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Renewable Energy News

THURSDAY 19 NOVEMBER, 2009 |

Ice Battery - Renewable Energy Storage

by Energy Matters

Ice battery - thermal energy storage tank

During 2009, we've reported on all sorts of possible alternatives to traditional deep cycle batteries for renewable energy storage - such as the lithium air battery, liquid batteries, the Beltway battery, molten salt batteries, the cavern battery and even a virus battery.

Introducing another possibility - the ice battery - and it's already on the market.

Air conditioning during the summer can be the largest single contributor to a building's energy cost. A hybrid cooling system from Calmac uses an ice bank thermal energy storage tank to make and store ice for use in air conditioning systems when the wind isn't blowing or the sun isn't shining - such as after dark.

For buildings without on-site renewable energy power generation, the ice can be made at night during off-peak times when electricity rates are cheaper and when cleaner baseload generation is used. In this scenario, Calmac says their system can reduce cooling costs by up to 40 percent.

According to Calmac, for every kilowatt-hour of energy that is shifted from on-peak usage to off-peak, there is a reduction in the source fuel needed to generate it - between 8 and 30%.

The IceBank tanks are made of heavily insulated polyethylene and contain a spiral-wound, polyethylene-tube heat exchanger surrounded with water. The tanks are available in a variety of sizes ranging from 45 to over 500 ton-hours.

During the charging cycle, a solution containing 25 percent ethylene or propylene glycol is cooled by a chiller and then circulated through the heat exchanger inside the IceBank tank. The ethylene-based or propylene-based glycol recommended for the solution is an industrial coolant that is specially formulated for low viscosity and superior heat-transfer properties.

The ice is built uniformly throughout the tank during the charging process and a full charging cycle of an IceBank tank requires approximately 6 to 12 hours, which makes it viable to be used in conjunction with a solar panel array.