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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]

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]