Surely this can be applied here in Chicago, right?
Enwave and the City of Toronto have created an innovative cooling system that brings an alternative to conventional air conditioning to cool Toronto's downtown core — one that is clean, price competitive and energy efficient. A permanent layer of icy-cold (4°C) water 83 meters below the surface of Lake Ontario provides naturally cold water. This water is the renewable source of energy that Enwave's leading-edge technology uses to cool office towers, sports & entertainment complexes and proposed waterfront developments.
The system has been in operation since 2004.
A similar form of air condition is being used in Halifax, Nova Scotia. At Purdy's Wharf, we read here, it “provides all the cooling for the building for 10 ½ of the year. During the remaining six weeks, the buildings use conventional chillers, but the seawater is used to cool the condensers. The system was paid off in two years, and saves the complex more than $100,000 annually in electricity and maintenance costs.”
In the U.S., Cornell University is implementing its own deep lake water cooling system.
Wikipedia has an entry, of course.