New Ice Age: Keeping Air Cool in Office

ICE is making a comeback in cooling. No, it's not a revival of the local ice company, delivering a 50-pound block for your cooler and giving kids scraps to suck on. But office buildings may be air-conditioned increasingly by water from freshly melted ice.

Seven buildings in downtown Chicago were successfully cooled this way last summer. Last week, plans were announced in Boston for similar "district cooling systems," in which one cooling plant serves a number of large buildings.

Unicom Thermal Technologies of Chicago, the innovator of the new-old technology and a partner in the Boston deal, is planning cooperative ventures in dozens of other cities in the United States, as well as in Canada and Europe.

Each night, the Chicago plant freezes 5 million pounds of giant ice cubes, using off-peak, hence cheaper, electricity. The ice melts slowly during the day and the 34-degree water is piped to participating buildings where it cools the air. The water, flowing in a closed loop, returns to the plant for refreezing.

"This technology is good for the world's environment in several ways," says Donald Petkus, Unicom Thermal's chief executive. First is the use of off-peak power at night. During the day in summers, power demand can be so high that inefficient, coal-burning power plants are started up, spewing extra hydrocarbons into the air.

"The relative efficiency of this one ice plant ... saves enough electricity in one day to meet the needs of 10,000 homes for that day," says Joe King of Unicom Thermal. Another environmental boon: The coolant that freezes the ice uses hydro-chlorofluorocarbons (HCFCs), which are less damaging to the earth's protective ozone layer than chlorofluorocarbons (CFCs), which can no longer be manufactured legally.

Unicom Thermal is a spinoff of Commonwealth Edison Company, which provides power in northern Illinois. Its Boston partner, Northwind Boston, is a unit of Boston Edison Company, another large utility. (With deregulation, utilities are entering new lines of business, sometimes competing with each other, through unregulated divisions.)

Because Boston office buildings must phase out CFC-based systems, and because many of these already use cool water, interest in the new venture should be strong, says Richard Zimbone, head of Northwind Boston.

"The capital risk in cooling can be shifted to us; we offer a 20-year contract with price predictability," he says.

For now, Chicago's is the only such system using ice-storage technology, but Minneapolis-St. Paul, Cleveland, and Hartford, Conn., have district cooling systems that cool water to about 45 degrees and circulate it.