Thermal storage system based on sand

The world’s first commercial sand-based thermal energy storage system has been developed to back up a heating network in Finland.

Technology company Polar Night Energy and utility organisation Vatajankoski joined forces to create the system, which is adjacent to a power plant. It has 100kW heating power and 8MWh capacity, and can heat the sand up to 500-600°C through renewable energy.

The system is based around a large steel container that holds hundreds of tonnes of sand. Vatajankoski uses the system to ready the waste heat recovered from data servers to feed into the district heating network.

Polar Night Energy’s chief technology officer, Markku Ylönen, says the construction of the storage went well.

“This innovation is a part of the smart and green energy transition,” he says.

“Heat storages can significantly help to increase intermittent renewables in the electrical grid. At the same time, we can prime the waste heat to usable level to heat a city. This is a logical step towards combustion-free heat production.”

Ylönen believes this heat storage method is a more stable renewable energy source.

“Production of renewable energy sources such as wind and solar power is highly volatile,” he says. “Our technology provides a way to refine cheap and clean surplus electricity to valuable heat in an affordable way to be used when most needed.”

According to a report by the LDES Council, between 25GW and 35GW of long-duration energy storage (LDES) will be installed globally by 2025. Sand-based thermal energy storage systems are one type of LDES that will likely become commercialised in the next few years.

The system has also made mainstream news, appearing in a BBC News special.