World’s largest thermal energy storage to be built in Finland

Taking advantage of the disparity in heat consumption between Summer and Winter, a huge facility capable of holding over a million cubic meters of water at 140°C, is being built in the Finnish city of Vantaa.

To borrow from Wikipedia: Thermal energy storage is the storage of thermal energy for later reuse. Employing widely different technologies, it allows surplus thermal energy to be stored for hours, days, or months. Scale both of storage and use vary from small to large – from individual processes to district, town, or region.

The seasonal thermal energy storage facility will be built in Vantaa’s bedrock, 100m below ground. Three caverns will be excavated, creating a space twice the size of Madison Square Gardens. These will be filled with hot water. Pressure will be created within the space, allowing the water to reach temperatures of up to 140 degrees without it boiling or evaporating.

The stored heat will be used to supply the district heating network whenever needed.

The total thermal capacity of the facility when fully charged will be 90GWh – enough to heat a medium-sized Finnish city for a year or the equivalent of 1.3 million electric car batteries.

Jukka Toivonen, CEO of Vantaa Energy who are behind the project, said: ‘Two 60-MW electric boilers will be built in conjunction with Varanto. These boilers will be used to produce heat from renewable electricity when electricity is abundant and cheap. Through the intelligent control of Varanto, electricity generation, waste heat and district heating, Vantaa will receive a hybrid system enabling us to take full advantage of the different energy sources. Our heat-producing system will work like a hybrid car: alternating between electricity and other forms of production, depending on what is most advantageous and efficient at the time.’

Finland is an ideal location for such a facility, given the widespread heat networks that exist in the country. In Vantaa alone the networks stretches for more than 6ookm, with around 90% of the population connected to it.

Jukka Toivonen said: ‘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.’