China, People’s Republic

Type IV hydrogen storage tanks play an important role in hydrogen fuel cell vehicles (HFCVs) due to their superiority of lightweight good corrosion and fatigue resistance. It is planned to be used between -40℃ and 85℃ at which the polymer liner may have a degradation of mechanical properties and buckling collapse. This demand a good performance of liner materials in that temperature range. In this article the temperature effect on mechanical properties of polyamide 6 (PA6) liner material including specimens with weld seam was investigated via the stress-strain curve (S-S curve) macroscopic and microscopic morphology. Considering that the mechanical properties will change after the liner molding process this test takes samples directly from the liner. Results show that the tensile strength and tensile modulus increased by 2.46 times and 10.6 times respectively with the decrease of temperature especially in the range from 50℃ to -90℃. For the elongation at break and work of fracture they do not monotonously increase with the temperature up. Both of them reduce when the temperature rises from 20°C to 50°C especially for the work of fracture decreasing by 63%. The weld seam weakens the mechanical properties and the elongation at break and work of fracture are more obvious which are greater than 40% at each temperature. In addition the SEM images indicate that the morphology of fracture surface at -90°C is different from that at other temperatures which is a sufficient evidence of toughness reducing in low temperature.

The near-wall flame structure and pollutant emissions of the laminar premixed biogashydrogen impinging flame were simulated with a detailed chemical mechanism. The spatial distributions of the temperature critical species and pollutant emissions near the wall of the laminar premixed biogas–hydrogen impinging flame were obtained and investigated quantitatively. The results show that the cold wall can influence the premixed combustion process in the flame front which is close to the wall but does not touch the wall and results in the obviously declined concentrations of OH H and O radicals in the premixed combustion zone. After flame quenching a high CO concentration can be observed near the wall at equivalence ratios (ϕ) of both 0.8 and 1.2. Compared with that at ϕ = 1.0 more unburned fuel is allowed to pass through the quenching zone and generate CO after flame quenching near the wall thanks to the suppressed fuel consumption rate near the wall and the excess fuel in the unburned gases at ϕ = 0.8 and 1.2 respectively. By isolating the formation routes of NO production it is found that the fast-rising trend of NO concentration near the wall in the post flame region at ϕ = 0.8 is attributed to the NO transportation from the NNH route primarily while the prompt NO production accounts for more than 90% of NO generation in the wall vicinity at ϕ = 1.2. It is thus known that thanks to the effectively increased surface-to-volume ratio the premixed combustion process in the downsized chamber will be affected more easily by the amplified cooling effects of the cold wall which will contribute to the declined combustion efficiency increased CO emission and improved prompt NO production.

Fuel cell electric vehicles are generally considered to have broad development prospects due to their high efficiency and zero emissions. The governments of the United States Japan the European Union and China are taking action to promote the development of the industry. In 2020 China launched a fuel cell electric vehicle demonstration project and there will be 30∼50 thousand FCEVs included in this project by the end of 2025. How to standardize the consistency of data and develop a unified and accurate evaluation method is an important topic. The difficulty is how to keep balance among scientificity neutrality and feasibility in the evaluation method. In order to evaluate the performance of vehicles in demonstration operation projects China has issued the "Fuel Cell Electric Vehicle Test Specifications" which is an important guide for the future development of fuel cell electric vehicles in China. This paper compares the test methods for critical parameters in this specifications with those used in the United States and Japan. It explains China’s technical considerations in detail including fuel cell system rated power the volume power density of the fuel cell stack fuel cell system specific power fuel cell system sub-zero cold start and fuel cell electric vehicle range contributed by hydrogen. For the volume power density of the fuel cell stack as an example both the US Department of Energy and Japan’s New Energy and Industrial Technology Development Organization have proposed technical goals. However the lack of specific and detailed test methods has confused the industry. We propose a new test method using bipolar plate measurement based on scientificity feasibility and neutrality This is the first time to define the measuring method of the volume and specific power density of the fuel cell stack. For sub-zero cold start we put forward a feasible scheme for sub-zero cold start at the system level. For range contributed by hydrogen we propose a new test method that can distinguish the contributing of electric and hydrogen energy. Furthermore a hydrogen-to-electric conversion formula is proposed to calculate the equivalent hydrogen consumption which makes it possible to compare the energy consumption between plug-in and non-plug-in vehicles. At the same time this approach is significant in helping fuel cell-related enterprises to understand the formulation of China’s “Fuel Cell Electric Vehicle Test Specifications”. It should also be helpful for guiding product design and predicting fuel cell electric vehicle policy direction in China.

The aeroderivative gas turbine is widely used as it demonstrates many advantages. Adding hydrogen to natural gas fuels can improve the performance of combustion. Following this the effects of hydrogen enrichment on combustion characteristics were analyzed in an aeroderivative gas turbine combustor using CFD simulations. The numerical model was validated with experimental results. The conditions of the constant mass flow rate and the constant energy input were studied. The results indicate that adding hydrogen reduced the fuel residues significantly (fuel mass at the combustion chamber outlet was reduced up to 60.9%). In addition the discharge of C2H2 and other pollutants was reduced. Increasing the volume fraction of hydrogen in the fuel also reduced CO emissions at the constant energy input while increasing CO emissions at the constant fuel mass flow rate. An excess in the volume fraction of added hydrogen changed the combustion mode in the combustion chamber resulting in fuel-rich combustion (at constant mass flow rate) and diffusion combustion (at constant input power). Hydrogen addition increased the pattern factor and NOx emissions at the outlet of the combustion chamber.

Mg-based materials are one of the most promising hydrogen storage candidates due to their high hydrogen storage capacity environmental benignity and high Clarke number characteristics. However the limited thermodynamics and kinetic properties pose major challenges for their engineering applications. Herein we review the recent progress in improving their thermodynamics and kinetics with an emphasis on the models and the influence of various parameters in the calculated models. Subsequently the impact of alloying composite and nano-crystallization on both thermodynamics and dynamics are discussed in detail. In particular the correlation between various modification strategies and the hydrogen capacity dehydrogenation enthalpy and temperature hydriding/dehydriding rates are summarized. In addition the mechanism of hydrogen storage processes of Mg-based materials is discussed from the aspect of classical kinetic theories and microscope hydrogen transferring behavior. This review concludes with an outlook on the remaining challenge issues and prospects.

The hydrogen storage tank is a key parameter of the hydrogen storage system in hydrogen fuel cell vehicles (HFCVs) as its safety determines the commercialization of HFCVs. Compared with other types the type IV hydrogen storage tank which consists of a polymer liner has the advantages of low cost lightweight and low storage energy consumption but meanwhile higher hydrogen permeability. A detailed review of the existing research on hydrogen permeability of the liner material of type IV hydrogen storage tanks can improve the understanding of the hydrogen permeation mechanism and provide references for following-up researchers and research on the safety of HFCVs. The process of hydrogen permeation and test methods are firstly discussed in detail. This paper then analyzes the factors that affect the process of hydrogen permeation and the barrier mechanism of the liner material and summarizes the prediction models of gas permeation. In addition to the above analysis and comments future research on the permeability of the liner material of the type IV hydrogen storage tank is prospected.

Transporting green hydrogen by existing natural gas networks has become a practical means to accommodate curtailed wind and solar power. Restricted by pipe materials and pressure levels there is an upper limit on the hydrogen blending ratio of hydrogen-enriched compressed natural gas (HCNG) that can be transported by natural gas pipelines which affects whether the natural gas network can supply energy safely and reliably. To this end this paper investigates the effects of the intermittent and fluctuating green hydrogen produced by different types of renewable energy on the dynamic distribution of hydrogen concentration after it is blended into natural gas pipelines. Based on the isothermal steady-state simulation results of the natural gas network two convection–diffusion models for the dynamic simulation of hydrogen injections are proposed. Finally the dynamic changes of hydrogen concentration in the pipelines under scenarios of multiple green hydrogen types and multiple injection nodes are simulated on a seven-node natural gas network. The simulation results indicate that compared with the solar-power-dominated hydrogen productionblending scenario the hydrogen concentrations in the natural gas pipelines are more uniformly distributed in the wind-power-dominated scenario and the solar–wind power balance scenario. To be specific in the solar-power-dominated scenario the hydrogen concentration exceeds the limit for more time whilst the overall hydrogen production is low and the local hydrogen concentration in the natural gas network exceeds the limit for nearly 50% of the time in a day. By comparison in the wind-power-dominated scenario all pipelines can work under safe conditions. The hydrogen concentration overrun time in the solar–wind power balance scenario is also improved compared with the solar-power-dominated scenario and the limit-exceeding time of the hydrogen concentration in Pipe 5 and Pipe 6 is reduced to 91.24% and 91.99% of the solar-power-dominated scenario. This work can help verify the day-ahead scheduling strategy of the electricity-HCNG integrated energy system (IES) and provide a reference for the design of local hydrogen production-blending systems.

In order to achieve carbon neutrality in a few decades the clean energy proportion in power mix of China will significantly rise to over 90%. A consensus has been reached recently that it will be of great significance to promote hydrogen energy that is produced by variable renewable energy power generation as a mainstay energy form in view of its potential value on achieving carbon neutrality. This is because hydrogen energy is capable of complementing the power system and realizing further electrification especially in the section that cannot be easily replaced by electric energy. Power system related planning model is commonly used for mid-term and long-term planning implemented through power installation and interconnection capacity expansion optimization. In consideration of the high importance of hydrogen and its close relationship with electricity an inclusive perspective which contains both kinds of the foresaid energy is required to deal with planning problems. In this study a joint model is established by coupling hydrogen energy model in the chronological operation power planning model to realize coordinated optimization on energy production transportation and storage. By taking the carbon neutrality scenario of China as an example the author applies this joint model to deploy a scheme research on power generation and hydrogen production inter-regional energy transportation capacity and hydrogen storage among various regions. Next by taking the technology progress and cost decrease prediction uncertainty into account the main technical– economic parameters are employed as variables to carry out sensitivity analysis research with a hope that the quantitative calculation and results discussion could provide suggestion and reference to energy-related companies policy-makers and institute researchers in formulating strategies on related energy development.

In the context of green aviation as an internationally recognized solution hydrogen energy is lauded as the “ultimate energy source of the 21st century” with zero emissions at the source. Developed economies with aviation industries such as Europe and the United States have announced hydrogen energy aviation development plans successively. The study and development of high-energy hydrogen fuel cells and hydrogen energy power systems have become some of the future aviation research focal points. As a crucial component of hydrogen energy storage and delivery the design and development of a safe lightweight and efficient hydrogen storage structure have drawn increasing consideration. Using a hydrogen-powered Unmanned Aerial Vehicle (UAV) as the subject of this article the crash characteristics of the UAV’s hydrogen storage structure are investigated in detail. The main research findings are summarized as follows: (1) A series of crash characteristics analyses of the hydrogen storage structure of a hydrogen-powered UAV were conducted and the Finite Element Analysis (FEA) response of the structure under different impact angles internal pressures and impact speeds was obtained and analyzed. (2) When the deformation of the hydrogen storage structure exceeds 50 mm and the strain exceeds 0.8 an initial crack will appear at this part of the hydrogen storage structure. The emergency release valve should respond immediately to release the gas inside the tank to avoid further damage. (3) Impact angle and initial internal pressure are the main factors affecting the formation of initial cracks.

The transformation of hydrogen metallurgy is a principal means of promoting the iron and steel industry (ISI) in reaching peak and deep emissions reduction. However the environmental impact of different hydrogen production paths on hydrogen metallurgy has not been systemically discussed. To address this gap based on Long-range Energy Alternatives Planning System (LEAP) this paper constructs a bottom-up energy system model that includes hydrogen production iron and steel (IS) production and power generation. By setting three hydrogen production structure development paths namely the baseline scenario business-as-usual (BAU) scenario and clean power (CP) scenario the carbon dioxide (CO2) emissions impact of different hydrogen production paths on hydrogen metallurgy is carefully evaluated from the perspective of the whole industry and each IS production process. The results show that under the baseline scenario the hydrogen metallurgy transition will help the CO2 emissions of ISI peak at 2.19 billion tons in 2024 compared to 2.08 billion tons in 2020 and then gradually decrease to 0.78 billion tons in 2050. However different hydrogen production paths will contribute to the reduction or inhibit the reduction. In 2050 the development of electrolysis hydrogen production with renewable electricity will reduce CO2 emissions by an additional 48.76 million tons (under the CP scenario) while the hydrogen production mainly based on coal gasification and methane reforming will increase the additional 50.04 million tons CO2 emissions (under the BAU scenario). Moreover under the hydrogen production structure relying mainly on fossil and industrial by-products the technological transformation of blast furnace ironmaking with hydrogen injections will leak carbon emissions to the upstream energy processing and conversion process. Furthermore except for the 100% scrap based electric arc furnace (EAF) process the IS production process on hydrogen-rich shaft furnace direct reduced iron (hydrogen-rich DRI) have lower CO2 emissions than other processes. Therefore developing hydrogen-rich DRI will help the EAF steelmaking development to efficiently reduce CO2 emissions under scrap constraints.