Author Topic: What is the real story around heat pumps?  (Read 389405 times)

0 Members and 1 Guest are viewing this topic.

Online Zero999

  • Super Contributor
  • ***
  • Posts: 20363
  • Country: gb
  • 0999
Re: What is the real story around heat pumps?
« Reply #300 on: February 24, 2024, 12:49:17 pm »
I'm just not going to discuss net zero, propaganda and taxes. They're political and will just result in pages of arguing, with neither of us agreeing. I just don't support it. You clearly do. We'll just have to disagree and leave it at that.

That is simply a lie. You did discuss just that, as I quoted above. You just don't want to defend your position when challenged. If you didn't want to discuss it, you wouldn't have mentioned it in the first place.
Now it appears you're tying to provoke me, which will not work. I'm more than capable of defending my position.

You really need to pay attention. I didn't say you wouldn't be capable of defending your position. I said you didn't want to defend your position. Look at it, it's right there in the quote that you are responding to. Now, you aren't trying to tell me that you wrote "I'm just not going to discuss net zero, propaganda and taxes" because you wanted to tell me that you were intent on defending your position, are you?

Indeed I consider it to be fairly obvious.

I supposed as much. But you do notice how that is a pointless statement to make, right?

I just do not want to discuss the matter here any more.

Which might be true or not. But that doesn't change that it is dishonest to first throw out a statement that you know is controversial, to say the least, and then pretend that it's a claim that you don't want to talk about. Obviously, you would be willing to talk about it further if you were getting agreement. If it were in fact something that you didn't want to talk about, you wouldn't talk about it. But you obviously did talk about it. And you obviously weren't forced to, either.
I was not the one who first raised the issue of net zero, which is a controversial and political point and is against the rules of this forum.

I should have just reported it to the moderator, but made an error of judgement and responded to it.

It appears as though you just want to ague now. I have no intention of responding to your disingenuous posts.
 

Offline zilp

  • Frequent Contributor
  • **
  • Posts: 351
  • Country: de
Re: What is the real story around heat pumps?
« Reply #301 on: February 24, 2024, 12:50:52 pm »
I accept what might be the most economical solution for me, won't be the case for others. For the purposes of this thread, it doesn't matter why energy prices are what they are. It's outside the scope of this forum.

Except it totally does matter, because that is what can inform you about how prices will change in the future, and thus about what investment decisions now will pay off later.

This is like saying the reasons for the chip shortage are outside the scope of this forum, just because the causes of the shortage are not something traditionally covered by an EE curriculum. The reasons very much are relevant if you want to make an informed decision as to how to deal with the situation.
 

Offline zilp

  • Frequent Contributor
  • **
  • Posts: 351
  • Country: de
Re: What is the real story around heat pumps?
« Reply #302 on: February 24, 2024, 01:07:33 pm »
I was not the one who first raised the issue of net zero, which is a controversial and political point and is against the rules of this forum.

I should have just reported it to the moderator, but made an error of judgement and responded to it.

Erm ... you seriously think that just because someone on the planet thinks that something is controversial, therefore, it is against the rules? So, mentioning that the earth is a globe is against the rules because there are people who are convinced that it ain't so?! Saying that free energy machines don't work is against the rules because there are people who think that the knowledge is suppressed by dark cabals?!

I mean, using a "lefty" label to try and discredit someone's position is obviously a political maneuver that I would think is against the rules as it obviously can not contribute anything constructive to a discussion. Stating and explaining facts about reality ... no so much.

It appears as though you just want to ague now. I have no intention of responding to your disingenuous posts.

Yeah, sure. I totally believe you.
« Last Edit: February 24, 2024, 02:07:56 pm by zilp »
 

Online Siwastaja

  • Super Contributor
  • ***
  • Posts: 9339
  • Country: fi
Re: What is the real story around heat pumps?
« Reply #303 on: February 24, 2024, 02:07:18 pm »
I can buy a monobloc unit for my house for about £4,000.  That replaces the boiler and provides heat.  I would need a hot water tank

A tip, assuming you have either a boiler, or a separate storage tank with, with heat excharger for domestic how water. Plumbing: connect the monoblock to feed heated water into the boiler or storage tank, with the heatpump's own curve as optimized for house heating needs. You then get lukewarm "preheated" DHW out of the existing heat exchanger, so all you need it to install a small electric boiler "in series". Given that it only needs to heat the water from say 30..40degC to 60, not from 10 to 60, it can be a small one, one of those you would normally use for heating water for a single sink or in a small cabin. A 60-liter, 2kW boiler has served this purpose for me very well.

During summertime, especially if you use a lot of hot water, you are losing in COP. In winter, not so much, because the "incremental" or marginal COP above the house heating temperatures is close to 1.0 anyway, even if you use compressor.

This way, you don't need a motorized turnover valve or two large-ish storage tanks, and also get 100% duty cycle (minus defrosts of course) for house heating during the coldest of times. A simpler and lower cost system for retrofits, especially DIY. Has served me well. Annual loss of COP is probably not much but I haven't exactly calculated it. Professionals probably hate the idea, just like they hate monoblocks.
« Last Edit: February 24, 2024, 02:13:16 pm by Siwastaja »
 
The following users thanked this post: tom66

Offline zilp

  • Frequent Contributor
  • **
  • Posts: 351
  • Country: de
Re: What is the real story around heat pumps?
« Reply #304 on: February 24, 2024, 02:19:05 pm »
A tip, assuming you have either a boiler, or a separate storage tank with, with heat excharger for domestic how water. Plumbing: connect the monoblock to feed heated water into the boiler or storage tank, with the heatpump's own curve as optimized for house heating needs. You then get lukewarm "preheated" DHW out of the existing heat exchanger, so all you need it to install a small electric boiler "in series".

Beware of legionella, though, if you have a storage tank that is filled with DHW (as opposed to a storage tank with a low-volume heat exchanger for DHW).
 

Online Zero999

  • Super Contributor
  • ***
  • Posts: 20363
  • Country: gb
  • 0999
Re: What is the real story around heat pumps?
« Reply #305 on: February 24, 2024, 02:20:17 pm »
It appears as though a few people, including myself, have forgotten the forum rules, so I thought I'd post a quote to serve as a reminder.

Quote
This is an electronics forum, so try to stay on-topic. We understand that threads drift off-topic, but try not to start deliberately and grossly off-topic stuff.
There are a couple of pet topics that always get out of control on forums, namely, religion, politics, guns, war, conspiracy theories, and the latest Current Thing that's happening or being championed by the public. They are not welcome here. This includes inside signatures and profile bios. This isn't Twitter where you virtue signal to everyone with your flags, emoticons, and hashtags.
https://www.eevblog.com/forum/chat/forum-rules-please-read/

In light of this. I have gone back and edited some of my posts, removing references to politics, net zero being one of them. If anyone spots a post I've missed, please either report it to the moderator, or just drop me a private message. I have also reported several posts to the moderator. I strongly recommend others do the same.
 

Online Siwastaja

  • Super Contributor
  • ***
  • Posts: 9339
  • Country: fi
Re: What is the real story around heat pumps?
« Reply #306 on: February 24, 2024, 02:26:51 pm »
A tip, assuming you have either a boiler, or a separate storage tank with, with heat excharger for domestic how water. Plumbing: connect the monoblock to feed heated water into the boiler or storage tank, with the heatpump's own curve as optimized for house heating needs. You then get lukewarm "preheated" DHW out of the existing heat exchanger, so all you need it to install a small electric boiler "in series".

Beware of legionella, though, if you have a storage tank that is filled with DHW (as opposed to a storage tank with a low-volume heat exchanger for DHW).

That's why you set the electric boiler to maintain at least 60degC. Which is actually more idiot proof, given a simple mechanical thermostat, than a complex system with turnover valve and two tanks heated by a heatpump and controlled by the heatpump's (possibly buggy or hard to configure) control system.

Another plus side for my proposal is that you will have an independent back-up system for DHW, just smaller capacity, which Just Works without modifications even if the heatpump fails.
 

Offline zilp

  • Frequent Contributor
  • **
  • Posts: 351
  • Country: de
Re: What is the real story around heat pumps?
« Reply #307 on: February 24, 2024, 03:27:53 pm »
Beware of legionella, though, if you have a storage tank that is filled with DHW (as opposed to a storage tank with a low-volume heat exchanger for DHW).

That's why you set the electric boiler to maintain at least 60degC. Which is actually more idiot proof, given a simple mechanical thermostat, than a complex system with turnover valve and two tanks heated by a heatpump and controlled by the heatpump's (possibly buggy or hard to configure) control system.

I'm not sure that that would be sufficient with a DHW storage tank!? AIUI, the problems is that the large volume (a) means that the concentration of bacteria never gets reduced much if they ever are established because use of hot water only dilutes things a bit while the growth is exponential and (b) sediments will settle in the tank, which adds additional protection for the bacteria from being cleaned out from the tank. At the same time, killing a high-ish concentration of bacteria down to a low-risk level would require heating to 60°C for many minutes, maybe up to 30, which a simple electric boiler at the output can't do. To kill them in seconds would require 70°C or more. Or you would have to occasionally heat up the tank to 60°C using the boiler somehow.
 

Online Siwastaja

  • Super Contributor
  • ***
  • Posts: 9339
  • Country: fi
Re: What is the real story around heat pumps?
« Reply #308 on: February 24, 2024, 03:39:56 pm »
I'm not sure that that would be sufficient with a DHW storage tank!? AIUI, the problems is that the large volume (a) means that the concentration of bacteria never gets reduced much if they ever are established because use of hot water only dilutes things a bit while the growth is exponential and (b) sediments will settle in the tank, which adds additional protection for the bacteria from being cleaned out from the tank. At the same time, killing a high-ish concentration of bacteria down to a low-risk level would require heating to 60°C for many minutes, maybe up to 30, which a simple electric boiler at the output can't do. To kill them in seconds would require 70°C or more. Or you would have to occasionally heat up the tank to 60°C using the boiler somehow.

No need to overthink. Just set to 60degC. Water is always held at 60degC (plus minus hysteresis of thermostat, and small excursions during heavy water use, but that's only for a short time). This is OK at least per legislation here. Maybe some other country requires 55 or 65degC. Set it to +70 with a further small decrease in total COP, if worried.

And this is definitely safer than than the "official" way of doing it offered by heatpumps, namely heatpump maintaining 50-55degC in DHW tank, which is a tad too low, with a 60-65degC "legionella" program running once a week. The risk is this program being too short or failing somehow. Even then, I'm not aware of any actual problems.

You probably did not understand what I suggested from my description in the first place, and being lazy I'm not going to try to draw a picture of it right now so just reread carefully my (possibly poor) explanation. Single storage for house heating -> pre-heated lukewarm DHW through existing heat exchanger -> small electric boiler in series to final temperature. This small boiler sits at high temperature all the time.
« Last Edit: February 24, 2024, 03:41:53 pm by Siwastaja »
 

Offline zilp

  • Frequent Contributor
  • **
  • Posts: 351
  • Country: de
Re: What is the real story around heat pumps?
« Reply #309 on: February 24, 2024, 04:24:16 pm »
There is no such thing as a delicate balance.

You are aware that you are in disagreement with about everyone who does research in that area professionally, right?
Citation needed... Maybe you should actually do some research into the subject like I did for over 25 years already.

https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM.pdf , search for 'tipping'.

If you start looking carefully you'll notice that a lot of data is being filled in by assumptions and thus the 'conclusion' is only an assumption. Trying to model something erratic as weather / climate is next to impossible so anyone claiming to have an absolute truth in that area is leaving out a lot of details which may even prove that person wrong. There are some long term effets (like recurring CO2 peaks, sun cycles, cold / hot periods centuries ago, etc, etc) which are not explained by models used for global warming. In the end global warming predictions are a line fitted onto the temperatures from the last 100 years with the assumption that CO2 levels are the major factor driving the temperature up.

You do realize that you have no idea how climate models actually work, right? The idea that somehow it is all based on weather data of the last 100 years is just ... wild.

Also ... why would you possibly expect a climate model of earth to explain sun cycles?! Sun cycles are obviously an input to climate models, not something that they try to explain!?

And also, who has ever claimed absolute truth? Are you saying that we should ignore risks unless we are absolutely certain that they will be realized?

Oh, and also ... now, what is it, is the climate chaotic, or is there not a delicate balance? You can't have it both ways. Either there are forking points where minor perturbations in inputs are amplified into huge effects or there aren't.

Oh, and ... why are you still mentioning the weather? How is chaotic behaviour at the micro scale relevant for the macro scale of climate?

Other than that, your objections really are just too vague to be useful.

IOW there is a good reason that people are getting fed up with fear mongering and start to vote for right wing politicians which want to continue burning fossil fuels.

Which is all based on the baseless assumption that it is fear mongering. So, you are just assuming your conclusion. If it is a real danger, then politicians acting to mitigate the risk are not fear mongering, and just claiming that it is doesn't create a good reason to be fed up with what they are doing.

In turn this circles back that renewable energy sources and reduction of energy usage needs to be made cheap enough for the masses.

Which still is a useless statement if you can't explain how that could be done.
 

Offline zilp

  • Frequent Contributor
  • **
  • Posts: 351
  • Country: de
Re: What is the real story around heat pumps?
« Reply #310 on: February 24, 2024, 04:39:14 pm »
And this is definitely safer than than the "official" way of doing it offered by heatpumps, namely heatpump maintaining 50-55degC in DHW tank, which is a tad too low, with a 60-65degC "legionella" program running once a week. The risk is this program being too short or failing somehow. Even then, I'm not aware of any actual problems.

Well, the preferred way is to not have a DHW tank at all, but only a storage tank with a heat exchanger for DHW, so that there is no significant volume of DHW at problematic temperatures, and what is there is cleaned out completely whenever you use hot water.

You probably did not understand what I suggested from my description in the first place, and being lazy I'm not going to try to draw a picture of it right now so just reread carefully my (possibly poor) explanation. Single storage for house heating -> pre-heated lukewarm DHW through existing heat exchanger -> small electric boiler in series to final temperature. This small boiler sits at high temperature all the time.

I am still not entirely sure what exactly you mean, but also, my response wasn't necessarily relevant to your specific setup, just a warning of something to consider.

If you mean a storage tank filled with non-DHW that is kept warm by the heat pump and a DHW heat exchanger in that tank (I think that that is what you are describing?), then that should be fine because there is no significant (dead) volume of DHW kept at problematic temperatures for a long time, so, with regular use, you shouldn't ever get any persistent high legionella concentrations.

The problem arises if you have a storage tank with DHW in it, which you could possibly keep at 30 to 40°C with the house heating heat pump as well, but then I would think that an electric boiler at the output heating the water to 60°C would not be sufficient to kill the legionella if they were to get established at high concentrations in the tank.
 

Offline NiHaoMike

  • Super Contributor
  • ***
  • Posts: 9323
  • Country: us
  • "Don't turn it on - Take it apart!"
    • Facebook Page
Re: What is the real story around heat pumps?
« Reply #311 on: February 24, 2024, 04:58:45 pm »
And this is definitely safer than than the "official" way of doing it offered by heatpumps, namely heatpump maintaining 50-55degC in DHW tank, which is a tad too low, with a 60-65degC "legionella" program running once a week. The risk is this program being too short or failing somehow. Even then, I'm not aware of any actual problems.
In the US, the solution (at least for the majority on city water) is the water has chlorine or chloramine added. The recommended hot water temperature is 120F as the risk of burns increases dramatically beyond that.

Another solution would be to have a UVC light inside the tank. My guess as to why that's not common is simply because there's no need for it with city water.
Cryptocurrency has taught me to love math and at the same time be baffled by it.

Cryptocurrency lesson 0: Altcoins and Bitcoin are not the same thing.
 

Online Siwastaja

  • Super Contributor
  • ***
  • Posts: 9339
  • Country: fi
Re: What is the real story around heat pumps?
« Reply #312 on: February 24, 2024, 06:35:53 pm »
Well, the preferred way is to not have a DHW tank at all

DHW tanks are super popular here, during the era when electric radiator heated houses (with no hydronic distribution) were built starting from 1980's (after the oil crisis). Most are made of stainless steel and it was really popular to automagically time them to use nightime tariffs for which 300 liters was a usual volume and 3kW the usual power. Smaller volumes for continuous operation. No one here considers them problematic at all. They are clean from biological growth because of the temperature, and last easily for 30-40 years. But clearly different solutions are popular in different countries. The small ones cost just a few hundred €. It's easy to put one in series to get to high enough water temperature if you have an "easy" (and high COP) source of preheated but not warm enough DHW, which is often the case in monoblock air-to-water retrofits in existing systems which did earlier use higher temperature in a tank with heat exchanger as explained by you.
« Last Edit: February 24, 2024, 06:38:21 pm by Siwastaja »
 

Offline nctnico

  • Super Contributor
  • ***
  • Posts: 28429
  • Country: nl
    • NCT Developments
Re: What is the real story around heat pumps?
« Reply #313 on: February 24, 2024, 06:56:23 pm »
And this is definitely safer than than the "official" way of doing it offered by heatpumps, namely heatpump maintaining 50-55degC in DHW tank, which is a tad too low, with a 60-65degC "legionella" program running once a week. The risk is this program being too short or failing somehow. Even then, I'm not aware of any actual problems.
In the US, the solution (at least for the majority on city water) is the water has chlorine or chloramine added. The recommended hot water temperature is 120F as the risk of burns increases dramatically beyond that.
That is too low to protect against legionella. And there can be other parasites in the water as well which are chlorine resistant AND can make you quite sick. So I'd keep the water temperature high. However, I can highly recommend getting a thermostatic tap for shower(s) and bathroom sink(s). They are limited to a safe temperature. And it saves quite a bit of water because it reaches the setpoint temperature quicker compared to manual mixing.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online Siwastaja

  • Super Contributor
  • ***
  • Posts: 9339
  • Country: fi
Re: What is the real story around heat pumps?
« Reply #314 on: February 24, 2024, 07:01:27 pm »
That is too low to protect against legionella.

This underlines how cultural differences affect engineering. In the land of freedom and lawsuits, you use chemical warfare against the threat, but you want to avoid hot water being hot because someone could get burns and sue. I'm sure it works there. Here we just try to carefully adjust our mixing valves to 60degC which is just enough to kill legionella and just low enough to at least avoid serious burns even though someone who is very careless could get minor burns. And we think it's parent's job to keep children away from dangerous stuff.
« Last Edit: February 24, 2024, 07:05:15 pm by Siwastaja »
 

Offline zilp

  • Frequent Contributor
  • **
  • Posts: 351
  • Country: de
Re: What is the real story around heat pumps?
« Reply #315 on: February 24, 2024, 07:10:39 pm »
But clearly different solutions are popular in different countries. The small ones cost just a few hundred €. It's easy to put one in series to get to high enough water temperature if you have an "easy" (and high COP) source of preheated but not warm enough DHW, which is often the case in monoblock air-to-water retrofits in existing systems which did earlier use higher temperature in a tank with heat exchanger as explained by you.

Oh, you are talking about a boiler in a tank? I thought you meant just a (flow-through type) boiler with minimal water volume. That should help, too, I guess.

Well, there are man ways to solve this, the important point is, whatever you do, pay attention to legionella!
 

Offline JohanH

  • Frequent Contributor
  • **
  • Posts: 669
  • Country: fi
Re: What is the real story around heat pumps?
« Reply #316 on: February 24, 2024, 07:15:07 pm »
That is too low to protect against legionella. And there can be other parasites in the water as well which are chlorine resistant AND can make you quite sick. So I'd keep the water temperature high. However, I can highly recommend getting a thermostatic tap for shower(s) and bathroom sink(s). They are limited to a safe temperature. And it saves quite a bit of water because it reaches the setpoint temperature quicker compared to manual mixing.

I guess it's very different in different countries. We are spoiled with very clean ground water in all of Finland. In our town it's taken straight from the ground and you can drink it from the tap as is. Everyone does! As for the hot water, in our house it's heated by the ground source heatpump to about 50 degrees C (in a 180 l tank) and twice a month it's heated to 60 C. There's a thermostat after the heat pump that mixes it down somewhat. Everyone that I know have thermostatic taps in their shower. I considered also putting a small electrical DHW tank in series, but it isn't needed for our hot water consumption (I know many does this over here). It's exactly as Siwastaja explained, they are used to "top up" the hot water and to get more capacity. I have never heard of any legionella or any other problem due to hot water over here, so I guess the legislation is enough.
 

Online Siwastaja

  • Super Contributor
  • ***
  • Posts: 9339
  • Country: fi
Re: What is the real story around heat pumps?
« Reply #317 on: February 24, 2024, 07:27:09 pm »
in our house it's heated by the ground source heatpump to about 50 degrees C (in a 180 l tank) and twice a month it's heated to 60 C.

This is what everyone "by default" does with heatpumps (ground source or air-water), because it's as implemented by the pump manufacturers, and I know it practically does not cause problems, but it strictly is illegal; the legal minimum continuous temperature is 55degC (of course very short excursions would be allowed, but "all the time except every two weeks" doesn't cut it). Specifically, 60degC is not enough for a "kill" program unless it's very long.

The legal range is here in 6§: https://www.finlex.fi/fi/laki/alkup/2017/20171047 : 55 to 65 degC. It's quite strict and I'm sure 80% of households doesn't meet these limits, yet legionella outbreaks are still very rare, because the actual high-risk region is more like +30 - +45 degC.

Low side of that range needs to be exceeded by the storage tank itself; high side can be shunted down by thermostatic mixing valve as usual.
« Last Edit: February 24, 2024, 07:29:07 pm by Siwastaja »
 
The following users thanked this post: JohanH

Offline nctnico

  • Super Contributor
  • ***
  • Posts: 28429
  • Country: nl
    • NCT Developments
Re: What is the real story around heat pumps?
« Reply #318 on: February 24, 2024, 07:28:51 pm »
That is too low to protect against legionella. And there can be other parasites in the water as well which are chlorine resistant AND can make you quite sick. So I'd keep the water temperature high. However, I can highly recommend getting a thermostatic tap for shower(s) and bathroom sink(s). They are limited to a safe temperature. And it saves quite a bit of water because it reaches the setpoint temperature quicker compared to manual mixing.
I guess it's very different in different countries. We are spoiled with very clean ground water in all of Finland. In our town it's taken straight from the ground and you can drink it from the tap as is.
The same goes for the NL. In most cities the water from the tap is cleaner compared to bottled water. Nevertheless, ground and surface water does contain legionella and it could grow given the right circumstances. Legislation is greatly depending on what kind fo serious outbreak has occured or not. In the NL (around)15 people died in a single incident due to a legionella outbreak so more legislation was put into place.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online Siwastaja

  • Super Contributor
  • ***
  • Posts: 9339
  • Country: fi
Re: What is the real story around heat pumps?
« Reply #319 on: February 24, 2024, 07:45:41 pm »
In the NL (around)15 people died in a single incident due to a legionella outbreak so more legislation was put into place.

You mean this one:
https://en.wikipedia.org/wiki/1999_Bovenkarspel_legionellosis_outbreak

Typical legionella cases seem to be:
* Hot tubs that are kept at around 37degC for prolonged times
* Air conditioner systems that stay inactive (still holding large amounts of condensed water at the evaporator) in very warm conditions, then are suddenly turned on
* Evaporative cooling towers people come in close contact with
* Rarely used shower heads in warm bathrooms
* Rarely used pipe stubs in large DHW systems

Household cases where someone only heat their water to 50degC instead of maybe 55 - I don't believe there are cases at all.

Serious cases all share long-term exposure at temperatures around 30-40 degC (optimum for growth) and then something that makes fine mist out of this water so that people breath it in.
« Last Edit: February 24, 2024, 07:48:35 pm by Siwastaja »
 
The following users thanked this post: nctnico

Online tom66

  • Super Contributor
  • ***
  • Posts: 7336
  • Country: gb
  • Electronics Hobbyist & FPGA/Embedded Systems EE
Re: What is the real story around heat pumps?
« Reply #320 on: February 24, 2024, 08:07:52 pm »
Can legionella even grow in a hot water tank? The majority of modern hot water tanks, at least in the UK, are unvented with external expansion vessels, as this tends to be more efficient. Since the vessel is under pressure, essentially the entire volume is full of water. Legionella is not an anaerobic bacterium, so the chances of the bacteria even having a location in which to grow is questionable.  I suppose it would be a concern for a vented system, but in the UK those haven't been installed for 20+ years.
 

Offline pcprogrammerTopic starter

  • Super Contributor
  • ***
  • Posts: 4670
  • Country: nl
Re: What is the real story around heat pumps?
« Reply #321 on: February 24, 2024, 08:24:16 pm »
The whole idea of these systems to pay for themselves is kind of bullshit. Sure it can reduce on your energy bill, but it will still cost money. Depending on the type of system and the cost to install it can take a long time before any savings start to come.

Remember that expensive systems such as quoted for you are a kind of specialty of wealthy societies and wealthy households. Energy solutions are being sold exceeding their true value, because there is market for that and people still buy. My air-to-water heat pump installation was less than 4000EUR all parts included, although I did the install work myself but it would have been less than 1000EUR for work if I just paid for hourly rates for electrician and plumber; and the end result is way better than how a typical 15000EUR complete one size fits all solution would have been.

Typical cost for air-to-water retrofit was around 8000-9000 EUR here but nearly doubled to 14-15000 EUR almost overnight after a 4000EUR subsidy come into place. The market does not reflect actual costs, and any subsidies further twist the market. Enough people are willing to pay outrageous prices when they feel good about it.

In Japan air-to-air heatpump costs something like 500EUR installed so one can easily afford one per each room. They do pay back for themselves, that's literally why they were developed in 1980's in the first place, to save cost of fossil fuels.

Even when I would get a cheap monoblock heat pump and do the work myself and spend say the 4000 euro you mentioned yours costed, it would still take a very long time to see a so called "return on investment" or reach a break even point.

What I pay now for my heating is 24m3 of fire wood at 55 euro the m3 is 1320 euro.
On average loss of interest on 4000 euro in a savings account lets say 80 euro. (At the moment we get more then 2% here in France, but it will vary)
Needed heat energy 16500KWh at SCOP 3.5 is ~4714KWh at an average electricity price of 20 euro cents comes to 942,8 euro.

So saving comes down to 1320 - 942,8 - 80 = 297,2 euro per year so comes down to about 13,5 years. At that time it might be needed to buy and install a new heat pump. If not you will have to save up the money you save and it will take another 10 years, with interest on interest, or so to get the initial 4000 euro back in the bank.

This is not taking into account the cost of owner ship like maintenance or replacing defective parts if needed, nor is it taking into account the rise in electricity price that comes round once in a while. The latter would also effect the price of fire wood, so not really needed to adjust for.

And that is why I said that living costs money.

It might be different for others who have much higher heating costs with their current system, but still you will never really get your investment back.

To me there is a distinction between saving money and making money. With PV solar panels it might be a different story when you harvest way more energy than you consume and can actually sell the remainder to the energy company. But then still you have to take cost of owner ship into account.

Online Someone

  • Super Contributor
  • ***
  • Posts: 5156
  • Country: au
    • send complaints here
Re: What is the real story around heat pumps?
« Reply #322 on: February 24, 2024, 08:56:06 pm »
All it needs is people plainly stating the reason why they think their position, instead of non specific unarguable generalisations.

Most of this thread is UK people dodging the fact that their energy costs are abnormal, while making all sorts of big claims about the rest of the world. Obnoxious colonialism vibes.
And from my position, I see this thread as a load of Europeans lecturing us Brits telling us what to do.
Quite the reverse from my perspective. You (and others) are jumping onto worldwide generalisations (as applicable to the OP) and arguing (without stating clearly that it only applies to your local situation) that other assessments/positions/choices are wrong.

...and coming back time and time again without citations, references, or bothering to make basic factual checks on your posts. Oh yeah, thats obnoxious.

zilp is putting up some pretty convincing rational arguments for heat pumps even in the UK. Which agree with my simple statements earlier:
Given the uses of gas a realistic price ratio is heading somewhere closer to 1:2, many countries are already there and betting on cheap gas being either:
a) available in other locations, or
b) continuing the large price ratio into the future
are both unrealistic.
If gas is so cheap in your market that heat pumps aren't economic for domestic heating, then why isn't someone bottling it up and selling it off to other countries for profit? Why aren't gas power stations running at high utilisation and profiting? Other countries are way ahead on the gas market changing, it's unrealistic to think the UK (or any other country) can maintain such large price ratios on an ongoing basis.
 

Online tom66

  • Super Contributor
  • ***
  • Posts: 7336
  • Country: gb
  • Electronics Hobbyist & FPGA/Embedded Systems EE
Re: What is the real story around heat pumps?
« Reply #323 on: February 24, 2024, 08:56:22 pm »
Even when I would get a cheap monoblock heat pump and do the work myself and spend say the 4000 euro you mentioned yours costed, it would still take a very long time to see a so called "return on investment" or reach a break even point. [...]

True if you just consider the outright cost of the heat pump, BUT, if you instead install the heat pump when the existing heating system needs refurbishment or replacement (do you have a wood/biomass boiler heating hot water for the house for instance?)  then it makes a lot more sense economically since you are just paying the "premium" to get one.  Say in my case, a replacement gas boiler costs around £2,500 to have fitted professionally.  If I could get a heatpump fitted for about £5,000, then I only have to make up £2,500 in heating costs over a decade, ignoring for now the time value of money.  That seems just about feasible - £250 per year in savings (I spend roughly £1,200 a year in gas) or about 20%.  If combined with solar/battery and load shifting (not heating the house at peak times and using a tariff that gives me a discount for doing so) then it probably ends up more cost effective. 

I can get an install for under £5,000 if I use the grant scheme, but the real cost to the taxpayer is another £7,500.  Such a system would have a 7 year warranty as long as it is serviced, which is good but not amazing, though better than most gas boilers which tend to have only 2-3 year warranty at best as they are so commoditised now.  What worries me is between year 7 - say the end of the life of the system at year 12 if indeed it has failed by then.  Do I go for another heat pump?  Will costs have fallen by then to be similar to gas boilers?  Or will it instead cost £5,000 to have the heat pump unit changed?  If that is the case, the economics don't work out against gas.

 

Online Someone

  • Super Contributor
  • ***
  • Posts: 5156
  • Country: au
    • send complaints here
Re: What is the real story around heat pumps?
« Reply #324 on: February 24, 2024, 08:59:18 pm »
Can legionella even grow in a hot water tank? The majority of modern hot water tanks, at least in the UK, are unvented with external expansion vessels, as this tends to be more efficient. Since the vessel is under pressure, essentially the entire volume is full of water. Legionella is not an anaerobic bacterium, so the chances of the bacteria even having a location in which to grow is questionable.
Still a problem and while deoxygenation is theoretically possible I've not heard of it being commercially used:
https://doi.org/10.3390/w14172644
 
The following users thanked this post: tom66


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf