Your solar panel is likely extremely lightweight, and I can see any issues with attaching it to the wall. If you are worried about the screws pulling out of the wall, you can use spring toggles for extra grip.
I'd recommend you apply some sealant to any holes in the wall and the mounting base for the solar panel. This will ensure that no water can enter the wall through your holes.
It looks like you'll be working at heights for this project, so I suggest you have a quick read of this article on How to use ladders safely.