Photovoltaic scavenging systems: Modeling and optimization

The interest in embedded portable systems and wireless sensor networks (WSNs) that scavenge energyfrom the environment has been increasing over the last years. Thanks to the progress in the design oflow-power circuits, such devices consume less and less power and are promising candidates to performcontinued operation by the use of renewable energy sources. The adoption of maximum power pointtracking (MPPT) techniques in photovoltaic scavengers increases the energy harvesting efficiency andleads to several benefits such as the possibility to shrink the size of photovoltaic modules and energyreservoirs. Unfortunately, the optimization of this process under non-stationary light conditions is still akey design challenge and the development of a photovoltaic harvester has to be preceded by extensivesimulations. We propose a detailed model of the solar cell that predicts the instantaneous powercollected by the panel and improves the simulation of harvester systems. Furthermore, the paperfocuses on a methodology for optimizing the design of MPPT solar harvesters for self-poweredembedded systems and presents improvements in the circuit architecture with respect to our previousimplementation. Experimental results show that the proposed design guidelines allow to incrementglobal efficiency and to reduce the power consumption of the scavenger.