Camping in the clouds

Low-tech Magazine: Camping in the clouds: the Aeromodeller II:

"The zeppelin inverts its propellers, which then serve as windmills. They deliver the necessary energy to split water (coming from the ballast tanks and replenished by rain) into hydrogen and oxygen. Six hours of wind energy accumulate enough fuel for one hour of flying.

This means that the airship has to “rest” regularly to charge its “batteries” – just like a living creature."