The angle at which light hits the panel, θis measured from a line perpendicular to the surface. This means that you will get the most power from the solar panel when the light shines directly on it (θ = 0), since cosine(0) = 1.
Okay, let’s do a quick calculation. The intensity of sunlight at Earth’s location is approximately 1,361 watts per square meterLet’s say our solar panel is 1 meter by 1 meter and has an efficiency of 25 percent (which is very optimistic). If the light hits at an angle of 30 degrees, this solar panel would give us an output of 294.7 watts.
Well, our solar-powered 737 is going to need a batch More power than that. We can calculate the surface area needed to generate 10 million watts. For simplicity, let’s assume that the light is perpendicular to the panels (obviously, this is not realistic). With this, we would need 29,000 square meters of panels.
For comparison, the 737 has a wing area of 125 square meters. If it were covered in solar panels, it would generate 42 kilowatts. That’s a nice amount, but not enough for a passenger plane. To be more specific, it’s 0.4 percent of the energy it would need to stay in the sky.
All in all, it’s pretty hard to imagine any way to make a solar-powered passenger plane. However, that doesn’t rule out electric planes entirely! We may have some nice battery-powered planes one day.
Ah, but what about those solar-powered planes? The key is to fly slower with a smaller mass so that the drag force is less. If the wings are big enough, it is possible to get enough power to fly… until the sky gets cloudy.