The World-First Sand Battery Begins Commercial Operation in Finland

Energy storage systems are essential for our modern, energy-hungry world, especially as we transition to using renewable energy. Humans use many energy storage forms, the most common being the ubiquitous Li-ion batteries. But batteries are not always the most efficient way to store energy, and that’s why scientists have come up with some very creative ideas. We’ve talked recently about the water battery that Switzerland built with great effort in the Alps. Still, there are also gravity batteries and even CO2 batteries.

Finland pioneered a new system that uses ordinary sand to store energy. This is a thermal energy storage system, storing heat in a sand reservoir at about 500-600 degrees Celsius (932-1112 °F). The sand is heated up using the electricity generated by solar panels and wind turbines. It can also keep its high temperature for months.

When needed, the energy is extracted from the heated sand using a heat pump to heat up buildings and swimming pools. This works very well in Finland, where house heating is centralized. The district heating system uses pipes with hot water to distribute the heat to people’s homes. The sand battery is straightforward and doesn’t require expensive components like turbines. It also has an efficiency factor of up to 99%, and it’s built to last for decades.

The sand battery was built by Polar Night Energy for Vatajankoski, a “new energy” company located a few hours out of Helsinki. The company uses heat from local data servers to offer district heating to surrounding areas. The sand battery can significantly enhance this system, supplementing the heat when needed. The isolated tank used to store the sand measures around 4 meters (13.1 ft) wide and 7 meters (23 ft) high and can store up to 8 MWh of energy.

“It’s really easy to convert electricity into heat,” said Polar Night CTO Markku Ylönen in a video interview with Disruptive Investing. “But going back from heat to electricity, that’s where you need turbines and more complex things. As long as we’re just using the heat as heat, it stays really simple.”

Sand is a very low-cost and environmentally friendly solution. Polar Night Energy claims the setup costs are less than $10 per kWh. The sand battery uses no consumables and runs fully automated. Although the system installed at Vatajankoski’s headquarters only yields 8 MWh, the same technology can scale up to 20 GWh of energy storage.

For Finland, such a system works miracles, considering that vast parts of the country see no sun for weeks on end in the winter. The long-duration storage capability of the sand battery is ideal in such conditions, significantly reducing the external energy needed to heat the buildings.

The sand offers considerable advantages over liquid-storage solutions like molten salt or water. For instance, it allows multiple heating zones inside the sand storage. This can be used to build long-term storage toward the center of the sand cylinder, while short-term repeated use cycles can be isolated closer to the surface.