- Demand for air-conditioning is rising, but providing the electricity required without boosting carbon emissions will be a huge challenge.
- Technology, sensible policy-making and changes in consumer behaviour can all make important contributions.
Cooling is the new heating. Population growth and rising incomes in countries where cooling is needed are teaming up with climate change to cause shifts in demand.
In an Energy Policy article on modeling residential energy demand against the backdrop of climate change, experts from the Netherlands Environmental Assessment Agency predicted that global energy demand for heating will rise until 2030 and then level off. They expect energy demand for air conditioning, on the other hand, to climb rapidly until 2100 and surpass energy demand for heating during the middle of this century.
How do things look today? According to a recent update from the International Energy Agency (IEA), there are about 2 billion air conditioning units in operation worldwide, mostly in residential buildings. These devices are making space cooling the leading driver for increases in demand for electric power in buildings and for the new capacity needed to meet power-demand peaks. The IEA’s Cooling report cites this form of consumption as the most rapidly growing end-use in buildings; in 2019, energy demand for space cooling – which has already more than tripled since 1990 – caused emissions of around one gigaton of CO2 and accounted for almost 8.5% of total final electricity consumption.
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These figures are set to grow. In 2015, the US Energy Information Administration reported that 87% of homes across the United States were already using air conditioning. In contrast, the IEA says that only 10% of the world’s population owns an air conditioning unit, although 35% of world’s people live in countries where the average daily temperature exceeds 25°C. Clearly, there is substantial pent-up demand among people around the globe who don’t yet have the financial resources or the stable power supply required to keep cool.
Denying people the ability to refrigerate food or keep residential temperatures within a range that is conducive to their health can’t be the answer, but even just providing all these new consumers with the required electricity will be a massive challenge. And once we begin to meet the demand, the world doesn’t really have a plan for satisfying these consumption needs in a way that doesn’t place a huge added burden on the environment.
New technologies, governmental policy measures and our behaviour as consumers can all make important contributions here. I see three steps toward more sustainable energy use in cooling.
1. Use sector coupling to increase the share of renewable energy
Sector coupling aims to decarbonize the entire energy system by transferring renewable energy from the power sector to other sectors. This integrated approach would make electricity the backbone of our future energy supply.
In the electricity sector itself, huge investments have increased the global share of power generated from renewables to more than 20% in 2019. Unfortunately, these positive developments had little impact on global carbon emissions. Why? Roughly 60% of global carbon emissions come from uses other than power generation.
The majority of emissions stem from transportation, buildings, industry, heating and cooling. Compared to the electricity sector, we’ve seen very little progress so far when it comes to decarbonizing these sectors.
We now need an integrated approach to decarbonizing all sectors of the economy – an overarching model that enjoys the full backing of policy-makers. As a key part of the energy transition, sector coupling is just such an approach.
Linking sectors together requires two steps. We first need to increase direct electrification of other major sectors; then we need to provide renewable energy to those sectors in a suitable form.
The most promising sector-coupling technology is called power-to-X. This approach involves methods for converting electrical energy from renewable sources into liquid or gaseous chemical energy sources through electrolysis and further synthesis processes. With power-to-X, electrical current is used to split water into oxygen and hydrogen in a way that is 100% free of carbon emissions. As a key technology for the energy transition, hydrogen can be stored, processed or consumed in many ways – for example, as a means to run air conditioning systems on green electricity.
2. Go digital to become more efficient
In addition to replacing hydrocarbons with sources of renewable energy, data-driven energy-efficiency measures can help reduce demand for both heating and cooling.
As areas in which such measures can be applied to boost efficiency in buildings, the International Renewable Energy Agency (IRENA) points to “advanced construction and design techniques, enhanced insulation, and better information and control of energy use with intelligent thermostats”. In industrial applications, IRENA sees potential in technologies like combined heat and power (CHP) units as well as energy-management solutions.
When it comes to boosting efficiency, it’s also worth thinking things through holistically and looking at the individual elements as one system. For example, taking a combined approach to the water chilling and air distribution systems used to cool buildings can save a great deal of energy.
Industrial applications for chilled water systems can typically reduce energy consumption by 20-50%; measured total chilled-water system performance can sink to as low as 0.33 kW/ton. In this way, the Fred Hutchinson Cancer Research Center in Seattle, Washington, improved its building performance and energy efficiency massively and saved about $1.5 million in energy costs over 13 years.
Another effective way to employ data is to use digital twins to enhance the energy efficiency of new buildings. Digital simulations can be used to maximize passive cooling in the design, including natural ventilation and cross ventilation using window placements, louvres, wing walls and solar chimneys. Different materials can also be simulated, such as insulated concrete forms (ICF) or solar reflective paint. ICFs provide high thermal efficiency and limit air infiltration, reducing cooling consumption by around 30%. Solar reflective paints can be applied to the exterior of buildings to help reduce energy absorption from the sun, improving building energy performance. A paint with a solar reflective index greater than 80 is able to decrease cooling consumption by up to 20%, while also mitigating any urban heat island effect.
In addition to visualizing all the geometric data of every element of a building, digital twins can include schedules, budgets and data regarding a building’s energy demand, lighting, fire protection and operations. As a result, a building’s future climatic impact can be optimized before ground has been broken.
What’s more, digital twins can keep on collecting data throughout a building’s operational lifetime. The results deliver useful details on physical stresses, failed components and building usage, allowing facility managers to bring maintenance costs down and keep operations smooth by better planning interventions.
Such data not only supports optimization during operations, it also helps designers, architects and engineers prepare the next generation of a building. This development work aims to achieve a closed loop that links the virtual world of planning with a building’s real-world performance.
3. Turn the dial – save the planet
If we don’t want cooling to run into the same problems as heating has done, we have to ask how we can conserve resources by using cooling systems efficiently. To this end, we need political leaders to initiate a new approach to energy supply that links all sectors into a holistic system. And we need industry to invest further in boosting energy efficiency and employing innovative, digital solutions such as digital twins.
But each of us can also make a significant contribution as an individual without much effort. Simply by raising our thermostat settings to allow a slightly higher temperature during the summer months, or by replacing AC use with a fan on not-so-hot days. Just ask yourself: does one degree of cooling really make a difference? About 30% of the energy we consume in our homes is for heating or cooling. In some countries – in the US, for instance – it’s more than half.
According to the SmarterHouse project of the American Council for an Energy-Efficient Economy, we can save 3–5% on air conditioning costs for each degree Fahrenheit (or for each 0.56 degrees Celsius) that we raise the thermostat. It goes without saying that reducing our energy consumption in this way will do more than save money.
So, turn the dial this summer and help save the planet.