Thermal Energy Storage for District Cooling

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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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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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Southern California Edison, Schedule TOU-8-RTP General Service-Large, Real Time Pricing

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HourlyEnergy

Rate

$3.80$0.038

Buy Low-Sell High Discharge Strategy

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$/m

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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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p. (°

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% 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