Polar Night Energy: The World's First Commercial Sand Battery Begins Energy Storage in Finland

The world’s first commercial sand battery system is now in operation in Western Finland.

Polar Night Energy just built a giant battery out of the sand

Using renewable energy to make sand really hot

On the edge of a small town in Western Finland, a startup called Polar Night Energy worked with a local utility to pioneer something that doesn’t exist anywhere else in the world: a giant sand battery. It’s what it sounds like: A tower filled with 100 tons of sand, designed to be super-heated with renewable electricity that can store the heat for months, so the power generated in the summer could later be used to heat homes in the winter.

The main purpose of the design “is to enable the upscaling of solar and wind,” says Markku Ylönen, cofounder and CTO of the startup. As renewable energy grows, so does the mismatch between production and demand; solar and wind farms now often generate much more electricity than the grid needs, but only at specific moments. At other times, when the sun isn’t shining or the wind isn’t blowing, the grid has to turn to other sources. The energy could be stored in lithium-ion batteries, but they are still relatively expensive. Polar Night Energy isn’t solving the problem of how to store electricity cheaply, since it’s inefficient to turn electricity into heat and then back into electricity. But storing renewably-powered heat long-term, it’s helping reduce another source of emissions.

At factories, the sand batteries could help store heat for industrial processes that require high temperatures and currently run-on fossil fuels. The sand can be heated to 400 degrees Celsius (752 Fahrenheit), and with some tweaks to the pipes and other materials in the system, it could store and provide heat up to 700 or 800 degrees Celsius. The basic approach is simple. Inside a strong container—either a silo with extra-thick walls or an underground space, potentially built in an old mine—a giant pile of sand can be heated with hot air blowing through pipes. When the sand is extremely hot, it naturally retains the heat until it’s ready for use.

Sand is an ideal material for the purpose. “It’s something that’s available everywhere,” says Ylönen. “It’s cheap, and you can build large storage for scaling it up.” Other cheap materials can also store heat, like water, but sand has the advantage of being able to reach much higher temperatures. The company can also use the lowest grade of sand, which wouldn’t be used in the construction industry.

The premises of a “new energy” company, Vatajankowski, a few hours out of Helsinki, Finland is using this stored heat, in conjunction with excess heat from its own data servers, to feed the local district heating system, which uses piped water to transmit heat around the area. It can then be used to heat buildings, swimming pools, industrial processes, or in any other situation that requires heat.

This helps make it extremely efficient, the company said. “It’s really easy to convert electricity into heat,” says Ylönen. “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 an efficiency factor of up to 99 percent, a capability to store heat with minimal loss for months on end, and a lifespan of decades.

How the world’s first sand battery stores green power – BBC News

Parts of Northern Finland see no sun at all during the winter, since they’re above the latitude (~68 degrees north) where there’s no direct sun at all for weeks on end through the depths of winter. This sand battery, says the company, will have its greatest impact during periods like this when its long-duration storage will keep buildings heated cheaply and cleanly through the freezing Finnish winter.

As such, Mission Innovation’s climate solutions framework has estimated that deploying Polar Night’s energy storage system to its full potential could replace enough carbon-burning heat sources to reduce annual greenhouse emissions by somewhere between 57 and 283 megatons of CO2 equivalent per year by 2030. That would be a pretty significant contribution.

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