A techno-economic study of photovoltaic-solid oxide electrolysis cell coupled magnesium hydride-based hydrogen storage and transportation toward large-scale applications of green hydrogen†

The large-scale development of green hydrogen energy offers a critical solution to the challenges posed by greenhouse gas (GHG) emissions and global climate change. Conducting an early technical and economic evaluation of an efficient and safe hydrogen production, storage, and transportation pathway is challenging but essential for enhancing the future global hydrogen energy supply chain. In this work, we conceive and forward a new hydrogen utilization route via photovoltaic-solid oxide electrolysis cells coupled with magnesium hydride-based hydrogen storage and transportation (PV-SOEC-MgH₂). The detailed design and simulation suggests that the thermal integration between SOEC and hydrogenation processes of magnesium exerts the energy and exergy efficiencies of 86.71% and 42.31%, respectively, in the hydrogen production process. The optimization of the fins and transfer structures in the metal hydride bed exerts the potential to increase the SOEC electrical efficiency by 5–9.3%. Besides, by implementing engineering operation data from solid oxide electrolysis cells (SOECs) and magnesium hydride-based hydrogen storage and transportation technology, we evaluate the technological feasibility, economic viability, thermodynamic performance, and environmental impact of this hydrogen utilization route and investigate its large-scale application potential. The current levelized cost of hydrogen (LCOH) production by PV-SOEC in China is estimated to range from 3.3 $ per kg_H2 to 5.8 $ per kg_H2, and will be minimized to 1.20–1.73 $ per kg_H2 by 2050 along with technology development. In addition, the LCOH in production is projected to decrease to 1.52 $ per kg_H2 and 1.64 $ per kg_H2 in solar-rich regions in Australia and the United States by 2050, respectively. Furthermore, the hydrogen cost is primarily influenced by regional factors and specific application scenarios, and the minimum production, delivery, and supply cost of hydrogen for refuelling cars in Shanghai is 7.68 $ per kg_H2, which might be potentially lowered to 5.68 $ per kg_H2 by 2030 and 4.08 $ per kg_H2 by 2050. Our findings offer both technological and economic insights into the global large-scale hydrogen energy applications in the future based on this new PV-SOEC-MgH₂ technical route.