Airnergy numbers don't add up

I don't believe a fucking word of it:

Maximum permitted output power of 802.11 unit: 100mW

Approx size of dongle: O(30 cm^2)

Guesstimate distance from base station: O(100m)

Ratio of a 30cm^2 patch to the surface area of a sphere of radius 100m = proportion of 100mW available as power to draw from the air.

Surface area of 100m radius sphere = 4/3.pi.r^3 = 4188790 m^2 =~ 42x10^9 cm^2.

Ratio of 30 cm^2 to 42 giga cm^2 =~ 7x10^-10

Therefore maximum power available for charging assuming 100% capture efficiency = 7x10^-11W. Let's be generous and round it up to a hundred picowatts. This is supposed to charge up a battery?

Did I drop many, many orders of magnitude in my calculations there, or is this about as likely as using pyramid power to charge your batteries?

i can't be the only one...

...wondering how the hell the hydrogen thing works, can I? Hydrogen + Oxygen -> Water is an energy releasing reaction, so you have to put energy in to seperate them, even with the world's most effective catalyst. Basic chemical physics. So where's it coming from in the "hydrogen generator"? You're going to have to put in more than just water - whether it's electricity (plug in, solar, turn a dynamo handle...) or some kind of renewable chemical supply, powdered, liquid or solid. Probably in the form of disposable packs that you buy at the shops and plug in the bottom of the device.

Funny, I can buy something like that at maplins. A box that you put disposable chemical packs in, a universal cable that clips onto it, and interchangable ends that you plug into your phone (none of this messing about filling it up with hydrogen like it was a bloody ciggy lighter). You don't even need to add any water, just the small, cylindrical packets, which make the energy out of nothing but air. I like to call them Alkalines...

We've been over the Wifi charger nonsense, so onwards. My money's on the spinny thing. It could be quite a therapeutic effort charging it, something you can do almost as an idle tic. I certainly know of the habit from rewinding tapes with a biro in the days when my only player was a five quid walkman with only stop, play, and so-called "fast forward" that was the same as play but without the head and capstan slowing the tape down. Want fast wind? Pop it out, thread the pen through the appropriate sprocket, and make like a 1970s footie fan.

My now several-years-old wind up torch is still going great guns with nary a change of battery or trip to the wall socket, and it can even charge my phone (or would if i hadn't lost the cable down a gutter in Edinburgh). If you had a protracted call to make, or a long walk ahead, the winding could get tiresome, but for short bursts, hunting for stuff in the garage or calling the emergency services it's just fine. Something which fits better in the pocket and has less easily losable bits - and can be wound one-handed, which is the major problem with most dynamo gear on the market right now - could be a winner.