Hey OP, it sounds like there is some interest and maybe even a worthwhile community here. My advice is to not reinvent anything special here. What about transforming it into a forum? Every thread with a different project, with different categories.
Doesn't have to be a forum, but something that you don't have to spend/waste time to make and can still be useful to everybody :)
I'm not entirely sure. What about a subreddit? There are already some similar things (not about solar), e.g. https://www.reddit.com/r/DIY/ and it seems to work out pretty well for them. I expect most of the HN crowd (or the relevant people, anyway, who might not be on HN) are familiar with reddit already and similar subreddits (/r/electronics, /r/hardware, /r/raspberry_pi, etc.). Simple upvote system, and comments already baked in.
Doesn't have to be a forum, but something that you don't have to spend/waste time to make and can still be useful to everybody :)