People power

These two shortlisted designs also generate electricity from motion and can be used to charge personal gadgets.


The Go Mechanical Charger from Elephant Design, top left, is rubbed against a table or other flat surface. It is targeted towards areas in India where many people have cellphones but power outlets can be hard to come by.
Rollergen, right, from the High Tide Association, connects to a bicycle's back wheel. Its designers say a 3-kilometre ride could fully charge a smartphone.

(Image: Greener Gadgets/Elephant/High Tide Association)