Should solar panels be level?

Jacksonricher · Aug 28, 2018

I am mounting my panels on my high top roof, should I mount them as level as possible? I am thinking a slight angle for rain run off.

Is the top glass so it is easier to clean or another material?

Van-Tramp · Aug 28, 2018

Mount them so excess air will not get under them while driving. A 60 MPH wind while you are driving will rip panels off your roof if you are not careful

A slight angle is fine, and will make it easier to clean. Just a degree or two angle is fine.

Canine · Aug 28, 2018

It's up to you if you want them level. Yes, it will make keeping them clean a bit easier, but if the panels are tilted away from the sun, you will get less power. Depends on how much power you want to lose. If it's winter, that's a bad deal. Summer it would be fine.

Rigid panels are glass- very tough, expensive glass. The flexible ones are plastic.

MrNoodly · Aug 28, 2018

Van-Tramp said:
Mount them so excess air will not get under them while driving.

However, it's best to have some bit of air gap between the panel and the roof so the panel doesn't overheat.

Jacksonricher · Aug 28, 2018

Can you just put a air damn thing like on the front of the hood to push the air up and over the panel?
Raise the panel maybe an inch with the damn in the front, open on the three other sides.

Dingfelder · Aug 28, 2018

I've always admired the builds that let you tilt panels to different angles to catch the sun. If you had that, you could install flat but tilt at your discretion.

Canine · Aug 28, 2018

An air dam would be perfect.

jimindenver · Aug 28, 2018

Just enough of a tilt to allow the rain to run off is best. If it sits the dust will settle.

MrNoodly · Aug 28, 2018

My big 270W panel sits 4 inches above the roof, no deflector (unless you count the windshield) and it is still there after five years. In fact, back in the days when I had it set up to tilt, I accidentally drove 22 miles at 70mph with it up. No problem except feeling stupid.

QinReno · Aug 28, 2018

I'm the least expert person here in regards solar, but sites I've seen indicate the tilt angle for best output is:
"Take your latitude and add 15 degrees for the winter, or subtract 15 degrees for the summer". But you'll notice there are also a couple of other formulas too.
https://www.solarpoweristhefuture.com/how-to-figure-correct-angle-for-solar-panels.shtml

So first-cut, Phoenix for instance would be 33+15=48 for winter, 33-15=18 for summer. Yes/no/maybe?

Jacksonricher · Aug 29, 2018

Thank you but I am not going to be changing the tilt, once they are up there they ain't moving. I think I will have a little angle for rain and dust and eaz of washing. And have about an inch under the panels, anchored really well with a custom made air damn in front and maybe a medium width LED light bar.
At least that is my thought right now, subject to change at any given time lol.

QinReno · Aug 29, 2018

I assume that, if the panel is at 0-deg when it should better be at 45-deg, then you'll be getting roughly 50% output at best. OTOH, since it's in your roof, it'll be charging all day long so that'll probably compensate.

A couple of other things to consider. In the heat of summer, you will want to be in the shade but your panels will need to be in the sun, so you can't go park under a nice shade tree. Also, with monocrystalline panels, which is what most people will swear by, all you need is for one small part of the panel to be in the shade and the output power will sink like a rock.

MrNoodly · Aug 29, 2018

QinReno said:
I'm the least expert person here in regards solar, but sites I've seen indicate the tilt angle for best output is:
"Take your latitude and add 15 degrees for the winter, or subtract 15 degrees for the summer". But you'll notice there are also a couple of other formulas too.
https://www.solarpoweristhefuture.com/how-to-figure-correct-angle-for-solar-panels.shtml

So first-cut, Phoenix for instance would be 33+15=48 for winter, 33-15=18 for summer. Yes/no/maybe?

I think if a few degrees of tilt makes a significant difference, then there's not enough panel. Besides, the sun shifts 15° east to west each hour (or, more correctly, the earth rotates), so unless you have your panel(s) mounted with automatic tracking, you'd need to keep reorienting the van.

I used to tilt mine, but it meant I always needed to face my van the same way, whether the campsite was conducive to it or not. There were winters I would reorient the van three or four times during the day. In addition, the tilting-untilting routine was a little annoying. So I quit bothering to tilt the panel and discovered things worked out just fine. So I got rid of the hinges and prop rods and latches and just bolted the panel to the rack.

Spaceman Spiff · Aug 29, 2018

I have a 3º tilt on my panels (1 inch higher in back than front). I have not seen a loss of output from that arraignment. I does make it slightly easier for heat to escape from under the panels.

As for wind faring in front of the panels: unless they are on the leading edge of the roof the slope of the windshield will push the air over the top of the panels. I get lots of bugs on my windshield but none on the leading edge of the panels 12 inches back from the ws.

Like MrNoodly, the few people I know that have had tilting panels on their roof have given up tilting as a bother.

I camp under forest canopy a lot, so for that and multiple cloudy days I carry a small generator. Run the generator in the AM to 80% battery an let the solar finish the job.

jimindenver · Aug 29, 2018

The OP is asking for a none moving mount in which case you do not want water standing on the panels. There is a inch difference between the front and back of my panels. Being able to tilt those on the trailers roof would greatly increase the mid day haul during the winter but it would also sacrifice some of the shoulder light. Having the big panel on the truck tilt as I move it throughout the day really helps but I only do that in the winter.

QinReno · Aug 29, 2018

MrNoodly said:
I think if a few degrees of tilt makes a significant difference, then there's not enough panel. Besides, the sun shifts 15° east to west each hour (or, more correctly, the earth rotates), so unless you have your panel(s) mounted with automatic tracking, you'd need to keep reorienting the van.

I imagine a few degrees won't matter much, but the difference in power output between being flat and being 48-degrees must be significant. Anyone know the percent output power change versus angle to the sun?

QinReno · Aug 29, 2018

QinReno said:
In the heat of summer, you will want to be in the shade but your panels will need to be in the sun, so you can't go park under a nice shade tree.

I see this as being kind of a self-fulfilling dilemma. Vicious circle.

To keep your batteries charged, you need to park in the sun. When you park in the sun in the summer, then the RV/van gets extremely hot, and now you need an air conditioner. But to run an air conditioner, now you need another 400-500W of solar and even more batteries, so another $1500 more. Now you have a ton of money in batteries plus panels mounted all over the place, and a huge weight in batteries just so you can stay cool when you park in the sun in the summer.

I think if I ever go the route with 400-500W of solar, it'll be on a cargo trailer I pull behind the van. Then I can park the trailer in the sun and the van in the shade.

Jacksonricher · Aug 29, 2018

QnReno, funny you say that because I was looking at trailers last night thinking the same thing.

MrNoodly · Aug 29, 2018

At one time I thought about a power module trailer. Get a trailer like the smallest U-Haul, the ones that aren't much bigger than a washing machine. Put some vents and outlets on the side, load it with batteries, the charge controller, meter, inverter, fuse panel and such. There might even be room for a generator and fuel. Mount a solar panel on the top as well as some that swing up from the sides and front that could be angled to the sun.

<img src="https://image.ibb.co/ncrGA9/tinytrailer.jpg" alt="tinytrailer" border="0" />

QinReno · Aug 29, 2018

Mr N, that might be a nice solution for people with vans, small trailer with just electrics in it and a bit of extra storage space. Run a 0-gauge wire over to your van that's sitting in the shade. Cool.

EDIT: Have to measure the area. Putting solar panels on the sides mounted on hinges is a good option. What is that, a 4'x6' size? You may have invented my dream solution. Cool.

Assuming the door is fold down, then clever boy might even put the solar panels on sliding racks that could be stored inside, but slid outside for deployment.

Should solar panels be level?

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