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Solar-Powered Plane to Fly Around the World
securitas writes "The BBC's Carolyn Fry reports on the Solar Impulse project, a plan to circumnavigate the globe in a solar-powered airplane. Adventurers Brian Jones and Dr. Bertrand Piccard, who were the first people to circumnavigate the globe in a balloon in 1999, are behind the Solar Impulse project. The project is proceeding to the design stage after a feasability study determined that the solar-powered airplane concept is a viable idea. While other solar-powered planes like the Helios prototype have relied on a secondary power source (fuel cells), this project will be powered by solar energy alone. Batteries will store energy received in daylight hours to fly all night. The first prototype is scheduled for launch in 2006."
Big spotlights on the ground shining up at the plane as it goes by!
The spotlights will be powered by a combination of coal powered power stations in urban areas, ancient russian nuclear reactors... and furnaces powered by burning kittens.
But the light is enviro friendly!
Helios used fuel cells to *store* energy from the solar cells in a closed system. This new project uses *batteries* to perform the same function. Therefore, the phrase this project will be powered by solar energy alone is not correct in implying there is anything significantly different than the Helios.
(BTW, I did some minor work on the Helios fuel cells)
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"Batteries will store energy received in daylight hours to fly all night."
Why not just fly the other drection and stay in the sunlight?
Earth's circumference: around 24,000 miles.
Hours in a day: around 24.
Speed of Earth's rotation at surface: around 1,000 miles per hour.
Look on your face as the sun goes wooshing past your solar plane: priceless.
If a manned solar-powered plane can fly around the world, then one could conclude that an unmanned solar-powered plane could reliably operate for indefinate periods of time above a city or region while carrying a substantial payload.
We can create controllable aircraft that don't ever have to land. That's huge.
Such a plane could function as the equivalent of a local communications satellite, with the latency benefits of not being thousands of miles away in geosync orbit. It could transmit and receive line-of-sight microwave communications with hundreds of thousands of people. It could relay data to other planes hundreds of miles away. It would also be several orders of magnitude less expensive to fly, and would be maintainable.
Businesses are spending hundreds, sometimes thousands, of dollars a month on reliable private communications between their offices in the same city. There is definately a market for this.
No reason why it wouldn't be manned.
They state a 60 meter wingspan. That would like be about 6 meters wide, if they keep a 10-1 ratio. The ground and sea also reflect a certain percentage of solar energy. Overall, it looks to me that the would have about 360m^2 of direct sunlight potential and about the same amount of reflected sunlight.
The solar power is about 1.3kw/m^2. That is 460KW of direct energy. If they get a 30% reflection on the underside, that is another 140KW of potential energy. About 600KW total. Figure about 15% efficiency and you get about 90KW of power. That is about 120 HP, which is the same power as the rear engine of used on Voyager on it's round the world flight. Electric engines have an advantage here in that they don't lose power with altitude, so their effective engine power at altitude would be higher than that used on Voyager.
Voyager only required two engines for take-off and to provide a secondary engine in case of problems with the first. The weight here will be constant throughout, so they will not need a second engine for take-off. (Voyager was basically a flying fuel tank on take-off and needed 300HP to take-off on it's runway. Once airborne, it only needed 110HP. Without all the fuel on board, 110HP was enough for take-off).
Also, solar panel efficiency improves with a slight reduction in temperature, so they might manage better solar efficiency.
Hmm. There is a dodge I wonder if they have considered. One of the problems with that they are doing is the weight. They have a background in ballooning. I wonder if they have considered incorporating sealed helium bladders in the wings and other areas that are not going to be occupied by people. If they can lower the effective density of the aircraft, then they will effectively lower it's weight. Not sure if it is worth the effort though. The other would be use open those sections to the air, then allow the heat from the solar panels heat the inner wings also effectively lowering the density of the aircraft, but this would not be as effective.