The researchers at TU Wien use heat to trigger a chemical reaction. This produces energy-rich chemical compounds that can be stored for months without any problems or loss of energy. When needed, the chemical reaction can then be reversed, releasing the energy again. For example, waste heat from industrial plants or solar heat can be stored in the summer and used to heat buildings throughout the winter. The chemical reaction and the suspension reactor specially developed for it ghave now been patented.

The new method is based on converting heat energy into chemical energy and back again. "There are different chemical reactions that can be used for this purpose. For example, we use boric acid, a solid material, which we mix with oil," explains Professor Franz Winter of TU Wien. "This oily suspension goes into a reactor whose wall is heated to a temperature between 70 °C and 200 °C."

Ideally suited for industrial waste heat

Many processes in industry take place in this temperature range, so this method is ideally suited to utilizing waste heat from industrial plants that would otherwise simply be lost. However, such temperatures can also be achieved simply by concentrating sunlight.

The heat causes a chemical reaction - for example, boric acid is converted into boric oxide, and water is released in the process. The oily boric oxide suspension can then be stored in tanks. If water is then added to this suspension again, the chemical reaction takes place in reverse, and the stored heat is released again.