Ice keeps some buildings cool — and green

updated 6:55 p.m. ET July 24, 2007

NEW YORK - 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, a financial services multinational corporation.

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.

3,000 systems worldwide
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.

The idea of using ice to cool rooms is a throwback to the eras before Willis Carrier devised the first air-conditioner. An early method of cooling air in India involved hanging wet grass mats over windows. In the 1800s, a physician in Florida blew air over buckets of ice to cool hospital rooms.

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

At Credit Suisse, for example, the company must cool 1.9 million square feet of office space at the historic Met Life tower.

In the basement, three main cooling rooms house chilling machines and 64 tanks that hold 800 gallons of water each. Credit Suisse has a traditional air conditioning system, but engineers use the energy-saving system first.

Easy to maintain
Construction on the system took about four months, and company engineers say it is extremely 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 Credit Suisse system.

Trane, the air conditioning arm of American Standard, also developed a system for Morgan Stanley's Westchester County offices and just completed a new system for its offices on Fifth Avenue. A new Goldman Sachs headquarters will also have ice cooling.

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