Solar fan in barn - revisited

BrassmanBrassman Registered Users Posts: 2
Back in 2013 there was a discussion thread about solar power for cooling fans in a barn. I'd like to ask more about that topic.

I'm looking at an AC fan that draws 4.6 start-up amps, 2.3 running amps. I'd like to control it with a thermostat so it only runs when the temp is 80+. It would only be needed in the summer months.

1) Could solar panels be run directly to an inverter, and on to the fan, or would they have to go through a battery first?
2) Either way, I may want to use a battery system anyway, to power lights in the winter. They would be on for minutes a day - not very long at all.
3) If I go with a battery system, how much battery/panel capacity would I need? I've been following the calculations I've seen here, and I think I'm getting the idea......

Previous posts have mentioned the cost effectiveness - that running cable out to the barn would be cheaper. While that is certainly true, I would REALLY prefer solar, if it can be done without too much blood,sweat, and tears.

Any input would be greatly appreciated!

Comments

  • froggersixfroggersix Solar Expert Posts: 35
    why do this if you've got grid? it won't be cheaper. couple o amps at 120 volts is 240 watts and if run all day thats near 6kw hours which would be less than a dollar a day from grid or needing thousands investment in batteries panel and inverter.
  • BB.BB. Super Moderators, Administrators Posts: 29,497 admin
    In general, the true solar power attic fans are much smaller motors, and much less airflow.

    If you can just open a hole in the side of the barn (louvered/screened as needed) or a cupola on the roof--That would compete pretty well vs a typical forced air solar fan.

    If you really want to go with solar power--You need to find a DC fan that can be powered by solar, and check the life rating of the motor.. Many inexpensive DC motors are brush type motors and only will last a few thousand hours before brushes need to be replaced.

    PM Motors + Electronics to run from solar panels (brushless motors), are not cheap.

    If you really need a fan, a thermostatically controlled AC fan will be more cost effective for the long haul (typically) and move 10x the amount of air of a typical solar fan + attached solar panel (24 Watt DC fan vs 240 Watt AC fan).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Solar Expert Posts: 4,994 ✭✭✭✭
    Not Cheap, but Backwoods Solar does offer a 16" brushless fan that will work off solar, This should work fine just disconnect and cover for winter.... http://www.backwoodssolar.com/products-fans-small-large-dc-super-fan-16inch-12-24v
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • JohannJohann Solar Expert Posts: 240 ✭✭✭
    Brassman wrote: »
    Back in 2013 there was a discussion thread about solar power for cooling fans in a barn. I'd like to ask more about that topic.

    I'm looking at an AC fan that draws 4.6 start-up amps, 2.3 running amps. I'd like to control it with a thermostat so it only runs when the temp is 80+. It would only be needed in the summer months.

    1) Could solar panels be run directly to an inverter, and on to the fan, or would they have to go through a battery first?
    2) Either way, I may want to use a battery system anyway, to power lights in the winter. They would be on for minutes a day - not very long at all.
    3) If I go with a battery system, how much battery/panel capacity would I need? I've been following the calculations I've seen here, and I think I'm getting the idea......

    Previous posts have mentioned the cost effectiveness - that running cable out to the barn would be cheaper. While that is certainly true, I would REALLY prefer solar, if it can be done without too much blood,sweat, and tears.

    Any input would be greatly appreciated!

    At what voltage is that AC fan taken those amps.
  • BrassmanBrassman Registered Users Posts: 2
    Finally got an electrician out to do an estimate for running AC out to the barn. The estimate is just under $900. I'm going to try the DC fan from Backwoods Solar. Thanks for the link, Photowhit.
  • BB.BB. Super Moderators, Administrators Posts: 29,497 admin
    There was one poster here (as I recall) that got the smaller / self contained solar power fan+solar array. Installed a bunch of them in the roof and saw the attic temperatures fall...

    Then years later, noticed that most (all?) of the fans had failed (I don't remember/know why--But I would suspect motor failure) and found that the attic temperatures were still much cooler than before the installation. Just punching enough holes in the roof to install the solar fans increased air flow enough to keep the attic cool. The solar fans did not really do anything useful otherwise.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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