Dottorato in ENERGIA E AMBIENTE

Titolo della tesi: Green Hydrogen Production via Electrolysis: From Laboratory-Scale Research to Industrial Applications

The transition toward a sustainable and decarbonized energy system requires the development of efficient, cost-effective, and scalable green hydrogen production technologies. Water electrolysis powered by renewable energy represents a key solution for enabling large-scale hydrogen production while integrating variable renewable energy sources. However, technological and economic challenges still hinder its widespread adoption, particularly concerning efficiency, durability, and system integration. This doctoral research, conducted in collaboration with the industrial partner Enel Green Power S.p.A., explores green hydrogen production via water electrolysis, covering the entire development pathway from laboratory-scale experimental investigations to industrial-scale system analysis. The study focuses on two low-temperature electrolyser technologies: anion exchange membrane (AEM) electrolysis, a promising but still emerging technology, and polymer electrolyte membrane (PEM) electrolysis, a more established and commercially viable alternative. The research aims to characterize the performance, stability, and scalability of these technologies through experimental studies, mathematical modelling, and techno-economic analyses. The first chapter presents an experimental investigation of a laboratory-scale single-cell AEM electrolyser, focusing on the characterization of its electrochemical performance under varying operating conditions. The study systematically evaluates the effects of key parameters, including temperature, electrolyte concentration, flow rate, and membrane thickness, on cell efficiency and stability. Given that AEM electrolysis is still in the early stages of technological development, assessing long-term durability is critical. For this purpose, extensive aging tests are conducted on two different membrane configurations—one standard (Fumasep® FM-FAA-3-50) and one reinforced with a polyether ketone (PK) matrix (Fumasep® FM-FAA-PK-3-75). The investigation provides insights into the fundamental degradation mechanisms affecting AEM electrolysers, such as the loss of cationic functional groups, catalyst deactivation, and structural deterioration of the membrane-electrode assembly (MEA). These findings contribute to improving the understanding of AEM electrolyser performance and identifying strategies for enhancing its long-term operational stability. The second chapter focuses on the mathematical modelling of PEM and AEM electrolysers, developing detailed electrochemical models implemented in MATLAB/Simulink to predict system behaviour under different operating conditions. The models incorporate the key voltage losses affecting electrolyser efficiency, including activation, diffusion, and ohmic overpotentials. The AEM electrolyser model is validated against laboratory-scale experimental data, ensuring its accuracy in representing the performance of early-stage technology. In parallel, the PEM electrolyser model extends the analysis to an industrial scale, leveraging experimental and operational data from commercial systems. This multi-scale modelling approach provides a powerful predictive tool for evaluating the efficiency and scalability of different electrolyser technologies, supporting optimization strategies and techno-economic assessments. The third chapter investigates the integration of electrolysis into complex energy systems, performing a comprehensive techno-economic analysis of various large-scale hydrogen production scenarios. The study examines the feasibility of utilizing curtailed wind power and floating photovoltaic (FPV) systems for green hydrogen production, analyzing plant configurations, system performance, and economic viability through Levelized Cost of Hydrogen (LCOH) calculations. Additionally, the study evaluates the integration of electrolysers in the transportation sector through a case study on the design and sizing of a hydrogen refueling station (HRS) for a bus fleet, assessing the interplay between hydrogen demand, production efficiency, and economic feasibility. Finally, the research explores sector coupling by analyzing the synthesis of synthetic natural gas (SNG) from CO₂ and hydrogen, investigating different electrolyser technologies, including AEM and solid oxide electrolysis (SOEC). This analysis highlights the role of electrolysis in enabling carbon capture and utilization (CCU), promoting the decarbonization of industrial and energy sectors. This research provides a multi-scale and multidisciplinary perspective on green hydrogen production, integrating experimental testing, numerical modelling, and system-level analysis to address the critical challenges associated with water electrolysis technologies. The study contributes to the advancement of AEM electrolysis by identifying the key factors influencing its performance and durability, while also supporting the deployment of PEM technology through industrial-scale modelling and integration studies. The findings emphasize the importance of material innovation for AEM systems, the scalability potential of PEM electrolysis, and the techno-economic feasibility of integrating electrolysers into renewable energy-based hydrogen production systems. These insights are essential for guiding future developments in electrolysis technologies and accelerating their role in the decarbonization of the global energy landscape.