Largest sand storage facility for district heating is located in Finland
A silo full of soapstone stores heat, which is later released into the district heating network. This means that six Finnish municipalities no longer need oil.
This silo is full of soapstone gravel.
(Image: Polar Night Energy)
The Finnish start-up Polar Night Energy has built the world's largest “sand battery” from 2,000 tons of gravel. The basic idea is to store heat in sand or gravel so that it can be used later. Following a pilot project in the small town of Kankaanpää in western Finland, where the sand storage unit can generate 100 kilowatts and store eight megawatts, Polar Night Energy has now handed over a heat storage unit with ten times the capacity and twelve times the storage volume to district heating operator Loviisan Lämpö.
Loviisan Lämpö supplies district heating to the towns of Lappohja, Loviisa, Pornainen, Pukkila, Siltakylä and the center of the village of Pyhtää. The silo is around 13 meters high and has a diameter of around 15 meters. It is filled with 2,000 tons of soapstone gravel, which was produced as waste by a stove manufacturer. A hot air blower heats the soapstone tower to hundreds of degrees Celsius, and it can store a total of 100 megawatts of energy for months.
The electricity comes preferably from renewable energy –, especially when there is a surplus of electricity in the grid anyway and the electricity price is cheap, if not negative. The sand silo therefore also provides negative balancing power, which helps to stabilize the power grid.
Pilot project for electricity generator
The stored energy would be enough to supply the connected district heating network for almost a week in winter. That doesn't sound like much, but according to Loviisan Lämpö, it is enough to stop all oil combustion. The operator also expects to be able to reduce the combustion of biomass by around 60 percent because he now relies primarily on the electricity grid. If this is fully utilized, heat storage and biomass boilers are available.
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In principle, the stored heat could be used to produce hot air to run an electricity generator. Polar Night Energy announced such a pilot project to convert heat back into electricity in the spring. It is to be built in the town of Valkeakoski.
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