A city in Southern Spain holds an ancient secret to fighting extreme heat

"We have deployed several types of cooling systems here, each one used depending on climatic conditions. The system, created millennia ago but updated for the 21st century, works by cooling water underground in the naturally low temperatures at night. To cool water more quickly, some is also sent to the roof via solar-powered pumps and sprayed out of nozzles in a thin layer through a method known as a falling film, before draining back down underground."

"By day, as outdoor temperatures peak, the cool water is sent above ground into the ceiling to counteract the heat. Water is also funneled into subterranean pipes that cool air (up to 36,000 square meters an hour), which is then released via ducts in the public spaces."

"In 2020, authorities began to install these cooling systems in two public spaces in the Isla de La Cartuja neighborhood of what is one of Europe's hottest cities. Every day about 30,000 people come to work and study in this northwestern district, which is mostly non-residential and home to university campuses, museums, and businesses."

Beneath Seville's former World Expo site, researchers have implemented an innovative cooling system that revives ancient qanat technology—underground aqueducts—enhanced with modern engineering. The EU-funded CartujaQanat project operates in two public spaces: the Agora (750 square meters) and a renovated amphitheater. The system cools water underground during cool nighttime temperatures, then uses solar-powered pumps to spray water across roofs via a falling film method for faster cooling. During peak daytime heat, the cooled water circulates through ceiling pipes and underground ducts to cool air up to 36,000 square meters hourly. This hybrid approach serves approximately 30,000 daily visitors in Isla de La Cartuja, a non-residential district containing universities, museums, and businesses.

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