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.
I've kept the old wood stoves in my house just in case I ever need them. I used them all last winter cause they were all I had at the time. Learned how to chop wood and start a fire and everything. It was kinda fun, but hard work. Defo not something anyone should have to do their whole life, but perhaps something everyone should try once. Quite humbling
EDIT: I used them for heating. Had to keep a fire going about 3 hours a day in each