Solar Planes are becoming a reality

Solar aviation traces its roots to the early 1970s, when hobbyists and engineers began using solar cells to power model aircraft. Then, since late ’90 endurance solar flights (day-night cycle) have been realized mainly on unmanned planes. Last summer an unmanned solar plane named “Zephyr” was capable to stay in the air for more than 82 hours (about 3 and half days!). The plane was running on solar power during the day and batteries that were charged by the sun, at night.
Other companies and organizations have also developed similar planes. A solar craft called “SoLong” flew for 48 hours in 2005. The US space agency “Nasa” developed “Helios” vehicle that set and altitude record in 2001 for a non-rocket-powered winged aircraft when it flew up to 29.5 km of altitude.
However, not only unmanned flights have been realised. The Swiss balloonist Bertrand Piccard plans in 2010 to launch “Solar Impulse”, a manned plane in which, in five year time, he will attempt to circumnavigate the globe. A transatlantic flight is planned to be realized already in 2011. In order to be capable to carry a pilot the craft will have a huge wingspan of about 60 m. Furthermore because the plane will be piloted by only one person at time, it will have to make frequent stops and break the journey into various legs.
In May 2008 two Solar Impulse pilots (Bertrand Piccard and André Borschberg), one after the other, spent 25 hours flying non-stop at the controls of a virtual flight in a cockpit identical to the one of the Solar Impulse. The pilots were able to test the ergonomics, the aerodynamic behavior of the plane, the management of the energy consumed by the motors or stored in batteries and the efficiency of these during nocturnal part of the flight.
Being photovoltaic cells capable to produce little amount of power (about 125 watts per square meter with good/optimal solar radiation) the only way to make an airplane flying long distances with so little power is to make it light and with a big wingspan. Solar panels cover almost the entire top surface of the wings and tail.
The prototype should be available by the next summer and the earliest flights will be made under battery power without solar cells, but later tests will be done by applying the complete technology. The team hopes to make several 36 hours flights already in 2009 to demonstrate the ability to fly a complete day-night-day cycle powered only by the sun.
This kind of technology will not replace jetliners in the near future, but it is a great idea to show people what is possible to achieve with renewable energy.


Posted by: Filippo

Resources:
www.solarimpulse.com
www.nasa.gov/centers/dryden/news/ResearchUpdate/Helios/index.html