Store wind and solar power as heat in sand. Polar Night Energy has created an energy storage solution based on this idea. A first implementation of the technology also stores the excess heat of servers, making it a potentially interesting solution for backup power in remote datacenters and digital infrastructure as well.

A first sand-based thermal energy storage system has started operating in Finland. Polar Night Energy has installed its patented technology at a power plant operated by utility Vatajankoski. A steel container contains hundreds of tonnes of sand that can be heated to temperatures of 500 to 600 degrees Celsius. Sand is heated with renewable electricity and stored for use in district heating systems. Excess heat from servers is also stored in the system.

According to the Finnish company, its technology is cheap and easy to build. A maximum of 100kW of heat power can be discharged from the system, which has a total energy capacity of 8MWh, or 80 hours of storage. A system with a capacity of 8GWh is planned. The company plans to develop energy storage facilities ranging from tens to thousands of cubic meters of sand. It is also possible to locate the system underground, saving valuable space.

Polar Night Energy has developed a heat transfer system inside the sand so that energy can be transported effectively to and from the storage. According to the company, proper insulation between the storage area and the environment ensures long storage periods, up to months, with minimal heat loss.

In Hiedanranta, Tampere, the Finns are also running a 3 MWh test pilot. Several buildings in the area are heated by it through a local district heating system. During the pilot, the heat storage solution will be tested, validated, and optimized. The pilot uses a 100 square meter solar panel array as its source of electricity and is also connected to the electric grid.

The Finnish sand battery is another example of a number of pilot projects that try to develop novel and sustainable energy storage solutions. A large water tower outside Berlin is another example, which can also store energy.

Photo credit: Polar Night Energy