Finnish researchers have installed the first fully operational “sand battery”, which can store green energy for months.
The researchers point out that the new battery could solve one of the great problems of renewable energy: ensuring continuous supply throughout the year.
The device uses low-grade sand that is heated with cheap electricity produced by solar or wind power.
The sand stores heat at around 500°C, which can then be used to heat homes in winter when energy is more expensive.
Finland imports most of the gas it consumes from Russia, and the war in Ukraine has intensified interest in viable alternatives.
The country has the longest border with Russia of any European nation. Moscow recently suspended the supply of gas and electricity to the Nordic country due to its request to join NATO.
Politicians and citizens alike in Finland are concerned about possible shortages of heat and light, especially during the long, cold winter.
But in the west of the country, a small power plant is using a new system that could help ease that concern.
The key element of this technology? About 100 tons of the type of sand used in construction, stacked in a silo.
These coarse grains of sand could be a simple and cheap way to store energy for when it’s needed most.
While more solar panels or wind towers can quickly be added to power grids, these power sources also pose major challenges.
The biggest problem is intermittency, in other words, how to keep the lights on when the sun isn’t shining or there isn’t enough wind.
Connecting more renewable resources also requires adding other energy sources to balance the electrical grid, since too little or too much power can cause it to collapse.
The most obvious answer would be to use large-scale batteries that store and balance energy as the grid becomes greener.
But today most batteries are made with lithium, take up considerable space, are expensive, and can only deal with a limited amount of additional power.
Hence the interest in solutions such as those in Kankaanpää, a town where a team of young Finnish engineers completed the installation of the first commercial system with a sand battery.
“When there’s a big increase in green electricity, we’re looking to store it really fast,” said Markku Ylönen, one of the two founders of the Polar Night Energy company, which developed the sand battery.
The new design was installed at the Vatajankoski Generating Plant, which supplies electricity to the surrounding district.
Low-cost electricity is used to heat the sand to a temperature of up to 500°C by resistance (the same process used in electric heaters).
A current of hot air is recirculated into the sand, which loses heat very slowly and is a very effective means of storing it.
The engineers claim that its battery can keep the sand at around 500°C for months.
When energy prices rise, the battery can release high-temperature air to heat water in the district heating system, which in turn heats homes, offices and even the local swimming pool.
The sand battery idea was initially tested at a pulp mill in the city of Tampere. Local authorities donated the physical space and funds to make the project a reality.
“If we have power plants that only work a few hours in winter when it’s colder that would be extremely expensive,” said Elina Seppänen, an energy and climate specialist in Tampere.
“However, if we have solutions that offer flexibility in heat usage and storage, I think this will help a lot in terms of cost.”
One of the biggest challenges now will be scaling this technology and using it to get electricity as well as heat.
The efficiency of the system drops dramatically when it is used to supply electricity to the grid.
However, storing green energy in the form of heat can also be an opportunity for the industrial sector, where the heat used in the production of food, beverages, textiles or medicines comes from the burning of fossil fuels.
Other research groups, such as the US National Renewable Energy Laboratory, are also studying the use of sand batteries.
But Finland is the first country with a commercial and operational system that has been working well, according to the man who bet on this technology.
“It’s really simple, but we liked the idea of trying something new, of being the first in the world to do it,” said Pekka Passi, director of the Vatajankoski power plant.
“It seems a little crazy, but I think it will be a success.”