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Thermal Energy Storage
for District CoolingSteve Benz
Director of Global Thermal Storage
and District Energy
Daily Electricity Demand vs. Supply
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Ele
ctr
ic P
ow
er
(mW
)
Time of Day
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Addressing Electric Supply Problems
• Rolling blackouts
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Addressing Electric Supply Problems
• Rolling blackouts
• Cash incentives
• Higher energy costs
– Demand charges
– Energy charges
– Connection charges
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Tariff-Based
or
Market-Based
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$0.00
$1.00
$2.00
$3.00
$4.00
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24Summer Day
Time of Day
Southern California Edison, Schedule TOU-8-RTP General Service-Large, Real Time Pricing
ExtremelyHot
Very Hot
ModeratelyHot
Mild
HourlyEnergy
Rate
$3.80$0.038
Buy Low-Sell High Discharge Strategy
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July 01 July 02 July 03 July 04 July 050
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DC
P E
lectr
ic L
oad
mW
Wh
ole
sale
En
erg
y C
ost
$/m
Wh
r
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Addressing Electric Supply Problems
• Rolling blackouts
• Cash incentives
• Higher energy costs
– Demand charges
– Energy charges
– Connection charges
• Industry mandates or regulations
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6C - Symposium: Thermal Energy Storage, Operational Experience & Economic Value
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6C - Symposium: Thermal Energy Storage, Operational Experience & Economic Value
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6C - Symposium: Thermal Energy Storage, Operational Experience & Economic Value
3 Key Decision Drivers
• Chiller selection
• Size
• Chilled water temperatures
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Chiller Selection Considerations
Chilled Water Storage
• Water as heat transfer
fluid
Ice Storage
• Glycol as heat transfer
fluid
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14 Figures courtesy of CB&I.
Stratified Chilled Water Storage
Glycol
Chiller
Water
Chiller
Cooling
Loads
Ice Storage Storage
Discharge
Cycle
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Glycol
Chiller
Water
Chiller
Cooling
Loads
Charging
Cycle
Chiller Selection Considerations
Chilled Water Storage
• Water as heat transfer
fluid
• Lift capability
• Higher production
efficiency
• Ease of retrofit
• Can locate TES tank at
remote loop location
Ice Storage
• Glycol as heat transfer
fluid
• Lift capability
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Size Matters
Chilled Water Storage
is 6 to 8 times larger than
Ice Storage
Entergy Solutions – Houston, Texas, USA
88,000 Ton-Hours (310 mW-Hours)
2008: 3rd International District Cooling Conference & Trade Show – Dubai
19 Photos courtesy of CB&I.
Los Angeles, California, USA Sacramento, California, USA
Jeddah, KSA
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Austin, Texas, USASingapore
Advantages of Colder Chilled Water Supply Temperature
• Reduced CHW loop flow
– Reduced pumping energy
– Maximize distribution piping asset value
• More economical building isolation (indirect
interface) with smaller heat exchangers
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Ice Storage System Types
EncapsulatedFrozen Solid
Ice-on-Coil
Internal Melt or External Melt
Chilled Water Supply Temperatures
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Ch
ille
d W
ate
r S
up
ply
Tem
p. (°
C)
% Discharged
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Internal Melt With Air Agitation
with Glycol to Chilled Water HX
External Melt Without HX
Encapsulated or Frozen Solid
with Glycol to Chilled Water HX
Chilled Water Storage
°F
3 Key Decision Drivers
• Chiller selection
• Size
• Chilled water temperatures
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Questions?Steve Benz
Director of Global Thermal Storage
and District Energy
