Running Greenhouse Exhaust Fan From PV Panels

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  • emboyd913
    Junior Member
    • May 2013
    • 2
    #1

    Running Greenhouse Exhaust Fan From PV Panels

    I own a hydroponic greenhouse operation (I grow lettuces, basil etc) on the Central Coast of CA. I am installing a couple of belt driven exhaust fans and want to run them off of some PV panels. The fans are 48 inches across and draw around 10.8 peak amps. I have a completely open south facing location to put them.

    I was hoping to connect the fans directly to the solar panel because I only need to run the fans when the sun is out and my greenhouse begins to heat up. Correct me if I am wrong, but from what I understand is that running a fan with too little power will not harm the motor in any way, only too much power.

    Is this type of system possible? I would like something to switch the fans off in case the sun is out, but it is still a cool day.

    Thanks for any help!

    Eric
    Tags: None
    • Sunking
      Solar Fanatic
      • Feb 2010
      • 23301
      #2
      What voltage are the fans using? I assume 120 VAC.
      MSEE, PE

        Comment

        • emboyd913
          Junior Member
          • May 2013
          • 2
          #3
          Originally posted by Sunking
          What voltage are the fans using? I assume 120 VAC.
          Correct, 120

            Comment

            • Sunking
              Solar Fanatic
              • Feb 2010
              • 23301
              #4
              OK you are talking some huge power numbers then. To take it off-grid you will be paying some 10 times more than what you pay the electric company to run those fans. Not a good biz decision. Bet you rcompetition does not do that.
              MSEE, PE

                Comment

                • Mike90250
                  Moderator
                  • May 2009
                  • 16020
                  #5
                  Without changing the fan motors out for DC motors, you are stuck. PV panels produce DC, the fans run on AC.

                  What you can do is to install a Grid Tie system, with all the permits and inspections and utility buy-offs. You will spend a lot of $ up front for it, and in exchange, lower your electric bill by 90% (if the system is engineered right) Then you can figure out if the payback period of saving 90% on the electric, will pay off the loan on the PV in less than 15 years. (note, grid tie shuts off if the grid fails, and your fans will stop.)
                  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

                    • FunGas
                      Member
                      • Aug 2012
                      • 99
                      #6
                      Maybe actuator driven windows are more efficient solution
                      Dem

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                        • SunEagle
                          Super Moderator
                          • Oct 2012
                          • 15160
                          #7
                          There are a number of DC fan manufacturers that could meet your needs and allow you to use a solar PV system. Depending on your CFM requirements you may end up with more smaller fans to get the desired air flow.

                          I use a couple of 14" fans in my attic to vent hot air build up. They each came with a small 10 watt solar panel that is mounted on my roof and the fans are mounted inside up against the static vent openings to my attic. There is a thermostat that turns on the fans if the temp exceeds 75 F so the fans don't always run during the colder months.

                          I don't think these fans would provide the amount of air flow you need but at least you can try to find something that does.

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