For millions of Canadians, the soundtrack to summer isn’t the latest beach-friendly banger. It’s the hum of air-conditioning. According to Statistics Canada, 83 per cent of Ontario households now use AC to ride out the province’s increasingly ferocious heatwaves. But a sweat-free home comes at a price — and we’re not just referring to the hefty hydro bill. Together, AC and refrigeration account for around 10 per cent of global greenhouse gas emissions. That figure is expected to rise sharply in the coming years.
In Canada, which is warming twice as fast as the global average, new buildings may eventually use more energy for cooling than heating. “That’s a big shift in what you would typically expect in a climate like Toronto’s,” says David MacMillan, a manager in the city’s Environment and Climate Division.
Some experts see a worrying feedback loop forming. As temperatures rise, more people crank up the AC, which further contributes to global warming.
To break out of this cycle, scientists are racing to develop new ways to keep buildings cool without boiling the planet.
Why is air-conditioning so bad for the climate?
AC units gobble electricity. According to data out of Texas, electricity demand on hot days increases four per cent with every degree the temperature rises. When everyone in a region is turning their cooling devices up to 11, grid managers must ramp up power generation, which often means drawing on older and dirtier backup sources. In Ontario that may involve activating gas plants, but elsewhere the options may generate even more pollution. When working at full tilt during heatwaves, Shanghai’s massive Waigaoqiao power station burns as much as 800 tonnes of coal an hour.
These demand spikes are exacerbated by the inefficiency of many AC systems. The International Energy Agency says the average unit bought by a consumer performs less than half as well as the most efficient products. In many cases, the systems available today would be recognizable to the buyer’s grandparents. “When you think about AC, that technology is 50 years old and nothing has really changed,” says Evelyn Allen, CEO of Evercloak, a Kitchener-based climate tech company.
What are the alternatives?
One solution is at Toronto’s doorstep. Lake Ontario is a year-round source of chilled water for Enwave’s deep lake water cooling technology. Using a pumping station near the Rogers Centre, the system draws water from the lake, cleans it and circulates it through a vast network of pipes to cool around 100 buildings downtown. Last year, Enwave added an additional water intake pipe, which stretches three kilometres into the lake and will allow the company to expand the solution to reach more buildings.
In total, the system can reduce electricity demand by 60 megawatts a year. Cameron Leitch, director of solutions and innovations at Enwave, says the technology is roughly twice as efficient as a conventional cooling plant. “At a city scale like this, the impact on the electricity grid is pretty significant.”
While lake cooling works effectively downtown, the vast majority of Toronto’s half-a-million structures are beyond its reach. “Heat pumps will do most of the work as we seek to reduce emissions,” says MacMillan. These energy-efficient pumps warm and cool buildings by moving heat in and out of the structures as needed.
Heat pumps often exchange heat with the air or the ground, but another less obvious source is being explored at Toronto Western Hospital. A project is underway there to use the thermal energy from wastewater in sewers to provide up to 90 per cent of the hospital’s heating and cooling needs. This unconventional medium works well “because it’s surprisingly warm,” says MacMillan. “Wastewater contains tremendous amounts of energy that are constantly replenished.”
But people say it’s not the heat — it’s the humidity. How does that factor into the equation?
“Humidity has a huge impact on energy use and how comfortable we are in a room versus just air temperature,” says Evercloak’s Allen. Swampy days feel disgusting because the air is so saturated with moisture that sweating no longer works to keep the body cool.
But reducing humidity is tricky. AC and dehumidifiers condense moisture out of the air by cooling it, but the process is energy intensive. Meanwhile, desiccants used in climate-controlled industrial settings can actually generate heat when they absorb water.
Evercloak believes the solution lies in a substance called graphene oxide. It’s a chemical derivative of graphene, an almost miraculous material that can be a million times thinner than a human hair yet stronger than steel. Evercloak uses graphene oxide to create ultra-thin membranes with nanopores that allow water vapour to pass through while keeping air out. Essentially, the technology can be used to suck water out of the air, and Evercloak claims it can cut AC energy requirements by 50 per cent.
“AC is not going away,” says Allen. “So, coming up with solutions where we can mitigate its energy use and apply those in smart ways is going to be really important.” The company is focused on industrial and commercial applications where precise control of humidity and temperature are required, such as pharmaceutical, battery and electronics manufacturing. But Allen believes its technology could eventually be used in offices and residential systems.
What else can we do?
While technology can provide some answers to our cooling conundrum, architectural historian Daniel Barber suggests we need to look more deeply at how we build our cities and how we live in them. One ray of light, he says, is that architects are thinking carefully about how to lessen dependence on mechanical cooling. Techniques like shades and passive ventilation were commonly used in the early 20th century, before AC emerged and pushed buildings to become sealed boxes of chilled air.
But Barber believes we must go further if we hope to wean ourselves off our addiction to artificially controlled climates. We need to recalibrate our behaviours, habits and expectations based on the conditions. “If it’s hot out, maybe my working hours will be from 5 p.m. to midnight, instead of nine to five, because it’s a cooler experience,” he says. “We as societies, as cultures have to transform ourselves.”
Find out more about how technology is changing how we keep cool on the MaRS podcast Solve for X: Innovations to Change the World.
David Paterson writes about technology for MaRS. Torstar, the parent company of the Toronto Star, has partnered with MaRS to highlight innovation in Canadian companies.
