I'm only half kidding. I'm a bit of a prepper and I have lots of powerbanks and devices that charge from USB but besides idling my truck I really had no other way to charge any of them in case of a long-term power outage which seemed a bit of an oversight on my part.
Not like this solves the issue. 30 watts (under ideal conditions) isn't much but it's a start.
For heating, I've been wanting to try a solar collector. Not sure if you've come across Greenhill Forge on YouTube or anywhere that covers his projects, but he does all sorts of off-grid stuff.
https://www.youtube.com/watch?v=8cPuVZjnbi4
That's where he builds and tests several different styles of solar collectors for solar heating. The collectors are pretty inexpensive to build so that may be an option if you just want to (help) keep a shed warm.