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.
There are small devices for off-grid text communication based on radio frequencies. It's uses LoRa and it requires no Internet after setting up(you may need to download the app). Be aware that Line of sight is a bit factor and that buildings, tress and other stuff might affect it.
You can buy a device or build one on your own (you need to buy first chip and battery) and install/flash mesh on it.
Be careful though, do not get hyped from what you read or see, because in the end might not suit you. Here in Europe it has grown up a lot, lots of people use it, especially when traveling in another country l.
I just gave you a basic explanation, for more information visit the meshtastic community
https://mander.xyz/c/meshtastic
Meshtastic and meshcore websites https://meshtastic.org// https://meshcore.io/