How Thermal Storage Works

Thermal energy storage is like a battery for a building’s air-conditioning system. It uses standard cooling equipment, plus an energy storage tank to shift all or a portion of a building’s cooling needs to off-peak, night time hours. During off-peak hours, ice is made and stored inside IceBank energy storage tanks. The stored ice is then used to cool the building occupants the next day.

Ice at Party, A Simple Metaphor

Imagine holding a party. You’re not likely to make ice the moment people arrive. You couldn’t make it fast enough. You’d buy or make ice ahead of time, store it in your freezer, and use it as needed. The promise of thermal energy storage is similar, with this important stipulation. You still make the ice ahead of time, at night. But, the electricity you use to make that ice, is far less expensive at night than it is during the day.

(Hover over the graphic below to see how energy storage works.)

Step 1

During night time, off-peak hours, water that contains 25% ethylene or propylene glycol is cooled by a chiller. That solution circulates inside the heat exchanger within the IceBank tank, freezing 95% of the water that surrounds the heat exchanger inside the tank. The water surrounding the heat exchanger never leaves the tank.

Step 2

Ice is created uniformly inside the IceBank tank via CALMAC’s, counter-flow-heat exchanger tubes. As ice forms, water still moves freely, which prevents damage to the tank. To fully charge an IceBank tank takes from six to 12 hours.

Step 3

During the day-time on peak hours, the glycol solution circulates through the ice storage tanks to deliver the stored energy to the building to augment or offset electric chiller cooling.  The cold glycol is delivered at the proper temperature to the cooling coil in an air handler. 

Step 4

A fan blows air over the coils to deliver cooling to the occupant spaces.  People feel cool and comfortable and never know ice storage is being used to save money on cooling costs.