powering small circulating fan w[ solar cell

System
System Posts: 2,511 admin
in Solar Beginners Corner #1
I built a solar air collector and need a small fan to help the thermosiphoning effect. Thought about a computer fan hooked to a solar cell. Can this be done?
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #2
    Re: powering small circulating fan w[ solar cell

    Computer fans can be had for nearly nothing from computer recyclers. A ~4" square 12vdc might draw ~15 watts. I would suggest that you find a 24vdc fan, plug it into a ~10-15 watt "battery minder" panel used to keep car batteries topped up. The 24vdc fan will run slower than the 12 vdc one, but won't get toasted if the panel puts out more voltage than the fan can handle. (Probably won't hurt the 12vdc one either though!) Put a fuse in the line and try it. Should work fine. No controls needed, as the fan will turn only as fast as the sun will allow, so it will shut down down when the collector shuts down.

    Tony
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  • System2
    System2 Posts: 6,290 admin
    #3
    Re: powering small circulating fan w[ solar cell

    Thanks for the info.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
    Re: powering small circulating fan w[ solar cell

    in answer to your question of 1 cell running a fan the answer is, no it can't. 1 solar cell will not output that much voltage as they are usually just over 1/2v for each cell. you could find yourself needing about 36 cells give or take to do this on a 24v fan motor as tony mentioned. even boost converters would need more than 1 cell to work. now along tony's line of thinking you could use a 12v fan with half the number of cells for about 18 cells total. the cells must also be able to deliver the current needed by the fan motor.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #5
    Re: powering small circulating fan w[ solar cell

    To clarify myself, and perhaps to clarify Niel: There is a semantic difference between a "solar cell" and a "solar panel", even if they are used interchangably. A solar PANEL is usually made up of a number of solar CELLS, wire in a series/parallel arrangement to produce a useable voltage/current. So a small "solar panel" that I suggest might be ~17voc or a bit more, with maybe .3 amps, putting out ~ 5 watts. This would be made up of a series of smaller cells.

    What you need is enough cells to power the load, in this case a simple fan that might draw 5 watts of less at ~12 vdc. The fan really doesn't care if it is running on 12 volts, or 7 or 17 vdc (within reason) the only thing different would be the speed it runs, higher voltage= higher speed.

    Tony
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  • tvengineer
    tvengineer Solar Expert Posts: 31 ✭
    #6
    Re: powering small circulating fan w[ solar cell
    muttmom wrote: »
    I built a solar air collector and need a small fan to help the thermosiphoning effect. Thought about a computer fan hooked to a solar cell. Can this be done?

    I have been able to get a cpu fan to run on only 3watts of panel...
    I have 3 of the one watt battery minder type panes from Harbor Freight...

    If you need MASSIVE amount of air flow.. I have been using a fan from HOme Depot.. it is meant to be a battery powered fan used on construction sites..
    It is made by Ryobi and HD sells them for about $30...
    I have one hooked directly to a 20 watt panel to ventilate my attic..
    As it is it runs slowly even in the evening ... with the sun shining on the panel it move quite a lot of air... benefit for attic vent and for your application.. more sunshine.. more air flow
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