CROM

PrestressedConcrete

Tanks

For ThermalEnergy Storage

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Institutional electrical energy usage follows a bell curve with peaks during the day and valleys overnight. Local power plants must have the capacity to handle the peak periods. Power plants are often oversized to meet high demand peak periods and are forced to charge demand fees to offset the cost of excess capacity. During periods of low demand (evenings), plants must be kept running and producing electricity, often with excess capacity. In many cases, energy produced during low demand periods is offered to large commercial users at a reduced rate. Thermal Energy Storage (TES) takes advantage of these lower rates by chilling water for the cooling systems at night and storing it in insulated tanks for use during times of peak demand. This is known as load shifting or peak shifting. Depending on the specific geographic location and utility incentives, the payback of the initial construction cost can be very short.

Another potential use of Thermal Energy Storage is to store chilled water during periods of low demand then use it to increase the capacity of the chiller plant by combining it with flow from the chillers to meet the needs during periods of high demand. This is called peak shaving and can allow owners to defer purchasing expensive chiller plant equipment. Stored Thermal Energy can also be utilized as a source of emergency back-up for mission critical cooling systems. In the event of a sudden power loss, TES can be used to keep the cooling system operating until emergency back-up generators can be brought on line. The concept of thermal energy storage results in a win/win relationship between the owner of the facility and the power company. Many times the benefit to the power producer is enough for it to offer financial incentives for the construction of these projects.

Introduction - Thermal Energy Storage

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Indian River State College - West CampusPort St. Lucie, Florida874,000 Gallon TES Tank61’8” ID x 40’3” SWDConsulting Engineers:Donadio & Associates Architects, P.A.

Daytona State CollegeDaytona Beach, Florida2,500,000 Gallon TES Tank74’0” ID x 81’0” SWDConsulting Engineers:Pond & Company, Inc.

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Nielsen Media Research - Oldsmar, FloridaTwo 750,000 Gallon TES Tanks46’ ID x 60’ SWDConsulting Engineers:Alfonso Architects & FL/Engineering Matrix, Inc.

Cover Photos

Time�of�Day

0 2 4 6 8 10 12 14 16 18 20 22 24

Typical�Peak�Cooling�Load�Profile

PEAK RATE OFF PEAKOFF PEAK

Cooling�Lo

ad�D

eman

d

Cooling�Lo

ad�D

eman

d

0 2 4 6 8 10 12 14 16 18 20 22 24

Typical�Peak�Cooling�Load�Profilewith�TES

Time�of�DayPEAK RATE OFF PEAKOFF PEAK

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Crom Thermal EnergyStorage Tanks

CROM has built over 4000 prestressed concrete water tanks since 1953. We provide a turnkey service from tank and diffuser design through complete construction of the TES tank. Crom tanks are very well respected in the water industry for being bottle-tight and virtually maintenance-free. The prestressed concrete tank in combination with the PVC internal diffuser system insures many years of uninterrupted service and very low life-cycle costs. Crom’s engineers design thermal storage tanks for the greatest possible return. The union of a Crom Prestressed Concrete Tanks and thermal storage is ideal. The internal diffuser is built at our fabrication shop under controlled conditions to insure fast and accurate field installation. Our own specially trained and experienced construction crews construct the tank on site and install the internal diffuser piping. Additionally, the internal diffuser system is designed to provide the most usable volume from the tank. Our typical installation includes an external insulation and finish system (EIFS) that can provide great design flexibility in the final appearance of the installation.

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Diffuser SystemDiffuser SystemDiffuser System

Galvanized Steel Shell DiaphragmGalvanized Steel Shell DiaphragmGalvanized Steel Shell Diaphragm

Shotcrete ApplicationShotcrete ApplicationShotcrete Application

Watertightness of the tank wall is made possible by the combined performance of a steel shell diaphragm, shotcrete encasement, and wire prestressing. The steel shell extends continuously the full height of the tank wall, thus precluding by positive means any through-wall leakage. The diaphragm has no horizontal joints. The vertical joints which connect the steel shell panels are sealed by epoxy injection after the diaphragm is encased inside and outside with shotcrete. The corrugations in the steel cylinder, running in a vertical direction, provide a mechanical bond between the diaphragm and the shotcrete encasement. Mild steel reinforcement is included to resist bending moments, shrinkage, and temperature stresses. Circumferential prestressing assures permanent ring compression in the tank core wall. Crom designs its structures under the supervision of professional engineers; trains and certifies its key employees; selects and uses the best available construction materials; and adheres rigidly to high standards of quality construction.

Design - Tank Structure

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0.08 MG Chilled Water Storage Tank0.08 MG Chilled Water Storage TankDevon Energy, Oklahoma City, OklahomaDevon Energy, Oklahoma City, Oklahoma

0.08 MG Chilled Water Storage TankDevon Energy, Oklahoma City, Oklahoma

PrestressingPrestressingPrestressing

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Naturally stratified Thermal Energy Storage Tanks take advantage of the normal differences in the density of water at different temperatures to separate the chilled water from the warm water returning from the air handling system. By limiting the inlet and outlet velocity of the water, internal mixing is minimized and buoyancy forces dominate allowing the water to stratify. This allows warm water to be stacked on top of the colder denser water without the need for a physical membrane to separate them. The layer of water that separates the warm return water from the cold stored water is called the thermocline. A major key to optimizing the performance of thermal storage is the design of the internal diffuser to create the thinnest possible thermocline. The octagon diffuser configuration allows the formation of the thinnest initial thermocline by spreading the diffuser openings across the entire surface area of the tank. Initial thermocline thickness is critical because it makes the biggest impact on tank efficiency. The diffuser configuration is self- balancing, requiring no adjustments during operation. The diffuser system is designed following the same philosophy as the tank structure: provide a robust system that requires as little maintenance as possible. The materials used are designed to be long lasting and require no periodic maintenance or inspection. Crom Thermal Energy Storage Tanks are designed to provide the highest return on investment for the end user.

Design - Thermocline/Diffuserillustration-diffusser &thermoclineCold Water

To Air Handler

Warm WaterReturn

THERMOCLINE

Cold WaterReturn

Warm WaterTo Chiller

THERMOCLINE

Operation-Peak Hours

Operation-Off-Peak Hours

InternalDiffuser

InternalDiffuser

InternalDiffuser

InternalDiffuser

Economy is a natural by-product of the prestressed concrete tank design - lesser quantities of materials and labor are utilized than is possible under conventional reinforced concrete design. Of greater significance is the quality of permanence inherent in the construction materials used. Shotcrete is a durable, high-strength building material whose long life is universally recognized. Interior surfaces of the tank do not require painting. This is a major cost and maintenance benefit.

Design - Tank Structure - continued

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TypicalWall Section

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Applications

ACC4 DATA CENTERAshburn, VirginiaTwo-0.5 MG TES Tanks - 40’0” ID x 53’2” SWDConsulting Engineers:

CCG Facilities Integration Incorporated

Data Storage and Processing -

Warehouse and Distribution Centers - WALGREEN COMPANY - WAREHOUSE &DISTRIBUTION CENTERWest Palm Beach, Florida1.6 MG TES Tank - 65’ ID x 65’ SWDConsulting Engineers:

The Korte Company

Hospitals -

Learning Institutions -

EDISON STATE COLLEGENaples, Florida0.5 MG TES Tank - 45’ ID x 42’ SWDConsulting Engineers:

Atlas Engineering, Inc.

ST. MARY’S HOSPITAL, INC.West Palm Beach, Florida1.4 MG TES Tank - 69’ ID x 53’ SWDConsulting Engineers:

Johnson, Levinson, Slider & Davila

Facilities Air-ConditioningCENTRAL HEATING & COOLING PLANTFort Bragg, North Carolina1.9 MG TES Tank - 68’0” x 70’0” SWDConsulting Engineers:

U. S. Army Engineering - Savannah District

The highest standards for attractive appearance and performance are our goals. Aesthetics can be a major consideration because of the storage tank’s high profile location in many facilities. The tank’s concrete construction allows the greatest flexibility in location options. The tank structure can be built at grade, completely buried, or anywhere in between. The exterior walls of the tanks are covered with EIFS (exterior insulation finishing system) which can easily utilize color, texture and architectural embellishments to match existing or planned buildings. In addition, the exterior insulation system can be covered with brick veneers, vinyl siding, aluminum cladding or plaster finishes. The final product can be designed to fit into any architectural scheme.

Versatility & Appearance

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Capacities in Millions of U.S. Gallons

Thermal Capacities in Ton-Hours0.2 0.3 0.4 0.5 0.75 1.0 1.5 2.0 2.5 3.0 4.0 5.0 7.5 10.0 15.0 20.0 0.25

Capacities and Dimensions forThermal Energy Storage Tanks

1500 1900 2300 3000 3800 5600 7500 15,100 18,800 22,600 30,100 37,600 56,500 75,300 112,700 150,20011,300Insi

de

Dia

met

erin

Fee

t

30354045505560657075

80859095100105110115120125130135140145150155160165170175180185190195200205210215220

37’10” 47’4” 56’9”

27’9” 34’9” 41’8” 55’8” 69’6”

21’3” 26’7” 31’11” 42’7” 53’2”

16’10” 21’1” 25’3” 33’8” 42’0” 63’1”

14’1” 17’1” 20’6” 27’3” 34’1” 51’2” 68’2”

14’1” 16’11” 22’6” 28’2” 42’3” 56’3”

18’11” 23’8” 35’5” 47’4” 70’11”

16’3” 20’2” 30’3” 40’4” 60’6”

17’5” 26’1” 34’9” 52’2” 69’6”

22’9” 30’4” 45’5” 60’7”

20’0” 26’8” 39’11” 53’2” 66’6”

23’7” 35’4” 47’2” 58’11” 70’8”

31’7” 42’1” 52’7” 63’11”

28’4” 37’9” 47’2” 56’7”

25’7” 34’1” 42’7” 51’1” 68’1”

30’11” 38’7” 46’4” 61’10”

28’2” 35’2” 42’3” 56’3” 70’4”

32’2” 38’7” 51’6” 64’5”

30’0” 35’6” 47’4” 59’2”

32’9” 43’8” 54’6”

40’4” 50’5”

37’5” 46’8” 70’0”

35’0” 43’5” 65’2”

40’6” 60’9”

37’10” 56’9”

53’2” 70’10”

49’10” 66’6”

44’2” 58’11”

62’7”46’11”

55’7”

52’6”

49’9”

47’6” 70’9”

67’2”

63’10”

60’9”

57’11”

55’3”

70’4”

73’8”

Thermal energy storage inton-hours assumes a T=12 F.

Dimensions shown reflect common aspect ratios for Thermal Energy Storage Tanks. Crom Prestressed Concrete Tanks can be built to any size specified.

Phone: (352) 372-3436 FAX: (352) 372-6209 www.cromcorp.com

CROM

250 SW 36TH TERRACE GAINESVILLE, FL 32607-2889

copyright c 2015 by Crom,LLC . All Rights reserved.

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