As heatwaves intensify across Europe, most cities are reaching for a familiar fix of more air conditioning. But in 1990s Paris, planning began for a different kind of solution: one of the world’s largest district cooling networks.
The system has 120kms (75-miles) of underground pipes distributing chilled water to museums, offices, hospitals, schools and other public buildings including the Louvre, the Grand Palais, and some luxury hotels and office districts. Instead of thousands of individual air-conditioning units, cooling is produced centrally and shared across the city like a utility.
The system circulates cold water through a network of pipes: cold river water from the Seine is pumped through one pipe, which runs right next to a secondary pipe carrying warm water from the city’s buildings. A thin metal wall separates them and a heat exchanger allows the heat from the warm city water to enter the cold Seine water without the fluids ever touching. It is similar to holding a cup of hot tea in a bowl of cold water – the liquids don’t touch, but the tea cools down
I don’t think you grasp the sheer volume of water flowing through the Seine. Even after the planned expansion that triples the size of the system, under drought conditions it’ll only raise the temperature of the river by about 1.5°C, and most of the time it’ll be much less than that. Sure, the river isn’t big enough for the system to cover every building in Paris, but this expansion is sustainable.
Some kind of ground-based heat exchange system would probably be ideal. That way in the summer you can dump heat deep into the ground, and in the winter you can run the system in reverse to reclaim what remains of it for heating.
Not just the volume or the mass, either. The specific heat of water is so high that a kg of water can absorb 4.184 kJ for each degree Celsius. Air is about 1 kJ kg/°C, but also is about 1/900 the density at normal sea level temperature and pressure. So assuming some humidity, we’re talking 3500 liters of air being cooled by 1 liter of water, for each degree of temperature change of each.
I don’t think you grasp the sheer scale of humanity’s ongoing and relentless efforts to exceed even the most optimistic projections of any possibly sustainable boundaries, without any regard for anything beyond their completely myopic perception of their immediate needs in the present moment, but I do appreciate the context you’re providing.
I think I do.
France is in the EU and in the EU we have this thing called rule of law. The law in this case places limits on how much effect industry can have on the temperature of natural bodies of water. I believe in this case the limit is 1.5°C, so the system will basically by definition not exceed that.
I have no personal experience with that. It must be really nice.