Energy Insights Singapore 2013-04
Transcript of Energy Insights Singapore 2013-04
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ENGINEERING ADVANTAGE
ENERGY INSIGHTSOPTIMISING HYDRONIC SYSTEMS
FOR ENERGY SAVINGS
Jean-Christophe Carette
Singapore, April 2013
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ENGINEERING ADVANTAGE
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opyrightTAHydronicsSA.Allrightsreserved.
World's energy consumption
2
40% of the world's energy
consumption is used in buildings*
50% of this is in HVAC systems alone*
(*) Sources: European Commission EPBD (point 6, pp1) &
US Department of Energys Buildings Energy Data Book
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ENGINEERING ADVANTAGE
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Energy savings on HVAC in buildings
3
HVAC installationUse of new technologies
System approach ofhydronic design
Shorter pay-back times
Building structure(insulation, double glazing, )
Best way to save energyLarger energy savings
Long pay-back times
Human factorAvoid interferences with
the HVAC systemEducate tenants and
maintenance team
Never-ending task
Building modifications require
adaptation or modernization of
the HVAC installation to take into
account new heat gains/losses
When modifying a HVAC
installation one must take into
account the capabilities of
peopleusing the installation
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ENGINEERING ADVANTAGE
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Energy savings via hydronic optimization
4
Optimising a building's HVAC
system can reduce its energy
consumption by 30% :
By avoiding the deterioration
of production unit
efficiencies,
By optimizing the energyefficiency of the hydronic
distribution,
By guaranteeing a stable and
accurate room temperature.
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IMPROVING
PRODUCTION UNIT
EFFICIENCIES
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ENGINEERING ADVANTAGE
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Coefficient of Performance (COP) isused to indicate chiller efficiency:
Heat transfer (and thus COP) is good when Log Mean Temperature Differencebetween water and refrigerant is kept high
Evaporator refrigerant temperature remains constant
Supply water temperature Ts is usually kept constant
Thus return water temperature Trmust be kept "high"
to keep LMTD high
Keeping a high Tr (thus a high T = Tr-Ts) provides higher COP at partial load
Chillers
6
Evaporator
Condenser
Chilled water
Tr Ts645.2
compressor
evaporator
P
PCOP
Refrigerant saturated
suction temp.
Tr
Ts
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Effect of a decrease of the return water temp. on COP
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Example :
Chiller: 200 tons (703 kW)
Water condenser temperatures: 29,5/35C
Supply temperature of chilled water Ts: 7C
A reduction of return temperature of chilled water can lead to a
15% drop of the COP
Return temp. chilled water Tr[C]
COP
5
4,6
4,4
4,24
4,2
4,4
4,6
4,8
5
5,2
10,5 11 11,5 12 12,5 13
15%
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6,0
8,0
10,0
12,0
14,0
16,0
18,0
20,0
22,0
24,0
26,0
0% 20% 40% 60% 80% 100%
Variable flow proportional control
8
Returntemp.Tr
2-way circuit (variable flow)
Flow through terminal unit
Temperature regime:
Ts/Tr/Ti = 6/12/23.5C
qp
STAD
H
C
Variable flow circuit
The DT through a terminal unit increases
when the flow reduces.
Thus the return water temperature increases
when the flow reduces.
All benefits for chiller COP.
Cooling
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0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0% 20% 40% 60% 80% 100%
On-off control Flow increase at partial load
Manually balanced variable flow on-offcontrol system
100 identical units; Pump head 200 kPa; Terminal unit 20kPa; On-off CV 5 kPa
Temperature regime:
Ts/Tr/Ti = 6/12/23.5C
Totalsystemflow
System load
At 50% load, the total flow in system reaches 77% of the total design flow.This is a 54% increase w.r.t. the required flow (50%) at 50% load.
Seasonal flow increase lead to an estimated increased pumping energy
consumption up to +4% of total plant energy consumption
10
4%
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0%
20%
40%
60%
80%
100%
120%
0% 20% 40% 60% 80% 100% 120% 140% 160%
On-off control Emission at partial load
At flow that is near design flow,
emitted power does not increase
much with the flow
Control signal switches on/off when
room temperature deviates much
beyond the thermostat differential
Flow
Em
ission
11
Roomt
Design
set-point23.5C
Time
At partial load in the system,
if a valve is open:
k
TqP
D
(Troom - Tset-point) >0