Thermodynamic Cycle Construction Using Several Types of Commercial Supercapacitors and Fabrication of Electrical Double Layer Capacitors

Abstract

Various energy harvesting systems have been studying to use enormous amounts of thermal energy in Low–Grade Heat (< 130 ℃) which produced in various industries and environment. Notably, the electrochemical thermodynamic cycle which can obtain energy with thermal energy using electrochemical energy storage device has been reported to be able to achieve higher efficiency than conventional thermoelectric devices in small temperature difference by using heat regeneration. Recently, it has been confirmed that the electric double layer capacitor (EDLC), one of the energy storage devices, can construct this electrochemical thermodynamic cycle. However, in the case of other types of supercapacitors, pseudo–capacitor and lithium–ion capacitor, there are no studied that use them to construct thermodynamic cycles. So in this work, the thermodynamic cycles of each supercapacitor were constructed using several commercial supercapacitors that easily available on the market. First, to construct the thermodynamic cycle, the voltage changes due to the temperature changes of each supercapacitor was measured, and the temperature coefficient was obtained by linear regression analysis. Also, after the cycle was constructed, normalized net work and Coulomb ratio of each supercapacitor cycle were calculated, and the efficiency of the thermodynamic cycles were predicted when the heat recuperation efficiency was assumed to be 0% and 100%. Besides, an electric double layer supercapacitor, one of the supercapacitor types, was fabricated to be applied to the thermodynamic cycle, and its performance was measured by electrochemical analysis.