Engineering student Maxwell von Stein applied the principles of a hybrid car to the bicycle to harness the kinetic energy typically lost when braking. With a variable transmission and a flywheel mounted to the bike's frame, von Stein's bike allows the rider to pick up speed faster after stopping than with a battery.
Image credit Cooper Union
There are a few questions that I would love to know the answer to;
-is the energy saved by having regenerative braking with the flywheel greater than the energy expended by pushing around an extra fifteen pounds?
-flywheels have a big moment of inertia. How easy is it to turn the bike? Doesn't it want to keep going straight?
Flywheels also exhibit precession, " a change in the orientation of the rotation axis of a rotating body." It's the wobble you see in spinning tops. Does it create a problem?
More Flywheel ideas:
Flywheel-Equipped Buses Could be 20% More Fuel Efficient
Flywheel Energy Harvesting System Puts Big Dent in Fuel Consumption at Cargo Ports
Fiskars Momentum Reel Mower Doubles Your Effort with Flywheel Action