Tilted solar panels vs more flat panels for off road use

[filippomasoni]

We all know tilting solar panels yield a better efficiency but is that worth it?

Looking for science data all I could gather is about 15% improvement, I'll leave you below some articles, maybe you can understand the math better than me:

Effect of tilt angle on the performance and electrical parameters of a PV module: Comparative indoor and outdoor experimental investigation

Photovoltaic (PV) system's performance is significantly affected by its orientation and tilt angle. Experimental investigation (indoor and outdoor) ha…

www.sciencedirect.com

Solar Array Tilt Angle and Energy Output

The effect of an array's tilt angle on solar PV energy output may be up to 20% compared to that of flat installations. A comparison of data in two US cities has been completed to exhibit the importance of a solar PV array's tilt angle. As a general rule of thumb, energy output can be optimized...

www.cedgreentech.com

How does the tilt angle and/or orientation of the PV panel affect system performance? | Photovoltaic Lighting | Lighting Answers | NLPIP

Optimum Tilt of Solar Panels

The ideal solution of a 2-axis tracker might give a theoretical 40% improvement but that's not feasible on a vehicle-mounted system.

A tilt system could be manual or with electric actuators, many different designs are possible, but even trying to achieve the best what's the real improvement we can get from the panels? I've seen videos that tested up to 32% but that's only when you have the sun perfectly perpendicular, during the day it will change position a lot and nobody will be able to move the vehicle 5-6 times a day to accommodate for the sun's position.

A tilt system has many downsides: it adds complexity, time to make, and money of course. It's one more point of failure. It will have a higher profile and higher aerodynamic drag on freeways resulting in more noise and fuel consumption. It's heavier and the weight up top is the worst on a vehicle, especially off-road, where we should try to have a lower center of gravity.

I've seen people create a tilt mechanism and support for flexible solar panels made of steel (on YouTube, where they probably got the panels for free) and I think it doesn't make sense, you'd be better of with rigid solar panels that already have a structure by themselves and build the tilt mechanism on those.

If the overall improvement is only 15% I think it's much better to cover the entire area available with flexible solar panels and have a very lightweight roof, but I would really like to know your opinions about it.

 

[chrisski]

I don’t think its worth it for a vehicle mounted system. I have it and don’t use it.

I don’t want to climb on my roof and spend an hour Adjusting six panels that have six screws each every time I stop. I did find in the late part of the year where the sun is low to the horizon my output was increased up to 40%, which is matched by what the site in my signature block tell me for improved efficiency in the later parts of the year. That same site shows me much less of an improvement in the summer months when the sun is directly overhead. Some of the winds I experienced would be shaking the RV and I did not want my panels extended During those.

I only tilted my panels once. That was my first trip. After that the novelty wore off.

I do put out portable panels and adjust those throughout the day if my roof panels are not giving enough power.

 

[pollenface]

Mine sits flat on a forward hinging mechanism.

When I load up the roof rack, the panel gets tilted forward. I'm not really fussed about best angle, it's just a little bit of bonus power at the right time of day. If you were really fussed about the orientation you'd do better with a solar blanket or folding panel kit and move it around as the sun moves.

 

[filippomasoni]

I don’t think its worth it for a vehicle mounted system. I have it and don’t use it.

I don’t want to climb on my roof and spend an hour Adjusting six panels that have six screws each every time I stop. I did find in the late part of the year where the sun is low to the horizon my output was increased up to 40%, which is matched by what the site in my signature block tell me for improved efficiency in the later parts of the year. That same site shows me much less of an improvement in the summer months when the sun is directly overhead. Some of the winds I experienced would be shaking the RV and I did not want my panels extended During those.

I only tilted my panels once. That was my first trip. After that the novelty wore off.

I do put out portable panels and adjust those throughout the day if my roof panels are not giving enough power.

Lots of very good information in you signature, thanks for that. I can't find what you mentioned about the improved efficiency of tilted panels, but it makes sense, when the sun will stay at a low angle for the best part of the day (winter) it will make sense to have them tilted.

Like you said a manual system will be too much of a hustle and never be used. Also if it suddenly gets windy or starts to rain I can't climb up there to adjust them. So if I'm considering a tilting it has to be operated by electric actuators, which makes the system way more complex, and I can't figure out how much heavier and expensive.

Portable panels are not a bad idea, very flexible to use. Do you have a separated MPPT for those?

 

[Bubba1]

With portable ground panels you would adjust a few times a day.morning sun. Again at lunch and later after noon. Whenever it's convenient.

 

[filippomasoni]

With portable ground panels you would adjust a few times a day.morning sun. Again at lunch and later after noon. Whenever it's convenient.

Yeah, that's definitely easier than going up on the roof and having to turn the vehicle 3 times a day.

Would I need a separate MPPT for the portable panels? Would it be best to have an MC4 connector outside of the camper or just running a cable through a window for example?

 

[chrisski]

Portable panels are not a bad idea, very flexible to use. Do you have a separated MPPT for those?

I do have a separate SCC for the portable panels. I wanted to go 4P for my parallel panels which did not match the 3S2P of my roof panels.

I don't like the idea of running a cable through my windows. Mostly has to do with critters and bugs getting in or not being able to shut my windows to keep the heat in.

My batteries and SCCs are in my pass through storage, which by coincidence had a 2" hole I could easily rote a cable to. I just route my portable panels through a hole and hook them to a MC4 connector to the SCC al in the pass through storage.

 

[Short_Shot]

Tons of people flat mount and forget about it. They generally "overpanel" to some degree too where space allows.
Just gotta watch your shade from rooftop stuff and whatnot.

And it would be best to have a second charge controller for your portable panel to avoid issues with unmatched voltages and whatnot.
I rather like my suitcase panel, but I find myself worrying about whether someone will steal the thing when I am away. So far not an issue, but certainly possible.

 

[chrisski]

I rather like my suitcase panel, but I find myself worrying about whether someone will steal the thing when I am away.

I made cables from Home Depot to keep the panels from being taken. Where I really got use is dueing the winds that came out of nowhere kept those panels from blowing away. I found them face down, unharmed, kept in place by the cable locked to my RV.

 

[Short_Shot]

I made cables from Home Depot to keep the panels from being taken. Where I really got use is dueing the winds that came out of nowhere kept those panels from blowing away. I found them face down, unharmed, kept in place by the cable locked to my RV.

I did exactly the same, but it's really easy to cut virtually any cable.

Just look at how quick they cut the stuff you bought off the roll.

 

[Boondock Saint]

There's no such thing as "over panel"

I plan to just scooch my rig through the day to keep the sun directly to my back and off the sides of the rig, which will also help with shading from the A/C etc. I might even put panels ON the back wall vertically. And those I might could tilt up 45 degrees etc.

I really wanted to tilt my rooftop, but it's just not feasible at this time.

I'm running cable through mine not for theft prevention, but in case one were to ever fly off or start to come undone, at least it would have some anchor and not sail away into traffic.

Cables and padlocks keep semi honest and lazy people away.

MORE THIEVING - MORE DOING - THE POWER OF HOME DEPOT

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[Short_Shot]

There's no such thing as "over panel"

There is when you roast your charge controller.

But in the spirit of your statement, that's why I put it on quotes.

 

[chrisski]

I did exactly the same, but it's really easy to cut virtually any cable.

The four portable panels I have, I store in my trailer overnight or if I'm going away for hours, they also get put in the trailer. Otherwise, I leave them out. Other campsites around me are leaving out things people want much more than my panels, like coolers of beer.

 

[Short_Shot]

The four portable panels I have, I store in my trailer overnight or if I'm going away for hours, they also get put in the trailer. Otherwise, I leave them out. Other campsites around me are leaving out things people want much more than my panels, like coolers of beer.

Yeah usually it's not an issue at private camp grounds, a little more likely at a state park, and definitely likely at a festival or other event.

However, the neighbors leaving their stuff out does not absolve me of responsibility over my own stuff. So I lock up what I can and have a GPS tracker in my camper to boot.

If they're particularly inventive about stealing my panel even with a cable. Well. Sucks for me. But at least I put the attempt in and who knows, maybe it'll stop a few attempts before someone brings a cutter.

 

[filippomasoni]

The cable is a nice and simple solution that works probably 95% on the times, not only from stealers but also from the elements. So portable panels with a separate charge controller are something I'll definitely add in the future.

I've though of putting panels on the sides or on the back as well. From the design I have in mind now i won't have anything in that back, no windows nothing, so that could be a solution, and a much easier one to deploy manually as well. They will be mostly unused during driving and could be shaded in many situation, so probably not something I will spend money on from the start, but it's not a bad idea.
They will also need to be on a separate charge controller.
Is there any chance they could get damaged by rocks or dirt especially driving off-road? Dusty roads will render them unusable pretty much as soon as you go off pavement ? Are rigid panels stronger in this case?

 

[Short_Shot]

Dust isn't that much of a problem to be honest.

Definitely doesn't make them "unusable".

I had mine parked out by a gravel road the first time and after two days I cleaned it off and saw essentially no increase in output. Maybe a watt or 3 out of 150w total, but that's fairly normal fluctuation.

I suppose I might do it every few days just because but I'm not going to obsess about it.

 

[Boondock Saint]

Dirt and dust from tires on logging roads does swirl around the back of an RV. Once you get set up somewhere just use your Swiffer Duster. I would have mine on some pneumatic arms to raise at the bottom so I would have to get there anyways.

Btw - I have pretty much EVERY tilt product and video you can find on the subject bookmarked. Even solar tracking, I just can't invest the engineering for that right now. I have a scant 4 weeks to finish this project.


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[bobdelso]

The only tilt system worth using is one that you can reach from the ground or push a button. Tilting a 300watt panel ontop of a minivan, sure thats easy.

Climbing on top of a van/truck and trying to lift 4 panels, not so much.

I think a scizzor lift tilt system or some kind of automated jack would be the best

 

[chrisski]

The only tilt system worth using is one that you can reach from the ground or push a button. Tilting a 300watt panel ontop of a minivan, sure thats easy.

Climbing on top of a van/truck and trying to lift 4 panels, not so much.

I think a scizzor lift tilt system or some kind of automated jack would be the best

I've found every tilt system I've looked at to be pricey. Even more so for automated ones.

Looked at using gas struts like you do on a car trunk. That would be $15 per panel for six panels

https://www.amazon.com/Supports-Shocks-Spings-2005-2008-Chrysler/dp/B072KF3CPD/ref=sr_1_3?dchild=1&keywords=trunk+shock&qid=1627602729&sr=8-3

The ball locking quick release pins are $48 for a 10 pack and you need 12

Amazon.com

1/4" nuts, bolts, washers and spring washers could run another $50.

That is just the most practical system I saw. Never built it. I'm sure there's others. The scissor lift tilt system is something you'd need to fab on your own, but would b pricey. I've seen pre-built slide out and they're pricey also.

What I actually used was the Renogy Tilt mount system, which was $35 per panel:

https://www.amazon.com/Supports-Shocks-Spings-2005-2008-Chrysler/dp/B072KF3CPD/ref=sr_1_3?dchild=1&keywords=trunk+shock&qid=1627602729&sr=8-3

I looked at fabbing some myself, which looked like it was going to save money until I realized the the cost of pre-drilled angle aluminum, $50 for nuts bolts washers and lock washers, and wingnuts all added up pretty quickly. Maybe I could have saved some money. Ended up the Renogy tilt mounts I went with and the 2.5 foot angle aluminum was too flat to fit on my curved roof, so I ended up cutting that into shorter pieces to fit on the roof.

 

[12kw_2021]

I am planning on installing glass panels on my roof with a 23 degree tilt that is permanent. Two 200w panels on each side of the roof low edge near roof edge, high edge near center of roof. The high point of the installed panels will not be above the other roof installed items so the overall height of the rig is not increased.

I fully agree that having a variable system that requires climbing on roof to adjust is something that won't get utilized much.

I have also read that most of the flexible solar panels don't last long, and degrade over a much shorter time so I am sticking to narrow and long 200w full glass panels. The additional cost of two fixed "struts" that raise the interior edge of each panel is small, and they will connect to the typical feet that are 3m VHB taped to the roof. Just my approach..