Quote:
Originally Posted by jamesqf
My point wasn't so much that solar on phones would be useless, as that there isn't enough energy in ambient indoor lighting to really charge much of anything. Most people don't appreciate the fact that the eye has a very nonlinear response to light: indoor lighting may appear about the same as sunlight to you, but in reality the sunlight is maybe 100 times as intense. Lux - Wikipedia, the free encyclopedia
Now if you're out camping, say, and leave your phone out in the sun, then solar would be useful. But how many people do that? Most keep their phone in a pocket or purse most of the time, and even if left on a table or desk indoors, the charging would be miniscule. Much more cost-effective to have separate solar chargers (which could charge/run any USB-powered device) for those who need such things. |
Yes, exactly. Hence, useless.
Using solar indoors is only worthwhile for calculators that need minuscule amounts of power to run.
A solar panel covering the entire back side of a smart phone and "charged" indoors all day might give it 10 seconds of extra run time. There is no way you could even approach maintaining charge on a phone that is on, but idle.
Here's the math for my office:
30 fluorescent x 28 watt bulbs = 1008 watt
40ft x 36ft = 1440 sq/ft room
1008w / 1440 sq/ft = 0.7w per square foot
Fluorescent energy to light efficiency is 11% at the high end
0.7w/sq/ft x 0.11 light efficiency factor = 0.077 watts of light per square foot
Solar efficiency is 30% at the high end
0.077 w/sq/ft x 0.3 solar efficiency factor = 0.0231 watts of power per square foot of solar panel
iPhone back side area = 0.087 sq/ft
0.087 sq/ft x 0.0231 w/sq/ft =
0.002 watts total solar power
If I turned all the lights on in my office and the back side of my iPhone was entirely covered with the most efficient solar cells available, I would be lucky to get 0.002 watts of power.
My iPhone has a 5.3 watt/hr battery. Lets generously say that at full charge, it can sit 48 hours before the battery is dead.
5.3 Wh / 48 = 0.11 Wh consumed per hour.
0.002 watts of solar power divided by 0.11 watts demanded by phone =
1.8% of the total power used by my phone on, but sitting idle.
Maybe your office is brighter than mine.
