My project folder has gotten unwieldy, so some things will show up here from there. The project folder (ok, it's now a shelf or two of bookcase) started when I realized that I had far more ideas than time to complete them. So I started making notes on the ideas so that at least I wouldn't forget what they were. But I'd also clear the brain a little to have room for new ideas. Some of those ideas have been published in the scientific literature, and some have sat quietly for upwards of 20 years.
A different sort of 'project' that will show up is where I'll suggest that you try something, or challenge you to answer something. In the former case, I probably know the answer and give some fair pointers to how to finish it. In the latter, I may not have the answer either; but it is a good question to have one for. Maybe some would be publishable in the scientific literature.
Probably a number of these will lend themselves to science fair projects.
Where I mention a project in a science note (like, say, the simplest meaningful climate model note) it may well also be that I don't expect you to take my word for things. If I'm talking science, you can do things yourself and come up with the same answer. I think it's a good thing to take the time and wrestle some with the guts of a problem. You'll understand a lot more that way (certainly I do). Plus, maybe I made a mistake and you can be the one to point it out. (In science this is normal and welcome. But you do have to provide more than 'ha ha, you're sooo wrong'.)