Coming to America: a Swiss solar powered plane

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Ten years ago, when Bertrand Piccard started a project in Switzerland to fly an airplane powered only by sunlight, aerospace companies he spoke to thought he was nuts. That was a good thing, he said, because it told him that he had come up with a worthy challenge that could make a big impact on people’s lives.

The project, called Solar Impulse, went on to set world records and spark imagination for a future when air travel could leave low-carbon footprint. Now that plane, embedded with solar cells from SunPower, will make its first flight in the United States this year. The plan calls for running test flights in April and taking off in northern California — likely from NASA’s Moffett Field — in May.

“We want to inspire people to go beyond the limitations they have set for themselves,” Piccard said during an event to present Solar Impulse at an affiliate of the Swiss Consulate in San Francisco Tuesday night. “We want to show with Solar Impulse the need for clean technologies.”

When the plane preps for its flight east to Washington, D.C. and then New York, it will be an awesome sight to behold. The aircraft’s designs aimed to create ample surface area to accommodate solar cells and to minimize its weight and energy needs. The single-seat plane has long wings: at 63.40 meters (208 feet), about the wingspan of an Airbus A340. Yet at 1,600 kilogram (3,527 pounds), it has the heft of a sedan.

It’s also got the power of a scooter: four engines of 10 horsepower each. The plane also sports four lithium polymer batteries to store solar energy during the day in order to power the plane at night. The 11,628 solar cells blanket both the wing and the horizontal stabilizer.

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The batteries made it possible for Solar Impulse to complete a 26-hour flight in 2010. The four batteries collectively could provide 90 kilowatt-hour of energy, and they are well insulated so that they could still function at minus 40-degree Celsius, which is the temperature at the plane’s maximum cruising altitude of 8,500 meters (27,900 feet). Each has the energy density of 240 wh/kg. The four batteries weigh a total of 400 kilograms (881 pounds), or about a quarter of the total weight of the plane.

Instead of flying without stopping to show off the aircraft’s technical prowess, the plane will land at three places between San Francisco and the nation’s capital. The idea is to educate the public about the solar-powered plane and inspire people to support clean tech.

The successful flight of 2010 came after years of engineering and flight simulations to figure out and correct problems. The plane took its maiden flight in 2009. The Solar Impulse’s home is at the research institute called Ecole Polytechnique Federale de Lausanne, and it materialized at the hands of nearly 80 engineers, technicians and mission controllers. The $130 million project also has relied on many corporate sponsors, including chemical company Solvay, Omega, Deutsche Bank and Schindler, an engineering firm.

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Piccard is a founder with a colorful background. A psychiatrist, he co-piloted the first balloon that traveled non-stop around the world. His father, Jacques Piccard, was the first, along with Don Walsh of the U.S. Navy, to explore the deepest part of the ocean, located in the Mariana Trench. His grandfather, Auguste Piccard, set world records for flying balloons to great altitudes.

Piccard and the CEO of Solar Impulse, Andre Borschberg, came to San Francisco to drum up interest not only for their maiden flight across the country but also the around-the-world voyage they plan to take in 2015. Solar Impulse is building a second, larger plane to circumnavigate the world. It has yet to release the technical specs of the new plane, though Borschberg said SunPower will be the cell supplier. The second plane will still use lithium polymer batteries, but they will have an energy density of 261 wh/kg.

While Solar Impulse has demonstrated that solar energy could be a stand-alone fuel, the days of solar-powered commercial flights are far far away. Borschberg, an engineer and an airplane pilot, believes those days are still about four decades away.

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Some interesting tidbits:

*Because of its light weight, the aircraft avoids turbulence by using weather data to calculate the best flight path. It usually takes off early in the morning and land at night.

*The average flying speed of the first plane is 70 kilometers per hour (43 miles per hour). It takes off at 44 kilometers per hour (27 miles per hour).

*The payload, or carrying capacity, of the first plane is 200 kilograms (440 pounds), which account for the pilot and cargo.

*The cockpit of the second plane will be larger so that the pilot could sleep throughout the journey, which will last nearly a month long.

*Negotiating for permissions to fly in and out of countries around the world is a lot of work. It took two years for China to say yes.

*The second plane will have a pressurized cockpit and on-board production of oxygen.

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