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.
See that is where I find they ca get more useful. When you have a non emergency use for them as well.
I haven’t had a powercut for more than 5 minutes in my entire life. Have wondered if power at my allotment shed is worth setting up but not super keen on spending many hundreds/thousands it would take for any garden power tools and a generator would probably be a better option.
Lower power things might not be so bad. Though I really hate how modern powertools use proprietary batteries and each brand uses a different one. A powertool battery charger could be a modest size solar/battery setup.
I have a backyard shed that serves as a small but competent woodworking shop. It is connected to the house via a single 20A circuit. Running table saws, routers, planers, jointers plus lighting and dust collection can get to be a lot on one circuit, so I can haul the battery bank out there for more.
Just recharging power tool batteries and things like that, you could get away with a smaller unit. 1kWh or lower, with one, maybe 2 100W panels?