“That, the companies claim, equates to a week’s worth of Pornainen’s heat demands in winter, or a month’s worth in summer.”
Polar Night Energy is building a 100 MWh steel silo of crushed soapstone for one Finnish town’s district heating. It charges on cheap surplus grid power and cuts the network’s emissions by 160 tonnes a year, almost 70%. Turning it back into electricity loses energy, so the company just sells the heat. It only works where pipes already carry hot water to every house, and that is the whole trick.