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Domestic Heat Pumps

Discussion in 'off topic' started by Vinny, Jun 9, 2021.

  1. Somafunk

    Somafunk pfm Member

    The housing partnership that took over dumfries & galloway council housing stock received a green initiative grant to remove coal/open fires from the houses that were not on mains gas, aka greenwashing. They claimed it would be cheaper to run and provide sustainable heating and hot water solutions. Utter ****ing bullshit dressed up as "look at how green and environmental our housing stock is"..............I'm convinced someone on the board of DGHP got backhanders to ensure the refit went ahead but im not allowed to repeat this otherwise ill be taken to court....a mate used to be in charge of housing repairs so im 100% convinced of what I was told.
     
  2. SteveG

    SteveG pfm Member

    When I'm on Islay I usually stay in Port Charlotte and noticed a lot of the houses there have been fitted with the heat-pumps and I assume that must have been down to one of the government initiatives as I didn't initially think they would have been the best of candidates for that, as most of the houses were from 1840 or so. They're right beside the sea though so I don't think they'll often be dealing with very low temperatures - or at least not for long. It looks like the housing association there is also going down the heat-pump route for their properties as well. I also found a report that looks at Islay more generally and they're looking at stuff like boreholes and even a water source heat-pump out into one of the sea-loch (that's for the Youth Hostel in Port Charlotte and the estimate is that it's going to cost £129K). The document for that is an interesting read and can be found at https://irp-cdn.multiscreensite.com...asibility Study GSHP WSHP - Public report.pdf
     
  3. Vinny

    Vinny pfm Member

    Interesting numbers here - Heat pump - Wikipedia

    Domestic heat pumps are operating with relative efficiencies of around 2-3, so they provide 2-3 times the energy (heat) as they consume, so effectively cutting the price of the electricity to run them, to a half to a third.
     
  4. IanW

    IanW pfm Member

    Thanks.

    That is shocking to hear.

    Completely inappropriate use of such technology.
     
  5. Vinny

    Vinny pfm Member

    Is it?

    It sounds more like the very predictable headless chicken civil servants and politicians, all with arts, humanities and suchlike degrees, running around and seeking no scientific/professional advice.

    Situation normal.
     
  6. PsB

    PsB Citizen of Nowhere™

    I don't understand this idea that you need to have a super-insulated building to be able to use a heat pump. These are two different discussions: the heat loss of the building, and how to make up that heat loss. Heat pumps are an efficient solution to the second part of the equation, as described by Vinny above you get 3 kW of heat for every kW of electricity you put in (with some variation depending on outside ambient temperature in the case of air-side HPs).The other benefit of HPs is you can reverse them in summer...

    If the building is old and draughty, you just need a bigger heat pump, just as you need a bigger gas boiler. Improving the insulation of the building just reduces the size of heat source needed.

    Am I missing something?
     
  7. mikemusic

    mikemusic pfm Member

    Cost effective with usually a short payback for super insulation, even more with draught proofing
    Free money sooner or later
     
  8. IanW

    IanW pfm Member

    Well, as stated it is to me.

    I have been interested in such technologies for a long time and have focused on the technical aspects and how they could be used.

    This is the first time I have come across a green washing use of heat pumps. But then again I have not looked for such articles and by the sounds of it, you are expecting misuse to be common and you may well be right for the reasons that you have given.
     
  9. Vinny

    Vinny pfm Member

    You'd need a huge heat pump to compensate for high losses. To get a huge heat pump to dump enough energy into a house with high losses, you would need whole-wall radiators or under-floor, behind-wall and above-ceiling heating. It is because the temperature of the water that can be generated is low - 50C maximum.

    You could run a heat pump off the first - using the 40-50C water as the heat source, but overall efficiency would be no better than running electric central heating.
     
  10. Vinny

    Vinny pfm Member

    The fact that the heating industry beleives that less than half the number of homes are suitable, compared to "official statistics", says quite a bit to me.
     
  11. PsB

    PsB Citizen of Nowhere™

    I can PM you a picture of a 50-100kW heat pump that is 2m^3. So huge, relative to what? I think you are making a lot of assumptions here, and in particular assumptions about heat pump technology, refrigerants used, efficiency of underfloor heating, etc. (There are huge ones, too, several MW, but this is about domestic HPs.)
    A 20kW heating need is a 20KW heating need, regardless of what you use to cover it. It will take up more space and cost more than a 10kW heat source.
     
  12. Vinny

    Vinny pfm Member

    Not relevant - the maximum water/transfer liquid temperature achievable is around 50C.

    To heat a drafty/lossy house with that would need internal heat-exchangers of a size that are TOTALLY unacceptable.

    Very simple physics.
     
  13. IanW

    IanW pfm Member

    Yes you can (and if it were financially viable the solution for @Somafunk would have worked), but...

    The costs install such a system are currently much greater than a gas boiler. The greater the energy requirement the greater the installation cost, although it should be a non linear increase.

    As most houses will use radiators, they will most likely need to install underfloor heating and a lot of insulation underneath it, or else you will be losing a lot of energy to heat the earth beneath the house.

    A builder that I know has been asked to get quotes for installing an ASHP system for a large new build (6 bed) and has been quoted >£60k after a lot of haggling. His company has installed them before and says that this is typical at the moment for that size of house. I do not know what it would cost for for an older house that has a poor energy rating and requiring a retrofit.

    At the other end of the scale a friend of mine who has installed 5 systems has only done it in very small houses (2 up and 2 down) and was able to purchase the units for £2 to £3k, and use his own time and experience to do all the work around the unit where the costs usually mount up very quickly. Instead of underfloor he put the pipes into the wall and so made one wall a radiator as he likes to experiment with these things. This was done after sealing the building, adding a heat recovery and ventilation system and adding a lot of insulation.

    So in summary, I am not saying that you can't do what you have suggested, just that it is not currently financially viable to do so and may be impractical to do in many buildings.
     
  14. IanW

    IanW pfm Member

    It does to me as well.

    After a quick web search I can see the spin (and incorrect statements) that some companies that install such systems are putting out there.
     
  15. PsB

    PsB Citizen of Nowhere™

    No, it depends on the refrigerant used. 70C to 80C reachable.
    And in-floor heating provides a large enough surface (I have this at home) to heat a whole house even with 40C water.
     
  16. Vinny

    Vinny pfm Member

    Theory is one thing, real life another. Not so on either count - read up on the details - LOADS on the www.
     
  17. PsB

    PsB Citizen of Nowhere™

    Thanks for the condescension: by the looks of it, I probably know more about heat pumps than you do (admittedly a low bar, judging from this exchange).
     
  18. Somafunk

    Somafunk pfm Member

    It’s perfectly acceptable to personally hold such a notion and express it on a web forum but don’t be surprised or spit the dummy when more knowledgeable people try and explain why you need a very well insulated house to benefit from the fitting of an air source heat pump.
     
  19. PsB

    PsB Citizen of Nowhere™

    Not spitting the dummy. I'm perfectly happy to defer to technically more knowledgeable people, on any subject, but so far this thread has not produced too many cogent responses to my simple question.
    Now, if the formulation had been that you need a well-insulated house to benefit from tiny air-side heat pumps running HFC or HFO refrigerant and producing a few kW, or that the technology exists but is still more expensive, we would not be having this argument. But the claim made by "experts" was that you can't get water temperatures >50C from heat pumps or retrofit them to existing buildings, laws of physics etc. This is incorrect. Technology is advancing rapidly in this area, and what was true 5 or 10 years ago is not necessarily true any more.
     
  20. Richard Lines

    Richard Lines pfm Member

    Good Evening All,

    I am not an engineering person but I am a person who has had a very strong interest in matters 'green' for some time and who lives in a house that has had solar PV since 2008, UFH replacing radiators since 2009, a GSHP and solar hot water since 2016, battery storage since 2019 and an EV since 2018 I feel I have a reasonable experience in this area.

    We live in an 1859 built stone farmhouse and the GSHP works fine, generally speaking the maximum water temperature out to the the combination UFH/ radiators is 42°C with an outside temperature down to -10°C. Hot water can be heated to 58°C.

    The property has an EPC rating 'A' which is a shed load better than most of the nearby properties (mostly 'D' according to recent sales particulars).

    The other side of the coin is that this hasn't been achieved at zero cost - BUT it is possible.

    Regards

    Richard
     
    PsB, cctaylor and foxwelljsly like this.

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