Epoxy is very tough. Easily stronger and more durable than any original glass (it would not shatter). It is commonly used on floors, and with even a thin layer properly applied it is stronger in many ways than wood. I've used it to reinforce compromised ply by diluting it with xylene and letting it soak into the ply.. Concerning a RV roof mounted solar panel, really your only concern is that the whole "sheet" of epoxy doesn't somehow separate from the frame. Although this is unlikely, it is the only difference between the epoxy sheet and the glass sheet. The epoxy sheet if it somehow broke away would likely do so in a solid sheet, whereas any glass would likely shatter. I'm not sure how big the panel is, but if you're looking at making a quick repair job to an existing glass panel that is shattered but still functioning.. I guess you could.. paint it on thick and run some sort of support straps across the panel every so inches, embed the straps in between the first and second layers of epoxy.. won't go anywhere. If you're looking at removing the existing glass and "pouring" a new layer of clear epoxy, that's what I would recommend as you won't get glass chips shifting around cutting up your solar works.
For that: remove the frame, remove the glass, build up the edges with painters tape, pour a reasonable amount of epoxy in the center of your panel, and spread it out to a thick coat using a chip brush. If you're going to apply a second coat, you wait about 8 to 16 hours (on a medium speed epoxy, recommended) and then you apply the second coat. The first coat should be set up, but still a little tacky, this way they will bond together. You want it all bonded, and the only other way to make a second coat bond to a 1st that's dry is to sand the 1st. After you're applied, I guess you put your frame back on and I guess you're good to go, make sure your frame is snug against the epoxy, but that's a sheet of hardened glue.. not going anywhere. Good UV properties too iirc.
As for sourcing your epoxy, there's a place called ill street composites. That's what we've used. Excellent epoxy.
Word of advise. For a single solar panel you likely need no more than a quart..
When you're mixing your resin and hardener.. do NOT add more hardener than resin.. If you are going to err.. err on the +resin side. If you add even a little bit too much hardener, or you don't properly mix it, that stuff can start superheating, SMOKING and hardening in minutes into a globby mess. The process works on compounding heat so you want it to have surface area while it cures. don't leave cups of the mixed stuff lying around.
I know people put glass panels on rv's, but the ones on mine have a plastic..plexiglass sort of material. I'm comfortable with that, and I would be just as comfortable with epoxy, but far less comfortable with glass, fyi.