Underwriters Lab Banks on Ice
An ice-storage system from Calmac provides cooling while it conserves energy.
Underwriters Laboratories Inc. (UL), Northbrook, IL, is an independent, not-for-profit, product-safety testing and certification organization. Managers took a close look at the facility's cooling system and determined the time was right to replace the entire system, if it could be done with minimal interruption to the daily operation. The engineering firm of Sebesta Blomberg (SB), Roseville, MN, was commissioned to design a system that was flexible, efficient, easy to operate, and allowed room for expansion. It also had to be affordable and last 25 yr.
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| Fifty tanks for the ice-storage cooling system were set in place within three days. |
Thermal storage, off-peak cooling
SB designed 8,000-ton hr. of thermal storage into the system with two screw chillers that could make ice, chilled water, or both at the same time, using low-cost, off-peak energy at night. Ice- storage cooling allowed UL to drop 400 to 800 hp each day from its daytime cooling demand, when energy is most expensive.
The project uses an ice storage system from Calmac Mfg. Corp., Fair Lawn, NJ. The system uses 50 Model 1190C tanks for a total of 8,000-ton hr., the optimum size to complement mechanical cooling and fit into the available space. The modular design allowed individual tanks to be lowered into an existing area well and slid into the basement, eliminating building modifications that would have been necessary to transport the tanks down main hallways. Fifty tanks, each measuring 7 1/2 ft. dia. x 8 1/2 ft. tall, and weighing 1 ton empty, were set and temporarily bolted together in three days.
"Overall, the new system reduced operating cost from 14 cents/ton to 0.066 cents/ton," a 52% savings, according to Volker Kotscha, UL's director of facilities operation.
An additional building houses two 800-ton chillers to cool the facility during ice production, and adds flexibility and redundancy to the system. "We can cool the entire facility with ice for a minimum of six hours to take advantage of any energy-curtailment incentive windows offered by the local utility," said Kotscha. "And we can produce 8,000 tons of ice in six hours to take advantage of nighttime energy incentives starting to appear in the market."
SB completed installation of the Calmac system on schedule and made ice the first time the equipment came online. UL had a fully charged thermal-storage system within days. "This really helped the project to finish on time and allowed UL to realize energy savings from day one," said Samuel McCoy, UL facilities technician.
SB estimates UL will save $10 to $11 million in operating costs over the next 25 yr. and help the environment at the same time.
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