Cold Comfort

Commercial thermal energy storage (TES) systems have proved to be one of the most efficient means of cooling large buildings by taking advantage of lower-cost electricity. The technology saves money and energy by drawing power during off-peak hours, typically at night when many utility companies lower prices, to chill or freeze water in a storage tank that is used to cool the building during the day.

The systems designed to cool large commercial buildings use chillers for cooling, which has been a major barrier to residential use. Recently, however, one manufacturer has introduced a TES system designed to work with refrigerant-based air-conditioning systems, making TES a practical cooling solution for buildings between 2,000 and 50,000 square feet, including large homes.

Ice Energy’s Ice Bear 50 integrates with a standard 5-ton air-conditioning compressor/condenser unit, which operates at night to freeze 500 gallons of tap water in the Ice Bear storage module. During the day a 100-watt motor pumps refrigerant through coils in the Ice Bear and then to a standard evaporator coil and blower. The cooled refrigerant in the evaporator coil then cools the building’s air. According to the manufacturer, the Ice Bear 50 simply intersects the connection between the condensing unit and the evaporator coil. While it is freezing water, the condenser unit does not cycle on and off but operates continuously, increasing the system’s efficiency.

Although there are many high-efficiency residential air conditioning systems available, thermal energy storage has the advantage of using primarily off-peak energy. Ice Energy claims that its system can reduce a building’s peak-hour electrical demand by up to 90 percent. An Ice Bear 50 unit can range in price between $4,000 and $18,000 depending on the size of the air conditioner, the application, and installation costs, says Randy Zwetzig, Ice Energy’s vice president. It can be installed by any licensed HVAC contractor.

Ice Energy’s commercial air-conditioning technology boasts greater efficiencies and is getting a makeover for residential application. Currently no other TES system manufacturer makes a model designed specifically for residential air conditioning. However, commercial TES system manufacturer Calmac Manufacturing Corp. has several large-scale residential installations under its belt. Using commercial air conditioning equipment in a house requires the builder and architect to work closely with a mechanical engineer, who can work with the manufacturer to design and size the system appropriately, says Paul Valenta, Calmac’s North American sales manager. Calmac’s smallest TES system, the ICE-BANK model 1045 C tank, delivers about 45 ton hours of cooling. The company claims its system’s small footprint requires less field piping and fewer connections, thus reducing installation costs.

Many utilities already offer time-of-use rates for residential electricity users, and as more utilities move toward this kind of pricing structure—encouraging users to shift their electrical demand to off-peak hours—TES systems could become a more practical residential solution, Valenta predicts.

Ice Energy. 970.545.3630. www.ice-energy.com.

Calmac Manufacturing Corp. 201.569.0420. www.calmac.com.