The Solar Impulse team is preparing to tackle one of solar power’s biggest challenges: night.
The team has a goal of flying around the globe without using a drop of fossil fuel. That means the solar panels on the aircraft must gather and store enough energy during the day to propel the aircraft through the night.
The Solar Impulse prototype, which has a 208-foot wingspan and weighs a little more than 3,500 pounds, made its first flight April 7. Propelled by four 10-hp electric engines, it gathers energy from solar cells on the wings and horizontal stabilizer and flies at an average speed of 38 knots.
Early this month, the prototype flew for four hours and 50 minutes, its longest flight thus far. The team reported that this was the aircraft’s first energy-positive flight. “This means, as Claude Nicollier stated, that ‘we came back with significant more energy than we took off with,’” wrote Martin Reichlin in a blog.