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Climate change: 'Sand battery' could solve green energy's big problem

By District Energy posted 07-06-2022 08:27

  

BBC News

Summary

Finnish researchers have installed the world's first fully working "sand battery" which can store green power for months at a time.

The developers say this could solve the problem of year-round supply, a major issue for green energy. 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.

The key element in this device? Around 100 tonnes of builder's sand, piled high inside a dull grey silo. These rough and ready grains may well represent a simple, cost-effective way of storing power for when it's needed most.

"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.

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