Novel insights of thermodynamic efficiency calculations of electrolyser systems for hydrogen production

This paper investigates the thermodynamic efficiency of hydrogen electrolysis systems and addresses especially the frequent use of a simplified thermoneutral cell voltage value of U<inf>th</inf> = 1.481 V, which can lead to erroneous results. The analysis shows that significant deviations occur, particularly in systems with low operating pressure, which is problematic since these technologies are pursued by several manufacturers. To close this research gap, a methodological approach to correctly calculate efficiency is presented. The paper outlines the basic principles of efficiency calculation, the derivation of a polynomial function to determine the thermoneutral cell voltage with high accuracy, and the structure of a COMSOL simulation model. This innovative approach provides a precise and user-friendly solution for simplifying and enhancing the accuracy of efficiency calculations. In addition, further influencing factors are illustrated using an example to enable a well-founded comparison of electrolysis processes. The findings are compared and discussed, providing both improved understanding of electrolysis thermodynamics and a critical perspective on common assumptions in the literature.