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There are more ways to store energy than just using batteries. Some are using fire bricks, particularly for process heat for industries that rely on high heat in manufacturing. Others propose an arrangement of massive concrete blocks that move up and down like the weights of a giant grandfather clock, converting kinetic energy to potential energy and back again. In Finland, two intrepid engineers began experimenting with a sand battery a few years ago.
As we reported when the first prototype was unveiled three years ago, the idea of a sand battery began with two Finnish engineers, Markku Ylönen and Tommi Eronen. The concept is simplicity itself. Make a really big pile of sand. Heat it with excess renewable electricity to around 500°C (932°F), then use that heat later to heat homes, factories, even swimming pools. They say the sand can stay hot for 3 months or more. The pair have founded Polar Night Energy, which constructed a prototype consisting of 100 tons of sand inside what looks like a silo in the town of Kankaanpää.
Many Americans are unfamiliar with the concept of district heating, but it is widely used in other counties, especially in Scandinavia where keeping schools, municipal buildings, arenas, factories, and homes warm in winter is a challenge.
Loviisan Lämpö is a Finnish district heating company that supplies district heating to customers in Loviisa, Pukkila, Pornainen, and Pyhtää. It has collaborated with Polar Night on a new sand battery — one that is much larger than the prototype — which began operating in the city of Pornainen in southern Finland this month, where it is expected to reduce carbon emissions from district heating by 70 percent.
Previously, the majority of heat needed for the system came from burning oil, but that has now been completely eliminated. The system will continue to burn wood chips to supplement the sand battery. Wood chips are at least carbon neutral, although not an ideal solution since it takes years for trees to grow but only minutes for the chips to burn.
At the commissioning ceremony for the new battery, Mikko Paajanen, CEO of Loviisan Lämpö, said, “A couple of years ago, we started considering how to take district heating in Pornainen to the next level. It would have been easy to simply replace the old wood chip power plant with a new one of the same kind, but that didn’t align with our goals. We evaluated every possible alternative, and the Sand Battery proved to be the best option.”
The battery is a 42 foot tall, 50 foot wide steel cylinder filled with 2,000 tons of crushed stone. According to Fast Company, when extra renewable electricity is available, the system uses it to heat up the crushed stone, where it is stored until needed. Then the heat from the battery travels to other buildings through a system of pipes filled with hot water. Each building has its own equipment to distribute the heat to radiators, floor heaters, or other heating devices.
“We have already learnt that our system has even more potential than we initially calculated. It’s been a positive surprise,” said Ylönen after the prototype was placed in service. “Whenever there’s a high surge of available green electricity, we want to be able to get it into the storage really quickly.” The need to use energy more wisely was driven home for Finns after Russia stopped providing electricity, methane, and oil to Finland when it voted to join NATO. Finland and Russia share a common border.
Sand Battery Is Simple & Efficient
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