Do you know your cost for on-peak cooling? Chances are it’s at least double your off-peak rates. Using technologies that leverage this difference can ease the burden on your pocketbook.
Thermal energy storage (TES) is a method by which energy is produced and stored at one time period for use during a different time period. The most common application in the U.S. is for cooling and entails making chilled water or ice during off-peak times (at night) and storing it for use during peak demand (the next day). By shifting energy use, a thermal storage system can lower operation and maintenance costs and reduce equipment size.
Building type, space available for storage, and existing equipment status will affect implementation of TES. Thermal storage for off-peak cooling is a proven, simple, and practical solution to rising energy costs, but can it work for you? Let these factors help you decide if the time is right for thermal storage.
Where To Begin
If your application is for a new construction project, TES can be considered from the very beginning. If you’re evaluating thermal storage for a retrofit, other triggering events will make the project more feasible and provide a more attractive payback period.
Start by studying your electric rates. “Utility bills can be confusing. Be aware of the peak demand charge,” advises Mark M. MacCracken, president and CEO of CALMAC Manufacturing, a provider of thermal energy systems. “Every rate I’ve seen for commercial buildings turns out to be 50-60% less at night, and that may not be evident at first glance. You have to study it – or have a consultant study it and give it back to you in English.”
The electricity you buy during the hottest part of the day can cost nearly three times as much as the power you could buy in the middle of the night, says John S. Andrepont, president and founder of thermal storage consulting firm The Cool Solutions Company.
“Usually, you will get at least an annual savings of $100-150 for every kilowatt of peak demand reduction,” Andrepont explains. Because TES can save thousands of kilowatts, there is potential to save hundreds of thousands of dollars.
Some local electric utilities pay one-time cash incentives to customers that install and operate TES equipment – usually a fixed amount of several hundred dollars per kilowatt of load reduction during a defined on-peak period of several hours per day, Andrepont says.
“In the most attractive cases, TES can be economically justified even as a pure retrofit,” adds Andrepont. “But TES economics are always better during times when a TES investment offsets an otherwise necessary investment in conventional chiller plant capacity – whether that’s new construction, retrofit expansion, or retirement of existing chillers.”