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Store Up Energy

Wednesday, March 04, 2015
Energy Storage

Written by an Engineer at Ahern

Thermal energy storage is a beneficial system that allows you to reduce your total electricity demand charges. In general, this is simply done by operating your cooling equipment during off-peak hours (weekends and nights) and storing the energy to be used later during expensive on-peak hours. There are a few other benefits to this type of system in addition to the energy cost savings.

  • With the additional capacity from the thermal energy storage you are able to reduce the size of the building’s cooling equipment, or it can be used as additional/backup capacity in an existing system.
  • When shifting the majority of the building’s energy use to off-peak hours at night, the cooling equipment will operate more efficiently at the lower condensing temperatures.
  • You also could receive utility rebates or incentives if a large amount of energy is shifted.

While there are a few different applications of thermal energy storage that will meet these benefits, such as a chilled water storage system, but typically an ice storage system is preferred. Ice storage in comparison to water storage can store far more energy in a smaller tank. Water storage guidelines range from 0.5 to 1gal/ft2 of conditioned space, while ice storage range from 0.13 to 0.25 gal/ft2 of conditioned space.1

When it comes to how the ice is made, there are a few different methods of how it’s created and stored. Some of the options are described briefly below:

  • Ice is formed on a closed loop refrigerant pipe that is routed through an ice tank (See Figure 1)
  • Ice is formed and thawed by circulating a low-temperature brine through coils.
  • Ice harvesters, which collect ice formed on plates.

There are a few other applications that ice storage can be used for such as creating a lower supply air temperature or for creating a low humidity level, but primarily it is used to create an energy cost savings.

If you’d like to learn more, contact Ahern today to see if an ice storage system is an ideal application for your project.

1 Stein, Benjamin, and John Reynolds. "Central Equipment." Mechanical and Electrical Equipment for Buildings. 11th ed. New York: J. Wiley & Sons, 2010. 421. Print.


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