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  1.  
    I was surfing about on you tube and found a video on DIY cooling of solar PV panels. The video was shot in Australia where loss of efficiency due to hot solar panels was a particular issue. The youtube poster's solution was to plumb in irrigation that covered the panels in a fine spray. Several comments on the video mentioned problems with doing that (I won't go into them here) and mentioned alternatives such as heat sinks and solar cooling fans.

    I came up with a solution that would use up some bits and bobs I have lying about, but before I go off and try it, I thought I'd run it by the experts on here so I don;t end up wasting my time - or worse, end up ruining my solar panels!!

    I was wondering if you bonded UFH aluminium spreader plates (150mm centers) onto the back of a solar panel, using heat conductive adhesive and ran UFH pipes through them, whether this would cool the panels down sufficiently to improve their efficiency on a hot summers day?

    I could rig a solar powered bilge pump taking water from our stream, pumping it through the spreader plates and then back into the stream. Alternatively, I could use the luke-warm water to irrigate our allotment (I read somewhere that plants do better with warm water than cold from the tap). I have a surplus solar thermal controller that I could rig up so that the pump only works when the panels reach a certain temperature and could design it so that it works as a 'drainback' system so that the pipework is empty when the pump isn't running.

    The net cost would (I think) be pretty negligible. The spreader plates are relatively cheap, as is the pipework (I'm fitting UFH in my living room at some point so would need both of these anyway). I was already looking at buying a bilge pump and small solar panel to irrigate our allotment, which is next to the garage the panels are installed onto, so not much extra cost to run the pipework to the garage. The water is freely available and I'm allowed to extract upto 20 cubic metres per day.

    The following questions come to mind:

    1. Would this damage the panels in any way? Either with the bonding of the plates to the back or due to the cooling of the panels (bear in mind that the panels are about 1.5m long and the spreader plates are 1m long, so would there be a problem with parts of the panel being cooled directly (the centre 1m) and parts being cooled indirectly (the 250mm at the top and bottom not covered by the spreader plate)?

    2. Is it worth the effort? Do we have a problem with efficiency loss due to hot panels in the UK like they do in AUS and other much warmer countries? Would the reduction in temperature be sufficient to actually make a difference to the efficiency?

    3. Would this actually even work?
    • CommentAuthortony
    • CommentTime6 days ago
     
    It would work but not sufficiently to make it economic here.
    •  
      CommentAuthorSteamyTea
    • CommentTime6 days ago
     
    PV modules often have 'sticky back plastic' as the underside coating. I would not do it.

    We have discussed this before, so should be able to do a search on here.

    If a module is tested at 800 or 1000W.m^2, and the sun is hitting it at 1100W.m^2, you still get the ten percent uplift initially, but higher thermal losses. These may well equal out.

    There is also the quirk to do with the angle PV is installed at. This is often the angle of the existing room and is often less than optimum during the summer. This can be mistaken for thermal losses.
  2.  
    <blockquote><cite>Posted By: SteamyTea</cite>We have discussed this before, so should be able to do a search on here.</blockquote>

    I've tried a few options "Solar PV Temperature" "Solar PV Cooling", etc. but without success. Anything less specific ends up with solar thermal discussions. Could you do me a favour and post a link to any of these discussions?

    My main aim is to determine whether PV panels in the UK get hot enough to have their efficiency impacted enough to make this worthwhile. I have 4kw of in-roof solar panels and 1.8kw of partial in-roof panels, so they just rely on surface ventilation for cooling. There is little cost in doing this, just my time and effort (which I don't want to waste if this idea isn't going to work, as I have a hundred other projects on the go :) ).

    The attached photo shows the in-roof solar panels (2kw on the west side of the roof). The stream that would provide the water is just behind the garage.
      PV_West.jpg
    • CommentAuthorcjard
    • CommentTime6 days ago
     
    And I thought my garage was cool.. That's awesome.

    Given that they're intended to cope with rain, would you not just be better off having a sprinkler at the top? what was the issue with the misting?
    • CommentAuthorgyrogear
    • CommentTime6 days ago
     
    could you not just "simply" cool them with air, such as by making an inside enclosure then fanning cold air from somewhere via a duct etc. ?

    O/W, A Very Nice Garage as said above :cool:

    gg
  3.  
    Thanks for the complements about the garage. I'm pleased with how the solar panels worked out, and they looked good enough to the reverse the planning department's decision to not allow us to have solar panels (I had to fit them without waiting for permission because the Tories pulled the rug on FIT payments without much warning). A stressful time, but all sorted now.

    I can't find the original youtube video (isn't that always the case), but one of the comments was that the water contained minerals that might build up on the panels? I'm not sure how reasonable that argument is, unless they're being sprayed 24/7 for 10 years.

    I did find a thesis that looked at using water sprays to cool panels and it gave a glowing review of that particular technology, not just for cooling but also for keeping the panels very clean which also boosted output. It'd certainly be much easier to implement a spray than cooling on the back of the panels, though how consistent the cooling would be with a spray in the windy hills of the South Pennines, I'm not so sure. I think the missus might get annoyed if she is sat on the patio (on the left of the garage where the slates we removed are sat) and keeps getting hit with a fine spray of water every time the wind changed direction. :bigsmile
    •  
      CommentAuthorfostertom
    • CommentTime5 days ago edited
     
    Thomas the Tank Engine is just about to come chuffing out - no doubt he's become hybrid by now!

    Those huge 'slates' - are they actually slate, up there, or some other laminar stone? My old house in Bath (1790) had enormous original green slates - over a metre square x half inch thick, half rotted unfortunately. Never seen the like before or since, esp in Bath.
    • CommentAuthorcjard
    • CommentTime3 days ago edited
     
    I was thinking more of a sprinkle/trickle than a spray/mist. Copper pipe with plenty of tiny holes punched along its length at its most basic.. Assuming the water isn't saturated with hard minerals, i don't see why any accumulated deposit wouldn't wash off again over night if sprayed with more water (like that it was formerly dissolved in) - your pump will have battery storage for the solar?
    • CommentAuthorgravelld
    • CommentTime1 day ago
     
    Whatever happened to the PV/ST hybrid systems? I thought this was basically how they worked.
    •  
      CommentAuthorSteamyTea
    • CommentTime1 day ago
     
    Posted By: gravelldWhatever happened to the PV/ST hybrid systems? I thought this was basically how they worked.
    I think people realised that it was cheaper to just install PV and plug it into a heater. The price of ST against PV is now relatively high, unlike a decade ago.
    • CommentAuthorBeau
    • CommentTime1 day ago
     
    I think minerals could be problem. We have a spring supply and if you end up with a slow leak anywhere staining occurs quite readily but it does wash off.
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