Brainstorming concept for mobile solar array

[yahastu]

Hello! I'm in the early process of brainstorming plans for a roof mounted mobile solar array as a DIY project. The host vehicle will be a 8.5'x20' cargo trailer. On the roof I can fit an array of 6x solar panels that is almost exactly 8.5x20. However, I actually want to create 3 such arrays, which will either fold out or roll out to the sides, so there will be a total of 18x panels when fully deployed (it will be about 10 kw). There are a few interesting engineering challenges here that I will outline below:

1) Reinforcing of the roof to handle the load. The weight of the panels and some minimal racking comes out to about 1000 lbs. To support this load I plan to reinforce it, probably using aluminum I-beams. If anyone has suggestions on the best way to frame out the support structure (from a theoretical structural perspective), I'd be happy to hear it, as well as any tips for how I might select I-beam size in order to achieve the necessary load bearing capacity.

2) The biggest question I am still pondering is the best way to store and deploy the panels. Each "super" panel will be basically 8.5x20 feet long, and will weigh approximately 350 lbs (including some minimal racking necessary to connect them). There are a few different configurations I'm considering:

a) I could mount 1 super panel on the roof, and 2 super panels on either side of the cargo trailer, attached by heavy duty hinges at the top edge. To deploy the side panels, I'd just have to lift them up 90 degrees and then fold out support legs. This would be the simplest to build, but I'm not a huge fan of this because the panels would cover any windows or doors on the side of the cargo trailer when done, in addition to attracting a lot of unwanted attention when hauling the trailer around.

b) I could have the two side panels fold out from the roof. This keeps my windows and doors unobstructed, but my main concern with this approach is the potential difficulty of deployment. I would have to climb up on a ladder to access the roof to unfold them, but with each super panel weighing about 350 lbs, it wouldn't be easy to life them up and fold them down. They could have legs that drop out from a gravity assist, so that would help, but lifting these panels up and gently opening them 180 degrees in a controlled manner would be difficult. Perhaps it would be possible to design some sort of pulley/winch system, although I don't have any specific idea of how that would look.

c) I could have the side panels on linear tracks that allow them to slide out horizontally from the roof. The advantage here is that they don't need to be physically lifted and rotated, so potentially easier to deploy given their large weight. It would be difficult to make them slide out from 100% overlap to 0% overlap, and one would need to be careful to deploy support legs before it gets to 0% overlap so there isn't too much stress put on the edge. I'm also not sure about options for a linear track that would be strong enough to support this weight, and not add excessive height.

Thanks for listening. I welcome any insights or ideas you might have!

 

[anorlunda]

That sounds like an interesting project. But it sounds to me that mounting them into super panels creates more problems than it is worth. I'm thinking of exactly the problems you said with weight and size.

Have you considered a lightweight frame that would allow you to remove the panels one at a time for storage, then collapse the frame?

Weather could be a factor. The wind forces on a 8x20 super panel during a storm could be very powerful. Have you considered that?If you do mount them into super panels, you many need leverage or power to manipulate them for storage. Perhaps something like hydraulic or pneumatic actuators. The engineering design for that is not trivial. What experience do you have in mechanical design?

 

[jrmichler]

If you not in a hurricane area, you can use a design wind load of 25 pounds per square foot to get started. In a hurricane area, use twice that. That wind load is trying to tear the panels off, push the trailer away, tip the trailer over, or even make it fly. You need to design for all of those cases. Keep in mind that the wind can come from any direction.

If you mount it to the roof of the trailer, you may also need to reinforce the walls. I strongly suggest that you calculate the height of the center of gravity before towing it.