Self-cooling turf can make blistering sports more bearable

Exercising outside has become exceptionally enjoyable. Renowned international athletes recently contributed to a report stating: extreme heat can pose safety risks during the Olympic Games in Paris this year. Just last month, the South American Football Federation after FIFA years earlier, officially changed the rules to take into account “rising temperatures due to climate change.” These heat problems are about to worsen temperatures rise and more communities replace grass with easier-to-maintain artificial grass. Although more durable, artificial grass has difficulty absorbing and retaining water, ultimately leading to higher surface temperatures. sometimes almost 170 degrees Fahrenheit.

Researchers at the KWR Water Research Institute in the Netherlands sought to tackle these sweltering grass temperatures by creating a new, ‘evaporative cooling’ artificial material capable of capturing rainwater and using it to lower the temperature on the surface of a field. The research, published this week in Boundaries in sustainable cities, found that surface temperatures on their custom turf were 46 degrees cooler than a modern artificial turf and nearly the same temperature as natural grass. If implemented on a large scale, researchers believe these types of self-cooling turf could potentially reduce the risk of serious heat-related injuries and even help improve storm drainage in urban areas where rainwater is not well absorbed by traditional artificial turf.

“Including an underground water storage and capillary irrigation system in artificial grass fields can lead to significantly lower surface temperatures compared to conventional artificial grass fields,” said hydrologist Marjolein van Huijgevoort of the KWR Water Research Institute in a statement. “A significant evaporative cooling effect is achieved with circular water management on location under the field.”

Evaporated rainwater can make turf almost as cool as natural grass

Natural grass is generally preferred over artificial alternatives, both in terms of cooling and water drainage, because water can seep into the soil organically. However, sports fields, and even an increasing number of parks, have switched to artificial grass in recent years because of its ease of maintenance. The researchers used the natural water absorption of grass as inspiration and created their own turf with an open water storage layer directly under the turf and the shock pad. This water layer collects and stores rainwater. Capillary cylinders composed of hydrophilic rock wool fibers are then used to transport the water back to the surface where it evaporates. Ultimately, the evaporated water naturally cools the grass surface.

Researchers tested their self-cooling turf with traditional grass and natural grass on a warm, sunny summer day in the Netherlands in 2020. Surface temperatures on their self-cooled turf were 98 degrees Fahrenheit. That’s hot, but nothing compared to traditional turf, which reached a whopping 144 degrees Fahrenheit. Additionally, the self-cooling turf was nearly the same temperature as the natural turf, which read 101.6 degrees Fahrenheit.

Although other research has previously looked at intermittent cooling of artificial grass pitches with sprinkler systems, this usually only provides limited relief in the short term. Constant watering can also damage or affect the playability of the sports grass. The KWR researchers say this new approach improves on these efforts by storing naturally occurring rainwater to cool a field when needed. The self-cooling turf also reportedly resulted in slightly cooler temperatures above the field surface. In addition to the cooling effects, researchers say the water-absorbing field could also help reduce stormwater runoff, which could in turn combat urban flooding. Mediocre drainage systems and an abundance of concrete are reportedly contributed to an increase in storm-related flooding during the past years.

Researchers say their new cooling system is relatively easy to implement, but not necessarily cheap. Installation costs for a self-cooling field can be roughly double that of traditional grass. And while the experiment focused on small 5×5 meter lawns, real-world fields could easily eclipse that. Yet those upfront costs may only tell part of the story. Heat stroke and other health-related harm or damage to agriculture due to poor drainage themselves impose long-term costs that, in theory, could potentially be mitigated with cooler grass on a large scale.

“The investment required for a cooled standard field is higher than for a conventional field,” the researchers write. “However, this investment ensures that the field becomes part of the on-site water management and provides a cooler and safer field for the athletes, based on natural evaporation of retained (rather than drained) rainwater.”