The Hindu : Front Page : Ice to cool, and save energy

Online edition of India's National Newspaper
Wednesday, Jul 25, 2007
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Ice to cool, and save energy

New York City office towers use it to ease power burden

System relies on ice blocks to pump chilly air
There are 3,000 ice-cooling systems worldwide

NEW YORK: As the summer swelters on, skyscrapers and apartments around America’s largest city will crank up air conditioners and push the city’s power grid to the limit. But some office towers and buildings are minimising their energy use by using a system that relies on blocks of ice to pump chilly air.

The systems save companies money and reduces strain on the electrical grid, which uses huge amounts of power on hot summer days.

“If you take the time to look, you can find innovative ways to be energy efficient, be environmental and sustainable,” said an engineer for Credit Suisse.

Ice cooling also cuts down on pollution. A system in Credit Suisse’s offices at the Metropolitan Life tower in Manhattan is equal to taking 223 cars off the streets or planting 770,000 hectares 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 where the majority of emissions come from the operation of buildings. There are at least 3,000 ice-cooling systems worldwide.

The process

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.

Ice storage can be used as the sole cooling system, or it can be combined with traditional systems to ease power demands during peak hours.

At Credit Suisse, for example, the company must cool 170,000 sq m of office space.

In the basement, three main cooling rooms house chilling machines and 64 tanks that hold 3,000 litres of water each. Credit Suisse has a traditional air conditioning system, but engineers use the energy-saving system first.

Engineers say it is very efficient. “When you make something mechanical, it can break, but a big block of ice... isn’t going to do anything but melt,” said Todd Coulard of Trane Energy Services, which built the system.

Ice storage at Credit Suisse lowers the facility’s peak energy use by 900 kilowatts, and reduces overall electric usage by 2.15 million KwH annually — enough to power about 200 homes.

At the Morgan Stanley facility in Westchester County, the system reduces peak energy use by 740 kilowatts and overall electricity usage by 900,000 kWh annually.

Both companies received incentives from the New York State Energy Research and Development Authority to improve the power grid and help businesses reduce operating costs. — AP

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