Builders See Ice as Cool Alternative to Air Conditioners
Back around the turn of the century, they air-conditioned theaters by fanning air across giant blocks of winter ice that had been stored underground until the summer.
Now ice conditioning--the high-tech variety--is back, and its promoters say it will save energy and help phase out ozone-depleting chemicals.
Office buildings in Chicago’s Loop already are cooled by a central plant filled with 5 million pounds of giant ice cubes. Boston is next.
Northwind Boston plans to build three downtown cooling plants at a cost of $60 million. The company was formed in January by subsidiaries of Boston Edison Co. and Unicom Corp. of Chicago.
The plants freeze large blocks of ice at night, when electricity demand is low and the price cheap. During the day, as the ice melts, the cold water is pumped to the buildings. The process begins all over again after dark.
The first plant, due to be hooked up next year, could cool up to 10 buildings the size of Boston’s largest without using chlorofluorocarbons, or CFCs. The manufacture of CFCs was discontinued this year because of concern over the shrinking ozone layer.
“We’re offering these owners an alternative to changing refrigerants or replacing their whole chiller system,” said Rick Zimbone, president of Boston Energies Technology Group, the Boston Edison subsidiary participating in Northwind.
By eliminating their own air-conditioning units, building owners could save on maintenance. Northwind’s cost would be comparable to installing a new system.
A four-story plant in Chicago owned by Unicom Thermal Technologies began pumping cooled water to Chicago office buildings in the spring, just in time for a killer heat wave during the summer.
“It worked great for us. It kept up all summer long,” said Rich Penner, who works in one of those buildings as a supervisor at Inland Steel Co. “It was a very smooth transition.”
The 19-story building is one of nine connected by underground pipes to the Adams Street plant. Two more plants are under construction.
The Adams Street cooling plant covers half a city block. Above the Osco Drug store on the ground floor, a network of chillers and pumps gives way to two stories of ice tanks. Each tank is the size of a tractor-trailer and contains four miles of tubing that freezes the water.
“If you were to cut off the roof of the building and look down from the top, it wouldn’t look a whole lot different than an ice cube tray,” said Joe King, a spokesman for Unicom, which also owns Commonwealth Edison.
The 34-degree water from the plant is piped to a heat-transfer station in each building. The heat-transfer station, the size of a couple of desks, draws cold out of the water. The warm water is then looped back to the cooling plant.
The system planned for Boston would use hydro-chlorofluorocarbons, or HCFCs, as a coolant.
That means it would still emit chlorine into the air, although less than if it used CFCs, according to Gerald Wilson, a professor of electrical engineering at the Massachusetts Institute of Technology.
“It’s not fundamentally different. So the claim that it’s better for the ozone layer is debatable,” Wilson said. “They’re not out of the woods yet on the ozone.”
Wilson said the biggest advantage to the plant is that it uses nearly all of its electricity during off-peak hours. Power produced off-peak is cleaner and cheaper.
“The downside here is that they are still using electricity,” he said.
