Dynamic Modelling and Optimization of Hydrogen Refuelling Stations and Their Integration with Renewable Microgrids

The transport sector generates more than 20% of global CO2 emissions, with road transport as the main contributor. The urgent need to reduce the environmental impact of mobility has promoted the development of sustainable vehicles, such us Battery Electric Vehicles (BEVs) and Fuel Cell Electric Vehicles (FCEVs). While BEVs have achieved widespread adoption, FCEVs are increasingly regarded as a viable alternative for heavy-duty applications thanks to their short refueling times and high gravimetric energy density. However, the implementation of FCEVs requires the design of efficient hydrogen refueling stations (HRS) capable of ensuring safe, fast, and complete refueling, in compliance with international protocols, such as SAE J2601-5. In this context, this thesis presents a dynamic modelling of Hydrogen Refueling Stations modelling and their integration into optimized renewable microgrid, addressing both technical performance, techno-economic and environmental feasibility. In particular, the research is structured in three main investigations. The first investigation focuses on a 35 MPa HRS designed to supply an urban fleet of hydrogen buses. A validated Matlab-Simulink model (pressure and temperature prediction errors below 1% in hydrogen tanks) was developed, integrating all main HRS components (hydrogen tanks, compressor and pre-cooling units). A parametric analysis and a more realistic simulation were analysed. The parametric analysis identified optimal initial conditions to maximize consecutive refuelings in one hour (5÷8 refuelings with 3÷7 minute refueling times), while the realistic simulation, based on actual fleet demand and seasonal variations, demonstrated continuous station operability with 3÷4 minute refueling times throughout the year, maintaining compliance with SAE J2601-5 limits through adaptive thermal management strategies. The second investigation focused on the integration of the 35 MPa HRS into a renewable energy microgrid. Three Energy Management Strategies (EMS) were analysed: Green EMS, Mixed EMS and Grid EMS. Multi-objective optimization results showed initial LCOH values close to 25 €/kg (Green EMS) and higher than 23 €/kg (Mixed EMS) for 100% SSR. When accounting for surplus electricity sales at 0.137 €/kWh, costs decreased significantly to almost 17 €/kg for both EMS. Parametric analysis with projected electrolyser cost reductions indicated that renewable-based production could reach just a bit more than 11 €/kg by 2050, becoming more cost-competitive than grid-based production (close to 13 €/kg in the case study analysed). Environmental analysis revealed that FCEV adoption could reduce CO2 emissions by 55% even with grid-only hydrogen production, while Green EMS would achieve a 99% reduction compared to the current diesel fleet (36.84 kt CO2/y). The last investigation examines a 70 MPa HSS for heavy-duty vehicles, modelling the complete infrastructure from dispenser to onboard tanks. Different layouts were proposed, also varying the type of tank, to find the best solution to reduce refueling times. A comprehensive sensitivity analysis was conducted varying key parameters, such as APRR, dispenser and ambient temperatures, pipe length and diameter, tank type and number. Results identified Type III tanks as the best performing configuration (10.11 min refueling time, 221 g/s mass flow rate), with only minor differences compared to Type IV and V tanks (within one minute). The analysis demonstrated that increasing APRR and component diameters improved performance, while higher temperatures and longer pipes increased refueling times. A final compromise was found, in order not to exceed the limits of the SAE J2601-5 protocol.