The summer of 2023 not only shattered monthly temperature records, but was also followed by the hottest September ever recorded. Consequently, urban areas saw a steady surge in the demand for cooling solutions.
Feeling the heat
The “cooling degree days” value, a weather-based index that shows the energy required to cool down buildings, has increased significantly over the past four decades (1982-2022) in European cities. It’s 6.9 times in Paris and 3.2 times in Madrid. The International Energy Agency (IEA) predicts that the number of air conditioner units installed in EU countries will double between 2023 and 2050, reaching 275 million units. This is creating a vicious circle; higher air conditioning-use boosts energy consumption and greenhouse gas emissions, potentially accelerating climate change and contributing to rising temperatures, in turn increasing demand for cooling.
Asian cities at the centre
While cities all around the world face increasing cooling demands, Asian cities are way ahead of the curve as they have long grappled with severe heatwaves. Cities in South and Southeast Asia have much higher demand for cooling than European cities. For instance, in 2022, cooling degree days in Bangkok are about 46 times the level of Paris.
Asia is emerging as a pivotal region in both mitigating and adapting to climate change, for two reasons. First, Asia is the largest emitter of CO2 among the world regions, being home to 60% of the world population and generating more than half of global emissions and 46% of global GDP.
Second, Asia is vulnerable to the impacts of climate change due to its geography and socioeconomic conditions. Under climate change, the region faces increasing frequency and severity of heat waves, storms, flooding, and droughts, along with sea level rise, all of which have the potential to inflict long-term harm on both lives and economies. S&P Global Ratings shows that South Asia is 10 times more exposed to physical climate risks than Europe, while the Asian Development Bank estimate that a high emission scenario could cost developing Asia 24% of GDP by 2100.
Looking for sustainable solutions
New techniques are being deployed to keep cool efficiently, including passive design strategies and district cooling systems.
Passive design strategies aim to optimise building elements such as orientation, thermal mass and natural sources of heating or cooling such as sun and breezes, ultimately leading to thermal comfort, energy efficiency, and reduced greenhouse gas emissions.
For example, Rajkot, India has introduced “Smart GHAR III (Green Homes at Affordable Rate)”, which reduces heat gains through windows, walls and roofs. For instance, the project used highly reflective roofing made of glazed tiles to reduce solar heat gain by reflecting rather than absorbing the sun’s rays. It is estimated to reduce peak summer room temperature by over 5°C.
Okinawa, Japan has established a green housing guideline for its semi-tropical climate, including a range of passive design strategies, such as installing heat-blocking rooftops, heat-resistant paint and ventilation block walls.
Cities are also working to make on larger-scale solutions, including district cooling systems. This approach cools water in a central plant, which is sent to various buildings to support air conditioning, eliminating the need for individual buildings to operate their own chillers. For instance, in Bangkok, Thailand, the “One Bangkok” urban megaproject is investing in district cooling infrastructure with an installed capacity of 36,000 refrigeration tons (equivalent to the energy required to produce 36,000 tons of ice at 0°C within 24 hours).
Another unique cooling approach is to use hydro-thermal energy. Seoul, Korea is starting a pilot project using the Han River’s water for year-round energy-efficient cooling and heating for buildings, which is expected to save around 90 megawatt-hours of energy annually. The city’s Lotte Tower, Korea’s tallest building, adopted this technology in 2014, resulting in a 35.8% reduction in energy consumption and a 37.7% reduction in carbon dioxide emissions compared to the same-capacity absorption chiller.
While rising temperatures are concerning cities across the world, Asian cities can and must lead the charge on energy-efficient cooling measures. Success here will not just keep their own citizens cool but – by cutting emissions – help cool an entire planet.
Find out more in the OECD report, Decarbonising Buildings in Cities and Regions.