All at sea: How Carlo Ratti’s giant sea tanks will heat Helsinki

Carlo Ratti Associati (CRA) has designed the "Hot Heart", a way of using seawater-powered heat pumps to store renewably-generated energy to heat buildings in Helsinki.

Winner of the Helsinki Energy Challenge, the system would function as a thermal battery. Ten cylindrical tanks in the Gulf of Finland, each 225m in diameter, will be able to hold a total of 10 million cubic metres of hot seawater.

Low-cost renewable energy such as from wind and solar would be converted into heat and stored in the tanks before entering Helsinki’s district heating system in winter.

Operated by artificial intelligence, the system synchronizes the production and consumption of thermal energy, which would help to stabilise the national energy grid.

The whole system is expected to cover the entire heating needs of Helsinki, estimated at 6,000 GWh, by the end of the decade, all without any carbon emissions and at an estimated cost 10% lower than today.

The archipelago of cylindrical "islands" will also be home to tropical forests and ecosystems from around the world.

CRA worked with Danish firm Ramboll on the project, engineer Transsolar, France’s Schneider Electric, Finland’s Danfoss, the UK’s Squint/Opera and consultant Schlaich Bergermann Partner on the project.

Jouni Laukkanen, Ramboll Finland’s director, said: "Wind power generation has evolved in recent years and is, in fact, the cheapest way to generate electricity. Further, electricity generated by wind power using heat pumps is also the cheapest way to produce district heat.

"However, it is not always windy. Thanks to the proposed huge heat storage, the use of electricity in district heating production can be timed to windy times and the annual variation in heat demand can be significantly balanced."

Hot Heart will now enter a "co-creation phase" in which the project’s development continues.

Image courtesy of CRA/Ramboll

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