The Helsinki energy company Helen is building Finland’s largest heat storage facility in former undergroundoil storage caves in the Mustikkamaa island. The reconverted caves will store hot water. The amount of hot water that can be stored in the caves corresponds to 40 times the amount of water in the pools of the Helsinki Olympic Stadium.

The heat storage facility is one of Helen’s many solutions on the company’s path towards carbon-neutral energy production.

Construction work in the underground spaces for the facility’s equipment and in a tunnel is now fully under way. In addition, district heat pipes are being installed from the Hanasaari power plant area to Sompasaari and to the underground district heat storage facility. The heat storage facility will be connected to the district heat network with the help of an existing tunnel that runs from the Hanasaari area under the sea and Sompasaari to the Mustikkamaa island. 

The Mustikkamaa heat storage facility will make the energy system increasingly flexible, as the charging and discharging of energy will help to ease peak demand for heat. As the energy of the storage facility is discharged, it can be utilized as such as district heat. 

The Mustikkamaa heat storage facility will be completed and ready for production in 2021.

Readmore in a blog from Helen (in Finnish)