INNOVATIVE SYSTEMS FOR PRODUCTION, STORAGE AND USE OF GREEN AMMONIA IN MICRO-GAS TURBINE FIELD

In recent decades, ammonia has gained attention as an effective hydrogen storage medium that can be easily dissociated and used as a sustainable fuel, particularly for power generation. Compared to hydrogen, ammonia offers significant benefits in terms of cost, storage, and distribution due to its higher hydrogen density and simpler handling requirements. Moreover, the ammonia production process is well-established at an industrial scale and serves as a fundamental component for the agricultural sector. However, ammonia production is associated with significant greenhouse gas emissions and using ammonia directly as a fuel poses challenges due to its notably low flame speed, making it difficult to utilize for power production purposes. The first section of this thesis presents a detailed literature review covering ammonia as an innovative fuel, its properties, development, and applications, including safety and distribution. It also examines traditional and emerging ammonia production methods, key industry players, the use of ammonia in gas turbines, including the challenges associated with its implementation. The second part of the thesis explores an innovative 15kW electrolyzer-based Power-to-Ammonia (P2A) system designed to significantly reduce CO₂ emissions. A complete description of the demonstration plant, installed at the University of Genoa's Innovative Energy System Laboratory (IES Lab), is provided. The system was assessed from both technical and economic perspectives using a detailed MATLAB/Simulink model. Results showed that the system achieved a round-trip efficiency of 41–42% with a maximum ammonia production of 12 tons per year. From an economic perspective, limitations arises due to the prototype size, resulting in a Levelized Cost Of Ammonia (LCOA) of about 3,557 €/ton NH3. Consequently, a scaled-up analysis based on a 1MW electrolyzer plant was conducted, revealing a LCOA of 1,368 €/ton NH3 for steady-state operation when the system is fed by the national grid, and 1,370 €/ton NH3 when powered exclusively by PV. The integration of a battery was also examined and found to be economically viable only with an 80% reduction in battery capital costs. The third part of the thesis focuses on the application of ammonia in micro-gas turbines (mGTs). An experimental test campaign conducted in 2024 at the University of Genoa laboratory demonstrated the feasibility of using ammonia-natural gas blends, maintaining turbine stability and power output across loads ranging from 100% to 43%. Despite a slight efficiency decrease of approximately 2%, CO2 emissions were reduced by 19.5% compared to pure natural gas operations. However, NOX emissions increased significantly, highlighting the need for effective reduction strategies. Additionally, the study identified challenges such as ammonium carbonate formation in the fuel lines, requiring natural gas pretreatment. A detailed MATLAB/Simulink model of the mGT was validated, enabling further simulations with various fuel mixtures and operational conditions. Results demonstrated that a 20% cracked ammonia blend allows for zero CO2 emissions while maintaining safety and cost advantages over hydrogen. The final chapter investigates the use of ammonia in a Hybrid System (HS) consisting of a Solid Oxide Fuel Cell (SOFC) coupled with a bottoming mGT. Simulation results for methane, biogas, and ammonia-fueled systems showed that ammonia offers the potential for CO2-free energy production with high power output. Among different configurations, the ammonia-based setup achieved the best performance, with a net power output of 301.30 kW and a system efficiency of 56%.