Solar powered aircraft

Alternative energy sources are at the top of many agendas as the world looks to move away from its dependence on fossil fuels. But these sources require efficient electronic power management. While cars are already beginning to adopt 'green' technologies, a greater challenge is to harness alternative energy to power aircraft. And the Solar Impulse project is looking to develop an aircraft that can circumnavigate the globe. Flying autonomously by day and night, the aircraft will be propelled entirely by solar energy. The project was launched by Bertrand Piccard – described variously as aeronaut and adventurer – as a mechanism to inspire the development of the new technologies that he believes should be demanded in order to preserve the planet's resources. Through this high profile challenge, he wants to inspire an ethos of sustainable development, engender better respect for the environment and reinforce the idea that technology can work hand in hand with sustainability. "Exploration is not about breaking records, but breaking preconceptions," he says. Using the analogy of dropping ballast from a balloon to gain altitude rapidly, he advises that, to climb out of a crisis, we may have to throw our certainties overboard and identify a new way of thinking. Piccard emphasises the Solar Impulse project is unachievable without pushing back current technological limits. "The greater the challenge, the better the technology needed to meet it." Solar Impulse provides nothing if not a challenge. With an 80m wingspan and severe weight restrictions, the solar powered aircraft is stretching the developers working on all areas of the project. Solar Impulse has attracted an impressive array of sponsors and technology partners, including Altran, Dassault, École Polytechnique Fédérale de Lausanne (EPFL), Services Industriel de Genève (SIG) and Solvay, as well as many specialist suppliers. International engineering firm Altran Technology is a technology partner is closely involved in the overall project management, as well as with more detailed power and energy management aspects. Energy gathered from the wing mounted solar cells not only powers the plane by day, but also recharges the batteries to enable the plane to fly through the night via its four 12hp electric motors. Coordinating the technology involved in the solar cells, the batteries and the motors, Altran's contribution is in the electronic control and energy management systems linking all three elements to the central cockpit avionics console. One of the critical challenges is energy management, which itself embraces multiple threads. Reducing energy consumption drastically is one, while improving efficiency in generating, storing and converting the solar energy is another. Keeping within the tight weight restrictions is a further factor, which influences virtually every consideration. "There are many parameters and variables to weigh up for every element of the design and construction," said Christian Le Liepvre, partnership director at Altran. "The project is at the limit of feasibility. Project management requires vision and decisiveness. Trade off is the keyword throughout!" The primary constraint, Piccard notes, is the pilot. Not only is his weight a significant factor, but he also needs a pressurised cabin in order to reach the altitudes necessary for non stop, long haul crossings of continents and oceans. And he needs additional instrumentation, safety equipment and basic comforts. An on board pilot strongly influences certain technology trade offs, erring on the side of safety and proven solutions, rather than advanced, but untried, innovations. Piccard the adventurer has to balance his pioneering spirit with caution and common sense. The views of the 'weathermen' – in this case, industry visionaries and project managers – are vital. "Do you want to fly very fast in the wrong direction, or descend a little and fly more slowly in the right direction?" Piccard postulates.