Influence of Power Conditioning on the Optimization of Energy Harvesting Systems Available to Purchase

Energy harvesting systems have components in both mechanical and electrical domains and in order to optimize the design of the overall system, the effect of practical electrical power conditioning sub-systems on the mechanical operation of the harvester must be taken into account. From basic considerations of a linear energy harvester it is shown that, for optimum mass displacement, the effective load resistance presented to the harvester by the power conditioning circuitry should be equal to or less than the load resistance at the peak power point. Further consideration reveals that peak power per volume may occur at an operating point different to that at which maximum power is achieved. The commonly available building blocks of the power conditioning system have characteristics that make it impossible to operate the harvester in a stable manner in the optimum region, and more complex techniques of maximum power tracking may consume excessive quiescent power and are only valid if maximum power is required at all times. The discussion is illustrated by numerical simulations. Finally a converter topology is described and realized, using discrete components, that goes some way to addressing these issues.