Solar power has been heralded as an alternative to petroleum-based fuels since Bell labs produced the first photovoltaic cell in 1954, but it has always had one very large obstacle – sunlight is not available at night. In recent years, solar, or photovoltaic, cells have been developed that can store energy more efficiently, making the power gathered during the day last well into the darkness of night.
One area where a switch from petroleum-based energy would greatly reduce dependence on oil while maintaining current levels of globalization is the airline industry. The first step towards realizing this potential is the Solar Impulse, the first solar-powered plane, which has proven its muster with an all day, all night test flight.
The craft is a prototype of a craft planned for an around the world flight in 2012. It is the result of Swiss and German money, engineering, and science. The propellered prototype has 12,000 solar cells that operate four electric engines, requiring no fuel and giving off no emissions. It has a wing span of 193-207 feet (depending on the source of the measurement), but is lighter than traditional aircrafts at only 3500 pounds. The craft is expected to be able to fly at nearly 28,000 feet and reach speeds of 70 km/h (44 miles per hour). On April 7, 2010, the craft made an 87 minute test flight (Reuters) over the Swiss countryside at an altitude of almost 4,000 feet. Its first flight was in December 2009, described as a “flea-hop”, flying 350 meters just 1 meter above the runway of a military base near Zurich. Both of these flights occurred during the day.
On July 7, 2010, the Solar Impulse made its first night flight (Reuters), which lasted for 26 hours, two hours longer than the pilots had hoped. The plane flew at more than 27,000 feet during the day, storing energy in its cells, and then dropped to 4500 feet for the night flying. Like the Wright Brothers, the Spirit of St. Louis, Amelia Earhart, and the numerous other airplane adventures that decry succumbing to obstacles that prevent humans from taking to the sky, the Solar Impulse has made its way into aviation history.
However, the developers do not see solar power replacing jet propulsion in the near future. It took seven years of planning and development for the Solar Impulse to fly at night, and the first major distance flight is not scheduled until 2012.
For more on how photovoltaics work, see NASA.
Some information for this article was taken from AHN.
