Empa's system is different because it stores heat in the form of chemical energy. The secret ingredient: chemical sodium hydroxide, also known as lye.
The setup consists of two main components, plastic storage tanks that hold the chemicals and a unit designed to charge and discharge the contained heat. The storage tanks contain the sodium hydroxide mixed with water. During the charging process, heat energy harvested from a renewable source, such as a solar thermal collector, is directed to the sodium hydroxide solution. As the solution absorbs the heat, the water evaporates.
The sodium hydroxide solution becomes more concentrated and can be stored like this for months or even years. What's more, it's heat storage capacity is five-times that of a hot water tank, which greatly reduces the space needed to contain the heat.
When water is added back into the condensed solution, the absorbed heat is released. That heat can be transported via pipes into the building's main heat system, delivering warmth to the rooms.
"We have succeeded in building an operational lab scale absorption heat storage system operating at the full potential," Fumey said. Empa has had a prototype of the solar-powered system running for about a year now.
Someday in the future, homeowners might be able to tap this new technology to save money on their winter heating bills.
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