The writer is a professor at MIT and Politecnico di Milano, and founder of Carlo Ratti Associati
This summer, as temperatures across Europe hit record highs, a familiar refrain reached deafening levels: that the continent must abandon its resistance to air conditioning and follow America’s example.
It is hard to ignore the rationale. Heat not only saps productivity, it also disrupts work and home life and can be deadly to vulnerable people. But Europe should think before it adopts wholesale the “dripping box” system that already exists. There are far better ways it can cool itself down.
These dripping boxes on buildings around the world trace their existence to 1902, when a young engineer, Willis Carrier, built his first “apparatus for treating air” for a Brooklyn printing plant. Since then, they have been replicated on buildings and rooftops millions of times. However, the basic principle has remained remarkably similar: a refrigerator turned inside out, spitting hot air outdoors while bringing a welcome chill indoors.
But that principle has a problem. It does not reduce heat so much as move it, pushing it out of buildings and into the street. The hotter streets mean more cooling is required, producing more heat. As the temperature rises, the system has to work ever harder.
The way out of this loop is to exchange heat with the ground or the water instead. Many great cities were, not by accident, built around lakes, rivers or the sea, with the water acting as a thermal reservoir, holding temperatures relatively stable throughout the year.
Such systems can work at the individual building level. But the use of water to store excess heat can also allow them to scale up to whole city blocks. One of the largest district cooling networks in the world is Fraîcheur de Paris, which sounds like a fine cologne: a promise of coolness delivered by water drawn from the Seine. Another expanding system is in Geneva, which uses the city’s lake (despite a problem with invasive mussels that has been mitigated with mechanical pipe scrapers). Rather than millions of private systems competing for electricity and pumping out waste heat, a city can manage thermal energy as it does water or power: through a shared network.
Water can do more than carry heat away. In some advanced systems, it acts as a kind of “thermal battery”. When electricity is cheap and abundant, water is chilled and stored; when temperatures peak, that stored coolness is released. This takes pressure off electricity grids strained by air conditioning.
None of this is a total solution. Every cooling system has its limits, and buildings can be made to do much of the work with better glazing and ventilation, well-placed shading and reflective roofs. Trees matter too. Research, including our own with the Dubai Future Foundation, has shown they can meaningfully lower street-level temperatures.
The best answer, then, is a mixed system, co-ordinated in real time, with sensors to track temperature, occupancy and demand, and algorithms deciding when to produce, store and distribute cooling in step with the electricity grid.
Built this way, cooling the air becomes an industry to be won. Cutting-edge engineering is a sector where Europe still has genuine strength, after all, with names like Danfoss, Bosch, Schneider Electric and Saint-Gobain.
Carrier came up with a way to cool individual buildings, and the world went with it. Europe now has the chance to do something different and more ambitious. Fraîcheur de Paris could become Fraîcheurs du Monde: not a fallback for a continent playing catch-up, but a system designed for a warming century and ever hotter demand for cooling.
The writer is a professor at MIT and Politecnico di Milano, and founder of Carlo Ratti Associati
This summer, as temperatures across Europe hit record highs, a familiar refrain reached deafening levels: that the continent must abandon its resistance to air conditioning and follow America’s example.
It is hard to ignore the rationale. Heat not only saps productivity, it also disrupts work and home life and can be deadly to vulnerable people. But Europe should think before it adopts wholesale the “dripping box” system that already exists. There are far better ways it can cool itself down.
These dripping boxes on buildings around the world trace their existence to 1902, when a young engineer, Willis Carrier, built his first “apparatus for treating air” for a Brooklyn printing plant. Since then, they have been replicated on buildings and rooftops millions of times. However, the basic principle has remained remarkably similar: a refrigerator turned inside out, spitting hot air outdoors while bringing a welcome chill indoors.
But that principle has a problem. It does not reduce heat so much as move it, pushing it out of buildings and into the street. The hotter streets mean more cooling is required, producing more heat. As the temperature rises, the system has to work ever harder.
The way out of this loop is to exchange heat with the ground or the water instead. Many great cities were, not by accident, built around lakes, rivers or the sea, with the water acting as a thermal reservoir, holding temperatures relatively stable throughout the year.
Such systems can work at the individual building level. But the use of water to store excess heat can also allow them to scale up to whole city blocks. One of the largest district cooling networks in the world is Fraîcheur de Paris, which sounds like a fine cologne: a promise of coolness delivered by water drawn from the Seine. Another expanding system is in Geneva, which uses the city’s lake (despite a problem with invasive mussels that has been mitigated with mechanical pipe scrapers). Rather than millions of private systems competing for electricity and pumping out waste heat, a city can manage thermal energy as it does water or power: through a shared network.
Water can do more than carry heat away. In some advanced systems, it acts as a kind of “thermal battery”. When electricity is cheap and abundant, water is chilled and stored; when temperatures peak, that stored coolness is released. This takes pressure off electricity grids strained by air conditioning.
None of this is a total solution. Every cooling system has its limits, and buildings can be made to do much of the work with better glazing and ventilation, well-placed shading and reflective roofs. Trees matter too. Research, including our own with the Dubai Future Foundation, has shown they can meaningfully lower street-level temperatures.
The best answer, then, is a mixed system, co-ordinated in real time, with sensors to track temperature, occupancy and demand, and algorithms deciding when to produce, store and distribute cooling in step with the electricity grid.
Built this way, cooling the air becomes an industry to be won. Cutting-edge engineering is a sector where Europe still has genuine strength, after all, with names like Danfoss, Bosch, Schneider Electric and Saint-Gobain.
Carrier came up with a way to cool individual buildings, and the world went with it. Europe now has the chance to do something different and more ambitious. Fraîcheur de Paris could become Fraîcheurs du Monde: not a fallback for a continent playing catch-up, but a system designed for a warming century and ever hotter demand for cooling.
So let me ask this: The buildings where this system is going to be installed, how do their winter heating systems work?