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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorphiledge
    • CommentTimeApr 20th 2019
     
    Anyone give their panels and or tubes an annual wash down? Is there any science confirming its worth it in extra output?
    • CommentAuthortony
    • CommentTimeApr 20th 2019
     
    A mate of mine runs several large rooftop arrays of PV

    Two were identical on 30degree pitched roofs

    He cleaned one of them but it made no difference, both systems clean and dirty generated the same

    I have concerns about very shallow pitched panels on flat roofs
    • CommentAuthorowlman
    • CommentTimeApr 21st 2019
     
    I bought a water fed telescopic pole, with a couple of different inter-changable heads. which I also use for roof-lights etc.. It certainly makes the panels look nicer especially the frames, not sure how it affects the output though.
    Mine can get quite dirty with tree dirt and domestic bee crap.
    • CommentAuthortony
    • CommentTimeApr 21st 2019
     
    If it is easy then do it
    • CommentAuthorphiledge
    • CommentTimeApr 21st 2019
     
    Ive been using tree pole pruner with window washing sponge on the end but its a bit of a pain dragging a hose pipe up on the ridge of the house to wash from above.

    Tonys mates experience seems pretty conclusive so I might skip every other year
    • CommentAuthorbhommels
    • CommentTimeApr 22nd 2019
     
    Most modern solar panels have cover glass sheets with self-cleaning nano coatings or patterning. Covering/filling these with limescale from tap water is not a good idea. So unless you rinse with deionised water or descaling solution I would recommend to wait for the next natural rinse cycle (rain).
  1.  
    most in the industry suggest they may benefit from a clean once a year.
    I clean mine once or twice a year.
    Id be suspicious of basing my reasoning on one single example
  2.  
    •  
      CommentAuthordjh
    • CommentTimeApr 26th 2019 edited
     
    I was doing a survey today that asked about my annual solar generation. I just realized that's probably a good way to answer this question too. I've kept annual generation totals, which are:

    2016 3963.86
    2017 3822.45
    2018 3884.38

    So I'm fairly happy that I'm not seeing any reduction through dirty panels :bigsmile:
    Or faulty panels :bigsmile: :bigsmile: (although my microinverters should make me aware of that if/when it happens)

    edit: oh, I forgot to mention that I haven't cleaned them at all. They're exposed on the roof with nothing overhanging them (I saw some recently that were green with growth induced by nearby trees) but some are at a fairly flat angle (since my roof is curved, the angle varies).
  3.  
    https://www.bbc.co.uk/news/uk-scotland-48037362
    Saharan dust: Why your car is covered in red dirt

    Does this stuff have any effect on solar panels? I had to clean it off my windscreen.
    • CommentAuthortony
    • CommentTimeApr 26th 2019
     
    Yes but it will wash and blow off again quite soon
    • CommentAuthorJeff B
    • CommentTimeApr 27th 2019
     
    I have only ever hosed my PV panels once or twice in the 8 years they've been up. Our tap water is very soft BTW.

    Although the back walls of the house need an annual clean due to green algae (lots of trees behind the house) this does not seem to be an issue with the PV panels - maybe a combination of the rain and the special surface of the panels makes the difference?

    Like djh I have not seen any gradual decline in PV output. Some variation from year to year certainly (3000 kWh +/- 10%) but no downward trend.
    • CommentAuthorJeff B
    • CommentTimeApr 27th 2019
     
    Just had a look at the link posted by jamesingram as above:

    https://www.popularmechanics.com/science/energy/news/a27112/pollution-can-block-25-percent-of-solar-power/

    Wow, no wonder those panels have reduced output - I don't think I would need a university study on my panels to tell me that I have a problem!
    • CommentAuthorphiledge
    • CommentTimeApr 27th 2019
     
    Surprised theyve got any output!!
    • CommentAuthorJeff B
    • CommentTimeMay 1st 2019
     
    Graph of our PV panels output from 2011 to 2018 attached. Output varies from (low) 2896 to (high) 3374 kWh. No special cleaning treatment. Just natural variation from year to year I would say.
    • CommentAuthorbhommels
    • CommentTimeMay 1st 2019
     
    When posting generation figures can we please normalize to kWh/kWp, so divide your generation by the installed peak output rating? It makes it easier (possible) to compare outputs.
    • CommentAuthorsam_cat
    • CommentTimeMay 1st 2019
     
    That chart made me twitch. Such huge variance - Then - Oh, its not 0 - x, its just showing the top of the chart.
    • CommentAuthorJeff B
    • CommentTimeMay 1st 2019
     
    <blockquote><cite>Posted By: sam_cat</cite>That chart made me twitch. Such huge variance - Then - Oh, its not 0 - x, its just showing the top of the chart.</blockquote>

    Lies, damned lies and statistics comes to mind! Graph as used by some of well known daily newspapers to make things look either terribly bad or amazingly good. I just let Excel choose on this occasion. Let the "buyer" beware and check the axis (axes)!
    • CommentAuthorJeff B
    • CommentTimeMay 1st 2019
     
    Hopefully this revised graph will satisfy both bhommels and sam_cat!
    • CommentAuthorbhommels
    • CommentTimeMay 1st 2019
     
    Lovely, thanks :-)
    • CommentAuthorsam_cat
    • CommentTimeMay 2nd 2019
     
    Much better, thanks! :)
    Far easier to see now that the variance is well within what you would expect.
    • CommentAuthorsam_cat
    • CommentTimeMay 2nd 2019
     
    I log mine in a similar fashion, but month on month and overlaying years:
    https://i.imgur.com/XVmTYMCl.png" >

    Part of a bigger spreadsheet where I monitor energy usage as well as generation.

    https://i.imgur.com/TQR7F0ml.png" >
    • CommentAuthorJeff B
    • CommentTimeMay 2nd 2019
     
    sam-cat - sorry but I cannot read your graphs as the image I get is tiny. Maybe it's me or my PC to blame?
    • CommentAuthorsam_cat
    • CommentTimeMay 3rd 2019
     
    Try these links:

    Solar section charts
    https://i.imgur.com/XVmTYMC.png

    Solar, Electric and Gas charts
    https://i.imgur.com/TQR7F0m.png
  4.  
    Posted By: Jeff Bsam-cat - sorry but I cannot read your graphs as the image I get is tiny. Maybe it's me or my PC to blame?

    Tiny image on my pc as well - however Ctrl and + together increase the size, hold the Ctrl key down and each poke of the + key steps up the size. This works for most web sites, including this one and Ctrl and - reduces size
    •  
      CommentAuthordjh
    • CommentTimeMay 3rd 2019
     
    Posted By: Peter_in_HungaryTiny image on my pc as well - however Ctrl and + together increase the size, hold the Ctrl key down and each poke of the + key steps up the size.

    True but that was no use with the original links. The text was unreadable even when enlarged. The second set of links cured the problem.
    • CommentAuthorJeff B
    • CommentTimeMay 3rd 2019
     
    Yes, the second set of links work ok. Thanks sam_cat. Whereabouts is your installation? Mine is in west Wales.
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