Moving toward net-zero carbon emissions means dealing with the intermittent, unpredictable nature of green power sources such as wind and solar. These intermittent renewables don’t produce energy around the clock, so the green energy transition will require huge amounts of energy storage.
Polar Night Energy and Vatajankoski, an energy utility based in Western Finland, have installed sand-based thermal energy storage, the world’s first commercial solution to store electricity in the sand as heat to be used in a district heating network. The sand battery, which has a hundred tons of sand inside, is placed in Vatajankoski’s power plant area, and it provides heat for Vatajankoski’s district heating network in Kankaanpää.
The sand-based thermal energy storage is about meters wide and 7 meters high steel container that has an automated heat storage system and a hundred tons of sand inside. Sand can store a lot of heat in a small volume at a temperature of about 500–600 degrees Celsius, which can then warm homes in winter when energy is more expensive. The device is capable of storing an impressive 8 megawatt-hours of energy at a nominal power rating of 100 kW.
Vatajankoski is using the heat provided by the storage to prime the waste heat recovered from their data servers which are intended for high-performance computing. Depending on the season, the temperature of the 60-degree waste heat from the servers must be raised to 75–100 degrees before it is fed into the district heating network.
“The construction of the storage went well, especially considering that the solution is completely new. We managed to get everything in order despite some challenges and a short delay. Now the sand is already hot,” says Polar Night Energy’s Co-Founder and CTO Markku Ylönen. “We have already learned that our system has even more potential than we initially calculated. It’s been a positive surprise.”
This innovation is a part of the smart and green energy transition. Heat storage can significantly help to increase intermittent renewables in the electrical grid. At the same time, we can prime the waste heat to a usable level to heat a city. This is a logical step towards combustion-free heat production, says Ylönen.