Inside the main cabin of MS Tûranor PlanetSolar, the first boat to travel around the world on sunlight alone, Christian Ochsenbein opens a trapdoor hidden beneath a seat cushion and crawls inside. He climbs down a dark tube and squats inside a long, narrow chamber—one of two pontoons keeping the catamaran afloat.

“We are now inside the ‘engine’ room,” he jokes. This being a solar-powered boat, there is no real engine to see. He points out the propeller shaft, driven by AC motors, and at the opposite end, a vault that houses solar-charged batteries. He can’t show them off up close, he says, because they contain top-secret German submarine technology. [Read More]