Conditioning the air we breathe

Fahad Badar explores rising air-conditioning demand and how efficient cooling, urban design and AI could reduce energy use and climate pressures.

There are an estimated 1.5 billion air conditioning units in the world today, and the Rocky Mountain Institute, a US-based think tank specializing in energy efficiency, projects that there are likely to be around 4.5 billion by 2050. The compound annual growth rate of the global market is set to be an average of more than 5% this decade, with the value reaching around $260 billion by 2029. The wider HVAC (heating, ventilation and air conditioning) sector is growing at the same rate.

Rising living standards in the emerging economies, growing populations and increased urbanization are contributory trends. Higher temperatures in many regions, attributable to global warming, drive the demand further.

Can the world’s energy supplies provide for a trebling of use? According to the International Energy Agency, air conditioning accounts for around 10% of electricity consumption globally. If the electricity generated for this additional demand is through the burning of fossil fuels releasing greenhouse gases and thereby adding to global warming, there is an obvious vicious cycle.

The problem is acute in India, which has seen record high summer temperatures – reaching around 50 degrees in Delhi in May this year – and is a rapidly urbanizing and developing economy. Temperatures above 40 degrees cause significant risks for humans, especially young children, elderly people, pregnant women and those with medical conditions. A temperature above 45 degrees is inhumane. The World Health Organization advises that the optimal temperature for a human body lies within a quite narrow range of 18 to 24 degrees. 

For many, air conditioning is a necessity, not a luxury. In addition, air cooling systems are needed for computer storage systems and other industrial uses. In the Middle East, very high temperatures are common in the summer. Some air conditioners are used even for outdoor areas – patios that are curtained off, with cool air rising through vents in the paved area. In a country like Qatar, with cheap energy, this is feasible.

Cities could benefit from better design. An effective natural air conditioning system is to have plenty of parks with trees, and more trees lining the streets, providing natural shade. They have a natural cooling effect while tarmac, brick and concrete radiate and intensify heat. In the Middle East the desert can actually be cooler than the city on a hot day. A study reported in the New Scientist in 2021 found that trees in cities can reduce land temperature by up to 12 degrees; interestingly it also found that green spaces without trees have negligible effect.

Natural shade and a greening of cities can lower the energy demand – which could become an urgent necessity in some nations if there are gaps in supply during the transition away from fossil fuels. In addition, there is a need for more energy efficient machines. In 2019 the Government of India joined with the Rocky Mountain Institute of the US to set up a Global Cooling Prize, offering $1 million to the team of engineers who can achieve rapid improvements in energy efficiency of cooling units. The organizers pointed out that the basic engineering of a conventional air conditioning unit had scarcely changed in the 100 years since the US inventor Willis Carrier developed the first unit in the 1920s. 

Two winners were announced. The Indian company Daikin, in partnership with Japanese firm Nikken Sekkei, developed an air conditioning system with two innovations: a multi-split method that optimizes refrigerant flow, and an evaporative cooling system that reduces the temperature of the input air. The Chinese manufacturer Gree, in partnership with Tsinghua University was the other winner: their system integrates advanced vapor compression refrigeration, photovoltaic direct-driven technology, evaporative cooling and ventilation.

There is also potential for artificial intelligence (AI) systems to optimize energy use within buildings. Sensors and data analytics can be used to inform automated control systems. Predictive maintenance – in which sensors detect a part that needs replacing before it breaks down – helps ensure continuous operation and better efficiency.

The continued growth of the built environment demands both better urban planning and smarter technology to prevent a vicious circle in which the machines cooling our buildings relentlessly increase the ambient temperature. Increasingly it appears that there is the learning and the inventions necessary to achieve this.