Paris is cooling 3,000 buildings with river water

Paris is planning to triple a cooling network that uses river water instead of air conditioning, aiming to reach more than 3,000 buildings by 2042. Fracheur de Paris runs 120 kilometers of underground pipes carrying cold water drawn from the Seine. A heat exchanger moves warmth between two pipes that never touch, then sends the river water back slightly warmer than it left. Monitoring so far shows the temperature changes stay within environmental limits, with no measurable harm to the river's ecology. The Louvre, the Grand Palais and several hospitals are already connected. "Everything that requires energy releases heat, and that heat has to go somewhere," said Sophie Parison, a researcher in Paris focused on urban heat. The expansion prioritizes hospitals and day-care centers. Stockholm did the same with the Baltic and Toronto with Lake Ontario, adapting the logic rather than copying the pipes. London looked at the Thames. The Thames did not qualify.