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 system can generate 100 kilowatts and store eight megawatt hours, Polar Night Energy has now handed over a heat storage system with ten times the capacity and twelve times the storage volume to the 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 megawatt hours 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 low, if not negative. The sand silo therefore also provides negative balancing power, which helps to stabilize the power grid.
