Polar Night Energy designs and builds high temperature and low-emission heat storage. The patented long-term storage solution of PNE uses sand as a storage medium. Excess and thus affordable electricity from, for example, a wind farm is used for heating up the sand to a high temperature, typically 500 - 600 °C. Later, the stored energy can be used as heat for different kinds of purposes from industrial steam production to district heating. The possibility of converting the stored heat back to electricity is also investigated in the NewSETS project.

The heat transfer to and from the storage medium is done via a patented pipe system, which is already successfully demonstrated in Polar Night Energy’s 3 MWh pilot plant in Hiedanranta, Tampere, Finland. Having sand as a heat storage medium instead of conventionally used water provides several benefits, e.g. three times better volumetric heat capacity and higher output temperatures. The heat storage studied in this project has a capacity of 500 MWh. The storages have no technical limitations for scaling up to any size, although several hundred GWh is a practical limit.