Prototype wheel uses braking energy to power bike

High-tech hub will turn any bicycle into a hybrid e-bike

Researchers at the Massachusetts Institute of Technology (MIT) have invented a self-powered wheel that will turn any bicycle into a hybrid e-bike.


The device, unveiled in the Danish capital Copenhagen to coincide with the UN Conference on Climate Change, uses a technology similar to the Kinetic Energy Recovery System (KERS) found in Formula One cars.

Professor Carlo Ratti, director of MIT’s SENSEable City Lab, said: “When you brake, your kinetic energy is recuperated by an electric motor and then stored by batteries within the wheel, so that you can have it back when you need it.

“The bike wheel contains all you need so that no sensors or additional electronics need to be added to the frame and an existing bike can be retrofitted with the blink of en eye.

“In a sense, you drive by foot: when you pedal forward the motor supplements your torque; when you pedal backwards to brake, the motor starts regenerating electric energy while reducing your speed.”

Assaf Biderman, associate director of the Lab, said: “Our goal with the Copenhagen Wheel is to promote cycling by expanding the range of distance people can cover and by making the riding experience smoother. When long distance and steep hills are no longer barriers to comfortable cycling, many cities can become more bicycle-friendly.”

The copenhagen wheel: the copenhagen wheel
MIT SENSEable City Lab

Riders control the wheel using a smart phone, such as the Apple iPhone. When mounted on the handlbars, the phone can be used to switch gears and motor modes while riding.

Sensors within the huge red plastic hub housing can be connected to the phone via Bluetooth so the rider can monitor speed, direction and distance traveled, collect data on air pollution and even check the proximity of their friends.

Another nifty feature is the wheel’s smart lock: if somebody other than the owner tries to move the bike – ie. if the wheel fails to detect the owner’s smart phone – it goes into a mode where the brake regenerates the maximum amount of power, and sends the owner a text message. Biderman said: “So, in the worst case scenario the thief will have charged your batteries before you get back your bike.”

The copenhagen wheel: the copenhagen wheel
MIT SENSEable City Lab

The initial prototypes of the Copenhagen Wheel were developed along with Ducati Energia and the Italian Ministry of the Environment. It is expected that the wheel will go into production next year, with a tag price competitive with that of a standard electric bike.

According to Claus Juhl, CEO of Copenhagen, the city might place the first order and give bicycles retrofitted with the Copenhagen Wheel to its employees as part of the city’s goal to become the world’s first carbon-neutral capital by 2025.


Lord Mayor Ritt Bjerregaard said: “Our city’s ambition is that 50 percent of the citizens will take their bike to work or school every day. So for us, this project is part of the answer to how can we make using a bike even more attractive.”