Toronto turns to lake water for air conditioning

Cold water drawn from Lake Ontario cools buildings and provides big energy savings.

from the August 30, 2007 edition

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Significant energy savings during peak periods

In the early 20th century, movie theaters provided air conditioning by blowing air over melting blocks of ice, which would cool the audience. Melting one ton of ice per hour is equal to one ton-hour of air conditioning. Using that measurement, the entire project has a cooling load of 54,493 ton-hours, enough to cool 27,000 houses.

But the electric utility prefers to measure the benefits in megawatts saved.

The two newer TD towers, modeled after van der Rohe's designs, were connected to the system last fall. For the first time this past summer, the entire TD Centre was air-conditioned by the water pulled in from Lake Ontario, saving a total of 10 megawatts of electricity during peak periods. Another 12 megawatts are similarly saved from connections to the Royal Bank Plaza and the Metro Centre, home to the local city government. All those buildings are close to Lake Ontario.

Perhaps the most ambitious connection is Queen's Park, seat of the provincial government, located about two miles from the lake. The legislature and some nearby government office buildings were connected in April, saving four megawatts of electricity.

New buildings that join the Deep Lake Water Cooling System should never have to build cooling units. Among them is a 25-story condominium complex built by Tridel, a local developer, in downtown Toronto. It was hooked into the project from the start.

The system has other benefits besides saving energy. Most office and apartment towers have cooling units on their roofs. Removing them means the roof can be used for something else, perhaps a running track. The three original van der Rohe towers have cooling units built between floors, appearing as black, windowless bands from the outside. The owner is now working out how to convert those areas into office space, which is almost as precious as electricity in downtown Toronto.

Still, the largest benefit created by the cooling system has been to reduce the city's demand for electricity during in the peak summer season. The two transformer stations at each end of Toronto's financial district has been hard-pressed to keep up with demand from computers, lighting, and air conditioning.

"Toronto Hydro gives Enwave a check every time we sign a new building on their grid," says Enwave's Mr. Loughborough. "We call it 'nega-watts,' where instead of creating new generating capacity, you lower the demand for power."

Other cities could benefit from similar systems

Toronto's cooling project is the largest of its kind in the world and the only one that offers both drinking water and cooling. Other cities use similar cooling systems: In Sweden, Stockholm's system, which uses cold ocean water, is about two-thirds the size of Toronto's.

Other cities that might benefit for using cold offshore water:

Chicago: The city has harsher winters than Toronto and sits beside frigid Lake Michigan. But Lake Michigan is shallower than Lake Ontario. To reach cold, deep water, it would have to lay pipes out 19 miles, six times the distance of Toronto's system.

Tokyo: It has deep water in Tokyo Bay, but hasn't done anything to try to exploit it for cooling yet.

Geneva: It's an ideal candidate, as Lake Geneva is cold and deep. It has inquired about the system.

New York: The city has contacted Enwave engineers, but the ocean off New York is too shallow. There are opportunities for a smaller system in upstate New York, however. Cornell University in Ithaca, N.Y., runs a cooling system similar to Toronto's, using Lake Cayuga as a source.

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