The Durst Organization Manhatten, New York

What is Off-Peak Cooling (OPC)? CALMAC’s Off-Peak Cooling systems (OPC) utilize a standard packaged chiller to produce ice during the night and store it in modular ICEBANK® thermal-energy storage tanks. The stored ice provides cooling the following day to meet the building’s air-conditioning requirement.

Why should building owners and engineers consider OPC for retrofit applications?

• Installed costs of a partial storage OPC system can be comparable to conventional cooling while operating costs can be reduced up to 40 percent.
• Smaller chillers, cooling towers, and ancillary equipment can be used with partial-storage systems.
• Colder supply temperatures available from storage can help reduce pumping costs.
• Ideal for building expansions because instead of adding costly electrical and chiller capacity to cool the additional load from the new building space, ICEBANK tanks work in conjunction with the existing equipment to meet the increased cooling load.
• OPC provides other benefits such as quantifiable return on investment and conservation of our valuable natural resources.

A good retrofit example was the project for the The Durst Organization at 1155 Avenue of the Americas, New York City, a major commercial landlord in Manhattan. The project was profiled in The New York Times and involved the installation of 28 CALMAC ICEBANK tanks to work in conjunction with a 700-ton chiller.

The chiller and the ICEBANK tanks share the cooling load during the on-peak daytime hours, and then work together to store ice during off-peak nighttime rates. This partial storage strategy has significantly reduced the Durst Organization’s energy costs.

Underwriters Laboratories Inc. (UL) chose off-peak cooling for the energy efficiency and operating flexibility it provided. Since the installation of Off-peak cooling in 2001, they have saved $350,000 on their utility bill annually . “Overall, the new system reduced operating cost from $0.14 to $0.066 per ton-hr”, a 52% savings according to Volker Kotscha, UL's Director Of Facilities Operation. This air-conditioning system is entirely redundant. “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 Volker, Kotscha.

Click here (PDF, 114 Kb) for more detailed information regarding the Durst Organization project.

CALMAC also developed a process of retrofitting a building’s existing rooftop units, which can result in a 43 percent reduction in demand charges and a 12 percent drop in total energy usage.

We also encourage you to fill out our thermal storage analysis form, and a member of our team will contact you with an evaluation of your facility.

Within this site you can learn more about CALMAC’s OPC systems and the specific benefits that this type of HVAC system can provide for you.