sighs Guess it’s math time, because I’m actually interested in this now.
Slow charging on a phone is 1 amp, 5 volts, so 5 watts is what we need. We have an EU plug here, which is 35mm wide. Let’s say the diameter of the green area is 45mm then: that gives us pi*(45/2)^2, or an area of 1600 mm^2 roughly.
Now we start being very generous. The average amount of power falling on a 1 square meter is 163 watts. 0.0016 m^2 for our area, times 163 watts, we get 0.26 watts at 100% efficiency. Solar panels aren’t 100% efficient: the absolute best we have, unconfirmed, is over 24%. Let’s say 25% because it makes the math easier. 25% of 0.26 is 0.065 watts if you do the best possible thing, which is to lay it down on a sunny part of the ground in a flat area.
For those of you keeping track at home, that’s a little less more than 1% of what a normal slow charge on your phone is, and it’s a little over a t of what your phone consumes in sleep mode. The nearest thing it matches is the power used for the antenna in your home wireless router.
Sources:
EU Plug Dimensions
Watts Per Square Meter
Math, and little facts via Wolfram Alpha
Most phones will act as High Power SuperSpeed Devices at a minimum when charging, which is apparently 900mA not 1A, but not too far off.
