Sand Battery Innovation: A Future Renewable Energy Solution Challenging Fossil Fuels
A Finnish energy innovation company, Polar Night Energy, is preparing to begin testing its latest “sand battery” technology. Unlike previous models, this battery is designed to convert the stored energy in the form of heat back into electrical power that can be fed directly into the electricity grid.
This technology represents a step forward from existing sand battery models, which previously only functioned to store renewable electricity by heating sand to temperatures of up to 400 degrees Celsius, then extracting it as hot water or steam.
CEO of Polar Night Energy, Tommi Eronen, revealed that this new model is technically “completely different” from the previous version. One of the most striking differences lies in its form; the battery uses a horizontal configuration, unlike the old model which was a vertical silo.
In terms of performance, this sand battery is projected to have an efficiency of around 30% to 35%, a figure comparable to fossil fuel-fired power plants in the United States, which averaged 39% in 2023. However, its main advantage lies in its dual output capability.
“The new battery will output both heat and electricity to increase system efficiency to around 90%,” said Eronen.
He added that this technology is ideal for industries that require heat and electricity simultaneously, such as utility companies.
The pilot project is located in Valkeakoski, about 150 kilometres north of Helsinki. Construction began in October 2025, and the testing phase is scheduled to last for two and a half years. During this period, engineers will test new materials capable of withstanding much higher operational temperatures to improve energy conversion efficiency.
The company states that converting heat back to power will greatly assist in balancing the electricity grid, reducing emissions, and decreasing dependence on fossil fuels.
Although technologically promising, the biggest challenge for this sand battery lies on the economic side. Chief Operating Officer of Polar Night Energy, Liisa Naskali, acknowledged that convincing customers to switch to this technology is not easy due to the high investment costs.
“One challenge in selling this to customers is its very high investment price,” said Naskali. “Almost no one dares to invest in our product because there are currently wood chip boilers, and wood chips are quite cheap.”
Naskali emphasised that while the sand battery power-to-heat-to-power can technically be realised, the current main focus is finding an economically viable solution. “It can be done, but at what price?” she concluded. (Live Science/Z-2)