An ice-ball storage cooling system for a laboratory complex

An ice-ball storage cooling system with a 30,000-gal (113.55-m 3 ) storage tank containing 125,000 dimpled plastic balls has been in successful operation to cool the main complex of the US Army Engineer Research and Development Center, Construction Engineering Research Laboratory (ERDC-CERL) in Champaign, Illinois, since October 1996. The unit cools the ERDC-CERL main complex from 10:00 a.m. to 6:00 p.m. (adjustable) during the summer, excluding weekends. The nominal design storage capacity of the system is 1700 ton-h (5,974 kWh). The system uses two chillers, which were installed in the spring of 1993. The ice storage cooling system was installed in October 1996. Depending on the ice inventory, one or two 170-ton (597.4-kW) R-22 screw chillers make ice every night. This study found that turning off the chillers reduces about 200KWofon-peakelectrical demand, which resulted in about 15% to 20% electric cost savings for the four summer months. In March 2003, the ice storage tank was opened to study the ice balls for the long-term impact during the past six years of operation. This paper documents the cost benefit, discusses lessons learned from the operation and maintenance of the system, and makes recommendations for future applications.