Earth Notes: KEHS talk: The Truth About Heat Pumps (2024)
Updated 2024-07-28.Many thanks to Peter M for the slides and for delivering the talk!
[00:00]Okay, hello everybody. We installed a heat pump, well it's nearly 15 years ago now, so we were
[00:05]distinctly early adopters of this, and it was really part of a project to try and reduce our carbon footprint, so no calculations about payback period or anything like that. I divided it into "What is a heat pump?" ... there is so much
[00:20]misinformation and disinformation around heat pumps, just try and get everybody on the same
[00:26]same place. "Our experience with owning and living with one of these things for 15 years" and then "Why
[00:33]heat pumps are necessary" really for the country, not just for individuals, so a heat pump. Okay,
[00:40]well most people are absolutely shocked at this price and really when you start to look into them
[00:45]they are extraordinarily complex engineering devices, much much more complicated than a boiler,
[00:51]stuffed full of electronics, compressors, heat exchangers, all sorts of things and you think
[00:57]they're very sort of new things but they're not. The first heat pump was made in 1830, well before
[01:03]anybody thought about gas boiler, you all, each of you probably has three heat pumps, maybe more.
[01:10]You've got one in the fridge, one in the freezer, one in a car, you might have an air conditioning
[01:16]and you might have dehumidifiers. They are everywhere, it's very common technology now, but
[01:21]complicated. Basically what it does is that it pumps heat backwards against temperature. I mean
[01:30]you'll think about your fridge, this is what happens, you know, your fridge, you're making a fridge
[01:39]and the fridge keeps on pumping it out and dumping it back in the kitchen and it's just going round
[01:43]and round in circles and that's what heat pump does. It needs some electricity to work because
[01:55]a gas boiler, the gas boiler or electric heater, you buy the electricity or the gas, you put it in,
[02:00]that's got the energy in it and you release it as heat. So you take the chemical energy in the gas
[02:06]and convert it into heat energy, um, the efficiency is maybe 80 or 90 percent, some of it's waste,
[02:13]some of it goes to the gym and that's fine. With a heat pump, you're not actually converting one
[02:18]form of energy to the other, you're harvesting energy in the environment and pumping it into
[02:23]your house. It takes some energy to run the machine and that energy is not wasted, it is, most of it is
[02:29]retained in the system, so it's not wasted energy, um, but the efficiencies are huge because it's,
[02:37]instead of being saying 90 percent for a good gas boiler, it's 300 percent for a heat pump,
[02:42]so it's harvesting three times as much. Now, when I sort of mentioned it, everybody said,
[02:46]well what happens on a really cold day when it's freezing, surely there's no energy left in the air.
[02:50]Um, well there is lots of energy left in the air, um, you have to think that there is no energy
[02:56]left in the air at minus 273, which is absolute zero. Now, you wouldn't exist in that form at
[03:03]minus 273, but if you think that you're, the environment we live in, it's maybe, you're going
[03:09]to be using a heat pump from when it's about 10 degrees to minus 5 degrees here, and the change
[03:15]in energy in the air over that range, tiny. The temperature difference does affect the heat pump,
[03:21]but it doesn't affect the principle of there being lots of energy in the environment to be harvested.
[03:26]So these are strange devices, um, very reliable, established technology. We went for a heat pump,
[03:38]your house. I thought, well okay, so we better check this. So we went to Daikin's training
[03:44]centre in Woking, where they got lots and lots of heat pumps, and we heard them. They sent them
[03:49]running, and we listened to them, and we thought, well okay, they're not silent, they make a noise,
[03:54]and it's probably a bit noisier than the flu on a gas boiler, because gas boiler makes noise,
[04:00]um, but it's okay, it's going to be okay, or we can live with it. And anyway, what's the equation
[04:05]between climate change and a bit of noise, why these two equated, I don't know why they equated,
[04:10]but people do. It was installed, um, we were the first customers in this company, and it showed they,
[04:18]um, we had three guys. We had a guy who dealt with refrigerants, a guy who dealt with electrics,
[04:23]and a guy who dealt with plumbing, and they were very good, but they never done one before,
[04:28]and they fled after they'd fitted me, and left me with a manual. This, they translated from
[04:35]Korean, I suppose, and my first was like, how on earth can they sell these to the general public?
[04:42]You have to be, I'm an engineer, and I have to be an engineer really to cope with this. I find it
[04:46]very stressful, very difficult, and I find faults, and they have to come back, and you know, I had to
[04:50]commission it and get it running, but we've got it settled, and I think if you went to Octopus now,
[04:54]who are the big sellers of them, it will be absolutely fine. Okay, it's been reliable,
[05:00]it had its first fault a couple years ago. In fact, it was a trivial fault. It took quite a
[05:05]lot of money to fix it, because the diagnostics in the machine are not brilliant. Ours is a very
[05:10]early one, and when it came out with its error code, and I phoned Aiken and said this is the
[05:17]error code, and he said, oh dear, that one covers a whole lot of faults, and we can't really tell.
[05:22]And so they changed lots of parts, which they didn't need to change, but I think machines,
[05:29]you know, it's all got better now. It was really just a solenoid that got a bit sticky, and it
[05:35]actually went into, like cars do, a limp home mode. So it carried on working, so this was in mid-winter,
[05:40]but it carried on working, not very well, but it kept our house warm over that time. So, and I have
[05:47]its checked every year, it doesn't really have any requirements for servicing, very, very simple.
[05:54]And the people who come and service it, they're really, they're absolutely excellent people.
[05:59]That was cost, well, in 2009, cost 12,000 pounds, so very expensive compared to gas boiler
[06:06]at the time. This is the crux of it, really, a graph of the efficiency and how the efficiency
[06:12]varies with the temperature of the water. Because it really is just a straight replacement for a gas
[06:19]boiler, in our case. So it connects into a hot water regulator system, which I've come on to,
[06:24]and the vertical bit is the efficiency, and it goes from four times to two times. So 400% efficiency,
[06:34]down to 200% efficiency, and this is the difference in temperature between hot water in the radiators,
[06:41]so that's what it's producing, and the temperature outside, because the temperature outside
[06:46]affects how it works. And what this means is on temperate days, when it might be seven degrees
[06:54]outside, and you want to heat your house to 20 degrees, and you might need water in the
[07:05]five, and you want to get water in the radiators up to 50 degrees, the efficiency drops. So the
[07:11]efficiency of it is changing rapidly all the time. It's not like a gas boiler, which is pretty
[07:16]constant. This is dynamic. It's moving around the whole time, depending on how cold it is outside,
[07:22]and how warm the radiator needs to be. So with this sort of thing in mind, you need to really
[07:29]try to get it to run as cool as it can all the time. So it's not like a gas boiler, which is
[07:34]blast water, hot water at 70, 75 degrees. Shouldn't really do this, but they do. This you need to
[07:41]always think about getting the temperature of the water down as low as possible, because the
[07:46]efficiency rockets you do that. And this I think this is why, you know, there's so much criticism
[07:51]in the press of people finding fault is because they haven't been installed with this in mind.
[07:56]The temperature of the water has to be as low as possible. And if you lower the temperature of the
[08:02]water and the radiators, the output of the radiators goes down more rapidly than the
[08:07]temperature that goes down. It's not linear, so it can go horribly wrong if you don't get it right.
[08:13]And there are two ways of addressing getting the temperature down. One is you improve the efficiency
[08:17]of the insulation in your house, which you might or might not be able to do. And that people say,
[08:22]you know, insulates your house. Well, okay, but you can put some loft insulation in, you can put
[08:27]some better windows in, some draft proofing around the doors. And then it starts to get difficult.
[08:39]insulation, but if you've got an old house with solid brick walls, it becomes very expensive.
[08:44]It's a Victorian house, you start to change the character of the house if you put it on the outside.
[08:48]There's just a heat pump. It's an easy fix, really, because what you do is you reduce your energy
[08:56]consumption three times. And there's no insulation, which you can do to a Victorian house, which will
[09:02]get anywhere near that. And if you did try it, it would cost you hundreds of thousands of pounds,
[09:08]you know, make sure you're loft insulation, fine, make sure you've got the windows draft proofing,
[09:12]maybe you can seal the floor. So you haven't got lots of drafty floors, and then stick a heat
[09:16]pump in. That's the best thing. There are settings in our machine, which you have to go in and set.
[09:22]I'm not showing the installer should do this is where you actually set the temperature in the
[09:27]radiator to be dependent on the temperature outside. So on really, really cold days, our
[09:33]radiators are about 50 degrees, maybe that's 49. And that's as hot as they go. And then as we come
[09:39]into this time, well, it's not on now. But you know, a few months ago, when it was maybe 10 degrees
[09:44]outside, I would have the temperature and the radiators about 2022. And what that does is
[09:49]because the pump's compressor now doesn't have to work so hard, because he's not having to produce
[09:53]very hot water. The electric demand drops and the efficiency rockets. And this is what we did, we
[10:01]put in bigger rate, we had steel radiators. And at the time we did this the best way, because
[10:07]everybody has a problem, they have pipes coming up to the floor, and what are you going to do to tear
[10:11]up the floor to put in bigger radiators. So we went for fitting radiators to the same pipes.
[10:17]And we went for cast aluminium radiators. So instead of having a steel panel radiator,
[10:23]we put in cast aluminium radiators, which is like this and this, which have much higher output.
[10:29]Basically, you need to be doing something like increasing, well, it depends on what you've got
[10:35]in the house, but you may be looking to increase the radiator outputs by 50 to 70%. Something of
[10:41]that order is likely to work. If you take a radiator, steel radiator, which is designed to
[10:48]work with water going in at 70 degrees, and then you then change that and put water in at 50 degrees,
[10:54]the output of the radiator will be hard. Now, since we did this, which was obviously 50 years ago,
[10:59]Stelran, who are the big manufacturers of steel radiators, now produce a radiator, which is
[11:06]designed to go onto the existing pipes and have twice the output. So they have actually solved
[11:12]this problem, but we didn't have that choice. So on our pipe, you can probably see just about,
[11:19]there's a sort of conch of botch pipe workers, the plumber, the pipes didn't quite line up with
[11:23]the size of the radiator, and the plumber had to do with the chicken was around.
[11:27]You wouldn't need to do that nowadays. So one of the things, if you can add insulation and reduce
[11:34]the heat loss of your house by doing that and draft quickly and get that improvement,
[11:38]sort of reducing airflow, sweeping heat out through the house, you might reduce, say,
[11:44]the heat demand of the house by 10%. If you could do that with a heat, if you do that with a gas
[11:49]boiler, you can just save 10%. If you do it with a heat pump, what it means is you can take the
[11:54]opportunity to lower the temperature in the radiators because you no longer need so much
[11:58]heat flowing into the house. You lower the temperature in the radiators and the efficiency
[12:03]goes up. So you probably save 15%. Our energy bills are energy consumption normalized. It's
[12:11]about 50 kilowatt hours of energy. This is everything we use. So I can't separate out
[12:17]televisions left on standby and all this sort of stuff, because we just can't be bothered to sort
[12:22]that out. It's about 50 kilowatt hours per square meter. And UK norms are 150 to 300 kilowatt
[12:31]hours per [square] meter, maybe more, depending...
TRANSCRIPT TO COME
Show Notes
Recorded with the Zoom H1n, stereo 48ksps, sitting on the desk at the front of the drama room near the speaker.
This final section of the talk Why heat pumps are necessary
turned into a long audience discussion, so too long for this format!
2024-07-28: my favourite Transcobble transcription tool had been broken for a while but Simon E just fixed it, and I am doing the transcript! Thanks!