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Solar Powered Fan to aid ventilation?

Discussion in 'Poly-Tunnel Gardening' started by Quackerjack, Apr 8, 2017.

  1. Quackerjack

    Quackerjack Apprentice Gardener

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    Has anybody tried using a solar powered fan, or maybe a 12v fan, to help ventilate a polytunnel? I have a 14' x 28' polytunnel, mesh covered window at bottom end (with roll-down plastic sheet for a curtain). I've been wondering about buying a solar powered fan or a 12v fan to run off a battery, but ones I've seen online don't look as though they'd make much of a draught and the solar powered ones are quite expensive. (Mains electricity not really an option.) Has anyone used one? Do they actually shift much air?
     
  2. Zigs

    Zigs Naughty Ginger Admin Staff Member

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    Probably a bit of an expensive set up, you'd need a leisure battery and a charge controller as well as the panel so you'd be looking at £100 ish and then the cost of a fan.

    Cheaper set up would be a small panel directly wired to a computer fan at the apex of the back wall. It would come on when the sun comes out and take the rising hot air out.

    I've powered one from the solar panel on an old battery charger.

    If you can't get a computer fan then model shops sell small 12 volt motors :)

    @Canadian Lori would be able to tell you more:fingers crossed:
     
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    • Marley Farley

      Marley Farley Affable Admin! Staff Member

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      I have tried 2 x 6" solar fans in my 8 x 6 greenhouse but to be honest they didn't really make any difference to the temp..

      I have a 27' x 15' poly tunnel and to get the air to move on a still day would require some mighty fans and I really don't think Solar will cut the mustard in there unless big min 12" powered by electricity or I don't they they will make a scrap of difference.. ;)
       
    • Quackerjack

      Quackerjack Apprentice Gardener

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      Hi,
      Thanks for replying. I have wondered about computer fans before, but I had it in my head that they are usually 9v? Don't know where I got that from. I've already got a panel/charge controller and leisure battery anyway (fantastic for keeping the ride-on lawnmower charged). Not sure if my wiring skills are up to it though - I can wire a plug but that's about my limit. I usually manage to break anything that I try to repair. :sad:
       
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      • Quackerjack

        Quackerjack Apprentice Gardener

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        Thanks for replying. I was afraid that would be the answer. Maybe Zig's idea of removing hot air from the top of the tunnel might help. If I can do it cheaply then I'm sure it can't hurt!:fingers crossed:
         
      • Marley Farley

        Marley Farley Affable Admin! Staff Member

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        @Quackerjack I will be most interested to hear how you get on doing that.. I was lucky enough to be able to face my tunnel into the prevailing wind direction for me which is the west, so my tunnel faces West X east?. I stay out in the summer and go in in the cool of the early morning or in the evening when the sun has gone off it.. I then wet the path down as well after I finish evening watering to keep the humidity up a bit until the next day's sun.. It certainly helps too..
         
      • ricky101

        ricky101 Super Gardener

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        Just been trying out a 12" 50w mains fan in my 8x6 gh just to act as an air circulator rather than extractor.
        At full speed it does move the air around ok but for a large pt doubt it would have much effect after a few feet.

        Before bothering with fans, try what Zigs says and make an opening at the top of the apex on one end of the tunnel and then a similar sized opening at the bottom of the other end.
        That should create a natual draught though the whole tunnel and out a the top of the apex.

        Fitting fans will aid the removal of the hot air if the above not enough.

        A 12v 120mm PC case fan uses about 100ma of current so a 60A + leisure battery should last several weeks, even more if you have it on a day /night timer and solar charger.
        Would suggest you will need several fans to produce enough air movement in such a big area.
         
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        • Zigs

          Zigs Naughty Ginger Admin Staff Member

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          Pm me if you need a hand, I set up my system - wind and solar pv myself :)DSCN0766.JPG
           
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          • Webmaster

            Webmaster Webmaster Staff Member

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            Rather than relying on electric to power a fan, have you thought of using plain magnets ?

             
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            • CanadianLori

              CanadianLori Ever Hopeful Canuck

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              Yes. I run what are zcalled "personal"fans that one would normally plug into your usb on your computer plus I run dc fans that are turbine and others that are dc ceiling fans. Then I havd a server fan as well. The ceiling fans are on timers because they create quite a breeze.

              They all run from solar panels either directly or via batteries.

              Things stay nice and dry out there ... er, well about 40% humidity. No mildew or mold.
               
            • CanadianLori

              CanadianLori Ever Hopeful Canuck

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            • Quackerjack

              Quackerjack Apprentice Gardener

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              Fascinating. I'm not sure I'd agree with 'free energy' though, as presumably somehow the magnet was 'charged up' when it was made. I don't know much about magnets ( can't remember that far back to school!) but surely the magnet will eventually lose its magnetism, depending on how it was made. Worth looking into though.
               
            • Quackerjack

              Quackerjack Apprentice Gardener

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            • Quackerjack

              Quackerjack Apprentice Gardener

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              My tunnel also faces east-west, slight slope down from east to west, door at east end and window at west end. I've a big row of trees behind it at the west end though, which provide quite a good wind break. Great protection from gales, but also stops gentle breezes - can't have everything!
              Why do you want to keep the humidity up at night? I've wet down the path in my greenhouse before, but always in the morning. I thought that humidity at night is likely to cause moulds?
               
            • Marley Farley

              Marley Farley Affable Admin! Staff Member

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              I wet the path down after watering on the really hot days and it just evaporates really well.. I think it helps them recover a bit after the heat of the day as temps can get very silly in the tunnel as not got any shade.. ;)
               

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