Solar Impulse-2, the solar powered plane, is on its 5th leg on the first ever round-the-world solar powered flight. This super lightweight plane is the brain child of businessman and pilot Andre Borschbeg and Bertrand Piccard, known for his ballooning exploits.
The remarkable aircraft carries with it a message about the power and potential of clean technologies, and demonstrates powerfully the feats possible with advanced engineering. Solar energy is predicted to be the dominate source of electricity by 2050 according to the International Energy Agency (IEA).
Track the Solar Impulse-2’s progress on the website http://www.solarimpulse.com/
Building a lightweight plane that is large enough to have living space for the pilots has taken some innovative uses of materials, perfected through the development of the prototype plane Solar Impulse-1. To compensate for the weight of the solar cells and batteries, means that every gram has to serve a purpose.
Solar-Impulse 2 Statistics
- Wingspan of 72m (which is wider than a 747 jumbo jet)
- Weight 2300kg
- Over 17,000 solar cells line the top of the wings,
- Lithium-ion batteries sustain night-time flying
- At sea level: minimum speed of 45 km/h and maximum speed of 90 km/h
- At maximum altitude: from 57 km/h to 140 km/h
How is the plane powered?
17,248 monocrystalline silicon cells, each 135 microns thick, are mounted on the wings, fuselage and horizontal tail-plane, providing the best compromise between lightness, flexibility and efficiency. These cells collect up to 340kWh of solar energy per day over the 269.5m2 surface area they cover.
Solvay, the chemical company, worked on the photovoltaic panels that cover the wingspan. Commercially available solar panels are thin and brittle, so Solvay developed a new encapsulation process to make the panels useable on the aircraft, they were then covered with a film to withstand extreme temperature and pressure.
The energy collected by the solar cells is stored in lithium polymer batteries, whose energy density is optimized to 260 Wh / kg. During the day, the solar cells recharge the lithium batteries which weigh 633 Kg, allowing the aircraft to continue to fly at night. In order to save energy, the aircraft climbs to 8,500 m during the day and descends to 1,500 m at night.
What materials are used to make the plane lightweight?
The entire structure of the Solar Impulse-2 is proportionally 10 times lighted than that of the best glider. To make room for enough battery storage and for living space for the pilots, sheets of carbon weighing a third of the amount of an average piece of printer paper was used (25 g/m2).
The airframe is made of composite materials with a carbon fibre and honeycomb sandwich for robustness. Solvay provided the light-weight honeycomb structure in the wings which limits the aircraft weight.
There are four brushless, sensorless motors, each generating 17.4 hp (13.5k), mounted below the wings, and fitted with a reduction gear limiting the rotation speed of a 4 m diameter, two-bladed propeller to 525 rev / min. The entire system is 94% efficient, setting a record for energy efficiency.
Click on the link to see a video of how the plane was constructed https://youtu.be/3ZWYdi6YYuk
The upper wing surface is covered by a skin consisting of encapsulated solar cells, and the lower surface by a high-strength, flexible skin. 140 carbon-fibre ribs spaced at 50 cm intervals give the wing its aerodynamic cross-section, and also maintain its rigidity.
What else needed to be thought about?
The plane needs to be operated through darkness, which is critical in order to traverse the Pacific and Atlantic oceans.
The slow speed of the aircraft means that the stages will take several days and nights of non-stop flying to complete. So whoever is at the controls will have to stay alert for nearly all of the time they are airborne. They will only be able to have naps of up to 20 minutes, similar to how a single-handed, round-the-world yachtsman would catch small periods of sleep.
They will also have to endure the physical discomfort of being confined in a cockpit that measures just 3.8 cubic metres in volume which is not a lot bigger than a telephone box, for 500 hours of total flight time, up to 5 or 6 days and nights in a row. In addition to these (dis)comforts the weather conditions will vary from -40°C to +40°C and they will be sharing their space with oxygen bottles, parachutes, a life raft and enough food and water for a week.
Pilots & Innovators
12 years of research, tests and development went into this fuel-free round-the-world flight, proving that pioneering spirit and innovation can change the world.
Bertrand Piccard and André Borschberg are the men behind this ambitious endeavour. Piccard, the doctor, psychiatrist, explorer and aeronaut who made the first ever non-stop round-the-world balloon flight, is its founder and chairman. He has an inspiring family history with his father, Jacques Piccard, being the first to reach the deepest place in the ocean (achieved with Don Walsh in the Trieste bathyscaphe in 1960). And his grandfather, Auguste Piccard, was the first person to take a balloon into the stratosphere, in 1931.
Borschberg, an engineer by education and graduate of the Massachusetts Institute of Technology (MIT) in management science is a trained fighter pilot and professional airplane and helicopter pilot, and is the CEO.
Team and Partners: the Solar Impulse team is about 90 people, including 30 engineers, 25 technicians and 22 mission controllers, supported financially and technologically by over a hundred partners and advisers, with the main partners being Solvay, Schindler, ABB & OMEGA.