Finnish company Polar Night Energy has announced an agreement to build a second sand thermal storage facility in the country. It will still be an experimental facility, where new solutions will be tested, including operation at higher storage temperatures.
Image source: Polar Night Energy
The first Polar Night Energy installation with a peak power of 1 MW and a storage capacity of 100 MWh is currently completing its winter testing phase in Pornainen, southern Finland. The installation converts electricity from solar and wind power plants into heat and stores it in a layer of sand. The sand tank is 15 m in diameter and 13 m high and contains 2,000 t of sand.
However, sand was only used in the 100 kW pilot plant built by the company in 2022. The heat accumulator in Pornainen used soapstone (talc chlorite) as a heat storage medium – a waste product from the local production of facing material for stoves, saunas and fireplaces. It has a higher heat capacity and therefore performs its function as a heat storage medium better.
Polar Night Energy has agreed to build a second large-scale sand-based heat storage facility in Valkeakoski, also in southern Finland, in cooperation with the city’s energy company Valkeakosken Energia. Construction is expected to begin in the fall of 2025 and be completed in about a year. The developer plans to implement a number of innovations at the new site, including maintaining a higher temperature for the heat storage unit to improve the efficiency of the entire system. Working out the details of the improved technology will allow the company to move on to building utility-scale installations.