A Tiny Town Is Betting on a Sand Battery to Heat Homes. It Could Revolutionize Energy.
A 1-megawatt sand battery that can store up to 100 megawatt hours of thermal energy will be 10 times larger than a prototype already in use.
The new sand battery will eliminate the need for oil-based energy consumption for the entire town of town of Pornainen, Finland.
Sand gets charged with clean electricity and stored for use within a local grid.
Finland is doing sand batteries big. Polar Night Energy already showed off an early commercialized version of a sand battery in Kankaanpää in 2022, but a new sand battery 10 times that size is about to fully rid the town of Pornainen, Finland of its need for oil-based energy.
In cooperation with the local Finnish district heating company Loviisan Lämpö, Polar Night Energy will develop a 1-megawatt sand battery capable of storing up to 100 megawatt hours of thermal energy.
“With the sand battery,” Mikko Paajanen, CEO of Loviisan Lämpö, said in a statement, “we can significantly reduce energy produced by combustion and completely eliminate the use of oil.”
Polar Night Energy introduced the first commercial sand battery in 2022, with local energy utility Vatajankoski. “Its main purpose is to work as a high-power and high-capacity reservoir for excess wind and solar energy,” Markku Ylönen, Polar Nigh Energy’s co-founder and CTO, said in a statement at the time. “The energy is stored as heat, which can be used to heat homes, or to provide hot steam and high temperature process heat to industries that are often fossil-fuel dependent.”
That first installation in western Finland features an insulated silo made of a 23-foot-tall steel housing and filled with 110 tons of sand and heat transfer pipes. Electricity from the grid or local production allows the company to charge the sand when clean electricity is more cheaply available, typically during the middle of the night. The electrical energy is transferred to the heat storage using a closed loop air-pipe arrangement.
Sand—a high-density, low-cost material that the construction industry discards—is a solid material that can heat to well above the boiling point of water and can store several times the amount of energy of a water tank. While sand doesn’t store electricity, it stores energy in the form of heat. To mine the heat, cool air blows through pipes, heating up as it passes through the unit. It can then be used to convert water into steam or heat water in an air-to-water heat exchanger. The heat can also be converted back to electricity, albeit with electricity losses, through the use of a turbine.
In Pornainen, Paajanen believes that—just by switching to a sand battery—the town can achieve a nearly 70 percent reduction in emissions from the district heating network and keep about 160 tons of carbon dioxide out of the atmosphere annually. In addition to eliminating the usage of oil, they expect to decrease woodchip combustion by about 60 percent.
The sand battery will arrive ready for use, about 42 feet tall and 49 feet wide. The new project’s thermal storage medium is largely comprised of soapstone, a byproduct of Tulikivi’s production of heat-retaining fireplaces. It should take about 13 months to get the new project online, but once it’s up and running, the Pornainen battery will provide thermal energy storage capacity capable of meeting almost one month of summer heat demand and one week of winter heat demand without recharging.
“We want to enable the growth of renewable energy,” Paajanen said. “The sand battery is designed to participate in all Fingrid’s reserve and balancing power markets. It helps to keep the electricity grid balanced as the share of wind and solar energy in the grid increases.”
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