China, People’s Republic
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.
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.
Investment Timing Analysis of Hydrogen-Refueling Stations and the Case of China: Independent or Co-Operative Investment?
Jun 2023
Publication
The investment in hydrogen-refueling stations (HRS) is key to the development of a hydrogen economy. This paper focuses on the decision-making for potential investors faced with the thought-provoking question of when the optimal timing to invest in HRS is. To fill the gap that exists due to the fact that few studies explain why HRS investment timing is critical we expound that earlier investment in HRS could induce the first mover advantages of the technology diffusion theory. Additionally differently from the previous research that only considered that HRS investment is just made by one individual firm we innovatively examine the HRS co-investment made by two different firms. Accordingly we compare these two optional investment modes and determine which is better considering either independent investment or co-operative investment. We then explore how the optimal HRS investment timing could be figured out under conditions of uncertainty with the real options approach. Given the Chinese HRS case under the condition of demand uncertainty the hydrogen demand required for triggering investment is viewed as the proxy for investment timing. Based on analytical and numerical results we conclude that one-firm independent investment is better than two-firm cooperative investment to develop HRS not only in terms of the earlier investment timing but also in terms of the attribute for dealing with the uncertainty. Finally we offer recommendations including stabilizing the hydrogen demand for decreasing uncertainty and accelerating firms’ innovation from both technological and strategic perspectives in order to ensure firms can make HRS investments on their own.
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.
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.
Research on Multi-Objective Energy Management of Renewable Energy Power Plant with Electrolytic Hydrogen Production
Mar 2024
Publication
This study focuses on a renewable energy power plant equipped with electrolytic hydrogen production system aiming to optimize energy management to smooth renewable energy generation fluctuations participate in peak shaving auxiliary services and increase the absorption space for renewable energy. A multi-objective energy management model and corresponding algorithms were developed incorporating considerations of cost pricing and the operational constraints of a renewable energy generating unit and electrolytic hydrogen production system. By introducing uncertain programming the uncertainty issues associated with renewable energy output were successfully addressed and an improved particle swarm optimization algorithm was employed for solving. A simulation system established on the Matlab platform verified the effectiveness of the model and algorithms demonstrating that this approach can effectively meet the demands of the electricity market while enhancing the utilization rate of renewable energies.
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.
Investigation of Hydrogen Leaks from Double Ferrule Fittings
Sep 2021
Publication
The use of hydrogen is expected to increase rapidly in the future. Leakage of hydrogen pipework are the main forms of safety problems in hydrogen utilization. In this paper a numerical model of hydrogen leakage and diffusion in pipe joints was established. The Schlieren + high-speed camera is used in experiments to observe the leakage of hydrogen in the pipe joints. In addition the shape and size of the scratches in the tube were statistically analyzed. Finally the leakage characteristics of double ferrule joints with scratches are experimentally analyzed. For the two scratch sizes the critical pressure values for the vortex transition are 0.2 MPa and 0.03 MPa. Through our experimental process some practical experience and suggestions are given.
Cradle-grave Energy Consumption, Greenhouse Gas and Acidification Emissions in Current and Future Fuel Cell Vehicles: Study Based on Five Hydrogen Production Methods in China
Jun 2022
Publication
Hydrogen fuel cell vehicles (FCVs) are regarded as a promising solution to the problems of energy security and environmental pollution. However the technology is under development and the hydrogen consumption is uncertain. The quantitative evaluation of life cycle energy consumption pollution emissions of current and future FCVs in China involves complex processes and parameters. Therefore this study addresses Life Cycle Assessment (LCA) of FCV and focuses on the key parameters of FCV production and different hydrogen production methods which include steam methane reforming catalysis decomposition methanol steam reforming electrolysis–photovoltaic (PV) and electrolysis Chinese electricity grid mix (CN). Sensitivity analysis of bipolar plate glider mass power density fuel cell system efficiency and energy control strategy are performed whilst accounting for different assumption scenarios. The results show that all impact assessment indicators will decrease by 28.8– 44.3% under the 2030 positive scenario for the production of FCVs. For cradle-grave FCVs the use of hydrogen from electrolysis operated with photovoltaic power reduces global warming potential (GWP) by almost 76.4% relative to steam methane reforming. By contrast the use of hydrogen from electrolysis operated with the Chinese electricity grid mix results in an increase in GWP of almost 158.3%.
Operation Potential Evaluation of Multiple Hydrogen Production and Refueling Integrated Stations Under DC Interconnected Environment
Feb 2022
Publication
Hydrogen production and refueling integrated station can play an important role in the development of hydrogen transportation and fuel cell vehicles and actively promote the energy transformation. By using DC system for hydrogen production and refueling the conversion links can be reduced and the system efficiency can be effectively improved. In this paper a new scheme of DC interconnection for hydrogen production and refueling integrated station is proposed and the modular modeling and operation capability evaluation method are proposed including the characteristic analysis of integrated station the modular modeling and evaluation method for multiple integrated stations under DC interconnection. The DC interconnection system of five integrated stations is constructed and operation capability improvement of integrated stations after adopting the innovative DC interconnection scheme is analyzed. On this basis the system simulation model based on MATLAB/Simulink and physical test platform are built to verify the effectiveness of the theoretical analysis.
Improve Hydrogen Economy for Vehicular Fuel Cell System via Investigation and Control of Optimal Operating Oxygen Excess Ratio
Apr 2022
Publication
This study investigates and controls the optimal operating oxygen excess ratio (OER) for PEMFC which effectively prevents oxygen starvation and improves the hydrogen economy of proton exchange membrane fuel cells (PEMFC). Firstly the PEMFC output characteristic model and the five-order nonlinear air supply system model are established. Moreover an adaptive algebraic observer was developed to observe the partial pressure of gas in PEMFC and further reconstruct OER. Secondly to achieve the minimum hydrogen consumption under the required power the reference OER is determined by analyzing the PEMFC system output power with its minimum current. Finally the super-twisting algorithm is adopted to track reference OER. Simulation results show that the average absolute observation errors of oxygen nitrogen and cathode pressures under the Highway Fuel Economy Test are 1351.1 Pa (5.1%) 1724.2 Pa (0.9%) and 409.9 Pa (1.6%) respectively. The OER adjust average absolute error is 0.03. Compared with the commonly used fixed OER (e.g. OER of 1.5 and 2.3) the optimal OER strategy can reduce the hydrogen consumption of the PEMFC system by 5.2% and 1.8% respectively. Besides a DSP hardware in loop test is conducted to show the real-time performance of the proposed optimal method.
Experimental Study on the Cycle Variation Characteristics of Direct Injection Hydrogen Engine
Jun 2022
Publication
Hydrogen energy is an important technical route to achieve carbon peak and carbon neutrality. Direct injection hydrogen engine is one of the ways of hydrogen energy application. It has the advantages of high thermal efficiency and limit/reduce abnormal combustion phenomena. In order to explore the cycle characteristics of direct injection hydrogen engine based on a 2.0L direct injection hydrogen engine an experimental study on the cycle characteristics of direct injection hydrogen engine was carried out. The experimental results show that cycle variation increases from 0.67% to 1.02% with the increasing of engine speed. The cycle variation decreases from 1.52% to 0.64% with the increasing of engine load. As the equivalence ratio increases the cycle variation first decreases significantly from 2.52% to 0.35% and then stabilizes. The ignition advance angle has a better angle to minimize the cycle variation. An experimental study on the influence of the start of injection on the cycle variation was carried out. As the engine speed/engine load is 2000rpm/4bar the cycle variation increases from 0.72% to 2.42% with the start of injection changing from -280°CA to -180°CA; then rapidly decreases to 0.99% and then increases to 2.26% with the start of injection changing from -180°CA to -100°CA. The experimental results show that SOI could cause significant influence on cycle variation because of intake valve closing and shortening mixing time and both the process of intake valve closing and lagging the SOI could cause the cycle variation to increase. The SOI remarkably affects the cycle variation at low engine load/equivalence ratio and high engine speed. This study lays the foundation for the follow-up research of hydrogen engine performance matching of the cycle variation.
A Review of the MSCA ITN ECOSTORE—Novel Complex Metal Hydrides for Efficient and Compact Storage of Renewable Energy as Hydrogen and Electricity
Mar 2020
Publication
Hydrogen as an energy carrier is very versatile in energy storage applications. Developments in novel sustainable technologies towards a CO2-free society are needed and the exploration of all-solid-state batteries (ASSBs) as well as solid-state hydrogen storage applications based on metal hydrides can provide solutions for such technologies. However there are still many technical challenges for both hydrogen storage material and ASSBs related to designing low-cost materials with low-environmental impact. The current materials considered for all-solid-state batteries should have high conductivities for Na+ Mg2+ and Ca2+ while Al3+-based compounds are often marginalised due to the lack of suitable electrode and electrolyte materials. In hydrogen storage materials the sluggish kinetic behaviour of solid-state hydride materials is one of the key constraints that limit their practical uses. Therefore it is necessary to overcome the kinetic issues of hydride materials before discussing and considering them on the system level. This review summarizes the achievements of the Marie Skłodowska-Curie Actions (MSCA) innovative training network (ITN) ECOSTORE the aim of which was the investigation of different aspects of (complex) metal hydride materials. Advances in battery and hydrogen storage materials for the efficient and compact storage of renewable energy production are discussed.
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.
Numerical Simulation on Pressure Dynamic Response Characteristics of Hydrogen Systems for Fuel Cell Vehicles
Mar 2022
Publication
A proton exchange membrane fuel cell (PEMFC) is known as one of the most promising energy sources for electric vehicles. A hydrogen system is required to provide hydrogen to the stack in time to meet the flow and pressure requirements according to the power requirements. In this study a 1-D model of a hydrogen system including the fuel cell stack was established. Two modes one with and one without a proportion integration differentiation (PID) control strategy were applied to analyze the pressure characteristics and performance of the PEMFC. The results showed that the established model could be well verified with experimental data. The anode pressure fluctuation with a PID control strategy was more stable which reduced the damage to the fuel cell stack caused by sudden changes of anode pressure. In addition the performance of the stack with the PID control mode was slightly improved. There was an inflection point for hydrogen utilization; the hydrogen utilization rate was higher under the mode without PID control when the current density was greater than 0.4 A/cm2 . What is more a hierarchical control strategy was proposed which made the pressure difference between the anode and cathode meet the stack working requirements and more importantly maintained the high hydrogen utilization of the hydrogen system.
Coupling Combustion Simulation and Primary Evaluation of an Asymmetric Motion Diesel Pilot Hydrogen Engine
Jul 2022
Publication
The thermal efficiency and combustion of conventional hydrogen engines cannot be optimized and improved by its symmetric reciprocating. This article introduces an asymmetric motion hydrogen engine (AHE) and investigates its combustion characteristics using diesel pilot ignition. A dynamic model is firstly proposed to describe the asymmetric motion of the AHE and then it is coupled into a multidimensional model for combustion simulation. The effect of asymmetric motion on the AHE combustion is also analyzed by comparing with a corresponding conventional symmetric hydrogen engine (SHE). The results show that the AHE moves slower in compression and faster in expansion than the SHE which brings about higher hydrogen-air mixing level for combustion. The asymmetric motion delays diesel injection to ignite the AHE and its combustion appears later than the SHE which leads to lower pressure and temperature for reducing NO formation. However the AHE faster expansion has a more severe post-combustion effect to reduce isovolumetric heat release level and decrease the energy efficiency.
Cost-Economic Analysis of Hydrogen for China’s Fuel Cell Transportation Field
Dec 2020
Publication
China has become a major market for hydrogen used in fuel cells in the transportation field. It is key to control the cost of hydrogen to open up the Chinese market. The development status and trends of China’s hydrogen fuel industry chain were researched. A hydrogen energy cost model was established in this paper from five aspects: raw material cost fixed cost of production hydrogen purification cost carbon trading cost and transportation cost. The economic analysis of hydrogen was applied to hydrogen transported in the form of high-pressure hydrogen gas or cryogenic liquid hydrogen and produced by natural gas coal and electrolysis of water. It was found that the cost of hydrogen from natural gas and coal is currently lower while it is greatly affected by the hydrogen purification cost and the carbon trading price. Considering the impact of future production technologies raw material costs and rising requirements for sustainable energy development on the hydrogen energy cost it is recommended to use renewable energy curtailment as a source of electricity and multi-stack system electrolyzers as large-scale electrolysis equipment in combination with cryogenic liquid hydrogen transportation or on-site hydrogen production. Furthermore participation in electricity market-oriented transactions cross-regional transactions and carbon trading can reduce the cost of hydrogen. These approaches represent the optimal method for obtaining inexpensive hydrogen.
Deep Reinforcement Learning Based Energy Management Strategy for Fuel Cell/Battery/Supercapacitor Powered Electric Vehicle
Sep 2022
Publication
Vehicles using a single fuel cell as a power source often have problems such as slow response and inability to recover braking energy. Therefore the current automobile market is mainly dominated by fuel cell hybrid vehicles. In this study the fuel cell hybrid commercial vehicle is taken as the research object and a fuel cell/ battery/supercapacitor energy topology is proposed and an energy management strategy based on a doubledelay deep deterministic policy gradient is designed for this topological structure. This strategy takes fuel cell hydrogen consumption fuel cell life loss and battery life loss as the optimization goals in which supercapacitors play the role of coordinating the power output of the fuel cell and the battery providing more optimization ranges for the optimization of fuel cells and batteries. Compared with the deep deterministic policy gradient strategy (DDPG) and the nonlinear programming algorithm strategy this strategy has reduced hydrogen consumption level fuel cell loss level and battery loss level which greatly improves the economy and service life of the power system. The proposed EMS is based on the TD3 algorithm in deep reinforcement learning and simultaneously optimizes a number of indicators which is beneficial to prolong the service life of the power system.
A Financial Model for Lithium-ion Storage in a Photovoltaic and Biogas Energy System
May 2019
Publication
Electrical energy storage (EES) such as lithium-ion (Li-ion) batteries can reduce curtailment of renewables maximizing renewable utilization by storing surplus electricity. Several techno-economic analyses have been performed on EES but few have investigated the financial performance. This paper presents a state-of-the-art financial model obtaining novel and significative financial and economics results when applied to Li-ion EES. This work is a significant step forward since traditional analysis on EES are based on oversimplified and unrealistic economic models. A discounted cash flow model for the Li-ion EES is introduced and applied to examine the financial performance of three EES operating scenarios. Real-life solar irradiance load and retail electricity price data from Kenya are used to develop a set of case studies. The EES is coupled with photovoltaics and an anaerobic digestion biogas power plant. The results show the impact of capital cost: the Li-ion project is unprofitable in Kenya with a capital cost of 1500 $/kWh but is profitable at 200 $/kWh. The study shows that the EES will generate a higher profit if it is cycled more frequently (hence a higher lifetime electricity output) although the lifetime is reduced due to degradation.
A Review of Technical Advances, Barriers, and Solutions in the Power to Hydrogen Roadmap
Oct 2020
Publication
Power to hydrogen (P2H) provides a promising solution to the geographic mismatch between sources of renewable energy and the market due to its technological maturity flexibility and the availability of technical and economic data from a range of active demonstration projects. In this review we aim to provide an overview of the status of P2H analyze its technical barriers and solutions and propose potential opportunities for future research and industrial demonstrations. We specifically focus on the transport of hydrogen via natural gas pipeline networks and end-user purification. Strong evidence shows that an addition of about 10% hydrogen into natural gas pipelines has negligible effects on the pipelines and utilization appliances and may therefore extend the asset value of the pipelines after natural gas is depleted. To obtain pure hydrogen from hydrogen-enriched natural gas (HENG) mixtures end-user separation is inevitable and can be achieved through membranes adsorption and other promising separation technologies. However novel materials with high selectivity and capacity will be the key to the development of industrial processes and an integrated membrane-adsorption process may be considered in order to produce high-purity hydrogen from HENG. It is also worth investigating the feasibility of electrochemical separation (hydrogen pumping) at a large scale and its energy analysis. Cryogenics may only be feasible when liquefied natural gas (LNG) is one of the major products. A range of other technological and operational barriers and opportunities such as water availability byproduct (oxygen) utilization and environmental impacts are also discussed. This review will advance readers’ understanding of P2H and foster the development of the hydrogen economy.
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