Cold air to heat a home? How heat pumps work

Heat pumps are the green way to heat a house…with a catch

Lesson summary

Hi there everyone, it’s Jeff and this is Plain English, where we help you upgrade your English with current events and trending topics. Every Monday and Thursday, I pick something in the news, I pick something going on in the world, something of interest, and I share it with you here at Plain English. And that way, you can learn new words and start thinking in English. And in the second half of the audio lesson, I show you how to use an English expression.

Today’s story is about heat pumps. Heating and cooling buildings is energy-intensive—and it releases greenhouse gases. But heat pumps are a way to heat and cool buildings at a much lower environmental cost. If you’re into science and engineering—this is for you. You’ll learn how heat pumps use even very cold air to heat a house.

And, fittingly, the expression I’ll show you today is “heat up.” This is a phrasal verb, and I’ll show you two ways to use it. I’ll also show you when to use “heat up” and when to use “warm up.”

As always, we put the full transcript with quizzes, exercises, translations, and more all at PlainEnglish.com. Today’s lesson is number 682, so that means all the lesson resources are at PlainEnglish.com/682.

Heat pumps are the green way to heat a home

Cars and trucks pollute . And we’ve all heard that electric vehicles can help reduce greenhouse gas emissions . But in areas with hot summers and cold winters, heating and cooling buildings can emit almost as much greenhouse gas as driving cars . So what’s being done to reduce the emissions of buildings?

One popular answer these days is heat pumps .

In cold-weather places , most buildings are heated with a furnace or a boiler . A boiler uses oil or gas to heat water. The hot water passes through metal radiators installed in a building’s interior. The heat from the metal coils radiates out to warm the room .

A furnace burns typically oil or natural gas to generate hot air: it then blows the heat into the house through ductwork .

Both furnaces and boilers burn fossil fuels to generate heat. And this is problematic for two reasons. First, environmental : they release greenhouse gasses. Second, political : oil and gas sometimes come from unfriendly parts of the world. Until recently, Europe, and Germany specifically , bought a lot of its gas from Russia.

But now, governments are turning to heat pumps to help reduce emissions and rely less on imports of oil and gas.

Heat pumps are the new, old thing. Heat pumps have been around since the late 1800s and they have been used in homes since the 1960s. But they were never as efficient or effective as furnaces or boilers, so they haven’t been widely adopted .

The new versions , though, are better. Let’s take a look at how they work.

In short, heat pumps take the thermal energy from the air outside and they move that thermal energy inside. This seems counterintuitive : how can cold air heat a home? Even on a cold day, there’s thermal energy in the air outside. It feels cold to you, as a human, but there’s still heat in the air. The trick is to extract the heat from the outside air and move that heat inside. And for that, a heat pump uses a chemical called a refrigerant .

A heat pump works in cycles . At the beginning of a cycle, the chemical refrigerant is a very cold liquid inside metal coils . The pump draws in air from outside. The air is cold to us, but it’s still warmer than the refrigerant. As this air flows over the coils , the refrigerant heats up just a little—but that’s enough to turn it into a gas.

Then, the pump compresses this gas into a much smaller space , increasing its pressure . As you might remember from science class, if you increase the pressure of a gas, you increase its temperature.

Now, the refrigerant gas—still inside the metal coils—the gas is under a lot of pressure and it’s hot. This is what we want! Next, a fan blows air over these hot coils, transferring the heat from the coils into the air in the house. The pump then releases the pressure on the refrigerant, and the cycle repeats.

The beauty of this is that the energy comes from the air outside. A little electricity is needed to operate the fans and the pumps. But this is small compared to the amount of heat that makes it into the house.

The best part? When it’s hot outside, just reverse the process of the heat pump, and now you have a central air conditioner . There’s no need to have a separate air conditioning unit.

This is an elegant , energy-efficient solution to heating and cooling a building. So, if that’s the case, why haven’t heat pumps been popular before? For one thing, the refrigerants—the chemicals—haven’t always been as good as they are now . So for a long time, heat pumps were not an option in very cold weather.

Second, heat pumps are more complicated than boilers or furnaces. When oil and gas was cheap, and when nobody was thinking about pollution and greenhouse gases, it just didn’t make sense to choose a complicated option over a simple one.

But now the math is starting—starting—to tip in favor of the heat pump over the traditional furnace or boiler.

Much like the transition to electric cars, the transition to heat pumps is not going to be cheap or easy. Heat pumps are a lot more expensive than traditional furnaces. There’s a shortage of workers who know how to install and service them . That further drives up the cost and limits the speed at which heat pumps can be adopted.

In the U.S. and Europe, government subsidies help offset the extra cost of a heat pump. But even with subsidies, they’re expensive. And furnaces and boilers can last ten, twenty, thirty years or more. So the cycle of replacing this equipment is much longer than the cycle of replacing passenger cars .

Jeff’s take

You guys know…science is like a foreign language to me. So, if you didn’t quite catch that part about how a heat pump works…don’t worry. You can listen to it again. You can read the transcript . Or, I have another option. The Guardian newspaper has a great graphic that finally helped me understand the science of how this works. I am operating at about a ten-year-old’s level of science comprehension . So I needed a really basic explanation, preferably with lots of pictures.

And I found one! So I’m going to put it in “Dig Deeper .” This is the section of the lesson, of the page on PlainEnglish.com, where I put links to articles and videos about the main topic. This is a great interactive graphic with really good explanations that I bet you’ll understand.

Go to PlainEnglish.com/682. Click on the main story. Then find the tab called “Dig Deeper” and you’ll see the link there. And the picture you see at PlainEnglish.com/682—that’s a picture of a heat pump outside a building.