Researchers in Europe have developed a compact heat storage unit that could change how heat pumps are used in homes and small buildings, tells Tech Xplore. Traditional heat pumps move heat from air, ground, or water into a house, but they have never stored that heat efficiently for later use. The new system acts like a thermal battery: it charges when electricity is cheap or abundant and releases heat when it’s needed. This makes heat pumps more flexible, easier to use, and better at matching demand patterns in real life without constant operation.
At the heart of this innovation is a class of materials called salt hydrates. Unlike common table salt, these materials change phase, that is, solid to liquid and back, when heated or cooled. That phase change lets them store far more energy per unit of volume than water. Salt hydrate systems also retain heat more steadily, a benefit when usage varies through the day or night. Because the storage unit can be several times smaller than a standard hot water tank, it fits more easily into existing homes.
The researchers increased efficiency and performance by using thin cooling fins made from recycled aluminum. These fins spread heat quickly through the salt hydrate, boosting charging efficiency from around 65% to about 85% and cutting charge and discharge times dramatically. To protect the aluminum from corrosion in contact with salt hydrates, the team applied a durable ceramic coating through a plasma electrolytic oxidation process.
The development came out of a multi-partner effort involving the Norwegian research institute SINTEF and the Swiss company COWA Thermal Solutions. It’s part of a broader project aimed at advancing thermal energy storage technologies for buildings. By combining heat pumps with smart heat storage, homeowners could use electricity more economically and reduce stress on power grids, especially when demand peaks or renewable generation varies.