The carbon-fibre aircraft spans 72 m, wider than a Boeing 747, but its mass is around that of a car. Solar Impulse 2 carries over 600 kg of batteries, allowing it to fly through the night. Its night-flight capabilities are not just for the sake of viewing pretty lights from the cockpit window, as the Solar Impulse 2 is capable of perpetual flight, making its only limitation the human pilot inside. Borschberg and Piccard have developed techniques to maintain vigilance during the absurdly long flight stretches, two of which have been projected to last five days.
The aircraft’s large wingspan and low weight make it especially susceptible to harsh weather conditions. To ensure that the aircraft does not run into potentially dangerous weather, a team of meteorologists constantly monitor the weather patterns on its route, searching for a perfect window of opportunity before every trip. At the start of what was meant to be its longest scheduled flight from Nanjing, China, to Hawaii, Solar Impulse 2 was forced to make an unscheduled stop in Nagoya, Japan, due to bad weather conditions further along its route. After waiting some time for favourable weather, Borschberg successfully made the remaining 7000 km trip to Hawaii. The trip lasted 118 hours, much longer than runner-up Steve Fossett’s 76 hours in a single-seater jet.
The aircraft is currently grounded in Hawaii undergoing extensive repairs on its batteries, which the Solar Impulse team says were insulated too much and overheated on the aircraft’s longest trip to date. The repairs are likely to outlast the end of the season, after which it will be difficult to find a window of opportunity. Piccard said in Hawaii that Solar Impulse 2 will probably continue its flight in 2016 when new ideal weather opportunities present themselves. Once repairs are finished, Piccard is scheduled to fly the plane across 4700lkm of ocean to the US, which will likely take four days. The aircraft will then continue to its final destination in Abu Dhabi, where it began its journey at the beginning of the 2015. Borschberg was met by Piccard in Hawaii, where Piccard commented, “Now you can fly longer with no fuel than you can with fuel. What [Borschberg] has done is not only a historic first for aviation, it’s a historic first for renewable energies, and this is why we are doing this project.” The aircraft is being stored in a hangar at Kalaeloa Airport with the support of the University of Hawaii and the Department of Transportation until it is able to continue its journey.
The Solar Impulse team has repeatedly stated that their project is not intended to demonstrate alternative methods of aviation, although the project has been successful in that regard. Their message is focused more on the potential of solar energy as an alternative for electricity generation. Solar Impulse 2 is meant to prove the rapidly increasing efficiency of solar energy and the trust that is being put into it by both governments and private sectors. In a nearly contemporaneous study to the flight of the Solar Impulse 2, The Australian Centre for Advanced Photovoltaics achieved the most efficient conversion rate ever for solar energy, converting 40% of incoming solar energy into electricity, compared to the typical coal station’s 33% energy conversion rate as reported by the US National Petroleum Council.
The effects of solar power’s increasing efficiency can be seen in industry as well, as more companies and governments take on the challenge of turning a once undesirable industry into a lucrative business opportunity.
The Solar Impulse project has been a challenging task from the beginning and some of the many hurdles the two pilots have had to accept are disappointment and frustration on several occasions, but Piccard leaves inspiring words on his views of the project, stating that “If no one tells you it’s impossible, it means you are not ambitious enough.”
Photo: Kirsty Mackay