Reliable and precise evaluation energy-transfer and efficiency of super-capacitors

Abstract

This article presents a basic physics model for the extraction of the potential-time characteristics of super-capacitors during charging and discharging that specifically accounts for the unique contributions to the power source and their nonlinear behaviors. The essential feature of the proposed extraction method is that it is based on the physical phenomena underlying the electrical characteristics of super-capacitors, this phenomenology model describes the essential features of the potential–time characteristics of the super-capacitors which can then be fit to any physics-based super-capacitor system. There are only three parameters in this elementary physics model and the model is expressed in the form of an explicit function. The best result is that the integral of the model over time results in an explicit function which corresponds to the input and the output energy. There is great beneficial to both super-capacitor designers and industry. The experimental validation of the new model agrees well with the measurements. To avoid confusion in weighing in super-capacitor performance, energy-transfer efficiency is introduced. Experimental and theoretical results show that the minimum energy-transfer efficiency is neither at the maximum current density nor at the minimum current density. We hope, by using this energy-transfer efficiency, the existing inconsistencies and confusion in the evaluation of the super-capacitor performance can be dispelled so as to help facilitate further progress in the field.