– Why do electric cars not have solar panels on rooftop so they could be charged while driving/parked
In: Engineering
tl;dr: Rule of thumb: You need about 6.5 m² per kW of solar power give or take. A car has not even 10 m². The extra infrastructure in the car adds to the weight and ruins the little extra mileage.
Maximum solar power at high noon at the equator, above the atmosphere is 1367 W/m².
Assume a car is a 2*5m flat surface, we’d end up with 10m² of possible solar panel area, ignoring the windshield.
Ignoring the filtration and damping by the atmosphere, we’d get a maximum power of 13.67 kW per car, which equals about 18.5 horsepowers. This isn’t sufficient to keep a car driving, but definetely a respectable amount of power to charge the batteries and maybe double it’s range while driving.
Anyway, we were still dreaming of a world where’s always high noon everywhere (90° angle of sunlight), clear blue sky, a world without an atmosphere where all the juicy 1367 Watts per m² reach the surface instead of the maybe 800-900 Watts in reality. Also we entirely ignored the fact that solar panels aren’t 100% efficient, which in reality is 20% at best, and that those solar panels ned to be perfectly clean because their efficiency is squarely dependent on the area.
If at all, we’d get a maximum of about 1.5 kW out of a solar car which isn’t even enough to power a lawn mower, and even if we did it, the extra complexity (charge pump, capacitors, cabling, glass cover etc.) would eat it all up by its weight and the mileage is ruined.
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