Solar-powered Hydrogen Production: Modelling PEM Electrolyser Systems for Optimal Integration with Solar Energy

This study presents an experimental approach to modelling PEM electrolysers for green hydrogen production using solar energy. The objective is to implement a temperature steady-state electrolyser model to assess the optimal coupling configuration with a photovoltaic plant and estimate the yearly hydrogen production capacity. The research focuses on the energy consumption of ancillary systems under different load conditions, developing a steady-state operational model that improves hydrogen production predictions by accounting for these consumptions. The model, based on polynomial equations, captures the non-linear variation in energy costs under partial load conditions. PEM electrolysers produce hydrogen above 3.0 quality (99.9% purity), and it is feasible to integrate purification processes to reach 5.0 quality (99.999% purity). While small-scale systems include purification, large-scale facilities separate it, enabling process optimisation. Two models are introduced to estimate hydrogen mass flow depending on purity: a base-purity model and a high-purity model that includes drying and pressure swing adsorption. Both are based on experimental data from a five-year-old small-scale electrolyser and are applicable to large-scale systems at partial load. Due to test conditions, the model applied to large-scale facilities underestimates hydrogen production, affected by energy losses from a non-optimised purification process and electrolyser degradation. Model validation with large-scale operational data from the literature shows the model captures plant behaviour well, despite the consistent underestimation described above. The model is applied to several European locations to identify optimal photovoltaic-to-electrolyser ratios. Oversizing factors between 1.4 and 2 are needed to cover ancillary consumption. The levelised cost remains comparable for both purity levels despite higher energy demands for high-purity hydrogen, due to the greater cost of the electrolyser over the photovoltaic plant.