While travelling with Indian Railways, sometimes especially during long journeys I experience my phone's battery falling short of electron flow. Although in AC boggies they provide charging points near every berth but not everyone always travels in AC boggies. In sleeper boggies, in most trains they do provide 4 charging points in every boggy but they aren't enough and occupied most of the time by rogues who keep listening to music in full volume with their phones' speakers while charging, hence not letting others charge their phones.
One such situation at hand, and the inquisitive me started thinking of something cool that would work perfectly. I stood at the gate of my boggy feeling the wind at 100KM/hr(that was train's direction in east, so wind's velocity for me was 100KM/hr in the west) with my palm, and then came the EUREKA moment!!!! A smile spread throughout my face. Yeah, I had got the idea! Why not someone build a portable wind powered mobile charger?
How will it work? There can be a wheel with blades which will rotate fast when wind strikes it. The wheel and axle machanism should be connected to a dynamo, a small one used in bicycles for lighting. A 12V/3W will work perfectly. Now the passenger can take his/her hands out of the window or may even stand at the exit gate holding the whole thing in his/her hand. When wind falls on the wheel, it rotates, in turn rotating the dynamo axle which produces an alternating current. Using a rectifier it can be converted to DC. A capacitor with appropriate specifications can be used to smoothen the waveforms produced by the rectifier. This output can be fed to a IC7805 which stabilises the voltage at 5V DC which is required by most mobile phones for charging. Take this output, connect it to a multi-model pin connector which can be used to charge any brand's phone. Now pack this whole makeup in a cool looking case, label it and sell it!!!! Done! Earn loads of money.
It will be very helpful for the travellers who can very practically stay online during long journeys keeping their cellphones charged :)