Best power arrangement for solar air heater?

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  • Matt98svt
    Junior Member
    • Apr 2019
    • 3

    Best power arrangement for solar air heater?

    So after watching some of the popular YouTube videos on solar air heaters I ordered a 10 watt solar panel off amazon to pair with a 120mm 12vdc .25amp computer fan for my solar air heater project.. In the videos they connect directly from fan to panel and it spins with ease. Of course my luck my fan spins very nicely when in the full summer sun but the slightest cloud and it comes to a complete stop. I can only image in winter months it would hardly work at all so now looking at what I really need to cost effectively make this solar air heater fan work where the fan will spin continuously in overcast winter weather. I'm guessing I need a charge controller but what kinda battery would be right for this? A used lawn/motorcycle battery? Lithium battery pack? Maybe a fan that requires less power? Any input greatly appreciated!


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  • bcroe
    Solar Fanatic
    • Jan 2012
    • 5203

    #2
    Originally posted by Matt98svt
    So after watching some of the popular YouTube videos on solar air heaters I ordered a 10 watt solar panel off amazon to pair with a 120mm 12vdc .25amp computer fan for my solar air heater project.. In the videos they connect directly from fan to panel and it spins with ease. Of course my luck my fan spins very nicely when in the full summer sun but the slightest cloud and it comes to a complete stop. I can only image in winter months it would hardly work at all so now looking at what I really need to cost effectively make this solar air heater fan work where the fan will spin continuously in overcast winter weather. I'm guessing I need a charge controller but what kinda battery would be right for this? A used lawn/motorcycle battery? Lithium battery pack? Maybe a fan that requires less power?
    A cloud could easily knock the available power down to 10% to 25% of the panel rating, below the fan
    requirement. Batteries will only delay the failure, but make it much more expensive.

    HOWEVER, part of the problem might be your fan using current in much larger pulses than the
    stated average, putting the system out of action when the panel can not supply that level. I
    would try putting a capacitor across the fan so that the panel does not need to supply the peaks,
    might allow the fan to run at somewhat clouded level, at reduced speed. I would try about
    2000 ufd at 20V, observing polarity as a test. A scope will tell the story.

    That may still be inadequate, the final fix is a 12V 50W or 100W panel that will produce enough
    power even under some clouding. If voltage rises too high in best sun, you might need a regulator.

    Bruce Roe

    Comment

    • Mike90250
      Moderator
      • May 2009
      • 16020

      #3
      I'd suggest a 50w panel, if you can borrow one to try. Cloudy/overcast don't expect more than 10% of nameplate output. But in cloudy conditions, you won't have much hot air to move either.

      I'd also recommend getting a 14V 80W zener diod to wire in with the fan to prevent the panel from zapping it with 21.6 v on a sunny day like a 1N3305, 2 in series, to get the needed wattage, and a heat sink to dump the excess power into
      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

      solar: http://tinyurl.com/LMR-Solar
      gen: http://tinyurl.com/LMR-Lister

      Comment

      • chrisski
        Solar Fanatic
        • May 2020
        • 553

        #4
        Originally posted by Mike90250
        I'd suggest a 50w panel, if you can borrow one to try. Cloudy/overcast don't expect more than 10% of nameplate output. But in cloudy conditions, you won't have much hot air to move either.

        I'd also recommend getting a 14V 80W zener diod to wire in with the fan to prevent the panel from zapping it with 21.6 v on a sunny day like a 1N3305, 2 in series, to get the needed wattage, and a heat sink to dump the excess power into
        I realize this is an old thread, but I had no idea you could wire two zener diodes in series.

        Comment

        • bcroe
          Solar Fanatic
          • Jan 2012
          • 5203

          #5
          Originally posted by chrisski

          I realize this is an old thread, but I had no idea you could wire two zener diodes in series.
          It is something like 2 batteries in series. Bruce Roe

          Comment

          • Mike90250
            Moderator
            • May 2009
            • 16020

            #6
            Zeners in series. If you need 14V @ 50W, you can us two 7V @ 25W and spread the heat easier. The drawback is you have a "softer" knee as the diodes turn on and start conducting,

            If you try to put in parallel, one will "hog" and burn itself out, so you have to use "swamping resistors" (ballast resistors) so the resistor helps raise the resistance of the conducting path and then another diode will kick in, and another and another......
            Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
            || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
            || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

            solar: http://tinyurl.com/LMR-Solar
            gen: http://tinyurl.com/LMR-Lister

            Comment

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