Helen has decided to build Finland's largest heat storage facility in the old oil caverns in Mustikkamaa for the storage of district heat. The heat storage facility will allow reduction in the use of fossil fuels.
The investment decision on the Mustikkamaa cavern heat storage facility was approved by Helen’s Board of Directors in March. The value of the investment is about EUR 15 million, of which EUR 2.1 million will be met from the investment aid for new technology granted by the Ministry of Economic Affairs and Employment.
The planning of the cavern heat storage facility has already been launched, procurement will start in the spring and construction work will begin in early 2019. The heat storage facility will be completed for production use in 2021.
The three caverns located underground in Mustikkamaa have previously been used for storing heavy fuel oil. The oil stores were emptied and decommissioned already in 1999. Two of the connected caverns will now be converted into a heat storage facility.
District heat will be stored in the caverns for use at another, more suitable time. On discharge, the heat can be utilised as such as district heat. The heat storage facility will provide flexibility to the energy system as it will balance variable heat consumption.
- Thanks to the Mustikkamaa cavern heat storage facility, it will no longer be necessary to use and produce all heat at the same time. With the facility, it will be possible, for example, to avoid starting up separate oil- or gas-fired heating plants in the winter season, says unit head Juhani Aaltonen of Helen.
- The use of fossil fuels in separate heat production will be reduced with the heat storage facility, and the use of renewable fuels and combined heat and power generation will be increased at the same time, Aaltonen continues.
The volume of the heat storage facility is 260,000 cubic metres. Its charging and discharging capacity is 120 megawatts, which enables discharge or charge for about four days when the accumulator is full or empty.
Underground infrastructure is utilised
The Mustikkamaa cavern heat storage facility will hold over 40 times the volume of water in the pools in the Helsinki Swimming Stadium. The facility will be filled with tap water and connected to the district heating network via heat exchangers.
The existing tunnel running under the sea and Sompasaari island between the Hanasaari power plant area and Mustikkamaa will be utilised when the heat storage facility will be connected to the district heating network. As the underground caverns, process facilities and tunnels are already in place, the technical implementation has been designed without extra rock excavation.
The heat storage facility will be located fully underground. No structures will be built above the ground level, and the storage of heat will not have an impact on other activities in Mustikkamaa.
Important role in climate change mitigation
Helen strives for climate-neutral energy production. Several different kinds of methods are needed for climate change mitigation, and energy storage plays a key role in this.
The Mustikkamaa heat storage solution supports the implementation of the national energy and climate strategy. It will improve the energy efficiency of the energy system and reduce the use of fossil fuels. It will support the reduction of coal use and replacement of coal with other production methods.
The heat storage investment will support the functioning of the electricity market and increasing of renewable energy in the entire electricity system. It will also increase combined heat and power generation. The Mustikkamaa heat storage facility can be used for increasing profitable operating time in combined heat and power generation and improving its possibilities of operating on the market also in the future to safeguard the security of energy production and supply.
• The planning of the Mustikkamaa cavern heat storage facility has already started, and construction work will begin in early 2019. The heat storage facility will be completed for production use in summer 2021.
• Hot water is used for energy storage.
• The effective water volume in the cavern storage facility is 260,000 m3.
• It accommodates over 40 times as much water as the pools at the Helsinki Swimming Stadium.
• The amount of energy stored is 11.6 GWh.
• The charging/discharging capacity of the storage facility is 120 MW (sufficient for about four days).
• The use of the rock caverns as a heat storage facility will have no impact on other activities in Mustikkamaa.
• Helen also has heat storage facilities at the Vuosaari and Salmisaari power plants.
• Helen is also planning a heat storage facility in Kruunuvuorenranta. This seasonal energy storage facility would operate according to a different principle than the Mustikkamaa heat storage facility.