While there are several examples around France and elsewhere, the news service Reuters provided a good article in The Guardian about a recent heating installation in a Parisian swimming pool using the heat from the sewer system.
Drain brain: Paris pool uses sewer heat to cut costs and emissions
A Paris swimming pool has inaugurated a heating system using warmth recovered from sewers in an attempt to cut costs and reduce carbon emissions.
The Aspirant Dunand pool in the 14th arrondissement is the latest in a series of French public buildings to use heat pumps to recycle residual warmth from showers, dishwashers and washing machines in its sewers.
The French waste and water group Suez, which has a 30-year contract to run the installation, already operates a dozen such heating systems around the country, including in pools in the Paris suburb of Levallois and in Annemasse, near the Swiss border.
They are also in use in schools, apartment blocks and administrative buildings, and Suez is installing three to four new systems a year.
“The potential is enormous. Wherever there are sewers, we can recover heat,” said Bertrand Camus, the head of Suez water in France.
France has about 250,000 miles of drains and sewage pipes, and their water temperature typically ranges between 13C in winter and 20C in summer.
By lining pipes with stainless steel, Suez is able to harness between four and eight degrees of that warmth and boost it to about 50C for use in space heaters or as hot water. The technology is similar to low-temperature geothermal energy, already widely used in some countries to heat individual homes.
Suez says the cost ranges from €200,000 (£176,000) for a pool to €1m for an apartment block, and that such projects pay for themselves over eight to nine years without subsidies and at normal energy prices.
Camus said the Aspirant Dunand installation covers nearly half of the pool’s energy consumption.
Paris aims to reduce its greenhouse gas emissions, boost the share of renewables in the administration’s energy use to 30% by 2020 and make better use of its sewage network.