Ice Energy, a  Colorado company, has signed a contract with the Southern California Public Power Authority to deploy rooftop units that use electricity at night to make ice. The ice is then used to cool buildings during the day.

The system effectively stores electricity made at night when demand and cost is low and uses it to reduce electricity demand on hot afternoons, when demand is at its peak.

Initially, 53 megawatts of storage will be installed on rooftops in the power authority’s service territory. The Los Angeles Department of Power and Water is the biggest user.

Christopher Hickman, a vice president of Ice Energy, said that his product would replace gas generators that might run only 5 percent of the hours in a year.

According to Bill D. Carnahan, the executive director of the Southern California Public Power Authority “The total 24-hour efficiency improvement is 8 percent”.

The ice storage units cost about $US2,000 per kilowatt of capacity.

(Based on sources including the New York Times)