-
The Role of Buildings in Smart Grid
Linda, Fu Xiao and Shengwei Wang Department of Building services
Engineering
Building Energy and Automation Research Laboratory Research
Institute of Sustainable Urban Development
The Hong Kong Polytechnic University [email protected]
5th International conference on Energy – Sustainable Energy
Policies and Technologies 15-17 October 2014, Hong Kong
mailto:[email protected]
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Outline of Presentation 1. Brief Introduction of Smart Grid 2.
Building Demand Side Management (DSM) 2.1 Outline of DSM Methods
for Buildings 2.2 Load Management in Buildings 2.3 Energy
Efficiency Improvement – An Example 3. Interactions between
Buildings and Smart Grid 4. Proactive “Building Cooling Supply
Side” Management
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1.Brief Introduction of Smart Grid 2. Building Demand Side
Management 3. Interaction between Buildings and Smart Grid 4.
Proactive “Building Cooling Supply Side” Management
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Peak load: affects grid safety
and wastes extra energy and cost due to the essential generation
capacity reserve.
50.2
50.0
49.8
Power imbalance: decreases power quality of grid and requires
more frequency controlled reserve, especially when large amount of
fluctuant renewable generations are used
and integrated to grid today.
1.1 Critical Issues in Power Grid load profile of end-users
renewable energies
-
Framework of Smart Grid
Smart grid is considered as a promising solution concerning its
improvements and benefits in power reliability, energy efficiency,
economics and sustainability.
1.2 Development of Smart Grid
Smart grid involves micro-grid, renewable energies, smart
metering system, information and communication technologies, demand
response, intelligent energy management system, etc.
Smart grid is a type of electrical grid with prediction and
intelligent response to the behaviors and actions of all power
participants.
China
-
Information and Communication Technologies (ICTs)
[Source: NIST Framework and Roadmap for Smart Grid
Interoperability Standards]
Click Here: Smart Metering Projects Map
Smart Metering System
1.3 Available Technologies for Smart Grid
http://maps.google.com/maps/ms?ie=UTF8&oe=UTF8&msa=0&msid=115519311058367534348.0000011362ac6d7d21187
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1. Brief Introduction of Smart Grid
2. Building Demand Side Management 2.1 Outline of DSM Methods
for Buildings 2.2 Load Management in Buildings 2.3 Energy
Efficiency Improvement – An Example 3. Interaction between
Buildings and Smart Grid 4. Proactive “Building Cooling Supply
Side” Management
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Power Supply – Power Demand
Mismatching between Supply and Demand
Demand Side Management Supply Side Management
1. Reducing Energy consumption by Increasing Energy
Efficiency
2. Peak Demand limiting/Load shifting
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The DSM methods in buildings basically consist of load
management and energy efficiency improvement.
2.1 Outline of DSM Methods for Buildings
-
Efficiency and
Conservation (Daily) Peak Load
Management (Daily) Demand Response
(Dynamic Event Driven)
Motivation
Economic;
Environmental protection;
Resource availability;
TOU savings;
Peak demand charges;
Reliability
Emergency supply
Operations Integrated system operations
Demand limiting
Demand shifting
Demand shedding
Demand shifting
Demand limiting
2.1 Outline of DSM Methods for Buildings
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11 Thermal Storage - 1
Energy Storage Methods
Mechanical energy storage
Thermal energy storage
Magneticstorage
Biological storage
Chemical energy storage
Hydro-storage
Fly-wheels
Compressed air storage
Electrochem-ical batteries
Organic mol-ecular storage
Sensibleheat storage
Latent heat storage
Energy storage is critically important to the success of any
intermittent energy source in meeting demand.
Thermal energy storage (TES) is an effective energy management
technology that has attracted increasing interest by building
professionals for load management.
2.2 Load Management in Buildings
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• Centralized Thermal Energy Storage Involving one/more major
storage devices (e.g. tanks) which usually are of big volume, such
as ice storage, etc. • Decentralized Thermal Energy Storage
Opposite to centralized systems, cold/heat are stored in various
small storage devices distributed in buildings. • Use of Building
Thermal Mass and Building Structures (Integrated with Phase Change
Materials) Building itself used as a thermal energy storage; PCM
integrated with building structures to increase building thermal
mass/performance.
(2.2) Means of Thermal Storage in Buildings
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Cooling Plant
Evaporators
Condensers
Air
Handling
Unit
Air
Handling
Unit
Building
Cooling Plant
Evaporators
Condensers
Evaporators
Condensers
Evaporators
Condensers
Air
Handling
Unit
Air
Handling
Unit
Building PCM
To enhance storage capability of buildings, phase change
material (PCM) is being considered in recent years.
Phase change materials have the ability to provide high energy
storage density and can store thermal energy at a relatively
constant temperature.
H(k
J/kg)
T (°C )
Heating Process(Solid)
Phase changeprocess
Heating Process(Liquid)
Tm
ε ε
Pure substancesRealistic
Ideal
It is a promising method for the buildings since most buildings
today are designed with light-weighted structures.
(2.2) Load Management – Building Integrated with Phase Change
Materials
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A Case Study of using PCM in Building Structures for Load
Management in Hong Kong
Zone 1
145m2Zone 2
175m2Zone 3
175m2Zone 4
145m2
Zone 5
110m2Zone 7
153m2Zone 8
153m2Zone 6
110m2
North
West East
20
22
24
26
28
0 12 24 36 48 60 72 84 96 108 120
Time (h)
Tem
pera
tute
of z
one
4 (℃
) Reference SSPCM
Brick wall
PCM layer
IndoorOutdoor
Hong Kong Test Case (HKD)
Reference building
PCM building
Cost saving
Normal control 1083.5 1026 5.31%
Demand Limiting Control
1082.7 968.5 10.55%
Overall cost saving
0.07% 5.6% 10.61%
Proper use of PCMs in buildings supported by optimal control
strategies can reduce the overall electricity of buildings
significantly with better thermal comfort.
(2.2)
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490 m 118 F
Six-star Hotel
High-rank commercial office
Commercial center and basement
Floor Area:
Hotel 70,000 (m2)
Office 286,000 (m2)
Commercial center 67,000(m2)
Gross area 440,000 (m2)
Experiences in A Super-high-rise Building -International
Commerce Centre (ICC)
2.3 Energy Efficiency Improvement – An Example
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EVAPORATOR EVAPORATOR EVAPORATOR EVAPORATOREVAPORATOR
COOLINGTOWER 2
COOLINGTOWER 4
COOLINGTOWER 3
COOLINGTOWER 6
COOLINGTOWER 5
COOLINGTOWER 8
COOLINGTOWER 7
COOLINGTOWER 1
COOLINGTOWER 11
COOLINGTOWER 9
COOLINGTOWER 10
EVAPORAROR
WCC-06a-01(2040 Ton)
PCHWP-06-01
FROM OFFICCE FLOORS(7-41)
TO OFFICE FLOORS(7-41)
HX HX HX HX HX HX HX
PCHWP-06-02 PCHWP-06-03 PCHWP-06-04 PCHWP-06-05 PCHWP-06-06
WCC-06a-02(2040 Ton)
WCC-06a-04(2040 Ton)
WCC-06a-03(2040 Ton)
WCC-06a-05(2040 Ton)
WCC-06a-06(2040 Ton)
CDWP-06-01 CDWP-06-02 CDWP-06-04CDWP-06-03 CDWP-06-05
CDWP-06-06
CT-06a-01 CT-06a-02 CT-06a-03 CT-06a-04 CT-06a-05 CT-06a-06
CTA-06a-01 CTA-06a-02 CTA-06a-03 CTA-06a-04 CTA-06a-05G
Cooling tower circuit
A
F
D
CA
B
E
B
D
C
EFG
Secondary water circuit for Zone 1
Secondary water circuit for Zone 2
Secondary water circuit for Zone 3 and Zone 4
Primary water circuit
Chiller circuit
Cooling water circuit
(S-B
)
FROM PODIUM & BASEMENT
TO PODIUM & BASEMENT
HX HX (S
-B)
(S-B
)
(S-B
)
FROM OFFICE FLOORS (43-77)
TO OFFICE FLOORS (43-77)
(S-B
)
CONDENSER CONDENSER CONDENSER CONDENSER CONDENSER CONDENSER
HXHXHX
TO OFFICE FLOORSS (79-98)
FROM OFFICE FLOORS (79-98)
(S-B
)(S
-B)
SCHWP-42-01 to 03SCHWP-42-04 to 06
SCHWP-78-01 to 03
PCHWP-78-03PCHWP-78-01 PCHWP-78-02
PCHWP-42-01 PCHWP-42-02 PCHWP-42-03 PCHWP-42-04 PCHWP-42-05
PCHWP-42-06 PCHWP-42-07
SCHWP-06-06 to 09
SCHWP-06-03 to 05
SCHWP-06-01 to 02
SCHWP-06-10 to 12
CTA Towers (without heating coil) CTB Towers (with heating
coil)
Central Cooling System
(2.3)
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• Verifying/improving the system configuration and component
selection including the chiller system, water system
(primary/secondary system), heat rejection system (cooling towers),
fresh air system etc.
• Verifying and improving the metering system for proper local
control, and the original proposed control logics at the design
stage.
• Proposal of additional metering system for implementing
supervisory control and diagnosis strategies and related facilities
for implementing these strategies.
Design commissioning mainly concerns the future operation and
control performance of HVAC systems, including:
The typical energy-saving efforts from the design and the
installation phases
(2.3) Commissioning at Design Stage
-
HX-42 HX-42 HX-42 HX-42 HX-42 HX-42 HX-42
(S-B
)
FROM OFFICE FLOORS (43-77)
TO OFFICE FLOORS (43-77)
(S-B
)
HX-78HX-78HX-78
TO OFFICE FLOORSS (79-98)
FROM OFFICE FLOORS (79-98)
(S-B
)(S
-B)
SCHWP-42-01 to 03SCHWP-42-04 to 06
SCHWP-78-01 to 03
SCHWP-06-06 to 09
To Z
one
3&4
From
Zon
e 3&
4
Flow meter
Bypass valve
EVAPORATOR EVAPORATOR EVAPORATOR
EVAPORATOREVAPORATOREVAPORAROR
WCC-06a-01(2040 Ton)
PCHWP-06-01
FROM OFFICCE FLOORS(7-41)
TO OFFICE FLOORS(7-41)
HX-42
PCHWP-06-02 PCHWP-06-03 PCHWP-06-04 PCHWP-06-05 PCHWP-06-06
WCC-06a-02(2040 Ton)
WCC-06a-04(2040 Ton)
WCC-06a-03(2040 Ton)
WCC-06a-05(2040 Ton)
WCC-06a-06(2040 Ton)
CDWP-06-01 CDWP-06-02 CDWP-06-04CDWP-06-03 CDWP-06-05
CDWP-06-06
A
F
D
CA
B
E
B
D
C
EF
Secondary water circuit for Zone 1
Secondary water circuit for Zone 2
Secondary water circuit for Zone 3 and Zone 4
Primary water circuit
Chiller circuit
Cooling water circuit
(S-B
)
FROM PODIUM & BASEMENT
TO PODIUM & BASEMENT
HX-06
(S-B
)(S
-B)
(S-B
)
FROM OFFICE FLOORS (43-77)
TO OFFICE FLOORS (43-77)
(S-B
)
CONDENSER CONDENSER CONDENSER CONDENSER CONDENSER CONDENSER
HX-78HX-78HX-78
TO OFFICE FLOORSS (79-98)
FROM OFFICE FLOORS (79-98)
(S-B
)(S
-B)
SCHWP-42-01 to 03SCHWP-42-04 to 06
SCHWP-78-01 to 03
PCHWP-78-03PCHWP-78-01 PCHWP-78-02
PCHWP-42-01 PCHWP-42-02 PCHWP-42-03 PCHWP-42-04 PCHWP-42-05
PCHWP-42-06 PCHWP-42-07
SCHWP-06-06 to 09
SCHWP-06-03 to 05
SCHWP-06-01 to 02
SCHWP-06-10 to 12
To cooling towersFrom cooling towers
HX-42 HX-42 HX-42 HX-42 HX-42 HX-42
HX-06
Original System Revised System
Secondary water loop systems of 3rd/4th zones
Primary pumps are omitted
(2.3) System Design Optimization
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Comparison between Two systems
0
200
400
600
800
1000
1200
1400
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
24Time (h )
Pum
p po
wer
(kW
)
Original designAlternative design
Typical sunny-summer day
Annual Pump Energy Saving is 1M kWh
(2.3)
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Optimal control strategies for central air-conditioning systems
Chiller sequence, optimal start-up Optimal chiller sequence - based
on a more accurate cooling load
prediction using data fusion method, and considering demand
limiting.
Adaptive online strategy for optimal start - based on simplified
sub-system dynamic models.
Ventilation strategy for multi-zone air-conditioning system
Optimal ventilation control strategy - based on ventilation demands
of
individual zones and the energy benefits of fresh air
intake.
(2.3)
-
Chilled water system optimization
Optimal pressure differential set point reset strategy;
Optimal pump sequence logic;
Optimal heat exchanger sequence logic;
Optimal control strategy for pumps in the cold water side of
heat exchangers;
Optimal chilled water supply temperature set-point reset
strategy.
Cooling water system optimization
Optimal condenser inlet water temperature set point reset
strategy;
Optimal cooling tower sequence.
Optimal control strategies for central air-conditioning
systems
(2.3)
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• 1,000,000 kWh (about 2.2% of energy consumption) saving due to
the modification on the secondary water loops of Zone 3 &
4.
• 2,360,000 kWh (about 5.1% of annual energy consumption of
chillers and cooling towers of the cooling system) saving due to
the change from single speed to variable speed using VFD.
• 607,000 kWh (about 2.8% of annual energy consumption of
chillers and cooling towers of the cooling system) saving by
modifying the lowest frequency is limited at 37Hz.
• 3, 500,000 kWh (about 7% of the total energy consumption of
HVAC system) saving by using PolyU control strategies based on the
original design.
Summary of Energy Benefits in ICC
Saving by Control Optimization – compared with the case when the
HVAC system operates correctly as the original design intent.
About 3.5M per year
Saving by Commissioning (Improving the system configuration and
selection) – compared with the original design.
About 3.5 M per year The annual total energy saving
is about 7.0M kWh !
(2.3)
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1. Brief Introduction of Smart Grid 2. Building Demand Side
Management
3.Interactions between Buildings and Smart Grid
4. Proactive “Building Cooling Supply Side” Management
-
01 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
24
Pow
er S
uppl
y an
d D
eman
d (M
W)
Time (hours)
Power Demand
Power Supply
Power Surplus
Power Shortage Power Surplus
Power Surplus
3.1 Interactions between Buildings and Smart Grid
-
Power Supply Power Demand
Power Stations Building Sectors
Power Flow (transmission & distribution)
Information Flow (monthly bill)
“One-way” Operation of Conventional Power Grid (3.1)
Online
Offline
“One-way” approach: Operation online but Communication with
outdated information. Buildings cannot help relieve power imbalance
timely using demand response.
-
Power Supply Power Demand
Power Stations Building Sectors
Power Flow (distributed generation)
Information Flow (information & communication
technologies)
Renewable Generations
“Two-way” Operation of Smart Grid (3.1)
Online
Online
“Two-way” approach enable smart grid to achieve a better overall
performance of all participants when integrated with distributed
generation and storage.
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WEATHER DATA
INTERNAL GAIN
HVAC SYSTEMS OPTIMAL CONTROL STRATEGIES
BUILDING LOAD AGGREGATION
BUILDINGS LOAD PREDICTION
DYNAMIC PRICING
OPTIMAL SETTING Smart Grids
Illustration of the interactive Concept (3.1)
-
Supply Curve: electricity price Increases when demand
increases
Demand Curve: demand decreases when electricity price
increases
Price ($/KWh)
Demand (KWh)
Supply Curve Demand Curve
Resulting Price
Initial Demand
Resulting Demand
Final Demand
Dynamic Pricing in a Certain Time Interval [Source: Fred C.
Schweppe et al., 1988]
Electricity pricing is the essential incentive to encourage
demand responses
3.2 Principle of Dynamic Pricing
-
Cap
acity
& L
oad
Pr
ofile
Time (24 hr.)
smart grid power capacity
smart grid optimal operation profile
end-users load profile at price α , β
Cap
acity
& L
oad
Pr
ofile
Time (24 hr.)
end-users load profile at price α′ , β′
adjust electricity price from α , β to α′ , β′
smart grid power capacity
smart grid optimal operation profile
Illustration of load profile alteration under incentive prices
Objective of the Interaction under Dynamic Pricing (3.2)
Overall energy efficiency of smart grid can be improved by
approaching overall balance of power supply and demand sides.
Operation cost savings of end-users can also be achieved and
benefit in the form of electricity prices.
-
The integration of smart metering system with BAS
Possibility of Establishing Interaction Integrated with smart
meters and grid information management and control centre, Building
Automation Systems (BASs) can provide valuable information and
communication (e.g. energy demand characteristics) for grid
optimization.
(3.1)
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Grid Dynamic Pricing Setting
Altered Building Power Demand
Predictor
Building Power Demand Predictor
Building Power Demand Alteration
Potential Characterization
Pi: the reference power demand prediction of the ith
building
Indices Pi
Pi′
Pi′: the altered power demand prediction of the ith building
r
Building Optimal Power Demand Control
r: the finalized electricity prices
Smart Grid Information Management and Control Center
Building Automation System
Intelligent Field Devices
(Offline Process)
(Online Process)
(Online Process)
r′: the trial electricity prices
r′
Other Buildings
Other Buildings
∑
Interactive Building Power Demand Management Strategy
Building Power Alteration Estimation
Building-Smart Grid Interaction
Building Power Demand
Management
(3.1)
-
1. Brief Introduction of Smart Grid 2. Building Demand Side
Management 3. Interaction between Buildings and Smart Grid
4.Proactive “Building Cooling Supply Side” Management
-
• HVAC systems count for nearly 50%-60% of the total electricity
consumption of buildings.
Power Grid HVAC Systems Electricity Cooling
To maintain thermal comfort
4.1 Building Cooling Load Management
• Increase/decrease of building cooling demand can significantly
change power consumption of the HVAC system, then the
buildings.
- Reduce building cooling demand in the case of grid power
supply shortage.
- Increase building cooling demand in the case of grid power
supply surplus.
-
- Conventional Method
HVAC Systems Cooling
To maintain thermal comfort
Cooling supply side Cooling demand side
Conventional Method: cooling demand side management - Change the
building indoor air temperature (Tindoor)
Limitation: - Long time required to reduce the HVAC power demand
due
to the building thermal capacity.
4.1 Building Cooling Load Management
-
Example of the Building Cooling Reduction
• Indoor temperature set-point reset (1℃ increase)
7
9
11
13
9 11 13 15 17
HVA
C P
ower
C
onsu
mpt
ion
(MW
)
Pnormal Plimit
15
20
25
30
35
9 11 13 15 17
Prov
ided
Coo
ling
Load
(M
W)
Qnormal Qlimit
22
23
24
25
26
27
9 11 13 15 17
Indo
or
Tem
pera
ture
(℃) Tnormal Tlimit
Reset period
Indoor Temperature
Building Cooling
HVAC Power
- Conventional Method (4.1)
Time delay over 30 in minutes
Indoor temperature increase: 1 ℃ Power peak reduction: 650kW
(6%) Response time required: over 30minutes
-
Proactive “Building Cooling Supply Side” Management : - Chillers
are the major cooling producer/power consumer in HVAC system. -
Proactively reduce the power of chillers (e.g. reduce the chiller
operating number) during grid power shortage.
Proactive “Building Cooling Supply Side” Management
HVAC Systems Cooling
To maintain indoor air temperature
Cooling supply side Cooling demand side
(4.1) - Proactive Method
-
Advantage: - Fast response by rapidly/immediately reducing power
of HVAC in response to grid power shortage.
Increase Tindoor
Decrease Cooling supply
to building
Decrease Cooling supply
by chillers
Decrease Power consumption
of chillers
Proactive “Building Cooling Supply Side” Management (4.1)
- Proactive Method
-
Comparison of Response Speed
Indoor Air Temperature Set Point Reset (Conventional Method)
Chiller Direct Load Control (Proactive Method) Time
Chiller Power
Demand
Response time is over 30 minutes
Chiller Power Reduction
Temperature Reset Signal
(4.1) - Conventional vs. Proactive Methods
Time
Chiller Power
Demand
Response in seconds and be stable in minutes
Chiller Power Reduction
Direct Load Control Signal
-
Item Avg. Power Decrease(kW)
Limiting Time(hour)
Avg. Power Increase(kW)
Resuming Time(hour)
Chiller Demand Limiting Strategy
1015 2 1050 1
-2000
-1500
-1000
-500
0
500
1000
1500
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
24
Power Alteration of Chillers and Pumps kW
hours
Chiller(s) Number Reduced
Chiller(s) Resumed
Power Alteration
A Simulation Case of the Proactive Management (4.1)
-
4.2 Proactive “Building Cooling Supply Side” Management
- It is difficult to determine the reduced cooling to ensure an
accepted indoor comfortable level;
- Water distribution system could be out of balance;
- Over-supplied water could be caused, resulting in deficit flow
in decouple line;
- Pump power could be highly increased.
Some potential problems could be caused if just simply change
the operating number of chillers
- Potential Problems
-
AHU
AHU
CHIL
LER
CH
ILLE
R
Bypass
Secondary pump
Primary pump
Tsup Tsup
AHU
Tsup
AHU
Tsup
• • •
Close AHUs: sufficient Remote AHUs: insufficient
Water distribution is not balanced
Examples of Potential Problems (4.2)
Water Imbalance Problem
-
Water Imbalance Problem
• There is no existing solutions available. • Examples of
solutions being considered in our current research:
- Proactive control the water valve openings by resetting AHU
supply air temperature set-point;
- Proactive control of terminal demands by resetting the indoor
temperature set-points;
- Direct and scheduled control of valve openings of AHUs.
(4.2) (4.2)
Possible solutions
-
Conclusions • Buildings can play an important and effective role
in addressing
the critical issues in smart grid: peak load and power
imbalance. • BAS, together with smart metering system, enable an
bidirectional
interactions between power supply and demand sides for
grid-scale control and optimization.
• Practice and regulations in BAS specifications need to be
revised and updated for bidirectional interaction with grid.
• Proactive “building cooling supply side” management can
provide fast response to power shortage of smart grid. But proper
proactive control strategies need to be developed further to solve
the problems when using conventional strategies based on cooling
supply responding to cooling demand
-
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