Suitcase panel on shed roof?

[LearningIt]

I have a 100 Watt expertpower suitcase panel (see ExpertPower or Amazon) and 200W/200Wh S200 solar generator. I want to add a panel to the roof of my 4x6 generator shed to power an exhaust fan for ventilation both for storage when the weather is hot and when the ICE generator is running during a power outage. I'm in a hot humid climate.

My shed roof is regular 3 tab shingles over osb but tilts (3 in 12) north, away from the sun. The south generator wall is close to the fence and the east and west walls are shaded.

Is there a good way to mount this panel to the roof with the legs extended to make it tilt south? I can place it on the roof and the angle works but I want a semi-permanent mounting. The legs don't have holes through the bottom for mounting pins but I could drill them. How would I also attach the edge that touches the roof on the south side?

Are these suitcase panels waterproof/weather resistant enough to stay outside or should I get a regular panel?

Has anyone else used a "12V" panel connected directly to something like a 12V electric automotive fan like this?
Good/bad idea?

I don't really want to leave the expertpower solar generator turned on and in the outside shed providing power to the fan. I think that would hurt the battery

 

[Rednecktek]

Sounds like a case for some basic shelf L brackets and screws.

 

[Bud Martin]

I have a 100 Watt expertpower suitcase panel (see ExpertPower or Amazon). I want to add a panel to the roof of my 4x6 shed to power an exhaust fan. I'm in a hot humid climate.

My shed roof is regular 3 tab shingles over osb but tilts (3 in 12) north, away from the sun.

Is there a good way to mount this panel to the roof with the legs extended to make it tilt south? I can place it on the roof and the angle works but I want a semi-permanent mounting. The legs don't have holes through the bottom for mounting pins but I could drill them. How would I also attach the edge that touches the roof on the south side?

Are these suitcase panels waterproof/weather resistant enough to stay outside or should I get a regular panel?

Has anyone else used a "12V" panel connected directly to something like a 12V electric automotive fan like this?
Good/bad idea?

I don't really want to leave the expertpower solar generator turned on and in the outside shed providing power to the fan. I think that would hurt the battery

This guy uses radiator fan and PWM speed control.

 

[HarryN]

If it were me, I would just buy a normal panel and mount it more conveniently.

Those suitcase system panels aren't really intended for that kind of use.

The fan that you linked to lists as being ~ 80 watts, so you will want at least 2x that much solar panel capacity to drive a fan directly.

I have not tried that but it isn't obvious why it would not work. Easy enough to test before installing.

I would be tempted to mount the panel on the wall facing the sun in the afternoon - even if that makes it vertical. There isn't any reason why you can't mount panels in two directions to capture sunlight and feed it to the fan AFAIK.

Since the panel voltage could hit close to 20 volts sometimes, it "might" make sense to consider buying a 24 volt fan instead of a 12 volt one. Digikey sells all kinds of fans of various voltages - and they likely will be much more reliable then something sold on amazon. I never buy anything electronic / electrical from amazon. Too many fake items.

 

[LearningIt]

If it were me, I would just buy a normal panel and mount it more conveniently.

Those suitcase system panels aren't really intended for that kind of use.

The fan that you linked to lists as being ~ 80 watts, so you will want at least 2x that much solar panel capacity to drive a fan directly.

I have not tried that but it isn't obvious why it would not work. Easy enough to test before installing.

I would be tempted to mount the panel on the wall facing the sun in the afternoon - even if that makes it vertical. There isn't any reason why you can't mount panels in two directions to capture sunlight and feed it to the fan AFAIK.

Since the panel voltage could hit close to 20 volts sometimes, it "might" make sense to consider buying a 24 volt fan instead of a 12 volt one. Digikey sells all kinds of fans of various voltages - and they likely will be much more reliable then something sold on amazon. I never buy anything electronic / electrical from amazon. Too many fake items.

Thanks. The south generator wall is close to the fence and the east and west walls are mostly shaded so the roof seems like the only place available. (I just updated the original post.)

I'll check DigiKey now too.

Good point on the fan rating vs the panel maximum output. Don't most of these fans not need a regulated voltage, but will run at a speed as a positive function of the voltage, within some range? And the panel will produce a voltage as a function of the insolation?

If I have just a "100W 12V" panel for an "80W" fan (this suitcase one or a normal one), it will rarely if ever get to the full 100W/18V and normally the fan would see closer to 12V. Maybe that would be OK. The fan shouldn't have sensitive electronics that are killed if sometimes it had higher voltage around 18V.

Will better brushless fans will last longer? I expect the fan to run several hours a day at least in the summer even if I put it on a temperature controlled switch to turn on only when above 85F.

So during the day the panel voltage (and power for a load) will rise then fall with the brightness and incidence of the sun, as will the speed of the fan. The fan presumably has some minimum voltage to start spinning, and will spin faster and move more air with rising brightness, which corresponds to rising temperatures. I want the panel voltage function and fan speed function to move enough cfm to exhaust hot air and ventilate the shed so it stays ambient air temperature.

I don't want the shed to get too hot. The shed does have open soffits and a radiant barrier roof. Around here, with 90-100F summer temperatures, attics (at least without adequate ventilation or radiant barriers) can get 120-150F. I put a temperature sensor in the shed to monitor temperatures but I just built it so I don't know what the non-power-vented temperatures would be in the summer.

 

[HarryN]

Brush less fans or blowers are definitely the way to go.

A fan produces air velocity but very little pressure, a blower uses more power, but produces both air velocity and pressure.

A bathroom exhaust "fan" is actually a "blower". A blower is used when the air has to move through a duct.

For instance a radiator fan is a "fan", but the "car heater fan" is a blower because it needs to move the air through a heat exchanger and some duct work or no air movement will really happen.

I pretty routinely use the comair rotron and pabst units. They have fairly long life spans and are quiet.

I think that the better bathroom exhaust fans are in the ~ 100 scfm range and it would take at least that much to do much IMHO.
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I don't have any experience directly wiring a solar panel to an end device without a battery and some kind of charge controller in between.

I am interested by the idea though.

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I do have experience using 12 and 24 volt fans / blowers at lower voltages than their rated voltage with battery packs. I did this by trial and error to hit a lower current draw without using a controller and it works. For instance ran a 12 volt blower with a 6 volt battery pack for a bunch of reasons.

________________

 

[HarryN]

I am just going to use this panel as an example of what might work for you and what to keep in mind in building things up. I don't have any affilation with the retailer nor the solar panel company but have used this particular panel on conversion vans.

SLP090-12F Silver Poly 12V

Solarland SLP090-12F 90 watt module, 12v

unboundsolar.com

Most people will correctly state that it is poly - so not as efficient as a mono crystalline panel, and that is correct - when in good sunlight.

A poly panel will be better for less than perfect sunlight conditions and non optimal mounting angles. So on partly cloudy days it will be better, but not as good in perfect light.

__________

This is a pretty typical spec for small solar panels. If you look at the number "Voc" (open circuit voltage) it could in theory hit 22 volts, but under load will come down to whatever it takes to run the fan. What I don't know is if the output current is too low to start fan rotation, could the voltage go up to Voc ? Not sure, which is why I suggested to consider using a 24 volt fan or blower.

If that voltage does hit 22 - 23 volts in a 12 volt fan - it might damage it. With a 24 volt version - it won't care.

Maybe it is possible to mount the panel on a wall that will catch more light, even if it is not on the shed itself?

 

[Jennifer]

I have a Schneider tri panel suitcase system and a Renogy as well and one thing to be mindful of is the usually PWM SCC mounted on the back of the units, they're ok but they're not really intended for full time outside use, you may want to remove it and put it inside where it's dry.

 

[LearningIt]

Possibly, one could use a buck converter to reduce the variable voltage from a panel to the actual 12V (up to 15V) that an automotive fan requires, without having to use a battery and charge controller.

 

[Rednecktek]

Being as those automotive fans in the car normally run from a 14+ volt alternator, feeding it 15v from a panel should be well within tolerances.

 

[LearningIt]

I got the radiator fan and as a test, I connected it to my car battery and separately to my 100W suitcase panel under overcast skies. From the 12V battery it ran very fast but quietly. The panel showed 22.5V open circuit and 6V when connected to the fan. It still ran reasonably but more slowly.

 

[pollenface]

Those suitcase system panels aren't really intended for that kind of use.

Aren't they just 2x panels joined with a hinge?

 

[pollenface]

Possibly, one could use a buck converter to reduce the variable voltage from a panel to the actual 12V (up to 15V) that an automotive fan requires, without having to use a battery and charge controller.

Definitely. I have a small panel connected to a buck converter to supply exactly 12.3v to a couple of relays (my sun switch).

 

[Rednecktek]

I got the radiator fan and as a test, I connected it to my car battery and separately to my 100W suitcase panel under overcast skies. From the 12V battery it ran very fast but quietly. The panel showed 22.5V open circuit and 6V when connected to the fan. It still ran reasonably but more slowly.

Yup, that's the voltage drop from the fan running under load. Even the best 100w panels are lucky to get 5a at working voltage under optimum test conditions. With DC fans the voltage controls the rotational speed so once the fan was sucking down all the amps, the voltage drop caused the fan speed to be reduced.

Just out of curiosity, is there a data sticker on the fan with the voltage/amperage numbers on it?

 

[LearningIt]

There was only the 12V 80W sticker on it but the Amazon page showed "5-7 amps." I only really need it to run fast, or really just run at all, when the sun is bright and it's hot outside so I will test it in bright conditions too.

I often see used 200-350W panels that would fit on my shed roof if needed. They seem to have 30 - 40V Vmp and Voc so I should be able to use them with a buck converter and the fan.

 

[Rednecktek]

There was only the 12V 80W sticker on it but the Amazon page showed "5-7 amps"

Yup, there's your problem. The fan is trying to draw 7 amps from what is probably a 5a-At-Best-In-A-Perfect-World panel. If you had 2 in parallel it might very well run at full performance in optimum sun.

Aren't they just 2x panels joined with a hinge?

Nope. While the actual silicon of the cells may be the same, the rest of the construction is different. To make a panel into a folding suitcase style you have to give up the glass on the front, the aluminum frame, and some of the thicker material in the substrate and replace all that with thinner plastic to cut the weight down. Doing that drastically reduces the durability and rigidity of the panel, the protective face is now a softer plastic instead of harder glass which gets scratched and dinged much easier and will degrade in sunlight, the whole panel is more flexible so the traces under the actual cells can be twisted and torqued around which can cause breakage, etc.

That's why the folding portable suitcase style panels aren't really a good option for permanent mount, they just can't take the physical abuse.

 

[LearningIt]

Thanks for the description of the suitcase panels' construction. I used mine as a Proof of Concept here but plan to check out onesy larger conventional panels.

 

[pollenface]

Nope. While the actual silicon of the cells may be the same, the rest of the construction is different. To make a panel into a folding suitcase style you have to give up the glass on the front, the aluminum frame, and some of the thicker material in the substrate and replace all that with thinner plastic to cut the weight down.

Okay. The ones I've seen are just normal panels with a hinge on them. Aluminium frames and all.

 

[LearningIt]

I tested this with the 100W suitcase panel and the 12V fan in bright sun. I measured 11-12V with the fan load and it ran similarly to being on the auto battery. I don't have a tachometer or cfm meter to quantify it though.

I'll probably look for a decently priced normal 200-300W panel that still fits on the shed and use that. Since those are generally "24V" panels, I'll get a buck converter if I get one of those panels.

 

[chrisski]

I tested this with the 100W suitcase panel and the 12V fan in bright sun. I measured 11-12V with the fan load and it ran similarly to being on the auto battery. I don't have a tachometer or cfm meter to quantify it though.

I'll probably look for a decently priced normal 200-300W panel that still fits on the shed and use that. Since those are generally "24V" panels, I'll get a buck converter if I get one of those panels.

Most “12 volt” panels are 16 - 22 volts. Labeled “12 volts” to let you know to put on a 12 volt PWM or suitable for a 1 volt MPPT SCC. If that were the case, I’d recommend a buck converter To take it to 12 -15 volts, whatever is needed.

You got the off panel that actually puts out 12 volts.