Helen, a Finnish energy company, has completed the filling of underground heat caverns in Mustikkamaa with water in order to heat homes in Helsinki. This filling process took over three months due to the large volume of the caverns, which would have taken over 50 years to fill from a regular tap. The water storage facility is currently at a temperature of about +30 degrees and the slow heating of the bedrock has begun. The aim is to connect the heat caverns to Helsinki’s district heating system in July. This innovative use of old oil caverns as an energy storage facility is a unique example of Finnish innovation. The heat contained in the water in the caverns is enough to heat 25,000 one-bedroom apartments all year round and the project will decrease carbon dioxide emissions by 21,000 tonnes per year. Helen is actively working towards a carbon-neutral future, with plans for other sustainable energy projects such as a geothermal heating plant, seawater heat pumps, and waste heat utilization.
https://www.helen.fi/en/news/2021/gigantic-heat-caverns-in-mustikkamaa-filled