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Heating and cooling: greenheat and energie - what's the catch?

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1 to 13 of 13

  1.  
    • CommentAuthorglerwill
    • CommentTimeApr 20th 2012
     
    Hi,
    I saw this system at the buildstore exhibition http://www.greenheat-renewables.co.uk/pdfs/Greenheat%20Thermodynamic%20Heating%20Insert.pdf

    It looked attractive - solar hot water year round and heating for the house, but the brochure is full of terms like 'special liquid'. Is it an air source heat pump? What's the efficiency? What about dumping excess heat?

    Tried to ask questions of the person at the show, but did not really get anything useful from him...


    rgds

    Graham
    • CommentAuthorSeret
    • CommentTimeApr 20th 2012
     
    Yep, sounds like a heat pump, they mention it having a compressor and refrigerant. Lots of waffle on that site.
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 20th 2012 edited
     
    Think we covered it somewhere else. Worth looking to see if it has any accreditation.
    Having said that, a heat pump needs to collect heat from somewhere, air or water is usual. They way they do this is to cool a liquid, usually water and anti-freeze to below 0°C, but can be lower, say -20°C (that could be the special liquid), pass it though something so that it warms up, usually a long plastic pipe in the case of a GSHP or a fan assisted radiator in the case of an ASHP. There is no reason why it cannot use solar thermal panels, easier to fit than a GSHP and no noisy fan like an ASHP. As that fluid warms a bit, it is put back into the 'fridge' and cooled again. It is the excess waste heat that is used to heat water. What would be nice to see is a set of performance figures at different external temperatures rather than this impressive looking table that says very little.
    The water heating claims are impressive, what I could do with 5 tonnes of water at 55°C, just the water alone would cost me 30 quid an hour :devil:
      Heat Panels.jpg
    • CommentAuthorglerwill
    • CommentTimeApr 20th 2012
     
    Thanks for the useful comments. I did see quite a strong frost on the exit pipe. I have asked some of the questions of the supplier that you mentioned.

    I'm guessing that it gets heat from the sun when shining - after all it looks like a black aluminium radiator panel! and from the heat pump when the sun's not shining..... but some clarity would be nice...

    pluses for me

    +no noise like from an ASHP.
    +hot water and heating, at least for a well insulated house.
    +no glass on roof - looks lightweight - looks easy to make 'roof integrated' with a standing seam metal roof.

    -installation cost was mentioned at about 9K for a 'average' house - a supply only option would be nice.
    - no explanation of cost to run (electricity/ coefficient of efficiency).
    - no explanation of a means of dumping excess of heat (swimming pool mentioned?)
    - is the need for a backup heat source eliminated?

    Despite that, it looks good to me, for a well insulated house with maybe MHVR as well....

    rgds

    Graham
  5.  
    Hi,

    Yes been covered before see the thread "Thermodynamic solar panels" (cant do a link) covers these. 2nd page has a post from the Ireland distributor with details etc.

    Cheers
    Mike up North
  6.  
    http://www.energie.pt/

    There is the manufacturers website, there is also another manufacturer of these in Spain or Portugal but the name escapes me.

    Yes it is a heat pump, but the collector is in the form of a roof mounted panel rather than a ground loop.

    I looked at these last year but I have still been unable to get any independent verification of the energy consumption of such a unit.

    If you search the net you will find lots of threads discussing these panels, but the only user feedback that didn't appear to come from someone shilling the system was invariably negative in terms of the running costs.

    I would be very reluctant to install such a system without some independent verification.

    Here is a reference from another forum to a system that claims to have been independently monitored by Climacheck for 3 years.

    http://www.diynot.com/forums/viewtopic.php?p=1818965#1818965

    However my attempts to obtain this data have so far proved fruitless, but perhaps someone else might have better luck?
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 20th 2012
     
    Posted By: glerwillfor a well insulated house with maybe MHVR as well....

    A 1kW fan heater would work well in that situation, cost about a tenner with a running cost of a fiver a day or less.
    CO2 emission around 12 kg/day if left on all day.
    So assume that the heating season is 4 months (120 days), heating time is 16h a day, that is 350 quids a year, CO2 about a tonne.

    If it costs 9k for an installation, that is a payback, at current prices, of 26 years.
    Keep that at the back of your mind as that is the most expensive method of heating a house.
  8.  
    @ST and what about his DHW costs?

    Just did some better research and have sent an email to the guy who claims to have 3-5years independent test data on the performance of these panels.

    If I get a reply I will post what details I can.
    • CommentAuthorCWatters
    • CommentTimeApr 20th 2012 edited
     
    The big question for me is what happens on a cold windless winters day when the panel is covered in snow and the heat pump is trying to make the panel colder still?

    What's the COP on a cold cloudy windless day?
  10.  
    Posted By: CWattersThe big question for me is what happens on a cold windless winters day when the panel is covered in snow and the heat pump is trying to make the panel colder still?

    What's the COP on a cold cloudy windless day?


    My understanding is there is a direct electric coil which takes over (or supplements) when the HP can't produce to the target temperature.
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 20th 2012 edited
     
    Posted By: CWatterspanel is covered in snow

    I would think that the COP goes down, snow is a good insulator. There is a safety aspect here though when it warms up and a foot thick 5 by 3, 150 kg lump of snow falls (rather mixed units there). Most likely to fall just as a door is slammed shut.

    Posted By: Chris P Bacon@ST and what about his DHW costs?

    same applies, energy is energy, takes the same amount.
    Not rubbishing it at all, just saying that it has to be compared to a baseline and an all electric one is a good one as it is the most expensive (price) and costly (environmental) to run, but the cheapest to install.
    • CommentAuthorCWatters
    • CommentTimeApr 20th 2012 edited
     
    Posted By: Chris P Bacon
    Posted By: CWattersThe big question for me is what happens on a cold windless winters day when the panel is covered in snow and the heat pump is trying to make the panel colder still?

    What's the COP on a cold cloudy windless day?


    My understanding is there is a direct electric coil which takes over (or supplements) when the HP can't produce to the target temperature.


    Well yes exactly. What matters is for what percentage of the time does the booster have to kick in and is that more or less frequently than with regular fan assisted ASHP, and what does it do to the COP averaged over a typical year.

    How about a system with both types of collector? A roof mounted panel for the summer and a fan for the winter?
    •  
      CommentAuthorDamonHD
    • CommentTimeApr 20th 2012
     
    ...Or just a wall-mounted panel or three on a south-facing wall as part of the system, where possible?

    Rgds

    Damon

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