RESEARCH ARTICLE Generating Electricity during Walking with a Lower Limb-Driven Energy Harvester: Targeting a Minimum User Effort

Background Much research in the field of energy harvesting has sought to develop devices capable of generating electricity during daily activities with minimum user effort. No previous study has considered the metabolic cost of carrying the harvester when determining the energetic ef-fects it has on the user. When considering device carrying costs, no energy harvester to date has demonstrated the ability to generate a substantial amount of electricity (> 5W) while maintaining a user effort at the same level or lower than conventional power genera-tion methods (e.g. hand crank generator). Methodology/Principal Findings We developed a lower limb-driven energy harvester that is able to generate approximately 9W of electricity. To quantify the performance of the harvester, we introduced a new perfor-mance measure, total cost of harvesting (TCOH), which evaluates a harvester’s overall effi-ciency in generating electricity including the device carrying cost. The new harvester captured the motion from both lower limbs and operated in the generative braking mode t