IBPSA Conference - HVAC Paper Hazem Elseoudy

Building Simulation: A Tool in HVAC System Design, Selection and EnergySavings

Hazem M. Elseoudy1,*

1 Independent Researcher, Cairo, Egypt

* Corresponding author. Tel: + 20 1002540888, E-mail: [email protected]

Abstract: Buildings are the dominate energy consumers on the planet. HVAC systems contribute to 30 % ofenergy use in buildings (from 22 % to as high as 54 %). Escalating energy costs are driving customers andconsultants to choose different alternatives in regard to HVAC systems in order to save on running costs. Egyptis a gas producing country and it is assumed that gas is offered at low prices. Consultants and owners areswitching from using traditional electrical compression cycle equipment to use high initial cost direct firedabsorption chillers in order to save on running costs. The approach sounds appealing; however as engineers it isour responsibility to provide customers with value engineering for their procured equipment and thus protecttheir investments. Building simulation softwar s became very handy as powerful tools to estimate the energyconsumption of various HVAC systems and building energy. Even if the project budget, circumstances andarchitecture considerations limit the choice to use a specific HVAC system, and in order to offer a sustainabledesign, economic lifecycle analysis should be performed to provide a comprehensive approach over the lifecycleof the project.In this research different projects in Egypt and various HVAC systems were modeled and investigated usingbuilding simulation and modeling software at the design stage, and the study was completed with an economiclifecycle analysis.Each building has different characteristics regarding building usage, function, cooling load profile, lighting,energy prices, bui etc. Building simulation tools can modeland replicate these factors. Therefore, it is very important to use building simulation modeling all these factorsagainst different proposed HVAC systems before jumping to conclusions. And thus, develop a completeunderstanding for the systems and buildings under design in order to choose the optimum HVAC system designand select the equipment that will result in achieving significant reductions in building energy use and savings;in addition to lower carbon emissions and reduced environmental impacts.

Keywords: Building Simulations and HVAC System Selection, Modeling HVAC Systems, HVAC System Selectionand Energy Saving, HVAC Lifecycle Analysis, Emissions Resulting From HVAC and Building Energy Use

1. Introduction1.1. Overview of energy used in buildings

and factors of considerationWorld total energy production is dividedbetween the building sector, the industrysector and the transportation sector. Thebuilding sector consumes 41% of the energywhile the latter two use up 31% and 28%respectively. As is shown in fig. 1 [1], the41% consumed by the building industryreflects 22% being used up by residentialbuildings while 19% reflects the usage bycommercial buildings; thus highlighting thefact that buildings are the dominate energyconsumers on the planet.

Fig. 1. Data Source: US EIA - World EnergyConsumption by Sector 2011

Energy plays a vital role in the developmentof world economies, thus creating newopportunities. A major issue of concern isthat the increasing world demand on energyaccompanying economic growth createsmore pressure on the world supply channels

Topic name: Energy in Buildings

rd thBuilding Simulation Cairo 2013 - Towards Sustainable & Green Built Environment, Cairo, June 23 - 24
mailto:[email protected]

and resources along with national andeconomic resources. Fig. 2 shows theestimated projection of energy consumptionby fuel type. According to the US EnergyInformation Administration, world energyconsumption will increase by 53% between2008 and 2035. Likewise, based on theinformation obtained from the samedatabase, energy consumption in Egypt isalso estimated to rise by 67% to 77%between 2008 and 2035. [2]

Fig. 2. World energy consumption by fuel type,1990-2035

Fig.3 shows the increase and the expectationof energy demands for different parts of theworld without imposing energy regulationsand improving energy efficiency especiallyamong non OECD countries (i.e. Africa,

[3]

Fig. 3. World Energy Demand chart - SourceExxonMobil Outlook Report 2013-2040

Another major environmental concern is thewater consumption associated with energyproduction as shown in table-1. [4]

Table-1 Water consumption in (L/1000kWh) bytype of electricity generation

PowerGeneration

Technologies

Efficiency (litersper 1000 kWh)

Hydroelectric 260

Geothermal 1,680

Solar Thermal 2,970 - 3,500

Fossil fuelthermoelectric 14,200 28,400

Nuclear 31,000 74,900

Water is heavily consumed during energygeneration. Therefore, with the increase inenergy demands there will be penalties on thewater resources. In other words, there shouldbe concerns with buildings water footprintnot just from the domestic, process coolingand irrigation water use perspectives but alsowith the water consumed due to buildingsenergy consumption associated with energyproduction.

Another factor of consideration is thebuildings impact on the climate change.Buildings are a key player in CO2 emissionsalong with other emissions which contributeto the global warming and greenhouse effect.Buildings accounts for 35% of theGreenhouse Gas Emissions in the U.S. [5]

Consequently, when designing new buildingsor retrofitting existing ones energy efficiencymust be addressed as the major concern bythe designer, architect, mechanical engineer,operator and all others involved in thebuilding industry. Fig.4 shows the potentialenergy savings from efficiency gains. [6]



Fig. 4. Potential Global Energy Saving fromEfficiency Gains.

1.2. Buildings and sustainabilitySustainable design or sustainable building isa hot topic in nowadays building practice.But what does sustainability really means?

Smethod of harvesting or using a resource sothat the resource is not depleted or

. [7]sustainable, a society needs to meet threeconditions: Its rates of use of renewableresources should not exceed their rates ofregeneration; its rates of use of non-renewable resources should not exceed therate at which sustainable renewablesubstitutes are developed; and its rates ofpollution emissions should not exceed theassimilative capacity of the environment .[8]

Comparing the effects the building industryhas on the environment (i.e. resources use,

places a lot ofresponsibilities on the people involved in this

thebusiness is done not to jeopardize the futuresgenerations and the planet. Each decision tobe taken will affect future generations.

understand that theindustry can no longer continue with thesame old conducts for constructing buildings.

With the available and affordabletechnologies engineers now have the ease ofinvestigating the effects of selected systemsand materials on buildings allowing the makeof better choices within a reasonable time.

1.3. Why HVAC mattersI where buildings consumeenergy. Fig.5 shows typical building energyconsumption. HVAC systems contribute to30 % of energy use in buildings with anormal range of 22 % or as high as 54 %. [9]

Fig. 5. Typical Building Energy Consumption

1.4. Building simulation softwares;powerful tools

Each building has different characteristics(i.e. building usage, cooling load profile,lighting, building materials, geographic

simulation tools have the capabilities tomodel and replicate these factors.

Simulation softwareThey are powerful tool for estimating energyconsumption of HVAC systems; along withevaluating the effect of building material,envelope, orientation, glazing, and otherconsiderations that would affect the energyuse and consumption of the building.

1.5. Energy and engineeringresponsibilities

The escalating energy costs are drivingcustomers and consultants to choose differentalternatives in regard to HVAC systems inorder to save on running costs. Egypt is anatural gas producing country and it has been



assumed that using HVAC equipmentutilizing natural gas will result in loweroperating costs. That made consultants andowners think about switching from usingelectrical compression equipment to use gasdirect fired absorption chillers that have highinitial cost hoping to save on running costs.

The approach sounds appealing; however,without detailed analysis this would becomevery tricky. Engineers have the responsibilityto provide customers with value engineeringfor their procured equipment and thus theirinvestments. Even if the project budget, andarchitecture considerations call for a specificHVAC system, different vendors offeringthis specific system should be energymodeled before selecting equipment based oninitial costs.

In order to offer a sustainable designeconomic lifecycle cost analysis (LCCA)should be conducted to provide acomprehensive approach over the lifecycle ofthe project. Thus it is very important to usebuilding simulation to model all the HVACproposed systems against the factorsaffecting building design to recognize theirenergy performance before jumping toconclusion. And hence, develop a completeunderstanding of the systems under design inorder to choose the optimum HVAC systemthat will result in achieving significantsavings in building energy use.

In this research different projects in Egyptwith various proposed HVAC systems weremodeled and investigated using buildingsimulation software at the design stage andthe studies were completed with economiclifecycle costs analysis.

2. Methodology2.1. HVAC systemsThere are a huge number of HVAC systemsavailable worldwide. These systems havedifferent efficiency, advantages andlimitations. A number of HVAC systemshave been considered for the three casestudies presented.

HVAC system selection is a very criticaldecision to be made. The satisfaction of thecustomer and occupant is what determinewhether the HVAC system was a success orfailure. A good designer must be able toforesee the performance of the intendedHVAC system.

In addition to that, other factors have to beconsidered such as initial cost, operatingcosts, load capacity required and the marketadoption of the technologies to be used.

Another important factor is the ownerperspective of the building operation and thelife expectancy of the equipment to be used.

2.2. Life expectancy of HVAC systemsIn order to perform the LCCA, theanticipated life of the HVAC systemsunderstudy must be recognized.

The ASHRAE application handbook containssurvey-based estimated service life of HVACsystem components. The data were used toperform the LCCA presented.

2.3. Data gathering and the buildingmodeling software

The methodology used in conducting thisresearch is summarized as follows:1- Understanding of the cooling load was

developed.2- Equipment data, catalogues, capacity...etc

of proposed systems were gathered.3- Information gathered was used to create

the energy models for the building andsystems.

4- The energy model outputs and systemeconomics were fed into economicsoftware to develop the LCCA.

In this research two Carrier energy modelingsoftwares were used to investigate the energyconsumption of the different proposedHVAC systems.

The first was Carrier Hourly AnalysisProgram (HAP). HAP is three tools in one.The first tool estimates load and design the



HVAC systems while the second toolsimulates building energy use and calculateenergy costs. It is also used for generatingLEED reports. HAP uses the ASHRAEtransfer function method for load calculationsand detailed 8,760 hour-by-hour simulationtechniques for energy analysis.

The second energy tool used was the CarrierChiller System Optimizer (CSO) developedfor simulating chilled water plants.Calculations are based on actual data,including ASHRAE bin weather patterns,building load profile, occupancy schedulesand auxiliary equipment.

After formalizing a clear understanding ofthe building loads, proposed sized equipmentwere sent to different vendors for prices andperformance data from their matchingequipment. Gathered equipment data fromsuppliers (i.e. sizing, actual load, energyefficiency...etc.) were fed back again into themodeling section of HAP or CSO forperforming energy analysis vs. actualequipment sizing and performance.

Then the LCCA was performed using CarrierEngineering Economic Analysis (EEA)software. This program performs 4 types ofeconomic analysis of which:

- Simple payback analysis- Private sector lifecycle analysis

HAP can export the energy simulation modelto the EEA saving time and minimizingerrors. The equipment initial costs gatheredwere fed into the EEA along with the energymodels to perform the LCCA for each case.

2.4. Case study -1; the small office spaceTable-2 summaries the assumptions and thedata gathered used in simulating thisbuilding:

Table- 2 Case study-1 data & design assumptionsLocation Cairo, Egypt

Application Type Office SpaceOperation Schedule 8 (hr/day) Fri & Sat. Off

Area 427.5 (m2)

Estimatedcooling capacity

84.4 (kW)

Occupancy 86 (persons)

LCCA, Equipmentlife expectancy

15 (yrs.) [10]

Electric rate2013 commercial

tariff [11]

Table-3 is showing the initial cost for the 3competing brands.

Table- 3 Equipment initial costs for case study-1

Brand-1 Brand-2 Brand-3Initial Cost

(EGP) 148,475 108,400 100,100

As a rented property, the owner requirementshas limited the HVAC system choice in usingDX split units to condition zones separately.Prices and catalogues for 3 different A/Cbrands were gathered. Table-9 shows theperformance data and comparison for the 3brands vs. the estimated load required. Afterthat, the 3 brands have been modeled forenergy consumption using HAP. LCCA wasperformed using simple payback method.

2.5. Case Study-2; The WTC commercialbuilding:

The scope of this study was to compare theLCCA for two different proposed chilledwater systems (Absorption chillers systemvs. centrifugal chillers system) then decidewhich would be the more feasibleinvestment.

Table-4 is the assumptions and data asprovided by the project consultant. Initialcosts are provided in table-5 [12].

CSO was used to create the energy model forthe following two alternative systems:A. Absorption chillers Qt. 3 - each 1407

(kW).B. Centrifugal chillers Qty. 3 - each 1407

(kW).



Table- 4 Case study-2 data and assumptionsLocation Cairo, Egypt

Application Hotel

Weather dataASHRAE Cairo

IWECOperation schedule 24 (hours)Estimated cooling

capacity4220 (kW)

LCCA, Equipmentlife expectancy

25 (yrs.) [13]

Electric Rate 0.25 (EGP/kWh)Natural Gas Rate 0.3 (EGP/m3)

Table-5 Initial cost and estimated annualmaintenance costs absorp. vs. centrif. systems.

Absorptionchillerssystem

Centrifugalchillerssystem

Initial Cost (EGP) 8,205,000 6,306,000Annual maintenance

costs (EGP/yr.) 120,000 102,000

2.6. Case study-3: The 5th District Mall:The scope of this case study was to calculatethe cooling load, provide system comparisonand identify investment costs for thefollowing 6 proposed alternative systemsavailable in the Egyptian HVAC market aspresented in table-6.

Table-6 Equipment estimated initial costsSystem Type Estimated Initial

Cost (EGP)VRF system 8,100,000Air cooled

chillers system 9,317,000

Water cooledchillers system 9,500,000

Absorptionchillers system 9,999,999

DX split system 4,500,000Water cooledpackage units 12,000,000

Table-7 contains the design data andassumptions used in case study-3.

Table-7 Case study-3 design assumptionsLocation Cairo, Egypt

Application Mall, Retail

Weather DataASHRAE Cairo

IWECOperation Schedule 9 to 12 AM (hours)Estimated Cooling

Capacity1746.2 (kW)

Air-conditioned area 7,575.7 (m2)

Occupancy 3.72 (m2 /Person) [14]

Lighting Intensity 26.91 (W/m2) [12]LCCA, Equipment

life expectancy25 (yrs.)

HAP was used to calculate the cooling, andthen sized equipment was sent to differentvendors for actual equipment performanceand prices. The LCCA was performed afterthe energy modeling was created.

3. Results3.1. Results for case study-1; The small

office spaceThe following table-8 is the energysimulation modeling output results for casestudy-1.

Table-8 Simulation results for case study-1

Brand-1 Brand-2 Brand-3HVAC Elec.

(kWh) 69,908 74,806 77,645

% of HVAC toannual energy cost 30.3 31.8 32.6

Annual HVACenergy cost/ floor

area (EGP/m2)116.49 124.68 129.43

CO2 emissionsequivalent (Kg)

164,668 168,168 170,196

HVAC annualenergy cost elect.

49,774 53,275 55,304

Non-HVACannual energy

cost elect.114,262 114,288 114,302

Total AnnualEnergy Cost 164,036 167,563 169,606



Fig.6 is showing that using brand-1 willresult in 30.3 % of energy consumed byHVAC components versus 69.7% by non-HVAC components in this building. Brand-2and brand-3 would use 31.8% and 32.6%respectively of the total building energy.

Fig. 6 Brand-1 Annual HVAC & Non-HVACCosts Totals

Table- 9 Unmet load hours comparison for the 3brands versus estimated space and zone loads

The comparison in table-9 is between theequipment of the 3 proposed brandscapacities versus the estimated zones coolingload. This table is also showing the numberof the unmet load hours using each of theproposed brands.

The results for the LCCA using simplepayback method are showing that brand-2 isthe winner case over both brands aspresented in table-10.

HVAC 30 3%.

Non-HVAC 69.7%

ZoneNo.

Space / ZoneName

EstimatedCoolingCapacity

(kW)

Brand-1 [15] Brand-2 [16] Brand-3 [17]Equipment

GrossCooling

Cap. (kW)

UnmetLoadHours

EquipmentGross

CoolingCap. (kW)

UnmetLoadHours

EquipmentGross

CoolingCap. (kW)

UnmetLoadHours

1 A/P Broker R. 5.60 6.01 0 6.44 0 6.80 02 A/P Delivery R 4.30 4.98 0 5.27 0 5.27 03 A/P MGRS 2.70 3.37 0 3.51 0 3.52 04 Archive 1 9.40 9.01 0 9.01 0 9.01 05 Archive 2 3.10 3.37 0 3.51 0 3.52 06 Cashier Room 3.80 3.37 0 3.51 0 3.52 07 Facility Mgr. 1.00 3.37 0 3.51 0 3.52 08 Meeting R. 2.00 3.37 0 3.51 0 3.52 09 PBX 2.50 3.37 0 3.51 0 3.52 010 Printing Pool 2.30 3.37 0 3.51 0 3.52 011 Reception 4.50 4.98 0 5.27 0 5.27 012 Space 1 4.20 4.98 0 5.27 0 5.27 013 Space 2 5.50 6.01 0 6.44 0 6.80 014 Space 3 4.20 4.98 0 5.27 0 5.27 0

15 Space 4 6.706.74 157 6.74 796.01 697 6.44 327 6.80 1218.57 0

16 Server Room 5.10 6.01 3 6.44 0 6.80 017 Top T/T Mgr. 2.60 3.37 0 3.51 0 3.52 018 Waiting 1 4.10 4.98 0 5.27 0 5.27 019 Waiting 2 6.70 6.01 0 6.44 0 6.80 020 Waiting 3 4.10 4.98 0 5.27 0 5.27 0



Table- 10 LCC analysis results for case study-1

3.2. Results for case study-2: The WTCCommercial Building

Table-11 represents the energy consumptioncomparison and savings by each HVACsystem component understudy.

Table-11 Annual energy use details of chilledwater system components in (kWh) for eclecticuse and (m3) for gas use.AnnualEnergy

Use Det.

Centrif.System

(kWh/yr.)

Absorp.System

(kWh/yr.)

Savings

(kWh/yr.)

%Savings

Chillers 3,382,506 241,728 3,140,778 93%Coolingtowers 300,146 765,472 (465,326) -155%

Chilledw. pumps 604,320 604,320 0 0%

Cond. w.pumps 906,480 1,625,621 (719,141) -79%

TotalElec. Use5,193,451 3,237,1411,956,310 38%

NaturalGas Use 0

1,943,122(m3)

(1,943,122)(m3) n/a

Table-12 is showing the detailed comparisonof the annual energy cost used by eachcomponent in the systems and the finalenergy cost savings in (EGP).

The energy report executive summary intable-13 is showing that the centrifugalchillers system has the lowest running cost.

The summary of the LCCA economic studyusing the private sector analysis for mutuallyexclusive base is displayed in table-14.

Table-12 Annual energy cost detialed results andcomparison between centrifugal chillers systemvs. absorption chillers systemAnnualEnergy

Cost Det.

Centrif.System(EGP)

Absorp.System(EGP)

Savings

(EGP)

%Savings

Chillerelectric 847,142 60,537 786,605 93%

Chillerfuel 0 582,937 (582,937) n/a

Coolingtower 75,173 191,700 (116,527) -155%

Chilled w.pumps 151,355 151,342 13 0%

Condenserw. pumps 227,033 407,111 (180,078) -79%

Totalenergy

cost1,300,7031,393,628 (92,925) -7%

Table-13 Executive summary for the energymodeling of the centrifugal vs absorption chillersystem

EconomicCriteria

Best SystemDesign for

Each Criteria

Value(EGP)

LowestAnnual

Energy Cost

(A) CentrifugalSystem 1,300,703

Table-14 LCCA comparison summary betweenabsorption versus centrifugal chiller systemsChallenger Base

CaseAdditionalFirst Cost

(EGP)

NPWSavings(EGP)

Absorption Centrif.[Winner]1,899,000 -14,507,986

3.3. Results for case study-3: The 5thDistrict Mall

The energy modeling results for the 5thDistrict Mall project in case study-3 arepresented in table-15.

Challenger Base Case AdditionalFirst Cost

(EGP)

PaybackPeriod(yrs.)

Brand-2[Winner]

Brand-3 7,600 4.0

Brand-1 Brand-2[Winner]

41,795 n/a



Table-15 Energy modeling results of case study-3

The comparison in the annual running costsin (EGP) for the six proposed HVAC systemsare presented in table-16.

Table-16 Annual energy consumption cost inEGP for case study-3

VRFSystem

Air CooledChillers

WaterCooled Ch.

AbsorptionChillers

DuctedSplit

Water C.Units

HVAC elec.(kWh) 1,270,305 1,603,859 1,451,012 833,914 1,645,923 1,972,066

HVAC naturalgas (m3) 0 0 0 454,079 0 0

HVAC annualenergy cost

(EGP)914,072 1,154,171 1,044,166 1,044,166 1,184,460 1,419,239

Total annualenergy cost

(EGP)3,369,681 3,609,840 3,499,790 3,509,631 3,640,127 3,874,949

% of HVAC toannual totalenergy cost

27.1% 32.0% 29.8% 29.8% 32.5% 36.6%

HVAC annualenergy cost /

floor area(EGP/m2)

120.67 152.35 137.83 139.16 156 187

CO2 emissionsequivalent (Kg) 3,345,354 3,583,671 3,474,486 3,941,950 3,613,730 3,846,773

SystemComponent

VRFSystem

AirCooled

(EGP)

WaterCooled

AbsorptionChiller

DuctedSplit

Water C.Units

(EGP) (EGP) (EGP) (EGP) (EGP)Air System Fans 128,714 128,888 128,886 128,886 105,005 109,476

Cooling 785,124 943,070 634,722 634,722 1,074,555 1,102,306

Heating 234 0 0 0 4,900 1,208

Pumps 0 82,213 206,990 206,990 0 163,590Heat Rejection

Fans 0 0 73,568 73,568 0 42,659

HVAC Sub-Total 914,072 1,154,171 1,044,166 1,044,166 1,184,460 1,419,239

Lighting 1,281,023 1,281,070 1,281,052 1,281,052 1,281,075 1,281,120

Elec. Equipment 1,174,479 1,174,523 1,174,506 1,174,506 1,174,527 1,174,568

Non-HVACSub-Total 2,455,502 2,455,593 2,455,558 2,455,558 2,455,602 2,455,688

Grand Total 3,369,574 3,609,763 3,499,723 3,499,723 3,640,061 3,874,927



The results also showed the water cooledpackage units manufactured locally wereneither competitive in operating cost nor inprice. It has the highest initial cost among theproposed systems and it added no value fromthe operating cost point of view. Therefore, itwas rejected and omitted from the design andthe economic analysis at early stage.

On the other hand, the DX split system wasdismissed for architectural reasons as havingmany condensing units installed on thebuilding facades.

The two tables (15 and 16) revealed that theVRF system has the lowest annual operatingcost.

Table-15 displayed that the VRF system hasthe lowest HVAC energy cost representing27.1% of the total energy cost of thebuilding. In addition to that, the table showedthat the VRF system has the lowest annualCO2 emissions which are 3,345,354 (Kg) asestimated by the energy model as shown intable-15.

The LCCA was performed only for the fourremaining competing systems. The LCCAresults in table-17 disclosed that the VRFsystem is the winner case.

Table-17 the Lifecycle incremental analysis datafor case study-3

Challenger Base Case AdditionalFirst Cost

(EGP)Air cooledch. System VRF [Winner] 1,217,000

Water cooledch. system VRF [Winner] 1,400,000

Absorptionch. system VRF [Winner] 1,899,999

4. Discussion4.1. Discussion of case study-1From the table-9, the estimated cooling loadfor zone no. 6 was 3.8 (kW). After running

the energy model for the 3 proposed brands,brand-1 with 3.37 (kW) gross coolingcapacity was sufficient to cover the loadgiving 0 (hours) of unmet load. This meansthat, it is not always necessary to use biggeror equal capacity machine to cover and liftthe space load.

Also from table-9, Zone no. 15, withestimated load of 6.7 (kW), is another strongexample to prove this point. When modeledagainst the nominal 24,000 (Btu/hr.) baseunit from the three competing brands; brand-1 achieved 697 (hours) unmet load;compared to 327 (hours) by brand-2 and only121 (hours) unmet load by brand-3. Using 2(units) from brand-1 3.37 (kW) each resultedin 157 (hours) unmet load while equivalentunits from brand-2 each 3.51 (kW) resultedin 79 (hours) unmet load. Thus if theapplication is critical and demands 0 unmet

then the designer have to move tobigger model when choosing and selectingequipment to be used. This of course willreflect on the cost, performance and energyconsumption.

The additional first cost of 41,795 (EGP) forbrand-1 which has the best energy efficiency,could not be justified over the 15 (years)expected life of the a/c split equipment.Therefore, from the economic stand pointbrand-2 was the winning equipment.

4.2. Discussion of case study-2The LCCA summary in table-14 showed thatthe centrifugal chillers system is the winningsystem, although first impressions were tothe favor of using gas fired absorptionchillers which was assumed to have loweroperating costs that would offset the initialcost differences for this project.

4.3. Findings and discussions of casestudy-3

The results of the energy simulation and theLCCA showed that the VRF system is thewining system among the 6 proposedsystems and would generate the lowestemission levels.



The difference in CO2 emissions between thelowest two systems in operation is 129,134(Kg) annually. Considering 20 years ofsystem operation will result in around2,582,680 (Kg) of CO2 emission reduction.

The simulation also highlighted that the gasfired absorption chillers system is the worstsystem in terms of CO2 emissions withannual operation emissions level of3,941,950 (Kg). If this system to be deployedover VRF system, this will increase CO2emissions by 11,931,920 (Kg) equivalentover 20 years period. Such figures should bewell-thought-out at decision making.

Fig. 7 Comparison of absorption vs. water cooledsystem component costs as a percentage of totalbuilding energy cost

The electric driven water cooled chillers andthe absorption chillers are classified underwater cooled systems. Fig.7 highlights thepumping power increase associated with thecondensing water side of the absorptionchillers compared to electric driven watercooled chillers.

In addition to that, the increase in heatrejection associated with cooling tower fansadds more energy consumption to absorptionchiller systems.

Therefore, specifying energy saving

with water cooled systems on bothcondensing water pumps and cooling tower

fans if can be toleratedby the selected system and load profile. Alsothe additional price for the VFD has to beconsidered in the economic study thoughthey are becoming affordable technologynowadays.

The energy modeling results in table-16showed that the six competing systems werevery close in terms of operating costs.Therefore, this did not yield any significantpayback period within the studied equipmentexpected life.

5. ConclusionEach building has its unique characteristicstherefore it should be considered and studiedseparately. No generalization should beconceded without carful study. Theperception and assumptions about certain

should not be taken for granted.

All project aspects should be considered suchas site location, availability of energy source,application type and load profile . Inaddition, energy prices at project site must beconsidered as it differs depending on sitelocation and utilities provided. Economicevaluation and LCCA for alternative has tobe made and investigated for accuratedecision making.

It is recommended that no equipment shouldbe evaluated independently. HVACequipment has to be studied as completesystems. Though the studied cases proved theopposite about absorption chillers, thesesystems still could provide significant energysavings in other applications than thoseexamined. To maximize energy savings,various system arrangements should beevaluated; for example, the electric chillerversus absorption chillers or using electric/absorption hybrid systems.

design engineersshould provide energy modeling forbuildings and perform LCCA for proposedHVAC systems and equipment. Also, they

05

10152025303540Absorption Chillers Water Cooled Chillers



have to investigate the environmentalimpacts of various systems and clarify theinformation to clients.

At this point, client awareness andinvolvement is very crucial in order tounderstand the differences and the ecologicaleffects of building systems. This will resultin wiser decisions to be taken not just basedon economics but rather with respect to theenvironment and sustainability concerns or asknown as social responsibilities.

The building industry cannot continue to dobusiness as it used to be. Energy guidinglegislations and codes should be imposed andenforced. Energy conservation has to beamong the high regional priorities for Egypt.Energy saving measures and technics has tobe implemented and studied carefully inorder to maintain and sustain thedevelopment of the Egyptian economy.

In summary, there are lots of new emergingtechnologies that should be considered andexplored. Using building simulation tools isbecoming very crucial to model all thefactors affecting building design in order toevaluate different HVAC systemsalternatives before jumping to conclusions.Single HVAC equipment should not becompared separately; whole systems have tobe studied. Systems should not be chosenbased on initial cost only. A completeunderstanding of the HVAC systems andbuildings under design has to be made beforedeciding the best optimal HVAC solutionthat will result in achieving significantenergy reductions, in building energy alongwith having lower environmental impacts. References [1] U.S. Energy Information Administration,

Annual Energy Review 2011, DEO/EIA,2011, pp. 38.

[2] U.S. Energy Information Administration,International Energy Outlook 2011,DEO/EIA, 2011, pp. 2.

[3] ExxonMobil, The Outlook for Energy: A

View to 2040, 2013, pp. 8.

[4] Willie D. Jones, How Much Water DoesIt Take to Make Electricity?,http://spectrum.ieee.org/energy/environment/how-much-water-does-it-take-to-make-electricity, 2008

[5] Greenhouse Gas Emissions byElectricity End-Use,http://www.epa.gov/climatechange/ghgemissions/sources/electricity.html

[6] ExxonMobil, The Outlook for Energy: AView to 2040, ExxonMobil, 2013, pp. 6.

[7] Sustainability definition MerriamWebster Dictionary:http://www.merriam-webster.com/dictionary/sustainable

[8] ASHRAE, ASHRAE GreenGuide: theDesign, Construction, and Operation ofSustainable Buildings, Elsevier, 2ndEdition, 2006, pp. 16.

[9] Wise Grid Solutions,http://wisegridsolutions.com/efficientlighting.html

[10] ASHRAE, ASHRAE ApplicationsHandbook, 2003, pp. 36.6 table-3.

[11] Electricity Tariffs, 2013http://egyptera.org/ar/t3reefa.aspx

[12] Carrier, Data provided by Carrier Salesand Maintenance departments, 2008.

[13] ASHRAE, ASHRAE ApplicationsHandbook, 2003, pp. 36.6 table-3.

[14] Arthur A. Bell Jr., PE, HVACEquations, Data, and Rules of Thumb,McGraw-Hill, 2nd Edition, 2007, pp.97- 108.

[15] Carrier, Carrier Split ResidentialCatalogues, 2013.

[16] LG, LG Split Residential Catalogues,2013.

[17] Samsung, Samsung Split ResidentialCatalogues, 2013.


http://spectrum.ieee.org/energy/environhttp://www.epa.gov/climatechange/ghgehttp://www.merriamhttp://wisegridsolutions.com/efficientlighttp://egyptera.org/ar/t3reefa.aspx

Documents

IBPSA Conference - HVAC Paper Hazem Elseoudy