Grossmont Hospital La Mesa, California

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 an Off-Peak Cooling (OPC) system dedicated for the surgical suites, supercooling these rooms can be done efficiently. The separate OPC 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.

OPC 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 Off-Peak Cooling (OPC) and how does it work? OPC 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 OPC 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 ICEBANK tanks. During the discharge cycle, the stored ice is used to cool 100 percent of the building’s load the next day.

With partial 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 the OPC process.

Additional hospital benefits

• Off-peak cooling systems offer 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.
• OPC is demand-responsive, offering even more cost-saving opportunities.
• The payback period is typically two to five years.
• OPC 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 OPC are not applicable. If the level of redundancy is similar for conventional cooling and OPC, the value of partial 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 OPC partial-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 OPC 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. OPC provides redundancy for less money.

The CALMAC OPC system installed at Grossmont Hospital (PDF, 89 Kb) is another example of how OPC can provide significant value. Grossmont Hospital is a 490,000 square-foot facility in La Mesa, California, and thus far, the results of installing the OPC system have been energy cost savings of $17,000 per year and a project payback of three years.

Bill Keaton, the hospital’s chief engineer said, "We're constantly looking for ways to reduce energy costs. We decided to use Off-Peak Cooling because of the demand savings and the cash incentives offered by San Diego Gas and Electric. We also wanted to use a modular ice-bank system because of its greater reliability and our need for future expansion. We're adding a new 60,000 square-foot women's center next year and ICEBANK tanks will be used to cool that, too."

Click here for additional information regarding how CALMAC Off-Peak Cooling systems can benefit medical facilities.

Click here for a partial listing of CALMAC’s project list.

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