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Thread: Solar panel used to power fan directly

  1. #1
    mikesoneill Guest

    Default Solar panel used to power fan directly

    I want to use a harbor freight or similar solar panel to power a fan that will move air from a solar heat collector to my house. I was going to avoid the use of batteries if possible. The fan is a Rule 240 bilge blower which is 12v and draws max of 4.3 amps. The Harbor Freight solar panel kit is 12v, 45 watts and 3 amps. Of course with lower levels of sun the performance would be below those levels.

    Can I connect the panel directly to the blower? If the voltage drops too low will that damage the motor? Do I need some sort of voltage controller?

    Thank you for your help. Mike

  2. #2
    Join Date
    Mar 2006
    Location
    SF Bay Area (California)
    Posts
    19,676

    Default Re: Solar panel used to power fan directly

    Probably not--The typical brushed motor is pretty voltage tolerant. Go ahead and connect--measure the fan voltage and see if it is OK.

    It is very possible though, that you will need a larger solar panel to start the fan and run it under less than full sun... The "proper" way to run a blower is with a Linear Current Booster (more or less the MPPT of the battery less DC world).

    7 amp Linear Current Booster/Pump Driver

    But, they are not cheap... It may cost less to just buy a second solar panel and connect it up.

    Poster 2manytoyz--On his website, he has a solar attic fan project which is similar to what you are probably looking at:

    http://2manytoyz.com/solar.html

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  3. #3
    Join Date
    Dec 2010
    Location
    Woburn, MA
    Posts
    463

    Default Re: Solar panel used to power fan directly

    If the motor needs a max of 4.3 amps, and the Harbor Freight panels can only supply 3 amps.. The motor isn't going to work real well. You need more PV power.

    I've got some panels that work well with a 12v battery charger..


    Notice at max power, they put out 17.4 volts. And with a light load, they put out 22 volts.
    Not really good for connecting directly to electronics that require 12vdc..

    Simple solution.. Use off-the-shelf hardware. Start with a 50 to 70 watt PV panel.
    Buy a small 12v battery (6Ah would work) and use a charger
    with 'load' terminals good for at least 5A, that disconnect the load
    when the battery voltage drops under ~10 or 11 volts..
    Hook it up and it will keep the fan going, even when a cloud comes over..

  4. #4
    Join Date
    Apr 2010
    Location
    Austin, TX, USA
    Posts
    1,838

    Default Re: Solar panel used to power fan directly

    Quote Originally Posted by mikesoneill View Post
    I want to use a harbor freight or similar solar panel to power a fan that will move air from a solar heat collector to my house. I was going to avoid the use of batteries if possible. The fan is a Rule 240 bilge blower which is 12v and draws max of 4.3 amps. The Harbor Freight solar panel kit is 12v, 45 watts and 3 amps. Of course with lower levels of sun the performance would be below those levels.

    Can I connect the panel directly to the blower? If the voltage drops too low will that damage the motor? Do I need some sort of voltage controller?

    Thank you for your help. Mike
    It may not work all that well, but it won't hurt the motor. Folks run DC water pumps directly off solar modules all the time. How much water the pumps move is dictated by the intensity of the sunlight on the module(s).

  5. #5

    Default Re: Solar panel used to power fan directly

    Thanks BB for the mention.

    I'll bet it'll work. Just won't spin full speed since the load is higher than the panels can supply.

    I've connected brushed, and brushless, 12V fans directly to solar panels for a while now. While they spin full speed in full sun, the amount of sunlight varies throughout the day. Morning, evening, clouds, etc.

    I could stand in the garage and hear the audible speed changes as clouds would pass by. That said, this audible speeding up/slowing down, might get a bit annoying if you're near the fan.

    Try it for now, you can always add more panels later... along with batteries, charge controller, blah blah. It gets addicitive, be warned!
    Robert
    Central FL
    http://www.2manytoyz.com
    900W of solar panels, 860 AH 12V battery bank (8 6V Golf Cart Batts), Xantrex Prosine 1800W inverter, Xantrex Prowatt SW2000 inverter, 2 Prostar 30M controllers, 1 Morningstar Sunlight 10L controller, Iota 75A charger (for rainy days), Furrion 30A automatic transfer switch, Yamaha EF2400iS generator.

  6. #6

    Default Re: Solar panel used to power fan directly

    Solar powered attic fans do exactly this.
    12 kw Generac, Yamaha EF2400is, 4.2 kw APC UPS powered either by battery or a Prius. Really.

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