# Solar Fan for Greenhouse- Advice please :)



## ChristieAcres

I would like to get a solar fan for my little 6 X 10 greenhouse, but not sure which would be the best type or brand. I am in Zone 8b, so our summers do get some heat, but not sweltering (90s rarely, and surpassing usually are record temps here)...usually in the 80s. 

Here is a picture of my greenhouse (only one vent). My DH will be able to mount whatever type of fan I do get:


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## TnAndy

Well, the do make gable vent fans with a remote 10w solar panel to power them...but the cheapest I see them for is about 200 bucks...here's one on Amazon.

http://www.amazon.com/Air-Vent-53560-800CFM-Solar/dp/B0013K3XT6

But also notice on the same Amazon page, a 120vAC gable fan ( the CX1500 ) which has almost twice the CFM rating, and only costs 48 bucks.....

Now....ask yourself....how long is it gonna take to over come the 150-160 buck difference in price of the solar fan versus the 120vAC model ? 

Figure the fan will run 'maybe' 5 hrs, and the AC fan uses ( 3.4a x 120v ) maybe 400w....which probably costs you about a nickel an hour or 20 cents per day the fan runs...and figure it runs 100 days/yr.....20 bucks/yr....7-8 years payback, at least.

I looked at both, and wired in a 120vAC model.


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## Windy in Kansas

My advice would be to calculate how many cubic feet of air you need to move and then select a fan of appropriate size, and a PV panel and battery bank to support the needs of the fan.

Even small greenhouses need a lot of air flow to prevent overheating.


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## ChristieAcres

There is approx 270 cubic feed of air. The greenhouse is 6 X 10. I found this type of fan, but would like an opinion:

http://cgi.ebay.com/Solar-Panel-Roof-Vent-Fan-Green-House-Cell-Ventilator_W0QQitemZ390095719773QQihZ026QQcategoryZ41980QQcmdZViewItemQQ_trksidZp3286.m7QQ_trkparmsZalgo%3DLVI%26itu%3DUCI%26otn%3D2%26po%3DLVI%26ps%3D63%26clkid%3D8989930644111059634

On hotter days, I will keep the door & vent open. I am also getting a shade cloth. If I went for a smaller fan like the above one, would I need 1 or 2 of them. Or is this simply "junk?"


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## TnAndy

*"These units move air slowly and quietly,"*

No CFM rating given, but based on the 6" size, I suspect you are likely to be disappointed with the amount of air they move.


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## wy_white_wolf

Putting an automatic opener on the vent would do more then that fan. I would look into adding 2 or 3 more roof vents and a lower vent to allow air in.


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## Jim-mi

With those "inexpensive" fans you will see the blades moving but feel darn little air movement (if any).

A good solar powered fan and PV panel will be a bunch of bucks. . . .and you still will need to put in a vent.

The vents WWW talks about will be far more effective. . .for way less bucks.


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## artificer

For an "on the cheap" system you could use the O2-cool fan. Either 12v from power supply, battery adapter, or 8 D-cells. They say 40hrs on D-cells. If the D-cells have 8amp-hrs that means the fan draws 2.4 watts on low. Quadruple for high (a guess), and you're still under 10 watts. Double that so you can still run early mornings and late evenings with lower angles to the sun.

Cost is $20 for the fan, $150 for a 20watt panel. A smaller panel will still run the fan, just slower. You might even get by with a $80 10watt on high speed. The solar panel is going to be your biggest cost. Spend as much as you want/can on that, and get a fan to match. The one you posted is probably only a 70mm muffin fan and a 1.5watt solar panel. (it uses a 3" hole) You can get computer muffin fans cheap. All it takes is a bit of wiring.

Do you have grid power at the cabin? (or so it looks) Is that why you want solar?

People: please notice she mentioned leaving the vent and door open. No automatic vents needed... just air movement.

Here's a slightly off the wall idea for a solar powered exhaust: The black chimney duct system. Put a black flue pipe on the end/top of the greenhouse. 6' should be good. The bottom is elbowed into the greenhouse, and the top is open. Sun heats the air in the pipe, and it rises. It draws air from the greenhouse to replace it. Passive ventilation. Might be ugly, and I'm not sure how well it would work, but its a cheap possibility.

Michael


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## artificer

Forgot to ask: Is the picture showing a roof vent? Does it already have an automatic opener? 

Just wondering...

Michael


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## ChristieAcres

Thanks all you guys for your responses! I will have to spend a bit of time thinking about this, before making a decision.

Michael- 

The garden cabin is wired, but the line hasn't been ran, yet (DH will be digging the trench and also running water/power to it). In the meantime, we have a long extension cord he uses for the equipment he has on the deck of it (the projects we are doing out there). When he insulated the garden cabin, he will be installing rough hewn Cedar to finish the inside walls, then installing my sink, etc...

I don't want to use electricity or regular batteries to run the fan, so that answers that Q.

There is one roof vent, not an automatic one. Since I work from home, can open/shut it when needed, also open/shut door when needed, for ventilation (screening it). Keeping in mind high 80s is usually the hottest it gets here, have hose, and can spray it down occasionally to cool it down. Also, getting shade cloth to help (don't want to cook the plants as I know it can get hot in there...). 

The idea of a chimney for passive ventilation is an interesting idea. DH is a Welder/Machinist, so if I come up with some idea, he can build whatever I need. The sunken floor should help a little...

On venting, I can have DH cut additional vents, if needed, also. Right now, that greenhouse is a sore spot of conversation. Primarily due to it needing to have all the panels screwed into place and the structure itself needs reinforcement. So, the way the shelving was installed, added a lot of strength. There is a lot of weight against the base, due to all the pea gravel, sunken beds, and then the framework was attached to the walls of the greenhouse, also to the beds. To further strengthen it, we just need to add a few 2 X 4s, up against the others. After he did all that, it did withstand a 55mph wind storm we had. However, I did have him park our old truck in front of it/blocking the wind to a degree.

The type of greenhouse? I bought it via Costco online. No, wouldn't recommend this type as it shouldn't have taken any extra work to make it withstand 20mph winds, as it was with them popping out, DH had to screw down every panel! Fortunately, that helped it withstand the latest high winds.


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## mightybooboo

150 for a 20 watt panel????

Folks,get snooping on Craigslist,I bought panels all day long at 2 dollars a watt,friend got 800 watts at a buck a watt,another bought unisolar 64's for 60 CENTS a watt!

Used panels are a steal on pricing,just look and save yourself some major bucks right now.May take a while to get a deal,its worth the time IMO.


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## artificer

mightybooboo said:


> 150 for a 20 watt panel????
> 
> Folks,get snooping on Craigslist,I bought panels all day long at 2 dollars a watt,friend got 800 watts at a buck a watt,another bought unisolar 64's for 60 CENTS a watt!
> 
> Used panels are a steal on pricing,just look and save yourself some major bucks right now.May take a while to get a deal,its worth the time IMO.


I've been looking for a year, and I still haven't found anything local. Where am I supposed to be finding all of these great deals?

Michael


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## cowboy joe

wy_white_wolf said:


> Putting an automatic opener on the vent would do more then that fan. I would look into adding 2 or 3 more roof vents and a lower vent to allow air in.


Agreed. I bought one of these units to try out as it was about half the price of those I found elsewhere. The push on retaining caps fell off all the time so I ended up replacing the hardware on the brace with long screws & bolts. Seems to do the trick for about a $1 in hardware. 

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92192


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## wy_white_wolf

mightybooboo said:


> 150 for a 20 watt panel????
> 
> Folks,get snooping on Craigslist,I bought panels all day long at 2 dollars a watt,friend got 800 watts at a buck a watt,another bought unisolar 64's for 60 CENTS a watt!
> 
> Used panels are a steal on pricing,just look and save yourself some major bucks right now.May take a while to get a deal,its worth the time IMO.


Not everywhere has panels for those prices on Graiglist. I've been checking every day for over 2 months and nothing locally or the 6 states surrounding me. I think it's just a California thing. 

Going price for a new 20 watt panel seems to be in the $100 to 150 range. Cheapest option new might be to use 1 - 15w panel out HF's 45 watt kit. That way if she wanted more air circulation she would just have to find 1 or 2 more fans.

Lori,

I think you will find the automatic openers to be a big help. All it takes is 1 time for something to come up and to keep you from getting to the greenhouse to overheat and kill everything. That one time could cost you more than the opener does.


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## ChristieAcres

Thanks for all the tips. Okay, I am sold on using automatic vent openers  So, I will start there.

Then, I will do more research on getting a fan. I still have to get a shade cloth for it, too. Since April has been forecast to be a colder month, I do have time to get this all figured out and now have more info to utilize!

BTW- I did look for used solar panels on CL They weren't cheap locally!


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## mightybooboo

It does take a lot of looking to find em.Takes me about 20 minutes a day to check on em and they arent always there by any stretch.But we have em,why a calif thing would seem odd,though our economy is really reeling here.

You can get 240 watts new panels here for 288 dollars,1.20/watt!I wouldnt pay 5 to 7.50
watt for a 20 watt panel,there are much better options IMO.

http://sunelec.com/index.php?main_page=index&cPath=5&zenid=c2c3175f0b11744f4357deeb245f47cb


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## wy_white_wolf

BooBoo,

If she was wanting batteries in the greenhouse I might agree. But since she doesn't I have to say those panels are worthless for this application. With a VOC of 91.8V and VMP of 67.0V the range is just to wide. Finding a fan/motor that could operate solar direct in that voltage range would be a bigger chore than finding cheap 12v panels. 

That would also limit ones options on finding a thermocouple to turn the fan on an off. I wouldn't use one anyway, but some like them.

Cheap panels of odd voltages on small systems usually end up costing more in the long run. 

WWW


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## artificer

mightybooboo said:


> It does take a lot of looking to find em.Takes me about 20 minutes a day to check on em and they arent always there by any stretch.But we have em,why a calif thing would seem odd,though our economy is really reeling here.


A reeling economy means people are selling whatever they can. Also, MUCH more solar in SoCal than the midwest, so used is going to be more common.



mightybooboo said:


> You can get 240 watts new panels here for 288 dollars,1.20/watt!I wouldn't pay 5 to 7.50
> watt for a 20 watt panel,there are much better options IMO.
> http://sunelec.com/index.php?main_page=index&cPath=5&zenid=c2c3175f0b11744f4357deeb245f47cb


So if you only need 20 watts of power, you would pay $288 for (4) 60 watt panels? How about the next cheapest: $511 for 210watts? That's 10-20 times what she needs to power a fan.

Even 20 watts at $8/watt is going to be more useful and cheaper than the Kaneka panels. Its not always about the $/watt. I'd love to have half a grand to get some of these panels, but my solar budget, right now is $200, which means $4-$5/watt. If you don't have the money for the cheaper panels, it doesn't matter how great the deal is... you're not going to be able to afford them.

Michael


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## blooba

lorichristie said:


> Thanks for all the tips. Okay, I am sold on using automatic vent openers  So, I will start there.
> 
> Then, I will do more research on getting a fan. I still have to get a shade cloth for it, too. Since April has been forecast to be a colder month, I do have time to get this all figured out and now have more info to utilize!
> 
> BTW- I did look for used solar panels on CL They weren't cheap locally!


I had to hook up fans to get some air movement to stop mold growth on the soil in seedlings in my greenhouse about that size. They don't really help for cooling it off so I have a mister system for that. But I have 3 4" fans 12v computer server fans running in there to solve that issue. Just one panel (forget what size) and a motorcycle battery run them.

Wish I knew what size it was but I got it used for free.

Automatic vent openers :goodjob:


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