Overview and prospects of low-emissions hydrogen (H2) energy systems: Roadmap for a sustainable H2 economy

Hydrogen (H2) has a big role to play in energy transition to achieve net-zero carbon emissions by 2050. For H2 to compete with other fuels in the energy market, more research is required to mitigate key issues like greenhouse gas (GHG) emissions, safety, and end-use costs. For these reasons, a software-supported technical overview of H2 production, storage, transportation, and utilisation is introduced. Drawbacks and mitigation approaches for H2 technologies were highlighted. The recommended areas include solar thermal or renewable-powered plasma systems for feedstock preheating and oxy-hydrogen combustion to meet operating temperatures and heat duties due to losses; integration of electrolysis of H2O into hydrocarbon reforming methods to replace air separation unit (ASU); use of renewable power sources for electrical units and the introduction of thermoelectric units to maximise the overall efficiency. Furthermore, a battolyser system for small-scale energy storage; new synthetic hydrides with lower absorption and desorption energy; controlled parameters and steam addition to the combustor/cylinder and combustors with fitted heat exchangers to reduce emissions and improve the overall efficiency are also required. This work also provided detailed information on any of these systems implementations based on location factors and established a roadmap for H2 production and utilisation. The proposed H2 production technologies are hybrid pyrolysis-electrolysis and integrated AD-MEC and DR systems using renewable, bioelectrochemical and low-carbon energy systems. Production and utilisation of synthetic natural gas (NG) using renewable-powered electrolysis of H2O, oxy-hydrogen and direct air capture (DAC) is another proposed H2 energy system for a sustainable H2 economy. By providing these factors and information, researchers can work towards pilot development and further efficiency enhancement.