Will future planes fly on solar energy?

On March 9, 2015, a plane took off from Abu Dhabi early in the morning and landed in Muscat, Oman, early in the evening. And though it took thirteen hours to complete a short trip that a small aircraft normally makes in less than an hour, it was a historic flight, or at least the first leg in what promises to be a historic journey.

What made it historic? The plane, known as Solar Impulse 2, uses no regular fuel at all; its huge solar panels convert sunlight into electricity, part of which is used directly to power the motors and part of it is used to charge batteries, to be used during nighttime. The plane will attempt to complete a trip around the world in about five months, broken into twelve legs, some as long as five days to cross the Atlantic and the Pacific oceans.

The project is the brainchild of two Swiss visionaries: Bertrand Piccard, a psychiatrist and aeronaut, and André Borschberg, an engineer and businessman. Going back more than ten years ago, they started developing an aircraft that could fly solely on solar energy and as far as possible. Their long-term dream is to see solar, or more generally “clean”, energy used in all areas of our lives, including air transportation. Their hope, for the immediate future, is to raise awareness of the need to develop “clean”, energy-efficient, environment-friendly systems, and to remind the world that aircrafts are the most environment-unfriendly, fossil-fuel loving human devices in use today.

For these short-term and longer-term objectives, they convinced a number of partners and financiers, including the European Space Agency, the (reputed) Ecole Polytechnique Fédérale de Lausanne in Switzerland, and several other major and minor companies, to sponsor the development of an aircraft that could fly long distances using no conventional fuels. The project, which will have cost over 100 million dollars (368 million dirhams), has made a number of technical advances, while showing why public air transport will not soon be achievable solely on solar energy.

Indeed, the Solar Impulse 2 aircraft (the previous version, Solar Impulse 1, had more limited capabilities, range, etc.) can take only a pilot, for its cabin is the size of a big car, but its wings are as large as those of an Airbus 380 or a Boeing 747. Why? Because a large part of the wings carries solar panels, which sunlight-to-electricity conversion are (still) not very efficient, thus requiring wide surfaces in order to deliver just enough power to lift and fly the plane.

Still, a number of improvements had to be made, thus the cost of the project. For one thing, in order to keep the plane as light as possible, expensive materials had to be developed and used. And indeed, the huge wings, which carry that small cabin, weighs no more than about two tonnes, compared to 180 tonnes for an empty Boeing 747. Another important technical achievement made by the team (dozens of engineers and aeronautical experts) is the high efficiency of the plane overall and of the engines in particular. Indeed, the four motors that power the aircraft lose only about 3 % of the energy they take in, whereas conventional engines tend to lose up to 70 per cent of their energy in the form of heat. Emphasising the extreme importance of this aspect of the problem, the International Energy Agency considers energy efficiency as the single most effective way of reducing carbon emissions in the world.

So while we become fully aware of the limitations of this project, we begin to understand the real objectives behind it. If it takes all this to fly just one pilot with great difficulty from one city to another, this is not going to become the transportation method of choice anytime soon.

Piccard and Borschberg, will alternate piloting the aircraft on this historic journey, and in doing so they will make heroic efforts. Indeed, on their trips, which will take between 13 hours and 5 full days, they will not be able to get up (even to “go to the bathroom”), they will only be able to recline the seat into a “bed”, eat, drink, “discharge themselves”, and sleep for only 20 minutes every four or five hours, as the plane will need regular monitoring. They have trained hard to bring their physical and mental powers to the required levels for the task.

And as if that were not enough of an effort, at each stop around the world, they will conduct media and public activities to raise awareness about clean energy sources and efficient, environmentally-friendly systems and technologies.

Piccard likens this “one small step” to the Apollo space missions: “When the Apollo astronauts went to the moon, it wasn’t to launch tourism to the moon and open hotels and make money. It was to inspire the world.” He hopes that this will lead to quantum leaps in solar-panel efficiency and other technical improvements that will allow the world to turn to clean energy.

The trip can be followed on the Solar Impulse website with live video and updates.

Nidhal Guessoum is a professor of physics and astronomy at the American University of Sharjah. You can follow him on Twitter at: www.twitter.com/@NidhalGuessoum.