A Cool (Green) Solution to Global Warming

Ice keeps New York office towers cool

As the summer swelters on, skyscrapers and apartments around the city will crank up air conditioners and push the city's power grid to the limit -- but some have found a cool alternative.

Some office towers and buildings are keeping their AC use to a minimum by using an energy-saving system that relies on blocks of ice to pump chilly air.

"If you take the time to look, you can find innovative ways to be energy efficient, be environmental and sustainable," said William Beck, the head of critical engineering systems for Credit Suisse.

The systems save companies money and reduce strain on the electrical grid in New York, where the city consumes huge amounts of power on hot summer days.

Ice cooling also cuts down on pollution. A system in Credit Suisse's offices at the historic Metropolitan Life tower in Manhattan is equal to taking 223 cars off the streets or planting 1.9 million acres of trees to absorb carbon dioxide from electrical use for a year, according to the New York State Energy Research and Development Authority.

Such a reduction in pollution is valuable in a city where the majority of emissions come from the operation of buildings. Officials said there are at least 3,000 ice-cooling systems worldwide.

Because electricity is needed to make the ice, water is frozen in large silver tanks at night when power demands are low. The cool air emanating from the ice blocks is then piped through the building. At night the water is frozen again and the cycle repeated.