11 April 2024
by Sarah Morgan

World’s largest thermal energy storage to be built

The largest seasonal thermal energy storage in the world is reported to be built underground in Vantaa, Finland.

Varanto © Vantaa Energy

Varanto (meaning vault or reserve in english) will have fully charged seasonal thermal energy storage of 90GWh.

The seasonal thermal energy storage total volume is expected to be 1,100,000m3, including process facilities.

Varanto is to store heat in underground caverns so that it can be used to heat buildings via the district heating network whenever it is needed.

Construction of the storage facility’s entrance is expected to start in summer 2024. The seasonal thermal energy storage facility could be operational in 2028.

The project cost is estimated to be around €200mln, and it has already been awarded a €19mln investment grant from Finland’s Ministry of Economic Affairs and Employment.

The facility will be built in Vantaa’s bedrock, where a total of three caverns about 20m wide, 300m long and 40m high will be excavated. The bottom of the caverns will be 100m below ground level.

These underground caverns will be filled with hot water. Pressure will be created within the space, allowing the water to reach temperatures of up to 140oC without the water boiling or evaporating.

Two 60MW electric boilers will be built in conjunction with Varanto. These boilers will be used to produce heat from renewable electricity when electricity is abundant.

Through the control of Varanto, electricity generation, waste heat and district heating, Vantaa will reportedly receive a hybrid system enabling it to take full advantage of the different energy sources.

There are more than 600km of underground district heating networks in Vantaa. Around 90% of Vantaa residents live in a home heated by district heating.

In 2023, a total of 37.3TWh of district heat was produced in Finland. Of this, 53% was produced from renewable heat sources and 14% from waste heat.

Vantaa Energy CEO Jukka Toivonen says, 'The world is undergoing a huge energy transition. Wind and solar power have become vital technologies in the transition from fossil fuels to clean energy.

'The biggest challenge of the energy transition so far has been the inability to store these intermittent forms of energy for later use. Unfortunately, small-scale storage solutions, such as batteries or accumulators, are not sufficient; large, industrial-scale storage solutions are needed. Varanto is an excellent example of this, and we are happy to set an example for the rest of the world'.

For more like this...


Related topics