Feature Article

Buildings on Ice: Making the Case for Thermal Energy Storage

June 30, 2009

But it was a feature hidden away in a sub-basement that I went to see recently: the building’s thermal energy storage (TES) system. Along with Mark MacCracken, P.E., the CEO of Calmac Manufacturing, which created the system, I entered through the building’s temporary scaffolding and slipped through a nondescript door in the lobby, leaving the building’s daylit grandeur for a catacomb of hidden hallways and stairways. Escorted by assistant chief engineer Dan Monahan of The Durst Organization, we dropped three floors from street level to a sprawling mechanical room with massive chillers, pumps, color-coded pipes of all sizes, and—what we had come to see—the 44 neatly arranged tanks where ice is made each night and melted each day to help cool the 2.1 million-square-foot (195,000 m2) tower.

Each of the 8'-diameter, 8½"-tall (2.4 x 2.6 m) insulated tanks holds over 1,600 gallons (6,100 l) of water and three miles (4.8 km) of plastic tubing through which 150 gallons (570 l) of glycol solution flows. When the water is frozen at night, each of these tanks holds 162 ton-hours (570 kWh) of cooling capacity, enough to provide cooling for about 10,000–12,000 ft2 (930–1,100 m2) of office space, according to MacCracken.