Adjustable tilt vs solid mount array for solar trailer build

OM617YOTA

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Building my first system, a solar trailer. I'm using 4x 410w bifacial panels, and am located at almost exactly 45deg latitude here in the pacific northwest of the USA. Would it be worth building adjustable tilt into the solar array? I had planned to just mount the panels on a 45 deg angle to match the latitude, and "aim" them by moving the trailer. It would be more trouble, but I could also build the frame to have adjustable tilt. Even have two separate arrays of two panels each, each with individually adjustable tilt, and each array feeding a separate MPPT.

I'm strongly leaning towards the solid 45 deg mount. My thoughts are:

1. It's easy.
2. In the summer, these panels will completely take care of 24 hours worth of energy needs in around 2 hours of full sun. Exact tilt won't be a huge factor.
3. In the winter, in Oregon, full sun is a fleeting thing, and my thought is that the more unfocused light means direct aiming is more important. No clue if that's reality or not. Flip side of that, getting the most of any sun that does peek out could be VERY important.

Please share your experience and thoughts. Thank you all.
 

FrederikSchack

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Hi,

I think you might want to look at this angle calculator, because it depends on when you want to optimize the sun for:

As far as I can se it gives a very good suggestion.

Notice that the angle you get is calculated relative to a vertical surface and not a horizontal surface. If you want to convert it to a horizontal surface, then you just subtract the calculated angle from 90 degrees. So if you get 41 degrees, it´s 90-41 = 49.
 

FrederikSchack

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Another thing I considered is that we rarely get golf ball sized hail where I live, so wouldn't like to lay them down flat. Anyway I want to optimize for winter sun, so where I live 49 degrees relative to horizontal is optimal and if I don't get to cover the panels before the hail, they'll sort of go at the panel at a steep angle, instead of straight on.
 

OM617YOTA

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Thank you, all.

Using the calculator Frederik shared, I can see why 45 deg, or roughly one's latitude, is considered "optimal" for year round performance in a fixed installation, but there's enough variant between the seasons that an adjustable mount seems worth seriously looking into. I do have sometime, as my batteries are yet a ways out. Thank you, Frederik.

No significant snow here, and no significant hail. Pea size, at most. Although with the weather going nutso lately, who knows what the future will bring. The inspiration for this build was an ice storm, which caused a six day power outage. Gasoline was difficult to find in a couple instances.

Thanks again, all.
 

FrederikSchack

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Thank you, all.

Using the calculator Frederik shared, I can see why 45 deg, or roughly one's latitude, is considered "optimal" for year round performance in a fixed installation, but there's enough variant between the seasons that an adjustable mount seems worth seriously looking into. I do have sometime, as my batteries are yet a ways out. Thank you, Frederik.

No significant snow here, and no significant hail. Pea size, at most. Although with the weather going nutso lately, who knows what the future will bring. The inspiration for this build was an ice storm, which caused a six day power outage. Gasoline was difficult to find in a couple instances.

Thanks again, all.
Yes, even if you found the optimal angle according to your preference, you might change your preference later and then it´s no fun to invest in a new support for the panels.

The drawback to your particular situation could be driving on a bumpy road with a flexible mount, it would have to be fairly sturdy. I would make sure that the panels can´t flex too much, of course depending on the panel type. But I´m sure you´ll find at good solution.
 

12VoltInstalls

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20-25* from vertical would be an ok year-round position because it is more likely to deflect golf balls from the driving rain - and is closer to the winter optimum.

I've been running vertically mounted for like 9 months now. Not ideal but is apparently making enough power to keep things going. Bonus and original intent: no snow buildup in winter.
I’ve stopped worrying about ultimate efficiency and instead just went for “enough” with extra panels which it seems I haven’t needed.
 

FrederikSchack

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20-25* from vertical would be an ok year-round position because it is more likely to deflect golf balls from the driving rain - and is closer to the winter optimum.

I've been running vertically mounted for like 9 months now. Not ideal but is apparently making enough power to keep things going. Bonus and original intent: no snow buildup in winter.
I’ve stopped worrying about ultimate efficiency and instead just went for “enough” with extra panels which it seems I haven’t needed.
When you get above about 45 degrees relative to horizontal, you stop winning energy in the wintertime with increased angle, but are loosing heavily in the summertime. I´ve made some calculations, but they are particular to my location.
 

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12VoltInstalls

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winning energy in the wintertime with increased angle, but are loosing heavily in the summertime
True, yes, I alluded to that.
I’m making enough in my case.

Not to minimize the summertime “loss” but I’m 100% charged in the AM of every sunny day so in that situation the last available watt is not a concern for me.
 

OM617YOTA

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I'm definitely interested in more practical solutions. The goal here isn't to pull every last watt out of the system, just enough to meet system specs. It may turn out that I never actually need to adjust the tilt, once the system is up and running.

The drawback to your particular situation could be driving on a bumpy road with a flexible mount, it would have to be fairly sturdy. I would make sure that the panels can´t flex too much, of course depending on the panel type. But I´m sure you´ll find at good solution.

The reason for trailer mounting was mostly to be able to move it around the property without much trouble. It was never meant to actually be road going. It's a cheesy Harbor Freight trailer anyway, so even without the 7' x 12' solar sail mounted on the top, it's only a "trailer" in a limited sense of the word. When it gets moved farther than just across the street, the panels will be dismounted, and likely the electronics and even the batteries removed, just to save them all the road shocks and vibration.

With the sail effect in mind, plus the weight of the panels relatively high, I'll be adding serious ballast to the trailer in addition to the batteries and electronics. Possibly jacking legs as well, and almost certainly ground anchors. The more I think on this, the more I think I probably should have just built the trailer myself, from scratch, for the intended purpose. Might still do that.
 
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JRUD

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May 21, 2021
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Bifacials are different. (Sez Capt Obvious!) They like to be off the ground, near reflective surfaces and at an angle to let max light hit the back side. I would guess the value of adjusting the tilt would be less than for standard panels.
 
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