Extreme heat is getting more extreme. As the planet warms, its hottest days are expected to get more frequent, and heat events could last twice as long. And the air conditioning that helps us get through those sweltering days contributes to that same heat, too.
"As it gets hotter outside, it takes a lot more energy to move the same amount of heat. As things get hotter, you're just a less and less efficient system. And that's kind of a fundamental thermodynamic principle you can't get away from."
Chuck Booten is a senior engineer in the building energy sciences group at the National Renewable Energy Laboratory. He told Newsy both air conditioning and the energy it needs are on the rise.
"Air conditioning is expected to grow in terms of not only the absolute amount of air conditioning, but kind of a penetration, the percentage of buildings that have it is expected to grow," says Booten. "And as things get warmer, if that continues to happen, then the amount of energy needed to keep buildings cool is also going to grow."
For the last three decades or so in the U.S., things have been getting warmer. On average, there have been more annual cooling degree days — when mean temperatures get above 65 degrees Fahrenheit and people are likely to cool their environment to stay comfortable.
But doing this with air conditioning can be a double-edged sword. AC keeps our buildings cool, but individual units vent waste heat to the immediate environment — which some research shows can make cities warmer. And when demand for AC increases, so can heat-trapping emissions, if the energy to meet that demand comes from fossil sources.
By definition, that's a feedback loop. But the right efficiency improvements could help control it. As worldwide demand for AC climbs, researchers are working on everything from refrigerants tailored to specific uses, to systems that control temperature and humidity separately, to fans that don't have to run at full throttle all the time.
"So systems that are not just on or off, but they can modulate based on how much air conditioning is needed. That is becoming more and more common. And there are a lot of energy savings to be had there potentially, too."
Booten says plain old insulation helps, too. The most efficient AC is the one you don't have to run at all.
"I think in most situations, having more insulation on your building so that you just need a less air conditioning load. That is almost universally important."