Artificial turf equipped with self-cooling technology offers solution for cities facing extreme weather

By absorbing rainwater and allowing it to evaporate on hot days, artificial turf stays much cooler than regular artificial grass. Self-cooling turf protects athletes from burns and heat stroke and helps cities manage stormwater.

Such surfaces are already in use in Amsterdam, London and Kobe, Japan, he said. Marjolein van Huygevoort At the KWR Water Resources Institute in Nieuwegein, The Netherlands.

“A normal lawn stays cool because the grass itself evaporates,” she says, “so this system mimics that natural situation by letting the water rise and evaporate.”

Van Huygevoort says many cities and sports venues are installing artificial turf fields because overuse can damage natural grass. Even in warm climates like those in Northern Europe, the sun can heat the plastic surface to about 70°C (158°F), not only damaging the health of athletes but also warming the air in urban areas, a situation that will only get worse with global warming, he says.

Inspired by A “blue-green roof” that collects rainwater for a cooling effectVan Huygevoort and her colleagues built a toy-sized mock-up of the playground in a climate-controlled lab, with a water-retention unit below the surface topped with a two-centimeter-thick cushioning pad with thin irrigation cylinders embedded inside.

Filled with mineral wool fibres that act like a sponge, these “capillaries” slowly wick water up into a thin layer of sand at the bottom of the artificial turf surface. In a heated laboratory environment, the irrigated water evaporates from the sand, creating a cooling effect on the surface.

Encouraged by these results, the team built a 25-square-metre test site in Amsterdam containing irrigated natural grass. During a heatwave that recorded a maximum temperature of 29.8°C (86°F), the conventional artificial grass reached 62.5°C (145°F). The researchers found that Self-cooling lawnBut the temperature never rose above 37°C (99°F), just 1.7°C warmer than on a natural grass field. Even the air above the water-cooled turf was cooler, which helped keep temperatures down across the city, van Huygevoort said.

The system is based on a design in which the rate at which the water level rises and the evaporative cooling process depend on various natural factors, such as weather conditions. “So water only evaporates when there is a demand for cooling,” says van Huygevoort.

A reservoir beneath the grass can store about 512,000 litres of rainwater beneath the floor of a standard 100-metre by 64-metre football pitch, she says, and capillaries in the buffer pad can store another 96,000 litres, meaning the field should be useful for absorbing large amounts of water during storms, van Huygevoort says.