While the idea of harnessing the sun's energy for fuel has been around since the 1830's the impetus to use this free and clean source of power for commercial transportation seems to have accelerated lately. Just a month ago, the MS Turanor Planet Solar, became the first solar-powered boat to circumvent the globe and now, a single-passenger airplane has taken the green energy to the skies with a successful Intercontinental flight.

The first leg of the solar plane's history making journey began from Switzerland's Payerne aerodrome on Tuesday May 24th, 2012. With Captain Andre Borschberg at the helm the Solar Impulse that sports a 207-foot wingspan took to the skies, cruising at a speed of about 43.5 miles per hour. Its biggest challenge was getting over the Pyrenees Mountains that lie along the border of France and Spain. While Andre was equipped with a parachute in case something went drastically wrong, he did not have much to worry about.

Everything went according to plan as he soared in the blue skies, flying alongside a barrier of clouds at an altitude of about 26,000 feet. The Solar Impulse arrived at the first designated landing spot in Madrid, Spain in the early hours of Friday morning after flying non-stop through the night for a total of 17 hours 30 minutes and 50 seconds.

While the second and final stretch of the historic flight was scheduled to begin shortly after, it had to be postponed for a few days due to bad weather. On June 5th, 2012, Solar Impulse was finally given the green light and took off, this time with the company's second founder, Bertrand Piccard at the helm. Cruising over the Strait of Gibraltar at an altitude of 27,000 feet and an average ground speed of 32.19 mph, the solar fueled plane flew for almost 20 hours before landing flawlessly at Morocco's Rabat-Sale International airport at 11.30 pm. The best part about the flight? Not a drop of petroleum-based fuel was used and even after flying for such a long stretch of time, the plane's batteries were still 95% charged!

While the entire journey may sound like a slow lumbering flight, the Solar Impulse has come a long way since its inaugural 30-second flight in 2009 when it rose just 3-feet above the ground and covered a distance of 1,150 feet. Believe it or not, that too was a history-making flight!

The current prototype comprises of 12,000 solar cells fitted onto the airplane's long wingspan, that capture the sun's energy and transfer it to four 10-hp electric motors. They also help charge the 882 pounds of lithium batteries that power the Solar Impulse during the night. In order to conserve and store as much captured energy as possible, the airplane is programmed to travel at reduced speeds even during midday hours, when the sun is at its peak.

With this latest Crossing Frontiers mission out of the way, the jubilant Swiss inventors/pilots - Bernard Piccard and Andre Borschberg are now preparing for the ultimate trip - A journey around the world. This is not the first time Mr. Piccard has made history. In 1999, the adventurer made headlines after completing a non-stop journey around the world, in a hot air balloon!

Though solar-powered planes have a long way to go before they can be used for commercial flights, the Solar Impulse certainly brings them a step closer to reality. To read more about this fascinating aircraft check out solarimpulse.com

Resources: Gizmag.com, solarimpulse.com, engadget.com