I first discovered air charging many years ago. I was in the office, and outside wad a digger working on the road, and its engine noise was causing the walls to

I first discovered air charging many years ago. I was in the office, and outside wad a digger working on the road, and its engine noise was causing the walls to vibrate. I thought, i could put some kind of capicitor on the wall positioned to exploit the vibration, and charge my phone with that. Brilliant i thought. I got to work immediatly on the invention. And then realised that running a noisy tractor outside everytime i charge my phone, is going to cost me significantly more money than using the supplied usb charging cable and adapter.