Finding ways to keep cool should focus the minds of every architect, planner and regional administrator around the world, if we are to avoid in the future a mass exodus of people from areas where it is increasingly becoming too hot to live.
This summer has shown that the world is warming more rapidly than even the most pessimistic forecasts of the past. In the USA, the National Integrated Heat Health system recorded more than 120 million people at risk from extreme heat on 3 August 2022.
This year, 2022, is the hottest year on record
In Australia, heatwaves have caused more deaths in the past 200 years than any other natural hazard, according to Human Rights Watch.
In Europe, July and August saw three heatwaves bringing record-breaking temperatures, droughts and fires. Most parts of the world experienced highest temperatures ever recorded.
This year’s heatwave was at least 10 times more likely because of human-induced climate change and without climate change the heatwave would have been 2–4 ºC cooler, according to an article in Nature magazine that quotes an international World Weather Attribution research group finding.
This is likely to continue every summer into the future, and to get worse, so the question of how to protect populations is one that should be focusing the minds of every architect, planner and regional administrator around the world.
The electricity demand associated with air conditioning and the chilling of water, particularly during heat waves, is massive, and contributes considerably to peak loads; it has been implicated many times in blackouts as local grids are overloaded.
If we are to protect populations from overheating, while avoiding traditional air conditioning using fossil fuel-fired electricity, which will perversely increase global warming, then we must first of all learn that nature is our friend, says Rachel Kyte, a member of the UN Secretary-General’s high-level advisory group on climate action.
Hot and dry climates
Hot and dry climates and hot and humid climates require different solutions for cooling. In both cases you don’t always need technology to improve conditions: you can plant more trees, paint roofs white to reflect the solar heat back into space, or green them with plants.
Vegetation in urban areas helps to cool the area and provide shade, while ponds and lakes also help to reduce the temperature. Bringing nature back into cities and towns has other benefits including promoting health and well-being.
Architects can design alterations to buildings that include features such as awnings, external shutters and other forms of shading, the ability to utilise cross and vertical natural ventilation and phase change materials to moderate internal temperatures.
The limit to human survival of climate change
But this won’t work in climates that are very humid. We’ve known since 2010 that the limit to human adaptability to climate change is a sustained wet-bulb temperature (a measure of humidity and temperature) exceeding 35°C (95°F).
If there is a high temperature and 100 per cent humidity the human body cannot sweat to cool down. It will therefore overheat. Organs will fail. It is likely to be fatal even to fit and healthy people. In some parts of the world, such as India, we weren’t far off these conditions this summer.
This reflects the shocking opening of Kim Stanley Robinson’s 2019 climate fiction novel, The Ministry of the Future, in which 20 million people in India die in such an event.
In this novel Robinson uses this event to stun the world into action on mitigating and adapting to climate change.
Hot and humid climates
So, what can these parts of the world do? In hot, humid climates shading plus an open-building approach work well in locations where the temperature is tolerable and does not change much from day to night. Daytime cross-ventilation is used to create an internal air flow that helps to maintain comfort levels.
But in these locations people should avoid the use of pools and areas of open water as these encourage insects and humidity.
In locations and situations where this is not appropriate, two possible strategies are available:
- an airtight building with mechanical cooling, which can be driven by renewable energy
- Passivhaus with careful attention to vapour control
Otherwise only air conditioning powered by a decarbonised grid can help the people living in these parts of the world. Unfortunately most of the people who do live in these very humid areas, such as in South Asia, are too poor to afford it, and the local electric grids are likely to be the last in the world to be decarbonised without support from richer countries.
The best way for richer countries to support this is at scale, using solar power.
Solar cooling
Counter-intuitive as it may seem, it is possible to cool water and buildings using solar thermal power. This focuses the sun’s heat to drive a heat engine in the same way that burning coal or gas does.
For solar technology, this is a hugely untapped potential market. Moreover, there is a great match between the energy supply and demand: when the sun is shining the most there is the most power available, and the demand for air conditioning is the highest.
The International Energy Agency has published a roadmap for the implementation of this technology. It outlines a pathway for solar energy to supply almost one-sixth (16.5 EJ) of the world’s total energy use for both heating and cooling by 2050. This would save some 800 megatonnes of CO2 emissions per year – more than the total CO2 emissions in Germany in 2009.
While solar heating and cooling today make only a modest contribution to world energy demand, the roadmap envisages that if concerted action is taken by governments and industry, solar energy could annually produce more than 16 per cent of total final energy use for low temperature heat and nearly 17 per cent for cooling.
Given that global energy demand for heat represents almost half of the world’s final energy use – more than the combined global demand for electricity and transport – solar heat can make a significant contribution in both tackling climate change and strengthening energy security.
