The lifetime prediction of supercapacitors is of great significance to the management of energy storage systems, but the phenomenon of capacitance regeneration may occur in the aging cycle experiment of supercapacitors, which will bring about interference to its lifetime prediction. In this paper, the critical factors affecting the capacitance regeneration of supercapacitors are investigated, so as to analyze the influence of the regeneration phenomenon on the lifetime prediction of supercapacitors. The results show that the regeneration performance of supercapacitors is closely related to the working voltage, temperature, aging depth and recovery time. When the charging voltage is increased, the amplitude of the capacitance regeneration decreases, and with the deepening of aging degree, the amplitude of the capacitance regeneration decreases gradually. The temperature has little effect on the amplitude of the capacitance regeneration, but the higher the temperature, the longer the recovery time of capacitance regeneration. In addition, the regeneration capacitance of supercapacitors decays faster than its inherent capacitance under the same aging test conditions. Considering the capacitance regeneration characteristics, the aging trend of supercapacitors is predicted by using support vectors machines method. The prediction results are basically identical with the experimental results.
With the rapid development of society, all kinds of non-renewable energy resources are constantly developed and utilized, energy storage is one of the best ways to solve the energy shortage. In this study , levulinic acid (LA) and 1,4 butanediol (BDO) were used to synthesize a novel polyol ester (LABDO) by biological and chemical methods. The biological method exhibited excellent performance in the synthesis process, where 87.5% of LABDO yield under optimal conditions, while the chemical method had more byproducts and higher energy consumption. Finally, the thermal properties of the obtained phase change materials (PCMs) were evaluated. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed that the melting temperature of LABDO was 50.51°C, the latent heat of melting was 156.1J/g, and the pyrolysis temperature was 150-160°C. Compared with traditional paraffin wax, the prepared PCMs have suitable phase transition temperature, higher latent heat of melting and better thermal stability. The thermal conductivity can be increased to 0.34W·m-1· k-1 by adding expanded graphite. In summary, LABDO can be used as low temperature phase change energy storage materials.
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