Paris captures the warmth of its sewers

Sensemaking / Paris captures the warmth of its sewers

A French school draws on the capital’s famous sewage network for heating. Next up: Sarkozy’s palace.

30 Aug 2011

A French school draws on the capital’s famous sewage network for heating. Next up: Sarkozy’s palace.

The famous sewers of Paris, masterminded in the 1850s and described by Victor Hugo as a whole other city with its own streets and squares, have been awarded a new function: heating buildings.

A school in Paris has been fitted with a heat pump and 60m of heat exchangers to draw heat from the underground streams. Commercial and domestic wastewater, from washing machines and dishwashers, raises the sewage temperature up to 20°C – heat that largely goes to waste.

Exchanger plates in the sewers now draw this heat into a transfer fluid running through a steel loop and to a heat pump in the cellar of Wattignies School. The pump concentrates the heat, raising the temperature to 60°C, and distributes it around the building.

The €400,000 installation – funded by Paris’ public heating organisation CPCU and water company Lyonnaise des Eaux – is part of the city’s goal of generating 30% of its power from renewable sources by 2020, and will provide 70% of the school’s heating needs. The technology can only be used within 200m of the sewer source, but the council estimates 10% of Paris could be heated this way.

Mayor Bertrand Delanoë called the project “a hallmark of the dynamism of Paris”. The Élysee Palace, residence of President Nicholas Sarkozy, is next up for the treatment. The development will be receive grant funding from the French Environment and Energy Management Agency, and will reduce the Palace’s carbon emissions by around 206 tonnes a year.

Similar systems have been trialled successfully in Norway and Japan, and the 2010 Vancouver Winter Olympics village also drew on waste sewage heat.

Terry Seward, Secretary of the Heat Pump Association in the UK, where dozens of schools generate electricity from ground-source heat pumps, said the high initial cost of such systems can be a barrier but that they are a good way of teaching children about renewables. “It’s an innovative use of the technology in Paris and should be pursued.” – Isabella Kaminski

Image credit: Karambole pour Lyonnaise des Eaux

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