The effect of operating flow rate on the voltage rise of energy extraction by double layer expansion

Abstract

Salinity gradients of water solution can be a great resource for generating clean electrical power. In this work, we used capacitive energy extraction based on double layer expansion (CDLE) technique to straightly convert this energy into electrical energy. We performed the experiment under different flow rates and the external given voltage values and carefully analyzed the result based on the Gouy-Chapman-Stern (GCS) model. We identified some factors that reduce the amount of extracted energy by CDLE cell. In particular, these factors are the occurrence of EDL overlapping inside the porous material and the non-zero internal resistance of CDLE cell. We examined the effect of flow rates on the voltage rise of CDLE cell during the exchanging process from saline water to fresh water. The voltage rise converges rapidly with the increase of the flow rate. This improves the power production as the time required to perform one CDLE cycle is shorter with the higher flow rate. In addition, despite its effect on the EDL formation, the external given potential does not enhance the speed of CDLE cycle.