A huge sand battery is set to slash the carbon emissions of a Finnish town.
The industrial-scale storage unit in Pornainen, southern Finland, will be the world’s biggest sand battery when it comes online within a year.
Capable of storing 100 MWh of thermal energy from solar and wind sources, it will enable residents to eliminate oil from their district heating network, helping to cut emissions by nearly 70 percent.
“It’s exciting to build a large-scale thermal energy storage, which will also act as a primary production plant in Pornainen’s district heating network,” says Liisa Naskali, COO at Polar Night Energy, the company behind the innovation.
“This is a significant step in scaling up the sand battery technology.”
Sand batteries are getting bigger in Finland
The new 1 MW sand battery has a precursor. In May 2022, Polar Night Energy rigged a smaller design to a power station in Kankaanpää town.
Launched just as Russia cut off gas supplies in retaliation for Finland joining NATO, the project was a timely example of how renewable energy could be harnessed in a new way.
Euronews Green previously spoke to the young Finnish founders, Tommi Eronen and Markku Ylönen, who engineered the technology.
“We were talking about how – if we had the liberty to design a community for ourselves – how could we solve the energy problem in such a confined environment?” Markku said of the inspiration behind Polar Night Energy in 2018.
“Then quite quickly, especially here in the north, you run into the problem of energy storage if you’re trying to produce the energy as cleanly as possible.”
The friends started playing around with ideas, landing on sand as an affordable way to store the plentiful electricity generated when the sun is shining, or the wind blowing at a high rate.
Finding a way to store these variable renewables is the crux of unleashing their full potential. Lithium batteries work well for specific applications, explains Markku, but aside from their environmental issues and expense, they cannot take in a huge amount of energy.
Grains of sand, it turns out, are surprisingly roomy when it comes to energy storage.
The sand battery in Pornainen will be around 10 times larger than the one still in operation at Vatajankoski power plant in Kankaanpää. The start-up also previously connected a pilot plant to the district heating network of Tampere city.
So how do sand batteries work exactly?
It’s quite a simple structure to begin with, Polar Night Energy said of its prototype. A tall tower is filled with low-grade sand and charged up with the heat from excess solar and wind electricity.
This works by a process called resistive heating, whereby heat is generated through the friction created when an electrical current passes through any material that is not a superconductor. The hot air is then circulated in the container through a heat exchanger.
The sand can store heat at around 500C for several days to even months, providing a valuable store of cheaper energy during the winter. When needed, the battery discharges the hot air – warming water in the district heating network. Homes, offices and even the local swimming pool all benefit in Kankaanpää, for example.
“There’s really nothing fancy there,” Markku says of the storage. “The complex part happens on the computer; we need to know how the energy, or heat, moves inside the storage, so that we know all the time how much is available and at what rate we can discharge and charge.”