Solar Impulse is an airplane powered by the sun. It provides a window for the technologies of the future, but already under development are solar cells offering a better efficiency-weight ratio, intelligent systems of energy management, materials as lightweight as they are resistant and a storage system to rival the most efficient. On earth at midday, each m2 of land surface receives the equivalent of 1000 Watts, or 1.3 horsepower of light power. Over 24 hours, this averages out to 250W/m2. With 200m2 of photovoltaic cells and a 12 percent total efficiency of the propulsion chain, the Solar Impulse airplane’s motors achieve no more than 8 HP or 6kW – roughly the amount of power the Wright brothers had a available to them in 1903 when they made their first powered flight. And it is with that small amount of energy, optimized from the solar panels to the propeller, that Solar Impulse is striving to fly day and night without fuel! Someday, the solutions developed for the solar airplane could find other applications in the building industry where efficiency and reliability are determining factors.
