How to get maximum solar power for minimum price?

[HiTech]

So what are the right steps to go through to get the maximum solar watts on the roof of a real world RV (with all it's unusual sized spaces) for the minimum expenditure in panels?

The method below does not do it (and it also totally ignores shadows, not a good idea), but it seems like a start:

Start in the largest open area, and find the highest efficiency panels you can that fit in the open spaces on your roof. Block off the area they take up from consideration. Repeat with the remaining space on the roof. Stop when no space remains or you get to a panel size that is too small to be interesting to you.

This is a rough approximation of maximum watts you can get on the roof, though it is possible there are better sequences than largest space first to optimize total watts one the roof.

Now cost optimize and possibly even increase wattage by covering more of the empty space:

For each panel proposed following the method above, look at it and the remaining wasted space around it, and consider panels of lesser efficiency but equal or better wattage in the space of the panel plus unused space around it. Pick the cheapest panel that fits this larger spot that is the same or greater total watts as the panel it replaces.

What is a better approach to filling an RV roof with the maximum watts of solar for the least $?

Jim

[Almot]

There is no prescription one for all. Available space is the space that is at least 1ft away from any superstructures on the roof, sometimes 1.5ft. So if you have 9ft from airconditioner to front bedroom vent, you in fact have 6 ft available for panels. If any tilt is planned, it becomes yet more complicated. You want enough clearance between the panels to avoid shading. With big titled panels, say over 200W, it is preferable that tapping screws in legs hit the roof rafters, because large panel will cause a lot of wind-induced stress.

[2oldman]

plascell wrote:
So is there still room to walk on the roof to reach and repair any vents, etc.?

Yeah, you gotta do that. I have six and I have to be really careful where I walk.

Having many panels can also increase roof life by their shading.

[HiTech]

Thinking just about max nominal watts of solar panels flat mounted, I imagine picking the highest efficiency is going to push you into mono or hybrid. There are some really high efficiency panels out there now but getting ahold of them in low quantity is nearly impossible.

In particular though I am pretty sure max watts flat on the roof does not always equal max efficiency panels. They make a great benchmark though, and sometimes they end up being the most watts produced to fit a certain dimension space.

All the other items like maintainability, shadow, actually getting the watts OUT of a mix of panels...etc. are all important, but dont really affect the proposed method for maxing out a space on watts.

I'm sure there is a better way - I just have not come up with it.

Jim

[Ski_Pro_3]

There's a couple things you might do to max the solar collection;
The type of controller.

Mounting the panels above roof for air circulation due to the efficiency of panels relative to heat.

Mounting panels above roof high enough to circumvent shadows from other things mounted up there, like the AC.

Ability to angle panels to face the sun, or even better, track the sun.

Removable panels w/extension wire to place panels in sun when RV is in shade.

Mount panels to side of RV w/ability to adjust angles. This saves roof space at the expense of parking angle/position to maximize sun exposure.

Mono panels as opposed to poly crystalline panels to maximize amperage-to-panel size.

[plascell]

So is there still room to walk on the roof to reach and repair any vents, etc.?

[EsoxLucius]

You can place panels to take up all of the "open spaces" on the roof. But they should be at least as far away from other objects on the roof as those objects are tall. And if you are using different size panels they should all have similar output.