Development and Experimental Validation of a Model to Simulate an Alkaline Electrolysis System for Production of Hydrogen Powered by Renewable Energy Sources

This work shows an ASPEN Plus model to simulate an alkaline electrolysis plant with the objective of evaluating the performance of a complete system under different operating conditions, such as temperature, pressure and current density. As this type of process modelling software is not able to simulate the behavior of the electrolysis cells, an electrochemical model has been previously developed. It is a semi-empirical model that allows determining the voltage cell, Faraday efficiency and gas purity as a function of the current, using both physical principles related to the electrolysis process and statistical methods. The different parameters defined in the equations of the model have been calculated by MATLAB, using a non-linear regression, on the basis of experimental data from different experiments obtained of an alkaline test bench. These equations have been used as a subroutine within an ASPEN Plus model including the rest of balance of plant (BoP) components to analyze a complete alkaline electrolysis plant to produce hydrogen. The obtained results allow determining which process variables are the most influential and hence, should be optimized in order to improve the performance and operation of an alkaline electrolyzer.