Solar Panel Layout?

It was suggested to me to use mounts that would raise the panels high enough so that shadows would not be an issue. Also, you do want some tilt to them to allow water to run off.

Sorry, I have no answers/comments about your post. However, I am very interested in the comments of others. I do have a couple of questions that I believe are relevant to your layout.

1) What type of controller are you going to use: PWM? MPPT?

2) How are you connecting your panels to the controller? In other words, what is the solar voltage going to the controller?

3) I have read about the shadow effect has on output performance but I have never seen it stated specifically for a design. Here is the chance for someone to address this issue for this design. Is the total system output less effected by monocrystalline panels when they are partially shadowed? How about when they are connected in series? How about when they are connected in parallel? Is a PWM controller better or not for handling shadows?

4) Knowing that there will be shadow issues for this setup, what would be the most beneficial selection of components: mono or poly crystalline panels? Series or parallel or series & parallel solar panel connection to the controller? PWM or MPPT controller?

5) Is it better to have the front of the panels tilted down to put wind pressure on the top of the panels when driving or vice versa? Is it even a design consideration?

I am looking forward to everyone's comments on this thread.

LeRoy

Allemac, with that many structures on the roof this is probably the best you can do.

As noted, you can lift panels a little, to reduce shading. I had to lift one of my panels by 4" co clear the plumbing vent (which was 3" tall). Lifting is easy, I did it with 4x4 aluminum angle:
4x4 aluminum angle. Ignore that it's tilted on the photo - I can tilt because it's a seasonal camp, but you don't have to.

Also, panels should NOT be flat. If you roof is flat (other than the front slope), then make the brackets on one side taller than on the other by an inch or two. There should be an angle about 4-6 degrees to shed water and dust.

If that flat/slope break in the front is steep, I wouldn't let the panel straddle the break. It just doesn't feel mechanically right. Though, if this will result in no more than 4-6 degrees panel tilt and no more than a few inches difference in brackets height, then you can.

With this layout the airconditioner will cause shading often, which means you should wire panels in parallel, which in turn means a substantial cable.

mena661 wrote:
It was suggested to me to use mounts that would raise the panels high enough so that shadows would not be an issue. Also, you do want some tilt to them to allow water to run off.

Hmmmm...meaning that panels mounted near an AC unit would have to be raised >14" above the roof height? That sounds scary to me. I have heard the tilt thing - will likely tilt outward on each side.

Homeless by Choice wrote:
I do have a couple of questions that I believe are relevant to your layout.

1) What type of controller are you going to use: PWM? MPPT?
I bought the MorningStar TriStar 60 Amp PWM controller as my (limited) understanding is that with low voltage panels you don't much "bang" from MPPT and you might as well just put your "buck" toward more panels.

2) How are you connecting your panels to the controller? In other words, what is the solar voltage going to the controller?
The panels will be wired in parallel to the CC. Therefore, shade will only affect the output of the one panel affected (series wired panels pass shade affects along). And these are 12V panels (see link in first post), so voltage will be 12V.

3) I have read about the shadow effect has on output performance but I have never seen it stated specifically for a design. Here is the chance for someone to address this issue for this design. Is the total system output less effected by monocrystalline panels when they are partially shadowed? How about when they are connected in series? How about when they are connected in parallel? Is a PWM controller better or not for handling shadows?
I don't know other than the parallel/series note in response to #2.

4) Knowing that there will be shadow issues for this setup, what would be the most beneficial selection of components: mono or poly crystalline panels? Series or parallel or series & parallel solar panel connection to the controller? PWM or MPPT controller?
Same answer as #3.

5) Is it better to have the front of the panels tilted down to put wind pressure on the top of the panels when driving or vice versa? Is it even a design consideration?
This is a question I have relative to if I mount my panels over the sloped area (or more accurately, straddling the flat/sloped area of my roof). I saw one comment on a thread where someone pointed out not to worry about it as the force of the wind pushing down on the panel was more that sufficient to counteract any lift generated by wind being forced up the slope.

I am looking forward to everyone's comments on this thread.
Me, too!! :)

alliemac9 wrote:

Hmmmm...meaning that panels mounted near an AC unit would have to be raised >14" above the roof height?

No. You WILL have shading from A/C unit, get over it. Which will be a big problem if you wire in series, but not so big problem if in parallel.

@Almot - thanks for giving me some quantified direction! A tilt of 4-6 degrees is much easier for me to work with than the general consensus to tilt for water/dust mitigation.

I don't have any great photos of the slope, but here are a couple...maybe it's insignificant?

Almot wrote:

alliemac9 wrote:

Hmmmm...meaning that panels mounted near an AC unit would have to be raised >14" above the roof height?

No. You WILL have shading from A/C unit, get over it. Which will be a big problem if you wire in series, but not so big problem if in parallel.

I see from the picture that his A/C unit is pretty tall. Mine is a lot shorter so I plan to raise them up to clear shadows.

Is the air conditioner a requirement?

@shooted - Yes. I have very fuzzy dogs (and a husband who likes climate control) so for the times when we are camping in less comfortable weather, we want to keep the AC.

We did a brutal (for us since we're used to a non-humid and moderate Colorado climate) trip to the SE/Midwest last summer to attend some family events. It would have been pretty awful without the AC. While we'd rather camp in comfortable temperatures, it's handy to have the flexibility in the RV to handle less ideal weather.

I wouldn't be concerned with the cab-over slope. Use it to your advantage and install one module at that fixed angle or modify the mounting to have less angle.

Shade is not your friend. Most larger modules have the internal diodes tied to a string of cells so if one cell in the string is shaded, you'll lose most of the power from that string. If partially shading a module means that you can install the required amount of modules, still, i'd just live with the shade.

Raising module height will eliminate a lot of the shade and shade duration. With the very compact nature of your layout, I'd be tempted to use rails and attach modules to those.

One of the best layout tools is to cut templates of your modules and position them where you intend to mount. It will uncover any layout discrepancies and you'll be able to plot shade issues.