Parasitic Shunt Currents in Alkaline Water Electrolysis (AWE) for Generating Clean Hydrogen

Since the beginning of the 20th century, alkaline electrolysis has been used as a proven method for producing hydrogen on a megawatt scale. The existence of parasitic shunt currents in alkaline water electrolysis, which is utilized to produce clean hydrogen, is investigated in this work. Analysis has been done on a 20-cell stack. Steel end plates, bipolar plates, and an electrolyte concentration of 6 M potassium hydroxide are all included in the model. The Butler-Volmer kinetics equations are used to simulate the electrode surfaces. Ohmic losses are taken into consideration in both the electrode and electrolyte phases, although mass transport constraints in the gas phase are not. Using an auxiliary sweep to solve equations, the model maintains an isothermal condition at 85°C while adjusting the average cell voltage between 1.3 and 1.8 V. The results show that lower shunt currents in the outlet channels as opposed to the intake channels are the result of the electrolyte’s lower effective conductivity in the upper channels, which is brought on by a lower volume fraction of the electrolyte. Additionally, it has been seen that the shunt currents intensify as the stack gets closer to the conclusion. Efficiency is calculated by dividing the maximum energy output (per unit of time) that a fuel cell operating under comparable conditions might produce by the electrical energy needed to generate that output inside the stack. At first, energy efficiency increases due to the rise in coulombic efficiency, peaking around 1400 mA. The subsequent decline after reaching 1400 mA is linked to an increase in stack voltage at elevated current levels.