A compact and light-weight generator for backpack energy harvesting

The reciprocating linear motion of a heavy backpack during walking has proved to be a viable source from which significant amount of electricity can be harvested. The energy harvesting systems proposed so far either use a mechanical rack and pinion to convert the linear motion to rotation or use a direct drive permanent magnet linear generator. This paper makes the case for the use of a magnetic gear to convert the linear motion to rotation. Compared to the mechanical rack and pinion, the proposed system is expected to have less noise, friction, and maintenance requirement and to facilitate the packaging. Compared to a direct drive linear generator, the proposed system would be multiple times lighter and compacter. The principles of backpack energy harvesting are outlined and design specifications of the proposed system are derived. An initial design is presented along with some simulation results.