Since it was a very small event, participants found it through word of mouth.
We'll announce the camp next year on this page. The event I linked at the bottom of the article is solpunk, a different german solarpunk event. The preferred language on both is English, AFAIK.
I agree! Especially here in the US. Solarpunk has gigantic potential in the Americas overall. I've got big travel plans next year I'm already saving up for but I'll definitely be finding my way to a convention somewhere in the relatively near future.