Most common solar powered fans are very low volume units. With two from another source, they indeed work, but provide very little air movement. Since the HF site does not mention output, volts, etc, hopefully someone with actual experience with these units can help. From my experience, for a 10X12, good passive ventilation, i.e. adequate roof vents and bottom side vents, provide ample ventilation in most conditions.

pcdur,

Why do you need solar?

cuestaroble,

The fan is 251CFM

chris,
Thanks for the cfm on the HF solar fan. Based on my calculations, a 10X12 needs ventilation of about 900 cfm in the summmer. If no top/side vents are provided, one would need about 4 of the HF solar units. Subtract the available top/side vents installed in the greenhouse to see if the HF fan will help. A range of passive vent area needed is 10-20% of the floor area for the roof, 5-10% for the bottom side vents, depending on the local climate.

cuestaroble,

The unit is actually a good deal if you get it at 40% off with a coupon. (if you don't connect the fan and use it in a greenhouse!)

a couple of decent sized solar panels, mounting brackets and a charge controller.

The PDF gives the details on what it is...

Here is a link that might be useful: PDF of the solar powered fan from HF

I use solar powered venting, although a homebrew system, not an HF one. And yes, it's pretty low power for your dollar. On the upshot, solar runs when you need the cooling the most and doesn't when there's no sun. The setup is pretty simple, too, and obviously it will eventually pay itself back. "Eventually" being measured in decades. ;)

I chose it for system simplicity. It made it so that I didn't need to run AC to the greenhouse (my greenhouse is off-grid), so I could use some DC fans I had lying around, and so I wouldn't need a thermostat for the fans (my vent has a thermostat, but I didn't want to mess with its wiring)

Oh, and another option for "solar" ventilation, if you have a tall tower nearby (say, from a wind turbine or tall tree): a solar chimney. Basically, hot air rises. You allow it to rise further into a black ventilation shaft, optimally with a glazing on the south side, that heats the air further. The shaft can go straight up, or you can run it horizontally for a while first, but the key is to get the most A) heating, and B) altitude at the exhaust vent. The opening on the vent should face away from the prevailing winds.

karenrei,

I use 12v DC in my greenhouse because when the power goes out then I am "off grid" Not because I am that environmentaly friendly and I use solar for power.

I charge up old batteries, from the grid and carry them to my greenhouse.

karen, or even steer the solar chimney vent away from the wind with a tail.

pcdur....funny i should run across this thread as i'm looking for the same solution. i was looking at fans and stuff at greenhousemegastore.com and according to their calculator i need 1440cfm of volume moving. this is for a 10x12 gh. the 12in fans move just over 1000cfm and the 16in 2000cfm. so i want a 16in. the harbor freight is only 6 3/4in and like the earlier poster said only 300 something cfm....way too inadequate. i'm in florida and when the OAT is 90f it can get to over 110f inside. i got 4 vents in the roof and intake vents all around the base and passive ventilation is not doing near enough. i designed and installed a misting setup and it does cool it down but it has to be on too much and i feel i will end up with rot problems. i'm growing orchids and they dont want to be wet all the time. anyway,...all of that to say the hf setup is inadequate. i dont want to have to run elec out to the gh but may have to. if i find something i think might work solar wise i'll post it here.

I've got the HF Solar Fan installed in my 6x8 HFGH. It is slightly under-powered for the GH, but I also have an AC electric box fan hooked to a thermostat.

I found that using a roof-panel was counterproductive b/c the Solar Fan (installed at the apex, above the door) would just suck the air from the roof-vent straight out the front (IOW: No cross-ventilation). That's why I ended up w/a screened panel (in the back) and a box fan, and I closed the roof vents.

On Hot Days I leave the door open (and have a screen hanging in the doorway). On not-so-hot (sunny winter) days, the Solar-fan seems adequate to meet my needs - even with the back-panel closed up w/polycarbonate.

No fatalities - Yet!

We put a page together describing the installation, see link below.

I highly doubt that *one* HF Solar Fan would be sufficient for the 10x12 GH, but it seems "adequate" for mine.

As always, YMMV...

BTW - The "controller" for my HF Solar Fan died after one season. DH, the Engineer, jury-rigged a new controller. I'll have to update the page to describe it but he essentially kept the HF controller as a thermostat, but rigged in a separate controller that diverts the electricity from the solar-panels to the storage battery.

If anyone is interested in the details of our Jury-Rigging Adventure, send me an email. I'll try to update the page to describe it - at some point (it's wintertime, so not much else to do!!!)

HTH

-Nancy (aka IMQTPI)

Here is a link that might be useful: 2007 Greenhouse Solar Fan