Gallery: Solar Impulse 2 sets world record for longest solar-powered fl...

Solar Impulse 2

The world watched as Solar Impulse 2 (SI2) landed in India on March 10, marking the first time a solar-powered aircraft has landed in the Asian country, as well as setting the world record for the longest solar-powered flight to date. This is the second stop of twelve on the zero-fuel aircraft’s record-breaking trip around the globe, which began on March 9 in Abu Dhabi. The city of Ahmedabad plays host to the vessel for four days, as the crew prepares to take off again for the third leg of their historical journey.

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  1. zeppflyer March 12, 2015 at 3:43 pm

    Congrats to these gentlemen on their accomplishment to date and good luck to them in the future!
    In response to Andre’s comment, it should be noted that solar-powered airplanes are not a feasible route forward for mass market air travel. Solar Impulse cruises at 43mph. It carries no cargo and is built far more lightly than would be feasible for a passenger plane.
    In an idealized scenario, sunlight produces about 100 watts of power per square foot. Of course, this is for only half the day, hence the SI’s massive batteries.
    Ignoring night time and adverse weather, though, a Boeing 777 has about 5000 square feet of wing area. Let’s be generous and say that you could find another 3000 square feet on the fuselage. That’s 0.8 megawatts. And that’s assuming that you’re somehow able to convert that 100 watts into forward thrust at perfect efficiency. This is, of course, is impossible.
    Even in an idealized scenario, though, this 0.8MW pales in comparison to the 166 MW produced by the 777’s two turbines.
    But the 777 carries 400 people at 560mph. Let’s go a little more modest. The DC-3 was the greatest workhorse plane of the mid 20th century. Carrying 21 people at about 200mph, it made air travel safe and convenient. Still, its two piston engines produced 1.8 MW of power, while its wing area of about 1000sqare feet would have yielded 0.1MW of solar power (again, if we were able to turn sunlight into thrust at 100% efficiency.)
    You really can’t go any smaller or slower than this and still have a competitive edge over ground or ocean transport.
    If we’re to have any sort of commercial solar-powered air travel, it will likely come in the form of airships; which require far less energy to move a load a given distance than heavier than air vehicles, and which have much greater surface areas to cover in panels.
    As to electric-powered planes? Who knows how energy dense batteries will get? Maybe they’ll find a niche in the green energy future. However, they’re not likely to pay the weight penalties needed for the extremely minor boost that they would receive from being covered in solar panels. They will be charged on the ground, from the grid, or possibly by some form of beamed power (microwaves, perhaps), but the latter is purely speculative.
    In response to R. Bruce’s comment about the USAF; the military is very much interested in (and is pursuing) solar-powered aircraft to fill the role in which the Predator, Global Hawk, etc are now used: Slow-flying, long-endurance observation drones. Not requiring much speed or payload, these super-light aircraft can stay aloft, powered only by the sun.

  2. R.Bruce March 12, 2015 at 8:23 am

    My Employer is the USAF-Maybe they’d be interested in some of these aircraft?

  3. Andre Ewert March 11, 2015 at 2:29 pm

    Great adventure. Great idea. Clean energy for Flight is possible. Here\\\’s the proof.

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