Performance of a reverse electrodialysis cell working with potassium acetate−methanol−water solution

Abstract

Salinity gradient energy exists between the concentrated and diluted electrolyte solutions, which can be converted to the electromotive force of a reverse electrodialysis (RED) cell. The waste solution is regenerable to restore the initial concentrations by absorbing thermal energy. The energy conversion efficiency of such a heat−to−power system is strongly influenced by the working solutions. The potassium acetate−methanol−water solution is proposed and assessed as the new candidate working fluid for the RED power system in this study firstly. The electrical conductivity of this ternary solution is fully measured and found to be influenced by the solution concentration, temperature and solvent composition. The maximum measured electrical conductivity value is 144.0 mS cm−1 at 6.0 mol kg−1 at 313.15 K. Furtherly, the electrical convertibility of potassium acetate−methanol−water is tested under the varying conditions freshly. The RED cell performances are influenced by the concentrations of the feeding dilute solution (recommendation: 0.02 mol kg−1), concentrated solution (optimum: 6.0 mol kg−1), solution flow rate (approximately 1.5 cm s−1), solution temperature (20 K higher than the environmental temperature), solvent composition (aqueous methanol solvent is preferred), and width of solution compartment (100 μm is suitable). Potassium acetate−methanol−water is a competitive new working fluid with the comprehensive advantages in thermodynamic and electrochemical properties.