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With the development of energy technology, hydrogen is gradually becoming widely used. China is also rapidly developing its own hydrogen energy industry in an effort to accomplish the "dual carbon target'. Hydrogen from methane is one of the mainstream sources, of which hydrogen from methane cracking is the decomposition of methane into hydrogen and solid carbon, with the solid carbon also having a high economic value. In particular, this technology does not emit carbon dioxide, which is very friendly to the environment, but it cannot avoid larger energy consumption. In contrast, hydrogen production from methane cracking driven by solar energy not only combines the characteristics of no CO 2 emission, but also greatly reduces the consumption of primary energy, which is the future development trend of hydrogen production from methane. This paper provides a brief overview of the various technological pathways for methane to hydrogen production in the context of China's actual development, focusing on the current status of the development and application of solar methane cracking to hydrogen production technologies at home and abroad. Among them, this paper mainly discusses the characteristics of solar reactors of different sizes and structures, and summarizes the results of related optimization studies. Meanwhile, the application of catalysts in solar reactors and the problem of carbon deposition are analyzed, and the practical application of solar methane cracking hydrogen production system is outlined. Finally, the future development of solar methane cracking hydrogen production technology is prospected from the national situation of China. [Display omitted] • Solar methane cracking for hydrogen can reduce emissions and energy consumption. • The current state of research on solar reactors is summarized. • Solar methane cracking requires higher performing catalysts. • Providing insights into the future development of solar methane cracking in China. [ABSTRACT FROM AUTHOR]

As the global shipping industry experiences rapid expansion, the imperative to address greenhouse gas emissions and environmental impact becomes increasingly paramount. Hydrogen has emerged as a pivotal and eco-friendly energy source, offering a pathway towards carbon neutrality and a complete zero-carbon transition in maritime operations. However, the widespread adoption of hydrogen-powered ships hinges on the establishment of robust regulations and technical standards. This paper conducts a comprehensive examination of hydrogen fuel cell (FC) technology in ships, scrutinizing the role of international classification societies and exploring existing standards and regulations within the maritime industry, specifically centered around hydrogen energy. The study outlines a strategic developmental roadmap for a green shipping hydrogen energy system tailored for hydrogen FC-powered ships in China. Emphasizing the differences in hydrogen application between fuel cell vehicles and ships, the paper elucidates technical challenges unique to hydrogen FC-powered ships. Furthermore, it proposes a visionary framework for future technical standards, advocating for the creation of a ship-based hydrogen energy standard system, the development of core technical standards, and a heightened focus on safety regulations. Through comprehensive analysis and compelling argumentation on hydrogen fuel cell ship technology and standards, this paper underscores the indispensable role that technical standards play in propelling the advancement of environmentally friendly shipping. Beyond serving as an informative resource, the paper aims to provide valuable guidance and direction for the future demonstration, application, and promotion of hydrogen fuel cell ship technology. Ultimately, it underscores the pivotal role of technical standards in advancing sustainable maritime transportation. • Analyze hydrogen energy technical standards from the production, storage, safety. • Comparison of hydrogen energy technical differences between vehicles and ships. • Outline the unique challenges of applying hydrogen technology to ship operations. • Constructed a technical standard framework for future hydrogen energy ships. [ABSTRACT FROM AUTHOR]

This study presents a bibliometric review focusing on the utilization of water electrolysis as a means of generating hydrogen as an energy carrier. The analysis includes research conducted over the past decade, covering from 2014 to 2023 (till August). Several key aspects are highlighted, including publication trends, the leading country in research output, journal rankings, and a citation analysis of papers related to water electrolysis. The findings reveal a notable increase in publication trends, with China emerging as the leading contributor in this research area. Furthermore, the International Journal of Hydrogen Energy is identified as the highest-ranked journal in terms of both publication number and citation impact. Additionally, the top ten most cited research articles and review papers are investigated to determine their influence within the field. To gain a deeper understanding of water electrolysis methods, the three primary approaches: alkaline water electrolysis (AWE), proton exchange membrane (PEM) electrolysis, and solid oxide electrolysis (SOE) is examined. The analysis emphasizes that PEM electrolysis is the most prevalent method for hydrogen generation, particularly when integrated with renewable energy sources such as solar and wind power due to its rapid response to electrical input fluctuation. Finally, the challenges and future directions of water electrolysis in hydrogen production are highlighted, including an exploration of economic and environmental considerations at large scale, offering insights into the path forward for advancing this technology sustainably. • A comprehensive bibliometric analysis of water electrolysis for hydrogen production. • Publication trends, journal rankings, and citation analysis are highlighted. • China is identified as the leading contributor in water electrolysis publications. • International Journal of Hydrogen Energy: the highest-ranked journal in this field. • Specific electrolysis methods, including AWE, PEM, and SOE are examined. [ABSTRACT FROM AUTHOR]

This paper precisely estimates the looming demand for hydrogen within the transportation sector, spanning 14 pivotal G20 nations from 2022 to 2050, anchored in the global vehicle hydrogen market penetration rate. Employing a robust techno-economic modeling methodology and leveraging Geographic Information System (GIS) for enriched visualization, it unveils distinct environmental dividends across three thoughtfully devised scenarios: Business- as -Usual, Moderate, and Aggressive. Findings herald India and China as pinnacles of hydrogen demand, with South Korea and Japan tailing closely. The study forecasts the energy consumption for solar hydrogen production in G20 countries to oscillate between 3.02 and 2.89 million GWh in 2022, while production costs are anticipated to range from $8.47/kg to $10.01/kg. In an assertive scenario, the paper illuminates a pathway towards achieving a significant CO 2 reduction, unmasking environmental savings of up to a staggering 48%, equivalent to 1.5 million mtCO 2 , by 2050. [Display omitted] • Hydrogen demand of G20 countries is analyzed using GIS and techno-economic models. • The projected adoption rates of hydrogen vary among the G20 countries. • Solar energy is crucial in determining each region's annual energy demand. • China, US, and India have the highest solar potential throughout the year. • The environmental analysis shows 850–1.5 million mtCO2 total emissions by 2050. [ABSTRACT FROM AUTHOR]

Hydrogen is considered a truly clean energy source with great potential for replacing fossil fuels. However, the special physical and chemical properties of this source make large-scale, safe, and efficient storage challenging, thus limiting its widespread use. Consequently, an underground hydrogen storage system inspired by underground methane storage and CO 2 geological sequestration has been proposed, and it is increasingly becoming a focus of research. Depleted oil reservoirs are ideal sites for such systems. Nevertheless, research on these types of underground hydrogen storage systems is limited to a few feasibility assessments, and the hydrogen seepage laws in reservoirs with residual oil are not well understood. In this paper, a study was conducted involving mathematical modeling and numerical simulation of underground hydrogen storage, which was converted from the SSZ low-permeability depleted oil reservoir in Bohaiwan Basin, eastern China, to reveal the seepage patterns between hydrogen and complicated in situ fluids (oil, gas, and water). First, a comprehensive analysis was conducted using numerous rock samples and experimental data to identify the composition, genesis, and distribution patterns of the sandstone reservoir, detailing its internal pore structure and fluid distribution postdepletion characteristics. Then, the hydrogen seepage properties in the presence of oil films in the three main throat types of low-permeability sandstone were analyzed, and corresponding mathematical models of the different throats were established. Finally, a numerical simulation of underground hydrogen storage was conducted to assess the impacts of various parameters, such as injection speed, reservoir heterogeneity, and residual oil saturation, on hydrogen seepage. The planar and vertical diffusion patterns of hydrogen were clarified, and the key factors affecting the efficiency of underground hydrogen storage were analyzed, offering suggestions for the establishment of stable and efficient underground hydrogen storage systems. • Selection and description of typical low-permeability reservoirs for UHS. • Mathematical model establishment for hydrogen percolation in porous rock. • Numerical simulation of the storage process of hydrogen. • Percolation laws of hydrogen in rock porous. [ABSTRACT FROM AUTHOR]

The identification of the technical cooperation mode in the field of hydrogen energy is of great importance in guiding technological innovation. Based on the social network analysis (SNA) and spatial network method, this paper constructs the technical cooperation graph of China's industry-university-research (IUR) tripartites in the field of hydrogen technology. Based on the performed graphs, it shows the game and evolution of hydrogen technology innovation in three stages, respectively 2000–2010, 2011–2015 and 2016–2019. Meanwhile, this paper calculates the changes of network indicators and found that: (1) the network density showed a downward trend, from the initial 0.062 to 0.003. (2) The degree centrality of the network decreased from 14.7% to 5.7%. (3) The average path length and clustering coefficient indicate that the internal connections within the network were relatively close from 2000 to 2010, and had small-world characteristics. From 2016 to 2019, although the clustering coefficient increased, the average path length also increased significantly, indicating that the internal connections of the network did not become closer. From the network characteristics, the collaborative innovation network of China's hydrogen energy industry continues to expand in scale and scope, and the cooperation relationship is stable. However, it shows the characteristics of low network density and loose cooperation relationship, gradually developing into a scale-free network. Developed provinces and cities in North and East China occupy core positions in the industry-university-research network, while other regions are gradually expanding their cooperation efficiency; however, the overall cooperation frequency is relatively low in Northeast China, and most provinces and cities in South and Northwest China are in edge positions with poor collaboration capabilities. • Network analysis sheds light on China's hydrogen energy tech cooperation via patent. • Collaborative innovation in hydrogen technology evolves through three stages. • Tight internal connections with small-world properties seen in network (2000–2010). • Network's internal connections didn't become closer (2016–2019). • Network transforms from a stable and expanding structure into a scale-free network. [ABSTRACT FROM AUTHOR]

The production of energy, food, water, and other utensils by fossil fuels generates pollution that causes constant climate change. To minimize and avoid this phenomenon, opting for less polluting energy production sources is increasingly necessary. Green hydrogen (H 2), a renewable and clean fuel, is analyzed in bibliometric terms in the present work, emphasizing photosynthetic H 2. The data were obtained through the journal database list in Web of Science, in which a total of 1507 was published between January 2010 to September 2022, dealing with the production of photosynthetic green hydrogen. The country with the most significant publication is China, with respectively 24.50% of the publications, and the Chinese Academy of Sciences has 60 co-authored papers, the largest in co-authorship—most papers published in the international journal of hydrogen energy, with 19.49% of the publications. The raw materials identified as emerging are cyanobacteria and microalgae, Rhodobacter capsulatus , synechocystis sp pcc6803 and Chlamydomonas reinhardtii pointed out as the microalgae of most significant interest. However, it is necessary to improve them, given the decrease in inactivity provided by the Calvin-Benson cycle. Life cycle assessment studies are needed, as well as H 2 storage. There is a need to reduce the levelized cost of H 2 production, which is around 9.65–25.22 USD/gallon. Studies also point to using cyanobacteria and microalgae to produce other biofuels (bioethanol biodiesel) and materials (supercapacitors, batteries, and polymers). [Display omitted] • Evaluation of the photosynthetic production of green hydrogen. • Analysis of 1507 papers from the Web of Science with CiteSpace, Vosviwer and Exell. • Advanced bibliometric analysis of future trends in the production of green hydrogen. • Using photosynthetic methods to produce biofuels. • Polymer production uses carbon dioxide and green hydrogen. [ABSTRACT FROM AUTHOR]

In this paper, the numerical calculation model of salt cavern hydrogen storage was established based on the proposed salt cavern hydrogen storage in a bedded salt mine in Jiangsu Province of China. The effects of the minimum internal pressure, maximum internal pressure, average internal pressure and injection-production rate on the stability and tightness of the storage were explored respectively. The results revealed that: (1) The volume shrinkage rate and the plastic zone distribution of the surrounding rock decreased with the increase of the minimum internal pressure, and increased with the decrease of the maximum internal pressure. (2) When the depth of salt cavern is around 1700 m , its long-term stability cannot meet the requirements according to the traditional standard of 0.3–0.8 times of the vertical stress at the cavern roof. It is therefore suggested that the minimum internal pressure of the storage should be increased to 0.4 times of the vertical stress at the cavern roof. (3) The tightness evaluation indexes, including leak range, pore pressure distribution of hydrogen, and cumulative leakage of hydrogen in surrounding rock, all increased with the increase of average pressure and amplitude of internal pressure. (4) Under the same average internal pressure and injection-production frequency, the greater the injection-production rate (the amplitude of internal pressure), the smaller the cumulative leakage rate is. Therefore, increasing the injection-production rate is beneficial to the storability of the hydrogen storage. • Different internal pressures are set to study the stability and tightness of the salt cavern for hydrogen storage. • Raising the minimum internal pressure can enhance the stability of the salt cavern. • The amplitude of internal pressure is the key factor affecting the tightness of the salt cavern. • The selection of internal pressure for hydrogen storage should take into account the effects of multiple factors. [ABSTRACT FROM AUTHOR]

The ongoing transition from fossil fuel-based electricity generation toward green energy relying on the intermittent renewable energy sources indispensably requires development of novel energy conversion and storage methods. Depending on a particular location and local resources, pumped storage, lithium- or sodium-ion batteries, compressed air energy storage, as well as the so called power-to-gas (P2G) technologies may be applied. Taking into account the abundant solar energy resources available in the northwestern China, such as Ningxia hui autonomous region, and local water resources coming from the Yellow River, a power-to-hydrogen (P2H2) distributed energy conversion system is proposed in this paper, which is based on a high-efficiency reversible Solid Oxide Cell (rSOC). The conducted studies comprise tests with simulated current based on the actual photovoltaic power station data, and with usage of the as-obtained Yellow River water for the electrolysis mode without any pretreatment. It is documented that the reversible operation is beneficial, and the tested cell can operate for a prolonged time. Of importance, Na, Ca, Mg, and Si elements remain in an evaporator, and do not contaminate the cell, while higher than the initial boron concentration can be found in the condensed exhaust gases. The respective operational parameters of the system correspond to an electrolysis current density loading up 433.3 mA cm−2 for 4 h, as well as fuel cell operation mode with a current density of 8.3 mA cm−2 for 12 h. It is found that the average voltage losses in the electrolysis cell and fuel cell mode are 0.27 %/cycle and 0.886 %/cycle, respectively, indicating that the lifetime of the cells can be more than 800 h. The reported studies demonstrate validity of applying rSOC-based P2H2 system, especially if abundant photovoltaic power and water resources are available. [Display omitted] • The Yellow River water was utilized by rSOC for the first time. • The designed test current was modeled with local photovoltaics. • The P2H2 nearby consumption system can reversibly operate for over 800 h. • The degradation rates in SOFC mode are lower than those in SOEC mode. • The Yellow River water has no significant effect on the degradation rate. [ABSTRACT FROM AUTHOR]

The use of hydrogen fuel cell vehicles is an important way to achieve carbon emission reduction in China's commercial vehicle field. The development of the hydrogen automobile industry needs policy guidance. To determine the characteristics and effects of China's hydrogen automobile industrial policy, this paper first uses a text mining method to analyze policy characteristics from three aspects: potency rank, policy subject and policy objectives. Then, from the perspective of policy tools, a policy quantitative system and standards are constructed to quantify the policy. Then, the sales data of hydrogen fuel cell vehicles from August 2018 to December 2022 were collected to empirically analyze the effect of the policy. The results showed that policy comprehensiveness significantly promoted the use of hydrogen fuel cell vehicles, but the effects of the different policy tools differed. Finally, some policy suggestions are proposed for the development of the hydrogen automobile industry. • China's hydrogen vehicle industry policy focuses on technology upgrading and application demonstration. • The use of hydrogen fuel cell vehicles is the most concerned industrial chain link in the policy. • Policy comprehensiveness has a significant positive effect on the promotion of hydrogen fuel cell vehicles in China. • Different policy tools play different roles, with supply-based policy tools and demand-based playing a more prominent role. [ABSTRACT FROM AUTHOR]

Studies on the iodine-sulfur (IS) thermochemical cycle for hydrogen production has been carried out since about 2005 by the Institute of Nuclear and New Energy Technology, Tsinghua University, China. The HI decomposition occupies the important position of hydrogen generation in the IS cycle. In this paper, the HI-100 test apparatus with a H 2 production rate of 100 L/h was constructed and the HI decomposition was tested. First, the process and components for HI decomposition were designed. Then, the key components, including the feed tank, evaporator, gas heater, adiabatic reactor, condenser, and gas-liquid separator were made of industrial materials. After building this apparatus, the sealing test, heating water test, and HI decomposition have been conducted. The stable hydrogen production operation of more than 100 L/h had been achieved for 5 h, the maximum hydrogen production reached approximately 130 L/h, and the hydroiodic acid decomposition rate maintained about 22 %. The test results provide the design and experimental guidance for further amplification of HI decomposition for hydrogen production by the IS cycle. • The HI-100 test apparatus with the H 2 production rate of 100 NL/h was constructed. • An HI decomposition test for iodine-sulfur hydrogen production cycle was carried out. • The stable hydrogen production operation of above 100 L/h was achieved for 5 h. • The maximum hydrogen production rate reached about 130 L/h in HI-100 apparatus. • The hydroiodic acid decomposition rate maintained about 22 %. [ABSTRACT FROM AUTHOR]

Regional integrated energy systems (RIES) can economically and efficiently use regional renewable energy resources, of which energy storage is an important means to solve the uncertainty of renewable energy output, but traditional electrochemical energy storage is only single electrical energy storage, and the energy efficiency level is low. Hydrogen energy storage has the advantages of large energy storage capacity, long storage time, clean and pollution-free, and can realize the synergistic and efficient utilization of electricity and thermal power. Based on this, this paper proposes a synergistic planning method for an integrated energy system with hydrogen storage taking into account the coupled use of electric-thermal energy, which effectively reduces the system carbon emission and improves the comprehensive energy efficiency level. Firstly, this paper constructs an electric-thermal coupling model of the hydrogen energy storage unit and proposes an optimization strategy for the integrated energy system containing hydrogen storage taking into account the utilization of electricity and thermal power. Secondly, a planning optimization model with the lowest economy and carbon emission and the highest comprehensive energy efficiency was constructed. Third, the CSPO-GE optimization algorithm is proposed for solving the problem, which significantly improves the solution efficiency. Finally, a planning optimization simulation of RIES for a residential community W in northern China verifies the effectiveness of the model and method proposed in this paper. The comparative analysis of the three schemes shows that compared with the integrated energy system with conventional electrochemical energy storage and heat storage tank as the main form of energy storage and the integrated energy system with only hydrogen storage, the integrated energy system with hydrogen storage and heat storage tank can reduce carbon emissions by 43.8% and 7.61%, respectively, and improve the integrated energy efficiency level by 337.14% and 14.44%. • An electrothermal coupled production strategy based on dynamic equilibrium feedback regulation is proposed. • A hydrogen-containing RIES planning and optimization model considering economy-environment-efficiency is constructed. • A multi-objective chaotic particle swarm algorithm (CPSO-GE) based on greedy and elite retention strategies is proposed • The impact of cost variation of hydrogen storage devices on the economics of integrated energy systems is considered. [ABSTRACT FROM AUTHOR]

Hydrogen is not only an important energy carrier needed to achieve the global goal of carbon neutrality, but also an important way of international energy trade in the future. This research analyzes the advantages and challenges of China's participation in international hydrogen trade in detail, proposes the possible routes of China's international hydrogen trade, and proposes specific measures to enhance China's participation in international hydrogen trade. This paper proposes that China should take green hydrogen as its development direction, and guide the development of China's hydrogen trade with the principle of blue green cooperation and gray hydrogen withdrawal. In the future, China's hydrogen trade forms will be diversified, and the types of trade will cover the entire hydrogen energy industry chain. Therefore, China should accelerate the overall deployment of hydrogen trade and the construction of hydrogen trade infrastructure, and build a more sophisticated hydrogen economy. [Display omitted] • The advantages of China's international hydrogen trade are analyzed. • Discussed China's possible international hydrogen trade routes in the future. • The obstacles affecting China's hydrogen competitiveness are analyzed. • Put forward suggestions to promote China's international hydrogen trade. [ABSTRACT FROM AUTHOR]

The efficient utilization of industrial by-products, such as synthetic ammonia exhaust tail gas and coke oven gas, has been neglected in China for a long time. Thus, the development of novel high-efficiency industrial by-product utilization methods is of great importance. A multistage multicycle cascade refrigeration system utilized for hydrogen liquefaction with LNG production is constructed in this paper. The industrial by-products after purification directly enter into cryogenic separation liquefaction system. Liquid hydrogen and LNG are produced after pre-cooling, separation and liquefaction respectively. Process configuration, thermodynamic analysis, optimization model with GA is conducted. The specific power consumption of the multistage multicycle cascade system is within 14.0–17.4 kWh/kmol (feed gas). The proposed process can be used in the efficient utilization of industrial by-products with high exergy efficiency (33.6%∼41.45%) and great economic benefits. • A cryogenic separation and simultaneous extraction system for liquid hydrogen and LNG is proposed. • A multistage multicycle cascade refrigeration system is constructed. • Key variables in the process are optimized to reduce the power consumption of the process. • MMcascade system has lower power consumption in the cases of high hydrogen content in feed gas. [ABSTRACT FROM AUTHOR]

With rapid industrialization, rising fossil fuel consumption, and environmental concerns, developing clean and green energy is an inescapable option. Hydrogen has emerged as a significant potential energy carrier and a viable future replacement fuel for fossil fuels due to its renewable and pollution-free properties. Previous review papers have significantly contributed to the body of literature on the various technologies for producing hydrogen by revealing key insights into their working principles and conditions, as well as the economic and environmental aspects. In addition, they also highlighted the potential pathways to enable the application of these technologies in the context of carbon neutrality. However, these studies have not broken down the evolutionary patterns and developmental progress of either fossil fuel-based or renewable energy-based technologies used to produce hydrogen. In addition, the currently available literature does not contain the most recent research that focuses on the evolution and life cycle of each technology category from a chronological point of view. The key drivers, countries/regions, and their contributions to the field's development have received little attention. As a result, it is critical to monitor technological advances in hydrogen energy production and investigate the key enablers of these advancements. Against this backdrop, the current study employs patent analysis tools to achieve four primary goals: (1) to track the development trends in the field of hydrogen production from 2000 to 2019; (2) to identify and compare the recent development trends in the last five years according to the feedstock, i.e., fossil fuel, water, and biomass-based technologies; (3) to predict the technology life cycle of the two main groups of hydrogen production technologies (fossil and renewable); (4) to identify and compare the key drivers of hydrogen production technologies from a statistical standpoint. The findings of the study may aid in identifying technical prospects in the field of fossil and renewable-based hydrogen production, and decision-makers may use them as a reference in developing a strategic plan for future technological growth. • Patent review on hydrogen production technologies from 2000 to 2019. • Japan, US, China are the leading countries in the field. • Recent developments are focused on renewable energy-based technologies especially water. • Technology maturity rate of renewable-based technologies is about 57%. • R&D expenditure strongly promotes hydrogen production innovations. [ABSTRACT FROM AUTHOR]

The cross-regional renewable hydrogen supply is significant for China to resolve the uneven distribution of renewable energy and decarbonize the transportation sector. Yet the economic comparison of various hydrogen supply routes remains obscure. This paper conducts a techno-economic analysis on six hydrogen supply routes for hydrogen refueling stations, including gas-hydrogen tube-trailer, gas-hydrogen pipeline, liquid-hydrogen truck, natural gas pipeline, MeOH truck, and NH 3 truck. Furthermore, the impacts of three critical factors are examined, including electrolyzer selection, transportation distance, and electricity price. The results indicate that, with a transport distance of 2000 km, the natural gas pipeline route offers the lowest cost, while the gas-hydrogen tube-trailer route is not economically feasible. The gas-hydrogen pipeline route shows outstanding cost competitiveness between 200 and 2000 km, while it is greatly influenced by the utilization rate. The liquid-hydrogen truck route demonstrates great potential with the electricity price decreasing. This study may provide guidance for the development of the cross-regional renewable hydrogen supply for hydrogen refueling stations in China. • The techno-economics of six renewable hydrogen supply routes for hydrogen refueling stations are studied in China's context. • The cost impacts of electrolyzer selection, transportation distance, and electricity price are explored. • Natural gas pipeline H 2 blending route offers the lowest cost at 2000 km distance. • Gas-hydrogen pipeline route's cost is strongly influenced by its utilization rate. • Liquid-hydrogen truck route has the best economics when the electricity price is below 0.1 CNY/kWh. [ABSTRACT FROM AUTHOR]

Environmentally friendly and pollution-free hydrogen cell, battery and supercapacitor hybrid power system has taken the attention of scientists in recent years. Several notable advancements in energy storage mechanisms with hybrid power systems have been made during the last decade, influencing innovation, research, and the possible direction for improving energy storage technologies. This paper represents a quantitative analysis of all knowledge carriers with mathematical and statistical methods of hydrogen energy storage to establish a hybrid power system. For selecting the top cited papers in this topic, related articles on energy storage mechanisms for hybrid power systems were searched in the Scopus database under specified predetermined parameters. The selection technique of the most cited paper was based on filtered keywords in the hybrid hydrogen energy storage-based hybrid power system and related research during 2008–2021. About 48% of all articles have been published between 2016 and 2019; 21% will have originated from China; and 29% of the papers have used batteries as a form of energy storage in the application of electric vehicles. Most of the articles contain experimental work (25.11%) followed by simulation analysis (25%) and systematic and nonsystematic review (18.75%). Related publications with the most citations were published in 35 different impactful journals from different publishers and nations. This research found that integrating hydrogen energy storage with battery and supercapacitor to establish a hybrid power system has provided valuable insights into the field's progress and development. Moreover, it is a thriving and expanding subject of study. Bibliometric analysis was used to identify the most significant research publications on the subject of hybrid energy storage, mapping the multidisciplinary character, illustrating nature and trends, and outlining areas for further research. The process of collecting, selecting, and analyzing the most cited articles is expected to contribute to a methodical foundation for future developments of hydrogen energy storage systems and provide viable research paths toward attaining a hybrid power system. • Hydrogen-battery-supercapacitor hybrid power system made notable advancements. • A statistical analysis of hydrogen storage integrated hybrid system is demonstrated. • Top cited papers were searched in Scopus database under predetermined parameters. • Challenges and recommendations are highlighted for future energy applications. • Bibliometric analysis was used to identify potentials for future research directions. [ABSTRACT FROM AUTHOR]

Using skid-mounted natural gas to hydrogen generator in hydrogen refueling station can significantly reduce the cost of hydrogen. In 2021, China successfully built the first 250 Nm3/h on-site skid-mounted natural gas to hydrogen generator, which was successfully debug-ed in Foshan, providing hydrogen products with purity ≥99.999% for FCVs. This paper summarized the technological process and development, analyzed the risk and the safety design of skid-mounted natural gas to hydrogen generator. Several key factors affecting compactness are analyzed, including process and technical route, reforming reformer and catalyst, heat exchange network, heat exchanger and steam generation system, PSA unit and overall integrated design, etc. In addition, innovative strategies to optimize the compactness of the device are given from the aspects of process flow, reforming reformer and steam generation system.The suggestions are put forward for the development and application of on-site skid-mounted natural gas to hydrogen generator. • The first 250 Nm3/h on-site skid-mounted natural gas to hydrogen generator in China. • The technological process and development of skid-mounted natural gas to hydrogen generator. • The risk analysis and safety design of skid-mounted natural gas to hydrogen generator. • Several key influencing factors and strategies to optimize the compactness. • Cost estimation and competitiveness of skid-mounted natural gas to hydrogen generator. [ABSTRACT FROM AUTHOR]

To satisfy the growing refueling demand of hydrogen fuel cell vehicles (HFCVs) with carbon-free hydrogen supply, this paper proposes an integrated planning method of green hydrogen supply chain. First, the k-shorted path method is introduced to analyze HFCV refueling load considering vehicle travel habits and routing diversity. Second, based on it, a two-stage integrated planning model is established to minimize the total investment and operation cost. The construction of hydrogen refueling stations, electrolysis-based hydrogen generation stations and hydrogen pipelines are coordinated with their operating constraints, constituting the green hydrogen supply chain, in which hydrogen storage is also an important part for consideration to address variable renewable power. Then, the proposed model is reformulated as a mixed integer linear programing (MILP) problem solved efficiently. Finally, the case studies are carried out on an urban area in Xi'an China to verify the validity and correctness of the proposed method. The results show that the integrated planning can realize synergy benefits. The influence of electricity prices and k values is also discussed. • Develop two-stage integrated planning method of the green hydrogen supply chain for HFCVs in urban areas. • Employ K-shortest path method to simulate hydrogen fuel cell vehicle (HFCV) refueling loads on a specified road network. • Co-optimize placement of Hydrogen Refueling Stations (HRSs), Hydrogen Generation Stations (HGSs) and hydrogen pipelines. • Use Piecewise linearization solution method for non-convex model. • Conduct Case Study of Pipeline topology and HRS deployment based on real urban transportation network. [ABSTRACT FROM AUTHOR]

Wind power hydrogen production is the direct conversion of electricity generated by wind power into hydrogen through water electrolysis hydrogen production equipment, which produces hydrogen for convenient long-term storage through water electrolysis. With the development of offshore wind power from offshore projects, construction costs continue to rise. Turning power transmission into hydrogen transmission will help reduce the cost of offshore wind power construction. This paper analyses the methods of producing hydrogen from offshore wind power, including alkaline water electrolysis, proton exchange membrane electrolysis of water, and solid oxide electrolysis of water. In addition, this paper outlines economic and cost analyses of hydrogen production from offshore wind power. In the future, with the development and advancement of water electrolysis hydrogen production technology, hydrogen production from offshore wind power could be more economical and practical. • Different ways of producing hydrogen via water splitting from offshore wind power. • Economic analyses of offshore wind power hydrogen production. • Future directions for economical and practical hydrogen production from offshore wind power. [ABSTRACT FROM AUTHOR]

Hydrogen fuel cell vehicle (HFCV) as an emerging industry with great potential have received great attention in the Yangtze River Delta, China. Under government's promotion of hydrogen energy, whether HFCV can be accepted by consumers is an important topic for future policymaking. Therefore, this study takes consumers' willingness to consume HFCV as the dependent variable and collects questionnaires from 21 cities in the Yangtze River Delta from 2020 to 2021. Based on Ordinary Least Squares (OLS) and Logit Regression, the evaluation was conducted from four perspectives: personal and family situation, environmental awareness, energy attitude and local product confidence. The results show that gender, age and income differences are not necessarily determinants of HFCV purchase, but educational level is a significant factor. Consistent with social-psychological studies, personal awareness of environmental protection and energy attitudes are the key factors that are significant affect HFCV purchase. Lastly, it is found that in the Yangtze River Delta, consumers' confidence in Chinese local hydrogen products is also a significant factor. This paper confirms that HFCV consumers have commonalities with other new energy consumers. However, due to the expectation of greater local production and development, enhancing the social recognition and confidence of local hydrogen technology may be one of the promotion approaches neglected. • Consumer Acceptance for Hydrogen fuel cell vehicle (HFCV) in China is explored. • 600 questionnaires were collected from 21 cities in the Yangtze River Delta. • Psychological constructs such as environmental awareness and energy attitudes are still validated in HFCV consumption. • Improving social confidence in local HFCV technology is an important promotion orientation for China. [ABSTRACT FROM AUTHOR]

China's carbon peaking and carbon neutrality goals present a significant challenge for coal chemical technology, which is critical to securing the energy structure. Combining coal chemical industry technology with new energy is an effective approach to transform the development of the coal chemical industry. This paper proposes and studies a novel coal-to-methanol (CTM) technology of gasification integrated solid oxide electrolysis cell (SOEC). SOEC electrolytic hydrogen production technology is an advanced electrolytic water technology with the advantages of large scale and high efficiency, which is very suitable to be combined with industrial technology and can solve the painful problem of H 2 deficiency in the conventional coal to methanol process. In this study, from mechanistic analysis and model simulations, it is observed that by increasing the SOEC capacity, the novel CTM system can create more methanol at the same coal consumption and simultaneously reduce CO 2 emissions. The novel CTM system can produce up to 2.2 times more methanol and reduce CO 2 emissions by 94% by replacing the water-gas-shift (WGS) process with the SOEC unit. The novel CTM increases energy consumption. In addition, the novel CTM technology will effectively improve the economics of coal to methanol, taking into account the carbon tax. At the methanol price of 2900 RMB/t and SOEC capacity of 250 MW, the economic benefits of novel CTM were 2.1 times greater than CTM technology. • Propose a novel coal-to-methanol technology of gasification integrated electrolysis. • The novel coal-to-methanol technology can produce more methanol and reduce CO 2 emissions. • The novel technology can offer better economics when methanol price is higher than 2900 RMB/t. [ABSTRACT FROM AUTHOR]

The leakage and dispersion of hydrogen gas in a mobile hydrogen refueling station is being numerically investigated in this paper. The investigated geometry is derived from the mobile hydrogen refueling station in China. The numerical models are verified by experimental data. The hydrogen gas leaks from the hydrogen buffer tank in the form of momentum-dominated jet. The combustible danger region, the hydrogen concentration distribution, and the volume of hydrogen gas cloud are investigated. The effects of leakage positions and leakage flow rates on the characteristics and evolution of hydrogen diffusion in the mobile hydrogen refueling station and the open space are analyzed. The results show that the hydrogen concentration in the 3-way corner of the ceiling opposite the leakage orifice first reaches 0.4% and 4%. When the leakage orifice faces the sidewall of the truck container, the liquid hydrogen storage is completely surrounded by hydrogen gas clouds in the flammability limit. The maximum diffusion height of hydrogen at the lower flammable limit increased as the leakage flow rate increased, and the volume of hydrogen in the flammability limit increased virtually exponentially in the open space. The research findings provide a significant reference for potential explosion and risk assessment studies of mobile hydrogen refueling station. • Hydrogen diffusion in a mobile hydrogen refueling station (MHRS) was studied. • The air wind promoted multiple hydrogen clouds to form a single hydrogen cloud. • The high-speed hydrogen gas jet hit the wall showed the wall-diffusion effect. • The H 2 volume in the MHRS was the minimum when vertical downward leakage position. • The H 2 volume in the open space increased almost exponentially with the leakage rate. [ABSTRACT FROM AUTHOR]

It is proposed to develop a novel thermochemical cycle using nuclear energy to decompose H 2 S and CO 2 , thus producing H 2 and CO from acidic gas in petrochemical or coal chemical industries, reducing CO 2 emissions and promoting sustainable energy development. The upper limits and significant energy-consuming steps were determined based on two chemical routes of the thermochemical cycle systems 1 and 2. When the enthalpy of the H 2 S oxidation reaction served as part of the circulating energy input, the values for system 1 and system 2 were 38.7% and 34.3%, respectively. However, if only external energy is considered to satisfy the heat and work required to run the reaction and pump, the thermal efficiency rises to 58.4% and 61.2%, respectively. The life cycle assessment (LCA) was used to investigate the environmental effect of the hydrogen generation process base on the upper thermal efficiency in this study, and the results of the LCA are stated in terms of global warming potential (GWP) and acidification potential (AP). The GWP of systems 1 and 2 was calculated as 2.59 kg CO 2 -eq/kg H 2 , 2.54 kg CO 2 -eq/kg H 2 , The AP of systems 1 and 2 was calculated as 7.48 g SO 2 -eq/kg H 2 and 9.08 g SO 2 -eq/kg H 2 , respectively. This paper assesses the environmental effect of two different hydrogen systems used in manufacturing various subsystems in GWP and AP, and compares them to the life cycle of other hydrogen production pathways. • A novel thermochemical cycle using nuclear energy to split H 2 S-CO 2 is proposed. • Energy-consuming steps and the upper thermal efficiency were determined. • The upper thermal efficiency has been developed to assess environmental impacts. • The LCA integrated China's HTR-PM with the innovative H 2 S-CO 2 process. • GWP and AP in the H 2 S-CO 2 system are compared to other hydrogen methods. [ABSTRACT FROM AUTHOR]

The popularity of hydrogen refueling stations in China is hindered by unreasonable site selection and high initial costs. Built gas stations with large consumer groups and reasonable locations can be expanded into oil-hydrogen combined stations. which can effectively reduce construction costs and approval complexity, improve hydrogenation infrastructure and reduce hydrogenation costs. Taking Chinese social-economic environment into consideration, this paper created an optimal site selection decision framework for oil-hydrogen combined stations to achieve the goal of reducing construction costs, transportation costs and carbon emissions in the whole process. A two-stage criteria system including veto criteria system and evaluation criteria system was established, and fuzzy analytic hierarchy process (AHP) method and TOmada De decis ão Interativa Multicritério (TODIM) method were utilized to determine the criteria weight and obtain the ranking of alternatives respectively. Finally, a case study was conducted and the most suitable gas station site for the construction of oil-hydrogen combined station was determined. Moreover, the economics of the several hydrogen sources were discussed from the perspective of best site selected, it is concluded that hydrogen from natural gas or coal is still the best hydrogen source for oil-hydrogen combined stations. • A comprehensive site selection criteria system including veto indicators and evaluation criteria was established. • A fuzzy AHP-TODIM-based decision-making framework for site selection for oil-hydrogen combined stations is established. • The economics and carbon emission levels of different hydrogen sources chosen by oil-hydrogen combined station are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The all-China-made proton exchange membrane fuel cell units were created and one fuel cell stack was assembled, with all domestic material such like Chinese proton exchange membrane, Chinese catalyst, Chinese carbon paper and Chinese graphite plate, on the basis of heat shaping CCM technology and modularized fuel cell stack assembly technology. The fuel cell unit was tested and optimized. The electricity generating test and other related experiments were conducted. It’s showed that the fuel cell unit’s performance was stable and its power density could reach 550 mW/cm2; the fuel cell stack’s operating power had reached 200 mW/cm2 with voltage uniformly distributed. The stack was stable and showed no obvious decrease in performance after 1800 h continuous operation. Discharged water analysis showed the all-China-made fuel cell stack’s materials had good chemical stability. This new type of fuel cell stack is much cheaper in production cost, compared to the same level import fuel cell stack. [Copyright &y& Elsevier]

Hydrogen-blended electricity-gas integrated energy system (EG-IES) utilizes surplus renewable energy power generation to blends hydrogen into the natural gas pipeline network for achieve efficient and economical large-scale hydrogen consumption and long-distance transportation. While enhancing the coupling between the power grid and gas grid, the scheduling control of such a complex system becomes increasingly important. The paper presents a dynamic model of a hydrogen blended EG-IES with high renewable energy permeability, and a modeling method that considers distribution parameters of the natural gas pipeline is obtained by using the cell segmentation and calculating the blended gas composition in real-time to avoid the assumption of constant composition. After the validation against available operational data, a case study of the certain area of Central China is simulated. The coordinate control law is reasonably designed according to the dynamic characteristics of EG-IES and the objective of realizing the load increase within the hydrogen concentration constraint, and the PID is utilized as the benchmark to compare dynamic performance. The results demonstrate that the coordinated control based on the alternate adjustment control law has no overshoot and shorter adjustment time of p l and ε about 33% and 42% than benchmark on the large delay system. • Establish a dynamic hydrogen blended electricity-gas integrated system model. • Solve the distribution parameter characteristics of the natural gas pipeline network. • Dynamic simulation and verification of a real EG-IES in Central China was carried. • Analysis of the different coordinate control performance during the load up process. [ABSTRACT FROM AUTHOR]

The international hydrogen supply chain has been commercialized and promoted hydrogen trade. With the global energy transition, the two are expected to play a more important role and make hydrogen become a major international energy trade category similar to natural gas and LNG. This paper considers importing two hydrogen sources to Huizhou of China through MCH-TOL hydrogen storage technology from Saudi Arabia, which are produced from Natural gas + CCS and from renewable energy sources. It is estimated that the costs of dehydrogenation and purification after landing are 27.6 CNY/kgH 2 and 32.7 CNY/kgH 2 respectively, which are difficult to be competitive. Therefore, the strategy and goal of cost reduction are proposed. It is expected to control the costs of dehydrogenation and purification to less than 25 CNY/kgH 2 , and explore the feasibility of developing large-scale and economically competitive hydrogen import business in China. • Composition, development status and prospect of international hydrogen supply chain and global hydrogen export. • Select suitable liquid organic hydrogen carrier for hydrogen trans -ocean transportation. • Introduce the hydrogenation and dehydrogenation processes of Methylcyclohexane - Toluene hydrogen storage technology. • Cost estimation and competitiveness analysis of importing hydrogen from Saudi Arabia to Huizhou, Guangdong, China. • Provide strategic suggestions for China to reduce the cost of importing hydrogen from overseas. [ABSTRACT FROM AUTHOR]

Hydrogen and fuel cells are getting increasing attention, and they are more widely used in the transportation sector. Meanwhile, hydrogen fuel cell heavy-duty trucks are also attracting people's attention. In this paper, people's tendency to adopt and the influencing factors of willingness-to-pay for hydrogen fuel cell heavy trucks are studied based on a choice experiment, and customers' willingness to pay is also analyzed. The results show that customers are not very willing to buy hydrogen fuel cell heavy-duty trucks, but the purchase price, fuel cost, environmental awareness, and the number of heavy-duty trucks purchased have a significant impact on the choice of participants. People's willingness to pay is 116,099–131,579 USD, more than 50% higher than diesel heavy trucks, and they are willing to pay no more than 1548 USD a year for maintenance. Based on this, the research will provide references for the formulation of manufacturers' production strategies, government subsidies policies and distributors' marketing plans. • Willingness to pay (WTP) for hydrogen fuel cell heavy trucks in China. • The choice experiment is performed to analyze consumers' buying preferences. • Factors that significantly influenced participants' choices were found. • People's willingness to pay is 116,099–131,579 USD, more than 50% higher than diesel heavy trucks. [ABSTRACT FROM AUTHOR]

This paper studies the economic and financial feasibility analysis of hydrogen energy projects in China to identify appropriate green financing solutions for them. Cost-benefit and sensitivity analysis approaches were carried out for the three hydrogen projects in Guangdong province (two cases) and Jiang Xi province (one case). The hydrogen projects are more sensitive to borrowing interest rates and income tax rates, amongst other financing costs. The main reasons are the capital-intensive nature of green energy projects and the role of tax in the rate of return of green projects in the long term. The optimal weight of bank loans for the studied hydrogen projects in China was calculated at nearly 56%, meaning the weight of green bonds is approximately 44%. In other words, diversifying financing channels instead of just relying on bank loans is recommended to reduce the financing risk and capital cost. As a major policy implication, we recommended various de-risking tools, such as the green credit guarantee corporation, to attract private investments in hydrogen projects. • Green Financing solutions can enhance the feasibility of hydrogen projects. • Hydrogen projects' feasibility is highly sensitive to borrowing interest rates and income tax rates. • We calculated the optimal financing of 3 hydrogen projects in China using bank loans and green bonds. • Diversifying channels of financing instead of just relying on bank loans is recommended. • De-risking tools, such as the green credit guarantee corporation, attract private investments in hydrogen projects. [ABSTRACT FROM AUTHOR]

Tritium self-sustaining operation, which is achieved by a successful closed tritium fuel cycle, is one of the key scientific objectives of China Fusion Engineering Test Reactor (CFETR). The initial tritium start-up inventory and the required TBR are two key parameters which directly affect the possibility of achieving tritium self-sufficiency. In this paper, a new purge gas scheme of He + 0.n% vol. D 2 is proposed for tritium extraction of solid breeder blanket, which can avoid the existence of protium in the mixed gas. In this way, the isotope separation system (ISS) in outer fuel cycle (OFC) can be omitted and a new concept of direct external recycling (DER) has been first put forward for OFC, which aims to skip ISS-O and reduce the processing time of OFC; and the feasibility of DER is preliminarily analyzed from four aspects. On this basis, the influences of DER on both the initial start-up inventory and the required TBR have been preliminarily analyzed for different fueling efficiency and tritium burning fraction (TBF) products, and the calculation results are compared with those corresponding to the same direct internal recycling (DIR) fractions. The results indicate that the application of DER can reduce the demand for both the initial start-up inventory and the required TBR, which can improve the possibility of achieving tritium self-sufficiency appropriately. In particular, the amount of "start-up inventory saved by DER" is still attractive under the condition of high fueling efficiency and TBF, and it is in direct proportion to the fusion power. Both of these make DER technology even more attractive for DEMO reactor and future power plant (FPP). These studies can provide some valuable suggestions for the design and optimization of the tritium fuel cycle system of CFETR and FPP. • A new purge gas scheme of He + 0.n% vol. D 2 is proposed for tritium extraction of solid breeder blanket. • A new concept of direct external recycling (DER) has been first put forward for outer fuel cycle. • The influences of DER on both the initial start-up inventory and the required TBR have been preliminarily analyzed. • The application of DER can improve the possibility of achieving tritium self-sufficiency appropriately. [ABSTRACT FROM AUTHOR]

The pursuing of inter-regional power transmission to address renewable power curtailment in China has resulted in disappointing gains. This paper evaluates the case of local green ammonia production to address this issue. An improved optimization-based simulation model is applied to simulate lifetime green manufacturing, and the impacts of main institutional incentives and oxygen synergy on investment are analysed. Levelized cost of ammonia is estimated at around 820 USD/t, which is about twice the present price. The operating rate, ammonia price, the electrical efficiency of electrolysers and the electricity price are found to be the key factors in green ammonia investment. Carbon pricing and value-added tax exemption exert obvious influences on the energy transition in China. A subsidy of approximately 450 USD/t will be required according to the present price; however, this can be reduced by 100 USD/t through oxygen synergy. Compared to inter-regional power transmission, green ammonia production shows both economic and environmental advantages. Therefore, we propose an appropriate combination of both options to address renewable power curtailment and the integration of oxygen manufacturing into hydrogen production. We consider the findings and policy implications will contribute to addressing renewable power curtailment and boosting the hydrogen economy in China. [Display omitted] • Local green ammonia production to reduce renewable power curtailment is explored. • The impacts of institutional incentives on green ammonia production are evaluated. • A hybrid model is applied to simulate the lifecycle green production. • Green ammonia investment exhibits both economic and environmental advantages. • The integration of oxygen manufacturing into green hydrogen production is proposed. [ABSTRACT FROM AUTHOR]

The demand for H 2 increases rapidly with the gradual recognition of the potential of H 2 as an important secondary energy. At present, coal gasification is the main way to obtain hydrogen on a large scale and at a low cost in China. The underground coal gasification (UCG), as a kind of in-situ utilization technology that can exploit the unreachable deep coal resources, could become an alternative H 2 production pathway. This paper presents comparative study of energy utilization and resource consumption in H 2 production by UCG and typical surface coal gasification (SCG) technology, namely Lurgi fixed bed gasification, with 1.2 billion Nm3/a throughput of H 2 as example, to offer corresponding data support. The efficiency and the amount of resources consumed in constructing and operating each coal-to-hydrogen system under different conditions have been researched from exergetic point of view, which is not reported in existing literatures. In this paper, the exergy efficiency is calculated to be 40.48% and 40.98% for hydrogen production using UCG and SCG. The result indicates the competitiveness of UCG in the field of hydrogen production comparing with widely used coal gasification technology. The resource consumption is measured by cumulative exergy consumption (CExC), which is 8.17E+10 MJ and 6.57E+10 MJ for H 2 production from UCG and SCG. The result shows that although the H 2 production from UCG has higher CExC, it can significantly reduce the resource consumption of equipment comparing with H 2 production from SCG, indicating its advantage in total investment. It is found that the exergy efficiency increases with the rise in H 2 O-to-O 2 and O 2 -to-CO 2 ratio, while the value of CExC decreases with the appreciation of H 2 O-to-O 2 ratio yet increases as the O 2 -to-CO 2 ratio rises. In addition, the sensitivity analysis of production capacity reveals that the exergy efficiency gap and CExC gap between hydrogen production by UCG and SCG diminishes at smaller scale production capacities, showing that UCG is more suitable for small-scale hydrogen production. • A resource consumption comparison of H 2 production from UCG and SCG is conducted. • Exergy is analyzed with 1.2 billion Nm3/a throughput of H 2 as example. • Exergy efficiency of UCG-H 2 reaches 40.48%, comparable to 40.98% for SCG-H 2. • UCG-H 2 significantly reduces CExC of equipment compared to SCG-H 2. • Effects of key operational parameters on system's performances are investigated. [ABSTRACT FROM AUTHOR]

Based on literature research, this comprehensive analysis of 1275 articles published in the past five decades provides quantitative and objective insight into research trends in the hydrogen economy. Scholars and experts agree that by 2030, hydrogen will play a critical role in energy transition by complementing other renewable energy technologies. We applied indicators such as the Field-Weighted Citation Impact index, cited by and usage count (180 days) to evaluate countries, authors, documents, journals and so on. We also used VOS viewer to visualize the evolving trend using keyword analysis and cluster analysis of documents. Results show that the literature on the hydrogen economy has been recently increasing, particularly from 2016 to 2020. Scopus database was employed to acquire the required data for the study. From preliminary analysis, it was established that from 218 journals, 1275 documents related to hydrogen economy had been published so far. The average publication per year since introducing the term "hydrogen economy" is 6.62 and increasing. The average citation per document is 47.21. There have been 3760 authors so far who have been associated with publications related to a hydrogen economy. Of which 139 authors have written 156 documents individually, and 3621 authors have collaborated to publish 1119 documents, thus forming a collaborative index of 3.24. The International Journal of Hydrogen Energy contributes 40% of the overall publications. In terms of countries, China and United States are the leaders, with 126 papers each. Our analysis shows that the study on hydrogen economy mostly deals with multidisciplinary aspects like hydrogen production, storage, transportation, application, and public policy formulation. We adopted the 180 days usage count offered by the Web of Science database to better understand the research hotspot and evolving trends. It helped us view the existing gaps and potential scope of study that future researchers working on the hydrogen economy can explore. Aspects like pipeline transportation, risk assessment studies, blending, public safety and hazard mitigation can play a vital role in the hydrogen economy research in the future. Cooperation between nations and research institutes should be fostered with cross-disciplinary interchange to boost the hydrogen economy's multidisciplinary growth. • Bibliometric analysis reveals International Journal of Hydrogen Energy is the pioneer journal on hydrogen economy. • Network visualisation analyses disclose that there is a high collaboration index (3.24) among authors. • USA and China are the leaders with 10% publication each. • Emphasis is needed on pipeline transportation, risk assessment studies, and hydrogen blending research. • Hydrogen supply chain and hydrogen fuel cell were the prime themes. [ABSTRACT FROM AUTHOR]

Based on literature research, this comprehensive analysis of 1275 articles published in the past five decades provides quantitative and objective insight into research trends in the hydrogen economy. Scholars and experts agree that by 2030, hydrogen will play a critical role in energy transition by complementing other renewable energy technologies. We applied indicators such as the Field-Weighted Citation Impact index, cited by and usage count (180 days) to evaluate countries, authors, documents, journals and so on. We also used VOS viewer to visualize the evolving trend using keyword analysis and cluster analysis of documents. Results show that the literature on the hydrogen economy has been recently increasing, particularly from 2016 to 2020. Scopus database was employed to acquire the required data for the study. From preliminary analysis, it was established that from 218 journals, 1275 documents related to hydrogen economy had been published so far. The average publication per year since introducing the term "hydrogen economy" is 6.62 and increasing. The average citation per document is 47.21. There have been 3760 authors so far who have been associated with publications related to a hydrogen economy. Of which 139 authors have written 156 documents individually, and 3621 authors have collaborated to publish 1119 documents, thus forming a collaborative index of 3.24. The International Journal of Hydrogen Energy contributes 40% of the overall publications. In terms of countries, China and United States are the leaders, with 126 papers each. Our analysis shows that the study on hydrogen economy mostly deals with multidisciplinary aspects like hydrogen production, storage, transportation, application, and public policy formulation. We adopted the 180 days usage count offered by the Web of Science database to better understand the research hotspot and evolving trends. It helped us view the existing gaps and potential scope of study that future researchers working on the hydrogen economy can explore. Aspects like pipeline transportation, risk assessment studies, blending, public safety and hazard mitigation can play a vital role in the hydrogen economy research in the future. Cooperation between nations and research institutes should be fostered with cross-disciplinary interchange to boost the hydrogen economy's multidisciplinary growth. • Bibliometric analysis reveals International Journal of Hydrogen Energy is the pioneer journal on hydrogen economy. • Network visualisation analyses disclose that there is a high collaboration index (3.24) among authors. • USA and China are the leaders with 10% publication each. • Emphasis is needed on pipeline transportation, risk assessment studies, and hydrogen blending research. • Hydrogen supply chain and hydrogen fuel cell were the prime themes. [ABSTRACT FROM AUTHOR]

Hydrogen is a promising sustainable energy carrier for the future due to its high energetic content and no emissions, other than water vapor. However, its full deployment still requires technological advances in the renewable and cost-effective production of hydrogen, cost reduction of fuel cells and especially in the storage of hydrogen in a lightweight, compact and safe manner. One way to achieve this is by using materials in which hydrogen bonds chemically, or by adsorption. Different kinds of Hydrogen Storage Materials have been investigated, such as Metal-Organic Frameworks (MOFs), Simple Hydrides (including Magnesium Hydride, MgH 2), AB 5 Alloys, AB 2 Alloys, Carbon Nanotubes, Graphene, Borohydrides, Alanates and Ammonia Borane. Billions have been invested in Storage Materials research, resulting in tens of thousands of papers. Thus, it is challenging to track how much effort has been devoted to each materials class, by which countries, and how the field has evolved over the years. Quantitative Science and Technology Indicators, produced by applying Bibliometrics and Text Mining to scientific papers, can aid in achieving this task. In this work, we evaluated the evolution and distribution of Hydrogen Storage Materials research using this methodology. Papers in the 2000–2015 period were collected from Web of Science and processed in VantagePoint® bibliometric software. A thesaurus was elaborated relating keywords and short phrases to specific Hydrogen Storage Materials classes. The number of publications in Hydrogen Storage Materials grew markedly from 2003 to 2010, reducing the pace of growth afterwards until a plateau was reached in 2015. The most researched materials were MOFs, Simple Hydrides and Carbon-based materials. There were three typical trends in materials classes: emerging materials, developed after 2003, such as MOFs and Borohydrides; classical materials with continuous growth during the entire period, such as Simple Hydrides; and stagnant or declining materials, such as Carbon Nanotubes and AB 5 Alloys. The main publishing countries were China, countries from the European Union (EU) and the USA, followed by Japan. There is a division between countries with continued growth in recent years, such as China, and those with stagnant production after 2010, such as the EU, the USA and Japan. The results of this work, compared to a previous study in storage materials patenting by our group, and the recent launch of commercial hydrogen cars and trains and stationary hydrogen production and fuel cell solutions, indicates that although the Hydrogen Energy field as a whole is transitioning from lab and prototype stages to commercial deployment, materials-based hydrogen storage still has base technological challenges to be overcome, and therefore still needs more scientific research before large scale commercialization can be realized. The developed thesaurus is made available for refinement and future works. • H 2 storage materials papers grew exponentially between 2000 and 2009, and maxed in 2015. • Most researched classes: MOFs, Simple Hydrides and Carbon-based materials. • US, EU and JP topped in 2009, while CN, KR and AU continued growing. [ABSTRACT FROM AUTHOR]

Green ammonia production as an important application for propelling the upcoming hydrogen economy has not been paid much attention by China, the world's largest ammonia producer. As a result, related studies are limited. This paper explores potential supply chain design and planning strategies of green ammonia production in the next decade of China with a case study in Inner Mongolia. A hybrid optimization-based simulation approach is applied, considering traditional optimization approaches are insufficient to address uncertainties and dynamics in a long-term energy transition. Results show that the production cost of green ammonia will be at least twice that of the current level due to higher costs of hydrogen supply. Production accounts for the largest share of the total expense of green hydrogen (~80 %). The decline of electricity and electrolyser prices are key in driving down the overall costs. In addition, by-product oxygen is also considered in the model to assess its economic benefits. We found that by-product oxygen sales could partly reduce the total expense of green hydrogen (~12 % at a price of USD 85/t), but it also should be noted that the volatile price of oxygen may pose uncertainties and risks to the effectiveness of the offset. Since the case study may represent the favourable conditions in China due to the abundant renewable energy resources and large-scale ammonia industry in this region, we propose to take a moderate step towards green ammonia production, and policies should be focused on reducing the electricity price and capital investments in green hydrogen production. We assume the findings and implications are informative to planning future green ammonia production in China. • The H 2 -based energy transition in China's ammonia industry is explored. • A hybrid approach for green ammonia supply chain design and planning is proposed. • The cost of green ammonia will be at least twice that of the current level. • Electricity price and expenses in electrolysers are key impacts to the total cost. • Storing and selling by-product oxygen can partly reduce the total cost. [ABSTRACT FROM AUTHOR]

This paper discusses the current development strategy, technology and industrialization of China's hydrogen energy industry in the transportation field, summarizes the characteristics and development experience, and makes a comparative study with the situation of some developed countries. The results show that the current development of hydrogen energy has formed a broad consensus in China and is becoming the overall development of China's national level consciousness. However, China's hydrogen energy industry is still facing problems such as high cost of comprehensive utilization, imperfect standards and regulations for hydrogen energy utilization, obvious tendency of industrial blind development and structural overcapacity risk. Therefore, some policy suggestions were proposed for the future development, such as strengthening top-level design, strengthening pilot demonstration, promoting the development of the whole hydrogen industry chain, and reducing the cost of hydrogen and fuel cell vehicles in the field of transportation. [Display omitted] • The development of hydrogen energy industry has become China's national consensus. • China has formed three major industrial clusters of hydrogen and fuel cells. • China's hydrogen industry is facing the risk of overcapacity. • China should strengthen the top-level design of hydrogen development strategy. [ABSTRACT FROM AUTHOR]

The increasingly serious energy crisis and environmental pollution caused by the excessive use of fossil fuels have been prompting China to aggressively seek a clean and self-sufficient energy source in the future. In the past decades, hydrogen has emerged as a promising alternative due to its advantages of cleanliness, abundance, high energy density, and high conversion efficiency. However, several challenges have to be overcome for China's successful transition to hydrogen economy. In this paper, the hydrogen supply chain is firstly described to help the readers to clearly understand the hydrogen economy. Subsequently, the feasibility of hydrogen economy is discussed by reviewing viewpoints from the literature. Finally, the challenges of China's transition to hydrogen economy are detailed summarized and discussed, and the strategies for China to develop hydrogen economy were compared with that of Japan and Australia. • Hydrogen economy is feasible with many challenges. • Hydrogen and electricity should clearly have the same strategic position in China. • Geographic differences in resources and demands should be addressed. • It is necessary to diversify the application of hydrogen. • CCS technology is significance to the medium-term development of China's hydrogen economy. [ABSTRACT FROM AUTHOR]

The hydrogen energy is considered to be main power source of transport sector in the future, and a huge amount of funds have been invested into developing hydrogen fuel cell electric vehicles (FCEVs). Since FCEVs are in initial development stage and there're few FCEVs on the road, before their expansion this paper intends to conduct an economic analysis for FCEVs by using the choice experiment method. In the choice experiment, 1072 participants were required to select among two FCEVs and one conventional fuel vehicle. Logit models were estimated and then the results were used to calculate the willingness to pay for FCEVs. Results showed that purchase price, driving range, refueling time, fuel cost, emissions reduction, refueling accessibility are significant influences, and the marginal values for every 200 km improvement in driving range, 5 min reduction in refueling time, RMB 0.5/kilometer reduction in fuel cost, 20% reduction in emissions, and 20% improvement of refueling accessibility were estimated to be RMB 49,091, 12,727, 3818, 47,818, and 12,909, respectively. A range of FCEV configurations were calculated, and compared to a gasoline-powered counterpart the extra value that customers were likely to pay for a FCEV ranged from RMB 20,810 to 95,310. These results have significant implications for promoting FCEVs and contribute to better sustainability in transport sector. • A choice experiment was used to collect public preference data of FCEVs. • A logit model was then used to estimate WTP for main attributes of FCEVs. • Driving range, emissions reduction, and refueling time largely decides WTP for a FCEV. • The WTP for various FCEV configurations was calculated and compared. [ABSTRACT FROM AUTHOR]

China is increasing its combustion vehicle numbers rapidly along a Western Model, with high emissions, high energy usage and low utilisation. These characteristics cause severe health, energy and congestion problems that could get five times worse over the next 50 years as the Chinese population buys many more western-type vehicles. This paper describes the steps being taken now in China to avoid the blight caused by combustion vehicles in western cities. In particular, the world's largest hydrogen-fuel-cell-battery (HFCB) bus project is now being implemented in Foshan city by a coalition of government and commercial companies. This project takes advantage of the subsidies offered by both central and local administrations, which have proved successful for battery electric vehicles (BEVs) but have not yet been so popular for hydrogen based machines, mainly because hydrogen infrastructure is not yet installed. Other Foshan PEMFC (Polymer Electrolyte Membrane Fuel Cell) hydrogen projects such as UAVs are also described. Since 2008 when the first hydrogen filling station was created at University of Birmingham, to refuel a fleet of 5 HFCB taxis, there has been little progress in the UK because car corporations have not prioritised zero emission vehicles. China has the unique opportunity to leap-frog the Western Model and provides a more democratic solution based on the success of the less polluting electric scooter, where China leads the world by a huge margin. China can do this because it has a strong government, the desire for infrastructure investment, plus rapidly growing vehicle companies in an expanding market. This paper describes the results of experiments on new hydrogen vehicles in Foshan City, including the biggest hydrogen fuel cells bus project in China at the present time. It does not comprehensively cover other Chinese cities and vehicle companies working on hydrogen. [ABSTRACT FROM AUTHOR]

Hydrogen energy is one of the green energy that may be potentially served for humans. However, it has not been widely used, due to the likelihood of lacking in understanding of hydrogen distribution within an enclosure. This kind of issue still remains unclear in reactor building for nuclear power plants, and has drawn many experts' attention, especially on the hydrogen stratification characteristics under different flow regimes, such as different Froude numbers. A large number of experimental and analytical studies have been conducted to figure out the single phase of hydrogen's dispersion mechanism, in order to evaluate the potential hydrogen risk in gradient layer, which may prevent the fluid from mixing evenly, thus increasing the form of combustible gas, with the wide-spread application of storage and transportation of hydrogen. However, in severe accident for nuclear power plants, build-up of hydrogen gradient layer is more complicated, due to the presence of steam. There is little research focusing on the injection and flow behaviors of both hydrogen and steam, which may occur in Loss-of-Coolant-Accidents (LOCAs), and moreover, with the scaling study by Peterson, it can be realized that the mixing process within an enclosure is governed not only by Froude number, but also by Reynolds number. Therefore, in this paper, a semi-empirical model of hydrogen distribution under the presence of steam is proposed in consideration of both the relative effect of momentum and buoyancy, and the effect of viscous force. The prediction results show better agreement with the experimental data obtained from an international benchmark test, THAI-HM2, and tests with high steam content based on a small scale facility and a modelled reactor building of CAP1400 built in China. After these validations, this analytical model is applied to basic conditions with different Re and Fr numbers. It can be discovered that the steam increases the inertness of ambient in the lower region of the modelled reactor building, and with the increase of the injection's steam content, the light gas will be diluted at the bottom, due to both effects of large density and good flowability characteristics of steam, leading to larger concentration and more stratified layer in upper region, corresponding to higher Re numbers. In order to figure out the relation between mass transfer process and complex flow regimes in gradient layer, a useful criterion is proposed, in consideration of the effect of Re , which can successfully identify the variations of flow regimes, corresponding to the build-up of gradient layer. The analytical model from this work can support the development of new CFD codes and help get new understandings of complex thermal-hydraulic phenomena in hydrogen gradient layer within any given enclosure. • Hydrogen stratification is dominated by Re and Fr numbers under presence of steam. • A new hydrogen distribution model is proposed based on dominant factors. • The flowability and large density of steam help dilute the lower region. • A new criterion is built to identify flow regimes in stratified layers. [ABSTRACT FROM AUTHOR]

Studies focused on the behavior of the hydrogen leakage and diffusion are of great importance for facilitating the large scale application of the hydrogen energy. In this paper, the hydrogen leakage and diffusion in six scenarios which including comparison of different leakage position and different wind effect are analyzed numerically. The studied geometry is derived from the hydrogen refueling station in China. Due to the high pressure in hydrogen storage take, the hydrogen leakage is momentum dominated. The hydrogen volume concentration with the variation of the leakage time in different scenarios is plotted. More importantly, profiles of the flammable gas cloud at the end of the leakage are quantitatively studied. Results indicate that a more narrow space between the leakage hole and the obstacle and a smaller contact area with the obstacle make the profile of the flammable gas cloud more irregular and unpredictable. In addition, results highlight the wind effect on the hydrogen leakage and diffusion. Comparing with scenario which the wind direction consistent with the leakage direction, the opposite wind direction may result in a larger profile of the flammable gas cloud. With wind velocity increasing, the profile of the flammable gas cloud is confined in a smaller range. However, the presence of the wind facilitates the form of the recirculation zone near the obstacle. With an increase of the wind velocity, the recirculation zone moves downward along the obstacle. Thus, the hydrogen accumulation is more prominent near the obstacle. • Hydrogen leakage and diffusion in hydrogen fueling station are studied. • Effect of leakage position on hydrogen leakage and diffusion is studied. • Effects of wind velocity and direction on hydrogen leakage and diffusion are studied. • Profiles of the flammable gas cloud are quantitatively analyzed. • Recirculation zone and its variation in different wind velocity are observed. [ABSTRACT FROM AUTHOR]

Proton exchange membrane (PEM) fuel cells produce a large amount of waste heat while generating electricity through electrochemical reactions, making them suitable for driving combined heating and power (CHP) systems. According to the hourly thermal and electric loads in a typical North China household, a 2-kW PEM fuel cell-based micro-CHP system with a lithium-ion battery energy storage system is proposed in this paper. The thermal and economic performances of the micro-CHP system with a lithium-ion battery (CHPWB) and a CHP system without a lithium-ion battery (CHPWOB) are comparatively analyzed by developing a thermal and economic performance analysis model on the MATLAB/Simulink platform. The thermal-load-following strategy is adopted during the design and simulation process. The results indicate that the storage capacity of the lithium-ion battery decreases by 6.6% after one cycle. The lithium-ion battery can be charged by the fuel cell stack during off-peak hours or using commercial electricity, and the charging cycle of the system is one week long. The average total efficiency of the CHPWB system can reach 81.24% with considering the energy loss in each conversion process, which is 11.02% higher than that of the CHPWOB system. The daily hydrogen consumption of the CHPWB system can be reduced by 14.47% compared with the CHPWOB system under the same operating conditions, and the average daily costs can be reduced by 8.4% and 9.5% when the lifespan is 10 and 15 years, respectively. Image 1 • A PEM fuel cell-based CHP system for a typical household in North China is proposed. • A complete model for this system is developed using the MATLAB/Simulink platform. • The thermal and economic performances of the proposed system are comparatively analyzed. • The thermal and economic performances can be improved by 11.02% and 9.5%, respectively. [ABSTRACT FROM AUTHOR]

The number of hydrogen refuelling stations (HRSs) is steadily growing worldwide. In China, the first renewable hydrogen refuelling station has been built in Dalian for nearly 3 years. FLACS software based on computational fluid dynamics approach is used in this paper for simulation and analysis on the leakage and explosion of hydrogen storage system in this renewable hydrogen refuelling station. The effects of wind speed, leakage direction and wind direction on the consequences of the accident are analyzed. The harmful area, lethal area, the farthest harmful distance and the longest lethal distance in explosion accident of different accident scenarios are calculated. Harmful areas after explosion of different equipments in hydrogen storage system are compared. The results show that leakage accident of the 90 MPa hydrogen storage tank cause the greatest harm in hydrogen explosion. The farthest harmful distance caused by explosion is 35.7 m and the farthest lethal distance is 18.8 m in case of the same direction of wind and leakage. Moreover, it is recommended that the hydrogen tube trailer should not be parked in the hydrogen refuelling station when the amount of hydrogen is sufficient. • The effects of wind speed and direction on hydrogen accidents are analyzed. • The farthest harmful distance and lethal distance are calculated. • The lethal area is larger when the wind speed is low. [ABSTRACT FROM AUTHOR]

China is very ambitious for the development of fusion energy system using the fusion reaction of hydrogen isotopes. According to China magnetic confinement fusion development roadmap, the China Fusion Engineering Test Reactor (CFETR) is expected to be constructed in 2020s, which will be the first hydrogen fusion reactor in China. However, China has not yet established the safety regulatory framework for the licensing of a hydrogen fusion reactor such as CFETR, while the existing regulatory framework is based on the fission reactor development and there are huge differences in the safety characteristics between fusion reactor and fission reactor. In this paper, China's nuclear safety regulation system is reviewed and then key issues are raised for adapting the regulatory framework to the hydrogen fusion reactor, considering the fusion safety characteristics as well as lessons learnt from the licensing of ITER in the French regulations. Gaps between China nuclear safety regulations and CFETR safety concerned demands are also identified and discussed. It is suggested that the engineering design of CFETR shall be done together with the development of corresponding safety regulatory framework. • Gaps identified between China nuclear safety regulations and CFETR safety concerned demands. • Key issues raised for the adaption of regulatory framework to hydrogen fusion reactor. • Overview of China's existing nuclear safety regulation system. [ABSTRACT FROM AUTHOR]

As an important part of energy use in the water end-use system, the energy consumption of urban household water use is typical to illustrate the nexus of water and energy. Considering its urban size and population, Tianjin is studied by questionnaires for residential water use and estimated energy intensity. This paper analyzes water-related energy use by studying water end-use data from 504 households and considering family-related impact and technical factors of water appliances. Results show that clothes washing and shower constitute the largest part of water end-use and water-related energy consumption, respectively. Overall simulation assesses the impact of technological improvements, behavioral modification and water-use decrease in household water-related energy use. It indicates that energy saving could reach to 1.69 * 10 10 KWh per year which accounts for 24% of total energy consumption for non-production purposes, which indicate saving water could lead to saving energy. Correlation analysis are used to analyze the relative effects of factors on household water and energy use. The ratio of hand washing and frequency of shower have significant correlation respectively with water end-use and water-related energy consumption, particularly in the parched north. It is suggested to focus on considering the full cost about water resource, strengthening the development of water saving and energy-efficient water appliances, and enhancing the publicity of water saving in the next step. This paper demonstrates the linkage between water and energy in urban water end-use system, thus providing a decision-support tool for water conservation and management. [ABSTRACT FROM AUTHOR]

Of the current new energy vehicles aiming to solve global energy depletion and greenhouse gas emission, the hydrogen fuel cell vehicle is well-reputed for its zero emission, high energy efficiency and recyclable energy resources. Recently, many demonstration projects have been established in China to promote the production and marketing of new energy vehicles, to explore their economical, technical and political feasibility and to detect technological flaws and design deficiency. Thus, the paper tends to explore these demonstration projects of hydrogen fuel cell vehicles and their marketing strategies in China. After analysing the significance, history, and pattern of these demonstration projects, the paper reviews various cases such as Beijing Olympic Games, Shanghai World Expo, Guangzhou Asian Games, Shenzhen Universiade and project Thousand New Energy Vehicles in Ten Cities . Finally, after giving some advice on the infrastructure (refuelling station and delivery truck) and marketing strategies, the paper predicts the market prospects of the hydrogen fuel cell vehicle. The paper, as the first elaboration on the relationship between the demonstration and the marketing of the new energy vehicles, comes to the conclusion that the demonstration of the new energy vehicle is an essential process for its exploration and marketing. [ABSTRACT FROM AUTHOR]

Abstract: The enhancement of sustainability of hydrogen supply chain is of vital importance for the stakeholders/decision-makers to design a sustainable hydrogen supply chain. The objective of this paper is to develop a method for prioritizing the influential factors, identifying the key driving factors that influence the sustainability of hydrogen supply chain and mapping the cause–effect relationships to improve the sustainability of hydrogen supply chain. In this paper, thirty seven criteria in four aspects including economic, technological, environmental and societal aspects are considered for enhancing the sustainability of hydrogen supply chain, and decision making trial and evaluation laboratory has been used to analyze the relationships among these criteria. The status of hydrogen supply chain in China has been studied by the proposed method, and the results are consistent with the actual conditions. It could be concluded that the proposed method is feasible and could be popularized to some other cases. [Copyright &y& Elsevier]

This paper compares the performance of a 2.02 kWp off-grid residential solar photovoltaic (PV) power system using PVSYST simulation software for a household in Kunming, Yunnan province, China. The monthly available solar energy; missing energy; array, final, and reference yields, performance ratio; and array capture and system losses were analyzed for five solar tracking modes: fixed tilted plane, seasonal tilt adjustment, horizontal axis tracking, vertical axis tracking, and dual axis tracking. Although there were some similar aspects across the five systems, minimum available solar energy (2461 kWh/y) and maximum missing energy (134.68 kWh/y) were obtained using the fixed tilted plane system (tilt angle = 25°, azimuth angle = 0°), whereas maximum available solar energy (3081 kWh/y) and minimum missing energy (48.53 kWh/y) in October were obtained using the dual axis tracking system. Average monthly performance ratio was maximal for the fixed tilted plane system (0.689), and minimal for the dual axis tracking system (0.596). [ABSTRACT FROM AUTHOR]