diy solar

diy solar

Solar direct to fan for Greenhouse

I used a 24V brushless DC fan with 12V panel, 48V brushless DC with 24V panels (two 12 in series)
With brushless DC you are taking a chance if Voc of panel exceeds rated voltage of fan. Even Vmp of a "12V" panel is about 17V.

If brush type (no electronics) not so much risk.

But if 12V brushless is cheap and available, you can try your luck.
 
ok I wasn't happy with the 24v fan options and prices. I ordered up 2x 12v 14" fans and a couple options (with free returns) for managing the voltage based on this thread. I think if they don't work out I will sell these panels and get some 12v units to run my stuff.

Still.. kinda hoping the battery option works out. I could put something bigger on it and use it for lights at night too maybe. The SCC I got is 30a/in 20a/out. (thanks for the tip on the output, the one I had originally was only 10a out)

Ill post back how it all works out.
 
ok I got my fans in and hooked up for testing. Right now im directly attaching the two 12v fans in series making them a 24v load. Im using only 1 panel ATM and it does start up the fans just fine even without direct sun light, just inside the greenhouse for the time being. It works... at peak sun im seeing 30v as expected but the fans draw on that and it drops up and down with sun.

Noise... the fans are very loud at full sun, im gonna need to to something about this TBH. Considering a SCC+battery, then I can put them in parallel (12v load) and use a 12v DC motor controller on them. I think that will work... Im just very of the SCC's I see cheap, some bad reviews I mean it is China trash.

Performance, thy do move air, not as much as I would expect but you can feel a good amount coming off the back. still hard to say if its helping, the green house is cooler, 10-12* hotter than outside . I need to measure it without the fans on but I feel like it was a good 20+ hotter inside before the fans.
IMG_0797.JPG


Also anyone know if these plugs are something I can buy pigtails for? so I don't have to cut them off when I make this all nice and tidy? Don't mind my bare foot outside, what a goober

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Scott251231 said:
Performance, thy do move air, not as much as I would expect but you can feel a good amount coming off the back. still hard to say if its helping,
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I wonder if having one blowing air in and one blowing air out would move a lot more air?
Ideally the input would be low and the exit up high.
You could check the flow where they are and help heat exchange by putting a partition between the fans...maybe diverting each one to the side. Or if you could put some kind of duct so the out blowing one drew air from up high, where its presumably hotter, it would help.

Regarding 12V parallel vs 30V serial, i suspect your fan noise will be pretty similar. If they're not getting hot then they be just fine.
 
Scott251231 said:
Also anyone know if these plugs are something I can buy pigtails for? so I don't have to cut them off when I make this all nice and tidy?
Click to expand...
Looks like MC4 connector, if so you can just search for "mc4 extension" and cut the extension cord however you want.
 
Those fans look awefully small. What is the diameter? That is likely why are so noisy (or they are plastic and not well balanced). For less noise you typically use larger diamater fan so that they can blow same volume of air as a smaller one but at a lower rpm. Switching to regulated DC is not going to fix that.
 
rhino said:
Those fans look awefully small. What is the diameter? That is likely why are so noisy (or they are plastic and not well balanced). For less noise you typically use larger diamater fan so that they can blow same volume of air as a smaller one but at a lower rpm. Switching to regulated DC is not going to fix that.
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Fans are 16". those are 24" box's. My original plan was to pull AC power out to the green hours and use cheap box fans in the frame I built. But Soal sounded fun and I kinda wanted to learn a little about this stuff. So this is just experimenting for when I do something larger.

When I had my DC motor control between the fans and the panels it seemed to work to quiet them down (slowing them down), it was just unstable with the panels input voltage changing on it.

MisterSandals said:
I wonder if having one blowing air in and one blowing air out would move a lot more air?
Ideally the input would be low and the exit up high.
You could check the flow where they are and help heat exchange by putting a partition between the fans...maybe diverting each one to the side. Or if you could put some kind of duct so the out blowing one drew air from up high, where its presumably hotter, it would help.

Regarding 12V parallel vs 30V serial, i suspect your fan noise will be pretty similar. If they're not getting hot then they be just fine.
Click to expand...

both are exhaust currently. The entire front door is all screen so my thinking was just taking hot air from up high out of the house will help. It does feel like its working though. Putting in a thermometer tonight actually then I will have better numbers. I am experimenting here for sure. I may move fans around, the wife is planing on starting the plants in there soon. We also have an indoor green house but its small.

I did just order a cheap 30a SCC with I think 15a out, I have a 12v 6ah battery im gonna use. That will still run the fans on Max at 12v, but it will be a nice stable ~12v out so the DC motor controller should work nice on it. that motor controller was acting weird between the panels on the fans alone.


for veggies btw... no weird hippie stuff here :p
 
Scott251231 said:
that motor controller was acting weird between the panels on the fans alone.
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Have you tried directly from panel to fans? I am assuming its a PWM controller and that could do funny things. I've been using server fans for years with solar swamp cooler, greenhouse ventilation and air circulation directly from solar.
 
MisterSandals said:
Have you tried directly from panel to fans? I am assuming its a PWM controller and that could do funny things. I've been using server fans for years with solar swamp cooler, greenhouse ventilation and air circulation directly from solar.
Click to expand...
Yea that's how it is now, direct of the panel. I just went out to inspect out, its full sun directly above. The panels are making 16v with the load attached so the fans were humming along full speed and loud lol.

Side note, it's only 4-5* hotter in the house than outside now, so it is working! just a bit loud.


This is what im thinking will be solid, what do you think? If my thinking is right getting my PWM controller (not currently in use) a static ~12v should let it function properly throughout its adjustment range. Added bonus is has a "off" function :)

30v 250w panel > SCC + 12v battery > PWM 12v DC controller > 12v Fans in parallel.
 
Rider said:
If it were me..... I'd get a bunch of these:

or a couple of these:

I get that this is DIY and the adventure in creating something, but for me, there is a time to just get something that's already available.
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yea, my issues with the solar attic fans. 1. never found one that lasted for nothing 2. expensive! im about $50 into this now 3. they hardly move any air. The little RV things are a joke, and at $36 a pop lol. Naw, this system is cheaper, more reliable and will move way more air.
 
Scott251231:

I'm setting up a small greenhouse for my wife, and my plan is similar to what you are working on. I'm going to use a small bank of lithium titanate batteries to provide some storage in the greenhouse, for a light, radio, small water pump, etc. That would be 24v nominal.
A good source for all sorts of surplus stuff is Surplus Nebraska. Just outside of Omaha. They sell a lot of fans for very reasonable prices.
 
if anyone is wondering... im doing some formal temp testing. It is 88* 5 feet outside the green house. Without the fans on the temps rose to 136* in about 30mins. The fans are back on, its recovering now, was 108* in just a few mins. Ill go check it in a bit.

So it is working lol.

IMG_0806.JPG
 
I use a Treadmill Motor. I attach a Fan blade from a cheap chineese house fan. I mount it on a bar stool. It runs on a 50watt solar panel 18 volt. It draws 1.3 amps at 18 volts. It is insanely great. It moves a ton of air. These Treadmill motors are like 120 volt DC Brushed. Their Industrial Grade. They last forever.
 
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...
What is an SCC?

Could you please tell me what solar DC fans you have?
 
cara2000 said:
What is an SCC?
Click to expand...
Solar Charge Controller

cara2000 said:
Could you please tell me what solar DC fans you have?
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All my DC fans are computer and server fans. The ones for my swamp cooler are 24V and about 6" diameter - i run them direct from solar panels sometimes but they run better from a 24V battery (2x 4Ah 12V gel cell in series) charged from solar with a cheapie PWM SCC.
 
Hello, I've been reading a lot online about solar panels, 12v batteries, voltage regulators, etc. Some say that you can connect the solar panel to the fan and others advise differently.

Last year I bought this exhaust fan/solar panel/battery combo. It lasted maybe 2 months when the battery died. Then i read about hooking it to a 12v battery with a voltage regulator; however the end connectors wouldn't be compatible. Maybe there's an adapter?

Then I see listings online for just a fan and solar panel combo, no battery. So needless to say, I'm confused.

So question is, can I just strip the ends of the wires from the fan and connect them straight to the solar panel? My husband says that the motor of the fan will burn out. My greenhouse is 20x8".

Thanks!
Connie
 

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naturemaiden said:
hen I see listings online for just a fan and solar panel combo, no battery. So needless to say, I'm confused.

So question is, can I just strip the ends of the wires from the fan and connect them straight to the solar panel? My husband says that the motor of the fan will burn out. My greenhouse is 20x8".
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Do you have any details on the fan motor itself? I've used two separate DC fans connected directly to a solar panel and had no issues but those fans specified a wide voltage range and not simply "12V".
 
I have four 5vdc computer fans in series directly tied to a panel. I measured the current the fans draw using a bench power supply to make sure the panel can source at least that much. The fans in series can take the full open circuit voltage of the panel I have, and the current they draw is less than the max current the panel can provide. They make a lot of noise when the sun is directly on the panel, but the panel can't burn them out since its full voltage is lower than their total rated voltage.

@naturemaiden , my next post has a link to fans that should match your panel if you put them in series.
 
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