diy solar

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Solar direct to fan for Greenhouse

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Scott251231

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I have a small 12x10 green house I would like to add a fan to. I can't get power it early and was thinking about doing a solar fan. I just want to fan to be on whenever the sun is out. I actually two full size panels sitting around a buddy gave me a while back, they are good, just extra and he didn't want them. Schott Poly 225. I was hoping to only use 1 since they are large.

here's what I was thinking, LMK if you see any problems with this. Panel > Simple buck converter to bring the voltage down to 12v > 16" 12v radiator fan maybe 2 fans?


I could also get a 24v fan(s) as well if you think that's better


maybe this converter? Maybe on with an adjustable dial? IDK. https://www.amazon.com/Cllena-Autom...s=DC+voltage+regulator&qid=1625775827&sr=8-11

00B0B_j63aHyDs52Cz_0t20CI_1200x900.jpg
 
Welcome to the forum.

Yep. Exactly what I'd use. Should work assuming the following is true from the listing:

  • Protections: Over-load, Over-current, Over-temperature, Short-circuit, Over-voltage.

Panels rarely output peak power, and their power output follows something of a parabola during the day, so you'll want to select your fans accordingly. I would hesitate to put more than 100W on it.
 
snoobler said:
Welcome to the forum.

Yep. Exactly what I'd use. Should work assuming the following is true from the listing:

  • Protections: Over-load, Over-current, Over-temperature, Short-circuit, Over-voltage.

Panels rarely output peak power, and their power output follows something of a parabola during the day, so you'll want to select your fans accordingly. I would hesitate to put more than 100W on it.
Click to expand...
Something like this maybe? I really want to use the 225 panels I have since, well, I have them. I guess even if that means a charge controller and battery, then run the fans of battery + light diode.

Something like this maybe? To keep the voltage to the fans in check?
 
I'm sorry. I meant that I wouldn't put more than a 100W load on your 225W panel. No issue with the panel.

Not confident that controller will get you what you want, but it's cheap enough to give it a try... :)
 
snoobler said:
I'm sorry. I meant that I wouldn't put more than a 100W load on your 225W panel. No issue with the panel.

Not confident that controller will get you what you want, but it's cheap enough to give it a try... :)
Click to expand...
ohh gotcha!

Actually I guess its makes more sense to use a buck converter to keep the variable solar voltage down to a fixed 12v, then a PWM/POT controller to regulate the static 12v for "speed control" (IE , noise control hah)

ok thanks for the help.
 
Last edited:
Another question for y'all, what would the voltage of that panel be considered? 24v?

Right now all I have confirmed is it is making 35-38v open in full sunlight.
 
No. It's a 60 cell panel. Vmp of a panel is 1.5X nominal, so a 24V panel will have a Vmp of around 36V. Yours is around 30V, so it's a 20V panel.

60 cell panels are most common in grid-tie systems with high series voltage.
 
If you want to extend your "sun is shining" hours and widen the parabola, you could hook up the 2 panels in parallel and face one southeast.ish, and one southwest-ish. The idea is that this will start the fans as the sun hits the east-ish panel in the morning and runs until sun fades off the west-ish one in the evening.
 
I've used PV panels direct to a DC fan without issue. Works well and gets rid of one more piece of equipment that you have to deal with if you only need the fan running when the sun is shining on the panels. Just make sure the panel voltage is within range of what the DC fan motor can handle.
 
ok so when I put a load on this panel it should drop into the 20v range? I like the idea of using both panels to maximize the run times.

It they are 20v I should be able to run a 24v fan (or two) nicely then without a Buck or PWM. (I have not bought fans yet btw.)
 
Scott251231 said:
ok so when I put a load on this panel it should drop into the 20v range? I like the idea of using both panels to maximize the run times.

It they are 20v I should be able to run a 24v fan (or two) nicely then without a Buck or PWM. (I have not bought fans yet btw.)
Click to expand...

No. A panel's nominal voltage is intended to describe the battery voltage for which they are best suited to charge.

For that panel, when you draw 7.5A in perfect solar conditions, it drops to 30V.

Trying to eliminate regulated voltage between the panel and the fan is going to be a headache. an unregulated voltage source may damage the fan.
 
No need for a controller. Just get a DC fan, or a brushless DC fan (in case of brushless, best to be able to handle Voc of panels).
The trick if finding a brushless DC which tolerates slow ramp up of power input. Some will strain for a moment and quit. I selected some at a surplus store an tested with bench supply to find what worked.

I had some Pabst 24V fans which I placed on inverter heatsinks and connected to a "12V" panel. Also, a 48V rack fan which I mounted on gable vents and connected to two, "12V" panels in series. It ramps up and varies in speed with the sun.
 
ok so Im thinking the best option is to grab a buck converter to bring the cartable panel voltage down to 12v and just go with it that way. 12v fan.

Amazon.com: Cllena DC 8V-40V to 12V 10A Automatic Buck Boost Converter Step Down/Up Regulator Voltage Reducer Converter Waterproof Regulated DC Power Supply for Golf Cart Club Car LED Light : Electronics

Buy Cllena DC 8V-40V to 12V 10A Automatic Buck Boost Converter Step Down/Up Regulator Voltage Reducer Converter Waterproof Regulated DC Power Supply for Golf Cart Club Car LED Light: Power Converters - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com


Or just sell these after storing them for a year and pickup a ~100watt 12v panel, smaller too.
 
MisterSandals said:
No SCC's require a battery and that the battery be connected first and disconnected last.
Click to expand...
The wouldn't be such a bad thing right? a little battery in the middle with that "SCC" to managed the panel voltage for me?

I have a couple 4 and 8ah sealed lead acid batteries too I'm not currently using.
 
I do a LOT of stuff like what you're doing, especially with my solar swamp cooler that i run directly from solar.

I would try to run both your fans in series from the 2 panels in parallel. DC motors are not too particular about a little extra voltage. Keep an eye on them to make sure they don't get hot in which case you need a different solution. I would say really good chance it will be just fine.

Second solution would be to get a cheapie SCC, attach it to one of your little batteries (i use a LOT of 4ah gel cells and do this) and run from the SCC's load terminals to your fans, that way you won't kill your battery everyday (unless you can rig a low voltage cutoff in which case i'd definitely run from the battery.)

Give it a go direct from a single panel with 2 fans in series. How big are your fans? They're not big 24" fans are they?
 
MisterSandals said:
I do a LOT of stuff like what you're doing, especially with my solar swamp cooler that i run directly from solar.

I would try to run both your fans in series from the 2 panels in parallel. DC motors are not too particular about a little extra voltage. Keep an eye on them to make sure they don't get hot in which case you need a different solution. I would say really good chance it will be just fine.

Second solution would be to get a cheapie SCC, attach it to one of your little batteries (i use a LOT of 4ah gel cells and do this) and run from the SCC's load terminals to your fans, that way you won't kill your battery everyday (unless you can rig a low voltage cutoff in which case i'd definitely run from the battery.)

Give it a go direct from a single panel with 2 fans in series. How big are your fans? They're not big 24" fans are they?
Click to expand...
I actually have not bought the fans yet. My greenhouse has two spots, 21" squares I build for future fans. I can use any size lower than that.

Im looking at 12v 80w cheap radiator fans off amazon, there are a couple 24v models too. Not sure yet.

Yea, a SCC + a 4ah seems like a solid solution.
 
Scott251231 said:
Yea, a SCC + a 4ah seems like a solid solution.
Click to expand...
The only issue is the the SCC load outputs are rally NOT meant to power very much. Make sure you check the load ratings. There are usually some nice on/off timers in some of the cheapie SCC's which is a plus. And if you toast one, its about $15 (for the cheap blue pwm 20a ones that i use for general purpose use like what you're doing. I have 4 and haven't killed one yet.)
 
Ok I’ll give them a try right off the panel first and see how that goes. Should I get 12v fans or 24v? 12v is more available and cheaper for sure.
 
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