I don’t have time to review all of this, but I’m glad you’ve written it all out! You should make sure to bookmark or otherwise save this link to your comment, so that you can access this text in case you want to explain the idea to anyone else.
In my role, I see lots of people propose very big ideas. Things to keep in mind about these:
The more things need to go right for an idea to work, the less likely it is to work. Consider which elements of your plans are flexible, and be ready to adjust them. This especially applies to working with relatively inflexible entities like local governments.
If you aren’t an expert on a topic, you may have a hard time doing really good research on it. Talking to an expert can teach you things you’d have had a hard time learning on your own. Before you spend a lot of time, or any money, on this idea, you should do your best to talk to someone who works in the solar industry (if you don’t work there yourself—sorry, don’t recall). They may have a simple objection that neither of us ever would have considered.
I can’t emphasize enough that large utility companies are already tracking people down and offering them electricity discounts in exchange for installing solar. Society doesn’t always discover sources of “free money” (like “houses that get a lot of sunlight”), but if you think you’ve found a new way to generate easy investment income, you should assume until proven otherwise that someone else has already taken that opportunity. Maybe the utility companies haven’t expanded to all the places they could reach, or maybe the charity could afford to target certain customers that a company couldn’t—but you need to very certain this is true.