One of the common themes that emerges in the discussion of alternative sources of electricity is the problem of energy storage. Unlike conventional power plants run on fossil fuels, many renewable energy sources have somewhat unpredictable availability: the wind may or may not blow, tomorrow may be sunny or heavily overcast. And, of course, the demand for electricity is subject to considerable fluctuation over the course of the average day. Smoothing out these fluctuations requires either a way to store energy for later use, or a scheme to keep extra generating capacity available for rapid use.
This past week, Technology Review had an article about a new technology that is being deployed by a consortium of municipal utilities in California to help level the load on the power grid. The basic idea is simple: small units are installed in the air conditioning systems of office buildings and other commercial properties that use power at night, when the demand is low, to make ice that can be used for cooling during the next day. The units are made by a Colorado-based company called Ice Energy.
Over the next two years, the 11 participating utilities will install 6,000 of the devices at a total of 1,500 locations, providing 53 megawatts of energy storage to relieve strain on the region’s electrical grid. The project is the first large-scale implementation of Ice Energy’s technology.
Similar systems have been put in place for large installations before, but they tend to be specifically designed for their particular environment. The Ice Energy units are standardized, modular devices that, at an estimated manufacturing cost of $5000 per unit, can be installed in small- to medium-sized buildings.
Brian Parsonnet, Ice Energy’s chief technology officer, says the technology can cut a building’s power consumption by 95 percent during peak hours on the hottest days.
There are incidental savings as well. The power used to make the ice is transmitted across the grid at night; efficiency is increased because electrical resistance in the transmission lines generally goes down as temperatures decline.
The development of this kind of “off the rack” technology is a hopeful sign. It’s a type of development that has to occur if renewable energy sources are ever to make significant inroads in power generation.