An african inventor, Cedrick Ngalande, has invented a device called the Green Erg, that could harness the pulling force of a person or moving vehicle, and convert some of it into electricity. Though I don’t see his invention any soon on any European or US market, it seems some say that it will have a great success in Africa, there where you have to make electricity out of anything.
The device consists of two rubber-covered rollers, having dynamos inside. You are tied up to the rollers like you tie up a horse to his cart, and keep walking. While you walk, the dynamos generate up to 2W of electricity, enough to power a cell phone or a radio.
“This is basically a dynamo which is being driven as a result of friction between the ground and the blocks. The small yellowish blocks (these are covered by rubber in the real commercial product) rotate as you pull it.
They are designed to rotate even on bumpy run even roads. We have tested it on moist lawn and have worked. It is very smooth so much that you basically don’t feel any disturbance as you move along.Also read: This Device Extends Your Phone's Battery Lifespan Like Nothing Else. 5% Discount Code: GREENOPT
At normal walking speeds we have gotten more than 2 watts which is more than enough for running cell phones or radios. I envision that people will attach this to themselves and walk with it – or even attach it to an ox-cart, a skating board, bike, etc.”
Usefulness: this could, indeed, produce electricity, but if the above-mentioned person, a poor guy from Uganda or Zimbabwe, would posess a cell phone, wouldn’t he have the money to buy something more easy to use? Would he sacrifice himself just to power a device he wouldn’t normally need? I’m not being mean here, but as far as I know, solar cells are much prettier than this – even if the thing works.