The GreenWheel is a modular electronic assist device for bicycles that fits inside the wheel of any standard bicycle and provides additional power above and beyond the power provided by the person pedaling.
Developed by William J. Mitchell and other team members at the Smart Cities project at the MIT Media Lab, the GreenWheel puts the motor and its batteries inside a housing that fits into the bicycle's wheel hub.
GreenWheel could be easily retrofitted to existing bicycles or designed as a component of new models.
The MIT Media Lab noted that the product would enable bicycle use for residents of hilly and hot cities, where it is not now practical.
A prototype of the GreenWheel design was created and demonstrated in October 2008.