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Why don't planes have solar panels on the wings?
I've been wondering recently why planes don't have solar panels on their wings. I mean, into the structure of the surface of the wings, thereby functioning as the lifting surface and an energy generator. My minimal knowledge of engineering and solar cell technology leaves me assuming that it is because the weight outweighs any potential harvest of energy. Anyone know any better than me, please comment...
__________________ Lose a sense and those left compensate. That's why people with no sense of humour have a greater sense of self-importance.
Probably the same reason we don't have them on our homes. Cost vs. benefit. Not to mention the fact that they are somewhat fragile and would be a maintenance nightmare. Durability is more of an issue than is flexibility I believe. Case in point...
Planes have alternators where are quite efficient generators of electricity.
I don't want to sidetrack your thread but I'm curious why we don't harvest the static charge rather than using wicks to dissipate it. Maybe some aircraft do and I'm just not aware.
Short answer: solar power is not very intense, so in direct sunlight you'd gain about the same energy as a half gallon or so of jet fuel every hour.
Long answer: the insolation rate above the earth's atmosphere is around 1.4 kiloWatts per square meter, and after absoroption in the atmosphere the rate in the desert southwest can approach 15 kiloWatt-hours per day so assuming 15 hour days let's say 1 kiloWatt per square meter is practical. Typical solar panels around 10% efficient, so we're down to 0.1 kiloWatt delivered per square meter. The wing area of a 737 is around 125 square meters, and for guesstimation purposes let's say we can cover 100 square meters with solar panels so we can deliver around 10 kiloWatts. In one hour, you get (1e4 joules/sec)*(3600 sec)=3.6e7 joules or 36 megajoules. The energy content of Jet A is around 43 megajoules per kilogram, and the thermodynamic (Carnot) efficiency of turning that to work is around a third, so one hour of energy from the solar panels would be equal to the energy gained by burning around 2 kilograms (or around half a gallon) of jet fuel.
Solar energy is great on a satellite, where you can't possibly carry enough liquid chemical fuel to meet the low power needs of the satellite over many years. It's great on rooftops where you already need to cover a surface. However, it's not great for high power density requirements like airplanes or cars, and storage is problematic (batteries have about a hundred times more mass per energy stored than liquid chemical fuels do).
Programs: NZ*G, TK*G, BAEC Gold, VS Red, Hertz President's Circle (RIP Diamond Club)
Posts: 617
Quote:
Originally Posted by altaskier
Short answer: solar power is not very intense, so in direct sunlight you'd gain about the same energy as a half gallon or so of jet fuel every hour.
Long answer: the insolation rate above the earth's atmosphere is around 1.4 kiloWatts per square meter, and after absoroption in the atmosphere the rate in the desert southwest can approach 15 kiloWatt-hours per day so assuming 15 hour days let's say 1 kiloWatt per square meter is practical. Typical solar panels around 10% efficient, so we're down to 0.1 kiloWatt delivered per square meter. The wing area of a 737 is around 125 square meters, and for guesstimation purposes let's say we can cover 100 square meters with solar panels so we can deliver around 10 kiloWatts. In one hour, you get (1e4 joules/sec)*(3600 sec)=3.6e7 joules or 36 megajoules. The energy content of Jet A is around 43 megajoules per kilogram, and the thermodynamic (Carnot) efficiency of turning that to work is around a third, so one hour of energy from the solar panels would be equal to the energy gained by burning around 2 kilograms (or around half a gallon) of jet fuel.
Solar energy is great on a satellite, where you can't possibly carry enough liquid chemical fuel to meet the low power needs of the satellite over many years. It's great on rooftops where you already need to cover a surface. However, it's not great for high power density requirements like airplanes or cars, and storage is problematic (batteries have about a hundred times more mass per energy stored than liquid chemical fuels do).
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__________________ Lose a sense and those left compensate. That's why people with no sense of humour have a greater sense of self-importance.
The flow over the wings is critical to flight performance and efficiency. Those little winglets you see on the ends of the wings can increase fuel efficiency by 3-5%!!! This is part of the structure that you really can't play with too much.
You might get a couple of kW total electrical power out of solar cells whereas an APU has lots more.....
Short answer: solar power is not very intense, so in direct sunlight you'd gain about the same energy as a half gallon or so of jet fuel every hour.
Long answer: the insolation rate above the earth's atmosphere is around 1.4 kiloWatts per square meter, and after absoroption in the atmosphere the rate in the desert southwest can approach 15 kiloWatt-hours per day so assuming 15 hour days let's say 1 kiloWatt per square meter is practical. Typical solar panels around 10% efficient, so we're down to 0.1 kiloWatt delivered per square meter. The wing area of a 737 is around 125 square meters, and for guesstimation purposes let's say we can cover 100 square meters with solar panels so we can deliver around 10 kiloWatts. In one hour, you get (1e4 joules/sec)*(3600 sec)=3.6e7 joules or 36 megajoules. The energy content of Jet A is around 43 megajoules per kilogram, and the thermodynamic (Carnot) efficiency of turning that to work is around a third, so one hour of energy from the solar panels would be equal to the energy gained by burning around 2 kilograms (or around half a gallon) of jet fuel.
Solar energy is great on a satellite, where you can't possibly carry enough liquid chemical fuel to meet the low power needs of the satellite over many years. It's great on rooftops where you already need to cover a surface. However, it's not great for high power density requirements like airplanes or cars, and storage is problematic (batteries have about a hundred times more mass per energy stored than liquid chemical fuels do).
Best
Answer
Ever
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+1 (many). Like others, may steal the long answer where in reality only understood the short one!
I didn't mean instead of fuel! Didn't the solar plane above store enough charge to fly round the world?
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