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.
are generally used to charge a power bank for phones, lights, and such.
That's exactly the use case I bought it for. In the picture I'm charging a powerbank. I'm intending to play around with a small-scale solar setup on my shed at some point but for now this is the one cheap investment that enables me to keep critical small electronics running indefinitely.