Three technical challenges of the Solar Impulse 2

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2014-05-06

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The Solar Impulse project in numbers

After twelve years of feasibility studies, concepts, designs, not to mention a healthy dose of scepticism from the project’s detractors, the Solar Impulse 2 was unveiled – I was lucky enough to attend the ceremony. I’d seen videos of the prototype, the Solar Impulse 1, and so I was eager to see the Si2 in the flesh. Two features took me by surprise: its sheer size and its look – I actually find it aesthetically quite pleasing. It took a team of 50 engineers and technicians to design and build the Si2 and to complete its mission of flying around the world three main technical challenges have to be overcome..

Challenge #1 – energy to cross oceans and continents

Its wingspan of 72 metres (four metres more than that of a Jumbo 747) packs in over 17,000 solar cells. In order to be able to fly non-stop for five days and nights, the solar energy collected by the monocrystalline silicon cells (each 135 microns thick mounted on the wings, fuselage and horizontal tailplane) will feed into lithium polymer batteries, which will in turn power four motors.

Challenge #2 – flying over 35,000 kilometers

Four brushless, sensorless motors (17.5 hp engines) have an average power over 24-hours of a small motorbike (15 hp) with a maximum power of 70 hp. They are 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.

Challenge #3 – Being as light as possible

With a total weight of only 2300 kilograms (ten times lighter than the best glider) clearly energy efficiency was the key focus for the technical team, led by André Borschberg.

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