In order to help boost their range, many electric and hybrid cars employ regenerative technology where braking energy is stored in the battery instead of simply being wasted. This idea can also be applied to electric-assist bikes, but what about bicycles of the plain old human-powered variety? Isn't it a shame that after having built up some good momentum, you just have to write it all off once you stop? Maxwell von Stein, a student at New York City's Cooper Union for the Advancement of Science and Art, thought so. As his senior project, he recently rigged up a flywheel to an existing bicycle, in order to harness the energy that's lost during braking. That energy can then be used to boost the bike when needed.