To cool its monuments, Paris relies on the Seine

With ever more frequent heat waves, Paris wants to expand its little-known "urban cold" network to keep its monuments at the right temperature using water from the Seine.

The city of Paris, which aims to become "the world's largest cooling network" by 2040, has signed a 20-year contract with the energy group Engie, which holds 85% of the shares of the company Fraîcheur de Paris, and the RATP, which owns the remaining shares.

“All the districts will be served in 2042”, announces Dan Lert, deputy mayor of Paris in charge of water.

Developing the cooling network makes it possible to avoid the use of "intense use" of individual air conditioning, which consumes electricity and emits greenhouse gases.

Christophe Ladaurade, commercial director at Engie, proposes with the town hall to stick to "a difference of 5 to 8 degrees between the outside and the inside", as allowed by the cooling network.

In the future, this cooling network will circulate in all Parisian hospitals, certain schools and in metro stations.

On the right bank of the Invalides bridge, a discreet spiral staircase leads to "Canada" - like the eponymous square where it is located - a water cooling station at a depth of forty meters, where a maze is located. of green, blue and gray pumps and pipes.

On one of the four levels of this station, which came into service in 2008, the water from the Seine is filtered, then descends into other tubes where a wall separates it from the closed cooling circuit.

Virtuous cycle

On the floor below, a pump pressurizes a cooling unit to cool the water and injects it into the underground circuit. The system operates virtually autonomously, controlled by two remote technicians from a central location near the Gare de Lyon.

Unlike urban heating in Paris, water cooling is mainly intended for tertiary activity sites, and not for housing or individuals.

"Our clients are office buildings, shopping centers, museums, institutions or even hotels", summarizes Benoit Reydellet, director of the Fraîcheur de Paris project.

The Louvre Museum, the National Assembly and the Radio France studios are thus kept cool, in part, thanks to the water from the Seine.

The system works all year round, since department stores or museums need to keep rooms cool and monitor the ambient humidity.

In winter, the Canada plant can use the "free cooling" system, which allows it to produce cold without consuming electricity by putting "direct water from the Seine in contact with water from the network", explains Mr. Reydellet.

The concessionaire has undertaken to develop this virtuous production from 2% to 11%, which represents an energy gain of one year over the next twenty years, the duration of the new concession contract, he underlines.

The megawatt-hour of cold is invoiced to customers at 137 euros. By Mr. Reydellet's own admission, "it's quite expensive, but much more virtuous than the cold produced by autonomous installations" such as air conditioners.

And the cold piping allows customers to remove grilles and other air conditioner vents from their roofs, in order to have the entire roof.

As for the water used, heated by the plant which extracted the cold, it ends up finding the river through four discreet evacuation routes. The few degrees difference with the ambient temperature have no "impact on the fauna and flora" of the Seine, reassures Benoit Reydellet.