IceBank® Energy Storage: Cooling for a Greener, Smarter Future
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U.S. Green Building Council Energy Star ARI Medical Facility Administrator


St. Francis Medical Center - Liliha
Honolulu, HI

Doctors require that surgical suites be very cool in order to help slow a patient’s metabolism and to keep doctors and their teams comfortable. By installing Hybrid Cooling system dedicated for the surgical suites, supercooling these rooms can be done efficiently. The separate hybrid cooling system avoids lowering the chilled-water temperature for the entire hospital, which reduces energy costs. It also provides additional cooling capacity, should it be needed in other areas of the hospital. This is all accomplished without increasing electric demand.

Energy storage can help the standby chiller provide a higher return on investment by having it make a portion of the next day’s cooling using low-cost nighttime electricity. Using the stored cooling the next day provides cost savings by lowering demand. While making ice, heat can also be recovered to preheat water for the water heaters, saving even more money. In some cases, the standby-generator size can be reduced as well.

What is Hybrid Cooling and how does it work? Hybrid cooling is a proven technology that takes advantage of low-cost, off-peak electric rates to produce cooling energy for use when electric rates are higher. CALMAC’s ICEBANK® thermal energy storage tanks work in conjunction with a hospital’s chiller to make ice during less-expensive off-peak hours at night. The ice is stored in the tanks and then used the next day to cool the hospital during more-expensive on-peak hours.

There are at least three hybrid cooling strategies to consider: full storage, partial storage, or a combination. Full storage shifts a building’s entire cooling load to off-peak hours. The building’s chiller only runs at night in order to charge the ICEBANKenergy storage tanks. During the discharge cycle, the stored ice is used to cool 100 percent of the building’s load the next day.

With partial energy storage, ICEBANK tanks work in tandem with the chiller. The chiller produces ice at night and continues to run the following day, cooling a portion of the hospital’s load. The stored ice in the ICEBANK tanks cools the remaining load. As a result, hospitals may be able to install a smaller than peak load chiller, while reducing energy costs.

Click here (PDF, 440 Kb) for more information regarding thermal energy storage.

Additional hospital benefits

  • Hybrid cooling offers hospital operators flexible cooling fuel source choices in a deregulated energy market to save the most money. Do I cool with a liquid fuel, on-peak electricity, or off-peak electricity? As rates change, so can the cooling operation.
  • Electric costs for cooling can be lowered because of a lower demand and off peak energy rates if available.
  • Hybrid cooling is demand-responsive, offering even more cost-saving opportunities.
  • The payback period is typically two to five years.
  • Hybrid cooling has the ability to efficiently lower humidity levels, which makes patients and staff feel more comfortable even at higher thermostat settings.
  • In new construction, the size and cost of air handlers, motors, ducts, and pumps can be reduced by 20 to 40 percent, further increasing cost savings.
  • Click here for a complete list of benefits.

Misconception: A hospital needs a redundant chiller, so the economics of energy storage are not applicable. If the level of redundancy is similar for conventional cooling and hybrid cooling, the value of energy storage can be proven. Using a hospital with a 1000-ton cooling load as an example: a redundant conventional design would be two 1000-ton chillers. A comparable partial energy storage design with redundancy would be two 600-ton chillers and a CALMAC ICEBANK tank farm. If either chiller fails or the ice tank farm fails, the facility can still be cooled on a peak day. However, the advantage that the hybrid cooling redundant design provides is that the chillers and associated equipment are downsized, helping to offset the system’s first cost while reducing energy and operating costs. Hybrid Cooling provides redundancy for less money.

Click here for additional information regarding how CALMAC thermal energy storage can benefit medical facilities.

Click here for a partial listing of energy storage projects.

Please click here to contact any of CALMAC’s regional managers for additional information or questions.

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