With magic solar panels and full sun an iphone shaped solar cell could charge my iphone fully in under an hour and a half. Good commercial solar cells can get a

With magic solar panels and full sun an iphone shaped solar cell could charge my iphone fully in under an hour and a half. Good commercial solar cells can get a little more than 20% efficiency so really with good sun and a bit of restricted usage an iphone with a solar cell for a back that got a lot of sunshine could power itself enough to be practically useful. With the ability to scale down the power usage with processors that do a whole lot less it’s certainly practical to get much more out of usable processors. You can do a lot with, say, 10 watt hours per day and that much is certainly achievable on a hand held device.