Wednesday, July 18, 2007

An Old Idea Made New

A friend sent me a link to a story about some companies using a twist on a very old technology to reduce their office air conditioning bills. Several facilities have installed large vats of water that they freeze every night and then use the melting ice to cool the air during the day--apparently including the former White Plains, NY headquarters of Texaco, now owned by Morgan Stanley. The article goes on to suggest that the system actually improves cooling efficiency, besides shifting the cooling load to nighttime hours when power is cheaper. If this proves attractive enough, it could have important implications for the way we use energy.

Air conditioning is a major component of electricity demand, and one of the largest segments that fluctuates with the seasons. Its use is still growing, worldwide. Higher incomes and increasing urbanization are responsible, and the result is not just higher energy consumption, but a reshaping of power generation capacity to meet the daily and annual cyclicality of demand created by people's natural desire to stay cool. If ice cooling became popular, it would help to even out at least the daily peaks and valleys, while reducing the absolute magnitude of the summer/winter difference. That would allow a country's electrical needs to be met with less--and potentially less polluting--capacity.

This idea might even dampen one of the feedback mechanisms of climate change. A warmer climate requires more air conditioning, using more power, which in turn generates more of the emissions that contribute to climate change. Even if ice cooling could cut peak electricity demand by only 10%, that could be significant.

While installing giant ice vats might not be feasible for everyone, the economics should compare favorably with battery storage, or schemes to generate hydrogen at night and run it through fuel cells to meet peak demand. Ultimately, this is about storing power, efficiently, which is one of the keys to making the best use of intermittent sources of renewable energy, such as wind power.

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