, M.Dupont D.Marchio, Ph. Rivière Armines – Ecole des Mines de Paris Date: December 2006

Five conference rooms are climatized by an AHU and a group of cold water production. About thirty offices have AC based on 2-pipe fancoils and natural ventilation. The cold water that feeds the loop of the AHU and the fancoil is produced in a non-reversible alternative Chiller.

Overview This audit was preformed to an office building located in the Paris suburbs. Building Description General The building was built in 1973 and his envelope is maid of curtain-facades with external metal framework. The principal facades are oriented to southwest (SW) and the North-East (NE). The glazing is double, sliding and provided with interior blinds. The glazing from the SW façade has also external blinds. The building has one floor and a basement. Its overall clear surface (OCS) is 1140 m ². It is possible to divide the building into three types of spaces: circulation zones, conference offices and rooms. The first located in the basement are not air-conditioned. Occupation & Scheduling The normal occupation of the building includes 42 people. These occupants are present roughly from 8 a.m. to 6 p.m. five days a week. The conference rooms by definition are occupied punctually, in different and random activities during the week. HVAC System Design The five conference rooms have AC system with an air-handling unit (AHU) that is supplied by chiller. About thirty offices have AC based on fancoils and natural ventilation system. Chiller description This non-reversible refrigerating unit, reference CIAT RZ800-2, was installed on the roof in 1993. Its nominal refrigerating power is 197 kW, it operates with R22 as refrigerant and the condenser is air cooled (8 fans of 250 W).

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The refrigerating unit consists of two independent circuits coupled with the same evaporator. Each circuit has a piston compressor with six cylinders. It has four refrigerating power stages (33%, 50%, 83% and 100%). It operates 24 h/24 and 7days/7, it has no kind of device in order to automatically stop its operation. Hydraulic network description The distribution fluid is a glycol-water solution. The network only requires one pump (doubled for safety). The cooling power transferred to the air by the batteries is attuned by adjusting the water flow thanks to 3-ways valves. The regulation of the water temperature in the network, 7 °C/12 °C, is carried out on the return temperature. AHU and network distribution The AHU, CIAT Climat 75, which supplies the five conference rooms, goes back to 1993. Including a mixing box and supplying a constant air volume, a fan (nominal electric power of 2.5 kW) supplies treated air while a second fan (nominal electric power of 1.5 kW) deals with the extraction of the exhaust air. Part of the exhaust air is mixed with the new air in order to limit the amount of heating. The amount of new fresh airflow is adjustable by a dumper on the external airflow. Besides the treatments, the mix of new and exhaust air is filtered before being supplied again into the conference rooms. The filters used in two successive lines are VOKES AIR Interpleat 40. The pre-filter is provided with a differential pressure gauge to control pressure losses and its fouling level. The supply temperature is controlled thanks to a 3-ways valve adapting the cold water flow circulating in the coil. An electric coil provides heat to the air in winter. The supply grills are located on the ceiling and the extraction grilles on the floor (technical floor). It misses in this case a recovery filter in order to avoid the clogging of the extractor fan. The “free-cooling” is activated when the outside temperature (lower than the interior temperature) makes it possible to satisfy the needs without turning on the refrigerating unit. The AHU only operates during the week from 4 a.m. to 8 p.m., approximately 4160 h/year. Fan-coils Description The 34 (two pipes and two coils) CIAT Major fan coils supply to the offices heating during the winter and cooling during the summer. Each air-conditioned office has an automatic thermostat. A dead band of 2 °C between the temperature setpoints of summer and winter avoid the simultaneous cold and heat supply. The contactors allow the fancoils to stop whenever a window is open. The setpoint of summer comfort default value is fixed at 25 °C. At night, the setpoint of summer comfort is increased at 30 °C. The fan of the fancoils keeps operating day and night, at low speed. One fancoil is installed in an informatics room. The thermal loads, even reduced, are kept at night forcing the fan coils to supply cold and keeping on the chiller. It would be preferable to dissociate this supply from the offices, controlling them independently. Building Energy Performance Cold water production group The cooling power installed - 178W/m² (OCS) - is largely higher than the current practices which is approximately 100W/m² and of 125 W/m² (OCS) for offices buildings and for this type of installation.

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According to statistics drawn by Eurovent in 1998, the nominal EER of the chiller ought to be between 2.12 and 2.85. By closely analysing these statistics mainly the compressor type, it seems that the nominal EER ranges between 2.16 and 2.74 which in the current energy class varies from F to D. No energy counter is provided, we estimated an electric consumption from 40 to 70 kWh/m².yr. This ratio leads to an annual air-conditioning demand ranging between 45 and 80 MWh/yr. The refrigerating unit represents an electric consumption between 40 and 60% of the electric consumption, about 18 to 48 MWh/yr (720 to 1920 kgCO2/year), the rest is consumed by the fancoils, the distribution pumps and by the AHU. Cold water distribution pumps The pump flow should normally be near 37m3/h, value obtained according to the total “best efficiency point” (BEP) of the pump which accounts approximately for 80% of its maximum flow. AHU (Air Handling Unit) The batteries of the supply and return fans indicate nominal power of 3 kW and 1.5 kW respectively. Taking into account their operation 4160 h/yr, we can conclude that their yearly consumptions rise in approximately 18.7 MWh/yr (748 kgCO2/yr). Fancoils According to the cold needs for the offices, the fancoils power should logically lie between 30 W and 80 W respectively. The 34 fancoils operation 8760 h/yr is then responsible for a minimum of 8.9 MWh/yr (356 kgCO2/yr) and a maximum of 23.8 MWh/yr (952 kgCO2/yr). Improvement scenarios Two improvement scenarios are possible:

1. The first obvious scenario consists in keeping air-conditioning in summer and the heating with Joule effect in winter.

2. The second scenario would be to replace the refrigerating unit by a reversible heat pump (HP) of which the average seasonal COP could reasonably be estimated at 2,5.

Loads and building opportunities- possible Improvements on the building The building is in general well adapted to AC, particular regarding the solar protections. The office equipment, which releases too much heat (printers, photocopier) are located in specific rooms, non-occupied and non-acclimatized. The thermal intern loads can be reduced. In fact, almost all the computers are equipped with cathode-ray tube screens. If opportunity arise, it would be interesting to replace them by more effective flat-faced screens. These screens can consume/release up to 50% less energy/heat than the cathode-ray tube screens. By equipping the 42 occupants in the building with flat-faced screens (30 W instead of 60 W), the direct savings in electricity are approximately 3.3 MWh/yr (130 kgCO2/yr) over a one-year standard. These measures generate also indirect energy saving in AC, related to the reduction of the thermal loads. Over approximately six months, the thermal loads are reduced 1.64 MWh/yr. By considering that the chiller compensates for these loads with a seasonal

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EER of 2.5, this improvement represents approximately 0.66 MWh/yr (26 kgCO2/year) whatever the selected scenario. This investment generates in the other hand a surplus of heating. By considering the six heating months, the thermal loads are also reduced 1.64 MWh/yr. In 1st scenario, these loads are treated by Joule effect and directly represent a surplus of electric consumption of 1.64 MWh/year (66 kgCO2/year). This scenario generates overall indirect losses of approximately 1 MWh/year (40 kgCO2/year). In 2nd scenario, these loads are treated by a reversible heat pump whose average seasonal COP is 2.5. The surplus of heating consumption finally cancels the indirect profits generated by AC. HVAC Performance- Opportunities on the GPEG, AHU and pumps The weakness lies mainly in the management of the operation periods. The refrigerating unit maintains the setpoint temperature during 24 h/24 and 7 days/7 all year. With few expenses, a substantial energy saving is possible by programming operating ranges:

- In 1st scenario, it is possible to establish a time schedule from 6 a.m. to 6 p.m. in week and all the weekends are possible. Moreover, as it is surely little requested from November at March, it is advised to completely shut down the cooling system for this period in order to avoid possible cycling.

- In the scenario the 2, even if the setpoints can be reduced the night and the weekend, the heat pump will have to operate for these periods to maintain a temperature acceptable in the building in winter. The heating corresponds indeed more to a "need" that with a "comfort" like air-conditioning. The schedule can however be maintained in period of air-conditioning.

The annual dates of stop and starting could be adjusted progressively empirically. The potential of energy saving of these new schedules should be quantified more precisely at the time of a more detailed audit. Another defect is an oversizing factor of approximately 80 % that led the refrigerating unit to run most of the time with partial load and thus with reduced effectiveness. The energy losses thus generated represent at least of 10 % of consumption of a refrigerating unit of identical output which would be correctly sized. The annual potential energy savings due to resizing the chiller (with identical EER) range between 1,8 to 4,8 MWh/year (72 to 192 kgCO2/year). At the time of the renovation, it is strongly advised to carry out a detailed assessment of the thermal loads of the building to optimize the system size. Then one would also rather a system of higher energy class (B even A following the Eurovent classes). The setpoint temperatures of the chilled water can be increased, best implementing an outdoor temperature dependent law, for example a temperature of return to 12 °C in summer and 14 °C in intermediate season. The potential of energy saving on the refrigerating unit is considered at 3 %/°C gained with the increased evaporator outlet temperature. This new regulation law would generate over the air-conditioning season a range of 1,1 to 2,9 MWh/year (43 to 115 kgCO2/year) of energy saving. Possible improvements on the distribution pumps Energy saving are also possible by reducing the operating time of the pump to the occupation periods:

- In scenario 1, to program the pump in week of 6 h with 6 p.m. and April at October only as the refrigerating unit would reduce its annual operating time to

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1800 h/year and would bring approximately 24,4 MWh/year (975 kgCO2/year) of energy saving.

- In scenario 2, the pump must be maintained under operation from November to March to heat the building, that means 3700 h/year more. These 5500 h/year of operation would make it possible to obtain approximately 11,4 MWh/year (455 kgCO2/year) of energy saving.

The pump, while operating less long, would then require less maintenance and its longevity would be also increased. Possible improvements on the air handling unit We distinguish between two operating modes following the period from the year: air-conditioning/ventilation from May to October and heating from November to April. In the first mode, the AHU only operates in week from 8 a.m. to 6 p.m., globally 1300 h/year. In the second scenario, we will consider that it is necessary to anticipate one hour the heating to restore comfort before the arrival of the occupants, that is to say 1430 h/year of operation. The annual total operating time is established then with 2730 h/year and saving energy amounts to 6,4 MWh/year (257 kgCO2/year). The new exhaust air and air ducts being coupled, it is possible and feasible to install an economizer with heat and cooling recovery from the extracted air. In winter, the potential is large and could be quantified more precisely in more detailed audit. Possible improvements on the fancoils Large energy saving are possible by reducing the periods of operation of the fancoils. They will have nevertheless to be maintained under operation in winter to maintain the temperature of the building. To fix lower setpoints during the night and the weekend is however possible. It is possible to limit their operation of 8 a.m. to 6 p.m. in week from April at October, the thermal loads evacuating itself naturally during inoccupation periods. This schedule reduces the operation time of the fancoils to 5200 h/year and avoided consumption ranges between 3,6 and 9,7 MWh/year (145 to 387 kgCO2/year). O&M opportunities The oversized air conditioning unit operated in short cycles even in full summer. This pour operation seems to be the direct result of the oversizing of the refrigerating unit. However, one should not dismiss the assumption of a lack of refrigerant. Indeed, the second circuit, when off, seemed undercharged according to the aberrant pressures recorded measured with the pressure gauges at low and high pressures. This state lets think that the contractual maintenance checks are not always carried out. From a general point of view, the refrigerating unit is in bad condition. Its plates of protection were removed, leaving the bodies exposed to the bad weather. The condenser fouling level is high. Pump distribution of the chilled water On the roof, the heat insulation of the hydraulic network is in bad condition at many places. In the building, no stain shows to the existence of leakages. The pump operates correctly and without particular noise. Air handling unit Except the display of the differential pressure of the primary filter and the exit and inlet temperatures of water in the coil, no other measurement device is installed on the equipment. Maintenance must thus be limited to the statement of the electric outputs

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absorbed by the fans, to the cleaning or the change of the filters as soon as the pressure losses reach a certain threshold and the control of the parameters of operation. Its effective application is unknown for us but the air-handling unit is in a good state of maintenance. The fouling level of the filters is normal and the fans are in good conditions, their respective belts are not damaged and no abnormal noise was detected. The environment of the unit allows to intervene without problems and is kept clean. Fancoils The temperatures of supplied air, obtained by requesting maximum power to the fancoil setting a severe setpoint temperature, are in agreement with the current values and the operation mode (7/12 °C) of the water loop. In addition, they are relatively homogeneous and thus do not allow to diagnose a hydraulic problem of balancing. Indeed, a huge lack of chilled water flow in a branch of the distribution would not respect of the comfort setpoint of in the concerned zone. The state of the fancoils gives confirmation of their age. They all are however in operating condition. Their consumption could be reduced by a regular calibration of the thermostats. If the procedure is too expensive, it is also possible to compensate consequently the specific setpoints where we observed difference. Evaluation of the efficiency of the pump Our measurements lead to a total efficiency of the pump of 49 %: we observed that the output is rather weak in comparison with those of the products of the market. It is indeed possible to reach a total efficiency of 67 % by choosing a more efficient pump. Appraisal of the AHU: evaluation of the specific efficiency of ventilation The specific effectiveness of Rv 4 ventilation is here 1,02 Wh/m3, the value is quite higher than the Switzerland recommendations, American and English on the matter. However, improvements can be made by replacing the fan groups by more effective ones. Summary conclusions

4 s u o e x t ra cv

v

P PRQ+

=

Psup (W) et Pextrac (W) electric powers of supply air fan and extract air fan and Qv (m3/h) total air flow in the circuit.

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Italy Case Study 1 ICSI Cultural Department

Dipartimento di Energetica del Politecnico di Torino - Italy Date: December 2006

The HVAC system installed is composed by embedded floor radiant panels and AHU’s.

Introduction The Public building, object of this study is the headquarters of the cultural department of the City of Turin; it is situated in Via San Francesco. It is composed of 5 floors, which have been converted into offices. Originally it had a central heating system with traditional radiators, after restructuring in 1996, a more articulated system of HVAC was installed. The present document intends to analyze and to appraise the operation of the system highlighting possible interventions to improve the efficiency and to reduce the energy requirement.

The actual HVAC system is constituted by: primary air plant, embedded floor radiant panels fed with warm water in winter and cold in the summer.

The actual system doesn't often succeed in supporting the summer load and therefore it doesn't achieve the comfort temperature and humidity values required.

Building Description The building of the culture department is situated in the historic centre of Turin has five floors, building houses administration offices of the City Council and a library. The old building was renovated in 1996 when a new HVAC was installed, but over the years this system has been seen to be inefficient and not adequate for the building’s needs.

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Figure 2 - Plant (floor 2) of Public Building

The main goal of this audit is to identify, using a simulation software package, a HVAC system which can supply the comfort requirements and, at the same time reduce energy consumption. Furthermore, it will be necessary to highlight all the suggestions regarding plant design that could be useful for the development of Audit methods.

Design Details The HVAC system is formed by embedded floor radiant panels that cool the environment, without relative humidity control. The humidity is controlled by different AHU’s in the building, housed in the ceilings. In winter this system works well, in fact the air is heated and humidified by the AHU and the embedded floor radiant panels function correctly. In summer, however, the temperature of the water circulating in the panels cannot go under 18°C or there are problems of condensation and mildew and the single primary air plant cannot maintain the correct environmental conditions.

The whole system is set up to be able to use a BMS (Building Management Systems) but at present the BMS only supplies information regarding the temperature in each office. It is impossible to calculate the electricity consumption as there are no meters from which the data can be downloaded.

Figure 3 - Embedded floor radiant panels, typical layout in each office

Control Strategy The HVAC system works continuously when the indoor air set-point temperature is 26ºC in summer and the relative humidity is 50%. In each room there is a control unit for the temperature. Performance Data

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Energy demand Using a dynamic simulation software package, it was possible to obtain the consumption of a mixed air/water HVAC where the embedded floor radiant panels are substituted by fan coils maintaining the AHU. The following figure show the data result from software package simulation :

Figure 4 – simulation consumption

1 BTU = 2, 93 x10-4 kWh = 1,055 kJ

Ventilation and air distribution The distribution of air produced by the various AHU, located on each floor of building, passes through rectangular or circular channels with run in the corridors. Diffusion in each single office passes through rectangular grilles located in the office, the passage of air is guaranteed by the grilles in the doors into the corridors where it is recovered by the system. In summer, the distribution of air in areas distant from the AHU’s is not enough to guarantee maintenance of optimal temperature and air control conditions, in fact the people that work inside these offices experience some problems.

Proposed Solutions

a) Change the embedded floor radiant panels to fan-coils. The new HVAC system can still be defined as air/water system but, it will be composed of AHU’s for ventilation, and cold – hot water distribution for the fan-coils.

b) Use a suitable BMS, the system is already predisposed with a specific control

console and suitable software.

c) Strengthen the fan of the various AHU’s because the existing fans are insufficient to force air to the offices distant from the AHU

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d) Intensify the maintenance of the fittings that is currently performed by an external

firm and the inspection of the components by the administration.

e) Use electricity meters to download electric consumption on an hourly and daily

basis, in order to collect further information for an effective audit of the building. For instance, the cooling system, lighting, central heating and pumps.

f) Change the burner that is currently installed (heating oil) to a methane model and

connect the system to the gas distribution network. Energy Analysis

Figure 5 - Total annual gas consumption 1 BTU = 2, 93 x10-4 kWh = 1,055 kJ As show above in Figure 5, with new HAVC system will be possible to save about 400.000 BTU Final Analysis The proposed solution present certain advantages compared with the existing system:

- Maintain the correct environmental conditions of temperature and humidity - The system will take further electric consumption information for use in future

audit - New HVAC system will allow to obtain a energy saving - BMS will allow a more efficient maintenance.

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Italy Case Study 2 ICS2 Hospital

Marco Masoero, Chiara Silvi, Salvatore Balducci Politecnico di Totino - Italy Date: December 2006

The HVAC system installed is composed by embedded floor radiant panels and AHU’s.

General Description of Case Study This case study is aimed at optimizing the operation of the refrigerating equipment present in the S. Andrea Hospital of Vercelli, a general hospital with 300 beds, serving a 178,000 inhabitants province in the eastern part of Piemonte (NW Italy), halfway between Milano and Torino. The hospital was built in the early 1960’s and, originally, was not equipped with a comprehensive centralised AC system. Distributed AC systems (including, chiller, AHU and air / water networks) have subsequently been installed in selected areas. The study was carried out in cooperation with the ESCO which manages the AC system, in conjunction with planned renovation work foreseeing the installation of new chillers and the construction of a chilled water loop connecting the existing refrigeration units. Potential energy and cost savings for various options were examined, including: replacement of existing chillers, different strategies of chiller operation, free cooling, and recovery of condensation heat for SHW production. Building Description

General Building Data:

Location Vercelli Altitude above sea level 130 m Configuration Concrete framed with masonry walls.

Layout Several separated buildings hosting the various hospital departments.

Number of floors Variable Floor area (Gross) --

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Design concept and details In the initial configuration, fifteen refrigeration units (identified as ECn = Existing Chiller n) were present in the hospital. The planned renovation work includes the installation of two new, identical refrigeration units (identified as NCn = New Chiller n), and the construction of a chilled water loop. The refrigerating power output of each of the new units (963 kW) is about equal to the sum of the outputs of existing chillers EC1, EC2 and EC3 (955 kW).

Unit no. Manufacturer and model Compressor

electric power Refrigerating power

Water flow rate

Pump Electric power

Nominal COP

kW kW m3/h kW EC1 Clivet VDAT-2/2.166 183 355 63 3.5 1.94

EC2 Clivet VDAT-2/2.166 183 355 63 3.5 1.94

EC3 RC Unico LNO 260.S2.G8 83 245 45 3 2.95

EC4 Climaveneta BE/SRAD/LN 2402 315 884 150 7,5 2,81

EC5 ---- 125 250 45 3 2.00

EC6 Airwell AIR CV A 18P 21 50 10 1.1 2.38

EC7 York Y CAC 45 15.5 35 7 0.75 2.26

EC8 Robur ACF 60 7 17.2 3 0.5 2.46

EC9 Robur ACF 60 7 17.2 3 0.5 2.46

EC10 MTA TA.E.251 25 60 12 1.5 2.40

EC11 ---- 125 250 42 3 2.00

EC12 Emicom RAE 361OU 9.8 35 6 0.75 3.57

EC13 MTA C6057 CA 23 55 10 1.1 2.39

EC14 ---- 125 250 42 3 2.00

EC15 Breda 40 80 15 1.5 2.00

EC16 ---- 120 295 52 3.5 2.46

NC1 CLIVET WSAT-23450 396 963 170 10 2,43

NC2 CLIVET WSAT-23450 396 963 170 10 2,43

Floor area (Treated) -- Year of construction: 1961 Refurbishment HVAC Variable (depends on department)

Refurbishment Lighting Variable (depends on department)

Refurbishment Other 2002-2004 Central boiler room and main electrical supply

Space Activity General hospital (300 beds) Occupiers Business Type National Health Care Service Type of tenancy Owner occupied Tenancy Since 1961 Heating System Gas fired wet radiators Ventilation System Mechanical Ventilation Cooling System Passive Chilled Ceilings Types of fuel used: Heating Gas Cooling Electricity DHW Gas HDD 2571 (conventional value)

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The position of the existing chillers EC1, EC2 and EC3, of the new chillers NC1 and NC2, and of the chilled water loop is shown in the following figure.

Control Strategy General The existing and new chillers adopt different control strategies: two regulation steps for the existing chillers, and nine regulation steps for new chillers. Performance Data The following chiller COP data were used in the energy analysis:

Regulation steps Regulation steps EC1 1 2

NC1 1 2 3 4 5 6 7 8 9

COP 2.70 1.94 COP 2.55 2.43 3.11 2.85 2.68 2.55 2.50 2.46 2.43 Cooling Performance General Lacking experimental data on cooling performance, the analysis was performed by simulation only, using the following approach. Weather data: hourly data (temperature and relative humidity) for the average day of the warmest months (April – September) measured at Milano-Linate airport, were used. Cooling load vs climate: the Humidex index, H, was used as the single-value climate descriptor5; hourly values of H were calculated for the six months. It was assumed that cooling demand is a linear function of H, the peak cooling demand (equal to the chillers rated output) occurring for the maximum hourly value of H (H = 32.2°C at 16 hrs in August), and cooling demand becoming zero for H = 15°C. The cooling load fraction for each hour of the six months were then determined. Chiller performance: hourly COP values were calculated as a function of load fraction, using the performance data of section 5.

5 Masterton J.M., Richardson F.A. (1979) Humidex, a method of quantifying human discomfort due to excessive heat

and humidity, CLI 1-79. Environment Canada, Atmospheric Environment Service, Donsview, Ontario.

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The following retrofit / system management options were analysed

1. Replacing chillers EC1, EC2, EC3 with new chiller NC1 2. Using both NC1 and NC2 at partial load 3. Increasing the air-conditioned area 4. Modifying the outdoor temperature at which chillers are shut off and free cooling

is performed 5. Recovering condensation heat for SHW

Detailed Replacing chillers EC1, EC2, EC3 with new chiller NC1 New chiller NC1 has a rated refrigeration power output which is virtually equal to the total power output of EC1 + EC2 + EC3. The analysis assessed the expected savings yielded by the replacement of the existing chillers with the new one. Expected seasonal electricity consumption reduction are on the order of 15730 kWh, yielding savings on the order of 1420 €/yr (i.e., 4% of present costs).

Using both NC1 and NC2 at partial load As an alternative option, both NC1 and NC2 operating at partial load could replace the existing chillers. This strategy should achieve a higher overall chiller efficiency, while increasing the pumping energy (two pumps instead of one). Compared to the above option (NC1 only), further savings on the order of 1460 €/yr could be achieved

EC1+EC2+EC3 NC1 NC2+NC3 Chiller electrical consumption (kWh/yr) 391830 376100 339200

Pumps electrical consumption (kWh/yr) 21000 21000 41400

Total electrical consumption (kWh/yr) 412830 397100 380600 Total electricity costs (€/yr) 33250 31830 30370

Increasing the air-conditioned area As a future option, the substitution of other existing groups with NC2 has been evaluated. Calculation was based on a peak load of 355 kW and an average COP for the replaced chillers. Expected seasonal savings are on the order of 1790 €/yr (i.e., 4% of present costs).

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Modifying the outdoor temperature at which chillers are shut off and free cooling is performed Savings associated to a one degree variation in the limit temperature at which the chillers are shut off and free cooling is adopted (23°C vs 22°C) are approximately equal to 50000 kWh/yr (with negligible differences between existing and new chillers), i.e. on the order of 12%. Recovering condenser heat for SHW As a base option, the new chillers are not equipped with condenser heat recovery system. The benefits associated with a partial recovery of condenser heat6 have been evaluated. By analysing the chiller’s thermodynamic cycle, the recovered heat was evaluated; it was further assumed that heat recovery is limited to the warmest period (six hours per day in July and August). Cost analysis is based on Net Present Value (NPV) calculation.

SHW production with condenser heat recovery

Recovered condensation power 191,25 kW

SHW temperature range (mains – delivery) 15 – 40 °C

SHW demand per person 140 L/person-day Daily SHW energy demand per person 4.07 kWh/person-day Daily recovered heat of condensation 1147.5 kWh/day

SHW volume produced with recovery 39474 L/day

Number of people served 282

SHW production with natural gas boiler Boiler efficiency 0.85

Daily natural gas consumption 140.7 m3/day

Daily cost 58,22 € Costs analysis Seasonal savings (July and August) 3610 €

Extra cost of the chiller 4500 €

Cost of the storage tanks 10500 €

Payback time 5.2 yrs

6 The chiller’s condenser is subdivided into two sections: the water-cooled high-temperature section transfers the heat

corresponding to the de-superheating phase of the process to the water, while the low-temperature air-cooled section rejects the heat of condensation to outdoor air.

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Summary conclusions and suggested ECOs This case study illustrates a situation which is very common in the hospital sector in Italy, and that can be summarized as:

• The building structures are relatively old, dating from the pre-energy crisis period (1960s).

• Originally, the hospital was not equipped with a comprehensive centralised HVAC system.

• In different successive phases, local AC systems (typically including chiller, AHU, air/water distribution networks) have been added to selected parts of the complex.

• Margins for energy efficiency are very limited, due to the “rigid” structure of the decentralised AC system.

• System maintenance is cumbersome: several refrigeration units of different size, manufacturer, and year of construction area present.

• Actual data on electricity consumption of chillers, pumps and fans are lacking, since overall electrical consumption only is measured for billing purposes.

The ESCO managing the AC system is now involved in a renovation plan, aimed at rationalising the chilled water production. The study has identified the following different ECOs that may lead to significant energy savings, with acceptable recovery times for the investment:

• Construction of a chilled water loop to which all the chillers in the hospital complex are connected.

• Replacement of three of the existing chillers (EC1, EC2 and EC3) with the new chiller NC1, whose rated refrigeration power, is equivalent to the total power of the three older units.

• As an alternative to the previous ECO, use of both new chillers NC1 and NC2 at partial load as substitute of EC1, EC2 and EC3.

• Modification of the outdoor temperature at which chillers are shut off and free cooling is performed.

• Recovery of condensation heat from the new chillers NC1 and NC2 for Service Hot Water production.

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Italy Case Study 3 ICS3 Surgery / Nursing Department

Marco Masoero, Chiara Silvi, Fabrizio Cagliero Politecnico di Totino - Italy Date: December 2006

100% external air AHU. This unit has humidifier, fans, HEPA filters, cooling coil and heating coil.

General Description of Case Study This case study illustrates the energy auditing of the AC system serving a three-storey building within the hospital of Oderzo, a town situated in the north-eastern Italian province of Treviso, 60 km NE of Venice. The study was carried out in cooperation with the ESCO responsible of managing the energy systems of the hospital. The building and AC system under investigation is currently undergoing a complete renovation. So far, the first floor hosting the Surgery and Nursing department has been completed (building refurbishment and a totally new AC system) and is now into its second year of utilisation; work on the basement and second floor are still ongoing. The energy analysis has been focused on optimising the operation of the Air Handling Unit (AHU) of the Surgery department. To do so, the main operational parameters of the AHU were monitored in the April-October 2006 period; recorded data were acquired with ad-hoc instrumentation, installed by the ESCO for the purpose of this energy diagnosis. Building Description

General Building Data:

Location Oderzo (Treviso)

Altitude above sea level 13 m

Configuration Concrete framed

Layout

Basement: Service areas (to be completed) First floor: Surgery and Nursing (completed) Second floor: Cafeteria, Chapel, Office space (to be completed). HVAC eqpt room (4 AHU’s – 2 already installed), electrical eqpt

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Number of floors Three

Floor area (Treated) 350 sq. m. (first floor)

Year of construction: Unknown

Refurbishment HVAC 2004

Refurbishment Lighting 2004

Space Activity (first floor)

Surgery: operating rooms (2), recovery room, sterilizer eqpt., service areas, corridor. Nursing: labour (4), delivery, recovery, newborn nursery, service areas, corridor.

Occupiers Business Type National Health Care Service

Type of tenancy Owner occupied

Heating System Radiators (in service areas)

HVAC System All air with HEPA filters (first floor)

Cooling System Air-cooled, vapour-compression water chiller

Types of fuel used: Heating Gas

Cooling Electrical

DHW Gas

HDD 2358 (conventional value) HVAC System Design General Information: The AC system of the building is all-air (100% external), as prescribed by Italian regulations for hospitals. When the renovation work will be complete, four AHU’s will be installed at the second floor: the two already existing AHU’s serve the Surgery and Nursing areas, while the two future AHU’s will respectively serve the basement and the second floor. Terminal units with HEPA filters are present in critical areas of the first floor. The Surgery and Nursing AHU’s are virtually identical, and include the following sections:

• Outdoor air intake with pre-filter • Intermediate-fluid heat recovery deck • Pre-heating deck • Cooling deck • Steam humidifier • High efficiency filter • Supply fan • Extract fan

Three post-treatment sections with re-heating and re-cooling decks are provided for individual control of space conditions in operating room no. 1, operating room no. 2, and recovery area. Chilled water is produced with an air-cooled, vapour compression water chiller installed on the roof of the building. The central boiler room of the hospital produces hot water for space heating and SHW with two hot water boilers; steam for air humidification is produced with an indirect steam generator coupled to a low-pressure, diathermic fluid steam boiler, which also covers other steam users of the hospital.

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Detailed Information:

Heating System Hot water boilers Two Gas-fired boilers Steam boiler Unknown Air Conditioning (Surgery) All-air with HEPA filters on room terminals Supply air flow rate (100% external) 9700 m3/h Extract air flow rate 8800 m3/h Supply fan electric power 11 kW Extraction fan electric power 4 kW Air Conditioning (Surgery / Nursing) All-air with HEPA filters on room terminals Supply air flow rate (100% external) 9760 m3/h Extract air flow rate 8800 m3/h Supply fan electric power 11 kW Extraction fan electric power 4 kW Air Conditioning (Basement) All-air Supply air flow rate (100% external) 3000 m3/h Extract air flow rate 2700 m3/h Supply fan electric power 1.5 kW Extraction fan electric power 1.1 kW Air Conditioning (Basement) All-air Supply air flow rate (100% external) 6000 m3/h Extract air flow rate 5700 m3/h Supply fan electric power 4 kW Extraction fan electric power 2.2 kW Water chiller Roof mounted Manufacturer Trane (air-cooled condenser) Refrigeration power Unknown Electrical power input 90 kW Compressors Unknown Refrigerant fluid R22

HVAC Control Strategy General The existing and new chillers adopt different control strategies: two regulation steps for the existing chillers, and nine regulation steps for new chillers.

Detailed data:

HVAC Plant Control: Continuous operation (24 hrs/day) for contamination control

Set Points (operating rooms) Adjustable in the 18-24 °C +/- 1°C range

Run times of HVAC plant Continuous

Identify HVAC zoning of building Each space of the Surgery / Nursing areas has individual temperature control

Details of planned maintenance Contract maintenance as per normal standards and documentation available on request.

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BOILER ROOM

Low-pressure steam boiler and indirect steam generator

Hot water boilers

HVAC SYSTEM

AHU – Surgery

Intermediate-fluid heat recovery deck

WATER CHILLER

Air-cooled water chiller serving the Surgery and Nursing AHUs

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AC Performance Monitoring methodology A detailed monitoring campaign of the Surgery AHU was conducted in the April – October 2006 period. The following 16 temperatures were measured and recorded at 15’ intervals:

• Outdoor air / Heat recovery inlet, air supply side (B11); • Return air / Heat recovery inlet, air discharge side (B12); • Heat recovery outlet, air supply side (B13); • Pre-cooling air outlet (B14); • Heat recovery outlet, air discharge side (B21); • Post-heating / Post-cooling air outlet operating room n° 1 (B22); • Post-heating / Post-cooling air outlet recovery room (B23); • Post-heating / Post-cooling air outlet operating room n° 2 (B24); • Pre-heating deck water supply (B31); • Pre-heating deck water return (B32); • Pre-cooling deck water supply (B33); • Pre-cooling deck water return (B34); • Heat recovery deck water supply (B41); • Heat recovery deck water return (B42); • Post-heating deck water supply operating room n° 1 (B43); • Post-heating deck water return operating room n° 1 (B44).

Four data acquisition modules were employed, each connected to four temperature sensors. Data were recorded at 15 min. intervals and periodically downloaded to a laptop PC. Electricity consumption of the heat recovery loop circulation pump was also measured. Monitoring results A sample display of the temperature recording is given below. Numerical data were stored as .xls files for post-processing. Visual inspection of the temperature trends allowed to identify a few metrological problems, such as a systematic error in temperature readouts due to heat conduction in the hot deck water pipes: this seemed to indicate that hot water was flowing in the pre-heating deck even in cooling regime – obviously a meaningless circumstance. In reality, hot water was correctly by-passed by

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the three-way valve, but heat conduction in the hot water pipes affected the readout of sensors B31 and B32.

Heat recovery performance The average thermal effectiveness of the intermediate-fluid heat recovery system turned out to be on the order of 58% (based on measurements). For sake of comparison, an air-to-air heat exchanger (65% effectiveness), was also considered. A performance comparison for the period 23 June – 22 September 2006 (assuming that heat recovery is on when Tout – Tin > 2°C) yielded the following results:

Heat recovery type A B Δ (B–A) Recovered thermal energy (kWh) 2955 7819 4864 Chiller electrical energy savings (kWh) 1477 3910 2433 Heat recovery loop pump electrical consumption (kWh) 389 0 -389 Net electrical energy savings (kWh) 1088 3910 2822

A: Intermediate-fluid heat recovery B: Air-to-air heat recovery

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In terms of financial impact, this action lead to savings on the order of 300 € (500 € if air-to-air heat recovery had been adopted). Free cooling Free cooling by direct supply of outdoor air (without mechanical cooling) is assumed feasible when Tout < 20°C. Seasonal expected energy savings are summarised in the table below:

Free cooling YES NO Δ Δ(%) Cooling energy (kWh) 48075 57079 9004 16% Chiller electrical energy (kWh) 24037 28539 4502 16%

Suggested ECO's In addition to a more extensive use of heat recovery and free cooling, the following ECO’s have also been suggested:

Installation of screens to protect the air-cooled condensers of the water chiller from direct solar radiation

Partial or total recovery of condenser heat for air re-heating Exclusion of the re-heating deck of operating room N° 2 (which is used for urgencies

only), while maintaining the prescribed air change Automatic closure of operating room doors to avoid energy losses due to treated air

movement Summary conclusions This case study has allowed a quantification of the impact of AHU operation on the electrical energy consumption of an all-air AC system for the hospital. Attention has been focused on ventilation heat recovery and free cooling. Data were obtained through a monitoring campaign carried out in April-October 2006, which required the installation of ad-hoc instrumentation (temperature sensors, electricity meters, and data loggers). Such approach was necessary since the necessary quantities were neither metered for billing purposes, nor acquired by the existing BEMS. Metrological problems in obtaining reliable field data were identified and solved. This points out the need for detailed and tested data collection protocols that would be of help in a detailed energy audit.

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Italy Case Study 4 ICS4 Research Center

Marco Masoero, Chiara Silvi, Andrea Cantarella, Daniel Dominguez Michelangeli Dipartimento di Energetica del Politecnico di Torino - Italy Date: December 2006

The AC is an air-and-water system type (primary air and two-pope fan coils). Hot and chilled water is produced with a water-to-water reversible heat pump, using treated lake water that feeds the AHU and FCU’s.

General Description of Case Study The Brasimone research center was established in the early 1960s by CNEN (National Committee for Nuclear Energy) – later to become ENEA (Italian National Agency for New Technologies, Energy and the Environment) - on the eastern shore of an artificial water basin, serving a nearby ENEL (National Electric Utility) hydroelectric power station. The Centre is located in the Appennine mountain range, halfway between Bologna and Firenze, at 846 m above sea level. In the mid 1980s, a small building (1.800 m3) was constructed on the side of the basin opposite the research centre. This initiative was jointly promoted by ENEA and ENEL to promote communication to the public on the activities being conducted by the two organisms in the Energy field (building views are shown in Figure 1). In 2005, the HVAC system of the building has been completely renovated. This case study presents the results of the system monitoring campaign, carried out in its first summer of operation (May – September 2006) Building Description General Building Data:

Location Brasimone (Bologna), Italy

Altitude 846 m

Configuration Small concrete framed building. Rectangular floor plan. Tilted roof (17° tilt angle)

Layout Spaces open to the public at ground floor, offices at the upper floor

Number of floors Ground + one floor

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Floor area (Gross) 300 m2.

Floor area (Treated) 300 m2.

Occupancy 120 (when conference room is in use)

Year of construction: 1985

Refurbishment HVAC 2005

Refurbishment Lighting -- Refurbishment Other -- Space Activity Exhibition area, Conference room, Offices

Occupiers Business Type Research Institution (ENEA) + Electric Utility (ENEL)

Type of tenancy Owner occupied

Tenancy Since 1985

Heating System Electrical Heat Pump + Oil boiler as a backup

HVAC System Air and water (two-pipe fan coils)

Cooling System Electrical Heat Pump

DHW Heat Pump (condenser heat recovery in summer)

HDD 3610 Building Envelope:

Windows

Type Operable

Window Area 120 m2

% Area operable 100% of total

Type of glazing Clear triple

Window U-value 2.3 W/m2K

Internal shading devices Venetian blinds

Wall Structure Concrete, Cavity, Masonry

Wall Insulation Within Cavity (Polystyrene)

Wall U-value (average) 0.5 W/m2K

Wall area 215 m2

Roof Structure Wood structure

Roof Insulation Polystyrene

Roof Area 290 m2

Roof U-value 0.48 W/m2K

Ceiling Type Suspended (wood)

Ceiling Height 3-5 m

Design concept General Information: The AC system is of the air-and-water type (primary air and two-pipe fan coils). Hot and chilled water is produced with a water-to-water reversible heat pump, using treated lake water as the heat source / sink. A newly installed BEMS allows continuous monitoring of the main performance parameters of the system

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Detailed Information: Terminal units Eleven two-pipe fan coils units are installed in the conference room and exhibition area at the ground floor, and in the offices at the upper floor. Radiators, fed by a separate hot water circuit, are provided for the rest rooms. Air handling unit The AHU (Figure 2) has a nominal flow rate of 3200 m3/h (100% outdoor air with heat recovery) and consists of the following elements:

• Outdoor air intake with pre-filter • Air-to-air heat recovery unit • Pre-heating deck • Cooling deck • Steam humidifier • Re-heating deck • High efficiency filter • Variable flow supply fan (equipped with inverter) • Variable flow extract fan (equipped with inverter)

The AHU supplies fresh air to the conference room. Air is extracted partly from the conference room, partly from adjacent spaces.

Figure 2: Air Handling Unit

Heat pump The reversible water-to-water heat pump (Figure 3) delivers a maximum thermal power of 60 kW (cooling @ 7-12°C) and 68 kW (heating @ 40-45°C). Condensation heat recovery in cooling mode is performed with a dedicated condenser. A scheme of the hydraulic circuits connecting the heat pump to the AHU and fan coils (primary circuit) and to the lake water (secondary circuit) is shown in Figure 4. The heat exchanger of the primary circuit is of the shell-and-tube type, and is immersed in an inertial storage of 200 litres. The heat exchanger on the secondary circuit is of the brazed plate type; the heat recovery condenser is also of the brazed plate type. A water-glycol solution is used in the secondary circuit to avoid the risk of freezing. The existing oil boiler was maintained for emergency use.

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Figure 3: Heat pump

Figure 4: Hydraulic circuits

Air Handling Unit Supply air flow rate 3200 m3/h Extract air flow rate 2600 m3/h Humidifier (steam) flow rate 10 kg/h Water terminals Fan-coils (three independent circuits) Conference room, exhibition room, offices Radiators Rest rooms Heat Pump Manufacturer and model Tonon EPH 58-2 Cooling power 68 kW @ 7-12°C Heating power 60 kW @ 40-45°C Electrical power input 16.2 kW Compressor type and control Two hermetic scroll compressors Refrigerant fluid R407c Oil boiler 70 kW (existing)

Control Strategy The building is equipped with a BEMS operating at two hierarchical levels: a set of local control units manage the individual HVAC components (terminals, AHU, heat pump), while a central PC performs the supervisory management (Figure 5). The central PC is capable of transmitting information to one or more external clients, similarly to a standard Internet Web server, the only requirement on the client side being the presence of an Internet browser and a password to access the website. The collected data (e.g, air / water temperatures, electrical energy consumption, malfunctioning alarms, operator intervention requests, etc.) are saved and can be downloaded by remote computers.

Figure 5: Examples of data visualisation on BEMS computer

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The heat pump cooling / heating power output is regulated by on-off control of the two compressors: therefore two levels of power output are possible. The AHU is equipped with standard air temperature / humidity regulation. Room thermostats control fan-coil operation. Performance data The main results of the monitoring campaign carried out in the summer of 2006 are summarized in the following charts and graphs (all data were obtained from the system BEMS and remotely downloaded on a PC): • The monthly average COP (Fig. 6) was computed from the measured data of

delivered cooling energy and compressor electrical consumption; the seasonal average COP turned out to be 3.9. Similarly, the thermal energy input obtained from the lake water was measured (Fig. 7).

• A correlation analysis was performed to investigate the dependence of delivered cooling energy (AC system thermal load) on outdoor climate. The graphs of fig. 8 show the dependence of cooling energy on air temperature, specific humidity and enthalpy. The best correlation is obtained when air temperature is considered. This fact may be explained by considering that, during the period of investigation, the AHU fans were generally switched off (the conference room was mostly unoccupied): the AC cooling load was therefore primarily determined by solar and conduction gains, which are fairly well correlated with outdoor dry-bulb air temperature.

• Finally, the heat pump load factor was determined by analysing the compressors duty cycle. The capacity control is in fact on-off: therefore, the heat pump load factor can be determined by measuring the time fraction for each turned on compressor.

Figure 6 - Monthly average C.O.P. and outdoor temperature

Figure 7 -Compressor electrical consumption and thermal energy input from the low-temperature heat

source (lake water)

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Figure 8 - Delivered daily cooling energy per unit volume vs. specific humidity

Figure 9 - Delivered daily cooling energy per unit volume vs. enthalpy

Figure 10 - Delivered daily cooling energy per unit volume vs.

outdoor air temperature

Figure 11 - Cumulative frequency of heat pump utilization factor

Summary This case study was aimed at analysing the performance of a water-to-water reversible heat pump. The presence of a BEMS makes it possible to monitor and record the main system operational parameters: water temperatures and flow rates, electric energy consumption, outdoor air temperature and humidity, etc. Based on the above data, the daily performance of the heat pump was analysed in the April – September 2006 period. The seasonal average COP was equal to 3.9 and a good correlation between daily cooling energy and outdoor dry-bulb air temperature was identified. The statistical distribution of heat pump load factor was also considered, which turned out to be quite low, mainly because of the limited utilisation of the conference room in the investigated period. A similar monitoring campaign is planned for the 2006-2007 winter season, with the purpose of analysing the heat pump performance in the heating mode.

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Portuguese Case Study 1 PCS1 Informatics Center

André Borges, André Poças, José Luís Alexandre FEUP/INEGI – Instituto de Engenharia Mecânica e Gestão Industrial - Porto Date: December 2006

The system installed is not centralized. Each room has independent cooling units. The units existent are basically DX close control and single split units.

Introduction The new Campus of Faculdade de Engenharia da Universidade do Porto (FEUP) has different types of buildings and most of them don’t have an HVAC centralized system installed. Due to the specific application of some of these buildings it was necessary to study the cooling capacities according to the type of the building. In the majority of the cases the actual HVAC system is neither adjusted to the demand of the several spaces nor to the type of buildings. The present document intends to evaluate the performance of one of those systems installed in the Computer’s Center of the University – Centro de Informática do Prof. Correia Araújo (CICA) and also the assessment of performance of both the air distribution and the efficiency of the system. The internal gains in this building are the main cause of its high thermal load; as a result the installed HVAC system became insufficient. This building reaches often high indoor air temperatures in all spaces or in some strategic zones of the building. This overheating effect is more common in summer when the external loads are higher.

The original HVAC is a VRF system where the local cooling units are ceiling splits and close control units with an outdoor condenser unit.

Through an auditing done to the building, it was verified that the energy consumption of this building was very influenced by the type of informatics equipment present in the floor -1. Consequently, the consumption of energy referring to floor -1 is responsible for 85% of the total consumption.

The main consumer of the building is the informatics equipment installed, it accounts for about 54% of the total consumption.

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Figure 1 – View of (-1) CICA’s floor

Building Description

Project Data

Location Porto, Portugal Latitude 41,1 N

Longitude 8,6 W Altitude 73 m

Year of construction 1996/2001 Number of Working spaces 4

Degree days (20) 1437 Heated floor area 140 m2

Heated space 395 m3 Inst. heating capacity - kW Inst. cooling capacity 50 kW Report Prepared by: André Borges and José Luís Alexandre

The building CICA has three floors and the ground floor is the centre of informatics resources. The function of this building is mainly to ensure and make available all the informatics services for the FEUP community and to uphold its innovation and use.

The cooling power installed in these spaces is not enough to remove the total load that occurs inside the building, which causes a high indoor air temperature leading to harmful situations, causing damages and reducing the performance of the informatics hardware.

The main goal of this audit is to evaluate the correct cooling power, as function of the demand of the four zones showed on Figure 1. It is, also, necessary to verify the efficiency of air flow distribution inside the different spaces and the assessment of ventilation as it was proposed in earlier. The indoor air set point temperature will be object of concern in this studied case.

If this value can be increased (i.e. increase set point temperature) lower energy consumption will be achieved without reducing the total performance of all systems.

This building employs electric energy as a source of final energy. The following picture shows values for the energy consumption in the year of 2005, as well as for the specific consumption.

Table 1 - Energy consumption – 2005

Ano 2005 803 MWh Electric energy 233 tep

Specific consumption 197 kgep/m2

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Design Details The HVAC system installed in below grade floor of CICA building is an all refrigerant system, where, all units work with R22 refrigerant. In D-102 and D-104 rooms, there are ceiling splits with 5 kW of cooling power, connected to the condenser units installed in the building’s rooftop, Error! Reference source not found.. The rooms, D-101, D103 and D-104 are equipped with close control units; one unit in the first two places and two units in the last one, Error! Reference source not found., an individual condensing outdoor unit is also located in the building rooftop. The Close control units allow humidity control inside the spaces.

Figure 2 illustrates the functionality of the close control units installed in the different zones where reheated /re-cooling air is supply by grids under the floor.

Figure 3 - Schematic of the close control

Figure 4 - Schematic of the condensers existing in the building rooftop

Building envelope The table below shows the configuration of the building envelope.

External wall e [m] λ [W/mºK]] cp [J/kgºK] ρ [kg/m3] U [W/m2K] Gypsum 0.015 1.150 837.0 1950.0 Concrete 0.220 1.750 1080.0 2200.0

Polystyrene 0.040 0.035 1250.0 32.5 Gypsum 0.015 1.150 837.0 1950.0

0.683

Internal wall e [m] λ [W/mºK]] cp [J/kgºK] ρ [kg/m3] U [W/m2K] Gypsum 0.020 1.150 837.0 1950.0

Brick 0.150 1.750 1080.0 2200.0 Gypsum 0.020 1.150 837.0 1950.0

1.833

Internal floor e [m] λ [W/mºK]] cp [J/kgºK] ρ [kg/m3] U [W/m2K] Linoleum 0.003 0.169 1000.0 1000.0 Light Slab 0.450 0.931 965.0 1320.0

1.490

Figure 2 - Schematic of the ventilation

systems distribution

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Ceiling e [m] λ [W/mºK]] cp [J/kgºK] ρ [kg/m3] U [W/m2K] Plaster 0.050 0.220 1085.0 1680.0 2.517

External floor e [m] λ [W/mºK]] cp [J/kgºK] ρ [kg/m3] U [W/m2K] Linoleum 0.003 0.169 1000.0 1000.0 Concrete 0.200 1.750 1080.0 2200.0

Polystyrene 0.040 0.035 1250.0 32.5 0.692

False floor e [m] λ [W/mºK]] cp [J/kgºK] ρ [kg/m3] U [W/m2K] Linoleum 0.003 0.169 1000.0 1000.0

Agglomerated 0.030 0.056 1000.0 300.0 Aluminium 0.001 200.000 3430.0 2700.0

1.374

Table 2 – Building envelope constitution

Control Strategy The HVAC system works in continuous throughout the year where the indoor air set-point temperature is 25ºC and the relative humidity is 50%. Each close control unit performs the specified set-point of the air conditioning space.

Control strategy set-point schedule Close control 24ºC 24h

Split units 19ºC - 23ºC 9h - 18h Performance Data Cooling demand Using a dynamic simulation software package, it was possible to obtain the cooling loads for each space. Figure 5 shows the results of the simulation for cooling demand and the sensible cooling load of the installed systems.

0

5

10

15

20

25

D -101 D -102 D -103 D -104

kW

Installed capacity Sensivel load

Figure 5 – Sensible cooling load

As shown above in figure 6 the installed cooling powers inside the analyzed spaces are not enough to remove the thermal load, which justifies the overheating that sometimes occurs.

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Ventilation and air distribution As it was already referred, the treated air is supplied through the floor, and there aren’t any ducts to promote the air distribution. figure 6 shows an air outlet, which allows the treated air supply in to the zone. As shown, there are cables in the floor that difficult the air flow and do not allow a uniform air distribution. Thus, it was verified that the indoor air temperature in the different spaces are not homogeneous.

Figure 6 – Air supply through the floor

We can’t obtain correct distribution of air flow due to the incorrect placement of the Close Control units.

Observing figure 7 it is possible to conclude that the equipment placed in the opposite side of the Close Control units, can easily reach temperatures about 34/36 ºC.

Figure 7 – Temperature distribution in space and overheating effect Proposed Solution The energetic context was the main concern when selecting and incorporating the several HVAC equipments, promoting the optimization of energy consumptions and ensuring new energetic regulations.

The solution proposed is, in an energetic and environmental way, the most adjusted since it is a centralized system that has a high efficiency. This solution also allows the cooling power increase without major costs.

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The considered HVAC system can be defined as an air/water system. It will be composed by a cold-water central producer (chiller), located in the building covering, and by a cold water distribution net with two pipes, for supply and return. This circuit will supply the existing cooling coils in the independent Close Control units. These units are located inside climatized spaces or, if not possible, near them. An adequate ventilation system can also be installed to guarantee the indoor air quality. This system will also include the possibility of free-cooling the spaces, given adequate exterior air conditions.

The following equipments form the proposed system:

- Chiller with scroll compressor with 100 kW of cooling capacity; - Four Close Control units supplied with cold water which integrates system of

humidification and electric resistance for heating; - Ventilation, piping and control system…

Performance data These spaces are characterized by its high internal gains, as shown bellow

Zone UPS -101 FCCN -102 Servers -103 Networks-104

Equipment gains [kW] 6,4 4,6 20,7 13,57 Light gains [W] 108 144 288 288

Occupancy - - - -

Overall internal gains [kw//m2pav] 0,42 0,15 0,42 0.30

Table 3 – Internal gains

Energetic Analysis The energetic and power consumptions of the existing Close Control units in the 4 zones, was obtained through dynamic simulation, was 128 MWhe/year. It should be noted that this analyses considers the consumption of the compressor, the ventilation, the reheat coils and humidification.

Using once again the dynamic simulation, we could calculate the energy consumption for the proposed solution, 87 MWhe/year. The following figure shows the comparison between the solutions.

0

20

40

60

80

100

120

140

160

180

Electirc resistence Hot Water Electric resistence Hot Water Electric resistence

Actual system New system without free-cooling New system with free-cooling

Ener

gy [M

Wh]

yea

r

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

CO

2 em

issi

ons

[ton

/yea

r]

[MWh(electric)]year [MWh(termal)]year t CO2

Figure 8 – Comparison between the simulated systems

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The new system with free-cooling and electrical reheat is much more effective than the others, except the system which uses hot water for reheat. However this system would require a boiler, so the system would consequently become more complex and expensive.

0

20

40

60

80

100

120

Ele

ctric

anu

al c

onsu

mpt

ionl

[MW

h]

Actual system

Centralized system withoutfree-coolingCentralized system with free-cooling

Figure 9 – Comparison of cooling electric energy required in the three different simulated systems

Once again is shown that the system with free-cooling is the most effective for this case. As it is verified by the energy earnings, of the floor -1, with the substitution of the current system for the proposed one, we can achieve savings of around 41 MWh (Figure 8). This value correspond to 2.870,00 Euros a year of economic won (the price of the electric energy was esteemed to be 0,070 €/kWh). Construction and Operating Costs of New System According to the proposed HVAC system, the expected budget rounds 80 000 € and the operating costs will decrease in comparison to the current system.

We shouldn’t forget that the new proposed system will have the responsibility of climatizing the whole building, therefore we have to make an estimate of earnings for the whole building, and not only for the floor -1. Having this in mind a new estimate was obtained, a value of around 7.000,00 euros a year of economics earnings. With such earnings, it is possible to have a capital return of about 11 years (payback of 11 years), the lifetime of an HVAC installation of this type is a proximally 20 years, turning the investment a little more tangible. Final Analysis The proposed solution presents certain advantages when compared with the existing system:

a. The cooling capacity can be increased with the connection of one or more chillers. According to the type of equipment, it is possible to connect them and optimize its functioning. All these systems allow a centralized management and partial loads according to the thermal needs.

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b. The circulation fluid is water, which do not represent any restriction or danger as refrigerant fluids.

c. When necessary, the upgrade of the indoor power is simple and easy to implement.

d. The terminal units can be independent of the cold unit production, in terms of trademark, model or type, turning the equipment more versatile.

e. The lifetime of the proposed equipment is always higher then that of splits units. Suggested ECO’ s and O&M The study has identified the following different ECO’s that may lead to significant energy savings, with acceptable recovery times for the investment: ECO’S - ENVELOPE AND LOADS E1.1 Install window film or tinted glass E1.2 Install shutters, blinds, shades, screens or drapes E1.3 Operate shutters, blinds, shades, screens or drapes E1.4 Replace internal blinds with external systems ECO’S - VENTILATION / AIR MOVEMENT / AIR LEAKAGE IMPROVEMENT E2.1 Generate possibility to close/open windows and doors to match climate E2.3 Optimise air convective paths in shafts and stairwells (in the -1 floor) E2.6 Generate possibility of night time overventilation ECO’S - OTHER ACTIONS AIMED AT LOAD REDUCTION E4.5 Replace electrical equipment with Energy Star or low consumption types E4.6 Replace lighting equipment with low consumption types E4.7 Modify lighting switches according to daylight contribution to different areas E4.8 Introduce daylight / occupation sensors to operate lighting switches E4.9 Move equipments (copiers, printers, etc.) to non conditioned zones O&M - FACILITY MANAGEMENT O1.1 Generate instructions (“user guide”) targeted to the occupants O1.2 Hire or appoint an energy manager O&M - GENERAL HVAC SYSTEM O2.1 Use an energy accounting system to locate savings opportunities and to track and measure the success of energy – efficient strategies O2.4 Maintain proper system control set points O2.5 Adjust internal set point values to external climatic conditions O&M - COOLING EQUIPMENT O3.1 Shut chiller plant off when not required O3.17 Clean condenser tubes periodically O3.18 Repair or upgrade insulation on chiller

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Portuguese Case Study 2 PCS2 Informatics Center

André Borges, André Poças, José Luís Alexandre FEUP/INEGI – Instituto de Engenharia Mecânica e Gestão Industrial - Porto Date: December 2006

This air-to-air system is composed by roof-top units (one per room) and heat pumps to provide the heating and cooling energy. This unit mixes fresh air with return air. Given favorable conditions, the control strategy is prepared to allow free-cooling.

Introduction The new Campus of Faculdade de Engenharia da Universidade do Porto (FEUP) has different types of buildings and most of them don’t have an HVAC centralized system installed. In other hand due to the specific application of some of these buildings it was necessary to study the cooling capacities according to the type of the building. In the majority of the cases the actual HVAC system is neither adjusted to the demand of the several spaces nor to the type of buildings. The present document intends to evaluate the performance of one of those systems installed in the central Amphitheatres of the Block B of FEUP and also to evaluate the performance of both the air distribution and the efficiency of the system. The occupants' acoustic comfort can’t be obtained due to the high noise index verified in these spaces. In order to revaluate the HVAC facilities in the amphitheatres it was necessary to calculate which thermal loads affected each space, confirming, this way the values of the original project.

The original HVAC was composed by three rooftops, placed in the covering of the building, equipped with heat pumps that supplied each one of the amphitheatres.

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Building Description

Project Data

Location Porto, Portugal Latitude 41,1 N

Longitude 8,6 W Altitude 73 m

Year of construction 1996/2001 Number of Working spaces 34

Degree days (20) 1437 Heated floor area 456m^2

Heated space 1536 m^3 Inst. heating capacity 47.8 kW Inst. cooling capacity 49.4 kW

Illumination 30 W/m^2 Report Prepared by: Andre Borges and José Luís Alexandre

The amphitheatres are part of the block of classes of FEUP, their objective is to provide the maximum of comfort to their occupants, during classes and during lectures at a

European and national level, or even for the projection of films (Figure 10). The installed system compels a quite high level of acoustic and thermal discomfort, it conditions in a considerably way the occupants of this spaces causing an unpleasant work environment. For this reason, users choose to maintain the system turned off for most of the time. Due to the high index of discomfort verified in these spaces the main objective of this audit is to evaluate the correct system without acoustic problems and without forgetting the

thermal loads that affects each space. The Block B (block of classes) of FEUP is subdivided in 4 different areas:

B1 (two more buildings to East); B2 (two located buildings between B1 and B3); B3 (two more buildings to West); Central amphitheatres, which include three rooms with AVAC systems independent of the type air to air - Salas B001, B002 and B003.

The present study just seeks the new dimensioning of the AVAC system in the central amphitheatres (B001, B002 and B003).

Figure 10 – View of Amphitheaters

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Description of the system of HVAC In general, the climatization system that equips Block B central Amphitheatres can be characterized as a type air-to-air system. In the covering of the building there are three "rooftops" equipped with heat pumps that supply each one of the amphitheaters (Figure 11). The air treated by these units is insufflated in to the places throughout an assemblage of insufflation ducts (Error! Reference source not found.) and its respective diffusers. It also exists three Air Handling Units (AHU's) (Error! Reference source not found.), that allow the return, the extraction and the admission of fresh air.

Figure 12– View of AHU Figure 13 – View of insufflation ducts

Control Strategy AHU assures the balance between the fresh and the recirculation air in function of the occupation rate and the pressure of the space. The difference between the supply and return air flow is compensated with the admission of fresh air from the exterior. The mixture of fresh and return air is filtered in the respective section of the machine; in case of acceptable temperature difference between the interior and the exterior air, the system allows "free-cooling". The control HIM/IT of the room temperature is done by a thermostat located in the return ducts. The dampers of air are computer monitored, allowing their regulation in function of the occupation rate as well as through temperature probes locate in the

Figure 11 – View of Rooftops

Figure 14– View of Exterior damper

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interior, and in the exterior, allowing, when possible, the use of "free-cooling." An independent system of desmoking fans is integrated in the ventilation facilities. This type of equipment allows the extraction of high amounts of air promoting the elimination of smoke in case of fire. This creates a loss of pressure in the affected room so that smoke proliferation doesn't affect adjacent rooms. These devices, are usually, activated in an automatic way through smoke detectors, when fire is detected. Analysis of the system of AVAC

• Acoustic Analysis After acoustic measurements made at Block B central Amphitheaters, we verified that the HVAC facilities presented a noise level between NC50 and NC60 index. This values and according to ASHRAE norms, are two times higher than the acceptable index for this type of space (NC35). As a result of this analysis the following aspects could have contributed to the malfunction of the mechanical facilities of ventilation and air conditioned system (HVAC) causing this unusual readings:

♦ Air distribution inside the rooms - after a simple analyses of the flow speed, on main and subsidiary ducts, it was verified the existence of prohibitive values. In the case of the main duct, the speed of the air reaches values that vary within 6 to 5 m/s, when the advised maximum should be 4.6 to 3.6 m/s. In the take-offs, the air reaches the speed of 5.6 m/s, instead of the recommended maximum value of 3 m/s. Without even consider the type of construction of the ducts, the form and the fixation type and the supply grille, we can easily affirm that the noise proceeding from the installation is provoked by the flow of the air in the ducts and accessories.

♦ Distribution of the air in the exterior/ covering - the generic analysis of the

operation mode of the current HVAC installation confirms that:

The net plan of the external ducts wasn’t take in to consideration; The equipments that were used for this type of installation were inappropriate, mainly at the acoustic level; Rigid connections were used among the different passive elements (ducts) and active equipments (heat pums /"rooftop"); Lack of vibration isolators as a support of the active equipments in the rigid structure of the building; Lack of acoustic attenuators in the supply net and air extraction.

Figure 7–NC Curves

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Cooling

00.5

11.5

22.5

33.5

44.5

55.5

100% 75%

50%

30%

MW

h

B002 B003 B001

Heating

0369

121518212427

100% 75%

50%

30%

MW

h

B002 B003 B001

• Energetic analysis

MWh/year B001 B002 B003 100% 5.06 9.75 4.42 11.21 5.03 9.75 75% 2.71 12.41 2.17 14.35 2.79 12.41 50% 1.36 16.89 1.00 19.31 1.48 16.89 30% 0.30 21.94 0.21 24.63 0.32 21.94

Table 1 – Necessities of Thermal energy of the Amphitheaters

Figure 8– View of the annual thermal energy evolution for the different level of occupation

Main System Alteration The main action lines to highlight are the following ones:

o Displacement of all of the active systems from the initial location (covering of the amphitheaters) to a zone of the covering were central corridor of the building B is located;

o Replacement of AHU's with box of mixture of three branches for a equivalent AHU's with insulating panels and acoustic attenuators;

o New dimensioning of the supply and extraction fans; o Placement of acoustic attenuators before the extraction and after the supply fans,

the global reduction should be approximately 30 dB(A); o Dimensioning of a new network of covered and insolated ducts to establish the

connection to the new equipment location; o Inclusion of CO2 detectors and temperature probes in the return conducts, making

possible the compatibilization of the operating systems with the rate of occupation of the amphitheaters;

o Inclusion of systems capable to absorb vibrations and machine stabilization, preferentially, in flotation platforms to be integrated in the covering;

The three AHU should have the following base technical characteristics: Insulated air flow: 9950 m3/h; Fan speed rotation: 775 RPM; Nominal cooling capacity: 49.4 W; Nominal heating capacity: 47.8 kW; Motor input: 2.2 kW;

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Frequency (Hz) 63 125 250 500 1000 2000 4000 Global

AHU without acoustic attenuators 77 76 73 71 70 68 64 76

AHU with acoustic attenuators 71 65 55 40 25 28 34 53

Table 2 – Profile of acoustic reduction dB(A) - AHU's

Frequency (Hz) 63 125 250 500 1000 2000 4000 Global

Acoustic attenuators 10 16 29 46 50 50 50 56

Table 3 – Acoustic attenuation profile dB(A)

Performance Data Results still don’t exist in what concerns the performance data, although an estimative was made and is already included in study. Three key factors were considered for this study:

o Improvement of the energy efficiency provoked by the improvement of air low in the insulation ducts, at the external level. – Work in Progress

o Improvement of the global efficiency o Energy results without and with CO2 controller

To make the analysis of the thermal energy needs of the space to acclimatize, in which the HVAC system can incorporate a CO2 controller, a dynamic simulation program was used (TRANSYS). For the development of this simulation it was established, according to the system operation method, the following considerations:

Schedule of the system operation; Occupation of the amphitheaters for the classes schedule; Internal gains; For the simulation of the system with CO2 controls was necessary to establish a low operation regime(minimum flow) in case it existed a low occupation rate of the building spaces;

Taken these into concern were obtained the following results: 100% of total occupation The following graphs illustrate the difference between, the energy needs obtained for the HVAC system in existence with and without CO2 control. After a careful analyzes of the graphs results we can conclude that the system without CO2 control has larger energy expenses comparatively to the system with CO2 control. This difference is shown in the graphs for each room and for each occupation rate.

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100 % of total occupation

75% of total occupation

50% of total occupation

30% of total occupation

The annual energy gains achieved, with the implementation of CO2 controller in the current HVAC system are represented in the table below.

Table 4 – Percentage of Thermal energy gains

As it is confirmed by the graphic evolution and by the table above, the thermal energy gains, for the use CO2 system controller, increase with the decrease of the student’s presence to classes. Below is represented graphically the spectrum of acoustic reduction for the different frequencies, of the proposed acoustic attenuators. The spectrum still presents the measured noise levels in the Amphitheater B001, the noise curves for the formed "Roof -Top" and AHU’s group, and the respective NC 30 and NC35 curves.

% B002 B003 B001 B002 B003 B001 100% 0.05 0.08 0.87 6.91 9.40 16.92 75% 0.17 0.04 2.57 5.37 7.58 13.79 50% 4.41 0.01 0.21 10.75 14.23 16.36 30% 48.94 4.65 4.88 39.10 46.35 48.52

Different level of occupation

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Graph 1 - Profile of the levels of noise in the Amphitheater B001

Construction and Operating Costs of New System According to the proposed HVAC system, the expected budget rounds 90 000 € and the operating costs will decrease in comparison to the current system.

The analyses made relatively to the savings achieved by the implementation of the proposed system allow us to conclude that the energy earnings won't compensate the investment done, however, the installation of the proposed system will guarantee the thermal and acoustic comfort necessary for the correct operation of the amphitheaters. Final Analysis The proposed solution presents certain advantages when compared with the existing system:

f. The acoustic comfort is established; g. The quality of the interior air is guaranteed; h. Decrease in energy consumption; i. The use of free-cooling and all compensation inherent of this cooling method.

Suggested ECO’s and O&M The study has identified the following different ECO’s that may lead to significant energy savings, with acceptable recovery times for the investment: ECO’S - VENTILATION / AIR MOVEMENT / AIR LEAKAGE IMPROVEMENT E2.1 Generate possibility to close/open windows and doors to match climate PLANT – ECO’S - COOLING EQUIPMENT / FREE COOLING P2.1 Minimise adverse external influences (direct sunlight, air flow obstructions, etc.) on cooling tower and air cooled condenser (AHU, packaged, split, VRF systems) P2.5 Improve central chiller / refrigeration control P2.6 Replace or upgrade cooling equipment and heat pumps PLANT – ECO’S - AIR HANDLING / HEAT RECOVERY / AIR DISTRIBUTION P3.3 Use the best EUROVENT class of fans P3.4 Use the best class of AHU P3.11 Generate possibility to increase outdoor air flow rate (direct free cooling) P3.13 Modify ductwork to reduce pressure losses

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O&M - FACILITY MANAGEMENT O1.1 Generate instructions (“user guide”) targeted to the occupants O1.2 Hire or appoint an energy manager O&M - GENERAL HVAC SYSTEM O2.4 Maintain proper system control set points O2.5 Adjust internal set point values to external climatic conditions O&M - FLUID (AIR AND WATER) HANDLING AND DISTRIBUTION O4.6 Eliminate air leaks (AHU, packaged systems) O4.7 Increase outdoor air flow rate (direct free cooling)

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Portuguese Case Study 3 PCS3 Library

André Borges, André Poças, José Luís Alexandre FEUP/INEGI – Instituto de Engenharia Mecânica e Gestão Industrial - Porto Date: December 2006

The system installed is centralized. There’s a boiler and a chiller on the roof that feed the chilled and hot water loops respectively. The air loop is handled by an air handling unit.

Introduction The new Campus of Faculdade de Engenharia da Universidade do Porto (FEUP) has different types of buildings and most of them don’t have an HVAC centralized system installed. Due to the specific application of some of these buildings it was necessary to study the cooling capacities according to the type of the building. In the majority of the cases the actual HVAC system is neither adjusted to the demand of the several spaces nor to the type of buildings. The present document intends to evaluate the performance of one of those systems installed in the Library of the FEUP and also the assessment of performance of both the air and water distribution and the efficiency of the system. The temperatures verified in this space are different from those of the project, providing the occupants thermal discomfort. In order to solve the problem of the thermal comfort, it was necessary to proceed to a rigorous analysis of all the air conditioned plant, evaluating the air and water distribution and the efficiencies of the primary systems, (chiller and boiler) The original HVAC is composed by two Boilers and two chillers, existent in the covering of the building that supplies the all library.

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Building Description

Project Data

Location Porto, Portugal Latitude 41,1 N

Longitude 8,6 W Altitude 73 m

Year of construction 1996/2001 Number of Working spaces 15

Degree days (20) 1437 Heated floor area 5100 m2

Heated space 17330 m3 Cooling floor area 5100 m2

Cooling space 17330 m3 Inst. heating capacity 515.6 kW Inst. cooling capacity 480 kW

Illumination 10 W/m2 Report Prepared by: Andre Borges and José Luís Alexandre

The Library is a block of FEUP that has eight floors which (including the covering); each floor holds an independent air handling unit (AHU) whose objective is to provide the maximum of comfort to their occupants, during study or work. The middle floors of the building, floors 1 to 4 have a central void that connects them. This building includes all the necessary administrative services for the correct library functioning, and has also a bar that is situated in the floor -1. The installed system causes a difficult problem related to the thermal comfort provoking a bad ambient of work and study. Due to the high rate of discomfort present in this building, the main objective of this audit is to evaluate the correct system without thermal comfort problems. HVAC system description In general, the climatization system that equips the library can be defined as a mixed air-air system and air-water system, the air handling units and fan coil units work simultaneous. This installation is constituted by a thermal control center were the hot and cold water is produced , located in the covering, and a network of distribution pipes, two pipes for the supply and two for the return, of both hot and cold water, respectively. The two independent circuits supply the existent heating and cooling batteries of the air handling units (AHU) located in each of the floors, as well as fan coils units located in the several cabinets of the 6 floor. The absorption chillers produce cold water and the boilers produce hot water. Both of these equipments are supplied by natural gas. Two cooling towers are part of the cooling water production. To complete the system description, there is a ventilation system that possesses an air supply and return ducts that supply each one of the AHU’s, as well as an extraction air system. The different AHU's are controlled in a centralized way.

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As a response to the topology of the building there was the need to include direct expansion units (designated commercially by splits) on the south facade of the building, middle floors, being used preferentially during the cooling station.

Figure 3 – View of the Chiller Figure 5– View of the Boiler Figure 4–Cooling towers

Building envelope For better evaluate the energy needs of the building it was necessary to typify the materials used in the construction of the envelope. The following table describes the type of building envelope and respective values for the thermal transmission coefficients, U [w/m2], of each constructive element.

Description U

(W/m2.ºC) Umáx

RCCTE2006 (I1)

Exterior wall 0.681 1,8

Interior wall 1.833 2

Slab 1.327 1,65

Roof 0.514 1,25

Glazed 4.5

Table 5: Thermal transmission coefficients

Climatic data of the place (external temperature; total monthly incident radiation). According to RCCTE (Portuguese building thermal regulation) the building in study is located in the area I2V1 and it presents the following values:

Degree Days (20ºC) 1610 Duration of the heating station (months) 6.7 Medium solar energy incident Gsul (kWh/m2. month) 108

Exterior Temp. of project (ºC) 30

Thermal width (ºC) 9

Table 6: Climatic data

Control Strategy The comfort conditions are established for the circulation of air inside the areas to acclimatize. The circulation of the air is assured by the air distribution system constituted by AHU’s and ducts.

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The ducts are dimensioned to do supply and return a constant air flow, in other words, AHU’s incorporates one or two ventilation fans, depending on the flow of air intended to circulate, that works continually (constant flow), independently of the load loss provoked by the equipments that compose the whole air distribution system. Since the ventilation fans work with constant flow, the air supply temperature is variable, depending on the interior conditions of the space to acclimatize, the temperature of set-point imposed by the operator and the dead band temperature. In this specify case, if the set-point temperature is 22ºC, then the control temperature for the opening and closing of the valves of the batteries of AHU’s, will be 20 and 24 ºC respectively. Some places of the building namely the cabinets are equipped with fan coils units (FCU). These equipments are supplied, in parallel with the batteries of AHU's, for intermissions of the water distribution system, constituted by four tubes, two for heating and two for the cooling (one for supply and other for the return). The ventilation system is, also composed by the extraction system with the purpose of extracting the air for the whole building. The operation schedule for the AHU's it’s established between the 4:30 and 19:30 hours for five days of week and during the whole year. The ventilation fans for extraction are always in operation. In what concerns to the operation method of the primary system, the boiler just works during the winter period and with the same weekly operation that AHU's, while the chillers and respective cooling towers just work in summer period, and during the 24 hours for the five days of the week. HVAC system analyses Thermal comfort analyses A simple analysis of the temperature and humidity was made in order to evaluate the comfort conditions for a period of seven days in different areas of the building.

Graph 1 – Temperature evolution (dry bulb - Tdb) from 4 to 11 of February, of three cabinets of the floor -1

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Graph 2 – Temperature evolution (dry bulb - Tdb) from 4 to 11 of February, of several floors

Graph 3 - Relative humidity evolution of the interior air from 4 to 12 of February of three

cabinets of the floor -1

Graph 4 - Relative humidity evolution of the interior air from 4 to12 of February of several floors

After the analysis of the collected values the following conclusions can be taken:

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The Library has places with excessive temperatures (C-108) and simultaneously, extremely low temperatures (floor 1). Low humidity values are usually present, a predictable effect since most of the time the humidification systems are turned off. There is and overheating on the south facade of floor 0 and 1 although the AHU’s that affected these floors maintains the heating battery ON – continuing the supply of hot air. Such fact occurs because the temperature sensor is badly placed. To solve this problem, the AHU's heating batteries that supply these places were turned off and a commitment solution was implemented, supply the space with outside air not treated. This intervention was made on February 4 for the Floor 0 and for the remaining spaces with overheating, three days later. The resulting effect was the expected, there was a decrease of the indoor temperature but even so the available flows were insufficient. This overheating effect was more intense in the Floor 4. In floor 1 we confirmed that the temperature is approximately 17 ºC while the relative humidity of the interior air presents daily medium values inferior to 30%. This effect had already been observed during 26 January to 1 February, never reaching 20 ºC.

Regarding all the previous conclusions analyzed the following remarks were drawn:

The interior temperature in offices C-108, C007 and Floor 4 presents values that are superior to the comfort values recommended by AHSRAE; It was confirmed that the interior temperature, in the Floor 0 and Floor 1, presents values that are inferior to the comfort values recommended by AHSRAE; The relative humidity shows some fluctuations, more tangible in office C009, of the Floor 0 and Floor 1. The relative humidity has usually inferior values comparatively to the recommended limits of ASHRAE; The temperature differences and relative humidity of the interior air obtained, starting from the two positions of measurement of the Floor 1, are not relevant; The thermal comfort is not established, this causes a dissimilarity of heat and cold sensations. For this reason the employees’ and remain users of the Library complains were properly justified.

After the simple analysis previously described, a more intense one was made and the following conclusions were drawn:

Bad existent control of the ventilation fans of AHU's , this disestablish the necessary air supply flow, see graph 5 and 6; The circulated air ducts are inadequate; The percentage of return air isn’t established; The percentage of extracted air isn’t established; The humidification system is turned off

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Supply

- 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00

AHU

_NA

0.1

AHU

0.2

AHU

0.1

AHU

_NA

1.1

AHU

1.1

AHU

1.2

AHU

6.3

AHU

_NA

6.1

AHU

7.1

and

7.3

AHU

7.2

Thou

sand

s [m

^3/h

]

REAL PROJ.

Graph 5 - Comparison between the project and real air supply for the floors -1, 0, 5 e 6

Supply

-

5.00

10.00

15.00

20.00

25.00

AHU

2.1

to 2

.4

AHU

3.1

to 3

.4*

AHU

4.1

to 4

.4*

AHU

5.1

to 5

.4*

AHU

6.1

and

6.2*

Thou

sand

s [m

^3/h

]

REAL PROJ.

Graph 6 - Comparison between the project and real

air supply for the floors 1,2,3,4 e 6 This results in a impasse situation if the ventilation fans aren’t properly controlled. There’s a decrease in terms of the thermal comfort. In other hand, if the ventilation fans are controlled properly there's an acoustic discomfort. Energy analysis In the year of 2005 the annual consumption of the Library was the following:

MWh m3 tep Electric energy 512* - 148

Natural gas - 46869 43 TOTAL 125

Table 3: Energetic consumption - 2005

* Obtained value based on measurements The values presented in the previous table are shown in the figure 5. The electric energy represents the larger consumer of the library global consumption being 78% of the total consumption. The natural gas consumption, regarding the AVAC system of the building, is due to the boilers and chillers, equipments responsible for the production of hot and cold water. All the remaining energy needs, are established through electric energy. The energy consumption breakdown showed in figure 5 was based on the measurement of electric power made during the audit. The main consumers are: illumination, equipments, ventilation fans of the AHU’s, extraction fans and direct expansion systems distributed along the building (splits).

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Figure 5: Global consumption disaggregation

Figure 6: Desegregation of the "Building system" Electric power

for the normal operation conditions

In figure 7 the thermal consumption desegregation is specified. We can see that the chiller has the largest weight in the thermal consumption. For the energy consumptions analysis of the building, it becomes necessary to evaluate the resources used. With this, and through the audit, it was possible to obtain different percentages based on the resources used by the “building system ", exemplified in the following illustration.

Figure 7: Desegregation of "Building system" in thermal Energy

Figure 8: Resources rate used by the "Building system" in the normal operation conditions.

By analyzing the figure above, we can see that the most used resources are “others” and “lighting” this correspond to almost 50% of the total resources. This means that the activity of the building approaches a typical profile of an office building. The rate regarding the resource "others" includes informatics equipments, printers and elevators.

Main System Alteration It was used a simulation program, Trnsys to evaluate and obtain solutions that could be implemented in the building. The simulation of possible alterations to the building and/or to the operation of the HVAC system is quite important when the final objective is the decrease of "Building system" energy consumption. The main proposed alterations are:

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A. Different control of ventilation using the number of people in the considered areas as control strategy. For the execution of the simulation was considered a 35 m3/h flow per person.

B. Application of a lighting maximum limit, 8w/m2 in the areas that the lighting was superior to 8w/m2.

C. Vertical and horizontal shadings of 1m in length were introduced in the east facade.

D. Entrance door alteration, in other words, substitution of the current door that provoked a 700m3/h infiltration for a “rotative” one.

E. Alteration of the AHU set point's values for the recommended RCCTE values. 20ºC for heating and 25ºC for cooling.

The alterations A and E compel a 42.8% decrease of the thermal energy consumption. This is an important decrease to the building global energy consumption, starting to consume 132 MWh of thermal energy, or, about 25.9kWh/m2. This value can be affected by 1.2, (considering a medium efficiency of 80% for the absorption chiller and boiler) acquiring the natural gas energy consumption of 31.1 kWh/m2. With this, and using a conversion factor 0.086 kWh/kgep we obtain a consumption of 2.7kgep/m2 in what concerns the primary energy, which is 60% inferior to the obtained for the real situation. To implement those two improvements previously described is necessary to do some extremely important alterations in the existent facilities:

- Introduction of acoustic attenuators - Implement an effective system to control the air distribution

Performance Data These results are interesting, we can verify the type of annual energy consumption evolution for the real and simulated systems. The illustrations 9 and 10 present that same evolution.

Figure 9: Monthly consumption of thermal energy,

concerning natural gas invoicing

Figure 10: Monthly consumption of thermal energy, obtained

by simulation - Trnsys Analyzing the natural gas demand, a random evolution of the gas consumptions is verified along the year. This is a difficult factor to take into account for the simulation. The monthly results of the energy consumption obtained using TRNSYS will be presented subsequently. As expected, in the summer when the days are hotter the cooling needs are higher than heating needs and vice-versa for colder days.

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The building in study has the natural gas as is main source of energy for the primary HVAC system needs, 22%, and the electric power that collects all the other needs, being the source of energy that is more consumed (78%). The following table shows then energy consumption for each For each implemented layout alteration comes the energy consumptions:

MWh % % Real

Alterations 308,8 100.0 0.0

A 252 81.8 18.2 B 308 99.9 0.1 C 310 100.7 -0.7 D 308 99.8 0.2 E 232 75.4 24.6

Table 7 – Economy of energy in the accomplishment of some measured

Suggested ECO’s and O&M The study has identified the following different ECO’s that may lead to significant energy savings, with acceptable recovery times for the investment: ECO’S - ENVELOPE AND LOADS E1.1 Install window film or tinted glass E1.4 Replace internal blinds with external systems ECO’S - VENTILATION / AIR MOVEMENT / AIR LEAKAGE IMPROVEMENT E2.1 Generate possibility to close/open windows and doors to match climate E2.8 Replace doors with improved design in order to reduce air leakage OTHER ACTIONS AIMED AT LOAD REDUCTION E4.5 Replace electrical equipment with Energy Star or low consumption types E4.6 Replace lighting equipment with low consumption types E4.7 Modify lighting switches according to daylight contribution to different areas E4.8 Introduce daylight / occupation sensors to operate lighting switches E4.9 Move equipments (copiers, printers, etc.) to non conditioned zones PLANT – ECO’S - BEMS AND CONTROLS / MISCELLANEOUS P1.4 Modify control system in order to adjust internal set point values to external climatic conditions P1.5 Generate the possibility to adopt variable speed control strategy PLANT – ECO’S -COOLING EQUIPMENT / FREE COOLING P2.1 Minimise adverse external influences (direct sunlight, air flow obstructions, etc.) on cooling tower and air cooled PLANT – ECO’S -AIR HANDLING / HEAT RECOVERY / AIR DISTRIBUTION P3.6 Apply variable flow rate fan control P3.7 Consider conversion to VAV O&M - GENERAL HVAC SYSTEM O2.1 Use an energy accounting system to locate savings opportunities and to track and measure the success of energy – efficient strategies O2.4 Maintain proper system control set points O2.5 Adjust internal set point values to external climatic conditions

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Portuguese Case Study 4 PCS4 Laboratory

André Borges, André Poças, José Luís Alexandre FEUP/INEGI – Instituto de Engenharia Mecânica e Gestão Industrial - Porto Date: December 2006

The studied AHU is composed by two fans, electric resistances for heating and a DX system for cooling. The filters tested were placed on the fresh air inlet side

Introduction In the climatization Laboratory, of the department of Mechanical Engineering, Fluids and Heat division of the Faculdade de Engenharia da Universidade do Porto, exists an air handling unit (AHU) that serves as a support for several experiences. The department decided to do a test to its energy efficiency in contrast to the physical state of the filters used in the unit, all of the comfort situations were established.

Building Description

Project Data

Location Porto, Portugal Latitude 41,1 N

Longitude 8,6 W Climate type mild

Altitude 73 m Year of construction 1996/2001

Number of Working spaces 1 Degree days (20) 1437 Heated floor area m2

Heated space m3 Inst. heating capacity 12 kW Inst. cooling capacity 21 kW

Fan supply 514.3 W Fan return 324.2 W

Illumination Building type Laboratory

Report Prepared by: André Borges and José Luís Alexandre

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HVAC system description The AHU structure is the following:

♦ two ventilation fans, one for return and other for admission;

♦ two batteries, one for cooling and other for heating, supplied by a DX system and three electric resistances, respectively;

♦ an heat recover exchanger:

♦ a filter in the admission of fresh air;

♦ and a dampers group, that control the flows.

Characteristics of the ventilation fans:

Return Fan

• Flow rate: 3800 m3/h 1.06 m3/s

• Pressure: 50 Pa

• Absorption power: 372.82 W

• Motor power: 550 W

Supply Fan:

• Flow rate: 3800 m3/h 1.06 m3/s

• Pressure: 50 Pa

• Absorption power: 514.3 W

• Motor power: 750 W

Filter characteristics:

• Cellule type: F2

• Efficiency G4: 90% gravimetric

• loss of introduced load: 55.4 Pa

Figure 2 – View of Chiller

1 – Outside air 2 – Outside air after the heat recover 3 - Air (mixed) before the cooling battery 4 - Air after the cooling battery 5 – Air supply (after the cooling battery) 6 – Return air (air of the space) 7 – Return air after the heat recover (extraction)

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Control Strategy The figures 3 and 4 show the simplified schematic of the control algorithm implemented by the BAS 2800+ software. This algorithm is defined to control the whole thermal system. Basically, it can be described in the following way: 1. In each instant the system measures the temperature value of the return air of the room, compares it with the established reference value, set point, and verifies the needs for cooling or heating the space. 2. In the cooling mode, before the cooling battery is turned on, the system analyses the possibility of using free cooling, this will occur if the outside air enthalpy is inferior to the room air enthalpy. 3. Still in the cooling mode and as a technical require of the cooling battery so it can work properly, the minimum air flow must be 2500 m3/h. 4. In both cooling and heating modes, the system analyses the possibility of energy recovery, using a heating recover or selecting the respective by-pass system.

BEGIN

Return temp. (θret) θret > θref Return enthalpy > ambient enthalpy

Free-cooling ON

Cooling ON

Cooling ON

qret - qamb > 2ºC

qret - qamb < 2ºC

Cooling ON

Heat exchanger ON Vmin = 2500 m^e/h

Vmin = 1500 m^3/h continue

Yes Yes

Yes

Yes

Figure 3 – Thirst part of the control algorithm simplified schematic

5. After attending the cooling and heating needs, the system evaluates the need to supply fresh air to the room, trying to maintain the CO2 concentration between the 500 and 1000 ppm, adapting the dampers of outside air, the three ways module and the ventilation fans. Below the 500 ppm, it’s not necessary to supply outside air to the room, the system works only with re-circulated air. Between 500 and 1000 ppm outside air is supplied to the room, through a proportional control, where the 1000 ppm corresponds to the maximum of outside air supplied to the room.

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6. In order to maximize the occupants comfort, the system tries not to exceed the 5ºC, difference value between the air temperature of the room and the supplied air temperature, for this the system employs the ventilation fans rotation velocity. If the thermal loads reach extreme values, it’s possible to ignore this condition, in order to quickly insure the desired conditions

CO2

|DT|>5ºC

Open air flow dampers

Heating ON Cooling ON

Go to the “begin”

Max (VCO2 , V1, Vmin)

Increase supply flow (V1)

Increase Fun Power

continue

Yes

Yes

Yes

VCO2

Figure 4 - Second part of the control algorithm simplified schematic HVAC system analyses Through a simple and direct analysis we verified that the dirty filters creates a rotation speed increase in the supply fan of about 6 rpm in order to maintain the constant flow. With this, and if the ventilation fan works continually for one hour, we would obtain a 360 rph, which is a quite accentuated difference relatively to the new (and clean) filters. It became then necessary to monitor the energy consumption during same periods for the two types of filters.

Figure 5– View of the filters

position

Figure 7– View of the

energy Monitor

Figure 6– View of the dirty filters

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Main System Alteration The main alteration to the system in order to maximize energy efficiency and minimize energy wastes is the replacement of the dirty filters for new ones. Performance Data

Figure 8– Outline of operation of the unit for the case of new filter

Figure 9– Outline of operation of the unit for the case of dirty filter

With the inclusion of new filters it is possible to obtain inferior energy consumption 6%, relatively to the use of dirty filters. Final Analysis and Suggested ECO’ s/ O&M This analyze prove, without a shadow of a doubt, that the lack of maintenance of the filters aggravates the indoor air quality and provokes a lot of waste energy. This study has also identified the following different ECO’s that may lead to significant energy savings, with acceptable recovery times for the investment: O&M - FACILITY MANAGEMENT O1.1 Generate instructions (“user guide”) targeted to the occupants O1.2 Hire or appoint an energy manager O1.3 Train building operators in energy – efficient O&M activities O1.5 Introduce benchmarks, metering and tracking as a clause in each O&M contract, with indication of values in graphs and tables O1.6 Update documentation on system / building and O&M procedures to maintain continuity and reduce troubleshooting costs O1.7 Check if O&M staff is equipped with state – of – the – art diagnostic tools

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Portuguese Case Study 5 PCS5 Service Building

André Borges, André Poças, José Luís Alexandre FEUP/INEGI – Instituto de Engenharia Mecânica e Gestão Industrial - Porto Date: December 2006

The HVAC system is centralized and composed by a boiler, a chiller and two ice storage tanks. The air distribution is done by using fan coil units.

Introduction The INESC building, located in the campus of Faculdade de Engenharia da Universidade do Porto is a typical service building with typical functioning hours, from 9:00h A.M to 8:00h P.M, five days a week. This building is composed by the zero floor and 4 other floors used for services. In the basement there is a document archive and in the roof there are the thermal sources (boiler and chiller). Building Description

Project Data

Location: Porto, Portugal Latitude: 41.2 ºN

Longitude: 8.7 ºW Altitude: 73 m

Year of construction 19.../20... Degree days (20) 1437 K.d Heated floor area 3235 m2

Heated space m3 Inst. cooling capacity 185.5 kW Inst. heating capacity 233 kW

Design Details The air conditioning system existent in INESC is a 4-pipe semi-centralized system, having as thermal energy source a chiller for cold water production and a boiler for hot water production. The energy distribution thru the circuit is done using circulating pumps. These pump groups are located on the top of the building, as well as the chiller and the boiler.

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The terminal units used in the several spaces are 4-pipe fancoils. The air renovation inside the spaces is assured by an air handling units (AHU) which uses only outside air. There is one of this AHU in each floor. Complementing this system, there are exhaust fans to equilibrate the air flow balance inside the zones. In this building there are also two ice storage tanks with 670 kWh of capacity that are recharged during the nocturnal period, when the electricity is less expensive. During the day the stored ice is used to produce chilled water and consequently reduces the chiller’s working hours during the day when the electricity is more expensive. This system is divided in two main circuits: the primary circuit and the secondary circuit. The primary circuit is composed by the thermal sources (chiller and boiler) and the distributors. The secondary circuit makes the connection between the distributor and the terminal units (fancoils and the coils in the AHUs) The table above resumes the equipment existent per floor.

LOCALIZAÇÃO EQUIPAMENTOS Roof Boiler + Pumps 5th floor AHU + V exhaust + Fancoils 4th floor AHU + V exhaust + Fancoils 3rd floor AHU + V exhaust + Fancoils 2nd floor AHU + V exhaust + Fancoils + close control 1st floor AHU + V exhaust + Fancoils 0 Chiller + AHU + Splits

Main equipment characteristics The main characteristics of the principal equipments are: Chiller: Boiler

Designation CH 1

Cooling capacity (kW) 151

Nr of compressors 4

Input power (kW) 55

Freon R 407 C

Designation CAQ 1 Heating power (kW) 233

Max flow (m3/h) 10.0

Max pressure (bar) 5

Efficiency 83.7 %

Fuel type 1 Natural gas

Close control Splits

Designation CC 1 Cooling capacity (kW) 24,8

Nr of compressors 1

Input power (kW) 7,34

Freon R 407 C

Designation UC 1 UC 2

Cooling power (kW) 7,1 2,6

Nr of Compressors 1 1

Input power (kW) 2,7 0,9

Freon R 410 A R 410 A

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Cooling Heating

Model

Air flow

(m3/h)

Water temperature 7-12 ºC

Water temperature 80-60 ºC

Total cooling power

(kW)

Sensible cooling

(kW)

Dry bulb air outlet

temperature (ºC)

Heating power

(kW)

Dry bulb air outlet

temperature (ºC)

VC 1 187 0.8 0.72 12.6 0.96 35.0

VC 2 227 0.9 0.84 13.0 1.10 34.0

VC 3 281 1.03 1.0 13.5 1.65 37.0

VC 4 374 1.2 1.2 14.4 1.98 35.4

VC 5 400 1.79 1.61 12.0 2.50 38.2

VC 6 500 2.19 1.96 12.0 2.89 36.8

VC 7 774 2.33 2.33 15.0 4.55 37.1

VC 8 928 2.67 2.67 15.5 5.0 36.0

VC 9 1062 4.0 3.55 14.0 6.68 38.0

VC 10 1213 4.66 4.0 14.2 7.24 37.0 Ice storage

Designation BG1

Storage capacity (kWh) 670

Max functioning temperature ºC 38

Quantity 2

Building Envelope The constitution of the building envelope is given in the table bellow Exterior Wall e [m] Cp [kJ/kgºK] λ [W/mºK] r [kg/m3] U [W/m2K]

Plaster 0.015 0.837 1.150 1950

Concrete 0.3 1.080 1.750 2200

Polystyrene 0.05 1.250 0.035 32.5

Plaster 0.015 0.837 1.150 1950

0.560

Interior Wall e [m] Cp [kJ/kgºK] λ [W/mºK] r [kg/m3] U [W/m2K]

Plaster 0.02 0.837 1.150 1950

Brick 0.15 1.080 1.750 2200

Plaster 0.02 0.837 1.150 1950

2.774

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Slab between floors e [m] Cp [kJ/kgºK] λ [W/mºK] r [kg/m3] U [W/m2K]

Linoleum 0.002 1.0 0.169 1000.0

Light slab 0.30 0.965 0.931 1320

Gypsum 0.05 1.085 0.220 1680

1.313

Ground Slab e [m] Cp [kJ/kgºK] λ [W/mºK] r [kg/m3] U [W/m2K]

Linoleum 0.002 1.0 0.169 1000.0

Concrete 0.3 1.080 1.750 2200

Polystyrene 0.05 1.250 0.035 32.5

Plaster 0.015 0.837 1.150 1950

0.567

Door e [m] Cp [kJ/kgºK] λ [W/mºK] r [kg/m3] U [W/m2K]

Wood 0.03 2.750 0.150 550 2.703

Solar and Overheating Protection The glazing constitution and properties are showed in the table below:

Glazing e [m] Cp [kJ/kg.ºK] λ [W/m.ºK] r [kg/m3] U [W/m2K]

Double glass 6mm/6mm 0.850 4000 2800 4.00

Solar transmittance = 0.75 The shading of the building is composed basically by vertical and horizontal shading

devices. There is no interior shading. Control Strategy The HVAC systems works according to a schedule that varies with the rooms application. The table bellow resumes the different room’s existent in INESC as well as their typical utilization schedule.

Type of room Functioning schedule

Offices and common areas From 9:00 to 20:00, 5 days a week

Reunion offices and audience rooms From 10:00 to 13:00, once a week

Server rooms and common areas with natural

ventilation 24 hours a day, 7 days a week

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Fig. 2: Screenshot of the management program

The temperature set points are:

Summer: 25 ºC Winter: 20 ºC Performance Data Building Energy Performance The amount of energy used in the year of 2005 is described below. The natural gas is used for heating only. Some measurements were done between January 28th and February 5th. The results showed in fig. 4

INESC Energy consumption for 2005

Electricity Natural gas

[kWh] [m3]

January 32774 904

February 32836 849

March 34340 855

April 42732 396

May 37162 41

June 43540 2

July 38299 9

August 42146 1

September 40924 4

October 45872 706

November 43766 1243

05000

100001500020000250003000035000400004500050000

Janua ry

FebruaryMarch

AprilMay

JuneJuly

August

September

October

Novembe r

December

Elec

trici

ty [k

Wh]

0200

400600800

10001200

14001600

Natu

ral g

as [m

3]

Natural gas [m3] Electricity [kWh]

Fig. 3: Energy consumption for the year of 2005

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Fig. 4: Energy measurements for the period between January 28th and February 5th.

The principal energy consumer sectors are the heating, cooling, lighting and the electric equipments existent in the building. The fig. 5 shows the partition in the energy consumption by sector.

Fig.5: Electric Energy consumption by sectors Fig.6: Energy demand for heating and cooling obtained by detailed simulations

The chiller (compressor) consumes about 25% of the total INESC’s electric energy consumption. The whole building’s climatization system (Boiler, Ventilation, Pumps, Splits, Chiller) represents 42% of the total energy consumption. Cooling and heating performance Using detailed simulation software (TRNSYS and EnergyPlus), it was possible to obtain the cooling and heating loads, as well as the cooling and heating demand profile. Ventilation Performance As said before, the air renovation is done using AHU that use only fresh air. The air enters the space by the insulation grilles existent near to the ceiling in each floor. The air exhaust is also done in each floor using extraction grilles. Proposed solutions In order to reduce the cooling energy consumption, there are some measures that can be taken into account:

The correct programming of the central command computer will enable the system to do “free-cooling”. This measure makes sense because the outside air temperature can be sufficient to remove the thermal loads for several months

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even in some summer periods. This would result in the decrease of 35 MWh/year in cooling energy reduction.

Suggested ECOs and O&M The study has identified the following different ECO’s that may lead to significant energy savings, with acceptable recovery times for the investment: ECO’S - ENVELOPE AND LOADS E1.3 Operate shutters, blinds, shades, screens or drapes E1.1 Install window film or tinted glass E1.2 Install shutters, blinds, shades, screens or drapes ECO’S - OTHER ACTIONS AIMED AT LOAD REDUCTION E4.5 Replace electrical equipment with Energy Star or low consumption types E4.6 Replace lighting equipment with low consumption types E4.7 Modify lighting switches according to daylight contribution to different areas E4.8 Introduce daylight / occupation sensors to operate lighting switches E4.9 Move equipments (copiers, printers, etc.) to non conditioned zones PLANT - ECO’S - COOLING EQUIPMENT / FREE COOLING P2.10 Consider indirect free cooling using the existing cooling tower (free chilling) P2.11 Consider Indirect free cooling using outdoor air-to-water heat exchangers O&M - GENERAL HVAC SYSTEM O2.1 Use an energy accounting system to locate savings opportunities and to track and measure the success of energy – efficient strategies O2.4 Maintain proper system control set points O2.5 Adjust internal set point values to external climatic conditions

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Slovenian Case Study 1 SCS1 Office Building

University of Ljubljana, Faculty of Mechanical Engineering Date: December 2006

The building is heated with a combined heat-pump (water-water) which provides heating and cooling energy. As a support for heating there is also a low temperature condensing gas boiler. Whole space is ventilated with high energy efficient ventilation / air conditioning units with energy recovery more than 90%. There is also a possibility of direct cooling with ground water. In summer period, it has a temperature of 15 – 16ºC.

Introduction The energy system of the presented office building, achieves at minimal energy consumption optimal working conditions. The investment costs are in the same range as the investment costs for a traditional building. Building is heated with a combined heat pump (water – water), which prepares heating and cooling medium for the whole building. Heating source is ground water from a spring. Heat and cooling energy are partly transmitted into the object by thermal activation of concrete construction and by supplied air from ventilation units. Local regulation of temperature is possible through local heating coils, built in special displacement air distributors. Whole space is ventilated with high energy efficient ventilation / air conditioning units with energy recovery more than 90%.

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Building Description

Project Data Location: MARIBOR, Slovenia Altitude: 273 m Year of construction 2004 Number of Working spaces 70 Degree days (20/12)3300 Kd (temperature deficit) Heated floor area 2720 m2

Heated space 8160 m3

Inst. heating capacity 102 kW Inst. cooling capacity 81kW Costs in € · 2.980.000 EUR

Design Concept General Energy Concept Building is glazed with a non – reflective glass, most of the sun’s heat is transferred to the building. Insolation can however be regulated with outside sunscreens, so that in warm weather glazing is shielded to prevent overheating. South side of the building is a complete glass wall. It is positioned in a specific angle (can be seen on Fig. 1), so that sun beams can not reach the spaces in late spring, summer and early fall. This way, architectural construction prevents overheating in warm periods and makes the passive insolation is possible during winter. Building Envelope Outside walls are reinforced concrete construction, insulated with approx. 16 cm mineral wool thermal insulation. U value is 0,22 W/m2K. Facade made from aluminum profiled plates with 1 cm air gap to the insulation layer. Roof construction is also a reinforced concrete construction, with thermal insulation made of extruded polystyrene, thickness 16 cm. Roof is than sand banked and covered with concrete tiles. Roof construction has also an U value of 0,22 W/m2K. Wall construction in the basement is reinforced with concrete. Insulation layer is made of extruded polystyrene, thickness 16 cm, 1m deep in the ground (freezing zone), deeper is 8 cm. U value is 0,35 W/m2K. Solar and Overheating Protection As already described above, glazing is a two – layer glass type, argon filled. It is combined with high quality aluminium profiles, with interrupted thermal bridges, thermal insulated. It also exist plenty innovative details concerning the interruptions between the thermal bridges and the glazing connections with the concrete construction. Design Details Building is heated with a combined heat pump (water – water), which prepares heating and cooling medium for the whole building. Heating source is ground water from a spring. Alternative heat source is a low temperature condensing gas boiler, in case the heat pump fails. In previous periods, the gas heating was also used at high electric rates. Heat and cooling energy are partly transmitted into the object by thermal activation of concrete construction and by supplied air from ventilation units. Local regulation of temperature is possible through local heating coils, built in special displacement air distributors. Whole space is ventilated with high energy efficient ventilation / air

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conditioning units with energy recovery more than 90%. There is also a possibility of direct cooling with ground water. In summer period, it has a temperature of 15 – 16ºC.

Control Strategy Ambient temperature set point is 22 – 23ºC in winter and 25 – 27ºC in summer. Also at higher temperatures in building (27ºC), there is possibility of dehumidifying the supply air in ventilation / air conditioning units, this makes working and living conditions in object totally acceptable. Digital control system The building is realized as an intelligent building. All functions that are linked to the thermal energy system, lighting, watering system, melting snow and ice on the parking places, sunscreens are controlled with a unified system of digital controllers that can directly communicate with each other without any interfaces. The controllers are freely programmable that enables a total flexibility of the system and easy optimization of the process operation. Central building managment system The entire digital control system is connected to a central building managment system. The traditional functions of the central building managment system are expanded so that it enables individual setting and adjusting of parameters at every work place.

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Building Energy Performance Annual energy consumption as follows (2005):

Electric: 80,4 MWh Gas: 5912 Sm3

Cooling Performance Performance of the cooling system is optimized for lowest possible energy consumption. Big amount of sensible heat is cooled with thermal activation of concrete construction it goes on large surface area, which means high cooling medium temperature – low energy consumption. Temperature of cooling medium in this system is 20 – 22ºC. The rest of sensible heat is cooled down with the supply air of ventilation / air conditioning units. As the ground water, which is the source for heat and cooling energy, has the temperature of 14 – 16ºC in summer, the building can be completely cooled direct with ground water for a long time in summer period. It is led into the concrete construction and water coolers in air conditioning units, after regulating on proper inlet temperatures on mixing valves in cooling energy distribution stations. Only at highest outer temperatures and humidity of outer air, the heat pump will prepare cooling medium – water 6ºC. This medium will cause efficient dehumidifying in AC unit’s water coolers and very efficient supply air cooling. The heat pump will than work with the highest known COP, because the condenser will be cooled down with ground water of 14 – 16ºC. At this time, this is the best known solution for cooling this object, so at this time, no further solutions have been studied to optimize the energy consumptions. Heating Performance The basic heat source is underground water. In winter it has a temperature around 10-13°C,o on the other side, we have thermal activated concrete construction with large heat areas, which means extremely low temperature heat medium of 25 – 26ºC, which assures that the heat pump works with a excellent coefficient of performance (COP) 5 – 6. A low temperature condensing gas boiler is also installed as an alternative heating system. Ventilation Performance Comfortable working conditions for employees are also achieved with a permanent supply of fresh air into the rooms with three air-changes per hour. Ventilation with 100% of fresh outside air wouldn’t be rational if it wasn’t done with ventilation and air conditioning units that have heat recovery of 92 % and humidity recovery of 87% at the lowest outside temperatures. In summer the air conditioning units also dehumidify the outside - inlet air when it is necessary, which assures comfortable working conditions even at extreme conditions of the outside air. Supply air is distributed through the displacement diffusers, mounted on the floor. They assure inlet of fresh supply air with minimal air velocities, so no draught is present. There are three ventilation / air conditioning systems in the building:

- Office rooms 1., 2., 3., floor – 12.500 m3/h, regenerative heat recovery, 92% sensible heat rec. efficiency, 87% latent heat recovery efficiency

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- Ground floor – 3.800 m3/h, regenerative heat recovery, 92% sensible heat recovery efficiency, 87% latent heat recovery efficiency

- Sanitation, dressing room, basement, storehouse – 2.100 m3/h, recuperative heat recovery, 83% heat recovery efficiency

Construction and Operating Costs After twenty four months of operation the building has without any doubt proven its energy efficiency and low energy consumption. As long as the building was heated only with natural gas (the heat pump was not operating) the average monthly costs for gas in winter 2004-2005 were 330,00 EUR. In this amount the heat losses of the building and ventilation losses of air conditioning units are included. Average cost of electricity for air conditioning units and pumps is 2.080,00 EUR per year. The cost for cooling is 1.050,00 EUR per year. The cost for lighting and computers is 2.250,00 EUR per year. It has to be taken in consideration that about 1.200 m2 of the building is momentarily in use and the ventilation system is working at 70% of its capacity, but the thermal activation of the concrete construction is in operation in the complete building in winter and also in summer.

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UK Case Study 1 UKCS1 Office Building

Dunn GN, Knight IP, Bleil de Souza C, Marsh AJ Welsh School of Architecture, Cardiff University Date: December 2006

The HVAC cooling system consists on chilled beams. The cold water production unit is a package air cooled chilled using R407c as refrigerant.

General Description of Case Study This case study illustrates an exceptionally energy efficient / low energy air conditioning system. The building is a purpose built 4 storey (Ground plus 3) 1980’s office building located in the centre on Leicester (UK), comprising of a mixture of large open plan areas and cellular of various sizes. Originally serviced by a perimeter wet-radiator heating system with natural ventilation, in 1998 a passive chilled beam comfort cooling system was installed which consumes less than 17% of the current good practice benchmark for annual A/C energy consumption. Building Description General Building Data: Configuration 4 storey (Ground + 3) purpose built office building

Layout "L" shaped 2 floors open plan, 2 floors cellular.

Number of floors 4

Floor area (Gross) 2414.5 m2

Floor area (Treated) 2195.3 m2

Refurbishment Fabric 1994

Refurbishment HVAC 1994

Refurbishment Lighting 1994

Refurbishment Other 1998 (installed comfort cooling system)

Space Activity Offices, meeting rooms, small gym.

Occupiers Business Type Government Offices

Type of tenancy Owner Occupied

Occupant density 17.4 m2 TFA / person

Tenancy Since 1994

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Caretaker / Porter Occupiers Own

Heating System Perimeter Radiators

Ventilation System Passive + Mech in stairwells only

Cooling System Chilled beams

Econ 19 Category Type 3 - Air Conditioned Standard

Building Category BRE OD4 - Day lit Open Plan Strip 1 to 4 Storeys

Types of fuel used: Heating Gas

Cooling Elec.

DHW Gas (Elec. Summer)

HDD 2276 Yearly Total on 20 year average Building Envelope: Windows

Type Double

Total Area 364.9 sq. m

Type of glazing Double w/ approx 12mm air void

Percentage of glazing by facade 23.9% North East

16.3 % North West

29.9 % South East

30.8 % South west

Glazing (U-value) 3.4 W/(m2.K) (Office areas)

Window Reveals & Overhangs (Size & Loc.) Reveals <25mm / Eaves none

External shading devices (Size & Loc.) None Specific

Internal shading devices (Type) Vertical Blinds

Internal shading devices (Location) Immediately Inside of Glazing

Wall Structure Brick & block cavity wall construction

Wall Insulation fibrous cavity insulation per 1994 UK standards Roof Structure Mixed built-up flat & mansard w/ slate tiles

Roof Insulation Fibrous blanket type

Roof Area 408 m2

Ceiling Type Suspended perforated metal

Ceiling Height (Typical) approx 2.75 m

Floor to Floor Height (Typical) approx 3.25 m

Thermal mass Heavyweight construction concrete and masonry, but NOT exposed.

HVAC System Design General Information: The comfort cooling system is based on passive chilled beams serviced from a Unico packaged air-cooled chiller utilising R407c refrigerant. The packaged unit also contains all the distribution pumps for the chilled beams. Ventilation is provided naturally (as per the original building specification) and the original heating system also remains but has been refurbished with Powermatic boilers and heating pumps serving the perimeter radiators all of which have TRV’s.

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Controls are Satchwell and include optimisation based upon external air temperature, as well as, condensation risk control based on humidity. Other systems include a small DX split system which serves the IT-server room and ventilation pressurisation of the stairs wells, both systems are not considered in this monitoring. Monitoring of the chilled beam system showed this system to be exceptionally energy efficient. Detailed Information: Heating System

Boilers 2x Powermatic RS9 atmospheric rated @ 217.5kW each (173kW input)

Heating pumps Grundfos twin UPCD 80-120

DHW Pumps Grundfos up20-07N

Domestic hot water heater Lochinvar LG50T, gas fired rated @ 80.5 BTU/hr

Ventilation

General office areas Naturally ventilated with opening windows and passive trickle ventilators.

Stair well ventilation Nu Aire, Single pack inline single fan QSP 400.

Smoke room Nu Aire inline Centrifugal fan, ss-250

Air Conditioning

General Passive chilled beams serviced by packaged air-cooled chiller with integral distribution pumps.

Chiller (Unico A EW 96 E2 G7) Air cooled R407C with cooling capacity of 91.7kW normal & 110kW max. Packaged unit with integral compressors, heat-rejection fans and chilled water distribution pumps.

Compressors X2 each rated at 29.4kW (28amps) normal load (39amps max load).

Condenser fans x4 axial fans rated @ 0.96kW in total

Water temps Chilled water temps of 14 deg C flow & 18.4 Deg C return. @ 5.8 l/s.

Total Cooling Capacity 110kW

Cooling Capacity By area 50.1W/m2

HVAC Control Strategy *General Controls are Satchwell and include optimisation based upon external air temperature, with local thermostats on the cooling systems, TRV’s on all the perimeter radiators, and an interlock that prevents simultaneous heating and cooling or cooling when outdoor temperature is below 10°C. Monitoring of this system should that not only was the chilled ceiling system very energy efficient but it was also very well controlled, with operational hours limited to 1725 hours per year which also contributed to the low energy consumption of both this building and air conditioning system.

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Detailed data: HVAC Plant Control:

Satchwell SUT 4201 Optimised on external temperature and chilled ceiling supply temperature varied on humidity to avoid risk condensation.

HVAC zoning 3 zones per floor

Set Points Heating 18 deg C

Cooling based on localised floor controllers but with central override preventing cooling if external temp <10 deg C

Run times of HVAC plant 7:30AM to 18:00 PM Monday to Friday (normal occupancy) (Plant off during cleaning hours)

Planned maintenance Contract maintenance by sub-contractor to national standards

Performance Data General The following data illustrates the level of heat gains within the building during the period in which the AC system was monitored. Detailed Internal gains

Total Space Gains 29.2 W/m2 TFA

Occupancy 7.5 W/m2 TFA

Lighting 12.4 W/m2 TFA

Small Power 9.3 W/m2 TFA

Building Energy Performance *General Annual Building Energy Consumption 218 kWh/m2 TFA (Total Delivered)

Gas 141 kWh/m2 TFA

Electricity 77 kWh/m2 TFA

Detailed National benchmarks for delivered energy by building type

Actual building performance (% of benchmark)

Typical Practice - 404 kWh/m2 TFA 54%

Good Practice* – 225 kWh/m2 TFA 97%

* Set at 25th percentile based on 1998 national standards

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Cooling Performance *General Monitoring showed this AC (comfort cooling) system to be exceptionally energy efficient, well operated and maintained. The follow detail shows the overall performance of the building in practice. Detailed

Annual cooling energy consumption 7.4 kWh/m2 TFA (3.1% of whole building)

Chilled Ceiling System Energy Consumption

0.00

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0.40

0.60

0.80

1.00

1.20

1.40

1.60

jan feb mar apr may jun jul aug sep oct nov dec

kWh/

m2

20002001

Fig1: Monthly cooling energy consumption

Cooling Energy Consumption Vs. National Benchmarks

0.0

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60.0

70.0

80.0

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Series1 44.0 6.34 7.35 91.0

Good Practice 2000 2001 Typical

Fig2: Cooling energy consumption compared to national

benchmarks

Chilled Ceilings - Typical Summer Weekday Energy Demand

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Measured Chiller Part-load Profile

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Summary conclusions This case study illustrates an exceptionally energy efficient and well controlled comfort cooling system in a UK office building that utilised natural ventilation and passive chilled beams. It is particularly important because, like many UK office buildings, the comfort cooling system was retrofitted to a previously non-air conditioned building to meet rising demand for air conditioning due to increased internal gains, expectations of thermal comfort and commercial productivity issues.

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UK Case Study 2 UKCS2 Office Building

Dunn GN, Knight IP, Bleil de Souza C, Marsh AJ Welsh School of Architecture, Cardiff University Date: December 2006

The basic system configuration features passive chilled ceilings and perimeter passive beams with night-time ice storage and some DX systems serving computer rooms and conference suites. Ventilation is provided mechanically via centralised AHU’s and heating is provided by perimeter radiators.

General Description of Case Study This case study illustrates a 1960’s government office building in the heart of Westminster, which had a service refurbishment in 1996 to 1996, and underwent external fabric improvement at the beginning of the monitoring. The building comprises six-storeys (Ground plus 5) of mainly small cellular offices and a lower ground containing support and storage areas. Building Description General Building Data: Configuration Large concrete framed government building, predominantly

artificially lit. Layout Generally cellular offices w/ some open plan spaces.

Number of floors Ground + 8 storeys occupied

Floor area (Gross) 8888 sq. m.

Floor area (Treated) 8000 sq. m.

Year of construction: 1963

Refurbishment HVAC 1996

Refurbishment Lighting 1996

Refurbishment Other 2000 Space Activity Offices

Occupiers Business Type Government

Type of tenancy Owner occupied

Tenancy Since 1963

Heating System Gas fired wet radiators

Ventilation System Mechanical Ventilation

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Cooling System Passive Chilled Ceilings

Types of fuel used: Heating Gas

Cooling Elec.

DHW Gas

HDD 1977 Yearly Total on 20 year average

Building Envelope: Windows

Type Operable

Total Area 1320 sq m

Total Area operable 20% of total

Type of glazing Tinted double

Percentage of glazing by facade 28% North west

0% North East

31% South East

0% South West

Glazing (U-value) 3.4 W/(m2.K)

Size & location of trickle vents None

Window Reveals & Overhangs (Size & Loc) approx 50mm

External shading devices (Size & Loc) None

Internal shading devices (Type) Vertical Blinds

Internal shading devices (Location) Immediately behind glazing Wall Structure Cast-in-place Concrete w/ Cavity

Wall Insulation Within Cavity Roof Structure Built up roofing

Roof Insulation unknown

Roof Area 1105 sq. m

Ceiling Type Suspended

Ceiling Height 3.2 m

Thermal mass Heavyweight construction concrete and masonry, but NOT exposed.

HVAC System Design General Information: The basic system configuration features passive chilled ceilings and perimeter passive beams with night-time ice storage and some DX systems serving computer rooms and conference suites. Ventilation is provided mechanically via centralised AHU’s and heating is provided by perimeter radiators, all of which have TRV’s. The system utilises two GNA Axial Fan air-cooled water chillers using R717 (Ammonia) in combination with three ice storage vessels. The two packaged air-cooled chillers at night operate at low temperature to charge the ice store. While, during the day the chillers operate at a higher temperature in combination with the ice store to meet the cooling load of the building. The primary chilled circuit is a 5% Ethylene Glycol mix and operates at –1 Deg C at night and 5 Deg C during the day. The secondary circuits are all water only and served off the primary circuit by heat exchangers supplying at 7 Deg C

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to the AHU’s and 12 Deg C to the ceilings. Pumps serving the Primary, secondary, and AHU circuits are constant speed, while the pumps serving the ceiling circuits are VSD but on constant “set” control. Detailed Information:

Heating System

Boilers Hovel Gas-fired boilers 4x condensing with a rated output of 500kW each

Heating pumps (Constant temp) 1x pair rated @ 2.02kW each.

Heating pumps (Compensated temp) 4x pair rated @ 0.34, 0.14, 2.02, 1.35kW each pair.

DHW Pumps 1x pair rated @ 0.4kW each. Ventilation

Supply AHU Consisting of 22kW fan Filters, heating and cooling coils and heat recovery run-a-round coil system.

Return AHU Consisting of an 11kW fan and heat recovery run-a-round coil system.

Heat recovery pumps 1x pair rated @ 1.36kW each. Air Conditioning

General Chilled ceiling and beams with perimeter heating and night-time ice storage

2x GNA Axial fan air cooled chillers 4 stage units consisting of 2 compressors and 6 variable speed axial condenser fans with a total cooling capacity rated @ 195kW per chiller.

3x Calmac Ice storage vassals Total storage capacity of 1710 kWh

Primary Chilled water pumps 2x Pullen constant speed @ 10.8kW each

Secondary Chilled water pumps 2x Pullen constant speed @ 3.7kW each

AHU circuit chilled water pumps 2x Pullen constant speed @ 6.7 kW each

Chilled ceiling circuit pumps 2x Pullen variable speed @ 10.8 kW each

Passive chilled ceilings Trox - 49watts each with floe temp of 15 Deg C located within ceiling voids throughout building

Passive chilled beams Clima-Therm Trox rated at 191watts each with floe temp of 15 Deg C. Located within ceiling voids (Perimeter zones)

Refrigerant Type R717 (Ammonia)

Total Cooling Capacity 110kW

Cooling Capacity By area 50.1W/m2

Additional Information Additional separate DX split VRV system in IT / communication areas

HVAC Control Strategy *General The general control settings are shown in the detailed data below. Detailed data: HVAC Plant Control: Timed On/Off to match occupancy

Set Points 22 deg C +/- 1

Run times of HVAC plant As per occupancy

Identify HVAC zoning of building North South by floor

Details of planned maintenance Contract maintenance as per normal standards and documentation available on request.

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Cooling Performance General Monitoring showed that this building’s A/C system generally performs significantly better than the Good Practice benchmarks for this Office type. The performance of the overnight Ice Storage system can be clearly seen in the Cooling Energy Demand profiles shown below. The part-load profiles also show the amount of time that the system runs at, or near, its rated capacity. Detailed

Annual cooling energy consumption 17.1 kWh/m2 TFA

Monitored Cooling Energy Consumption

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20002001

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Site Energy Consumption Vs. National Benchmarks(Econ19 type 2 standard AC offices)

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benchmarks

Demand Profiles Chilled Ceiling Systems Average Summer Weekday

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Hours of operation 2453 hours per year Summary conclusions This case study illustrates the potential for very good cooling performance available from a Chilled Ceiling System with Ice Storage. However, this Case Study does not have a modelling component to compare with the demand actually measured, so we cannot be certain what loads were being met by the system.

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UK Case Study 3 UKCS3 Office Building

Dunn GN, Knight IP, Bleil de Souza C, Marsh AJ Welsh School of Architecture, Cardiff University Date: December 2006

The HVAC system installed is a 2-pipe Multi-Split DX system. This system has the possibility to free cool the spaces.

General Description of Case Study This case study presents the findings of a detailed monitoring study aimed at assessing the energy performance, and its potential for improvement, of a comfort cooling system installed in a UK office building. This speculative office building built in 1992 consists of a ground floor plus two stories of office only accommodation. The building was originally designed to be entirely naturally ventilated with a wet perimeter heating system controlled by thermostats (by floor and TRV’s) and supplied from a mains gas modular boiler. In 2000, the second floor was retrofitted with mechanical ventilation and a DX comfort cooling system. The mechanical ventilation system was designed to meet minimum ventilation requirements only and is loft mounted. The comfort cooling is provided by a 2-pipe (cooling only) Toshiba VRF multi-split DX system, consisting of 3 external condensers and internal ceiling mounted cassettes. The study was carried out by the Welsh School of Architecture (WSA) on the 2nd floor of the building only, and monitored the energy consumption of the whole AC system and mechanical ventilation system as well as the internal temperature of the open plan room at 15 minute intervals over a period of 11 months. The external weather data for the building was obtained at 5 minute intervals from a site about 2 miles away. From the monitoring study potential energy savings could be identified. The building was also simulated to analyse which were the highest contributors to the cooling loads in the AC system, indicating further energy saving options.

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Building Description General Building Data: Configuration Steel framed, side-day lit 3 storey office building

Layout Generally open plan office w/ some larger cellular spaces.

Number of floors Ground + 2

Floor area (Gross) 2348 sq. m

Floor area (Treated) 508 sq. m.

Refurbishment Fabric n/a

Refurbishment HVAC 2000

Refurbishment Lighting n/a

Refurbishment Other n/a

Space Activity Offices

Occupiers Business Type Property holdings

Type of tenancy Owner occupied

Occupant density 6.9m2 TFA/person

Tenancy Since 1992

Caretaker / Porter Occupiers Own

Heating System Gas fired wet radiators, whole building

Ventilation System Mechanical Ventilation, 2nd floor only w/ elec. Reheat

Cooling System DX Multi-Split, 2nd floor only

Econ 19 Category Type 3 (Air Conditioned Standard)

Building Category BRE OD4 Day-lit (Side) Open plan strip 1-4 storeys

Types of fuel used: Heating Gas

Cooling Electric

DHW Gas

HDD 1882 Yearly Total on 20 year average Building Envelope: Windows

Type Double

Total Area 289.4 sq. m

Type of glazing Clear Double

Percentage of glazing by facade 27% North

15% South

20% East

10% West

Glazing (U-value) 2.8 W/m2K

Window Reveals & Overhangs (Size & Loc.) 50mm approx

External shading devices (Size & Loc.) None

Internal shading devices (Type) Vertical blinds

Internal shading devices (Location) Behind glazing

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Wall Structure Brick & block cavity wall

Wall Insulation Rock wool in cavity Roof Structure Concrete tile, on pitched timber trusses Roof Insulation 200mm+ rockwool above ceiling

Roof Area 1190 sq. m

Ceiling Type Suspended

Ceiling Height (Typical) 2.6 m

Floor to Floor Height (Typical) n/a

Thermal mass n/a

HVAC System Design General Information: The comfort cooling system is a 2-pipe cooling only Toshiba VRF multi-split system, consisting of 3 external condensers and ceiling mounted cassettes. Ventilation is provided mechanically and was designed to meet minimum requirements only. It is loft mounted consisting of supply and return fan boxes, plus an electric heater battery. Controls for cooling are through the Trend BMS with a set-point of 24°C. The BMS locks out the cooling when heating is engaged. Detailed Information: Heating System

Boilers Not known

Heating pumps Not known

DHW Pumps Not known

Domestic hot water heater Not known Ventilation

General office areas Mechanically ventilated with openable windows

Stair well ventilation n/a Air Conditioning

General Toshiba VRF 2-pipe heating and cooling “change over” Multi-split DX system.

Exterior enclosure 3x Toshiba VRF super multi condensers, with refrigeration, distribution and controls integral to the condenser unit.

Ceiling void Internal ceiling cassettes - 7.1 kW cooling (7.9 heating) each

Loft space Supply AHU - Consisting of ducted axial fan, filter pack and elec. Heater battery.

Extract fan - Ducted axial fan.

Total Cooling Capacity 75kW

Cooling Capacity By area 147.6W/m2

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HVAC Control Strategy General The general strategy for the control of the HVAC system on the floor monitored is shown below in the detailed data section. The interlock with the heating was to ensure that simultaneous heating and cooling was not possible. However the building manager was believed to be proactive and, for example, would open the windows in appropriate weather to provide cooling, rather than switch on the A/C system. It is clear from the A/C system profile however that there was a background load of around 3kW being consumed by the A/C system even when cooling was not being provided. This only became clear in post-monitoring analysis so it is unclear how this load was created. The ECO’s aimed at Operation and Maintenance such as ECO O2.2 should be applicable here. Detailed data: HVAC Plant Control: Trend BEMS - Interlock heating and cooling

HVAC zoning By floor - By Condenser unit

Set Points Cooling 24 deg C

Run times of HVAC plant 8:00AM to 18:00 PM Monday to Friday (normal occupancy) (Plant off during cleaning hours); 9:00AM to 17:30 PM Saturdays.

Planned maintenance Contract maintenance as per normal standards and documentation available on request.

Performance Data General The following data illustrates the surveyed level of heat gains within the building during the period in which the AC system was monitored. Detailed Internal gains

Total Space Gains 47.1 W/m2 TFA, consisting of:

Occupancy 16.8 W/m2 TFA

Lighting 9.8 W/m2 TFA

Small Power 20.5 W/m2 TFA

Building Energy Performance *General Annual Building Energy Consumption 305.8 kWh/m2 TFA (Total Delivered) whole building

Gas 168.2 kWh/m2 TFA whole building

Electricity 137.6 kWh/m2 TFA whole building Detailed National benchmarks for delivered energy by building type

Actual building performance (% of benchmark)

Typical Practice - 404 kWh/m2 TFA 76%

Good Practice* – 225 kWh/m2 TFA 136%

* Set at 25th percentile based on 1998 national standards

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Cooling Performance *General from monitoring The monitoring shows this AC (comfort cooling) system seems to be very energy efficient, achieving an overall annual energy consumption/m2 for cooling which was substantially better than Best Practice at the time of the survey. However, a background load of 3kW for the A/C system seems to be present all the time, even when cooling is not being provided, and the modelling shown later will show that the actual COP achieved by the system against the modelled cooling load is very poor. The figures below show that for the vast majority of the time the system ran at less than 10% of its rated capacity – reflecting the unspecified 3kW load that was being consumed. Detailed

Annual cooling energy consumption 24.25 kWh/m2 TFA

Multi Split DX

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Fig1: Monthly cooling energy consumption

Site Energy Consumption Vs. National Benchmarks(Econ19 type 2 standard AC offices)

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Hours of operation 8674 hours per year General from simulation A simulation of the cooling demand was performed and the breakdown of the components that contribute to the cooling load were analysed in order to see which ECO’s could be used in the building to improve its energy performance for cooling. This modelling was also used to allow an overall summer COP to be calculated (from June to

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September), which in this case was 0.72. This value is substantially below that expected for a system of this type (1.05), and reflects the poor control of the system when cooling is not required. Had the 3 kW non-cooling base load been able to be removed, then the COP would have improved to 1.19 and the annual energy consumption of the A/C system would be almost 2.7 times lower than the actual value. Weather data: hourly data from the year of 2001/2002 was used. Meteorological station located in Cardiff. Simulation details: Energy Plus software was used to plot hourly breakdown of loads in the AC system and identify the main contributors to it. Breakdown of loads are defined based on a heat balance algorithm and are subdivided into Air heat balance breakdowns and Internal surfaces heat balance breakdowns. The air load breakdowns provide: total internal convective heat gains, infiltration sensible gains and losses, ventilation sensible gains and losses and convective loads from surfaces against cooling demand on the system. The internal surface load breakdowns provide: opaque surface inside face conduction gains and losses, total internal radiant heat gains, total internal visible heat gains, window heat gains and losses, radiant exchanges with other surfaces against convective loads from surfaces. Detailed from simulation

Annual cooling demand simulated 5,460 kWh

MONTHLY LOADS: Inside Surface Heat Balance Breakdown

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MONTHLY Total INTERNALVISIBLE Heat Gain (kWh)

MONTHLY CONVECTIVE heattransfer from SURFACES(kWh)

MONTHLY RADIANTEXCHANGES betweensurfaces (kWh)

Fig5: Inside surface heat balance breakdowns for whole year

MONTHLY LOADS: Air Heat Balance Breakdown

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Fig6: Air heat balance breakdowns for whole year

COOLING DESIGN DAY: Inside Surface Heat Balance Breakdown

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Fig8: Summer Design Day – Inside surface heat balance breakdowns

COOLING DESIGN DAY: Air Heat Balance Breakdown

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Fig7: Summer Design Day – Air heat balance breakdowns Hours of operation predicted for the A/C system from the modelling 813 hours per year

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From the breakdown analysis it can be seen that for loads acting directly in the air and therefore directly on the HVAC system, the highest contributors to the cooling demand are:

- The convective internal loads, i.e. the convective portion of the internal gains, followed by the convective heat transfer from surfaces. Surfaces are being heat up mainly by the internal gains and release the heat to the air through convection. As a consequence, the internal gains should be reduced in order to reduce the cooling demand. ECO’s related to “Other actions aimed at load reduction” (E4) should be applied. The most appropriate ones for this specific case study are listed in the Summary and conclusion section.

- Ventilation and infiltration tend to contribute positively to the cooling load as the

outside air temperature seems to be always lower than the inside air one. ECO’s related to “Ventilation/ Air movement/ Air leakage improvement” (E2) should be applied. The most appropriate ones for this specific case study are also listed in the Summary and conclusion section.

When analysing loads acting in the inside face of the surfaces and indirectly in the HVAC system, it can be seen that all the components increase the cooling load:

- The total internal radiant heat gains followed by the transmitted solar energy and the total visible heat gains will heat up the surfaces that will transfer heat to the air through convection. The negative values for conduction indicate a heat transfer from the inside surface to the mass which is being heat up by the internal gains together with the solar gains. The negative values for radiant heat exchange among surfaces will indicate the surfaces radiating heat back to the room. That reinforces the use of ECO’s related to “Other actions aimed at load reduction” (E4) together with the use of ECO’s related to “Solar gain reduction / daylight control improvement” (E1). The most appropriate ones for this specific case study are listed in the Summary and conclusion section.

Summary conclusions From the breakdown analysis it can be concluded that the following ECO’s could be used to help reduce the cooling energy demand in the building:

- ECO E4.5 – Replace electrical equipment with Energy Star or low consumption types.

- - ECO E4.9 – Move equipments (copiers, printers, etc.) to non conditioned zones.

Electrical equipment loads are the highest loads among the internal gains in this case, therefore any possibility to reduce the amount of energy they use and release should be considered. Most of the copiers and printers, etc in this case are in the conditioned zone, relocation to non conditioned areas could also be considered to reduce the cooling loads.

- ECO E4.7 – Modify lighting switches according to daylight contribution to different areas.

- ECO E4.8 – Introduce daylight/occupation sensors to operate lighting switches. Electrical lighting seems to be on all the time according to the survey and its contribution to the cooling demand is considerable.

- ECO E2.1 – Generate possibility to open/close windows and doors to match

climate. Ventilation should be used as much as possible as a free cooling source as the outside air temperature tends to be lower that the inside air temperature.

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- ECO E1.1 – Install window film or tinted glass.

- ECO E1.3 – Operate shutters, blinds, shades, screens or drapes. Solar control should be used to reduce the cooling loads, even though it is not the highest contributor to it.

- ECO O2.2 - Shut off A/C equipments when not needed.

The ancillary equipment to the A/C system is apparently consuming 3kW even when then system is providing no cooling. The relatively short period of time that this system provides cooling means that this load becomes a very significant component of the overall energy use, and reduces the overall COP dramatically.

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UK Case Study 4 UKCS4 Small Commercial Building

Dunn GN, Knight IP, Bleil de Souza C, Marsh AJ Welsh School of Architecture, Cardiff University Date: December 2006

DX splits were installed for comfort cooling. The system has roof mounted condensers and wall mounted slim-line cassettes.

General Description of Case Study This case study presents the findings of a detailed monitoring study aimed at assessing the energy performance, and its potential for improvement, of a comfort cooling system installed in a small commercial architectural practice operating as part of the Welsh School of Architecture (WSA), located in a historic building. Mitsubishi DX splits were installed for comfort cooling. The system has roof mounted condensors and wall mounted slim-line cassettes. Both units are supplied from the same panel, the supply to which is monitored. Controls are completely localised and independent, with the on/off and set-point temperature being controlled directly by the occupants when they feel a need for cooling. The building is heated by wet radiators serviced by centralised gas boilers. The heating is normally 24 hours-day throughout the heating season because of the heavy weight nature of the buildings historic fabric. The heating season is from 1st of October to end of April and the AC should be used only in the summer period. The study was carried out by the Welsh School of Architecture (WSA) only on the conditioned room of the building. The energy consumption of the whole AC system was monitored as well as the internal temperature of the room at 15 minute intervals over a period of 12 months. The external weather data for the building was obtained at 5 minute intervals from a meteorological station installed on the roof of this same building. From the monitoring study potential energy savings could be identified. The building was also simulated to analyse which were the highest contributors to the cooling loads in the AC system, indicating further energy saving options.

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Building Description General Building Data: Configuration A small office on the 2nd floor of an historic 5 storey (Lower

Ground, Ground +2, Mezzanines) civic building. Layout The building is based around a central courtyard, wit the

office itself consisting of the main office area and adjacent smaller storage and copier rooms.

Number of floors 5 whole building – only one room monitored Floor area (Gross) 89.5 m2 Floor area (Treated) 70.9 m2 Refurbishment Fabric 1995 Refurbishment HVAC 1995 Refurbishment Lighting 1995 Refurbishment Other 1997 Space Activity Small Commercial Office Occupiers Business Type Professional Services Type of tenancy Owner Occupied Occupant density 11.8m2 TFA/person Tenancy Since 1984 Caretaker / Porter Occupiers Own Heating System Perimeter Radiators Ventilation System Tempered mechanical ventilation Cooling System DX splits Econ 19 Category Type 3 - Air Conditioned Standard Building Category BRE n/a Types of fuel used: Heating Gas Cooling Electric DHW Electric HDD 1882 Yearly Total on 20 year average

Building Envelope: Windows

Type Double

Total Area 50.4 sq. m

Type of glazing Double with approx 10mm air void

Percentage of glazing by facade 48.6% roof, Skylights at a slope of approx 30 deg.

Glazing (u-value) 2.9 W/(m2.K) (Office areas)

Window Reveals & Overhangs (Size & Loc.) n/a

External shading devices (Size & Loc.) None Specific

Internal shading devices (Type) Horizontal (adjustable) Blinds

Internal shading devices (Location) Immediately Inside of Glazing

Wall Structure Stone outer and brick inner with cavity.

Wall Insulation None known Roof Structure Mixed slate tiles and skylights Roof Insulation Fibrous blanket type

Roof Area 103.7 m2

Ceiling Type Plaster

Ceiling Height (Typical) Varies approx. 6m (centre) to 3.5m (walls)

Floor to Floor Height (Typical) n/a

Thermal mass n/a

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HVAC System Design General Information: The office has a DX split comfort cooling system. The pair of single split DX system has roof mounted condensers and wall mounted slim-line cassettes. Each rated at 7.9kW cooling and 9.1kW Heating with a rate input power of 3.14kW each. These are reverse cycle machines, but are used for cooling only. In addition, the office is serviced by a perimeter radiator heating system and a mechanical ventilation system providing tempered fresh air, designed to meet minimum requirements only. Both are part of the main building system and were not monitored in this study. Controls for cooling are localised and independent with the on/off and set-point temperature being controlled directly by the occupants. Detailed Information: Heating System

Boilers Not known

Heating pumps Not known

DHW Pumps Not known

Domestic hot water heater Not known

Ventilation

General office areas Mixed mode – natural ventilation with CO2 controlled mechanical ventilation

Stair well ventilation Not known Air Conditioning

General 2 x Mitsubishi DX Split units

Exterior enclosure Roof mounted condensers

Total Cooling Capacity 15.8kW

Cooling Capacity By area 232.35 W/m2

HVAC Control Strategy *General The general strategy for the control of the HVAC system on the floor monitored is shown below in the detailed data section. Detailed data:

HVAC Plant Control:

The two split A/C systems are controlled by the room occupants on demand. They have control of the temperature of the system as well. There is no timeclock for the system, but the virtually individual control of the system means that the system is rarely left on.

HVAC zoning One room only

Set Points Various

Run times of HVAC plant Various, generally from 9:00AM to 17:00 PM Monday to Friday with rare weekend usage

Planned maintenance Contract maintenance per normal standards and documentation available on request.

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Performance Data General The following data illustrates the surveyed level of heat gains within the building during the period in which the AC system was monitored. Detailed Internal gains

Total Space Gains 42.5 W/m2 TFA, consisting of:

Occupancy 11.0 W/m2 TFA

Lighting 12.2 W/m2 TFA

Small Power 19.3 W/m2 TFA Building Energy Performance *General Annual Building Energy Consumption 154.95 kWh/m2 TFA (Total Delivered) whole building

Gas 42.84 kWh/m2 TFA whole building

Electricity 112.12 kWh/m2 TFA whole building Detailed National benchmarks for delivered energy by building type Actual building performance (% of benchmark)

Typical Practice - 404 kWh/m2 TFA 38.4%

Good Practice* – 225 kWh/m2 TFA 68.9% * Set at 25th percentile based on 1998 national standards Cooling Performance *General from monitoring The monitoring shows this AC (comfort cooling) system seems to be very energy efficient, achieving an overall annual energy consumption/m2 for cooling which was substantially better than Best Practice at the time of the survey. The modelling shown later will show that the actual COP achieved by the system against the modelled cooling load over the Summer period is at the low end @1.32 for the type of system being used, though this is not unexpected as the figures below show that for the vast majority of the time the system ran at less than 10% of its rated capacity

Annual cooling energy consumption – 31.08 kWh/m2 TFA

Project Office DX Splits Energy Consumption

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Cardiff University Project Office - Splits Average Weekday July 01

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Hours of operation 5921 hours per year General from simulation A simulation of the cooling demand was performed and the breakdown of the components that contribute to the cooling load were analysed in order to see which ECO’s could be used in the building to improve its energy performance for cooling. This modelling was also used to allow an overall summer COP to be calculated (from June to September), which in this case was 1.32. This value is within those expected for a system of this type (between 1.15 and 1.95). Weather data: hourly data from the year of 2001/2002 was used. Meteorological station located in Cardiff, on the top of the monitored building. Simulation details: Energy Plus software was used to plot hourly breakdown of loads in the AC system and identify the main contributors to it. Breakdown of loads are defined based on a heat balance algorithm and are subdivided into Air heat balance breakdowns and Internal surfaces heat balance breakdowns. The air load breakdowns provide: total internal convective heat gains, infiltration sensible gains and losses, ventilation sensible gains and losses and convective loads from surfaces against cooling demand on the system. The internal surface load breakdowns provide: opaque surface inside face conduction gains and losses, total internal radiant heat gains, total internal visible heat gains, window heat gains and losses, radiant exchanges with other surfaces against convective loads from surfaces.

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Detailed from simulation Annual cooling demand simulated

1935 kWh

MONTHLY LOADS: Air Heat Balance Breakdown

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Fig5: Air heat balance breakdowns for whole year

MONTHLY LOADS: Inside Surface Heat Balance Breakdown

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Fig6: Inside surface heat balance breakdowns for whole year

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Fig7: Summer Design Day – Air heat balance breakdowns

COOLING DESIGN DAY: Inside Surface Heat Balance Breakdown

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Fig8: Summer Design Day – Inside surface heat balance

breakdowns

Hours of operation predicted for the A/C system from the modelling 607 hours per year From the breakdown analysis it can be seen that for loads acting directly in the air and therefore directly on the HVAC system, the highest contributors to the cooling demand are:

- The convective heat transfer from surfaces, followed by the convective internal loads, i.e. the convective heat portion of the internal gains. Surfaces are being heat up mainly by the solar radiation transmitted through the skylights and release the heat to the air through convection. As a consequence, the solar gains should be reduced in order to reduce the cooling demand. ECOs related to “Solar Gain Reduction / Daylight Control Improvement” (E1) should be applied. The use of ECOs related to “Other Actions Aimed at Load Reduction” (E4) could also contribute to reducing the cooling demand. The most appropriate ones for this specific case study are listed in the Summary and conclusion section.

- Ventilation and infiltration tend to contribute to reducing the cooling load as the

outside air temperature seems to be always lower than the inside air one. ECOs related to “Ventilation/ Air movement/ Air leakage improvement” (E2) should be applied. The most appropriate ones for this specific case study are also listed in the Summary and conclusion section.

When analysing loads acting in the inside face of the surfaces and indirectly in the HVAC system, it can be seen that all the components increase the cooling load:

- Mainly the transmitted solar energy followed by the total internal radiant heat gains and the total visible heat gains will heat up the surfaces that will transfer

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heat to the air through convection. The negative values for conduction indicate a heat transfer from the inside surface to the mass which is being heat up by the internal gains together with the solar gains. The negative values for radiant heat exchange among surfaces will indicate the surfaces radiating heat back to the room. That reinforces the use of ECOs related to “Solar gain reduction / daylight control improvement” (E1) together with the use of ECOs related to “Other actions aimed at load reduction” (E4). The most appropriate ones for this specific case study are listed in the Summary and conclusion section.

Summary conclusions From the breakdown analysis it can be concluded that the following ECOs could be used to help reduce the cooling energy demand in the building:

- ECO E1.1 – Install window film or tinted glass. - ECO E1.3 – Operate shutters, blinds, shades, screens or drapes. - ECO E1.4 – Replace internal blinds with external systems.

Solar control should be used to reduce the cooling loads as this is the highest load in the room

- ECO E4.5 – Replace electrical equipment with Energy Star or low consumption

types. - ECO E4.9 – Move equipments (copiers, printers, etc.) to non conditioned zones.

Electrical equipment loads are the highest loads among the internal gains in this case, therefore any possibility to reduce the amount of energy they use and release should be considered. Most of the copiers and printers, etc in this case are in the conditioned zone, relocation to non conditioned areas could also be considered to reduce the cooling loads.

- ECO E4.7 – Modify lighting switches according to daylight contribution to different

areas. - ECO E4.8 – Introduce daylight/occupation sensors to operate lighting switches.

Electrical lighting seems to be on all the time according to the survey and its contribution to the cooling demand is considerable. With good top lighting from the rooflights the lighting in this section should be daylight-linked.

- ECO E2.1 – Generate possibility to open/close windows and doors to match

climate. Ventilation should be used as much as possible as a free cooling source as the outside air temperature tends to be lower that the inside air temperature.

- ECO P2 – Use of mechanical ventilation system to provide free cooling could be investigated.

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UK Case Study 5 UKCS5 Small Commercial Building

Dunn GN, Knight IP, Bleil de Souza C, Marsh AJ Welsh School of Architecture, Cardiff University Date: December 2006

The office has a DX split comfort cooling system with a roof mounted condenser and a 4-way ceiling mounted cassette.

General Description of Case Study This case study presents the findings of a detailed monitoring study aimed at assessing the energy performance, and its potential for improvement, of a comfort cooling system installed in a small administrative office, located in a historic building of Cardiff University. A single split DX system with roof-mounted condenser and ceiling mounted cassette was installed to provide comfort cooling. Controls are completely localised and independent, with the on/off and set-point temperature being controlled directly by the occupants whenever cooling is needed. Ventilation is provided through passive vents into the ceiling void, from which the ceiling cassette draws and conditions the supply air. Wet radiators serviced by centralised gas boilers heat the building 24hs a day throughout the heating season because of the heavy weight nature of the fabric. The heating season is from 1st of October to end of April and the AC should be used only in the summer period. The study was carried out by the Welsh School of Architecture (WSA) only on the conditioned room of the building. The energy consumption of the whole AC system was monitored as well as the internal temperature of the room at 15 minute intervals over a period of 12 months. The external weather data for the building was obtained at 5 minute intervals from a site about few miles away. From the monitoring study potential energy savings could be identified. The building was also simulated to analyse which were the highest contributors to the cooling loads in the AC system, indicating further energy saving options.

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Building Description General Building Data: Configuration A small office on the 2nd floor of an historic 5 storey civic

building. Layout Large masonry building, of cellular layout.

Number of floors 5 whole building – only one room monitored

Floor area (Gross) 34.3 m2 – monitored room.

Floor area (Treated) 34.3 m2

Refurbishment Fabric 1994

Refurbishment HVAC 1994

Refurbishment Lighting 1994

Refurbishment Other n/a

Space Activity Office

Occupiers Business Type Public sector institution

Type of tenancy Owner Occupied

Occupant density 11.4m2 TFA/person

Tenancy Since 1910

Caretaker / Porter Occupiers Own

Heating System Perimeter Radiators

Ventilation System Natural

Cooling System DX splits

Econ 19 Category Type 3 - Air Conditioned Standard

Building Category BRE n/a

Types of fuel used: Heating Gas

Cooling Electric

DHW Electric HDD 1882 Yearly Total on 20 year average

Building Envelope: Windows

Type Double

Total Area 2.64 m2

Type of glazing Double with approx 12mm air void

Percentage of glazing by facade 16.7%

Glazing (u-value) 2.9 W/m2K (Office areas)

Window Reveals & Overhangs (Size & Loc.) 150mm approx

External shading devices (Size & Loc.) None

Internal shading devices (Type) Vertical blinds

Internal shading devices (Location) Immediately Inside of Glazing

Wall Structure Stone outer and brick inner with cavity – 700mm total thickness

Wall Insulation None known Roof Structure n/a Roof Insulation n/a

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Roof Area as floor area

Ceiling Type Suspended

Ceiling Height (Typical) 2.75m

Floor to Floor Height (Typical) 3.2 m approx

Thermal mass n/a

HVAC System Design General Information: The office has a DX split comfort cooling system with a roof mounted condenser and a 4-way ceiling mounted cassette. Heating is provided via a separate perimeter radiator system and ventilation provided passively. Openable windows and passive vents in the ceiling plenum would supply fresh air to the room. Both heating and ventilation were not monitored in this study. Controls for cooling are localised and independent with the on/off and set-point temperature being controlled directly by the occupants. Detailed Information: Heating System

Boilers Not known

Heating pumps Not known

DHW Pumps Not known

Domestic hot water heater Not known Ventilation

General office areas Not known

Stair well ventilation Not known Air Conditioning

General 1x Carrier cooling only DX split

Total Cooling Capacity n/a

Cooling Capacity By area n/a

HVAC Control Strategy General The general strategy for the control of the HVAC system on the floor monitored is shown below in the detailed data section. Detailed data: HVAC Plant Control: Controls for cooling are localised and independent with the

on/off and set-point temperature being controlled directly by the occupants.

HVAC zoning 1 Unit serves entire office area

Set Points Various (which provides great uncertainties in the modelled performance)

Run times of HVAC plant Various, generally from 9:00AM to 17:00 PM Monday to Friday with rare weekend usage

Planned maintenance Contract maintenance per normal standards and documentation available on request.

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Performance Data General The following data illustrates the surveyed level of heat gains within the building during the period in which the AC system was monitored. Detailed Internal gains

Total Space Gains 37.5 W/m2 TFA, consisting of:

Occupancy 11.4 W/m2 TFA

Lighting 9.9 W/m2 TFA

Small Power 16.2 W/m2 TFA Building Energy Performance *General Annual Building Energy Consumption N/A

Gas N/A Electricity 153.1 kWh/m2 TFA whole building

Detailed National benchmarks for delivered energy by building type Actual building performance (% of benchmark)

Typical Practice - 404 kWh/m2 TFA N/A

Good Practice* – 225 kWh/m2 TFA N/A * Set at 25th percentile based on 1998 national standards Cooling Performance *General from monitoring The monitoring shows this AC (comfort cooling) system seems to be reasonably efficient, achieving an overall annual energy consumption/m2 for cooling which was between Good Practice and Typical Practice at the time of the survey. However, the modelling shown later will show that the actual COP achieved by the system against the modelled cooling load is very poor. The figures below show that for the vast majority of the time the system ran at less than 20% of its rated capacity

Annual cooling energy consumption – 46.9 kWh/m2 TFA

Cu South Bldg. - Split DX System Monthly Total kWh / m2

0.001.002.003.004.005.006.007.008.009.00

10.00

JanFeb

MarApr

MayJun

JulAug

SepOct

NovDec

kWh

/ m2

20012002

Fig1: Monthly cooling energy consumption

S ite E n e rg y C o n s u m p tio n V s . N a tio n a l B e n c h m a rk s(E c o n 1 9 ty p e 2 s ta n d a rd A C o ffic e s )

0 .0

1 0 .0

2 0 .0

3 0 .0

4 0 .0

5 0 .0

6 0 .0

7 0 .0

8 0 .0

9 0 .0

1 0 0 .0

An

nu

al k

Wh

/

S e rie s 1 4 4 .0 5 9 .2 4 7 9 .4 9 9 1 .0

G o o d P rac tic e 2 0 0 1 2 0 0 2 T yp ic a l

Fig2: Cooling energy consumption compared to national

benchmarks

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CU South Building DX Split Weekday Average July 2001

0

5

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15

20

25

30

0:00

1:15

2:30

3:45

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8:45

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0

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5Time of day

W/m

2 AverageSTDev +1STDev -1

Fig3: Cooling energy demand

System Part-Loading in CU South DX

0%

10%

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30%

40%

50%

60%

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80%

90%

1-5%5-1

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%

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%

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% of Full-Load

Tim

e

Fig4: Part-load profile

Hours of operation 6627 hours per year General from simulation A simulation of the cooling demand was performed and the breakdown of the components that contribute to the cooling load were analysed in order to see which ECO’s could be used in the building to improve its energy performance for cooling. This modelling was also used to allow an overall summer COP to be calculated (from June to September), which in this case was 0.09. This value is substantially below that expected for a system of this type (between 1.15 and 1.95), but used a modelled setpoint of 24°C which may not have been the setting in practice. However, even allowing for all the modelling uncertainties it is clear that this particular system did not perform as well as it might have done. Weather data: hourly data from the year of 2001/2002 was used. Meteorological station located in Cardiff. Simulation details: Energy Plus software was used to plot hourly breakdown of loads in the AC system and identify the main contributors to it. Breakdown of loads are defined based on a heat balance algorithm and are subdivided into Air heat balance breakdowns and Internal surfaces heat balance breakdowns. The air load breakdowns provide: total internal convective heat gains, infiltration sensible gains and losses, ventilation sensible gains and losses and convective loads from surfaces against cooling demand on the system. The internal surface load breakdowns provide: opaque surface inside face conduction gains and losses, total internal radiant heat gains, total internal visible heat gains, window heat gains and losses, radiant exchanges with other surfaces against convective loads from surfaces.

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Detailed from simulation Annual cooling demand simulated

93.7kWh

MONTHLY LOADS: Air Heat Balance Breakdown

-500.00

-400.00

-300.00

-200.00

-100.00

0.00

100.00

200.00

300.00

400.00

1 2 3 4 5 6 7 8 9 10 11 12

Months of the Year

Load

in kW

MONTHLY CONVECTIVEINTERNAL load (kWh)

MONTHLY CONVECTIVE heattransfer from SURFACES(kWh)MONTHLY INFILTRATION ofoutside air (kWh)

MONTHLY VENTILATION (kWh)

Fig5: Air heat balance breakdowns for whole year

MONTHLY LOADS: Inside Surface Heat Balance Breakdown

-500.00

-400.00

-300.00

-200.00

-100.00

0.00

100.00

200.00

300.00

400.00

1 2 3 4 5 6 7 8 9 10 11 12

Months of the Year

Load

in k

Wh

MONTHLY TRANSMITTEDSOLAR Energy (kWh)

MONTHLY Opaque SurfaceINSIDE FACE CONDUCTIONEnergy (kWh)

MONTHLY Total INTERNALRADIANT Heat Gain (kWh)

MONTHLY Total INTERNALVISIBLE Heat Gain (kWh)

MONTHLY CONVECTIVE heattransfer from SURFACES(kWh)

MONTHLY RADIANTEXCHANGES betweensurfaces (kWh)

Fig6: Inside surface heat balance breakdowns for whole year

COOLING DESIGN DAY: Air Heat Balance Breakdown

-1.50

-1.00

-0.50

0.00

0.50

1.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hours of the day

Load

in kW

h

CONVECTIVE INTERNALload (kWh)

CONVECTIVE heattransfer fromSURFACES (kWh)INFILTRATION of outsideair (kWh)

VENTILATION (kWh)

SYSTEM delivered load(kWh)

Fig7: Summer Design Day – Air heat balance breakdowns

COOLING DESIGN DAY: Inside Surface Heat Balance Breakdown

-1.50

-1.00

-0.50

0.00

0.50

1.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hours of the day

Load

in kW

h

TRANSMITTED SOLAR Energy(kWh)

Opaque Surface INSIDE FACECONDUCTION Energy (kWh)

Total INTERNAL RADIANT HeatGain (kWh)

Total INTERNAL VISIBLE HeatGain (kWh)

CONVECTIVE heat transferfrom SURFACES (kWh)

RADIANT EXCHANGES amongsurfaces (kWh)

Fig8: Summer Design Day – Inside surface heat balance

breakdowns

Hours of operation predicted for the A/C system from the modelling 305 hours per year From the breakdown analysis it can be seen that for loads acting directly in the air and therefore directly on the HVAC system, the highest contributors to the cooling demand are:

- The convective internal loads, i.e. the convective portion of the internal gains, followed by the convective heat transfer from surfaces. Surfaces are being heat up mainly by the internal gains and release the heat to the air through convection. As a consequence, the internal gains should be reduced in order to reduce the cooling demand. ECOs related to “Other actions aimed at load reduction” (E4) should be applied. The most appropriate ones for this specific case study are listed in the Summary and conclusion section.

- Ventilation and infiltration tend to contribute positively to the cooling load as the

outside air temperature seems to be always lower than the inside air one. ECOs related to “Ventilation/ Air movement/ Air leakage improvement” (E2) should be applied. The most appropriate ones for this specific case study are also listed in the Summary and conclusion section.

When analysing loads acting in the inside face of the surfaces and indirectly in the HVAC system, it can be seen that all the components increase the cooling load:

- The total internal radiant heat gains are the largest contributors to the cooling load, followed by the transmitted solar energy and the total visible heat gains. These gains will heat up the surfaces in the room that in turn will transfer heat to

163

the air through convection. The negative values for conduction indicate a heat transfer from the inside surface of the materials in the room to their mass, due to their being heated up by the internal gains together with the solar gains. The negative values for radiant heat exchange among the surfaces indicate that the surfaces are radiating heat back to the room. That reinforces the use of ECO’s related to “Other actions aimed at load reduction” (E4) together with the use of ECO’s related to “Solar gain reduction / daylight control improvement” (E1). The most appropriate ones for this specific case study are listed in the Summary and conclusion section.

Summary conclusions From the breakdown analysis it can be concluded that the following ECOs could be used to help reduce the cooling energy demand in the building:

- ECO E4.5 – Replace electrical equipment with Energy Star or low consumption types.

- ECO E4.9 – Move equipments (copiers, printers, etc.) to non conditioned zones. Electrical equipment loads are the highest loads among the internal gains in this case, therefore any possibility to reduce the amount of energy they use and release should be considered. Most of the copiers and printers, etc in this case are in the conditioned zone, relocation to non conditioned areas could also be considered to reduce the cooling loads.

- ECO E4.7 – Modify lighting switches according to daylight contribution to different areas.

- ECO E4.8 – Introduce daylight/occupation sensors to operate lighting switches. Electrical lighting seems to be on all the time according to the survey and its contribution to the cooling demand is considerable.

- ECO E2.1 – Generate possibility to open/close windows and doors to match

climate. Ventilation should be used as much as possible as a free cooling source as the outside air temperature tends to be lower that the inside air temperature.

- ECO E1.1 – Install window film or tinted glass. - ECO E1.3 – Operate shutters, blinds, shades, screens or drapes.

Solar control should be used to reduce the cooling loads, even not being the highest contributor to it.

164

UK Case Study 6 UKCS6 Office Building

Dunn GN, Knight IP, Bleil de Souza C, Marsh AJ Welsh School of Architecture, Cardiff University Date: December 2006

This area is serviced by VRF indoor units, ceiling mounted, from external condensers on a 2-pipe heating and cooling “change over” only basis. The supply AHU consist of an in-duct axial fan, filter pack and electric heater battery. The system has plenum return ventilation with ducted supply and partial recirculation in the fan-coil units.

General Description of Case Study This case study presents the findings of a detailed monitoring study aimed at assessing the energy performance, and its potential for improvement, of a comfort cooling system installed in a light industrial building on a small rural estate near Oxford, which has been adapted to contain a variety of offices, production centre, warehousing and a call centre (not intensively used). The conditioned area consists of a large open plan office, 3 cellular spaces of executive offices, a conference room and a production area room. This area is serviced by 12 VRF indoor units, ceiling mounted, from 3 external condensers on a 2-pipe heating and cooling “change over” only basis. Controls are timed on and off based on the working day of 8.00am to 6.00pm, Monday to Friday with a setpoint of 23°C. The area is mechanically ventilated and it is assumed that in the office areas supply air is delivered through the plenum via the VRF units. Heating is provided by gas fired radiators The study was carried out by the Welsh School of Architecture (WSA) only on the conditioned part of the building. The energy consumption of the whole AC system was monitored as well as the internal temperature of the room at 15 minute intervals over a period of 12 months. The external weather data for the building was obtained at 5 minute intervals from London meteorological station. From the monitoring study potential energy savings could be identified. The building was also simulated to analyse which were the highest contributors to the cooling loads in the AC system, indicating further energy saving options.

165

Building Description General Building Data: Configuration Large steel framed light industrial building, predominantly

artificially lit. Layout Generally open plan office w/ some larger cellular spaces.

Number of floors Ground + mezzanine

Floor area (Gross) n/a whole building

Floor area (Treated) 1202.2 m2

Refurbishment Fabric n/a

Refurbishment HVAC 2000

Refurbishment Lighting n/a

Refurbishment Other n/a

Space Activity Offices, Small Call centre (not intensively used), document archive.

Occupiers Business Type Marketing

Type of tenancy Rented

Occupant density 18.8 m2 TFA/person

Tenancy Since 1999

Caretaker / Porter Occupiers Own

Heating System Gas fired wet radiators

Ventilation System Mechanical Ventilation

Cooling System DX Multi-Split

Econ 19 Category Type 3 (Air Conditioned Standard)

Building Category BRE HA Artificial-lit Hall

Types of fuel used: Heating Gas

Cooling Electric

DHW Electric HDD 1977 Yearly Total on 20 year average

Building Envelope: Windows

Type None

Total Area n/a

Type of glazing n/a

Percentage of glazing by facade 0

Glazing (u-value) n/a

Window Reveals & Overhangs (Size & Loc.) n/a

External shading devices (Size & Loc.) n/a

Internal shading devices (Type) n/a

Internal shading devices (Location) n/a

Wall Structure Composite metal cladding system on steel frame and purlings.

Wall Insulation Integral to cladding system Roof Structure Composite metal, low pitch of aprox 15 deg and light colour. Roof Insulation Integral to cladding roofing system

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Roof Area n/a part of larger building

Ceiling Type Suspended

Ceiling Height (Typical) 3.5 m

Floor to Floor Height (Typical) n/a

Thermal mass n/a

HVAC System Design General Information: The conditioned area has 12 Toshiba VRF indoor units, ceiling mounted from 3 external condensers running 407c refrigerants on a 2-pipe heating and cooling “change over” multi-split DX system. The supply AHU consist of an in-duct axial fan, filter pack and electric heater battery. The system has a plenum return ventilation with ducted supply and partial recirculation in the fancoil units. All refrigeration, distribution and controls are integral to the condenser unit. Detailed Information: Heating System

Boilers Not known

Heating pumps Not known

DHW Pumps Not known

Domestic hot water heater Not known Ventilation

General office areas Not known

Stair well ventilation Not known Air Conditioning

General Toshiba VRF 2-pipe heating and cooling “change over” Multi-split DX system.

Exterior enclosure 3x Toshiba VRF super multi condensers

Ceiling void 6x Internal ceiling cassettes (ground floor), 9x Internal ceiling cassettes (first floor)

Total Cooling Capacity 75kW

Cooling Capacity By area 76.7 W/m2 HVAC Control Strategy *General The general strategy for the control of the HVAC system on the floor monitored is shown below in the detailed data section. Detailed data: HVAC Plant Control: Timed On/Off to match occupancy

HVAC zoning By Condenser unit

Set Points 23 deg C

Run times of HVAC plant Generally from 9:00AM to 17:00 PM Monday to Saturday

Planned maintenance Contract maintenance as per normal standards and documentation available on request.

167

Performance Data General The following data illustrates the surveyed level of heat gains within the building during the period in which the AC system was monitored. Detailed Internal gains

Total Space Gains 28.1 W/m2 TFA, consisting of:

Occupancy 6.1 W/m2 TFA

Lighting 9.1 W/m2 TFA

Small Power 12.9 W/m2 TFA Building Energy Performance General Annual Building Energy Consumption n/a

Gas n/a Electricity n/a

Detailed National benchmarks for delivered energy by building type Actual building performance (% of benchmark)

Typical Practice - 404 kWh/m2 TFA n/a

Good Practice* – 225 kWh/m2 TFA n/a * Set at 25th percentile based on 1998 national standards Cooling Performance General from monitoring The monitoring shows this AC (comfort cooling) system seems to be reasonably energy efficient, achieving an overall annual energy consumption/m2 for cooling which was between Good Practice and Typical Practice at the time of the survey. However, the modelling shown later will show that the actual COP achieved by the system against the modelled cooling load is very poor. The figures below show that for the vast majority of the time the system ran at less than 25% of its rated capacity. It should also be noted that the system ran 24 hours a day despite the hours of operation of the building being recorded as 09:00 to 17:00 daily during the working week. The system also ran at weekends when there was little or no recorded occupancy. This suggests it might be appropriate to consider Operation and Maintenance ECO’s e.g. ECO O2.2.

168

Annual cooling energy consumption – 46.5 kWh/m2 TFA

Multi-split (2-pipeVRF) System Total Monthly kWh / m2

0123456789

JanFeb

MarApr

MayJun

JulAug

SepOct

NovDec

kWh

/ m2

Fig1: Monthly cooling energy consumption

S ite E n e rg y C o n s u m p tio n V s . N a tio n a l B e n c h m a rk s(E c o n 1 9 ty p e 2 s ta n d a rd A C o ffic e s )

0 .0

1 0 .0

2 0 .0

3 0 .0

4 0 .0

5 0 .0

6 0 .0

7 0 .0

8 0 .0

9 0 .0

1 0 0 .0

An

nu

al k

Wh

/

S e r ie s 1 4 4 .0 5 7 .1 8 9 1 .0

G o o d P ra c ti c e 2 0 0 1 T yp ic a l

Fig2: Cooling energy consumption compared to national

benchmarks

Average Weekday Energy ProfileJuly 2001

0

5

10

15

20

25

30

00:00 02:00 03:59 05:59 07:59 09:59 11:59 13:59 15:59 17:59 19:59 21:59 23:59

Time of Day

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2

Average STDev+1 STDev-1

Fig3: Cooling energy demand

System Part-Load Profile 2001 DX Multi-Split

0%

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Tim

e

Fig4: Part-load profile

Hours of operation 8744 hours per year

General from simulation A simulation of the cooling demand was performed and the breakdown of the components that contribute to the cooling load were analysed in order to see which ECO’s could be used in the building to improve its energy performance for cooling. This modelling was also used to allow an overall summer COP to be calculated (from June to September), which in this case was 0.48. This value is substantially below that expected for a system of this type (1.05). Weather data: hourly data from the year of 2001 used. Meteorological station located in London. Simulation details: Energy Plus software was used to plot hourly breakdown of loads in the AC system and identify the main contributors to it. Breakdown of loads are defined based on a heat balance algorithm and are subdivided into Air heat balance breakdowns and Internal surfaces heat balance breakdowns. The air load breakdowns provide: total internal convective heat gains, infiltration sensible gains and losses, ventilation sensible gains and losses and convective loads from surfaces against cooling demand on the system.

169

The internal surface load breakdowns provide: opaque surface inside face conduction gains and losses, total internal radiant heat gains, total internal visible heat gains, window heat gains and losses, radiant exchanges with other surfaces against convective loads from surfaces. Detailed from simulation

Annual cooling demand simulated 13284.1 kWh

MONTHLY LOADS: Air Heat Balance Breakdown

-6000.00

-5000.00

-4000.00

-3000.00

-2000.00

-1000.00

0.00

1000.00

2000.00

3000.00

4000.00

1 2 3 4 5 6 7 8 9 10 11 12

Months of the Year

Load

in kW

MONTHLY CONVECTIVEINTERNAL load (kWh)

MONTHLY CONVECTIVE heattransfer from SURFACES(kWh)MONTHLY INFILTRATION ofoutside air (kWh)

MONTHLY VENTILATION (kWh)

Fig5: Air heat balance breakdowns for whole year

MONTHLY LOADS: Inside Surface Heat Balance Breakdown

-6000.00

-5000.00

-4000.00

-3000.00

-2000.00

-1000.00

0.00

1000.00

2000.00

3000.00

4000.00

1 2 3 4 5 6 7 8 9 10 11 12

Months of the YearLo

ad in

kWh

MONTHLY TRANSMITTEDSOLAR Energy (kWh)

MONTHLY Opaque SurfaceINSIDE FACE CONDUCTIONEnergy (kWh)

MONTHLY Total INTERNALRADIANT Heat Gain (kWh)

MONTHLY Total INTERNALVISIBLE Heat Gain (kWh)

MONTHLY CONVECTIVE heattransfer from SURFACES(kWh)

MONTHLY RADIANTEXCHANGES betweensurfaces (kWh)

Fig6: Inside surface heat balance breakdowns for whole year

COOLING DESIGN DAY: Air Heat Balance Breakdown

-40.00

-30.00

-20.00

-10.00

0.00

10.00

20.00

30.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hours of the day

Load

in k

Wh

CONVECTIVE INTERNALload (kWh)

CONVECTIVE heattransfer fromSURFACES (kWh)INFILTRATION of outsideair (kWh)

VENTILATION (kWh)

SYSTEM delivered load(kWh)

Fig7: Summer Design Day – Air heat balance breakdowns

COOLING DESIGN DAY: Inside Surface Heat Balance Breakdown

-40.00

-30.00

-20.00

-10.00

0.00

10.00

20.00

30.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hours of the day

Load

in kW

h

TRANSMITTED SOLAR Energy(kWh)

Opaque Surface INSIDE FACECONDUCTION Energy (kWh)

Total INTERNAL RADIANT HeatGain (kWh)

Total INTERNAL VISIBLE HeatGain (kWh)

CONVECTIVE heat transferfrom SURFACES (kWh)

RADIANT EXCHANGES amongsurfaces (kWh)

Fig8: Summer Design Day – Inside surface heat balance

breakdowns

Hours of operation predicted for the A/C system from the modelling 812 hours per year

From the breakdown analysis it can be seen that for loads acting directly in the air and therefore directly on the HVAC system, the highest contributors to the cooling demand are:

- The convective internal loads, i.e. the convective portion of the internal gains, followed by the convective heat transfer from surfaces. Surfaces are being heat up mainly by the internal gains and release the heat to the air through convection. As a consequence, the internal gains should be reduced in order to reduce the cooling demand. ECOs related to “Other actions aimed at load reduction” (E4) should be applied. The most appropriate ones for this specific case study are listed in the Summary and conclusion section.

- Ventilation and infiltration tend to contribute positively to the cooling load as a

whole because during the night the outside air temperature is lower than the inside one. However, during the day they tend to increase the cooling load as the outside air temperature seems to be most of the time equal or higher than the inside air one. ECOs related to “Ventilation/ Air movement/ Air leakage improvement” (E2) should be applied. The most appropriate ones for this specific case study are also listed in the Summary and conclusion section.

170

When analysing loads acting in the inside face of the surfaces and indirectly in the HVAC system, it can be seen that all the components increase the cooling load:

- The total internal radiant heat gains followed by the total visible heat gains will heat up the surfaces that will transfer heat to the air through convection. The negative values for conduction in the morning indicate a heat transfer from the inside surface of the material to its mass, as the surface is being heated up by the internal gains of the space. The positive values for conduction in the afternoon indicate a heat transfer from the mass to the inside surface which contributes to an increase in the cooling loads due to convective heat transfer from the surface to the air.

- This observation reinforces the use of ECOs related to “Other actions aimed at load reduction” (E4). The most appropriate ones for this specific case study are listed in the Summary and conclusion section.

Summary conclusions From the breakdown analysis it can be concluded that the following ECOs could be used to help reduce the cooling energy demand in the building:

- ECO E4.5 – Replace electrical equipment with Energy Star or low consumption types.

- ECO E4.9 – Move equipments (copiers, printers, etc.) to non conditioned zones. Electrical equipment loads are the highest loads among the internal gains in this case, therefore any possibility to reduce the amount of energy they use and release should be considered. Most of the copiers and printers, etc in this case are in the conditioned zone, relocation to non conditioned areas could also be considered to reduce the cooling loads.

- ECO E4.7 – Modify lighting switches according to daylight contribution to different areas.

- ECO E4.8 – Introduce daylight/occupation sensors to operate lighting switches. Electrical lighting seems to be on all the time according to the survey and its contribution to the cooling demand is considerable.

- ECO E2.1 – Generate possibility to open/close windows and doors to match

climate. - ECO E2.6 – Generate possibility of night time over ventilation.

Ventilation should be used as much as possible as a free cooling source during the night as the outside air temperature tends to be lower that the inside air temperature. However it needs to be controlled during the day in order to not contribute to an increase in the cooling loads.

- ECO O2.2 - Shut off A/C equipments when not needed. The A/C system is providing cooling even during periods of no occupancy. This is a relatively long period of time compared to the occupied period, and means that this load becomes a very significant component of the overall energy use, and reduces the overall COP dramatically.

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UK Case Study 7 UKCS7 Office Building

Dunn GN, Knight IP, Bleil de Souza C, Marsh AJ Welsh School of Architecture, Cardiff University Date: December 2006

The conditioned area has a 2-pipe fan-coil system with the electrical reheat, supplied by two reverse cycle air-cooled chillers. The indoor units are a 2-pipe ceiling mounted cassettes with multi-speed fans and electrical reheat in the perimeter units.

General Description of Case Study This case study presents the findings of a detailed monitoring study aimed at assessing the energy performance, and its potential for improvement, of a comfort cooling system installed in the ground floor of a 2 storey office block. The conditioned area consists of open plans and cellular office rooms, meeting rooms, training rooms and a reception. This area is serviced by a 2-pipe fancoil system with Carrier Aquasnaps package chillers with CCN control system based on the working day of 7.00am to 8.00pm, Monday to Friday with a setpoint of 24°C. The whole building is mechanically ventilated with the AHU located at the roof top plant room. The study was carried out by the Welsh School of Architecture (WSA) on the two floors of the building separately. The energy consumption of the ground floor AC system was monitored as well as the internal temperature of a room at 15 minute intervals over a period of 12 months. The external weather data for the building was obtained at 5 minute intervals from London meteorological station. From the monitoring study potential energy savings could be identified. The building was also simulated to analyse which were the highest contributors to the cooling loads in the AC system, indicating further energy saving options.

Building Description General Building Data: Configuration A 2 storey (Ground + 1) speculative built office building

Layout Mixture of open plan and cellular, including a number of larger training and conference rooms.

Number of floors Ground +1 (only ground being analysed here)

Floor area (Gross) 812.7 m2

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Floor area (Treated) 705.3 m2

Refurbishment Fabric none

Refurbishment HVAC 2000

Refurbishment Lighting none

Refurbishment Other none

Space Activity Corporate Offices & Training rooms

Occupiers Business Type Multi-national corporation

Type of tenancy Tenant

Occupant density 14.1 m2 TFA/person

Tenancy Since 2000

Caretaker / Porter Occupiers Own

Heating System Centralised Heat-pumps & Fancoils w/ elec. re-heat

Ventilation System Tempered Mechanical ventilation

Cooling System Centralised liquid chiller & Fancoils, additional packaged DX in Common rooms

Econ 19 Category Type 3 - Air Conditioned Standard

Building Category BRE OD4 - Daylit Open Plan Strip 1 to 4 Storeys

Types of fuel used: Heating Electric

Cooling Electric

DHW Gas HDD 1977 Yearly Total on 20 year average

Building Envelope: Windows

Type Double

Total Area 92.9 sq. m

Type of glazing Double w/ aprox 12mm air void, aluminium frames and gray tint.

Percentage of glazing by facade

12.5% North East 21.8 % North West 21.8 % South East 26.3 % South west

Glazing (u-value) 2.8 W/m2K (3.4 w/m2 w/ metal frames)

Window Reveals & Overhangs (Size & Loc.) Reveals <25mm / Eves none

External shading devices (Size & Loc.) None Specific

Internal shading devices (Type) Vertical Blinds

Internal shading devices (Location) Immediately Inside of Glazing Wall Structure Brick & block cavity Wall Insulation fibrous cavity insulation per 1999 standards

Roof Structure Wood framed (Eng. Trusses), w/ OSB sheathing, felt and tiles

Roof Insulation Fibrous blanket type

Roof Area n/a

Ceiling Type Suspended

Ceiling Height (Typical) aprox 2.75 m

Floor to Floor Height (Typical) aprox 3.25 m

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Thermal mass n/a

HVAC System Design General Information: The conditioned area has a 2-pipe fancoil system with the electrical reheat, supplied by two Carrier Aquasnap air-cooled reverse cycle air-cooled chillers. Distribution pumps are integrated into the chiller. The indoor units are a 2-pipe ceiling mounted cassettes with multi-speed fans and electrical reheat in the perimeter units. The control system is a CCN type. Detailed Information: Heating System

Boilers n/a

Heating pumps n/a

DHW Pumps n/a

Domestic hot water heater Centralised system for the entire building using instantaneous gas boilers

Ventilation

General office areas The entire building is mechanically ventilated with a 2-duct supply and return system. The air handling unit is located in the roof top plant room.

Air Conditioning

General

A 2-pipe 'Change-over' fancoil system with the electrical reheat, supplied by two Carrier Aquasnap air-cooled reverse cycle air-cooled chillers. Distribution pumps are integrated into the chiller. The system uses R-407c refrigerant and CCN control system. There are 2 x Carrier Aquasnap 30RH050 packaged air cooled reverse cycle heat pumps, with 2 hermetic scroll compressors in each unit. Each unit is rated at 45kW cooling 48 kW heating with a nominal input of 19.2 kW. The package includes all heat rejection fans and distribution pumps.

Ceiling void The ceiling voids are used as the supply plenum for the mechanical ventilation system.

Total Cooling Capacity 90 kW

Cooling Capacity By area 64.97 W/m2 HVAC Control Strategy *General The general strategy for the control of the HVAC system on the floor monitored is shown below in the detailed data section. Detailed data: HVAC Plant Control: Carrier CCN system, Optimised on external temperature.

HVAC zoning 2 per floor north & south (Half floor), each chiller / heat-pump serves a single zone as a standalone system

Set Points 18°C heating and 24°C cooling

Run times of HVAC plant Generally from 7:00AM to 8:00 PM Monday to Friday

Planned maintenance Contract maintenance per normal standards and documentation available on request.

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Performance Data General The following data illustrates the surveyed level of heat gains within the building during the period in which the AC system was monitored. Detailed Internal gains

Total Space Gains 34.46 W/m2 TFA, consisting of:

Occupancy 7.5 W/m2 TFA

Lighting 15.0 W/m2 TFA

Small Power 11.96 W/m2 TFA Building Energy Performance *General Annual Building Energy Consumption 252.6 kWh/m2 (electricity for the whole building)

Gas n/a Electricity 252.6 kWh/m2

Detailed National benchmarks for delivered energy by building type Actual building performance (% of benchmark)

Typical Practice - 404 kWh/m2 TFA 62.5%

Good Practice* – 225 kWh/m2 TFA 112% * Set at 25th percentile based on 1998 national standards Cooling Performance *General from monitoring The monitoring shows this AC (comfort cooling) system seems to be relatively energy efficient, achieving an overall annual energy consumption/m2 for cooling which was better than Typical Best Practice at the time of the survey but not as good as the Good Best Practice. The modelling shown later will confirm that the actual COP achieved by the system against the modelled cooling load is within an acceptable range for the type of system being used. Detailed from monitoring

Annual cooling energy consumption –87.14kWh/m2 TFA

Energy ConsumptionCarrier Aquasnap Fancoil System

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

jan feb mar apr may jun jul aug sep oct nov dec

kWh/

m2 2000

20012002

Fig1: Monthly cooling energy consumption

S ite E n erg y C o nsu m p tio n V s . N a tio na l B en ch m arks(E co n 19 typ e 2 s tan d ard AC o ffices )

0 .0

50.0

100 .0

150 .0

200 .0

250 .0

300 .0

An

nu

al k

Wh

/m

S eries1 129 .0 126 .0 9 83 .19 249 .0

Good P ractice 2001 2002 Typ ica l

Fig2: Cooling energy consumption compared to national

benchmarks

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Chiller+ Fancoils Average Weekday July 01

0

10

20

30

40

50

60

70

00:00

01:15

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03:45

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20:00

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W /

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STDev+1

STDev-1

Fig3: Cooling energy demand

System Part-Loading in 2001 Chiller (FCU)

0%

5%

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20%

25%

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35%

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0%

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e

Fig4: Part-load profile

Hours of operation 8605 hours per year

General from simulation A simulation of the cooling demand was performed and the breakdown of the components that contribute to the cooling load were analysed in order to see which ECO’s could be used in the building to improve its energy performance for cooling. This modelling was also used to allow an overall summer COP to be calculated (from June to September), which in this case was 0.5. This value is within expected values for a system of this type (between 0.3 and 1.6) but is much lower than was expected from a state-of-the-art system. The reason for this was the apparent 24 hour operation of the systems when not required. Weather data: hourly data from the year of 2001 used. Meteorological station located in London. Simulation details: Energy Plus software was used to plot hourly breakdown of loads in the AC system and identify the main contributors to it. Breakdown of loads are defined based on a heat balance algorithm and are subdivided into Air heat balance breakdowns and Internal surfaces heat balance breakdowns. The air load breakdowns provide: total internal convective heat gains, infiltration sensible gains and losses, ventilation sensible gains and losses and convective loads from surfaces against cooling demand on the system. The internal surface load breakdowns provide: opaque surface inside face conduction gains and losses, total internal radiant heat gains, total internal visible heat gains, window heat gains and losses, radiant exchanges with other surfaces against convective loads from surfaces.

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Detailed from simulation Annual cooling demand simulated

13641.7kWh

MONTHLY LOADS: Air Heat Balance Breakdown

-6000.00

-4000.00

-2000.00

0.00

2000.00

4000.00

6000.00

1 2 3 4 5 6 7 8 9 10 11 12

Months of the Year

Load

in kW

h

MONT HLY CONVECT IVEINT ERNAL load (kWh)

MONT HLY CONVECT IVE heattransfer from SURFACES(kWh)MONT HLY INFILT RAT ION ofoutside air (kWh)

MONT HLY VENT ILAT ION(kWh)

Fig5: Air heat balance breakdowns for whole year

MONTHLY LOADS: Inside Surface Heat Balance Breakdow n

-6000.00

-5000.00

-4000.00

-3000.00

-2000.00

-1000.00

0.00

1000.00

2000.00

3000.00

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1 2 3 4 5 6 7 8 9 10 11 12

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Load

in kW

h

MONT HLY T RANSMIT T EDSOLAR Energy (kWh)

MONT HLY Opaque SurfaceINSIDE FACE CONDUCT IONEnergy (kWh)

MONT HLY T otal INT ERNALRADIANT Heat Gain (kWh)

MONT HLY T otal INT ERNALVISIBLE Heat Gain (kWh)

MONT HLY CONVECT IVE heattransfer from SURFACES(kWh)

MONT HLY RADIANTEX CHANGES between surfaces(kWh)

Fig6: Inside surface heat balance breakdowns for whole year

COOLING DESIGN DAY: Air Heat Balance Breakdow n

-40.00-35.00-30.00-25.00-20.00-15.00-10.00-5.000.005.00

10.0015.0020.0025.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hours of the day

Load

in kW

h

CONVECT IVE INT ERNALload (kWh)

CONVECT IVE heattransfer from SURFACES(kWh)INFILT RAT ION of outsideair (kWh)

VENT ILAT ION (kWh)

SYST EM delivered load(kWh)

Fig7: Summer Design Day – Air heat balance breakdowns

COOLING DESIGN DAY: Inside Surface Heat Balance Breakdow n

-40.00

-35.00

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

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10.00

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Load

in k

Wh

T RANSMIT T ED SOLAREnergy (kWh)

Opaque Surface INSIDE FACECONDUCT ION Energy (kWh)

T otal INT ERNAL RADIANTHeat Gain (kWh)

T otal INT ERNAL VISIBLE HeatGain (kWh)

CONVECT IVE heat transferfrom SURFACES (kWh)

RADIANT EXCHANGES amongsurfaces (kWh)

Fig8: Summer Design Day – Inside surface heat balance

breakdowns

Hours of operation predicted for the A/C system from the modelling 1078 hours per year

From the breakdown analysis it can be seen that for loads acting directly in the air and therefore directly on the HVAC system, the highest contributors to the cooling demand are:

- The convective heat transfer from surfaces followed by the convective internal loads, i.e. the convective portion of the internal gains. Surfaces are being heat up mainly by the internal gains followed by the solar gains and release the heat to the air through convection. As a consequence, the internal gains should be reduced together with the solar gains in order to reduce the cooling demand. ECOs related to “Other actions aimed at load reduction” (E4) should be applied together with ECOs related to “Solar Gain Reduction / Daylight Control Improvement” (E1). The most appropriate ones for this specific case study are listed in the Summary and conclusion section.

- Ventilation and infiltration tend to contribute positively to the cooling load as a

whole because during the night the outside air temperature is lower than the inside one. However, during the day they tend to increase the cooling load as the outside air temperature seems to be most of the time equal or higher than the inside air one. ECOs related to “Ventilation/ Air movement/ Air leakage improvement” (E2) should be applied. The most appropriate ones for this specific case study are also listed in the Summary and conclusion section.

When analysing loads acting in the inside face of the surfaces and indirectly in the HVAC system, it can be seen that all the components increase the cooling load:

177

- The internal radiant heat gains followed by the transmitted solar gains and the

total visible heat gains will heat up the surfaces that will transfer heat to the air through convection. The negative values for conduction indicate a heat transfer from the mass to the inside surface which is being heat up by the solar gains together with the internal gains. That reinforces the use of ECOs related to “Solar gain reduction / daylight control improvement” (E1) together with the use of ECOs related to “Other actions aimed at load reduction” (E4). The most appropriate ones for this specific case study are listed in the Summary and conclusion section.

Summary conclusions From the breakdown analysis it can be concluded that the following ECOs could be used to help reduce the cooling energy demand in the building:

- ECO E4.7 – Modify lighting switches according to daylight contribution to different

areas. - ECO E4.8 – Introduce daylight/occupation sensors to operate lighting switches.

Electrical lighting seems to be on all the time according to the survey and its contribution to the cooling demand is considerable.

- ECO E4.5 – Replace electrical equipment with Energy Star or low consumption

types. - ECO E4.9 – Move equipments (copiers, printers, etc.) to non conditioned zones.

Electrical equipment loads are the highest loads among the internal gains in this case, therefore any possibility to reduce the amount of energy they use and release should be considered. Most of the copiers and printers, etc in this case are in the conditioned zone, relocation to non conditioned areas could also be considered to reduce the cooling loads.

- ECO E1.1 – Install window film or tinted glass. - ECO E1.3 – Operate shutters, blinds, shades, screens or drapes. - ECO E1.4 – Replace internal blinds with external systems.

Solar control should be used to reduce the cooling loads as this is the highest load in the room

- ECO E2.1 – Generate possibility to open/close windows and doors to match

climate. - ECO E2.6 – Generate possibility of night time over ventilation.

Ventilation should be used as much as possible as a free cooling source during the night as the outside air temperature tends to be lower that the inside air temperature. However it needs to be controlled during the day in order to not contribute to an increase in the cooling loads.

- ECO O2.2 – Shut off A/C equipment when not needed.

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UK Case Study 8 UKCS8 Office Building

Dunn GN, Knight IP, Bleil de Souza C, Marsh AJ Welsh School of Architecture, Cardiff University Date: December 2006

3 pipe heat recovery VRF units with roof mounted condensers and internal ceiling mounted cassettes. The entire building is mechanically ventilated with a 2-duct supply and return system, within the air handling unit located in the roof top plant room.

General Description of Case Study This case study presents the findings of a detailed monitoring study aimed at assessing the energy performance, and its potential for improvement, of a comfort cooling system installed in the first floor of a 2 storey office block. The conditioned area consists of open plans, cellular office rooms and meeting rooms. This area is serviced by Toshiba 3-pipe VRF units with heat recovery. The condensers are roof mounted with internal ceiling mounted cassettes. The cassettes draw air from the ceiling void that is also supplied with fresh tempered air from the mechanical ventilation system. The whole building is mechanically ventilated with the AHU located at the roof top plant room. The study was carried out by the Welsh School of Architecture (WSA) on the two floors of the building separately. The energy consumption of the first floor AC system was monitored as well as the internal temperature of a room at 15 minute intervals over a period of 12 months. The external weather data for the building was obtained at 5 minute intervals from a London meteorological station. From the monitoring study potential energy savings could be identified. The building was also simulated to analyse which were the highest contributors to the cooling loads in the AC system, indicating further energy saving options.

179

Building Description General Building Data: Configuration A 2 storey (Ground + 1) speculative built office building

Layout Mixture of open plan and cellular, including a number of larger training and conference rooms.

Number of floors Ground +1 (only first floor being analysed here)

Floor area (Gross) 812.7 m2

Floor area (Treated) 661 m2

Refurbishment Fabric none

Refurbishment HVAC 2000

Refurbishment Lighting none

Refurbishment Other none

Space Activity Corporate Offices & Training rooms

Occupiers Business Type Multi-national corporation

Type of tenancy Tenant

Occupant density 12.5 m2 TFA/person

Tenancy Since 2000

Caretaker / Porter Occupiers Own

Heating System Toshiba 3-pipe heat recovery VRF multi-split DX system

Ventilation System Tempered Mechanical ventilation

Cooling System Toshiba 3-pipe heat recovery VRF multi-split DX system

Econ 19 Category Type 3 - Air Conditioned Standard

Building Category BRE OD4 - Daylight Open Plan Strip 1 to 4 Storeys

Types of fuel used: Heating Electric

Cooling Electric

DHW Gas HDD 1977 Yearly Total on 20 year average

Building Envelope: Windows

Type Double

Total Area 113.2 sq. m

Type of glazing Double w/ approx 12mm air void, aluminium frames and gray tint.

Percentage of glazing by facade

12.5% North East 21.8 % North West 28.1 % South East 40.1 % South West

Glazing (u-value) 2.8 W/m2K (3.4 w/m2 w/ metal frames)

Window Reveals & Overhangs (Size & Loc.) Reveals <25mm / Eves none

External shading devices (Size & Loc.) None Specific

Internal shading devices (Type) Vertical Blinds

Internal shading devices (Location) Immediately Inside of Glazing Wall Structure Brick & block cavity Wall Insulation fibrous cavity insulation per 1999 standards Roof Structure Wood framed (Eng. Trusses), w/ OSB sheathing, felt and

180

tiles

Roof Insulation Fibrous blanket type

Roof Area n/a

Ceiling Type Suspended

Ceiling Height (Typical) approx 2.75 m

Floor to Floor Height (Typical) approx 3.25 m

Thermal mass n/a

HVAC System Design General Information: The conditioned area has 3 pipe heat recovery VRF units with roof mounted condensers and internal ceiling mounted cassettes. The cassettes draw air from the ceiling void that is also supplied with fresh tempered air from the mechanical ventilation system. The entire building is mechanically ventilated with a 2-duct supply and return system, within the air handling unit located in the roof top plant room. The ceiling voids are used as supply plenum. Detailed Information: Heating System

Boilers N/A

Heating pumps N/A

DHW Pumps N/A

Domestic hot water heater Centralised system for the entire building using instantaneous gas boilers

Ventilation

General office areas The entire building is mechanically ventilated with a 2-duct supply and return system. The air handling unit is located in the roof top plant room.

Air Conditioning

General The first floor is air conditioned by Toshiba VRF units of the 3 pipe heat recovery type. These are capable of being run in heat pump mode and use electric reheat as well. The 4 condensers are roof mounted with internal ceiling mounted cassettes. The cassettes draw air from the ceiling void that is also supplied with fresh tempered air from the mechanical ventilation system.

Ceiling void The ceiling voids are used as the supply plenum for the mechanical ventilation system.

Total Cooling Capacity 100 kW

Cooling Capacity By area 135.5 W/m2

HVAC Control Strategy *General The general strategy for the control of the HVAC system on the floor monitored is shown below in the detailed data section.

181

Detailed data: HVAC Plant Control: Toshiba integrated controls, optimised on external

temperature. HVAC zoning Internal units grouped by area (cellular or open)

Set Points 18°C heating and 24°C cooling

Run times of HVAC plant Generally from 7:00AM to 8:00 PM Monday to Friday

Planned maintenance Contract maintenance per normal standards and documentation available on request.

Performance Data General The following data illustrates the surveyed level of heat gains within the building during the period in which the AC system was monitored. Detailed Internal gains

Total Space Gains 37.0 W/m2 TFA, consisting of:

Occupancy 7.6 W/m2 TFA

Lighting 15.0 W/m2 TFA

Small Power 14.4 W/m2 TFA Building Energy Performance *General Annual Building Energy Consumption 252.6 kWh/m2 (electricity for the whole building)

Gas n/a Electricity 252.6 kWh/m2

Detailed National benchmarks for delivered energy by building type Actual building performance (% of benchmark)

Typical Practice - 404 kWh/m2 TFA 62.5%

Good Practice* – 225 kWh/m2 TFA 112% * Set at 25th percentile based on 1998 national standards Cooling Performance *General from monitoring The monitoring shows this AC (comfort cooling) system seems to be relatively energy efficient, achieving an overall annual energy consumption/m2 for cooling which was better than Typical Best Practice at the time of the survey but not as good as the Good Best Practice. However, the modelling shown later will show that the actual COP achieved by the system against the modelled cooling load is very poor.

182

Detailed from monitoring Annual cooling energy consumption –173.8kWh/m2 TFA

VRF System Energy Consumption

0.00

5.00

10.00

15.00

20.00

25.00

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

kWh/

m2

200020012002

Fig1: Monthly cooling energy consumption

Site E nergy C o nsum p tion V s. N ation al B enchm arks(Eco n19 type 2 stan dard AC offices )

0 .0

50 .0

100 .0

150 .0

200 .0

250 .0

300 .0

An

nu

al k

Wh

/

S eries1 1 29 .0 162 .73 155 .48 24 9.0

G ood Prac t ice 2001 2002 T yp ica l

Fig2: Cooling energy consumption compared to national

benchmarks

VRF Average Week Day July 01

0.00

10.00

20.00

30.00

40.00

50.00

00:00

01:00

02:00

03:00

04:00

05:00

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19:00

20:00

21:00

22:00

23:00

Time

W /

m2

AverageSTDev+1

STDev-1

Fig3: Cooling energy demand

System Part-Loading in 2001 VRF-HR

0%

2%

4%

6%

8%

10%

12%

14%

16%

1-5%

5-10%

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85-90

%

90-95

%

95-10

0%

% of Full-Load

Tim

e

Fig4: Part-load profile

Hours of operation 8759 hours per year

General from simulation A simulation of the cooling demand was performed and the breakdown of the components that contribute to the cooling load were analysed in order to see which ECO’s could be used in the building to improve its energy performance for cooling. This modelling was also used to allow an overall summer COP to be calculated (from June to September), which in this case was 0.49. This value is below the expected value for a system of this type (1.05) and is much lower than was expected from a state-of-the-art system. The potential reason for this was the 24 hour operation of the systems when not required, as well as a control issue with the systems which meant that electric reheat was used first thing in the morning to bring the space to temperature, rather than the heat pump capability of the system. Weather data: hourly data from the year of 2001 used. Meteorological station located in London. Simulation details: Energy Plus software was used to plot hourly breakdown of loads in the AC system and identify the main contributors to it. Breakdown of loads are defined

183

based on a heat balance algorithm and are subdivided into Air heat balance breakdowns and Internal surfaces heat balance breakdowns. The air load breakdowns provide: total internal convective heat gains, infiltration sensible gains and losses, ventilation sensible gains and losses and convective loads from surfaces against cooling demand on the system. The internal surface load breakdowns provide: opaque surface inside face conduction gains and losses, total internal radiant heat gains, total internal visible heat gains, window heat gains and losses, radiant exchanges with other surfaces against convective loads from surfaces. Detailed from simulation

Annual cooling demand simulated 16980kWh

MONTHLY LOADS: Air Heat Balance Breakdown

-5000.00

-4000.00

-3000.00

-2000.00

-1000.00

0.00

1000.00

2000.00

3000.00

4000.00

5000.00

6000.00

1 2 3 4 5 6 7 8 9 10 11 12

Months of the Year

Load

in kW

MONTHLY CONVECTIVEINTERNAL load (kWh)

MONTHLY CONVECTIVE heattransfer from SURFACES(kWh)MONTHLY INFILTRATION ofoutside air (kWh)

MONTHLY VENTILATION (kWh)

Fig5: Air heat balance breakdowns for whole year

MONTHLY LOADS: Inside Surface Heat Balance Breakdown

-5000.00

-4000.00

-3000.00

-2000.00

-1000.00

0.00

1000.00

2000.00

3000.00

4000.00

5000.00

6000.00

1 2 3 4 5 6 7 8 9 10 11 12

Months of the Year

Load

in k

W

MONTHLY TRA NSMITTEDSOLA R Energy (kW h)

MONTHLY Opaque SurfaceINSIDE FA CE CONDUCTIONEnergy (kW h)

MONTHLY Total INTERNA LRA DIA NT Heat Gain (kW h)

MONTHLY Total INTERNA LVISIBLE Heat Gain (kW h)

MONTHLY CONVECTIVE heattransfer from SURFA CES(kW h)

MONTHLY RA DIA NTEXCHA NGES betw eensurfaces (kW h)

Fig6: Inside surface heat balance breakdowns for whole year

COOLING DESIGN DAY: Air Heat Balance Breakdown

-40.00-35.00-30.00-25.00-20.00-15.00-10.00-5.000.005.0010.0015.0020.0025.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hours of the day

Load

in kW

h

CONVECTIVE INTERNALload (kWh)

CONVECTIVE heattransfer fromSURFACES (kWh)INFILTRATION of outsideair (kWh)

VENTILATION (kWh)

SYSTEM delivered load(kWh)

Fig7: Summer Design Day – Air heat balance breakdowns

COOLING DESIGN DAY: Inside Surface Heat Balance Breakdown

-40.00

-35.00

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

5.00

10.00

15.00

20.00

25.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hours of the day

Load

in kW

h

TRANSMITTED SOLAR Energy(kWh)

Opaque Surface INSIDE FACECONDUCTION Energy (kWh)

Total INTERNAL RADIANT HeatGain (kWh)

Total INTERNAL VISIBLE HeatGain (kWh)

CONVECTIVE heat transferfrom SURFACES (kWh)

RADIANT EXCHANGES amongsurfaces (kWh)

Fig8: Summer Design Day – Inside surface heat balance

breakdowns

Hours of operation predicted for the A/C system from the modelling 1084 hours per year

From the breakdown analysis it can be seen that for loads acting directly in the air and therefore directly on the HVAC system, the highest contributors to the cooling demand are:

- The convective heat transfer from surfaces followed by the convective internal loads, i.e. the convective portion of the internal gains. Surfaces are being heat up mainly by the internal gains followed by the solar gains and release the heat to the air through convection. As a consequence, the internal gains should be reduced together with the solar gains in order to reduce the cooling demand. ECOs related to “Other actions aimed at load reduction” (E4) should be applied together with ECOs related to “Solar Gain Reduction / Daylight Control Improvement” (E1). The most appropriate ones for this specific case study are listed in the Summary and conclusion section.

184

- Ventilation and infiltration tend to contribute positively to the cooling load as a whole because during the night the outside air temperature is lower than the inside one. However, during the day they tend to increase the cooling load as the outside air temperature seems to be most of the time equal or higher than the inside air one. ECOs related to “Ventilation/ Air movement/ Air leakage improvement” (E2) should be applied. The most appropriate ones for this specific case study are also listed in the Summary and conclusion section.

When analysing loads acting in the inside face of the surfaces and indirectly in the HVAC system, it can be seen that all the components increase the cooling load:

- The internal radiant heat gains followed by the transmitted solar gains and the total visible heat gains will heat up the surfaces that will transfer heat to the air through convection. The negative values for conduction indicate a heat transfer from the mass to the inside surface which is being heat up by the solar gains together with the internal gains. That reinforces the use of ECOs related to “Solar gain reduction / daylight control improvement” (E1) together with the use of ECOs related to “Other actions aimed at load reduction” (E4). The most appropriate ones for this specific case study are listed in the Summary and conclusion section.

Summary conclusions From the breakdown analysis it can be concluded that the following ECOs could be used to help reduce the cooling energy demand in the building:

- ECO E4.7 – Modify lighting switches according to daylight contribution to different

areas. - ECO E4.8 – Introduce daylight/occupation sensors to operate lighting switches.

Electrical lighting seems to be on all the time according to the survey and its contribution to the cooling demand is considerable.

- ECO E4.5 – Replace electrical equipment with Energy Star or low consumption

types. - ECO E4.9 – Move equipments (copiers, printers, etc.) to non conditioned zones.

Electrical equipment loads are the highest loads among the internal gains in this case, therefore any possibility to reduce the amount of energy they use and release should be considered. Most of the copiers and printers, etc in this case are in the conditioned zone, relocation to non conditioned areas could also be considered to reduce the cooling loads.

- ECO E1.1 – Install window film or tinted glass. - ECO E1.3 – Operate shutters, blinds, shades, screens or drapes. - ECO E1.4 – Replace internal blinds with external systems.

Solar control should be used to reduce the cooling loads as this is the highest load in the room

- ECO E2.1 – Generate possibility to open/close windows and doors to match

climate. - ECO E2.6 – Generate possibility of night time over ventilation.

Ventilation should be used as much as possible as a free cooling source during the night as the outside air temperature tends to be lower that the inside air temperature. However it needs to be controlled during the day in order to not contribute to an increase in the cooling loads.

ECO O2.2 – Shut off A/C equipment when not needed.

185

UK Case Study 9 UKCS9 Office Building

Dunn GN, Knight IP, Bleil de Souza C, Marsh AJ Welsh School of Architecture, Cardiff University Date: December 2006

Costum built AHU. The packaged roof top units are VRV condensers with 3 pipes Heating/Cooling and heat-recovery unit, believed to be operating as modular banks of 7 per floor. The ground and first floor ceiling voids contain in total 56 VRV 3-pipe heat and cooling ceiling cassettes.

General Description of Case Study This case study presents the findings of a detailed monitoring study aimed at assessing the energy performance, and its potential for improvement, of a comfort cooling system installed in a 2 storey office block. The conditioned area consists of open plans, cellular office rooms and meeting rooms. This whole area is serviced by a Daikin 3-pipe heat recovery system. Controls are BEMS type optimised based on external temperature. The mechanical ventilation is provided through an Air Handling Unit with its own DX cooling unit. The study was undertaken by the Welsh School of Architecture (WSA) on the whole building. The energy consumption of the AC system and the internal temperature of an open plan room were monitored at 15 minute intervals over a period of 12 months. The external weather data for the building was obtained at 5 minute intervals from a London meteorological station. From the monitoring study potential energy savings could be identified. The building was also simulated to analyse which were the highest contributors to the cooling loads in the AC system, indicating further energy saving options. Building Description General Building Data: Configuration Phase 2 is a two story rectangular offices block, probably

steel framed with non-load bearing walls

Layout Mainly open plan offices areas with cellular core containing support services and spaces etc.

186

Number of floors Ground + 1

Floor area (Gross) 3071 sq. m.

Floor area (Treated) 2566 sq. m

Refurbishment Fabric n/a

Refurbishment HVAC Various Splits added

Refurbishment Lighting n/a

Refurbishment Other Phase two built approx 1997

Space Activity Offices, Conference, National Control Room, Canteen

Occupiers Business Type Utility Supplier

Type of tenancy Owner Occupied

Occupant density 12.6 m2 TFA/person

Tenancy Since 1985

Caretaker / Porter Occupiers Own

Heating System Electric Convection fins

Ventilation System AHU

Cooling System VRV 3-pipe Heating & Cooling

Econ 19 Category Cat 3 - Air conditioned Standard (Phase Two Only)

Building Category BRE OA (Artificially lit Open plan multistorey)

Types of fuel used: Heating Electric

Cooling Electric

DHW Electric HDD 1977 Yearly Total on 20 year average

Building Envelope: Windows

Type Sealed

Total Area 790 sq. m

Type of glazing Tinted Double w/ approx 6mm air void

Percentage of glazing by facade 50 % each

Glazing (u-value) 2.8 W/m2K

Window Reveals & Overhangs (Size & Loc.) Reveals <100mm / Eves 700mm

External shading devices (Size & Loc.) None Specific

Internal shading devices (Type) Vertical Blinds

Internal shading devices (Location) 250 mm in side of glazing

Wall Structure Non-load bearing w/ Brick veneer & cavity, plus glazing system metal framed.

Wall Insulation As per 1997 code Roof Structure Pitched 20 degs, mid gray colour metal roofing Roof Insulation As per min 1997 code

Roof Area 2767 sq. m

Ceiling Type Suspended

Ceiling Height (Typical) 3.0 m

Floor to Floor Height (Typical) n/a

187

Thermal mass n/a

HVAC System Design General Information: The conditioned area has a custom Built AHU manufactured by Mallard UK Ltd. containing supply and return constant speed fans of unknown size, a 4 stage 10Kw elec. defrost, a 70kW Electric heater battery and a 4 stage DX cooling coil and integral condensers running on R22. Tempered fresh air is supplied via the ceiling plenum with ducted return. The packaged roof top units are 14 modular Daikin VRV condensers with 3 pipe Heating/ Cooling and heat-recovery unit, believed to be operating as modular banks of 7 per floor. The ground and first floor ceiling voids contain in total 56 Daikin VRV 3-pipe heat and cooling ceiling cassettes. Detailed Information: Heating System

Boilers Not known

Heating pumps Not known

DHW Pumps Not known

Domestic hot water heater Not known Ventilation

General office areas

Custom Built AHU manufactured by Mallard UK Ltd. containing supply and return constant speed fans of unknown size, a 4 stage 10kW elec. defrost, a 70kW Elec. Heater battery and a 4 stage DX cooling coil and integral condensers running on R22.

Air Conditioning

General 14 packaged roof top units. Modular Daikin VRV condensers with 3 pipe Heating/ Cooling and heat-recovery unit, believed to be operating as modular banks of 7 per floor

Ceiling void 56 x Diakin VRV 3-pipe heat and cooling ceiling cassettes.

Total Cooling Capacity n/a

Cooling Capacity By area n/a HVAC Control Strategy *General The general strategy for the control of the HVAC system on the floor monitored is shown below in the detailed data section. Detailed data: HVAC Plant Control: BEMS, optimised based on external temperature

HVAC zoning By Floor in Perimeter and other areas

Set Points 22 ºC +/- 3 ºC

Run times of HVAC plant Generally from 8:00AM to 6:00 PM Monday to Sunday

Planned maintenance Contract maintenance as per normal standards and documentation available on request.

188

Performance Data General The following data illustrates the surveyed level of heat gains within the building during the period in which the AC system was monitored. Detailed Internal gains

Total Space Gains 28.6 W/m2 TFA, consisting of:

Occupancy 7.8 W/m2 TFA

Lighting 8.2 W/m2 TFA

Small Power 12.6 W/m2 TFA Building Energy Performance *General Annual Building Energy Consumption 110.48 kWh/m2 (electricity for the whole building)

Gas n/a Electricity 110.48 kWh/m2

Detailed National benchmarks for delivered energy by building type Actual building performance (% of benchmark)

Typical Practice - 404 kWh/m2 TFA 27%

Good Practice* – 225 kWh/m2 TFA 49% * Set at 25th percentile based on 1998 national standards Cooling Performance *General from monitoring The monitoring shows this AC (comfort cooling) system seems to be very energy efficient, achieving an overall annual energy consumption/m2 for cooling which was better than the Best Practice at the time of the survey. However, the modelling shown later will show that the actual COP achieved by the system against the modelled cooling load is very poor. Detailed from monitoring

Hours of operation - 7595 hours per year Annual cooling energy consumption –51.2 kWh/m2 TFA

2 pipe DX VRV multi-split System

0

2

4

6

8

10

12

14

16

18

20

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

kWh/

m2 2000

2001

2002

Fig1: Monthly cooling energy consumption

Site Energy Consumption Vs. National Benchmarks(Econ19 type 2 standard AC offices)

0

10

20

30

40

50

60

70

80

90

100

Annu

al k

Wh/

m2

kW h/m2 44.0 40.73 38.67 63.90 91.0

Good Practice 2000 2001 2002 Typical

Fig2: Cooling energy consumption compared to national

benchmarks

189

General from simulation A simulation of the cooling demand was performed and the breakdown of the components that contribute to the cooling load were analysed in order to see which ECO’s could be used in the building to improve its energy performance for cooling. This modelling was also used to allow an overall summer COP to be calculated (from June to September), which in this case was 0.18. This value is below the expected values for a system of this type (1.05). It is most likely that the reason for this apparently very poor performance is that the system ran 24 hours a day, whilst the occupancy times were much lower. The system is also HEATING the building as a heat pump. The very low cooling efficiencies are not unexpected therefore. Weather data: hourly data from the year of 2001 used. Meteorological station located in London. Simulation details: Energy Plus software was used to plot hourly breakdown of loads in the AC system and identify the main contributors to it. Breakdown of loads are defined based on a heat balance algorithm and are subdivided into Air heat balance breakdowns and Internal surfaces heat balance breakdowns. The air load breakdowns provide: total internal convective heat gains, infiltration sensible gains and losses, ventilation sensible gains and losses and convective loads from surfaces against cooling demand on the system. The internal surface load breakdowns provide: opaque surface inside face conduction gains and losses, total internal radiant heat gains, total internal visible heat gains, window heat gains and losses, radiant exchanges with other surfaces against convective loads from surfaces.

Annual cooling demand simulated 24885.8 kWh

MONTHLY LOADS: Air Heat Balance Breakdown

-15000.00

-10000.00

-5000.00

0.00

5000.00

10000.00

15000.00

1 2 3 4 5 6 7 8 9 10 11 12

Months of the Year

Load

in kW

MONTHLY CONVECTIVEINTERNAL load (kWh)

MONTHLY CONVECTIVE heattransfer from SURFACES(kWh)MONTHLY INFILTRATION ofoutside air (kWh)

MONTHLY VENTILATION (kWh)

Fig5: Air heat balance breakdowns for whole year

MONTHLY LOADS: Inside Surface Heat Balance Breakdown

-15000.00

-10000.00

-5000.00

0.00

5000.00

10000.00

15000.00

1 2 3 4 5 6 7 8 9 10 11 12

Months of the Year

Load

in k

Wh

MONTHLY TRANSMITTEDSOLAR Energy (kWh)

MONTHLY Opaque SurfaceINSIDE FACE CONDUCTIONEnergy (kWh)

MONTHLY Total INTERNALRADIANT Heat Gain (kWh)

MONTHLY Total INTERNALVISIBLE Heat Gain (kWh)

MONTHLY CONVECTIVE heattransfer from SURFACES(kWh)

MONTHLY RADIANTEXCHANGES betweensurfaces (kWh)

Fig6: Inside surface heat balance breakdowns for whole year

COOLING DESIGN DAY: Air Heat Balance Breakdown

-120.00-110.00

-100.00-90.00-80.00-70.00-60.00-50.00-40.00-30.00-20.00-10.00

0.0010.0020.0030.0040.0050.0060.0070.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hours of the day

Load

in kW

h

CONVECTIVE INTERNA Lload (kWh)

CONVECTIVE heattransfer fromSURFA CES (kWh)INFILTRA TION of outsideair (kWh)

VENTILA TION (kWh)

SY STEM delivered load(kW h)

Fig7: Summer Design Day – Air heat balance breakdowns

COOLING DESIGN DAY: Inside Surface Heat Balance Breakdown

-120.00-110.00

-100.00-90.00-80.00-70.00-60.00-50.00-40.00-30.00-20.00-10.00

0.0010.00

20.0030.0040.0050.0060.0070.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hours of the day

Load

in kW

h

TRANSMITTED SOLAR Energy(kWh)

Opaque Surface INSIDE FACECONDUCTION Energy (kWh)

Total INTERNA L RADIANT HeatGain (kWh)

Total INTERNA L VISIBLE HeatGain (kWh)

CONVECTIVE heat transferfrom SURFACES (kWh)

RADIANT EXCHANGES amongsurfaces (kWh)

Fig8: Summer Design Day – Inside surface heat balance

breakdowns Hours of operation predicted for the A/C system from the modelling 991 hours per year

190

From the breakdown analysis it can be seen that for loads acting directly in the air and therefore directly on the HVAC system, the highest contributors to the cooling demand are:

- The convective internal loads, i.e. the convective portion of the internal gains, followed by the convective heat transfer from surfaces. Surfaces are being heat up mainly by the internal gains followed by the solar gains and release the heat to the air through convection. As a consequence, the internal gains should be reduced together with the solar gains in order to reduce the cooling demand. ECOs related to “Other actions aimed at load reduction” (E4) should be applied together with ECOs related to “Solar Gain Reduction / Daylight Control Improvement” (E1). The most appropriate ones for this specific case study are listed in the Summary and conclusion section.

- Ventilation and infiltration tend to contribute positively to the cooling load as a

whole because during the night the outside air temperature is lower than the inside one. However, during the day they tend to increase the cooling load as the outside air temperature seems to be most of the time equal or higher than the inside air one. ECOs related to “Ventilation/ Air movement/ Air leakage improvement” (E2) should be applied. The most appropriate ones for this specific case study are also listed in the Summary and conclusion section.

When analysing loads acting in the inside face of the surfaces and indirectly in the HVAC system, it can be seen that all the components increase the cooling load:

- The internal radiant heat gains followed by the transmitted solar gains and the total visible heat gains will heat up the surfaces that will transfer heat to the air through convection. The negative values for conduction indicate a heat transfer from the mass to the inside surface which is being heat up by the solar gains together with the internal gains. That reinforces the use of ECOs related to “Solar gain reduction / daylight control improvement” (E1) together with the use of ECOs related to “Other actions aimed at load reduction” (E4). The most appropriate ones for this specific case study are listed in the Summary and conclusion section.

Summary conclusions From the breakdown analysis it can be concluded that the following ECOs could be used to help reduce the cooling energy demand in the building:

- ECO E4.7 – Modify lighting switches according to daylight contribution to different

areas. - ECO E4.8 – Introduce daylight/occupation sensors to operate lighting switches.

Electrical lighting seems to be on all the time according to the survey and its contribution to the cooling demand is considerable.

- ECO E4.5 – Replace electrical equipment with Energy Star or low consumption

types. - ECO E4.9 – Move equipments (copiers, printers, etc.) to non conditioned zones.

Electrical equipment loads are the highest loads among the internal gains in this case, therefore any possibility to reduce the amount of energy they use and release should be considered. Most of the copiers and printers, etc in this case are in the conditioned zone, relocation to non conditioned areas could also be considered to reduce the cooling loads.

- ECO E1.1 – Install window film or tinted glass. - ECO E1.3 – Operate shutters, blinds, shades, screens or drapes.

191

- ECO E1.4 – Replace internal blinds with external systems. Solar control should be used to reduce the cooling loads as this is the highest load in the room

- ECO E2.1 – Generate possibility to open/close windows and doors to match

climate. - ECO E2.6 – Generate possibility of night time over ventilation.

Ventilation should be used as much as possible as a free cooling source during the night as the outside air temperature tends to be lower that the inside air temperature. However it needs to be controlled during the day in order to not contribute to an increase in the cooling loads.

ECO O2.2 – Control of system to reduce unnecessary use.