China, People’s Republic
Topology and Control of Fuel Cell Generation Converters
Jun 2023
Publication
Fuel cell power generation is one of the important ways of utilizing hydrogen energy which has good prospects for development. However fuel cell volt-ampere characteristics are nonlinear the output voltage is low and the fluctuation range is large and a power electronic converter matching its characteristics is required to achieve efficient and stable work. Based on the analysis of the fuel cell’s characteristic mechanism maximum power point tracking algorithm fuel cell converter characteristics application and converter control strategy the paper summarizes the general principles of the topology of fuel cell converters. In addition based on the development status of new energy hydrogen energy is organically combined with other new energy sources and the concept of 100% absorption system of new energy with green hydrogen as the main body is proposed to provide a reference for the development of hydrogen energy.
Numerical Investigation on NOx Emission of a Hydrogen-Fuelled Dual-Cylinder Free-Piston Engine
Jan 2023
Publication
The free-piston engine is a type of none-crank engine that could be operated under variable compression ratio and this provides it flexible fuel applicability and low engine emission potential. In this work several 1-D engine models including conventional gasoline engines free-piston gasoline engines and free-piston hydrogen engines have been established. Both engine performance and emission performance under engine speeds between 5–11 Hz and with different equivalent ratios have been simulated and compared. Results indicated that the free-piston engine has remarkable potential for NOx reduction and the largest reduction is 57.37% at 6 Hz compared with a conventional gasoline engine. However the figure of NOx from the hydrogen free-piston engine is slightly higher than that of the gasoline free-piston engine and the difference increases with the increase of engine speed. In addition several factors and their relationships related to hydrogen combustion in the free-piston engine have been investigated and results show that the equivalent ratio ϕ = 0.88 is a vital point that affects NOx production and the ignition advance timing could also affect combustion duration the highest in-cylinder temperature and NOx production to a large extent.
Time‐Decoupling Layered Optimization for Energy and Transportation Systems under Dynamic Hydrogen Pricing
Jul 2022
Publication
The growing popularity of renewable energy and hydrogen‐powered vehicles (HVs) will facilitate the coordinated optimization of energy and transportation systems for economic and en‐ vironmental benefits. However little research attention has been paid to dynamic hydrogen pricing and its impact on the optimal performance of energy and transportation systems. To reduce the dependency on centralized controllers and protect information privacy a time‐decoupling layered optimization strategy is put forward to realize the low‐carbon and economic operation of energy and transportation systems under dynamic hydrogen pricing. First a dynamic hydrogen pricing mechanism was formulated on the basis of the share of renewable power in the energy supply and introduced into the optimization of distributed energy stations (DESs) which will promote hydro‐ gen production using renewable power and minimize the DES construction and operation cost. On the basis of the dynamic hydrogen price optimized by DESs and the traffic conditions on roads the raised user‐centric routing optimization method can select a minimum cost route for HVs to purchase fuels from a DES with low‐cost and/or low‐carbon hydrogen. Finally the effectiveness of the proposed optimization strategy was verified by simulations.
Analysis of Hydrogen Production Potential from Waste Plastics by Pyrolysis and In Line Oxidative Steam Reforming
Oct 2021
Publication
A study was carried out on the valorization of different waste plastics (HDPE PP PS and PE) their mixtures and biomass/HDPE mixtures by means of pyrolysis and in line oxidative steam reforming. A thermodynamic equilibrium simulation was used for determining steam reforming data whereas previous experimental results were considered for setting the pyrolysis volatile stream composition. The adequacy of this simulation tool was validated using experimental results obtained in the pyrolysis and in line steam reforming of different plastics. The effect the most relevant process conditions i.e. temperature steam/plastic ratio and equivalence ratio have on H2 production and reaction enthalpy was evaluated. Moreover the most suitable conditions for the oxidative steam reforming of plastics of different nature and their mixtures were determined. The results obtained are evidence of the potential interest of this novel valorization route as H2 productions of up to 25 wt% were obtained operating under autothermal conditions.
Hydrogen Diffusion and Its Effect on Hydrogen Embrittlement in DP Steels with Different Martensite Content
Dec 2020
Publication
The hydrogen diffusion behavior and hydrogen embrittlement susceptibility of dual phase (DP) steels with different martensite content were investigated using the slow strain-rate tensile test and hydrogen permeation measurement. Results showed that a logarithmic relationship was established between the hydrogen embrittlement index (IHE) and the effective hydrogen diffusion coefficient (Deff). When the martensite content is low ferrite/ martensite interface behaves as the main trap that captures the hydrogen atoms. Also when the Deff decreases IHE increases with increasing martensite content. However when the martensite content reaches approximately 68.3% the martensite grains start to form a continuous network Deff reaches a plateau and IHE continues to increase. This is mainly related to the reduction of carbon content in martensite and the length of ferrite/martensite interface which promotes the diffusion of hydrogen atoms in martensite and the aggregation of hydrogen atoms at the ferrite/martensite interface. Finally a model describing the mechanism of microstructure-driven hydrogen diffusion with different martensite distribution was established.
A Review on Environmental Efficiency Evaluation of New Energy Vehicles Using Life Cycle Analysis
Mar 2022
Publication
New energy vehicles (NEVs) especially electric vehicles (EVs) address the important task of reducing the greenhouse effect. It is particularly important to measure the environmental efficiency of new energy vehicles and the life cycle analysis (LCA) model provides a comprehensive evaluation method of environmental efficiency. To provide researchers with knowledge regarding the research trends of LCA in NEVs a total of 282 related studies were counted from the Web of Science database and analyzed regarding their research contents research preferences and research trends. The conclusion drawn from this research is that the stages of energy resource extraction and collection carrier production and energy transportation maintenance and replacement are not considered to be research links. The stages of material equipment and car transportation and operation equipment settling and forms of use need to be considered in future research. Hydrogen fuel cell electric vehicles (HFCEVs) vehicle type classification the water footprint battery recovery and reuse and battery aging are the focus of further research and comprehensive evaluation combined with more evaluation methods is the direction needed for the optimization of LCA. According to the results of this study regarding EV and hybrid power vehicles (including plug-in hybrid electric vehicles (PHEV) fuel-cell electric vehicles (FCEV) hybrid electric vehicles (HEV) and extended range electric vehicles (EREV)) well-to-wheel (WTW) average carbon dioxide (CO2 ) emissions have been less than those in the same period of gasoline internal combustion engine vehicles (GICEV). However EV and hybrid electric vehicle production CO2 emissions have been greater than those during the same period of GICEV and the total CO2 emissions of EV have been less than during the same period of GICEV.
Numerical Simulation of Hydrogen Leakage from Fuel Cell Vehicle in an Outdoor Parking Garage
Aug 2021
Publication
It is significant to assess the hydrogen safety of fuel cell vehicles (FCVs) in parking garages with a rapidly increased number of FCVs. In the present work a Flame Acceleration Simulator (FLACS) a computational fluid dynamics (CFD) module using finite element calculation was utilized to predict the dispersion process of flammable hydrogen clouds which was performed by hydrogen leakage from a fuel cell vehicle in an outdoor parking garage. The effect of leakage diameter (2 mm 3 mm and 4 mm) and parking configurations (vertical and parallel parking) on the formation of flammable clouds with a range of 4–75% by volume was considered. The emission was assumed to be directed downwards from a Thermally Activated Pressure Relief Device (TPRD) of a 70 MPa storage tank. The results show that the 0.7 m parking space stipulated by the current regulations is less than the safety space of fuel cell vehicles. Compared with a vertical parking configuration it is safer to park FCVs in parallel. It was also shown that release through a large TPRD orifice should be avoided as the proportion of the larger hydrogen concentration in the whole flammable domain is prone to more accidental severe consequences such as overpressure.
Distinct facets to enhance the process of hydrogen production via methanol steam reforming—A review
Jan 2022
Publication
Methanol steam reforming manifests great potential for generating hydrogen owing to its lower reaction temperature (200–300 °C) and higher hydrogen/carbon ratio comparing with ethanol and methane reforming. In this case methanol steam reforming is applied in various renewable energy systems to assist the energy conversion and improve the system efficiency. The performance of methanol steam reforming reaction strongly depends on the catalysts and reactor structure. In this paper the development of the copper-based the noble metal–based and the nanomaterial catalysts were summarized by analyzing the effects of different modification methods which indicates that cutting the cost and simplifying the manufacturing process are the future goal of catalyst modification. Moreover the reaction mechanism of different catalyst type was discussed. For the reactor performance conventional miniature micro and membrane reactors were discussed and compared where conventional reactor with high CO tolerance is more suitable for industrial application while membrane reactor with high H2 purity and compact structure is ideal for fuel cell technology. The integration of the methanol steam reforming system into renewable power systems was reviewed as well. Methanol steam reforming technology is of great potential in exhaust heat recovery cogeneration system and other renewable energy field where more comprehensive research should be performed.
Modular Modeling Method and Power Supply Capability Evaluation for Integrated Hydrogen Production Stations of DC Systems
Mar 2022
Publication
Low-voltage DC distribution system has many advantages such as facilitating the access of DC loads and distributed energies and improving the network’s stability. It has become a new idea for integrated hydrogen production stations. Power supply capacity and small-signal stability are important indexes to evaluate a low-voltage DC integrated system. Based on the master–slave control mode this paper selects the typical star structure as the research object constructs the system transfer function through the scalable modular modeling method and further evaluates the impact of the high-order DC hydrogen production station integrated system on the hydrogen production capacity under the changes of the line length and master station position. The results show that the hydrogen production capacity of the system decreases gradually with the main station moving from side to inside. Finally a practical example is analyzed by MATLAB/Simulink simulation to verify the accuracy of the theory. This study can provide an effective theoretical method for the structure optimization and integrated parameter design of low-voltage DC system
A Case Study Using Hydrogen Fuel Cell as Range Extender for Lithium Battery Electric Vehicle
Mar 2024
Publication
This paper presents a case study of a lithium battery and fuel cell integrated powertrain system for a renewable energy vehicle. The performance analysis includes evaluating the energy consumption of the vehicle and the efficiency of the power generation components. When driven solely by the lithium battery at average speeds of 15 km/h and 20 km/h it was observed that speed significantly influences the travel distance of the vehicle with higher speeds resulting in lower mileage. The energy efficiency rates were found to be 89.3% and 85.7% at speeds of 15 km/h and 20 km/h respectively indicating an 18.1% decrease in efficiency from low to higher speeds. When the lithium battery is solely charged by the hydrogen fuel cell the efficiency under test conditions reaches approximately 32.5%. In the “FC + B + SC” driving mode which combines the use of the lithium battery fuel cell and solar panel to power the vehicle the travel range can be extended to 50.62 km and 42.05 km respectively representing an increase of over 50% with overall efficiencies of 63.8% and 60.7% respectively. This hybrid powertrain system exhibits rapid dynamic response high energy and power density and enables longer travel distances for the renewable energy vehicle.
Low-Carbon Strategic Planning of Integrated Energy Systems
Mar 2022
Publication
With the rapid promotion of renewable energy technologies and the trend to a low-carbon society the positive impacts of an integrated energy system that realizes various forms of energy-utilizing improvement and carbon reduction have fully emerged. Hydrogen with a decarbonized characteristic being integrated into the integrated energy system has become a viable option to offset the intermittency of renewables and decline the fossil fuel usage. An optimal planning model of a wind–photovoltaic–hydrogen storage-integrated energy system with the objective of total economic and environmental cost minimization by considering various energy technology investments is proposed. Case studies are developed to compare the economic and environmental benefits of different energy investment scenarios especially hydrogen applications. The cost–benefit analysis was carried out to prove that hydrogen investment is not a cost-competitive option but can alleviate the burden of carbon emissions somehow. Finally sensitivity analysis of key parameters of sale capacity carbon tax and renewable penetration level was performed to indicate the rational investment for a wind–photovoltaic–hydrogen storage-integrated energy system.
The Spatio-Temporal Evolution of China’s Hydrogen Fuel Cell Vehicle Innovation Network: Evidence From Patent Citation at Provincial Level
Oct 2021
Publication
Hydrogen fuel cell vehicle industry is in a rapid development stage. Studying the domestic spatial distribution of hydrogen fuel cell vehicle industry across a country especially the spatio-temporal evolution of the innovation level and position of each region in innovation network will help to understand the industry’s development trends and characteristics and avoid repeated construction. This article uses social network analysis and patent citation information of 2971 hydrogen fuel cell vehicle related invention patents owned by 218 micro-innovators across 25 provinces of China from 2001 to 2020 to construct China’s hydrogen fuel cell vehicle innovation network. Based on the dimensions of knowledge production knowledge consumption and network broker the network positions of sample provinces in three periods divided by four main national policies are classified. The main findings are as follows. 1) In China the total sales of hydrogen fuel cell vehicle and the development of supporting infrastructure are balanced and a series of national and local industrial development polices have been issued. 2) China’s hydrogen fuel cell vehicle innovation network density the proportion of universities and research institutes among the innovators and the active degree of the eastern provinces are all becoming higher. 3) The provinces in optimal network position are all from the eastern region. Shanghai and Liaoning are gradually replaced by Beijing and Jiangsu. 4) Sichuan in the western region is the only network broker based on knowledge consumption. 5) Although Zhejiang Tianjin Hebei Guangdong and Hubei are not yet in the optimal position they are outstanding knowledge producers. Specifically Guangdong is likely to climb to the optimal network position in the next period. The conclusions will help China’s provinces to formulate relevant development policies to optimize industry layout and enhance collaborative innovation in the hydrogen fuel cell vehicle industry.
A Study of Hydrogen Embrittlement of SA-372 J Class High Pressure Hydrogen Storage Seamless Cylinder (≥100 MPA)
Nov 2022
Publication
The spinning process will lead to changes in the micro-structure and mechanical properties of the materials in different positions of the high-pressure hydrogen storage cylinder which will show different hydrogen embrittlement resistance in the high-pressure hydrogen environment. In order to fully study the safety of hydrogen storage in large-volume seamless steel cylinders this chapter associates the influence of the forming process with the deterioration of a high-pressure hydrogen cylinder (≥100 MPa). The anti-hydrogen embrittlement of SA-372 grade J steel at different locations of the formed cylinders was studied experimentally in three cylinders. The hydrogen embrittlement experiments were carried out according to method A of ISO 11114-4:2005. The relationship between tensile strength microstructure and hydrogen embrittlement is analyzed which provides comprehensive and reliable data for the safety of hydrogen storage and transmission.
Environmental Benefit and Investment Value of Hydrogen-Based Wind-Energy Storage System
Mar 2021
Publication
Alongside the rapid expansion of wind power installation in China wind curtailment is also mounting rapidly due to China’s energy endowment imbalance. The hydrogen-based wind-energy storage system becomes an alternative to solve the puzzle of wind power surplus. This article introduced China’s energy storage industry development and summarized the advantages of hydrogen-based wind-energy storage systems. From the perspective of resource conservation it estimated the environmental benefits of hydrogen-based wind-energy storages. This research also builds a valuation model based on the Real Options Theory to capture the distinctive flexible charging and discharging features of the hydrogen-based wind-energy storage systems. Based on the model simulation results including the investment value and operation decision of the hydrogen energy storage system with different electricity prices system parameters and different levels of subsidies are presented. The results show that the hydrogen storage system fed with the surplus wind power can annually save approximately 2.19–3.29 million tons of standard coal consumption. It will reduce 3.31–4.97 million tons of CO2 SO2 NOx and PM saving as much as 286.6–429.8 million yuan of environmental cost annually on average. The hydrogen-based wind-energy storage system’s value depends on the construction investment and operating costs and is also affected by the meanreverting nature and jumps or spikes in electricity prices. The market-oriented reform of China’s power sector is conducive to improve hydrogen-based wind-energy storage systems’ profitability. At present subsidies are still essential to reduce initial investment and attract enterprises to participate in hydrogen energy storage projects.
Integrated Energy System Optimal Operation in Coal District With Hydrogen Heavy Trucks
Sep 2021
Publication
The coal industry contributes significantly to the social economy but the emission of greenhouse gases puts huge pressure on the environment in the process of mining transportation and power generation. In the integrated energy system (IES) the current research about the power-to-gas (P2G) technology mainly focuses on the injection of hydrogen generated from renewable energy electrolyzed water into natural gas pipelines which may cause hydrogen embrittlement of the pipeline and cannot be repaired. In this paper sufficient hydrogen energy can be produced through P2G technology and coal-to-hydrogen (C2H) of coal gasification considering the typical scenario of coal district is rich in coal and renewable energy. In order to transport the mined coal to the destination hydrogen heavy trucks have a broad space for development which can absorb hydrogen energy in time and avoid potentially dangerous hydrogen injection into pipelines and relatively expensive hydrogen storage. An optimized scheduling model of electric-gas IES is proposed based on second-order cone programming (SOCP). In the model proposed above the closed industrial loop (including coal mining hydrogen production truck transportation of coal and integrated energy systems) has been innovatively studied to consume renewable energy and coordinate multi-energy. Finally an electric-gas IES study case constructed by IEEE 30-node power system and Belgium 24-node natural gas network was used to analyze. The results show that by introducing the proposed hydrogen production technology typical daily operating costs are effectively reduced by 7.7%. Under China’s carbon emissions trading system the operating costs of hydrogen heavy trucks have been reduced by 0.95 and 4.68% respectively compared with electric vehicles and diesel trucks. Under Europe’s stricter carbon emissions trading system the percentages of cost reduction are 2.56 and 9.12% respectively. The above technical results verify the feasibility economy low carbon and effectiveness of the proposed mechanism.
Techno-economic Assessment of a Chemical Looping Splitting System for H2 and CO Co-generation
Feb 2022
Publication
The natural gas (NG) reforming is currently one of the low-cost methods for hydrogen production. However the mixture of H2 and CO2 in the produced gas inevitably includes CO2 and necessitates the costly CO2 separation. In this work a novel double chemical looping involving both combustion (CLC) and sorption-enhanced reforming (SE-CLR) was proposed towards the co-production of H2 and CO (CLC-SECLRHC) in two separated streams. CLC provides reactant CO2 and energy to feed SECLRHC which generates hydrogen in a higher purity as well as the calcium cycle to generate CO in a higher purity. Techno-economic assessment of the proposed system was conducted to evaluate its efficiency and economic competitiveness. Studies revealed that the optimal molar ratios of oxygen carrier (OC)/NG and steam/NG for reforming were recommended to be 1.7 and 1.0 respectively. The heat integration within CLC and SECLRHC units can be achieved by circulating hot OCs. The desired temperatures of fuel reactor (FR) and reforming reactor (RR) should be 850 °C and 600 °C respectively. The heat coupling between CLC and SECLRHC units can be realized via a jacket-type reactor and the NG split ratio for reforming and combustion was 0.53:0.47. Under the optimal conditions the H2 purity the H2 yield and the CH4 conversion efficiency were 98.76% 2.31 mol mol-1 and 97.96% respectively. The carbon and hydrogen utilization efficiency respectively were 58.60% and 72.45% in terms of the total hydrogen in both steam and NG. The exergy efficiency of the overall process reached 70.28%. In terms of the conventional plant capacity (75×103 t y-1 ) and current raw materials price (2500 $ t-1 ) the payback period can be 6.2 years and the IRR would be 11.5 demonstrating an economically feasible and risk resistant capability.
Using Multicriteria Decision Making to Evaluate the Risk of Hydrogen Energy Storage and Transportation in Cities
Jan 2023
Publication
Hydrogen is an environmentally friendly source of renewable energy. Energy generation from hydrogen has not yet been widely commercialized due to issues related to risk management in its storage and transportation. In this paper the authors propose a hybrid multiple-criteria decision-making (MCDM)-based method to manage the risks involved in the storage and transportation of hydrogen (RSTH). First we identified the key points of the RSTH by examining the relevant literature and soliciting the opinions of experts and used this to build a prototype of its decision structure. Second we developed a hybrid MCDM approach called the D-ANP that combined the decision-making trial and evaluation laboratory (DEMENTEL) with the analytic network process (ANP) to obtain the weight of each point of risk. Third we used fuzzy evaluation to assess the level of the RSTH for Beijing China where energy generation using hydrogen is rapidly advancing. The results showed that the skills of the personnel constituted the most important risk-related factor and environmental volatility and the effectiveness of feedback were root factors. These three factors had an important impact on other factors influencing the risk of energy generation from hydrogen. Training and technical assistance can be used to mitigate the risks arising due to differences in the skills of personnel. An appropriate logistics network and segmented transportation for energy derived from hydrogen should be implemented to reduce environmental volatility and integrated supply chain management can help make the relevant feedback more effective.
Thermodynamics and Kinetics of Hydriding and Dehydriding Reactions in Mg-based Hydrogen Storage Materials
Oct 2021
Publication
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 Role of Hydrogen in the Corrosion and Cracking of Steels - A Review
Oct 2021
Publication
In many processes of steel industrial including steel manufacture storage and service hydrogen could be absorbed into metallic materials and the absorbed hydrogen seriously impaired its corrosion resistance. This paper provides a comprehensive review on the effects of hydrogen on passive film anodic dissolution pitting corrosion and stress corrosion cracking and based on the review the mechanism by which hydrogen promotes corrosion of steel and subsequently leads to cracking has been discussed. It is envisaged that hydrogen harms the stability of the passive film and as a result escalates anode’s activation of steel eventually leading to pitting and stress corrosion cracking.
Influence of Air Distribution on Combustion Characteristics of a Micro Gas Turbine Fuelled by Hydrogen-doped Methane
Nov 2021
Publication
Adding hydrogen to the fuel can change the combustion characteristics and greatly improve the pollutants emission for the gas turbine. The numerical method was adopted to study the combustion process in a counter-flow combustor of a 100 kW micro gas turbine using methane doped by hydrogen and various distribution schemes of air flow. The combustion characteristics and pollutant emissions were explored to ascertain the influence of air distribution based on solving the validated models. It was shown that as the amount of premixed air increased in the swirling gas the range of the recirculation region became larger and the range of the high-temperature zone in the combustion chamber gradually enlarged. When the amount of premixed air was 30% the outlet temperature distribution of the combustor was excellent and the average temperature was 1172 K. Moreover the concentration of NOX gradually increased and reached a maximum value of 23.46 ppm (@15% O2) as the premixed air increased in the range of the ratio less than 40%. It was reduced to 0.717 ppm (@15% O2) when the amount of premixed air increased to 50%. These findings may support the running of the micro gas turbine using the hybrid fuel of hydrogen and methane.
The State-of-the-Art Progress on the Forms and Modes of Hydrogen and Ammonia Energy Utilization in Road Transportation
Sep 2022
Publication
The crisscross progress of transportation and energy carries the migrating track of human society development and the evolution of civilization among which the decarbonization strategy is a key issue. Traffic carbon emissions account for 16.2% of total energy carbon emissions while road traffic carbon emissions account for 11.8% of total energy carbon emissions. Therefore road traffic is a vital battlefield in attaining the goal of decarbonization. Employing clean energy as an alternative fuel is of great significance to the transformation of the energy consumption structure in road transportation. Hydrogen and ammonia are renewable energy with the characteristics of being widely distributed and clean. Both exist naturally in nature and the products of complete combustion are substances (water and nitrogen) that do not pollute the atmosphere. Because it can promote agricultural production ammonia has a long history in human society. Both have the potential to replace traditional fossil fuel energy. An overview of the advantages of hydrogen and ammonia as well as their development in different countries such as the United States the European Union Japan and other major development regions is presented in this paper. Related research topics of hydrogen and ammonia’s production storage and transferring technology have also been analyzed and collated to stimulate the energy production chain for road transportation. The current cost of green hydrogen is between $2.70–$8.80 globally which is expected to approach $2–$6 by 2030. Furthermore the technical development of hydrogen and ammonia as a fuel for engines and fuel cells in road transportation is compared in detail and the tests practical applications and commercial popularization of these technologies are summarized respectively. Opportunities and challenges coexist in the era of the renewable energy. Based on the characteristics and development track of hydrogen and ammonia the joint development of these two types of energy is meant to be imperative. The collaborative development mode of hydrogen and ammonia together with the obstacles to their development of them are both compared and discussed. Finally referring to the efforts and experiences of different countries in promoting hydrogen and ammonia in road transportation corresponding constructive suggestions have been put forward for reference. At the end of the paper a framework diagram of hydrogen and ammonia industry chains is provided and the mutual promotion development relationship of the two energy sources is systematically summarized.
Effect of Hydrogen-blended Natural Gas on Combustion Stability and Emission of Water Heater Burner
Jun 2022
Publication
To study the effect of hydrogen-blended natural gas on the combustion stability and emission of domestic gas water heater a test system is built in this paper taking a unit of the partial premixed burner commonly used in water heaters as the object. Under the heat load of 0.7~2.3kW the changes of flame shape burner temperature and pollutant emission of natural gas with hydrogen volume ratio of 0~40% are studied with independent control of primary air supply and mixing. The results show that: with the increase of hydrogen blending ratio the inner flame height increases firstly and then reduces while the change of burner temperature is opposite. The maximum inner flame height and the minimum temperature of the burner both appear at the hydrogen blending ratio of 10~20%. It can be seen that the limit of hydrogen blending ratio which can maintain the burner operate safely and stably under rated heat load is 40% through the maximum temperature distribution on the burner surface. The CO emission in the flue gas gradually decreases with the increase of hydrogen blending ratio while the NOx emission fluctuates slightly when the hydrogen blending ratio is less than 20% but then decreases gradually.
Hydrogen Safety Prediction and Analysis of Hydrogen Refueling Station Leakage Accidents and Process Using Multi-Relevance Machine Learning
Oct 2021
Publication
Hydrogen energy vehicles are being increasingly widely used. To ensure the safety of hydrogenation stations research into the detection of hydrogen leaks is required. Offline analysis using data machine learning is achieved using Spark SQL and Spark MLlib technology. In this study to determine the safety status of a hydrogen refueling station we used multiple algorithm models to perform calculation and analysis: a multi-source data association prediction algorithm a random gradient descent algorithm a deep neural network optimization algorithm and other algorithm models. We successfully analyzed the data including the potential relationships internal relationships and operation laws between the data to detect the safety statuses of hydrogen refueling stations.
Hydrogen Production: State of Technology
May 2020
Publication
Presently hydrogen is for ~50% produced by steam reforming of natural gas – a process leading to significant emissions of greenhouse gas (GHG). About 30% is produced from oil/naphtha reforming and from refinery/chemical industry off-gases. The remaining capacity is covered for 18% from coal gasification 3.9% from water electrolysis and 0.1% from other sources. In the foreseen future hydrogen economy green hydrogen production methods will need to supply hydrogen to be used directly as fuel or to generate synthetic fuels to produce ammonia and other fertilizers (viz. urea) to upgrade heavy oils (like oil sands) and to produce other chemicals. There are several ways to produce H2 each with limitations and potential such as steam reforming electrolysis thermal and thermo-chemical water splitting dark and photonic fermentation; gasification and catalytic decomposition of methanol. The paper reviews the fundamentals and potential of these alternative process routes. Both thermo-chemical water splitting and fermentation are marked as having a long term but high "green" potential.
Hydrogen-Enriched Compressed Natural Gas Network Simulation for Consuming Green Hydrogen Considering the Hydrogen Diffusion Process
Sep 2022
Publication
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.
Heat Transfer Models for Refueling Safety of Hydrogen Vehicle
Sep 2021
Publication
Due to the simple structure and quick refueling process of the compressed hydrogen storage tank it is widely used in fuel cell vehicles at present. However temperature rise may lead to a safety problem during charging of a compressed hydrogen storage tank. To ensure the refueling safety the thermal effects need to be studied carefully during hydrogen refueling process. In this paper based on the mass and energy balance equations a general heat transfer model for refueling process of compressed hydrogen storage tank is established. According to the geometric model of the tank wall structure we have built three lumped parameter models: single-zone (hydrogen) dual-zone (hydrogen and tank wall) and triple-zone (hydrogen tank wall liner and shell) model. These three lumped parameter models are compared with U.S. Naval gas charging model and SAE MC method based refueling model. Under adiabatic and diathermic conditions four models are built in Matlab/Simulink software to simulate the hydrogen refueling process under corresponding conditions. These four models are: single-zone singletemperature (hydrogen) dual-zone single-temperature (hydrogen) dual-zone dual-temperature (hydrogen and tank wall temperatures) and triple-zone triple-temperature (hydrogen tank wall liner and tank wall shell temperatures). By comparing the analytical solution and numerical solution the temperature rise of the compressed hydrogen storage tank can be described. The analytical and numerical solutions on the heat transfer during hydrogen refueling process will provide theoretical guidance at actual refueling station so as to improve the refueling efficiency and to enhance the refueling safety.
A Study of Thermoelectric Generation Coupled with Methanol Steam Reforming for Hydrogen Production
Nov 2022
Publication
Waste heat recovery was considered as a promising candidate for energy conservation and emission reduction. Methanol steam reforming was considered to be an effective means for hydrogen production because of its advantages. In this work a micro reactor was constructed and thermoelectric generation coupled with hydrogen production from methanol steam reforming was innovatively used to recycle waste heat which was simulated by hot air from a hot air gun. The waste heat was converted into electricity and hydrogen at the same time. The characteristic of thermoelectric generation coupled with methanol steam reforming was investigated. It was experimentally verified that both the hydrogen production rate and methanol conversion increased with the increasing inlet temperature but thermal efficiency increased firstly and then decreased with the increasing temperature. The methanol steam reforming could effectively maintain cold side temperature distribution of thermoelectric generation. In the case of the thermoelectric module (1) the highest temperature difference of 37 ◦C was determined and the maximum open circuit voltage of 2 V was observed. The highest methanol conversion of 64.26% was achieved at a space velocity of 0.98 h−1 when the temperature was 543 K comprehensively considering the CO content and thermal efficiency.
Techno-economic Assessment of Electrolytic Hydrogen in China Considering Wind-solar-load Characteristic
Jan 2023
Publication
Hydrogen production by electrolysis is considered an essential means of consuming renewable energy in the future. However the current assessment of the potential of renewable energy electrolysis for hydrogen production is relatively simple and the perspective is not comprehensive. Here we established a Combined Wind and Solar Electrolytic Hydrogen system considering the influence of regional wind-solar-load characteristics and transmission costs to evaluate the hydrogen production potential of 31 provincial-level regions in China in 2050. The results show that in 2050 the levelized cost of hydrogen (LCOH) in China’s provincial regions will still be higher than 10 ¥/kg which is not cost-competitive compared to the current hydrogen production from fossil fuels. It is more cost-effective to deploy wind turbines than photovoltaic in areas with similar wind and solar resources or rich in wind resources. Wind-solar differences impact LCOH equipment capacity configuration and transmission cost composition while load fluctuation significantly impacts LCOH and electricity storage configuration. In addition the sensitivity analysis of 11 technical and economic parameters showed differences in the response performance of LCOH changes to different parameters and the electrolyzer conversion efficiency had the most severe impact. The analysis of subsidy policy shows that for most regions (except Chongqing and Xizang) subsidizing the unit investment cost of wind turbines can minimize LCOH. Nevertheless from the perspective of comprehensive subsidy effect subsidy cost and hydrogen energy development it is more cost-effective to take subsidies for electrolysis equipment with the popularization of hydrogen
Research on the Flexibility Margin of an Electric–Hydrogen Coupling Energy Block Based on Model Predictive Control
Apr 2022
Publication
Hydrogen energy plays an important role in the transformation of low-carbon energy and electric–hydrogen coupling will become a typical energy scenario. Aiming at the operation flexibility of a low-carbon electricity–hydrogen coupling system with high proportion of wind power and photovoltaic this work studies the flexibility margin of an electricity–hydrogen coupling energy block based on model predictive control. By analyzing the power exchange characteristics of heterogeneous energy the homogenization models of various heterogeneous energy sources are established. According to the analysis of power system flexibility margin three dimensions of flexibility margin evaluation indexes are defined from the dimension of system operation and an electricity–hydrogen coupling energy block scheduling model is established. The model predictive control algorithm is used to optimize the power balance operation of the electro–hydrogen coupling energy block and the flexibility margin of the energy block is quantitatively analyzed and calculated. Through the example analysis it is verified that the calculation method proposed in this article can not only realize the online power balance optimization of the electric–hydrogen coupling energy block but also effectively quantify the operation flexibility margin of the electric–hydrogen coupling energy block.
A Prompt Decarbonization Pathway for Shipping: Green Hydrogen, Ammonia, and Methanol Production and Utilization in Marine Engines
Mar 2023
Publication
The shipping industry has reached a higher level of maturity in terms of its knowledge and awareness of decarbonization challenges. Carbon-free or carbon-neutralized green fuel such as green hydrogen green ammonia and green methanol are being widely discussed. However little attention has paid to the green fuel pathway from renewable energy to shipping. This paper therefore provides a review of the production methods for green power (green hydrogen green ammonia and green methanol) and analyzes the potential of green fuel for application to shipping. The review shows that the potential production methods for green hydrogen green ammonia and green methanol for the shipping industry are (1) hydrogen production from seawater electrolysis using green power; (2) ammonia production from green hydrogen + Haber–Bosch process; and (3) methanol production from CO2 using green power. While the future of green fuel is bright in the short term the costs are expected to be higher than conventional fuel. Our recommendations are therefore as follows: improve green power production technology to reduce the production cost; develop electrochemical fuel production technology to increase the efficiency of green fuel production; and explore new technology. Strengthening the research and development of renewable energy and green fuel production technology and expanding fuel production capacity to ensure an adequate supply of low- and zero-emission marine fuel are important factors to achieve carbon reduction in shipping.
Super Short Term Combined Power Prediction for Wind Power Hydrogen Production
Sep 2022
Publication
A combined ultra-short-term wind power prediction strategy with high robustness based on least squares support vector machine (LSSVM) has been proposed in order to solve the wind abandonment caused by wind power randomness and realize efficient hydrogen production under wide power fluctuation. Firstly the original wind power data is decomposed into sub-modes with different bandwidth by variational modal decomposition (VMD) which reduces the influence of random noise and mode mixing significantly. Then dragonfly algorithm (DA) is introduced to optimize LSSVM kernel function and the combined ultra-short-term wind power prediction strategy which meets the time resolution and accuracy requirements of electrolytic cell control has been established finally. This model is validated by a wind power hydrogen production demonstration project output in the middle east of China. The superior prediction accuracy for high volatility wind power data is verified and the algorithm provides theoretical basis to improve the control of wind power hydrogen production system
A Robust Scheduling Methodology for Integrated Electric-Gas System Considering Dynamics of Natural Gas Pipeline and Blending Hydrogen
Mar 2022
Publication
As smart grid develops and renewables advance challenges caused by uncertainties of renewables have been seriously threatening the energy system’s safe operation. Nowadays the integrated electric-gas system (IEGS) plays a significant role in promoting the flexibility of modern grid owing to its great characteristic in accommodating renewable energy and coping with fluctuation and uncertainty of the system. And hydrogen as an emerging and clean energy carrier can further enhance the energy coupling of the IEGS and promote carbon neutralization with the development of power-to-hydrogen (P2H) technology and technology of blending hydrogen in the natural gas system. Dealing with the uncertainty of renewables a robust schedule optimization model for the integrated electric and gas systems with blending hydrogen (IEGSH) considering the dynamics of gas is proposed and the iterative solving method based on column-and-constraint generation (C&CG) algorithm is implemented to solve the problem. Case studies on the IEGSH consisting of IEEE 39-bus power system and 27-node natural gas system validate the effectiveness of the dynamic energy flow model in depicting the transient process of gas transmission. The effectiveness of the proposed robust day-ahead scheduling model in dealing with the intra-day uncertainty of wind power is also verified. Additionally the carbon emission reduction resulting from the blending of hydrogen is evaluated.
Novel Ways for Hydrogen Production Based on Methane Steam and Dry Reforming Integrated with Carbon Capture
Sep 2022
Publication
The combination of methane steam reforming technology and CCS (Carbon Capture and Storage) technology has great potential to reduce carbon emissions in the process of hydrogen production. Different from the traditional idea of capturing CO2 (Carbon Dioxide) in the exhaust gas with high work consumption this study simultaneously focuses on CO2 separation from fuel gas and recycling. A new hydrogen production system is developed by methane steam reforming coupled with carbon capture. Separated and captured high-purity carbon dioxide could be recycled for methane dry reforming; on this basis a new methane-dry-reforming-driven hydrogen production system with a carbon dioxide reinjection unit is innovatively proposed. In this study the energy flow and irreversible loss in the two newly developed systems are analyzed in detail through energy and exergy balance analysis. The advantages are explored from the perspective of hydrogen production rate natural gas consumption and work consumption. In addition in consideration of the integrated performance an optimal design analysis was conducted. In terms of hydrogen production the new system based on dry reforming is better with an advantage of 2.41%; however it is worth noting that the comprehensive thermal performance of the new steam reforming system is better reaching 10.95%. This study provides new ideas for hydrogen production from a low carbon emission perspective and also offers a new direction for future distributed energy system integration.
Combustion Characterization of Hybrid Methane-hydrogen Gas in Domestic Swirl Stoves
Oct 2022
Publication
Combustion of hybrid natural gas (methane) and hydrogen mixture in domestic swirl stoves has been characterized using hot-state experiments and numerical analysis. The detailed combustion mechanism of methane and hydrogen (GRI-Mech 3.0) has been simplified to obtain reduced number of chemical reactions involved (82 % reduction). The novel simplified combustion mechanism developed has been used to obtain combustion characteristics of hybrid methane-hydrogen mixture. The difference between the calculations from the detailed and the simplified mechanisms has been found to be Combustion of hybrid natural gas (methane) and hydrogen mixture in domestic swirl stoves has been characterized using hot-state experiments and numerical analysis. The detailed combustion mechanism of methane and hydrogen (GRI-Mech 3.0) has been simplified to obtain reduced number of chemical reactions involved (82 % reduction). The novel simplified combustion mechanism developed has been used to obtain combustion characteristics of hybrid methane-hydrogen mixture. The difference between the calculations from the detailed and the simplified mechanisms has been found to be <1 %. A numerical model based on the simplified combustion model is developed rigorously tested and validated against hot-state tests. The results depict that the maximum difference in combustion zone’s average temperature is <13 %. The investigations have then been extended to hybrid methane-hydrogen mixtures with varying volume fraction of hydrogen. The results show that for a mixture containing 15 % hydrogen the release of CO due to combustion reduces by 25 % while the combustion zone’s average temperature reduces by 6.7 %. The numerical results and hot-state tests both confirm that the temperature remains stable when hybrid methane-hydrogen mixture is used in domestic swirl gas stoves demonstrating its effectiveness in cooking processes.
The Direct Reduction of Iron Ore with Hydrogen
Aug 2022
Publication
The steel industry represents about 7% of the world’s anthropogenic CO2 emissions due to the high use of fossil fuels. The CO2 -lean direct reduction of iron ore with hydrogen is considered to offer a high potential to reduce CO2 emissions and this direct reduction of Fe2O3 powder is investigated in this research. The H2 reduction reaction kinetics and fluidization characteristics of fine and cohesive Fe2O3 particles were examined in a vibrated fluidized bed reactor. A smooth bubbling fluidization was achieved. An increase in external force due to vibration slightly increased the pressure drop. The minimum fluidization velocity was nearly independent of the operating temperature. The yield of the direct H2 -driven reduction was examined and found to exceed 90% with a maximum of 98% under the vibration of ~47 Hz with an amplitude of 0.6 mm and operating temperatures close to 500 ◦C. Towards the future of direct steel ore reduction cheap and “green” hydrogen sources need to be developed. H2 can be formed through various techniques with the catalytic decomposition of NH3 (and CH4 ) methanol and ethanol offering an important potential towards production cost yield and environmental CO2 emission reductions.
Design Strategies for Large Current Density Hydrogen Evolution Reaction
Apr 2022
Publication
Hydrogen energy is considered one of the cleanest and most promising alternatives to fossil fuel because the only combustion product is water. The development of water splitting electrocatalysts with Earth abundance cost-efficiency and high performance for large current density industrial applications is vital for H2 production. However most of the reported catalysts are usually tested within relatively small current densities (< 100 mA cm−2 ) which is far from satisfactory for industrial applications. In this minireview we summarize the latest progress of effective non-noble electrocatalysts for large current density hydrogen evolution reaction (HER) whose performance is comparable to that of noble metal-based catalysts. Then the design strategy of intrinsic activities and architecture design are discussed including self-supporting electrodes to avoid the detachment of active materials the superaerophobicity and superhydrophilicity to release H2 bubble in time and the mechanical properties to resist destructive stress. Finally some views on the further development of high current density HER electrocatalysts are proposed such as scale up of the synthesis process in situ characterization to reveal the micro mechanism and the implementation of catalysts into practical electrolyzers for the commercial application of as-developed catalysts. This review aimed to guide HER catalyst design and make large-scale hydrogen production one step further.
P2H Modeling and Operation in the Microgrid Under Coupled Electricity–Hydrogen Markets
Dec 2021
Publication
The uncertainty and volatility of wind power have led to large-scale wind curtailment during grid connections. The adoption of power-to-hydrogen (P2H) system in a microgrid (MG) can mitigate the renewable curtailment by hydrogen conversion and storage. This paper conducts unified modeling for different types of P2H systems and considers the multi-energy trading in a hydrogen-coupled power market. The proposed bi-level equilibrium model is beneficial to minimize the energy cost of microgrids. Firstly a microgrid operation model applied to different P2H systems including an alkaline electrolysis cell (AEC) a proton exchange membrane electrolysis cell (PEMEC) or a solid oxide electrolysis cell (SOEC) is proposed at the upper level. Secondly an electricity market–clearing model and a hydrogen market model are constructed at the lower level. Then the diagonalization algorithm is adopted to solve the multi-market equilibrium problem. Finally case studies based on an IEEE 14-bus system are conducted to validate the proposed model and the results show that the microgrid with a P2H system could gain more profits and help increase the renewable penetration.
Impacts of Low-Carbon Targets and Hydrogen Production Alternatives on Energy Supply System Transition: An Infrastructure-Based Optimization Approach and a Case Study of China
Jan 2021
Publication
Low-carbon transition pathways oriented from different transition targets would result in a huge variation of energy system deployment and transition costs. Hydrogen is widely considered as an imperative energy carrier to reach carbon neutral targets. However hydrogen production either from non-fossil power or fossil fuels with carbon capture is closely linked with an energy supply system and has great impacts on its structure. Identifying an economically affordable transition pathway is attractive and energy infrastructure is critical due to massive investment and long life-span. In this paper a multi-regional multi-period and infrastructure-based model is proposed to quantify energy supply system transition costs with different low-carbon targets and hydrogen production alternatives and China is taken as a case study. Results show that fulfilling 2-degree and 1.5-degree temperature increase targets would result in 84% and 151% increases in system transition costs 114% and 246% increases in infrastructure investment and 211% and 339% increases in stranded investment compared to fulfilling stated policy targets. Producing hydrogen from coal would be economical when carbon capture and sequestration cost is lower than 437 yuan per tonne and reduce infrastructure investment and stranded coal investment by 16% and 35% respectively than producing hydrogen from renewable power.
Industrial Status, Technological Progress, Challenges, and Prospects of Hydrogen Energy
Apr 2022
Publication
Under the requirements of China's strategic goal of "carbon peaking and carbon neutrality" as a renewable clean and efficient secondary energy source hydrogen benefits from abundant resources a wide variety of sources a high combustion calorific value clean and non-polluting various forms of utilization energy storage mediums and good security etc. It will become a realistic way to help energy transportation petrochemical and other fields to achieve deep decarbonization and will turn into an important replacement energy source for China to build a modern clean energy system. It is clear that accelerating the development of hydrogen energy has become a global consensus. In order to provide a theoretical support for the accelerated transformation of hydrogen-related industries and energy companies and provide a basis and reference for the construction of "Hydrogen Energy China" this paper describes main key technological progresses in the hydrogen industry chain such as hydrogen production storage transportation and application. The status and development trends of hydrogen industrialization are analyzed and then the challenges faced by the development of the hydrogen industry are discussed. At last the development and future of the hydrogen industry are prospected. The following conclusions are achieved. (1) Hydrogen technologies of our country will become mature and enter the road of industrialization. The whole industry chain system of the hydrogen industry is gradually being formed and will realize the leap-forward development from gray hydrogen blue hydrogen to green hydrogen. (2) The overall development of the entire hydrogen industry chain such as hydrogen production storage and transportation fuel cells hydrogen refueling stations and other scenarios should be accelerated. Besides in-depth integration and coordination with the oil and gas industry needs more attention which will rapidly promote the high-quality development of the hydrogen industry system. (3) The promotion and implementation of major projects such as "north-east hydrogen transmission" "west-east hydrogen transmission" "sea hydrogen landing" and utilization of infrastructures such as gas filling stations can give full play to the innate advantages of oil and gas companies in industrial chain nodes such as hydrogen production and refueling etc. which can help to achieve the application of "oil gas hydrogen and electricity" four-station joint construction form a nationwide hydrogen resource guarantee system and accelerate the planning and promotion of the "Hydrogen Energy China" strategy.
Simulation and Study of PEMFC System Directly Fueled by Ammonia Decomposition Gas
Mar 2022
Publication
Ammonia can be stored as a liquid under relatively easy conditions (Ambient temperature by applying 10 bar or Ambient pressure with the temperature of 239 K). At the same time liquid ammonia has a high hydrogen storage density and is therefore a particularly promising carrier for hydrogen storage. At the same time the current large-scale industrial synthesis of ammonia has long been mature and in the future it will be possible to achieve a zero-emission ammonia regeneration cycle system by replacing existing energy sources with renewable ones. Ammonia does not contain carbon and its use in fuel cells can avoid NOx production during energy release. high temperature solid oxide fuel cells can be directly fueled by ammonia and obtain good output characteristics but the challenges inherent in high temperature solid oxide fuel cells greatly limit the implementation of this option. Whereas PEMFC has gained initial commercial use however for PEMFC ammonia is a toxic gas so the general practice is to convert ammonia to pure hydrogen. Ammonia to hydrogen requires decomposition under high temperature and purification which increases the complexity of the fuel system. In contrast PEMFC that can use ammonia decomposition gas directly can simplify the fuel system and this option has already obtained preliminary experimental validation studies. The energy efficiency of the system obtained from the preliminary validation experiments is only 34–36% which is much lower than expected. Therefore this paper establishes a simulation model of PEMFC directly using ammonia decomposition gas as fuel to study the maximum efficiency of the system and the effect of the change of system parameters on the efficiency and the results show that the system efficiency can reach up to 45% under the condition of considering certain heat loss. Increasing the ammonia decomposition reaction temperature decreases the system efficiency but the effect is small and the system efficiency can reach 44% even at a temperature of 850°C. The results of the study can provide a reference for a more scientific and quantitative assessment of the potential value of direct ammonia decomposition gas-fueled PEMFC.
Study on Enhancing Hydrogen Production Potential from Renewable Energy in Multi-terminal DC System
Aug 2021
Publication
Renewable energy complementary hydrogen production can enhance the full consumption of renewable energy and reduce the abandonment of wind and solar power. The integration of renewable energy and hydrogen production equipment through existing multi-terminal DC systems can reduce new power lines construction and save investment in distribution equipment. For integrated renewable energy/hydrogen energy in an existing multi-terminal DC system this paper investigates its potential of hydrogen production based on renewable energy while ensuring the normal performance of the existing system being not affected. The typical structure and control strategy of the integrated renewable energy/hydrogen energy in multi-terminal DC system are firstly described. Then the state space model of the system is constructed and the key parameters affecting the hydrogen production capacity are studied by using the eigenvalues analysis method. Finally the corresponding system simulation model and test platform are built and the theoretical analysis results are verified and the potential of using multi-terminal DC system to enhance hydrogen production is quantitatively analyzed. The proposed scheme can enhance the hydrogen production potential from renewable energy meanwhile the normal performance of the existing system is not affected.
Experimental Study of the Feasibility of In‐Situ Hydrogen Generation from Gas Reservoir
Nov 2022
Publication
Due to there is no better way to exploit depleted gas reservoirs and hydrogen can generate from natural gas combustion. In this paper the possibility of in‐situ hydrogen generation in air injected gas reservoirs was determined through pseudo dynamic experiments. The study indicated that highertemperature and steam/methane ratio can generate more hydrogen and the temperature should not be lower than 600 °C within gas reservoirs. The debris has positive catalysis for hydrogen generation. The maximum mole fraction of hydrogen was 26.63% at 600 °C.
Research on the Primary Frequency Regulation Control Strategy of a Wind Storage Hydrogen-Generating Power Station
Nov 2022
Publication
Wind curtailment and weak inertia characteristics are two factors that shackle the permeability of wind power. An electric hydrogen production device consumes electricity to produce hydrogen under normal working conditions to solve the problem of abandoning wind. When participating in frequency regulation it serves as a load reduction method to assist the system to rebuild a power balance and improve the wind power permeability. However due to its own working characteristics an electric hydrogen production device cannot undertake the high-frequency component of the frequency regulation power command; therefore an energy storage device was selected to undertake a high-frequency power command to assist the electric hydrogen production device to complete the system frequency regulation. This paper first proposes and analyzes the architecture of a wind storage hydrogen-generating station for centralized hydrogen production with a distributed energy storage and proposes the virtual inertia and droop characteristic mechanism of the wind storage hydrogen-generating station to simulate a synchronous unit. Secondly an alkaline electrolysis cell suitable for large-scale engineering applications is selected as the research object and its mathematical model is established the matching between different energy storage devices and their cooperation in power grid frequency regulation is analyzed and a super capacitor is selected. A control strategy for the wind storage hydrogen-generating power station to participate in power grid frequency regulation with a wide time scale is then proposed. Using the first-order low-pass filter the low-frequency component of the frequency regulation power command is realized by an electric hydrogen production device load reduction and a high-frequency component is realized by the energy storage device. Finally the effectiveness and rationality of the proposed control strategy are verified by establishing the simulation model of the wind storage hydrogen-generating power station with different initial wind speed states comparing the system frequency dip values under the proposed multi-energy cooperative control strategy and a single energy device control strategy.
Research on Motor Rotor Loss of High-Speed Air Compressor in the Application of Hydrogen Fuel Cell Vehicle
Feb 2023
Publication
As an important component of hydrogen fuel cell vehicles the air compressor with an air foil bearing rotates at tens of thousands of revolutions per minute. The heat generation concentration problem caused by the high-speed motor loss seriously affects the safe and normal operation of the motor so it is very important to clarify the loss distribution of the high-speed motor and adopt a targeted loss reduction design for air compressor heat dissipation. In this paper for an air compressor with a foil bearing with a rated speed of 80000 rpm an empirical formula and a three-dimensional transient magnetic field finite element model are used to model and calculate the air friction loss stator core loss winding loss and permanent magnet eddy current loss. The accuracy of the analytical calculation method is verified by torque test experiments under different revolutions and the average simulation accuracy can reach 91.1%. Then the distribution of the air friction loss stator core loss winding loss and eddy current loss of the air compressor motor at different revolutions is obtained by using this method. The results show that the proposed method can effectively calculate the motor rotor loss of a high-speed air compressor with air foil bearing. Although the motor efficiency increases with the increase in motor speed the absolute value of loss also increases with the increase in motor speed. Stator core loss and air friction loss are the main sources of loss accounting for 55.64% and 29% of the total motor loss respectively. The electromagnetic loss of winding the eddy current and other alloys account for a relatively small proportion which is 15% in total. The conclusions obtained in this paper can effectively guide calculations of motor loss the motor heat dissipation design of a high-speed air compressor with an air foil bearing.
Effect of H2 on Blast Furnace Ironmaking: A Review
Nov 2022
Publication
Under the background of “carbon peaking” and “carbon neutralization” the green transformation of iron and steel enterprises is imminent. The hydrogen-rich smelting technology of blast furnaces is very important for reducing energy consumption and CO2 emission in ironmaking systems and it is one of the important directions of green and low-carbon development of iron and steel enterprises. In this paper the research status of the thermal state reduction mechanism of iron-bearing burden coke degradation behavior and formation of the cohesive zone in various areas of blast furnace after hydrogen-rich smelting is summarized which can make a more clear and comprehensive understanding for the effect of H2 on blast furnace ironmaking. Meanwhile based on the current research situation it is proposed that the following aspects should be further studied in the hydrogen-rich smelting of blast furnaces: (1) the utilization rate of hydrogen and degree of substitution for direct reduction (2) combustion behavior of fuel in raceway (3) control of gas flow distribution in the blast furnace (4) operation optimization of the blast furnace.
Intelligent Damping Control of Renewable Energy/Hydrogen Energy DC Interconnection System
Oct 2022
Publication
Renewable energy DC hydrogen production has become a new development trend. Due to the interaction between the weak damping of DC network and the negative impedance characteristics of power supply of hydrogen production the actual available power of renewable and hydrogen energy DC interconnection system will be lower than its rated setting value. To solve this problem this paper proposes an intelligent damping control to realize the rated power operation of hydrogen generation power source and significantly improve the hydrogen generation performance. In this paper the nonlinear model under typical control strategies is established in order to adapt to different degrees of disturbance and the damping controller is designed based on state feedback including feedback control law and damping generation formula. On this basis an intelligent method of damping control is proposed to support rapid decision-making. Finally the intelligent damping control method is verified by simulation analysis. It realizes rated power of power supply of hydrogen production by generating only a small amount of damping power and superimposing it on the hydrogen production power
Deep Decarbonization of the Indian Economy: 2050 Prospects for Wind, Solar, and Green Hydrogen
May 2022
Publication
The paper explores options for a 2050 carbon free energy future for India. Onshore wind and solar sources are projected as the dominant primary contributions to this objective. The analysis envisages an important role for so-called green hydrogen produced by electrolysis fueled by these carbon free energy sources. This hydrogen source can be used to accommodate for the intrinsic variability of wind and solar complementing opportunities for storage of power by batteries and pumped hydro. The green source of hydrogen can be used also to supplant current industrial uses of grey hydrogen produced in the Indian context largely from natural gas with important related emissions of CO2. The paper explores further options for use of green hydrogen to lower emissions from otherwise difficult to abate sectors of both industry and transport. The analysis is applied to identify the least cost options to meet India’s zero carbon future.
A Comprehensive Review of Electrochemical Hybrid Power Supply Systems and Intelligent Energy Managements for Unmanned Aerial Vehicles in Public Services
Jun 2022
Publication
The electric unmanned aerial vehicles (UAVs) are rapidly growing due to their abilities to perform some difficult or dangerous tasks as well as many public services including real-time monitoring wireless coverage search and rescue wildlife surveys and precision agriculture. However the electrochemical power supply system of UAV is a critical issue in terms of its energy/power densities and lifetime for service endurance. In this paper the current power supply systems used in UAVs are comprehensively reviewed and analyzed on the existing power configurations and the energy management systems. It is identified that a single type of electrochemical power source is not enough to support a UAV to achieve a long-haul flight; hence a hybrid power system architecture is necessary. To make use of the advantages of each type of power source to increase the endurance and achieve good performance of the UAVs the hybrid systems containing two or three types of power sources (fuel cell battery solar cell and supercapacitor) have to be developed. In this regard the selection of an appropriate hybrid power structure with the optimized energy management system is critical for the efficient operation of a UAV. It is found that the data-driven models with artificial intelligence (AI) are promising in intelligent energy management. This paper can provide insights and guidelines for future research and development into the design and fabrication of the advanced UAV power systems.
Combined Soft Templating with Thermal Exfoliation Toward Synthesis of Porous g-C3N4 Nanosheets for Improved Photocatalytic Hydrogen Evolution
Apr 2021
Publication
Insufficient active sites and fast charge carrier recombination are detrimental to photocatalytic activity of graphitic carbon nitride (g-C3N4). In this work a combination of pore creating with thermal exfoliation was employed to prepare porous g-C3N4 nanosheets for photocatalytic water splitting into hydrogen. Hexadecyl trimethyl ammonium chloride (CTAC) as the soft template promoted the formation of porous g-C3N4 during the thermal condensation of melamine. On further post-synthesis calcination the porous g-C3N4 aggregates were exfoliated into discrete nanosheets accompanied by an increase in specific surface area and defects. Optimal porous g-C3N4 nanosheets achieved 3.6 times the photocatalytic hydrogen evolution rate for bulk counterpart. The enhanced photocatalytic activity may be ascribed to TCN-1%CTAC has larger specific surface area stronger optical absorption intensity and higher photogenerated electron–hole separation efficiency. The external quantum efficiency of TCN-1%CTAC was measured to be 3.4% at 420 nm. This work provides a simple combinatorial strategy for the preparation of porous g-C3N4 nanosheets with low cost environmental friendliness and enhanced photocatalytic activity.
Aldehyde Replacement Advances Efficient Hydrogen Production in Electrolyser
Mar 2022
Publication
The high energy consumption and production of undesired oxygen greatly restrict the wide adoption of water electrolysis for hydrogen production. In a paper recently published in Nature Catalysis Wang and coworkers rationally introduce aldehydes for oxidation at anode to replace oxygen evolution reaction which can produce hydrogen and value-added products at low potential realizing efficient bipolar hydrogen production with high-purity. Moreover these aldehydes are biomass-derived and contribute to sustainable hydrogen production
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