Optimum design of a supercapacitor charged by a photovoltaic module

Abstract

A solar-driven charging device composed of a photovoltaic module and a supercapacitor is proposed. Based on the equivalent circuit model of the device, the current–voltage relationship of the hybrid system is established. The energy conversion and storage efficiency and the energy stored in the supercapacitor as functions of the charging time have been derived. The advantage of the theoretical model is that the effects of the series resistance, parallel resistance, solar irradiance, and operating temperature on the charging performance of the supercapacitor can be evaluated. The optimal relationships between the capacitance of the supercapacitor and the charging time at different external conditions, i.e., the optimally matching conditions of the supercapacitor, have been provided. Results show that the proposed theoretical analysis method is capable of efficiently evaluating the performance of photo-supercapacitors under given parameters of practical photovoltaic systems. The proposed model may pave the foundation for the future development of supercapacitors driven by commercial PV modules.