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.
Burning wood comes with its own extra work and costs. Plus the danger of burning your house down. I live in a forest, and wood heat is not uncommon here. There were 4 wood heat fires that destroyed homes this past winter, it was a cold and long winter this year. And I did grow up with wood heat as a kid, so I'm very familiar with it. I do remember a couple of chimney fires quite well.