A pilot plant developed by Polar Night Energy has been operating since 2022, and now an industrial (10 times larger) «sand battery» is to be launched in Finland for use during cold polar nights.
New Atlas describes design, such as a large steel bunker with sand (or similar solid material) that is heated through a heat exchanger embedded in the center, using excess electricity from the grid — for example, that generated during a surge in renewable energy sources.
This energy can be stored for months with very little loss until it is used when needed. In Finland, the new sand battery will be tested in the district heating system of the Finnish municipality of Pornainen, which is operated by Loviisan Lämpö.
The sand battery is expected to measure 13 meters in height and 15 meters in width, and will have a capacity of 1 MW and a storage capacity of up to 100 MWh — which, according to the company, is equal to Pornainen’s weekly heat demand in winter or a month’s worth in summer. For comparison, the previous Polar Night sand battery measures 4 x 7 meters with a rated power of 100 kW and a capacity of 8 MWh.
The new battery is also expected to reduce carbon dioxide emissions in the district heating system by 160 tons per year, or almost 70%. The sand itself will also be sourced from environmentally friendly sources — it will consist of crushed soapstone, which is a by-product of another local industry.
Polar Night Energy said that construction and testing of the new sand battery will be completed in about 13 months.