Finnish researchers have installed the world’s first fully working “sand battery” which can store green power for months at a time.
Using low-grade sand, the device is charged up with heat made from cheap electricity from solar or wind.
The sand stores the heat at around 500C, which can then warm homes in winter when energy is more expensive.
Right now, most batteries are made with lithium and are expensive with a large, physical footprint, and can only cope with a limited amount of excess power.
But in the town of Kankaanpää, a team of young Finnish engineers have completed the first commercial installation of a battery made from sand that they believe can solve the storage problem in a low-cost, low impact way.
“Whenever there’s like this high surge of available green electricity, we want to be able to get it into the storage really quickly,” said Markku Ylönen, one of the two founders of Polar Night Energy who have developed the product.
The device has been installed in the Vatajankoski power plant which runs the district heating system for the area.
Low-cost electricity warms the sand up to 500C by resistive heating (the same process that makes electric fires work).
This generates hot air which is circulated in the sand by means of a heat exchanger.
Sand is a very effective medium for storing heat and loses little over time. The developers say that their device could keep sand at 500C for several months.
So when energy prices are higher, the battery discharges the hot air which warms water for the district heating system which is then pumped around homes, offices and even the local swimming pool.
The idea for the sand battery was first developed at a former pulp mill in the city of Tampere, with the council donating the work space and providing funding to get it off the ground.
One of the big challenges now is whether the technology can be scaled up to really make a difference – and will the developers be able to use it to get electricity out as well as heat?
The efficiency falls dramatically when the sand is used to just return power to the electricity grid.
But storing green energy as heat for the longer term is also a huge opportunity for industry, where most of the process heat that’s used in food and drink, textiles or pharmaceuticals comes from the burning of fossil fuels.