China, People’s Republic

This study employs first principles calculations and thermodynamic analyses to investigate the dissociative adsorption of hydrogen on the Fe(110) surface. The results show that the adsorption energies of hydrogen at different sites on the iron surface are −1.98 eV (top site) −2.63 eV (bridge site) and −2.98 eV (hollow site) with the hollow site being the most stable adsorption position. Thermodynamic analysis further reveals that under operational conditions of 25 ◦C and 12 MPa the Gibbs free energy change (∆G) for hydrogen dissociation is −1.53 eV indicating that the process is spontaneous under pipeline conditions. Moreover as temperature and pressure increase the spontaneity of the adsorption process improves thus enhancing hydrogen transport efficiency in pipelines. These findings provide a theoretical basis for optimizing hydrogen transport technology in natural gas pipelines and offer scientific support for mitigating hydrogen embrittlement improving pipeline material performance and developing future hydrogen transportation strategies and safety measures.

Under the dual pressures of global climate change and energy structure transition the offshore wind–solar–current energy coupling hydrogen production (OCWPHP) system has emerged as a promising integrated energy solution. However its complex multi-energy structure and harsh marine environment introduce systemic risks that are challenging to assess comprehensively using traditional methods. To address this we develop a novel risk assessment framework based on hesitant fuzzy sets (HFS) establishing a multidimensional risk criteria system covering economic technical social political and environmental aspects. A hybrid weighting method integrating AHP entropy weighting and consensus adjustment is proposed to determine expert weights while minimizing risk information loss. Two aggregation operators—AHFOWA and AHFOWG—are applied to enhance uncertainty modeling. A case study of an OCWPHP project in the East China Sea is conducted with the overall risk level assessed as “Medium.” Comparative analysis with the classical Cumulative Prospect Theory (CPT) method shows that our approach yields a risk value of 0.4764 closely aligning with the CPT result of 0.4745 thereby confirming the feasibility and credibility of the proposed framework. This study provides both theoretical support and practical guidance for early-stage risk assessment of OCWPHP projects.

Due to the random fluctuations in power experienced by high-temperature green electric hydrogen production systems further deterioration of spatial distribution characteristics such as temperature voltage/current and material concentration inside the solid oxide electrolysis cell (SOEC) stack may occur. This has a negative impact on the system’s flexibility and the corresponding control capabilities. In this paper based on the SOEC electrolytic cell model a comprehensive optimization method using an adaptive incremental Kriging surrogate model is proposed. The reliability of this method is verified by accurately analyzing the dynamic performance of the SOEC and the spatial characteristics of various physical quantities. Additionally a thermal dynamic analysis is performed on the SOEC and an adaptive time-varying LPV-MPC optimization control method is established to ensure the temperature stability of the electrolysis cell stack aiming to maintain a stable efficient and sustainable SOEC operation. The simulation analysis of SOEC hydrogen production adopting a variable load operation has demonstrated the advantages of this method over conventional PID control in stabilizing the temperature of the stack. It allows for a rapid adjustment in the electrolysis voltage and current and improves electrolysis efficiency. The results highlighted that the increase in the electrolysis load increases the current density while the water vapor electrolysis voltage and H2 flow rate significantly decrease. Finally the SOEC electrolytic hydrogen production module is introduced for optimization scheduling of energy consumption in Xinjiang China. The findings not only confirmed that the SOEC can transition to the current load operating point at each scheduling period but also demonstrated higher effectiveness in stabilizing the stack temperature and improving electrolysis efficiency.

This article takes the perspective of Hydrogen Load Aggregator (HLA) to optimize the declaration strategy of peak shaving market improve the flexible regulation capability of power system and HLA economy as the research objectives and proposes an optimization strategy method for HLA to participate in peak shaving market. Firstly an improved Convolutional Neural Networks–Long Short-Term Memory (CNN-LSTM) time series prediction model is developed to address peak shaving demand uncertainty. Secondly a bidding strategy model incorporating dynamic pricing is constructed by comprehensively considering electrolyzer regulation costs market supply–demand relationships and system constraints. Thirdly a market clearing model for peak shaving markets with HLA participation is designed through analysis of capacity contribution and marginal costs among different regulation resources. Finally the capacity allocation model is designed with the goal of minimizing the total cost of peak shaving among various stakeholders within HLA and the capacity won by HLA in the peak shaving market is reasonably allocated. Simulations conducted on a Python3.12-based experimental platform demonstrate the following: the improved CNN-LSTM model exhibits strong adaptability and robustness the bidding model effectively enhances HLA market competitiveness and the clearing model reduces system operator costs by 5.64%.

Due to the environmental impact of fossil fuels renewable energy such as wind and solar energy is rapidly developed. In energy systems energy storage units are important which can regulate the safe and stable operation of the power system. However different energy storage methods have different environmental and economic impacts in renewable energy systems. This paper proposed three different energy storage methods for hybrid energy systems containing different renewable energy including wind solar bioenergy and hydropower meanwhile. Based on Homer Pro software this paper compared and analyzed the economic and environmental results of different methods in the energy system through the case of a residential community in Baotou City. The result showed that (1) the use of batteries as energy storage in communities posed the lowest energy costs whose NPC was $197396 and LCOE was $0.159 consisting of 20 batteries 19.3 kW PV 6 wind turbines a 12.6 kW converter. (2) Lower fuel cell prices mean lower NPC and the increase in the Electric Load Scaled Average implied a decrease in LCOE and the increase of the NPC. (3) The use of fuel cells also had impacts on the environment such as resulting CO2 and SO2.

Enhancing the economics of microgrid systems and achieving a balance between energy supply and demand are critical challenges in capacity allocation research. Existing studies often neglect the optimization of electrolyzer efficiency and multi-stack operation leading to inaccurate assessments of system benefits. This paper proposes a capacity allocation model for wind-PV-hydrogen integrated microgrid systems that incorporates hydrogen production efficiency optimization. This paper analyzes the relationship between the operating efficiency of the electrolyzer and the output power regulates power generation-load mismatches through a renewable energy optimization model and establishes a double-layer optimal configuration framework. The inner layer optimizes electrolyzer power allocation across periods to maximize operational efficiency while the outer layer determines configuration to maximize daily system revenue. Based on the data from a demonstration project in Jiangsu Province China a case study is conducted to verify that the proposed method can improve system benefits and reduce hydrogen production costs.

Solar-driven water electrolysis has emerged as a prominent technology for the production of green hydrogen facilitated by advancements in both water electrolyzers and solar cells. Nevertheless the majority of integrated solar-to-hydrogen systems still struggle to exceed 20% efficiency particularly in large-scale applications. This limitation arises from suboptimal coupling methodologies and system-level inefficiencies that have rarely been analyzed. To address these challenges this study investigates the fundamental principles of solar hydrogen production and examines key energy losses in photovoltaic-electrolyzer systems. Subsequently it systematically discusses optimization strategies across three dimensions: (1) enhancing photovoltaic (PV) system output under variable irradiance (2) tailoring electrocatalysts and electrolyzer architectures for high-performance operation and (3) minimizing coupling losses through voltage-matching technologies and energy storage devices. Finally we review existing large-scale solar hydrogen infrastructure and propose strategies to overcome barriers related to cost durability and scalability. By integrating material innovation with system engineering this work offers insights to advance solar-powered electrolysis toward industrial applications.

China’s dual-carbon goals have positioned hydrogen as a central pillar of its energy transition. This review examines the recent development of China’s hydrogen supply chain with particular focus on manufacturing technologies for alkaline electrolysers high-pressure cylinders and diaphragm compressors. In 2024 China produced 36.5 million tons of hydrogen of which 77 % was grey and only 1 % derived from electrolysis. Storage and transportation account for nearly 30 % of end-use costs while reliance on imported compressors increases refuelling station expenses by approximately 40 %. We identify key bottlenecks including limited electrolyser efficiency the high cost of carbon fibres for Type III/IV cylinders and insufficient domestic capacity for highreliability compressors. To address these challenges targeted advances are proposed: membrane materials with engineered hydrophilicity advanced surface modifications and hydrophilic inhibitors; liner design incorporating grooved-liner braided layers with double-fibre configurations; and a three-layer diaphragm compressor architecture. By consolidating fragmented studies this review provides the integrated manufacturing perspective on China’s hydrogen supply chain offering both scientific insights and practical guidance for accelerating costeffective large-scale low-carbon hydrogen deployment.

The blending of hydrogen significantly impacts the diffusion and safety characteristics of natural gas within indoor environments. This study employs ANSYS Fluent 2021 R1 to numerically investigate the diffusion and ventilation characteristics of hydrogen-blended natural gas (HBNG) leakage in indoor spaces. A physical and mathematical model of gas leakage from pipelines is established to study hazardous areas flammable regions ventilation characteristics alarm response times safe ventilation rates and the concentration distribution of leaked gas. The effects of hydrogen blending ratio (HBR) ventilation conditions and space dimensions on leakage diffusion and safety are analyzed. Results indicate that HBNG leakage forms vertical concentration stratification in indoor spaces with ventilation height being negatively correlated with gas concentration and flammable regions. In the indoor space conditions of this study by improving ventilation conditions the hazardous area can be reduced by up to 92.67%. Increasing HBR substantially expands risk zones—with pure hydrogen producing risk volumes over five times greater than natural gas. Mechanical ventilation significantly enhances indoor safety. Safe ventilation rates escalate with hydrogen content providing quantitative safety criteria for HBNG implementation. The results underscore the critical influence of HBR and ventilation strategy on risk assessment providing essential insights for the safe indoor deployment of HBNG.

From an environmental standpoint carbon-free energy carriers such as ammonia and hydrogen are essential for future energy systems. However their hightemperature chemical behavior remains insufficiently understood posing challenges for the development and optimization of advanced combustion technologies. Ammonia in particular is globally available and cost-effective especially for energy-intensive industries. The addition of ammonia or hydrogen to methane significantly reduces the accuracy of existing predictive models. Therefore validated and detailed data are urgently needed to enable reliable design and performance predictions. This review highlights the compatibility of ammonia with existing combustion infrastructure facilitating a smoother transition to more sustainable heating methods without the need for entirely new systems. Applications in high-temperature heating processes such as metal processing ceramics and glass production and power generation are of particular interest. This review focuses on the systematic assessment of alternative fuel mixtures comprising ammonia and hydrogen as well as natural gas with particular consideration of existing safety-related parameters and combustion characteristics. Fundamental quantities such as the laminar burning velocity are discussed in the context of their relevance for fuel mixtures and their scalability toward turbulent flame propagation which is of critical importance for industrial burner and reactor design. The influence of fuel composition on ignition limits is examined as these are essential parameters for safety margin definitions and operational boundary conditions. Furthermore flame stability in mixed-fuel systems is addressed to evaluate the practical feasibility and robustness of combustion under varying process conditions. A detailed overview of current diagnostic and analysis methods follows encompassing both pollutant measurement techniques and the detection of key radical species. These diagnostics form the experimental basis for reaction kinetics modeling and mechanism validation. Given the importance of emission formation in combustion systems a dedicated subsection summarizes major emission trends even though a comprehensive treatment would exceed the scope of this review. Thermal radiation effects which are highly relevant for heat transfer and system efficiency in large-scale applications are then reviewed. In parallel current developments in numerical simulation approaches for industrial-scale combustion systems are presented including aspects of model accuracy boundary conditions and computational efficiency. The review also incorporates insights from materials engineering particularly regarding high-temperature material performance corrosion resistance and compatibility with combustion products. Based on these interdisciplinary findings operational strategies for high-temperature furnaces are outlined and selected industrial reference systems are briefly presented. This integrated approach aims to support the design optimization and safe operation of next-generation combustion technologies utilizing carbon-free or low-carbon fuels.

As global awareness of environmental protection increases hydrogen is seen as a promising solution due to its high energy density and zero-emission combustion. The PEM electrolyze combined with renewable energy power generation is an effective method to solve the problem of hydrogen production. The market competitiveness of PEM electrolyte will be enhanced in the future and the equipment cost can be reduced by 35.8%. The fast dynamic response performance of PEM electrolyzes especially during start-up and shutdown affects system flexibility and stability. The 190 Nm3/h test platform is established to study the fast dynamic response performance considering the cold startup thermal start-up and shutdown behaviors. The results shown that the 190 Nm³/h PEM electrolyze required 6340 s to achieve cold start-up 1100 s to achieve thermal start-up and 855 s to complete shutdown. When operating stably the temperature fluctuation of the PEM remains below 5 °C demonstrating the excellent temperature control performance. However during cold start-up and shutdown the concentrations of hydrogen and oxygen fluctuate significantly which can easily lead to a decrease in system performance. These findings provide guidance for optimizing the design and operating parameters of PEM Electrolyze systems.

Integrated Hydrogen–Energy Systems (IHES) have attracted widespread attention; however distributed energy sources such as photovoltaics (PV) and wind turbines (WT) within these systems exhibit significant uncertainty and intermittency posing key challenges to scheduling complexity and system instability. As a core mechanism for the integrated operation of IHES electricity price regulation can promote the absorption of renewable energy optimize resource allocation and enhance operational economy. Nevertheless uncertainties in IHES hinder the formulation of accurate electricity prices which easily lead to delays in scheduling responses and an increase in cumulative operating costs. To address these issues this study develops lifespan models for Proton Exchange Membrane Electrolyzers (PEMELs) and Proton Exchange Membrane Fuel Cells (PEMFCs) constructs dynamic equations for the demand side and response side and proposes a fuzzy-weighted dynamic pricing strategy. Simulation results show that compared with fixed pricing the proposed dynamic pricing strategy reduces economic indicators by an average of 15.3% effectively alleviates energy imbalance and optimizes the energy supply of components. Additionally it reduces the lifespan degradation of PEMELs by 21.59% and increases the utilization rate of PEMFCs by 54.8%.

To effectively address the issues of curtailed wind and photovoltaic (PV) power caused by the high proportion of renewable energy integration and to promote the clean and lowcarbon transformation of the energy system this paper proposes a “chemical–mechanical” dual-pathway synergistic mechanism for the reversible solid oxide cell (RSOC) and flywheel energy storage system (FESS) electricity–hydrogen hybrid system. This mechanism aims to address both short-term and long-term energy storage fluctuations thereby minimizing economic costs and curtailed wind and PV power. This synergistic mechanism is applied to regulate system operations under varying wind and PV power output and electricity–hydrogen load fluctuations across different seasons thereby enhancing the power generation system’s ability to integrate wind and PV energy. An economic operation model is then established with the objective of minimizing the economic costs of the electricity–hydrogen hybrid system incorporating RSOC and FESS. Finally taking a large-scale new energy industrial park in the northwest region as an example case studies of different schemes were conducted on the MATLAB platform. Simulation results demonstrate that the reversible solid oxide cell (RSOC) system—integrated with a FESS and operating under the dual-path coordination mechanism—achieves a 14.32% reduction in wind and solar curtailment costs and a 1.16% decrease in total system costs. Furthermore this hybrid system exhibits excellent adaptability to the dynamic fluctuations in electricity– hydrogen energy demand which is accompanied by a 5.41% reduction in the output of gas turbine units. Notably it also maintains strong adaptability under extreme weather conditions with particular effectiveness in scenarios characterized by PV power shortage.

As hydrogen fuel cell vehicles gain momentum as crucial zero-emission transportation solutions the urgency to address hydrogen permeability through the polymer liner becomes paramount for ensuring the safety efficiency and longevity of Type IV hydrogen storage tanks. This paper synthesizes existing research findings analyzes the influence of different materials and structures on gas permeability elucidates the dissolution and diffusion mechanisms of hydrogen in plastic liners and discusses their engineering applications. We focus on measurement methods influencing factors and improvement strategies for liner gas permeability. Additionally we explore the prospects of Type IV hydrogen storage tanks in fields such as automotive aerospace and energy storage industries. Through this comprehensive review of liner gas permeability critical insights are provided to guide the development of efficient and safe hydrogen storage and transportation systems. These insights are vital for advancing the widespread application of hydrogen energy technology and fostering sustainable energy development significantly contributing to efforts aimed at enhancing the performance and safety of Type IV hydrogen storage tanks.

Proton exchange membrane water electrolyzers (PEMWEs) are a promising technology for large-scale hydrogen production yet their industrial deployment is hindered by the harsh acidic conditions and sluggish oxygen evolution reaction (OER) kinetics. This review provides a comprehensive analysis of recent advances in iridium-based electrocatalysts (IBEs) emphasizing novel optimization strategies to enhance both catalytic activity and durability. Specifically we critically examine the mechanistic insights into OER under acidic conditions revealing key degradation pathways of Ir species. We further highlight innovative approaches for IBE design including (i) morphology and support engineering to improve stability (ii) structure and phase modulation to enhance catalytic efficiency and (iii) electronic structure tuning for optimizing interactions with reaction intermediates. Additionally we assess emerging electrode engineering strategies and explore the potential of non-precious metal-based alternatives. Finally we propose future research directions focusing on rational catalyst design mechanistic clarity and scalable fabrication for industrial applications. By integrating these insights this review provides a strategic framework for advancing PEMWE technology through highly efficient and durable OER catalysts.

Hydrogen is increasingly recognized as a clean energy alternative offering effective storage solutions for widespread adoption. Advancements in storage electrolysis and fuel cell technologies position hydrogen as a pathway toward cleaner more efficient and resilient energy solutions across various sectors. However challenges like infrastructure development cost-effectiveness and system integration must be addressed. This review comprehensively examines above-ground hydrogen storage technologies and their applications. It highlights the importance of established hydrogen fuel cell infrastructure particularly in gaseous and LH2 systems. The review favors material-based storage for medium- and long-term needs addressing challenges like adverse thermodynamics and kinetics for metal hydrides. It explores hydrogen storage applications in mobile and stationary sectors including fuel-cell electric vehicles aviation maritime power generation systems off-grid stations power backups and combined renewable energy systems. The paper underscores hydrogen’s potential to revolutionize stationary applications and co-generation systems highlighting its significant role in future energy landscapes.

The development of new energy vehicles particularly electric vehicles (EVs) and hydrogen fuel cell vehicles (HFCVs) represents a strategic initiative to address climate change and foster sustainable development. Integrating PV with hydrogen production into hybrid electricity-hydrogen energy stations enhances land and energy efficiency but introduces scheduling challenges due to uncertainties. A multi-time scale scheduling framework which includes day-ahead and intraday optimization is established using fuzzy chance-constrained programming to minimize costs while considering the uncertainties of PV generation and charging/refueling demand. Correspondingly trapezoidal membership function and triangular membership function are used for the fuzzy quantification of day-ahead and intraday predictions of photovoltaic power generation and load demands. The system achieves 29.37% lower carbon emissions and 17.73% reduced annualized costs compared to day-ahead-only scheduling. This is enabled by real-time tracking of PV/load fluctuations and optimized electrolyzer/fuel cell operations maximizing renewable energy utilization. The proposed multi-time scale framework dynamically addresses short-term fluctuations in PV generation and load demand induced by weather variability and temporal dynamics. By characterizing PV/load uncertainties through fuzzy methods it enables formulation of chance-constrained programming models for operational risk quantification. The confidence level – reflecting decision-makers’ reliability expectations – progressively increases with refined temporal resolution balancing economic efficiency and operational reliability.

Green hydrogen is emerging as a pivotal energy carrier in the global transition toward decarbonization offering a sustainable alternative to fossil fuels in sectors such as heavy industry transportation power generation and long-duration energy storage. Despite its potential large-scale deployment remains hindered by significant economic technological and infrastructure challenges. Current production costs for green hydrogen range from USD 3.8 to 11.9/kg H2 significantly higher than gray hydrogen at USD 1.5–6.4/kg H2 due to high electricity prices and electrolyzer capital costs exceeding USD 2000 per kW. This review critically examines the key bottlenecks in green hydrogen production focusing on water electrolysis technologies electrocatalyst limitations and integration with renewable energy sources. The economic viability of green hydrogen is constrained by high electricity consumption capital-intensive electrolyzer costs and operational inefficiencies making it uncompetitive with fossil fuel-based hydrogen. Infrastructure and supply chain challenges including limited hydrogen storage transport complexities and critical material dependencies further restrict market scalability. Additionally policy and regulatory gaps disparities in financial incentives and the absence of a standardized certification framework hinder international trade and investment in green hydrogen projects. This review also highlights market trends and global initiatives assessing the role of government incentives and cross-border collaborations in accelerating hydrogen adoption. While technological advancements and cost reductions are progressing overcoming these challenges requires sustained innovation stronger policy interventions and coordinated efforts to develop a resilient scalable and cost-competitive green hydrogen sector.

Hydrogen fuel cell vehicles (HFCVs) are vital for advancing the hydrogen economy and decarbonizing the transportation sector. However research on HFCV market dynamics in passenger vehicles is limited especially incorporating both market competition from other vehicle types and the comprehensive supply–demand market dynamics. To bridge this gap our study proposed a spatial agent-based model to simulate the HFCV market evolution with the aim of finding effective strategies and policy implications for breaking the diffusion dilemma of the HFCV market. We calibrated the model using survey data (N=1065) collected from Beijing and evaluated its performance across five “What-If” scenarios. Results indicate that HFCVs and hydrogen stations are difficult to penetrate under the current conditions despite HFCV applicants and market share growing by 37.5% and 15.63% respectively. Consumer perceptions on cost social and environment have greater impacts on HFCV proliferation than facility availability. The HFCV purchase subsidy has much greater impact than the technological learning rate greatly accelerating its market emergence timing. Finally HFCVs’ diffusion significantly influences the market of battery electric vehicles.

Ocean islands possess abundant renewable energy resources providing favorable conditions for developing offshore clean energy microgrids. However geographical isolation poses significant challenges for direct energy transfer between islands. Recent electrolysis and hydrogen storage technology advancements have created new opportunities for distributed energy utilization in these remote areas. This paper presents a low-carbon economic dispatch strategy designed explicitly for distant oceanic islands incorporating energy self-sufficiency rates and seasonal hydrogen storage (SHS). We propose a power supply model for offshore islands considering hydrogen production from offshore wind power. The proposed model minimizes operational and carbon emission costs while maximizing energy self-sufficiency. It considers the operational constraints of the island’s energy system the offshore transportation network the hydrogen storage infrastructure and the electricityhydrogen-transportation coupling of hydrogen storage (HS) and seasonal hydrogen storage (SHS) services. To optimize the dispatch process this study employs an improved Grey Wolf Optimizer (IGWO) combined with the Differential Evolution method to enhance population diversity and refine the position updating mechanism. Simulation results demonstrate that integrating HS and SHS effectively enhances energy self-sufficiency and reduces carbon emissions. For instance hydrogenation costs decreased by 21.4% after optimization and the peak-valley difference was reduced by 16%. These findings validate the feasibility and effectiveness of the proposed approach.

Underground hydrogen storage in aquifers is a promising solution to address the imbalance between energy supply and demand yet its practical implementation requires optimized strategies to ensure high efficiency and economic viability. To improve the storage and production efficiency of hydrogen it is essential to select the appropriate cushion gas and to study the influence of reservoir and process parameters. Based on the conceptual model of aquifer with single-well injection and production three potential cushion gas (carbon dioxide nitrogen and methane) were studied and the changes in hydrogen recovery for each cushion gas were compared. The effects of temperature initial pressure porosity horizontal permeability vertical to horizontal permeability ratio permeability gradient hydrogen injection rate and hydrogen production rate on the purity of recovered hydrogen were investigated. Additionally the impact of different well pattern on the purity of recovered hydrogen was studied. The results indicate that methane is the most effective cushion gas for improving hydrogen recovery in UHS. Different well patterns have significant impacts on the purity of recovered hydrogen. The mole fractions of methane in the produced gas for the single-well line-drive pattern and five-spot pattern were 16.8% 5% and 3.05% respectively. Considering the economic constraints the five-spot well pattern is most suitable for hydrogen storage in aquifers. Reverse rhythm reservoirs with smaller permeability differences should be chosen to achieve relatively high hydrogen recovery and purity of recovered hydrogen. An increase in hydrogen production rate leads to a significant decrease in the purity of the recovered hydrogen. In contrast hydrogen injection rate has only a minor effect. These findings provide actionable guidance for the selection of cushion gas site selection and operational design of aquifer-based hydrogen storage systems contributing to the large-scale seasonal storage of hydrogen and the balance of energy supply and demand.

The use of rare earth elements in hydrogen storage processes offers significant advantages in terms of increasing technological efficiency and ensuring system security. However this process also creates some serious problems in terms of environmental and economic sustainability. It is necessary to determine the most critical indicators affecting the sustainable use of these elements. Studies on this subject in the literature are quite limited and this may lead to wrong investment decisions. The main purpose of this study is to determine the most important indicators to increase the sustainable use of rare earth elements in hydrogen storage processes. An original decision-making model in which Siamese network logarithmic percentage-change driven objective weighting (LOPCOW) fractal fuzzy numbers and weighted influence super matrix with precedence (WISP) approaches are integrated in the study. This study provides an original contribution to the literature by identifying the most critical indicators affecting the sustainable use of rare earths in hydrogen storage processes by presenting an innovative model. Fractal structures such as Koch Snowflake Cantor Dust and Sierpinski Triangle can model complex uncertainties more successfully. Fractal structures are particularly effective in modeling linguistic fuzziness because their recursive nature closely mirrors the layered and imprecise way humans often express subjective judgments. Unlike linear fuzzy sets fractals can capture the patterns of ambiguity found in expert evaluations. Hydrogen storage capacity and government supports are determined as the most vital criteria affecting sustainability in rare earth use.

Driven by the global energy transition and the dual carbon goals developing low-carbon and zero-carbon alternative fuels has become a core issue for sustainable development in the internal combustion engine sector. Ammonia is a promising zero-carbon fuel with broad application prospects. However its inherent combustion characteristics including slow flame propagation high ignition energy and narrow flammable range limit its use in internal combustion engines necessitating the addition of auxiliary fuels. To address this issue this paper proposes a composite injection technology combining “ammonia duct injection + hydrogen cylinder direct injection.” This technology utilizes highly reactive hydrogen to promote ammonia combustion compensating for ammonia’s shortcomings and enabling efficient and smooth engine operation. This study based on bench testing investigated the effects of hydrogen direct injection timing (180 170 160 150 140◦ 130 120 ◦CA BTDC) hydrogen direct injection pressure (4 5 6 7 8 MPa) on the combustion and emissions of the ammonia–hydrogen engine. Under hydrogen direct injection timing and hydrogen direct injection pressure conditions the hydrogen mixture ratios are 10% 20% 30% 40% and 50% respectively. Test results indicate that hydrogen injection timing that is too early or too late prevents the formation of an optimal hydrogen layered state within the cylinder leading to prolonged flame development period and CA10-90. The peak HRR also exhibits a trend of first increasing and then decreasing as the hydrogen direct injection timing is delayed. Increasing the hydrogen direct injection pressure to 8 MPa enhances the initial kinetic energy of the hydrogen jet intensifies the gas flow within the cylinder and shortens the CA0-10 and CA10-90 respectively. Under five different hydrogen direct injection ratios the CA10- 90 is shortened by 9.71% 11.44% 13.29% 9.09% and 13.42% respectively improving the combustion stability of the ammonia–hydrogen engine.

Activated carbon as a hydrogen storage material possesses advantages such as low cost high safety lightweight and good cycling performance. Zhundong coal characterized by low calorific value high volatility and elevated reaction activity stands out as an exceptional raw material for the production of activated carbon. This study employed Zhundong coal for the synthesis of hydrogen storage activated carbon exploring the impact of acid treatment and varied activation conditions on Zhundong coal. The specific surface area of sample ZD-HK3-AC is 1980 m2 /g and the gravimetric hydrogen storage density reaches 0.91 wt% under the condition of 80bar at room temperature. The adsorption–desorption isotherms nearly overlapped demonstrating excellent cycling performance and high mechanical strength. At the same time the relationship between the pore structure parameters of activated carbon and hydrogen storage density was explored revealing the mechanism of activated carbon adsorption and hydrogen storage. These findings hold significant guiding implications for the preparation and research of hydrogen storage materials utilizing activated carbon.

The gas equation of state (EOS) serves as a critical tool for analyzing the thermal effects within the hydrogen storage tank during refueling processes. It quantifies the dynamic relationships among pressure temperature and volume playing a vital role in numerical simulations of hydrogen refueling the development of refueling protocols and ensuring refueling safety. This study first establishes a lumped-parameter thermodynamic model for the hydrogen refueling process which combines a zero-dimensional gas model with a one-dimensional tank wall model (0D1D). The model’s accuracy was validated against experimental data and will be used in combination with different EOSs to simulate hydrogen temperature and pressure. Subsequently parameter values are derived for the van der Waals EOS and its modified forms—Redlich–Kwong Soave and Peng–Robinson. The accuracy of the modified forms is evaluated using the Joule–Thomson inversion curve. A polynomial EOS is formulated and its parameters are numerically determined. Finally the hydrogen temperatures and pressures calculated using the van der Waals EOS Redlich– Kwong EOS polynomial EOS and the National Institute of Standards and Technology (NIST) database are compared. Within the initial and boundary conditions set in this study the results indicate that among the modified forms for van der Waals EOS the Redlich– Kwong EOS exhibits higher accuracy than the Soave and Peng–Robinson EOSs. Using the NIST-calculated hydrogen pressure as a benchmark the relative error is 0.30% for the polynomial EOS 1.83% for the Redlich–Kwong EOS and 17.90% for the van der Waals EOS. Thus the polynomial EOS exhibits higher accuracy followed by the Redlich–Kwong EOS while the van der Waals EOS demonstrates lower accuracy. This research provides a theoretical basis for selecting an appropriate EOS in numerical simulations of hydrogen refueling processes.