Carlo Ratti Associati’s ‘Hot Heart’ is an archipelago of heat-storing floating islands

Bearing a whimsical name and a uniquely peculiar purpose, the Hot Heart designed by Italian architecture firm Carlo RattiAssociati is probably the largest infrastructural intervention of its kind. Located just off the coast of Helsinki, Finland, the islands have been designed to store thermal energy for the chilly winter months in the capital city, while also housing artificially sustained tropical forests and varied ecosystems from around the world to serve as a vast, new public recreation space. The project, formed as a collaboration between interdisciplinary teams including CRA, Ramboll, Transsolar, DanfossLeanheat, Schneider Electric, OP Financial Group, schlaichbergermann partners and Squint/Opera, was adjudged the winner of the Helsinki Energy Challenge.

Organised by the municipality of Helsinki with the aim of accelerating the city’s transition to carbon neutrality in heating by 2030, Hot Heart is hailed as a modular, adaptable intervention that can be replicated by other cities with similar climatic conditions. Helsinki faces particularly chilly months with temperatures dropping to as low as -20 degrees, incurring heating demands estimated at 6000 GWh. The islands are envisioned to cover the entire demand without the added load of any carbon emissions, at a cost touted to be approximately 10% lower than current conventional methods.

The entire system functions in sophistication and in tandem as a giant thermal battery, wherein heat from excess renewable energy, generated at low or negatively offset cost, is stored in a set of 10 underwater cylindrical basins, each measuring 225m in diameter. The stored heat is withdrawn from the tanks to be fed into the city’s heat distribution networks during the winter. Making this project truly unique and multidimensional is its designed provision to double up as an extension of Helsinki’s accessible public space, opening up an unprecedented avenue for the city towards the sea. In addition to its thermal storage properties, four of the 10 hot water basins are enclosed in domes that house “floating forests”, intended to provide the city of Helsinki and its residents a climate agnostic experience, as opposed to its native chill.

Additionally, the forests ensconced within the domes are sustained in a cyclical manner by the natural heat provided by the floating basins underneath. The use of powerful LED technology is envisioned to help maintain optimal temperatures for the Amazon like forestry to thrive, and to provide thermally comfortable public spaces to patrons and travellers alike.

The design and operation of the heat storing basins uncovers another layer of sophisticated technology that is sure to bewilder as well as perplex in anticipation. Aided by artificial intelligence, the central concept of the project aims to use seawater heat pumps to convert wind, solar and other forms of energy into heat, which is stored in Hot Heart’s reservoirs. The AI helps in synchronously operating the production and consumption of thermal energy, stated to stabilise the national energy grid in relation to fluctuating supply.

“Production of renewable energy is getting cheaper, but storage is still extremely expensive. Our idea is to use the giant ‘thermal batteries’ to store energy when prices are at low or even negative levels, and extract it when required by the district heating system when demand is high. This model would also be applicable to many coastal cities with similar climates,” states Carlo Ratti, founding partner of CRA on the economic feasibility of the heating system storage design. On the softer aspects of his mega-design, he states that Hot Heart “offers a unique experience, bringing the natural and artificial worlds together. It is inspired by the Finnish concept of JokamiehenOikeudet, which could be translated as ‘every person’s right’: the right to reflect and unwind while peacefully enjoying nature.”

Currently in its master planning stage, Hot Heart is projected to be fully implemented in Helsinki by 2028.

Project Details

Name: Hot Heart
Location: Helsinki, Finland
Projected Year of Completion: 2028
Design: CRA-Carlo RattiAssociati
General Engineering: Ramboll
Climate Engineering: Transsolar
Technology Partner for Sustainability and Energy Efficiency: Schneider Electric