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.
A standard E-Book can store the entire Wikipedia, OSM DB, Wikisource and Wikibook contents on a single $4 128 GB (~1 million books) SD card, also having a good IPX8 waterproof class.