Comment & Analysis

The challenges of cooling in an age of warming ​

Mike Davis MEng AMIMechE, Graduate Engineer, Infrastructure Division, Atkins

...our thirst for cooling is now at risk of becoming one of the key threats to global progress in tackling climate change
...our thirst for cooling is now at risk of becoming one of the key threats to global progress in tackling climate change

An overheating problem in UK housing points to an impending global challenge of how we stay cool on a warming planet. The solution could pose a major threat to progress on climate change.

UK homes are not fit for the future. That is the alarming conclusion of a report on the ‘Future of UK Housing’ published last month by the Committee on Climate Change (CCC). Its findings are unequivocal: greenhouse gas emissions from UK buildings need to reduce further and faster if the UK is to meet its legally-binding climate change targets. Our housing also needs urgent adaptation to cope with a future of more frequent hot summers, water scarcity and increased flood risk.

The challenges this presents will be particularly acute as we seek to meet the future energy demand for mechanical cooling, which is most commonly used for air conditioning (AC). This is set to rise strongly as more and more energy is used to cool down a population living on a warming planet. Unfortunately, this will produce more greenhouse gas emissions, the very cause of the warming in the first place.

The benefits of cooling go far beyond the well-known positive effects on comfort, health and well-being of building occupants. It is also responsible for cooling the data centres behind the technology we use, for production processes of the goods we buy and for safe storage and transport of the food and medicines we need. Some even charge it with influence in politics. In his widely-cited analysis, author Steven Johnson claims that air conditioning was responsible for electing Ronald Reagan, thanks to the demographic changes it caused by drawing Americans south to retire comfortably in the Sun Belt.

However, once a great enabler of human progress, our thirst for cooling is now at risk of becoming one of the key threats to global progress in tackling climate change.

So, how do we both be cool and be green? With its temperate climate and relatively advanced knowledge of low-carbon technology, this should be easier to solve in the UK than in many other countries. However, the CCC’s findings show that progress on reducing emissions from UK buildings has stalled (they actually rose in 2017), and that 4.5 million homes currently overheat, even in cool summers. As hot summers become more common and our population ages, the CCC warns of an increase in heat-related mortality if no action is taken.

The construction industry and government need to ensure that as much of this overheating as possible is mitigated by passive measures (such as adoption of natural ventilation strategies and solar shading). However, where this falls short, mechanical cooling will need to step in, bringing with it a demand for green electricity.

The fact that the UK faces this challenge is indicative of a much larger global issue. In the coming decades seismic shifts in the global economy will combine with rising temperatures and population growth to drive a phenomenal surge in cooling demand worldwide.  

Central to this will be the dominant rise of today’s emerging economies, with countries such as India, Indonesia and Mexico set to rank amongst the largest in the world by 2050.

This has a significant impact on cooling. First, a huge proportion of this growth will occur in the heat of the tropics and subtropics, where the need for cooling and dehumidification is high but current AC ownership is low (only 5% of households in India have it installed). It will also lead to billions of people joining the world’s middle classes, exacerbating the demand for ‘comfort’ cooling as income levels rise and living standards improve.

Urbanisation will accentuate this further, as the growth of huge urban conurbations enhances what’s known as the ‘heat island’ effect.

These trends will be dramatically reflected by changes in the global AC stock, which the International Energy Agency forecasts to rise to an astonishing 5.6 billion by 2050.

Producing green electricity to run these units is not the only issue. Even if all electricity was hypothetically made 100% zero-carbon tomorrow, the climate would remain exposed to the risk posed by refrigerants, substances used by cooling machines that can be 1000 times worse than CO2 as greenhouse gases in some cases. Agreements such as The Kigali Amendment aim to phase out the most harmful of these, potentially saving a staggering 80 billion tonnes of CO2 equivalent emissions by 2050. However, to be effective it needs to be widely-ratified and properly enforced (America is one country which is yet to do so). Refrigerant leakage is also likely to occur on disposal of life-expired equipment, potentially around 15 years after a ban is imposed.

In summary, we appear to be on the cusp of a period of global economic growth that will be more cooling-intensive than ever seen before. The electricity demand for this cooling will need to be serviced, in many cases by some of the world’s most carbon-intensive power infrastructure. Added together with the dangers of insufficient control of refrigerants, and the scale of the cooling conundrum really begins to hit home. No time can be wasted in finding a solution.

This is a member guest blog and the views expressed do not necessarily represent the views of the IMechE.

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