Surely it would save some carbon emissions if the plane was clad in solar panels and could use solar energy once airborne/above the clouds?
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Answer: the weight of the batteries needed would hinder the plane. Also solar power can still be ysed at night time
There’s a plane that tried that, there basically wasn’t enough surface area to get enough light to power the propellers enough (you still need to use the propellers to stay flying, otherwise you’re just slowly gliding down) so at that point, it’s just a waste of money for not enough power
(I think it was an old discovery or history Channel thing about it)
There simply is not enough energy in the sunlight that hit a regular airplane to power it, just like a normal car can drive with just solar panels.
Airplanes have been made and cars too that can just be powered by the sun. They do not have the speed cargo capacity etc that would be needed to replace regular cars and airplanes
Look at https://en.wikipedia.org/wiki/Solar_Impulse which is a single pilot and no one else in it. The cruise speed is 70km/h
Batteries are heavy. Even the lightest lithium ion batteries are several times heavier than the equivalent energy of jet fuel.
The name of the game in aircraft is keep things light, so in all you’re less efficient adding more batteries, expensive hybrid motor systems, and solar panels than you are just sticking with the kerosene.
While it is theoretically possible for planes to use solar power for their energy needs, there are several practical challenges that make this difficult in practice.
First and foremost, the amount of energy that can be generated by solar panels is very small compared to the amount of energy that is required to power a plane. To generate any useful amounts of energy, the planes would need to have a very large surface area covered with solar panels, which would make them heavy and difficult to maneuver.
Additionally, the amount of energy generated by solar panels can vary depending on factors such as weather and time of day, which could make it difficult to ensure a consistent and reliable source of power for the plane.
Finally, solar panels are not very efficient at converting sunlight into usable energy, so even a plane with a large surface area covered in solar panels would not be able to generate enough power to sustain flight under most circumstances.
A few hours of solar on the panels that could be fit on a plane aren’t enough power to make a meaningful difference for the energy required for a plane to stay in the air, and it would require an additional set of engines to run on electric power.
Honestly the power output of a solar panel is kinda weak. Yeah the wings have a lot of surface area and stuff but the power needed to keep a plane that heavy moving that fast is very high. It just isn’t happening.
And there are concerns with building the plane. Though the air is thinner at high altitudes, they’re basically flying through a hurricane through their sheer speed. How you do have solar panels on the plane, exposed to the light but also able to withstand those winds for hours at a time? I’d be worried about them just getting ripped apart, or otherwise needing some kind of transparent layer protecting them. Gotta be transparent so sunlight gets to the solar panels!
It’s not even remotely practical.
Sorry, this isn’t going to be ELI5. More like ELI15.
A long flight in a 737 might use around 20,000 liters or so of fuel and lasts about 8.5 hours. Jet fuel contains about 34.5 megajoules per liter. The power we can expect to get from the jet fuel roughly comes from energy divided by time (there’s also pesky stuff like efficiency and airspeed vs groundspeed, but just a rough, back of the envelope calculation). That means the plane uses roughly 22.6 megawatts of power to fly. A quick Google search says it’s closer to around 50 MW, but I’m happy to have the right number of digits to confirm my estimate is on the right track. This is also almost entirely at cruising speed. If we wanted to keep just above stall speed, it might be less efficient, but we might use less power overall, so let’s stick with about 20 MW for our number.
The sun hits the earth with roughly 1370 watts per square meter. That and the power we calculated before gives us the size of plane we need covered in solar panels to keep the 737 aloft: 15,000 square meters. That’s about 3.7 acres. So if you had 3.7 acres of solar panels, it could power a 737. But if we scaled up the plane to be able to hold that many solar panels, it would probably take even more.
Clearly the 737 isn’t the lightest plane out there, but it should give a relatively good idea of the scales we’re dealing with. This isn’t going to be viable for commercial flights. It’s maybe decent enough as a novelty for something like the Wright flyer, but still, it’s probably not sustainable considering we have to deal with the efficiency of the solar panels, time of day, tilt of the plane, cloud cover… All of these will affect the power we can get.
One gallon of gasoline is equivalent to 36 kilowatt hours. So it would take 360 of those 2 x 3 foot panels you see on your neighbors roof, in direct sun for an hour to provide the same energy as one gallon of gas. Now let’s say a small plane uses 10 gallons an hour. That’s 3,600 panels. All that’s assuming 100% efficiency.
Thank you all you clever people! Makes total sense. Shame though eh?
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