Heat Pumps finally make sense

[This is a transcript with links to references.]

What does civilization mean to you? To me the most essential part of civilization is shelter. Yes, YouTube comes a close second of course. But on top of the list, I have a safe, dry, warm place to live.

And it’s not just me. Residential heating plays a special role in peoples’ life in countries where temperatures outside frequently get a little uncomfortable. But most buildings are currently heated with gas and oil. Globally, the carbon dioxide emissions from residential heating make up 10-12% or so, though they strongly depend on the season.

This is why a lot of governments have pushed their people to install heat pumps. At least where I live those have not been particularly popular – so far. But this might change soon because a major upgrade to the technology is now hitting the market and it’s really good news. Let’s have a look.

A heat pump is basically a type of electric heating. It uses electricity to move heat from one place to another, against the direction the heat’d naturally flow. Your freezer for example also uses a type of heat pump. It pumps warm air out of the pizza and into your room. An air conditioning is also a heat pump, it pumps warm air out of your room and into your neighbour’s garden.

Heating with a heat pump works the same way but in the other direction, it pumps heat into your house by making the outside colder. Or maybe one could say that it pumps cold out of your house.

Guys I’ve been thinking about this sentence for a full hour now. Does it make sense to speak of moving around cold as the negative of moving around heat, but please chime in below.

There are three major types of heat pumps, the simplest one uses air from next to the house. But you can also use a water reservoir if you have one, or air from deeper underground. This has the advantage that the temperature is usually more stable down there, but it requires drilling.

Either way you can use the heat pumps to warm up the air in your house, or the water that you use for heating.

What’s the point? The point is that a heat pump is very energy efficient basically because it just sorts heat rather than creating it. Exactly how much carbon dioxide is released in the operation of a heat pump depends on how you power it, but if you go by energy, it’s half to a third of a typical fossil fuel heating. That’s why most countries have pushed house owners to install heat pumps.

And that partly worked. Heat pumps are on the rise internationally and in some countries it’s been going well: Sweden, Norway and Finland lead the way in adoption with 40% of households using heat pumps already, and in the United States it’s about 15%. But in other countries the uptake has been very slow. In Europe, we have the UK at the bottom of the list with less than 1%, and Germany isn’t doing much better with about 2%.

The problem with heat pumps is that they have limits below what some of us are used to from civilization, and that makes us uncomfortable. Why is that?

Well, you have probably noticed that no matter how long you run your freezer, it doesn’t reach a temperature of absolute zero. That’s because your freezer isn’t entirely airtight, because the container walls also conduct heat, and because the efficiency of the cooling cycle decreases the larger the temperature difference between the inside and outside. This means for all practical purposes, your freezer has a minimum temperature that it can reach.

It’s the same with those heat pumps just that they have a maximum temperature that they can reach, and the larger the temperature difference you want to have, the less well they’ll work. With the heat pumps that have been on the market so far, it’s been really difficult to reach temperatures above 50 degrees Celsius, especially in the winter.

Now you might say you don’t want your room at 50 Celsius anyway and I hear you. But the typical water cycle heating that most houses have with fairly small heating elements use temperatures between 50 and 90 degrees Celsius. That’s because if the heating elements are small you need them to be really hot.

You can make do with lower temperatures if you heat larger areas instead. This is why heat pumps are often used together with floor heating, that way the temperature doesn’t have to be that high. But the floor heating themselves are expensive, and then the insulation of your house also matters for them to work well.

I believe these are the major reasons why in some countries heat pumps have been slow to catch on. They work well in new houses. But many old houses are not well enough insulated for those pumps to indeed heat them.

If you walk through a typical residential street in the UK for example you’ll see lots of brick houses, many of them with wood framed windows. A heat pump just won’t get them warm, and they’re a nightmare to insulate. Even if you insulate them that causes other problems, for example with humidity.

I suppose that’s why the infamous British-born activist group “Extinction Rebellion” now has a splinter group which calls itself “Insulate Britain”. I really admire the change of direction there. They went from raging against human extinction right to “Excuse me, is it possible that we could get some state aid to retrofit our brick walls?”

The issue with old houses in Germany isn’t quite so pressing because a lot of those were bombed down in the second world war.

However, heat pumps aren’t popular here for other reasons, the first is that they’re expensive, even with the support you get from the government, and that electricity is also expensive in Germany. Also, heat pumps make noise because you need to, well, run that pump. And then there’s the issue that most house owners know that heating trends come and go and I guess they figure they’ll just sit it out. At least that’s what I was thinking.

However, it doesn’t look like the heat pump trend is going away, rather it’s just getting started. The reason is that a new generation of heat pumps has just come on the market, and they really make a difference. They use a new refrigerant, that’s the stuff which transports the heat, called R 290 which is a type of propane. This much increases heat pump efficiency.

These new heat pumps reportedly reach temperatures up to 70 degrees Celsius, which is comparable to what your oil or gas heating delivers. Even better, the R 290 refrigerant is one that doesn’t damage the ozone layer when it escapes.

The idea itself is not new, it’s been around for years, but it wasn’t until last year that it hit the consumer market big time. Lots of companies are now selling the new heat pumps. Mitsubishi for example has declared R290 the future of home heating, LG agrees. Panasonic is on it too. The things are all over the place.

The praise of R290 is pretty much universal. I’ve tried to dig up criticism but the only thing I’ve found is that R290 is extremely flammable which is not great seeing that the most common problem with heat pumps is that they leak. Then again, these pumps don’t contain a huge lot of the stuff, so I guess the risk is tolerable.

That said, using propane doesn’t remove the problem that heat pumps need more energy the higher the temperature difference you want them to create.

This means that while you could use the new heat pumps to reach water temperatures above 70 degrees, the relevant question is whether that’s any better than just heating with electricity.I guess we’ll find out soon.

The potential of these heat pumps is huge. A recent study found that in the United States alone, heat pumps could save between one and two thirds of carbon emissions from the residential sector, that’s between 5 and 9% of the national emissions. That’s a big chunk.

So I think that’s a good development and it could make a real difference. In principle. In practice, the company which owns our house isn’t even fixing our half-broken oil heating, so I don’t think we’ll see any heat pump here soon, I hope that Insulate Britain is doing better than that.