An Australian study conducted by UNSW Sydney has unveiled a groundbreaking strategy that could reduce the scorching temperatures of Riyadh, one of the world’s hottest cities in a desert climate, by up to 4.5°C.
This innovative approach combines highly reflective ‘super cool’ building materials, irrigated greenery, and energy retrofitting measures.
Published in Nature Cities, the study is the first of its kind to investigate the large-scale energy benefits of modern heat mitigation technologies when applied within a city. The research was conducted in collaboration with the Royal Commission of Riyadh, offering a potential solution to a persistent challenge faced by many urban areas worldwide.
UNSW Scientia Professor Mattheos (Mat) Santamouris, Anita Lawrence Chair in High-Performance Architecture and senior author of the study, emphasised the transformative potential of these technologies.
“The project demonstrates the tremendous impact advanced heat mitigation technologies and techniques can have to reduce urban overheating, decrease cooling needs, and improve lives,” he said.
Riyadh, the capital of Saudi Arabia, endures extreme temperatures exceeding 50°C during summer, making it one of the hottest cities globally. The combination of rapid urbanization and climate change intensifies this heat, leading to higher energy consumption and adverse health effects.
Prof. Santamouris highlighted the key factors contributing to Riyadh’s extreme heat, stating, “Limited greenery and extensive artificial surfaces, like asphalt and concrete, trap heat, exacerbating the city’s temperature. Additionally, vehicle emissions and industrial activities contribute to the heat buildup.”
The study employed large-scale cooling simulations, evaluating various heat mitigation scenarios for Riyadh’s Al Masiaf precinct.
It considered factors such as super cool materials, types of vegetation, and levels of energy retrofitting. The results revealed the potential to reduce the city’s outdoor temperature by almost 4.5°C during summer while improving cooling energy conservation by up to 16 percent.
The recommended heat mitigation scenario for Riyadh includes implementing super cool materials in building roofs and significantly increasing the number of irrigated trees for enhanced transpiration cooling. In contrast, the blind application of cooling techniques, lacking advanced scientific optimization, could lead to a substantial temperature increase in the city.
Prof. Santamouris emphasised the broader benefits of cooling the city, such as improving thermal comfort, reducing health issues, lowering pollutant concentrations, and enhancing human productivity. Previous research has also demonstrated a reduction in heat-related deaths when similar cooling strategies were implemented in other cities.
The study also explored the energy impact of retrofitting measures for all 3323 buildings in Riyadh alongside urban-scale heat mitigation technologies. Combining these technologies with energy retrofitting options, including improved windows, insulation, solar, and cool roofs, could potentially reduce cooling demand by up to 35 percent.
Prof. Santamouris sees these findings as a significant step towards sustainability, stating, “This represents a substantial reduction in energy needs for Riyadh, reducing cooling costs and improving the quality of life for its residents.”
The research team now aims to collaborate with the Royal Commission of Riyadh to implement the tailored heat mitigation plan, marking the world’s largest initiative of its kind.
“Once implemented at the city scale, these advanced heat mitigation technologies will deliver important health, sustainability, and economic outcomes for the city for years to come,” concludes Prof. Santamouris.
The research team included experts from the University of Sydney, Lawrence Berkeley National Laboratory, the Royal Commission of Riyadh City, the University of Calcutta, and the University of Athens.
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