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How to cool one of the hottest cities on Earth

A first-of-its-kind study has shown the large-scale energy benefits of modern heat mitigation technologies when implemented at a city-wide scale.

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Conducted by University of New South Wales, Sydney, Australia, researchers looked at the Saudi Arabian capital, Riyadh, for their modelling. Although extreme heat is thought to impact more than 450 cities across the world, the case study is among the worst affected, with summer temperatures regularly exceeding 50C. 

Led by Professor Mattheos Santamouris, Anita Lawrence Chair in High-Performance Architecture, the multi-faceted approach to cooling combined highly reflective building materials, developed by the High-Performance Architecture Lab, irrigated greenery and energy retrofitting. Different strategies were developed, utilising various combinations  of ‘super cool’ materials, vegetation types and energy retrofitting levels. The most effective delivered modelling for a 4.5C drop in temperature during the warmest months in Riyadh. 

‘Limited greenery and large artificial surfaces made of conventional building materials like asphalt and concrete trap heat, meaning the city continues to heat up. Additional heat from car pollution and industrial activities also increases the city’s temperature,’ said Santamouris.

‘By implementing the right combination of advanced heat mitigation technologies and techniques, it is possible to decrease the ambient temperature at the precinct scale,’ he continued. ‘For a sweltering city the size of Riyadh, significantly reducing cooling needs is also tremendous for sustainability.’

For energy retrofitting, footprints for 3,323 individual buildings were simulated, alongside the heat mitigation technologies. When the most effective improvements were made – specifically update windows and insulation, solar and cool roofs – the energy demands of cooling also saw huge reductions of up to 35%.

‘This represents a substantial reduction to the energy needs for Riyadh that would help further reduce costs associated with cooling for the city while improving the quality of life for the local population,’ says Prof. Santamouris. ‘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.’

The team now hope a collaboration with the Royal Commission of Riyadh is possible, leading to a roll out of bespoke heat mitigation plans across the city. If this happens, it would be the largest project of its kind anywhere in the world, and could encourage other metropolitan areas struggling with similarly extreme environmental conditions, and a reliance on energy-based cooling, to develop their own roadmaps. 

More on cities and cooling:

British cities rank as world’s most congested

Well-placed trees halve air pollution, Select Committee told

Global Cooling Pledge launched at air con heavy COP28

Image:  M Zaedm

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