Energy and entropy generation analysis in a supercapacitor for different operating conditions

Abstract

Sustainability and efficiency are the key issues concerning performance and lifetime of supercapacitors. In this work, an entropy generation analysis is implemented for the first time in the supercapacitor cell, aiming at facilitating the design and optimization of the supercapacitor systems. Entropy generation analysis accurately quantifies the irreversibilities due to heat transfer, mass transfer and ohmic loss of the supercapacitor cell, satisfying direct identification of the inefficiency mechanisms that cannot be achieved by the conventional energy analysis. The effects of the electrolyte, porosity and charge/discharge current on the thermodynamic irreversibilities and heat transfer characteristics are investigated. The optimal design scheme of the supercapacitor cell is obtained using the optimization approaches based on the combined energy and entropy generation analyses. Results indicate that the main contribution to the irreversibilities is due to ohmic loss, followed by the mass transfer effect. The 1 M TEMABF4/ACN electrolyte with the porosity of 0.4 is found to be the optimal choice, corresponding to the entropy generation rate of 2230 W/(m3·K) and the temperature rise of 0.20974 °C. The outcomes of this work provide a fundamental and computational framework for the development and optimization of clean and renewable energy conversion and storage systems with reduced irreversibilities.