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This study proposes a novel wind-hydrogen coupled poly generation system. The system consists of alkaline electrolyzers, fuel cells (FC), organic Rankine cycle (ORC), hydrogen compressors, hydrogen turbines, pumps and storage tanks. By the multistage utilization of the waste heat, more electricity, hydrogen and heat energy are provided to the user, and improve the operating conditions of the equipment. The effects of multiple parameters on the system's exergy efficiency and destruction are discussed. The economic and environmental of the system are evaluated. The results show that rising the electrolyzer operating temperatures and ambient temperatures can slightly improve the system's exergy efficiency. Increasing FC operating temperature, the exergy efficiency of FC-ORC and the system rapidly increased to 51.91 % and 58.83 %, respectively. By increasing the hydrogen storage pressure, the system exergy efficiency increases by 6.87 %. The static payback period of the poly generation system is 7.3 years. [Display omitted] • By multistage use of waste heat, solve the problem of system's low exergy efficiency. • The working temperature of FC significantly affects the system's exergy efficiency. • Static payback period of the wind-hydrogen poly generation system is 7.3 years. [ABSTRACT FROM AUTHOR]

Underground hydrogen storage (UHS) is recognized as one of the most promising ways to achieve large-scale long-term storage of hydrogen, and bridge the gap between demand and supply of the renewable energy sources. Recent studies show that depleted shale gas reservoirs might also be a favorable candidate for hydrogen storage because of its unique adsorption and sealing capacities. However, the interaction of hydrogen-cushion gas-water in shale is still unclear, and there is a lack of research revealing the transport mechanisms of their mixtures in shale nanopores. Here, we used the molecular dynamics simulations to investigate the hydrogen-methane transport through Na-montmorillonite clay (i.e. a common clay mineral in shale) in the presence of water. The effect of pore size, water content and driving pressure gradient on fluid behavior was discussed. The results show that: (i) The pores prefer to adsorb water molecules and form water films near the pore walls. If the water content is below 10%, it can be considered to increase the proportion of cushion gas to reduce the adsorption loss of hydrogen. (ii) When the water content increases from 10% to 50%, the thickness of water film in the pores increases by 2–3 times, and the self-diffusion coefficient of hydrogen decreases more than that of methane. (iii) The increased pressure gradient promotes the desorption of water molecules, and results in an increased amount of hydrogen accumulating near the pore walls. The results in the study provide deep insights into how hydrogen-methane mixtures transport through clay nanopores, which is important for enhancing experimental and modelling design aimed at improving hydrogen injection and production efficiency in shale. • Molecular dynamics simulation is used to study hydrogen-methane flow in nanopores. • The presence of water and methane can reduce hydrogen loss caused by clay adsorption. • The diffusion of hydrogen is more sensitive to changes in water than methane under low water content. • The impact of pressure gradient on fluid behavior is related to water content and pore sizes. [ABSTRACT FROM AUTHOR]