Recently, heat waves have once again affected many parts of the world, forcing people to cope in a variety of ways. While the citizens of the United States of America were forced to use backup power supplies for air conditioners during energy crises, Depth presented a completely different, ecological and now viral idea.
China uses the natural mechanism of perspiration to cool buildings, but on a much larger scale. In this way, the temperature of the city block drops, and passers-by and residents do not get wet.
How rain from roofs works
A rooftop rain system has been installed on several residential buildings in the city of Yuncheng, in northern China’s Shanxi Province. This system works by ejecting a fine mist of water through 200 high-density nozzles mounted on the roofs of the solitaires.
Working in intervals of about 10 minutes, this artificial rain manages to lower the temperature of the surrounding space by 5°C do 8°C. Of course, it is common knowledge that water cools everything it touches, but the key advantage of this Chinese technology lies in the fact that passers-by and residents under the buildings remain completely dry.
The secret is in a scientific principle called evaporative cooling (evaporative cooling). It is exactly the same mechanism by which the human body uses sweat to cool itself. Micro-particles of water mist absorb ambient heat from the air until they evaporate. As the process takes place at the molecular level, whatever remains in the air becomes significantly colder, directly lowering the local temperature.
As an interesting aesthetic side effect, water mist refracts light and creates rainbows over buildings. In somewhat gray city districts, this comes as a pastime and something that pleases, and is almost rarely seen.
Did Yuncheng design salvation for Europe?
Although the world is only just now massively learning about the technology from Juncheng, this system has actually been successfully functioning since August 2024. If the spokeswoman for the Chinese Ministry of Foreign Affairs, Mao Ning, had not officially shared a video about this project on social networks at the beginning of July, most of the planet would probably not even know that such a solution exists.
Many world media quickly used this opportunity to draw a parallel with Europe, which year after year struggles with more and more extreme summers. Great Britain is especially mentioned in this context, because summers there regularly break historical records, while air conditioners in households are still a real rarity. This is so to the extent that some islanders have a traditional aversion to the very concept of air conditioning
Assuming the scientific theory holds water in all conditions, China’s rooftop sprinkler system could offer an elegant solution for European cities. However, it all depends on geographical factors and climate.
The problem of high humidity
The main reason why this innovative cooling system works flawlessly in China is because it is installed on tall residential buildings in a specific region with relatively drier air during peak heat.
If we tried to transfer this concept to countries like Great Britain, we would encounter a serious obstacle. Great Britain has an extremely humid climate, a high air humidity limits the effectiveness of evaporative cooling. When the air is already saturated with moisture, the water particles from the sprinklers cannot evaporate quickly and absorb the heat, which means that the cooling effect would be minimal. In addition, British and Northern European houses have historically been built to retain and trap heat inside by sending it up the inside of the walls. For this reason, an external water/steam mist system would hardly solve the problem of internal stuffiness.
However, rain from roofs could work perfectly in large, continental European metropolises with dry summer climates. Let’s say, in Belgrade and throughout Serbia.
For all other regions, affordable and energy-efficient solar-powered air conditioners remain the most reliable way to beat the summer heat and win the trust of skeptical citizens.