OK for solar panel overhang edge of RV roof?

[Visionquest2]

I want to add a second solar panel to my RV roof in such a way that I can travel with it flat and tilt it while in storage during winter months. The rear of my RV faces almost due south while in its outdoor storage space. By mounting the panel at the rear of the RV with a slight bit of overhang I expect snow to fall right off on to the ground 12 feet below. The tilt will also optimize the winter solar performance. During our travels (March through Oct) performance will be best by leaving it flat as well as I won't want to drive with the leading edge of the panel catching air!



My other factor is the rear AC unit which will not allow the panel to sit fully flat on the roof. It will have to overhang the rear edge of the roof by about 6-8". (panel is 200w approx 5' x 2'). See attached graphic.


I'm looking for input on whether this overhang would be acceptable. I would plan buy or fabricate the rail mounting such that the mounting is cantilevered off the roof, giving the trailing edge of the panel full support.


Thanks in advance for your input.

[Ray,IN]

At first I was thinking a side overhang, which would be the first thing a tree limb would contact; then you diagram shows rear of RV overhang, for which I can forsee no negative connotations.
It's your money, use it any way you choose. That sounds like a reasonable plan.

[Unplanned Tourist]

I think I would just put the second panel ahead of the AC unit. Your batteries will be just fine if you park it with a full charge and the disconnect the negative leads.

I like the KISS principle.

[rarebear.nm]

I have three commercial sized 350 watt panels on my 5th wheeler. The rear panel overhangs the rear by about 3". No issues. I wired these 44 volt panels in parallel and never experience any significant shading issues. Partially because of the quality of the panels themselves.

[Mudfrog]

Only thing that would be a bit of a concern to me is the proximity of the tilted panel to the a/c. Shouldn't be a problem the majority of the time but it could impede condenser air flow efficiency it it were too close. Maybe even if laying flat.

[Visionquest2]

I would place the panel in front of the A/C unit except that I would like the benefit of easy snow removal. My batteries stay connected year round with a remote monitoring system so disconnecting batteries is not in the plan. With the existing (flat) panel, even near the edge, snow removal was problematic this past winter. A tilted panel with nothing under it to keep snow from simply sliding off would be far easier to maintain through the winter months.

[Visionquest2]

Originally Posted by Mudfrog

Only thing that would be a bit of a concern to me is the proximity of the tilted panel to the a/c. Shouldn't be a problem the majority of the time but it could impede condenser air flow efficiency it it were too close. Maybe even if laying flat.

Yes, I agree and will evaluate that further. The panel will likely lay flat enough to not affect the A/C but I'll need to determine if the A/C will pump too much hot air at the panel. Thanks for the thought.

[n0mad]

We crammed a pallet of used panels + a bunch of additional panels onto the roof of my friend's 38' motorhome a while back. 5020W if I recall correctly, and they're not the most efficient panels so they require more lot of real estate than a more modern panel (the price was right). They hang slightly over the sides and quite far over the back and have done so for many, many thousands of problem free miles.

Side note, second photo shows 13,850W on three RVs (my rig on the lower right).

[Visionquest2]

Mindblowing!

[Ray,IN]

Originally Posted by n0mad

Attachment 419235
Attachment 419236

We crammed a pallet of used panels + a bunch of additional panels onto the roof of my friend's 38' motorhome a while back. 5020W if I recall correctly, and they're not the most efficient panels so they require more lot of real estate than a more modern panel (the price was right). They hang slightly over the sides and quite far over the back and have done so for many, many thousands of problem free miles.

Side note, second photo shows 13,850W on three RVs (my rig on the lower right).

Where were the plumbing vents relocated?

[rarebear.nm]

Originally Posted by Ray,IN

Where were the plumbing vents relocated?

It is clear in the first image that a custom mounting system was used to raise the panels above all roof top objects. On my own rig I built my own Z brackets and ran the panels over the top of the plumbing vents. No issues in six years. That gave me 1050 watts in three panels.


Some of the new large panels produce 500+ watts per panel. In 2025 we should see commercial production of new light weight 3D Printer solar panels. They have been proven in limited production and production equipment is being scaled up. They will be able make panels in variable sizes and shapes. You might Google for 3D printed solar panels for details.

[n0mad]

Originally Posted by Ray,IN

Where were the plumbing vents relocated?

On that particular rig, the risers are 14" tall if I recall correctly. Plenty of room for the vents to function properly. That rig has a composting toilet, and the black tank retasked as an additional grey tank.

[Ray,IN]

How about that! I would've thought air would get under the panels at highway speeds and cause them to act like sails.
Pretty neat.

[n0mad]

Originally Posted by Ray,IN

How about that! I would've thought air would get under the panels at highway speeds and cause them to act like sails.
Pretty neat.

I've installed panels in 30mph sustained winds and once they get anywhere near horizontal, the wind has negligible impact. You can hold one over your head in those wind speeds and not be moved any more than you'd move without one. They're large, but don't have the right shape to generate any significant lift. I'm not an expert in fluid dynamics, but those are my anecdotal observations. I know of several dozen rigs with similar racks and cumulatively they must have hundreds of thousands of miles on them if not more.

Going up and over is the best way to go for many reasons if building a large system.