Iced Coffee? Iced Tea? How About Ice for Campus Air Conditioning?

It’s the time of year when many peoples’ thoughts turn to air conditioning. Most college and university employees take it for granted, but with energy prices continuing to rise, those responsible for paying the bills are painfully aware of what a luxury all that cool air has become: The chillers that produce cold water to operate large-scale air-conditioning systems are among any college’s biggest users of energy, and they typically run most when electric costs are highest—on summer afternoons. So some colleges have turned to a pretty basic technology to save money.

It’s called “ice.”

The strategy is so simple a kid could understand it: A college runs its chillers at night, when electricity prices are lowest, and makes ice in big, insulated tanks. Then, as the day heats up, water for the chilled-water lines is run through the ice facility, rather than through the chillers. The University of Arizona, which has just installed a second ice plant, expects it to lower the university’s electric bills by $30,000 a month. The University of Pennsylvania and Cornell University are among other institutions that make ice at night and use it for air conditioning during the day.

In addition to saving money, using an ice-based system can be significantly more sustainable than running chillers during peak periods. That’s because electric utilities run their most efficient generating plants around the clock, bringing less-efficient plants online as demand increases. Ice made at night is, in all probability, made with electricity that has less of a carbon footprint than the electricity that would run chillers on a July afternoon. (Not all chillers run off electricity, however—some are fired by natural gas, while others are driven with steam from campus boilers.)

Cornell also takes advantage of an even more inventive air-conditioning strategy—it siphons cold water up from the chilly depths of Cayuga Lake and runs the water through heat exchangers that cool water for the campus chilled-water loop. Although the infrastructure was expensive to build, rising energy costs make the $60-million initial investment look more attractive every day.