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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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.
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