As humans, we pride ourselves on our ability to innovate and adapt to a variety of environments. This has led us to develop technology that can support civilization, even in extreme environments. However, this technology largely relies on fossil fuels.

Now, there’s a global push to put human innovation to the test and see what alternative, environmentally friendly energy sources are out there to take the place of harmful fossil fuels.

The city of Helsinki, Finland recognized that to reach its goal of becoming carbon neutral by 2035, it would need an alternative, long-term solution to heat hundreds of thousands of homes and buildings.

The city decided to open up the drawing board to its citizens by hosting the Helsinki Energy Challenge. Anyone who could come up with a viable alternative would receive a one-million-euro reward sponsored by the city.

One of the ideas that emerged as a winner, Helsinki’s Hot Heart, proposes storing heat in seawater using ten floating reservoirs off the city’s coast.

The system would strategically harvest renewable electricity during times of the day when its most abundant and least expensive. The renewable energy will be used to run heat pumps that would heat the seawater and keep it in the reservoirs. The heat is sent on demand through Helsinki’s existing heating system, a network that sends heat to almost all the city’s buildings. Designer Carlo Ratti’s vision is for reservoirs to also double as greenhouses with hot pools that the residents can visit when the weather is cold and gray.

“In the specific context of Helsinki, it is ideal to use seawater to store heat because it is readily available in the sea outside the city, does not require any costly transportation, which would result in CO2 emissions, and does not create interference with the natural ecosystem,” Ratti states. “It’s also easy to store seawater in basins in the sea because the water inside has a similar pressure to the water outside, simplifying the structural requirements of the construction.”

The ingenious concept of floating reservoirs shows a lot of promise as it could theoretically be used in any city that borders the sea, lakes, or rivers. The designers working on the Hot Heart are confident that the technology could meet the city’s heating needs with zero carbon emissions well before Helsinki’s self-imposed deadline.

Image source: Carlo Ratti Associati