Leading the Charge in Urban Cooling Innovations at UNSW Sydney
In a world grappling with rising urban temperatures and the urgent threat of climate change, innovative solutions to cool our cities are more important than ever. At the forefront of this crucial effort is Scientia Professor Mattheos Santamouris from UNSW Sydney, whose pioneering work, highlighted in Nature Cities, showcases groundbreaking techniques to combat urban overheating, with a special focus on the sweltering city of Riyadh, Saudi Arabia.
Over a rigorous three-year period marked by the challenges of the COVID-19 pandemic, Professor Santamouris and his team undertook an ambitious project to address the extreme heat in Riyadh, where temperatures can soar to an incredible 45°C. Their comprehensive research explored the impact of ‘super cool’ building materials, the introduction of green spaces, and the application of energy-efficient retrofits, leading to a strategy that could reduce urban temperatures by as much as 5°C. This achievement marks a pivotal step in improving urban living standards, cutting down on energy usage, and enhancing the quality of life for residents.
In our interview, we explore the essence of their trailblazing research, highlighting the strategies deployed, the challenges faced, and the profound influence their findings have on urban planning and sustainable architecture around the globe. By addressing the critical issue of urban heat and advancing environmental sustainability objectives, the work of Professor Santamouris and his team at UNSW Sydney charts a course towards a cooler, more sustainable urban future, redefining heat mitigation practices for cities everywhere.
Can you detail the main goals and the time frame of your research focused on mitigating urban heat in Riyadh?
Our research project extended over a three-year period, which was notably impacted by the COVID-19 pandemic and the associated travel restrictions. This study was initiated in response to the extreme summer temperatures in Riyadh, often exceeding 45°C, posing significant challenges to the city’s livability and energy consumption. At the request of the Royal Commission of Riyadh, we embarked on a mission to discover effective methods to cool the urban environment, aiming to both enhance resident comfort and reduce the reliance on energy-intensive cooling solutions.
To tackle this challenge, we started with an in-depth simulation analysis covering Riyadh’s urban landscape. This involved a detailed examination at a resolution of 500 meters by 500 meters, integrating satellite imagery and data from ground stations to accurately chart the city’s heat distribution patterns.
Our investigative process included the evaluation of a variety of heat mitigation approaches. This encompassed the application of innovative cooling materials, known for their superior cooling properties, alongside the strategic integration of green spaces, evaluating the impact of both irrigated and non-irrigated vegetation. Employing advanced simulation techniques, we carefully assessed the efficacy of these diverse strategies in combatting urban heat.
The findings from our comprehensive study were promising, indicating the potential to significantly decrease Riyadh’s peak temperatures by as much as five degrees Celsius. Moreover, these strategies were found to be capable of substantially reducing the energy demands for cooling buildings by approximately 35%, showcasing the tangible benefits of our proposed heat mitigation methods in addressing urban overheating issues.
Can you explain what heat mitigation management is?
Heat mitigation management comprises techniques and innovations designed to control the Earth’s thermal environment by directing the flow and dispersal of heat. Essentially, all beings, humans included, release infrared radiation, which ascends into the atmosphere and is intercepted by greenhouse gases, only to be partially re-emitted back towards the Earth. Earth’s capability to sustain a stable, habitable temperature largely hinges on the atmospheric window, an integral part of our atmosphere that permits a fraction of this Earth-emitted heat to dissipate into space. To harness this natural cooling avenue, cutting-edge materials have been introduced, aiming to specifically exploit this atmospheric window to bolster Earth’s inherent temperature regulation abilities. These pioneering materials are engineered to emit heat in such a manner that it efficiently traverses the atmospheric window, venting into space and thereby lessening the heat load on our planet. This strategic manipulation of heat emission and atmospheric science forms the crux of heat mitigation management, ensuring the maintenance of Earth’s thermal equilibrium. In the absence of this atmospheric window, Earth could potentially experience extreme temperature conditions, rendering it as inhospitable as Venus or Mars. Thus, the creation and application of materials that effectively utilize this window mark a critical leap forward in our global temperature management strategies.
How do ‘super cool’ building materials, greenery, and energy retrofitting work together in your study to lower urban temperatures?
In our study, we focused on leveraging ‘super cool’ or photonic materials known for their exceptional reflective properties and high emissivity at the atmospheric window. This unique characteristic allows these materials to release absorbed heat directly into space, bypassing the atmospheric window, which in turn reduces the heat accumulation around the material and cools the immediate environment.
Additionally, we assessed the effects of both reflective and cooling materials, which, while also reflecting solar radiation and emitting heat, do so over the wider infrared spectrum, not exclusively through the atmospheric window. This broader approach aids in diminishing heat absorption, offering a generalized cooling effect across urban spaces.
The role of vegetation, including both irrigated and non-irrigated greenery, was another critical aspect of our research. Integrating green spaces into urban areas serves as a vital mechanism for cooling, as the type of vegetation selected and its maintenance are key to achieving the best cooling outcomes. In Riyadh’s case, we chose local tree varieties that are resilient to high temperatures. These trees, when properly watered, support the natural process of water circulation and evaporation, aiding in temperature reduction. Conversely, trees that lack sufficient irrigation, particularly under extreme heat, may not only fail to provide cooling but could also contribute to increasing local temperatures due to the dark pigmentation of their leaves which inhibits effective water evaporation.
Our comprehensive analysis concluded that a combination of employing ‘super cool’ materials and ensuring the presence of well-irrigated greenery constitutes the most effective strategy for lowering urban temperatures. The strategic selection and maintenance of heat-resistant vegetation, coupled with adequate irrigation, emerged as essential factors for harnessing these cooling advantages. Within the context of Riyadh, meticulous planning and upkeep of the urban green infrastructure are crucial steps toward achieving a notable decrease in urban heat.
How do the reflective building materials created by the High-Performance Architecture Lab stand out from traditional building materials in terms of cooling urban environments?
Our Australian lab has developed unique materials known for their outstanding reflectivity, intended primarily for roofing applications rather than sidewalls. These materials are part of a global innovation trend, with similar developments occurring worldwide. Their main advantage lies in their dual capacity to reflect sunlight and emit heat via infrared radiation directly through the atmospheric window, a band in the atmosphere measuring between 7 to 13 micrometers. This allows the materials to vent heat straight into space, bypassing the immediate atmospheric layers and thereby reducing the urban heat load.
Distinct from conventional materials that tend to absorb and then emit heat back into the environment, our materials function like a diffuse mirror, reflecting sunlight without causing glare or brightness issues. This property significantly contributes to urban cooling by preventing additional heat accumulation.
A notable benefit of these materials is their ability to decrease a building’s need for cooling by as much as 50%, a finding we reached in collaboration with the Lawrence Berkeley National Laboratory (LBNL) at UC Berkeley. This achievement highlights the effectiveness of our materials in cooling urban areas and the importance of international collaboration in developing such technologies.
Could you share the challenges your team encountered during the cooling, climate, and energy simulations for the Al Masiaf precinct in Riyadh, and how you addressed them?
Launching this project was challenging, especially as it was our inaugural effort to apply such solutions on a large urban scale. Tailoring our innovative building materials for city-wide use involved a detailed and time-consuming optimization process. At the beginning, there was considerable uncertainty regarding the most effective strategies, given the unprecedented nature of our task. Nonetheless, through a process of continuous experimentation and adaptation, we managed to navigate these challenges successfully.
Initially, our focus was on materials with high reflectivity intended for roofing. As our work evolved, we developed new materials with comparable thermal benefits but without the high reflectivity, making them suitable for use on vertical facades and pavements. This was a significant step forward, increasing the versatility and potential impact of our solutions.
Our research covered Riyadh extensively, but we concentrated our efforts on implementing energy-saving solutions within the central Al Masiaf area. This specific focus helped us fine-tune our approach, allowing for adjustments that could later be scaled up to benefit the entire city and potentially be applied in other urban areas.
What are the expected impacts on Riyadh’s energy consumption and public health from the projected temperature decrease of up to 4.5°C?
The challenge of urban overheating is intensifying issues related to energy use and public health, with climate change and city growth pushing urban temperatures even higher. By 2050, we anticipate that cities could see their nighttime temperatures rise by four to five degrees and daytime temperatures by one to three degrees, affecting energy demands, health, and economic conditions significantly.
Short-term benefits of cooling urban areas by up to 4.5°C include a reduction in the need for air conditioning, which in turn lowers energy consumption, diminishes heat-related illnesses and deaths, and lessens the intensity of urban heat islands. Over the long haul, these temperature drops are expected to decrease the peak demand for electricity substantially, reducing the necessity for new power generation facilities that are only active during periods of highest demand.
Our research has shown that applying reflective roofing materials can reduce the demand for air conditioning by 40 to 45%. Coupled with other strategies, such as those implemented in Singapore, it is possible to construct buildings that have minimal to no cooling energy requirements, showcasing the role of advanced technology in developing zero-carbon or zero-energy structures even in warm, humid climates.
Addressing urban heating comprehensively involves significant decarbonization efforts, estimated to cost around 1.6 trillion USD annually until 2050. The solution goes beyond just financial investment, extending to ensuring that low-income groups, particularly in developing nations, have access to affordable, local solutions that provide substantial benefits without necessitating expensive technology imports.
In essence, successfully reducing temperatures in cities like Riyadh could bring significant and wide-ranging benefits, from energy savings and improved public health to reduced economic strains from overheating. Moving forward, a combination of cutting-edge technology, forward-thinking policies, and inclusive strategies will be key in catering to the diverse needs of the global population.
How can cities effectively select and implement heat mitigation strategies to avoid unintended increases in temperatures?
Globally, there are inspiring instances of how heat mitigation technologies can be successfully implemented, as seen in the widespread adoption of cool roofing in educational and commercial buildings across India, China, and Japan. These cases illustrate that the right combination of innovative technologies and supportive policies can lead to substantial improvements. For example, the European Bauhaus initiative aims to significantly lower energy use in the construction sector by 2050, improving the overall environmental quality of urban areas. Europe also aims to make 110 of its cities carbon-neutral by 2050, a target that’s actively being pursued. Similarly, in California, specific heat-combating materials are mandated for road construction, showcasing policy backing for these technologies.
Despite these successes, challenges remain, particularly in achieving widespread adoption. It’s essential to promote proven strategies, counteract opposition from industries like air conditioning, and secure support from open-minded policymakers.
Adapting to the specific causes of overheating in each location is vital. For instance, Sydney’s heat issues stem from desert heat advection, requiring different solutions than those effective in other areas. This may mean that strategies successful in one region, such as planting more trees, might need adjustment or alternatives in another.
Addressing urban heat effectively demands a comprehensive strategy that combines innovative technology with targeted policy initiatives. This collaborative approach must navigate industry pushback, harness political support, and tailor solutions to fit the unique climate challenges of each urban area. Without a unified move towards decarbonization and targeted heat mitigation, the impact on cities and their residents could be significant.
Can you elaborate on the significance of irrigation in urban green spaces for cooling and its impact compared to non-irrigated areas?
Irrigation plays a vital role in enhancing the cooling effects of urban greenery. Trees utilize soil moisture for transpiration, a process where water vapor is released from leaves, significantly cooling the air. Without adequate moisture, especially in high temperatures, trees cease their water uptake, stopping transpiration and, consequently, their cooling effect. Moreover, stressed trees under such conditions may release biogenic volatile organic compounds (BVOCs), which could potentially worsen air quality more than automobile emissions. Hence, lacking irrigation, green spaces might inadvertently contribute to higher urban temperatures and increased pollution. Projects like Riyadh’s expansive park developments underscore the value of properly maintained green spaces in mitigating urban heat.
How does your research on urban heat reduction inform urban planning and architecture in cities facing similar challenges?
Our research, relevant to over 400 cities globally engaging in heat mitigation efforts, demonstrates the effectiveness of modern strategies in reducing temperatures by 2.5-3°C. These innovations offer powerful tools for cities to lower heat, improve environmental quality, and enhance public well-being. The critical need for such strategies is underscored by events like the heatwave in Delhi, which significantly impacted worker productivity, highlighting the economic stakes of urban overheating.
What steps are necessary to transition your research findings into practical solutions for Riyadh, and what challenges do you anticipate?
We are in the process of developing new materials projected to lower urban temperatures by 7-8 degrees in the coming 2-3 years, advancing our capabilities to fight urban heating. Moving forward involves overcoming skepticism towards climate change and reluctance towards new technologies. Fortunately, our current knowledge and technological advancements position us well to address these challenges. A proactive approach, utilizing our insights and innovations, is crucial for meaningful urban heat mitigation, aiming to alleviate the complex issue of urban overheating effectively.
The groundbreaking research led by Scientia Professor Mattheos Santamouris at UNSW Sydney, focused on developing sustainable cooling solutions for urban areas like Riyadh, showcases a significant leap towards combating the escalating issue of urban heat exacerbated by climate change. By integrating ‘super cool’ building materials, strategic greening, and energy-efficient retrofits, this study not only promises to substantially lower urban temperatures by up to 5°C but also aims to enhance urban comfort, reduce energy consumption, and improve the overall well-being of city residents. The work emphasizes the necessity for a comprehensive approach that combines technology, policy, and community engagement to address urban overheating effectively. As cities worldwide confront similar challenges, the innovative strategies and outcomes of this research offer valuable insights and methodologies for creating cooler, more sustainable urban environments, highlighting the potential for significant advancements in urban planning and sustainable architecture globally.
Cover photo: Self Portrait, Image credit: UNSW Sydney
