Green Wheels  

MSNBC has an article on an electric bike conversion that is based in the bike's wheel assembly - Green wheel turns pedal bike into electric hog.

The next time you change a bike tire, think about upgrading your power as well. Scientists at MIT are testing a new power generation, storage and propulsion system known as the GreenWheel that will turn any pedal bicycle into an electric hog.

"Just take the wheel off, put a GreenWheel equipped wheel on in its place, plug it in and it should work just fine," said Ryan Chin, one of the GreenWheel designers. "The whole thing has been designed so all the parts except the throttle are enclosed in the wheel."

From the outside, the GreenWheel has the radius of a small dinner plate and is about 2 inches thick. Inside the aluminum frame sits the three major GreenWheel components: an electric generator, batteries and an electric motor.

For now, installing GreenWheel on your own does require a moderate level of technical knowledge or a trip to a bike shop. The GreenWheel can be installed on any bike frame or wheel size, but the original spokes have to be replaced with shorter spokes. Michael Chia-Liang Lin, a master's student at MIT developing the GreenWheel, called his parents in Taiwan, who own a bike shop, to figure out how to respoke the wheel.

Under its current configuration, a bike powered solely by a single GreenWheel (front, rear or both wheel can be equipped with a GreenWheel) has an estimated range of 25 miles. Pedaling the bike doubles the range under electric power, provided the rider isn't traveling at the nearly top speed of 30 miles an hour. The bike can be charged by pedaling or by plugging it into the electric grid.

A GreenWheel equipped bike is a smooth ride, as Discovery News found out during a recent afternoon test ride around MIT's campus. Turning the handle mounted throttle, like any motorcycle, just a few small degrees produces a noticeable increase in power and a light electric hum. The handle-mounted throttle is connected wirelessly to the electric motor in the wheel.

The GreenWheel is also durable. The team estimates its range at 40,000 miles, or about eight years work of travel at an estimated 20 miles per business day.

"You'll have to replace the bike before you replace the batteries," Lin told Discovery News.