Essentially, the idea is to turn the hatch cover into a solar collector. Out of the way and always on.
Howard
I guess I'm feeling chatty lately :-) I'll just toss in a comment about the hatch cover location (assuming you mean the companionway hatch), which is to not forget that many panels don't work if they're partially shaded (depends on the type). I've cruised on two different boats, both of which had one solar panel. On the first boat it was mounted simply to the stern rail, and was almost always in the sun and working - albeit not as well as it might have if we'd rotated it or something, but pretty darned well. On the second the panel was mounted to the top of the dodger. Aesthetically, this was great as it didn't really show, and functionally it was out of the way. But so many times it didn't give us any charging even when the sun was out! Sailing, the boom or sail would nearly always shade it; at anchor we'd have to pull the main boom way out to one side and even then if the boat swung it would be shaded. You'd also have to step over the vang/preventer tackle that was holding it over if you happened to be going forward on that side. It was easy to pick out our boat in a crowded anchorage though, with that big chicken wing sticking out to one side :-) If I were mounting a panel (unless it were the flexible type that doesn't get bothered as much by shading - and if I had that kind I'd probably keep it portable - strap it to top of sailcover at anchor, etc.), I probably wouldn't choose the hatch cover/dodger top again, FWIW. --- Rachel