Aside from traditional large-scale li-ion battery energy storage systems, there are many other solutions, and Finland managed to create the first commercial “sand battery” recently.

Energy storage systems are diversified, such as flow battery, molten salt battery, gravity battery, and carbon dioxide battery. Each solution comes with its own advantages and disadvantages pertaining to efficiency, dimension of devices, installation and operating cost, lifespan, and energy capacity.

Finland-based Polar Night Energy’s sand battery is a heat storage system, where an insulated steel cylinder measuring at 4m in diameter and 7m in height is filled with sand, and the sand is then heated to 500-600°C, with the heat exchanger providing 8MWh of energy and 100kW of rated power.

The company has established the first commercial sand battery at Vatajankoski, a company located several hours of drive outside of Helsinki. The heat storage system and the excess heat from Vatajankoski’s in-house servers are used to provide heat for local buildings, swimming pools, industrial places, and other venues that require thermal energy.

Markku Ylönen, CEO of Polar Night Energy, commented, “It's really easy to convert electricity into heat. 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. ” The company claims that the system has an efficiency factor of 99%, and is able to store several consecutive months of thermal energy under minimum losses, with a lifespan that can go up to few decades.

The cost of the system is also very affordable since the main material is ordinary sand, and only needs to be kept and without any combustible matters. Polar Night Energy claims that the establishment cost is below EU€10/kWh, and the automatic operation does not require any consumables

The company also plans to enlarge the installation scale in the future by establishing 20GWh energy storage devices. Should the shape fit, large underground energy storage facilities can be built at abandoned mines without any high pressure vessel, and the most expensive segment would be pipelines instead of the energy storage equipment.

The reason for the company to build such energy storage systems has something to do with its name Polar Night. Finland is a high latitude country, roughly 68 degrees north latitude at the northern forest, and will not see any sunlight for several consecutive weeks during the wintertime, which is why Polar Night Energy hopes that the sand battery is able to provide affordable and clean heat during winter.

(Cover photo source: Polar Night Energy)