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Green Living: Solar Panels (for heating water) - why do it?

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      CommentAuthorSteamyTea
    • CommentTimeOct 4th 2014
     
    Posted By: jamesingramLike a trombe (thermosiphon) wall ?
    That is how I would do it.
    Trouble is that I don't think there is that much energy to be got. Easy enough to do the sums though.
    Probably find for drying timber just moving air though it is as affect as anything. How 'windchill' works.
    It is all down the physics not so much the energy source.
  2.  
    Posted By: SteamyTea
    Posted By: jamesingramLike a trombe (thermosiphon) wall ?
    That is how I would do it.
    Trouble is that I don't think there is that much energy to be got. Easy enough to do the sums though.
    Probably find for drying timber just moving air though it is as affect as anything. How 'windchill' works.
    It is all down the physics not so much the energy source.


    I know the technology works as I visited a site while in Austria using the system for drying woodchip but I cannot remember whether it had the PV panels on the top. Apparently there is a big new M & S distribution centre near Leeds fitted with it on the vertical south aspect but not with the PV panels fitted.
  3.  
    Hi SteamyTea, I presume you were talking about the Sunpower panels, which I believe the manufacturer only sells to approved installers. BenQ make modules that appear to share exactly the same design (though they are made in a different factory) which seem cheaper and more widely available (though still significantly more per watt than the 250W panels).

    I've been looking into them for our roof as it will only fit 12 panels of an average sort of size, so 12x330W seems the way to go.

    Ed
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 5th 2014
     
    Yes it was the Sunpower ones. Not looked since as I still have the problem of not being able to DIY at the moment, and not got the cash to free at the moment.
    • CommentAuthorjamesingram
    • CommentTimeOct 5th 2014 edited
     
    Steamy did you see my whispered comment on last page re costing of benQ. If you can find someone to sign it off then diy is possible. Vat is an issue though. You'd need a supply and commission deal. Probably unlikely to find a willing helpful pv company?
  6.  
    £6695 was the lowest I've seen advertised for a 12 panel (4 kW) BenQ 330 W system so still a fair bit more than the cheapest 16 panel systems.

    Hopefully It'll drop a bit more by next year when hopefully we can have it installed with the new roof covering. I am still dubious though of whether using grid-tied solar PV for water heating can be justified on environmental grounds in most cases.

    Ed
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 5th 2014 edited
     
    Seen it now James. Thanks.

    I shall have to ask around, I know a few people in the industry that may be able to help.

    My main point about DIYing it is that if they cut the FITs by much more then it is not worth going down the MCS route (was set up to reduce the payments and make the industry self reliant after all).
    Just have to find out if it is possible to get paid for exports though a smart meter and what the rates will be.
    If I can generate at 7p/kWh then it is a no brainer, at 14p, assume the kit costs £7000 installed and I can offset 2.5MWh/year then it is marginal. And that would assume staying in the house for the next 20 years, or taking the stuff to the next place (which is an advantage of DIYing it.
    • CommentAuthorEd Davies
    • CommentTimeOct 5th 2014
     
    Posted By: jamesingramLike a trombe (thermosiphon) wall ?
    Note, not all thermosiphon walls are Trombe walls - a Trombe wall necessarily has high thermal mass whereas other types of thermosiphon walls can be thermally lightweight, which might be more appropriate in the case of cooling PV where you want to move the heat away from the scene as promptly as possible.
  9.  
    Posted By: jamesingramSteamy did you see my whispered comment on last page re costing of benQ. If you can find someone to sign it off then diy is possible. Vat is an issue though. You'd need a supply and commission deal. Probably unlikely to find a willing helpful pv company?


    Hi James,

    please could you whisper this to me too as I'd be interested as I need to know how much we'll need for reroofing + solar PV.

    Thanks,
    Ed
    • CommentAuthorwookey
    • CommentTimeOct 7th 2014
     
    Who would buy such a system?


    People who understand that they have a carbon budget of 1, maybe 2, tonnes a year for _everything_ (travel, heating, stuff, food).

    ST gives you a few MWh of (almost) carbon-free heat. 'payback' doesn't really come into it. Using PV instead can make sense, but mostly due to the external financial incentives. On an areal basis ST gets a lot more watts/m2 but does helpfully supply not enough for 1/3rd of the year and way too much for some of the summer. (PV also has this problem, but is not quite so unhelpfully skewed).

    Mine cost £800 to install, which does make the finances look a lot better, and it's been great for 5 years now.
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 7th 2014
     
    Wookey
    What sort of system do you have, FP, EV, homemade?
    How is it plumbed in and did that 800 include a new cylinder?
    •  
      CommentAuthordjh
    • CommentTimeOct 7th 2014
     
    Steamy asked: "Wookey
    What sort of system do you have, FP, EV, homemade?
    How is it plumbed in and did that 800 include a new cylinder?"

    The answers are at

    http://wookware.org/solar/

    http://wookware.org/pics/solar/
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 7th 2014
     
    Thanks

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