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A plane that can fly at a high altitude and be powered only by the sun could stay aloft for years, but one of the key challenges for flying wings or planes powered by solar panels is keeping the sun's light hitting the panels.

That's why Boeing's flying wing looks so odd: "The present disclosure provides a solar powered aircraft including a modular main wing and a pair of relatively large modular winglets attached to the transverse end portions of the main wing. To collect solar radiation, including relatively low-angle radiation, solar panels are mounted to both the main wing and the winglets," the company writes in its patent application.

The application also lists potential uses for a solar-powered plane that could stay in a fixed position over a city, for example:

imaging systems such as a camera or radar;

communication systems for use with radio signals, cell phone signals, microwave transmissions, earth-to-satellite links, television broadcasts, internet connections, payload-to-payload linkages, and the like;

atmospheric sensing systems for measuring wind, temperature, humidity, gases present, sunlight, and other purposes.

This plane would be fundamentally different from the piloted solar plane currently hopping across the planet. Flying people around the world in planes powered by sunlight sounds cool, but there's a problem, as the Boeing application also points out:

If a Boeing 747 were equipped with perfectly efficient solar cells on its entire upper wing surface, it would receive at most approximately 600 kilowatts, or about 800 horsepower from the solar cells. This compares with approximately 100,000 horsepower required for the 747 to maintain cruising speed and altitude. Thus, solar power can provide only 0.8% of the needed power to a conventional 747, even if the solar cells are 100% efficient and the sun is directly above the airplane. With typical very good cells, solar power can provide only 0.3% of the needed power to a 747. The conclusion is that a very special airplane is needed--one that can fly on very low power while gathering lots of solar energy.

Consequently, it's unlikely you and I will be getting around via solar-powered planes, but clearly there are other uses for such vehicles.

From: SeattlePI.com

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