To meet its goal of making Helsinki carbon-neutral by 2030, the municipality of Helsinki launched the Helsinki Energy Challenge in February 2020, where it invited proposals to suggest sustainable alternative solutions to decarbonize the heating system of Helsinki. 

Floating reservoirs to create carbon-free heating for Helsinki proposed by Carlo Ratti Associati - Sheet3
Aerial View of the floating reservoirs_ⒸCarlo Ratti Associati

Carlo Ratti Associati (CRA), an Italian design and innovation firm, was one of the four winners of the challenge, who in collaboration with Squint/Opera, Ramboll, Transsolar, Danfoss/Leanhear, Schneider Electric, OP, and Schlaich Bergermann Partner, proposed the design of a series of, island-like, floating reservoirs to collect and store thermal energy for use in the cold winters of Helsinki. 

Owing to the cold climate of Finland, the energy requirements of existing urban heating systems are massive and contribute to nearly 56% of the city’s carbon emissions. As opposed to the current district heating system that sources heat by burning fossil fuels and biomass, CRA’s design would source heat from seawater heat pumps that would convert carbon-free electrical energy into heat. 

Floating reservoirs to create carbon-free heating for Helsinki proposed by Carlo Ratti Associati - Sheet4
Structural system of the cylindrical basins_Ⓒ

Titled as Hot Heart, CRA’s design proposal essentially behaves as a thermal storage system, composed of ten floating cylindrical basins, each of a diameter of 225 meters, that can collectively store up to 10 million cubic liters of water. CRA proposed to use these systems with two types of storage modulespartially excavated into the sea bed and completely floating. 

Each of the cylindrical basins would be made of tubular walls100-inch diameter tubes similar to those found in oil and water pipelinestied together with prestressed radial cables mimicking the structure of a bicycle wheel. To secure the basins, the rings would be anchored to the sea bead and would be covered with a metal base at the bottom. 

“The latter is more conservative and could work well in Helsinki due to its shallow sea nearby. The former could use innovative wind offshore technologies, have lower impact, and be replicated in cities around the world.” [1]

Floating reservoirs to create carbon-free heating for Helsinki proposed by Carlo Ratti Associati - Sheet5
Overall energy harvesting and utilization system Ⓒ

The process of utilization of these thermal batteries starts with the usage of renewable energy sources which when become abundant and inexpensive transfer the excess to be stored in these thermal batteries which can then be supplied to the city, during winters, via its standard district heating system.  

CRA collaborated with trans-disciplinary organizations to come up with the most efficient system of energy generation and conservation where the seawater heat pumps are used to convert wind, solar and other forms of power into heat, to be ultimately stored in Hot Heart’s reservoirs. energy can be input in the form of electrical energy which is converted into thermal energy and stored for later use. 

Floating reservoirs to create carbon-free heating for Helsinki proposed by Carlo Ratti Associati - Sheet6
Helsinki’s Hot Energy Management System Ⓒ

It is backed by AI to run a ‘predictive energy management system’ that would keep a track of real-time weather conditions and regulate the heat supply as and when required by the city. It would also aid in fault detection and ensure optimum utilization of the storage facility. 

This system also acts as a load balancer to the national energy grid and can cater to the heating requirements of the entire city of Helsinkiestimated at 6000 GWh, by using technologies with zero carbon footprint made available to users at extremely economical prices. 

Floating reservoirs to create carbon-free heating for Helsinki proposed by Carlo Ratti Associati - Sheet7
The four domes that will house tropical rainforests_Ⓒ

Apart from serving the mechanical needs of energy systems, the reservoirs have been designed to host an additional function- that of behaving as public recreational spaces. Four out of the ten cylindrical basins would be encased in transparent inflatable domes made out of ETFE with inbuilt insulation features to allow natural light to enter the domes freely. 

The interiors of these domes would be designed to house ‘Floating forests’ in the form of the tropical rainforest-like arrangements that replicate important rainforests of the world, the heating requirements of which would again be provided by the basins themselves. 

These spaces act as socializing spaces, all year round and winters, in particular, gracing the coast, that provide comfortable natural environments to the city dwellers who would otherwise be devoid of warm open spaces to interact in the harsh cold of Helsinki. 

Floating reservoirs to create carbon-free heating for Helsinki proposed by Carlo Ratti Associati - Sheet
Renders of the interiors of the floating forests ⒸCarlo Ratti Associati
Floating reservoirs to create carbon-free heating for Helsinki proposed by Carlo Ratti Associati - Sheet1
Renders of the interiors of the floating forests Carlo Ratti Associati

A Hot Hearth in a Cold City as CRA calls it is one of the many projects of its kind that the firm has developed on the lines of sustainable design innovations. Previously, the firm worked on various projects to improve urban environments through climate remediation. 

In 2017 CRA in collaboration with the Museum of the Future, in Dubai, designed an installation titled Sun and Shade that involved the usage of an array of mirrors that would respond to the incident sun and lighting conditions and ultimately reflect excess and unwanted heat and light to be collected at a far away sensor to generate energy. 

Similarly, in 2018 the firm designed an interactive pavilion called Living Nature, at the Milan Design Week, wherewith the help of advanced energy management systems for climate control they were able to house and let four different gardens of different seasons co-exist. Hence it is no surprise that CRA has come up with yet another AI-driven energy management system that contributes to a positive change in built environments and their energy systems. 

With this project taking the lead in creating sustainable urban environments, the organizers hope to use Helsinki as a testbed for projects alike and propel other cities sound the world to be inspired and create similar interventions to create positive global environmental impacts. 

It is no more an option to avoid discussions on climate change and with the statistics showing that cities and heavy urban bases contributing to nearly 80% of the world’s harmful carbon emissions it only becomes imperative to discuss and implement projects of such nature. 

The Hot Heart is surely one such project to take lessons from in creating carbon-neutral and sustainable urban environments. 

References :


Carlo Ratti designs digital shading for climate control

Living Nature | Carlo Ratti Associati.

Results of the Helsinki Energy Challenge  

The Hot Heart

Carlo Ratti Associati among winners of global Helsinki Energy Challenge

Hot Heart


Priyamvada Gannavarapu is an architecture student who believes in the ability of architecture to influence and inspire human behaviour in fostering positive, efficient and sustainable built environments. As an avid reader ,a trained Bharatanatyam dancer and Carnatic vocalist she likes to explore the various aspects of experiential design in creating meaningful habitable spaces for users alike.