PORNAINEN, Finland — Engineers will soon begin testing new “sand batteries” that can convert energy stored as heat into electricity and feed it into the power grid. But challenges lie ahead, they say, with investment costs potentially driving customers away.
Polar Night Energy’s existing sand battery model stores renewable electricity by using electricity to heat sand and sand-like materials to temperatures of up to 752 degrees Fahrenheit (400 degrees Celsius). That heat is then extracted to provide hot water, steam, or hot air.
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The new sand battery is “fundamentally completely different” from existing power-to-heat versions, Tommi Eronen, co-founder and CEO of Polar Night Energy, told Live Science at the existing sand battery site here in Polnainen. Although he could not provide further details, he said the shape was one of the key differences between the two batteries. Power-to-heat sand batteries have a horizontal configuration rather than vertical silos like power-to-heat versions.
The efficiency of new sand batteries will depend on their size and how they are integrated into existing systems. However, its expected efficiency is around 30% to 35%, comparable to the efficiency of combustion-based power plants, Polar Night Energy representatives said in a statement. For reference, the average efficiency of fossil fuel-based combustion power plants in the United States was 39% in 2023.
By converting this heat back into electricity, the new batteries will “help balance the power grid, reduce emissions, reduce dependence on fossil fuels, and pave the way for large-scale, affordable energy storage,” the representatives added in a separate statement.
But the new battery outputs both heat and electricity, increasing the system’s efficiency to about 90%, Eronen said. He added that the sand battery could be used in any industry that requires both heat and electricity, such as power companies.
The new sand cannon is currently being tested in the Finnish city of Valkeakoski, about 150 kilometers north of Helsinki. Construction will begin in October 2025 and testing will begin within weeks, with the pilot phase lasting approximately two and a half years in total. However, Polar Night Energy has already created designs for commercial products.
Polar Night Energy Chief Operating Officer Liisa Nascali told Polunainen’s Live Science that during the pilot project, engineers will be experimenting with different technological solutions that will enable future power generation. This includes the development of new materials. For example, it will “develop and test new materials and designs that can withstand higher operating temperatures,” representatives said in a statement.
The main barrier to this new sand battery is cost. “The only challenge in selling this to customers is that the investment price is very high,” Nascali added. “Few people are brave enough to invest in our product because we have wood chip boilers. [currently]And wood chips are pretty cheap.
He said sand batteries that convert electricity into heat and provide power are possible, but the problem now is how to find an economically viable and technically efficient solution. If it were easy, she pointed out, someone would have done it by now. “That’s possible, but at what price?”
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