New designs for off-peak cooling systems are being developed all the time. Whereas large-scale units use large, insulated, polyethylene tanks, a chiller and dedicated distribution system to cool and circulate indoor air, now, there are also smaller styles and configurations that will make off-peak cooling possible for small scale applications like light manufacturing, commercial and residential use.
The size of the system required to cool a specific building will depend on the area to be cooled. Air-conditioning volume is sized in tons, and it takes one ton (0.9 metric tons) to cool 12,000 BTUs (3.5 kilowatts) in an hour. If you're confused, that translates to about 500 square feet (46.45 square meters) of space [source: ACU Air].
The Ice Bear 50 system by Ice Energy is designed for small commercial or large residential applications. It's a roof or split-system compatible unit that will work with an air-conditioning system's existing ductwork to cool up to 30-ton hours at a maximum load of 5 tons (4,536 kilograms). According to Ice Energy, integrating the Ice Bear, which uses a conventional HVAC system during off-peak hours, with your existing system can reduce peak energy demand up to 95 percent from its first day of use. The Ice Bear can cost anywhere from $4,000 and $18,000 depending on the air conditioner involved and the specifics of the installation [source: Ice Energy]
IceCycle also manufacturers a unit designed for retrofits called the IceCycle Retro and, like the Ice Bear, it works on roof and split-system installations using the existing setup for the conversion from conventional air conditioning to off-peak cooling.
Industry leader CALMAC, who has made off-peak systems available to companies like IBM, American Airlines, McDonald's, Kohl's, DuPont, Marriott Hotels and JC Penney, is getting into some large residential installations, too, with its ICE-BANK model 1045 C tank, which is rated for 45-ton hours of cooling [source: Miller].
In the next section, we'll take a look at what the future holds for off-peak cooling.