CapLibrate: Self-Calibration of an Energy Harvesting Power Supply with Supercapacitors

Achieving perpetual and self-sustaining operation of wireless sensor nodes is an important topic of current research in the field of energy harvesting. Closely related to this is the employment of energy budgeting, i.e., effective utilization of available and future energy resources without pushing a node towards the hazard of energy depletion. Therefore, reliable prediction of node lifetime in context of the available energy within a given time is required. This in turn requires self-calibration of the sensor nodes and their energy harvesting supply. In this paper, we explore and assess models for a supercapacitorbased harvesting supply. The parameters of the models are discussed and determined, so that fast, reliable, and energyefficient calibration becomes possible. Moreover, measurement results for a specific hardware platform are discussed and a roadmap for a self-calibration algorithm is presented.