Ice Storage Systems

8/12/2019 Ice Storage Systems

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Agenda Ice storage basics Ice storage design considerations

Full and partial storage systems Internal and external melt systems

Ice storage installations and applications


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Ice Build on Ice Coil Tube


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Ice Build on Ice Coil


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What is Ice Storage? Ice Storage is the process of using a

chiller or refrigeration plant to build iceduring off-peak hours to serve part or all of

the on-peak cooling requirement


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Ice Thermal StorageHow does it work?


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Time of Day

C o o

l i n g

L o a

d

Typical Cooling Load Profile


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Conventional System

Chiller

Cooling Load


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Ice Storage System

Ice Storage Tank Chiller

Cooling Load


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Time of Day

C o o

l i n g

L o a

d

Ice Storage Cycle

IceStorage

Cycle

IceStorage

Cycle


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0 2 4 6 8 10 12 14 16 18 20 22

Time of Day

P o w e r

( M e g a w a t

t s )

Typical Daily Utility Load Curve

Demand

Charges

High Timeof DayRates

Total Utility Capacity


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0 2 4 6 8 10 12 14 16 18 20 22

Time of Day

C o o

l i n g

L o a

d

Ice Storage Cycle

IceStorage

Cycle

IceStorage

Cycle

DemandCharges

High Timeof DayRates


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M 2 4 6 8 10 N 14 16 18 20 22

Time of Day

% G

e n e r a

t i o n

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M 2 4 6 8 10 N 14 16 18 20 22

Time of Day

% G

e n e r a

t i o n

Electric Generation Fuel Sources

Hydro-electric 0.2/kWh

Nuclear 0.4/kWh

Coal-fired steam 2.5/kWh

Combined cycle 3.0/kWhOil-fired steam 3.5/kWh

Diesel 6.5/kWhComb. turbine 7.0/kWh

TheStorage

Shift


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Thermal Storage SystemEnvironmental Advantages

Require less kWh than conventionalsystems

Utilize efficient power and produce fewercarbon dioxide emissions

Energy line losses at night are 4% to 5%lower than during the daytime

Source: Source Energy and Environmental Impacts of Thermal Energy Storage , California Energy Commission - February 1996


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Advantages of Ice Thermal Storage Reduced equipment costs Reduced energy and operating costs Colder supply water temperature


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Advantages of Ice Thermal Storage Reduced equipment costs

Only ~60% of chillers and heat rejectionequipment required

Requires only 1/4 to 1/6 of the space requiredfor chilled water storage (~3Ft 3/Ton-Hour) Requires less chiller plant plan area than

instantaneous chiller system


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30,000 RT Output

16,000 RT Heat Rejection


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Ice Thermal StorageUses Less Energy

During daytime, chillers operate at highersupply temperatures and greater efficiencywhen piped upstream of the ice storage

At night, chillers operate when ambienttemperatures are lower

Pump and fan energy can be less when

colder system supply temperatures areused


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EER of Air Cooled Chillers*

6

8

10

12

14

16

20 25 30 35 40 45 50 55

Leaving CHW

E E R

95 Air 85 Air 75 Air* includes heat rejection

75

85

95

Normal

Design Point Pre-cooling

Ice-Making


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EER of Water Cooled Chillers*

10

12

14

16

18

20

20 25 30 35 40 45 50 55

Leaving CHW

E E R

85 80 75* excludes heat rejection

Pre-cooling Normal

Design Point

Ice-Making

75

80

85


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Ice Thermal StorageReduces Operating Costs

Reduces air conditioning kW demand byapproximately 40%

Reduces air conditioning kWh by up toapproximately 15%

Reduces electric utility costs Large percentage of energy usage is at night

Daytime energy costs 2 to 5 times more thannight time energy


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http://www.usgbc.org/programs/leed.htm


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http://www.usgbc.org/programs/leed.htm


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LEED Criteria Sustainable sites (14 possible points) Water efficiency (5 possible points) Materials and resources (13 possible points) Energy and atmosphere (17 possible points)

Ozone depletion Optimize energy performance

Cost based analysis vs. ASHRAE 90.1 Indoor air quality (15 possible points) Innovation & design process (5 possible points)


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Advantages ofCold Supply Water Temperature

Smaller distribution pumps and piping Reduced pumping power Allows for economical building isolation

(indirect interface) with smaller heatexchangers Provides better dehumidification and

indoor air quality(IAQ) 78F (25.5C) at 40% RH is more comfortablethan 76F (24.4C) at 50% RH

Cold air distribution


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Burj Dubai Tower Will become worlds

tallest building at over180 floors

Currently at 156 floors 41,600 ton-hours


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Taipei 101

Currently the worldstallest building at 101floors

36,400 ton-hours


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7 th & 8 th floors37.8 F (3 C)

42 nd floor39.2 F (4 C)

74 th floor41.0 F (5 C)

Taipei 101


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Factors Favorable forIce Storage Systems

Loads are of short duration Schools

Loads occur infrequently Churches Sports venues

Loads are cyclical in nature

Process or batch cooling


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Factors Favorable forIce Storage Systems

Loads are not well matched to availabilityof the energy source

Energy costs are time-dependent Time-of-use energy rates

Energy supply is limited Demand charges for peak energy use

Utility rebates, tax credits, or othereconomic incentives are provided for theuse of load-shifting equipment


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Potential Ice Storage Projects Commercial A/C and industrial

Schools Hospitals

Office buildings Internet data centers Hotels

Airports Sports venues Manufacturing plants


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Potential Ice Storage Projects Commercial A/C and industrial District cooling

Colleges and universities Corporate campuses Hospitals Convention centers

Sports arenas Utilities


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Ice Thermal Storage Systems

Design Considerations


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Full Storagevs.

Partial Storage


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0 2 4 6 8 10 12 14 16 18 20 22

Time of Day

C o o

l i n g

L o a d

( T o n s )

Batch Cooling or Process LoadProfile


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Time of Day

C o o

l i n g

L o a d

( T o n s )

Full Ice StorageBatch Cooling or Process Application

Ice Charge Ice Discharge


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0 2 4 6 8 10 12 14 16 18 20 22

Time of Day

C o o

l i n g

L o a d

( T o n s )

Air Conditioning Load Profile


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Time of Day

C o o

l i n g

L o a d

( T o n s )

Full Ice Storage Air Conditioning Application

Ice Charge Ice Discharge


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Ice Thermal Storage System DesignFull Ice Storage

Advantages Best suited for short,

peak demand periodsand/or high, peakloads Shifts largest electricaldemand that providesthe lowest operatingcost

Provides systemstandby capability andoperating flexibility

Disadvantages Largest storage

volume required Larger chiller required Most expensive

thermal storage design


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0 2 4 6 8 10 12 14 16 18 20 22

Time of Day

C o o

l i n g

L o a d

( T o n s )

Partial Ice Storage Air Conditioning Application

Ice Charge Chiller

Ice Discharge


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Time of Day

C o o

l i n g

L o a d

( T o n s )

Ice Charge Chiller

Ice Discharge


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Time of Day

C o o

l i n g

L o a d

( T o n s )


Ice Charge Chiller

Ice Discharge


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0 2 4 6 8 10 12 14 16 18 20 22

Time of Day

C o o

l i n g

L o a

d ( T o n s

)

Ice Charge Chiller

Ice Discharge

Base Chiller


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Ice Thermal Storage System DesignPartial Ice Storage

Advantages Best suited for long

cooling periods

Lower first cost due toreduced storagevolume and smallerchiller

Provides systemoperating flexibility

Disadvantages Less standby

capability

Less electricaldemand shifted to off-peak


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Internal Meltvs.

External MeltIndirect vs. DirectContact Cooling


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Ice Storage System Types

Direct Contact Cooling Indirect Contact Cooling


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Ice Thermal StorageIce-on-Coil Technology


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Ice Thermal Storage System DesignIce on Coil - Internal Melt

Cold glycol solution is circulated through thecoil to the A/C system

Warm glycol solution, circulating through thecoil, is cooled indirectly by the melting ice

ICE

ICE ON COIL

WARMGLYCOL

IN

COLDGLYCOL

OUT

WARMGLYCOL

MELTING OCCURSFROM INSIDE

Indirect


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Ice Storage DesignInternal Melt (Indirect Contact)


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Ice Storage DesignInternal Melt Performance*

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% Ice Meltout

L e a v

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T e m p e r a

t u r e

0

1

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34

5

6

7(F)(C)

*10 hour, constant load

w/o air agitation


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Advantages Simple to design and operate

simple controls for various operating modes closed, pressurized loop

Stable, cold discharge temperatures 36F to 38F (2.2C to 3.3C) typical

Durable steel construction 150 to 300 psi (10.3 to 20.7 bar) design pressure

rating tested at 190 to 375 psi (13.1 to 25.8 bar) Flexible layout (modular tanks or vault design)


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Ice Storage Tank Chiller

Heat Exchanger

OptionalBase Chiller

Cooling Load

System Schematic


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Disadvantages Heat exchanger required for chilled water

in building loop

Not able to discharge as quickly as directcontact cooling ice melt limited by flow through coil


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Ice Thermal Storage System DesignIce on Coil - External Melt

Ice water is circulated through the icestorage tank to the A/C system

Warm return water, circulating through thetank, is cooled via direct contact with the ice

Direct

ICE

ICE ON COIL

REFRIGERANTOR GLYCOL

MELTING OCCURSFROM OUTSIDE

WATERIN

WATEROUT

AIR

WARMWATER


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Ice Storage DesignExternal Melt (Direct Contact)


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Ice Storage DesignExternal Melt Performance*

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% Ice Meltout

L e a v

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T e m p e r a

t u r e

0

1

2

34

5

6

7(F) (C)

*10 hour, constant load


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External Melt Supply Temperatures

0102030405060708090100

% Ice Remaining

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L e a v i n g

W a t e r

T e m p .

( F )

Hours

1

24

126


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6000 Ton-HoursIce Storage

6000 Ton-HoursIce Storage

375 TR Water Chiller



(Spare)

34FCWS

54FCWR 42FCWS

250 TR Glycol Chiller



(Spare)

21.4FCGS27.8FCGR

2000 GPM

1500 GPM

External MeltSystem Schematic


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Advantages Lowest chilled water supply temperatures Quickest discharge capability Eliminates glycol from chilled water loop

I S D i


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Disadvantages Chiller with lower temperature capability

generally required

Glycol control valves required on largersystems

Heat exchanger may require to manage

static head of open system More difficult to monitor amount of ice ininventory

I Th l S S


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Ice Thermal Storage SystemsExternal Melt vs. Internal Melt

External Melt Project requires a

constant, cold supplywater temperature of34F (1C) or quickdischarge periods

Trained operating staffavailable

Large savings indistribution piping system

Highest energy efficiency

Internal Melt Project does not require

coldest possible supplytemperature

Simpler design andoperation Individual buildings Energy efficiency is less

critical (extra heattransfer step required)

I Th l S S


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Ice Thermal Storage SystemsExternal Melt vs. Internal Melt

Most air conditioning applications useinternal melt

Most process and district cooling systems

use external melt


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Maryknoll Grade School

Honolulu, HawaiiBelow-Grade Concrete Tank2,000 Ton-Hours Ice Storage

District Cooling Retrofit


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Maryland Stadium Authority

Oriole Park at Camden YardsRavens Stadium at Camden Yards

Baltimore, MarylandBuried Concrete Tank

13,000 Ton-Hours Ice Storage


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Comfort Link Plant #2Saratoga and Eutaw Streets

Baltimore, Maryland Above-Grade Steel Tanks

27,000 Ton-Hours Ice Storage


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Comfort Link Market Center Chilling Station Construction (1999)


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Comfort Link Market Center Chilling Station Completion (1999)


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Comfort Link District Cooling


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gBaltimore, Maryland USA

Operations began in 1996 with traditionalelectric tariff 10:00 AM to 8:00 PM peak window Fixed peak demand charge Time of day energy rates

Began purchase of electricity throughindependent suppliers in June, 2002

System flexibility allows daily changes tooperating schedules to minimize spotmarket consumption and capacity charges

Electric Cost Components - Typical UserSRC Current Market Estimate - PJM Mid-Atlantic


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72%

5%

4%

19% Market - Energy Cost

Market - Capacity Cost

Market - Other Costs

Local Delivery / Utility

Current Market Supply Estimate, 1 Year:$85-$88/MWh


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Electric Cost Components

Energy Based on prevailing market prices Daytime energy costs average twice nighttime

energy costs

Capacity UCAP (generation capacity charge)

Highest system load hour on each of 5 highestload days (not customer)

Transmission More than $60/kW/year

Energy Cost Operating Strategy


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Chart courtesy of Comfort Link



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Demand Limiting Operating Strategy


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Chiller Ice


June 27, 2007High of 100F (37.8C)Low of 80F (26.7C)

12 mWDemand Shift

Record Heat and Record Loads

Load Leveling Operating Strategy


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August 8, 2007High of 108F (42.2C)Low of 86F (30.0C)

(1) 1750 TR chiller out of service

Load Leveling Operating Strategy


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6 mWDemand Shift

Demand Limiting Operating Strategy


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11 mWDemand Shift

Predicted performance with all chillers in service


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Ice Thermal Storage Systems

Greg HendersonDirector, Global Thermal Storage

Documents

Ice Storage Systems