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'm gonna give this warning: I have a panel of that type but much larger. It's rated at ~200 watts. I've never seen it make more than 80. I don't think it's a great idea to make large, flexible solar panels, I bet something internal is cracked in it. It's...virtually impossible to handle gently. It has kick stands on 3 of its 4 panels and you CANNOT stop that one inner panel from twisting. So...I am going to avoid that style of panel if it's larger than, say, a book. OP's 30 watt panel is probably fine but if you're dealing in the hundreds of watts honestly my glass panels are easier to deal with.