3 ms·

What about all the square footage present for solar panels?

mikeash 11y ago
It's irrelevantly small. You can build solar-powered aircraft, but they have to be extremely light, huge, extremely slow, and carry almost no payload. Insolation is approximately 1hp per square meter. The Cessna in question has about 16m^2 of wing, so that's 16hp of incoming sunlight. Solar cells are maybe 20% efficient, so that's about 3hp of actual electricity generated. That's not even counting cosine error, which will hurt you badly any time you're not flying at high noon in the tropics.
- RobotCaleb 11y ago
  Great answer. Thanks.
- hyperpallium 11y ago
  converting to OP units: 1 hp is about .75 kW, so 3 hp is 2.25 kW, compared with the 231 kW used by the engine. 1/100. But apart from drones, perhaps a specifically designed aircraft to target this could help: lighter, smaller, larger surface area, slower cruising speed would reduce air-friction so increasing efficiency. Mightn't be practical to get down to self-fueling, but at least make a significant contribution to range. NB: longer flights collect more fuel. Human-powered flight is possible using only 0.35 hp (0.26 kW), though superslow at 18km/hr. See Gossamer Condor http://wikipedia.org/wiki/Human-powered_aircraft http://wikipedia.org/wiki/Human-powered_aircraft EDIT: here's the real deal: human flight, pure-solar, no batteries at all http://wikipedia.org/wiki/Solar_Challenger http://wikipedia.org/wiki/Solar_Challenger EDIT2 Solar Impulse 2 is currently on a circumnavigation of the globe (they store power to continue to fly at night) http://wikipedia.org/wiki/Solar_Impulse http://wikipedia.org/wiki/Solar_Impulse At the moment waiting for ideal weather in the China leg
  - mikeash 11y ago
    Solar aircraft can definitely be done (what with the existence proofs you provided) but they're not very practical. Power consumption is roughly proportional to the cube of speed, so to get the Solar Impulse 2's cruise speed up to, say, 150kts instead of the 49kts it actually does would require 27x more solar collection surface area. If you want to carry two people instead of one, it'll need to be about twice again as big. You'll hit annoying scaling laws since larger structures are proportionally weaker so it'll get even worse.

It's irrelevantly small. You can build solar-powered aircraft, but they have to be extremely light, huge, extremely slow, and carry almost no payload. Insolation is approximately 1hp per square meter. The Cessna in question has about 16m^2 of wing, so that's 16hp of incoming sunlight. Solar cells are maybe 20% efficient, so that's about 3hp of actual electricity generated. That's not even counting cosine error, which will hurt you badly any time you're not flying at high noon in the tropics.

RobotCaleb 11y ago
Great answer. Thanks.
hyperpallium 11y ago
converting to OP units: 1 hp is about .75 kW, so 3 hp is 2.25 kW, compared with the 231 kW used by the engine. 1/100. But apart from drones, perhaps a specifically designed aircraft to target this could help: lighter, smaller, larger surface area, slower cruising speed would reduce air-friction so increasing efficiency. Mightn't be practical to get down to self-fueling, but at least make a significant contribution to range. NB: longer flights collect more fuel. Human-powered flight is possible using only 0.35 hp (0.26 kW), though superslow at 18km/hr. See Gossamer Condor http://wikipedia.org/wiki/Human-powered_aircraft http://wikipedia.org/wiki/Human-powered_aircraft EDIT: here's the real deal: human flight, pure-solar, no batteries at all http://wikipedia.org/wiki/Solar_Challenger http://wikipedia.org/wiki/Solar_Challenger EDIT2 Solar Impulse 2 is currently on a circumnavigation of the globe (they store power to continue to fly at night) http://wikipedia.org/wiki/Solar_Impulse http://wikipedia.org/wiki/Solar_Impulse At the moment waiting for ideal weather in the China leg
- mikeash 11y ago
  Solar aircraft can definitely be done (what with the existence proofs you provided) but they're not very practical. Power consumption is roughly proportional to the cube of speed, so to get the Solar Impulse 2's cruise speed up to, say, 150kts instead of the 49kts it actually does would require 27x more solar collection surface area. If you want to carry two people instead of one, it'll need to be about twice again as big. You'll hit annoying scaling laws since larger structures are proportionally weaker so it'll get even worse.