Numerical modeling of dry cell alkaline electrolyzer for HHO production

Abstract

It is essential to simulate HHO dry cell in order to save money and time. Modeling and prediction of electrical, thermodynamic, chemical, and thermal behaviors of an alkaline electrolyzer is the goal of this work. Alkaline water electrolyzer was designed and fabricated for oxyhydrogen production using NaOH electrolyte of 20 g/L by water electrolysis. MATLAB/Simulink was used to solve the model equations. This study investigates how the temperature affects I-U curve, overvoltage potential, gas flow rate, and energy efficiency at various temperatures. Enthalpy, Gibbs free energy, and entropy were decreased with the temperature rise. Due to the lower energy needed to initiate the reaction and the shrinkage of gas bubbles, the highest activation and ohmic voltages at current density of 300 mA/cm2 are seen at temperature of 40°C but the lowest at temperature 80°C. The highest voltage is shown at the lowest temperature of 40°C and specific current density of 250 mA/cm2. Once the current density reaches 250 mA/cm2, the activation voltage becomes constant. As the current density increases from 50 to 100 mA/cm2, Faraday efficiency increases from 86% to 94%. At temperature of 80°C, the energy efficiency is at its maximum value but it is low at 20°C. Alkaline electrolyzer produces the high rate of HHO with the least amount of consumed power when the temperature is at 80°C. The peak energy efficiency occurs at temperature of 100°C and the lowest energy efficiency at a temperature of 20°C. The error percentages between experimental and theoretical for oxyhydrogen flow rate and cell voltage are up to 6% and 4.1%, respectively, and this confirms the model validity.