China, People’s Republic
A Critical Review on the Principles, Applications, and Challenges of Waste-to-hydrogen Technologies
Sep 2020
Publication
Hydrogen sourced from energy recovery processes and conversion of waste materials is a method of providing both a clean fuel and a sustainable waste management alternative to landfill and incineration. The question is whether waste-to–hydrogen can become part of the zero-carbon future energy mix and serve as one of the cleaner hydrogen sources which is economically viable and environmentally friendly. This work critically assessed the potential of waste as a source of hydrogen production via various thermochemical (gasification and pyrolysis) and biochemical (fermentation and photolysis) processes. Research has shown hydrogen production yields of 33.6 mol/kg and hydrogen concentrations of 82% from mixed waste feedstock gasification. Biochemical methods such as fermentation can produce hydrogen up to 418.6 mL/g. Factors including feedstock quality process requirements and technology availability were reviewed to guide technology selection and system design. Current technology status and bottlenecks were discussed to shape future development priorities. These bottlenecks include expensive production and operation processes heterogeneous feedstock low process efficiencies inadequate management and logistics and lack of policy support. Improvements to hydrogen yields and production rates are related to feedstock processing and advanced energy efficiency processes such as torrefaction of feedstock which has shown thermal efficiency of gasification up to 4 MJ/kg. This will affect the economic feasibility and concerns around required improvements to bring the costs down to allow waste to viewed as a serious competitor for hydrogen production. Recommendations were also made for financially competitive waste-to-hydrogen development to be part of a combined solution for future energy needs.
Progress in Biofuel Production from Gasification
May 2017
Publication
Biofuels from biomass gasification are reviewed here and demonstrated to be an attractive option. Recent progress in gasification techniques and key generation pathways for biofuels production process design and integration and socio-environmental impacts of biofuel generation are discussed with the goal of investigating gasification-to-biofuels’ credentials as a sustainable and eco-friendly technology. The synthesis of important biofuels such as bio-methanol bio-ethanol and higher alcohols bio-dimethyl ether Fischer Tropsch fuels bio-methane bio-hydrogen and algae-based fuels is reviewed together with recent technologies catalysts and reactors. Significant thermodynamic studies for each biofuel are also examined. Syngas cleaning is demonstrated to be a critical issue for biofuel production and innovative pathways such as those employed by Choren Industrietechnik Germany and BioMCN the Netherlands are shown to allow efficient methanol generation. The conversion of syngas to FT transportation fuels such as gasoline and diesel over Co or Fe catalysts is reviewed and demonstrated to be a promising option for the future of biofuels. Bio-methane has emerged as a lucrative alternative for conventional transportation fuel with all the advantages of natural gas including a dense distribution trade and supply network. Routes to produce H2 are discussed though critical issues such as storage expensive production routes with low efficiencies remain. Algae-based fuels are in the research and development stage but are shown to have immense potential to become commercially important because of their capability to fix large amounts of CO2 to rapidly grow in many environments and versatile end uses. However suitable process configurations resulting in optimal plant designs are crucial so detailed process integration is a powerful tool to optimize current and develop new processes. LCA and ethical issues are also discussed in brief. It is clear that the use of food crops as opposed to food wastes represents an area fraught with challenges which must be resolved on a case by case basis.
Cross-regional Drivers for CCUS Deployment
Jul 2020
Publication
CO2 capture utilization and storage (CCUS) is recognized as a uniquely important option in global efforts to control anthropogenic greenhouse-gas (GHG) emissions. Despite significant progress globally in advancing the maturity of the various component technologies and their assembly into full-chain demonstrations a gap remains on the path to widespread deployment in many countries. In this paper we focus on the importance of business models adapted to the unique technical features and sociopolitical drivers in different regions as a necessary component of commercial scale-up and how lessons might be shared across borders. We identify three archetypes for CCUS development—resource recovery green growth and low-carbon grids—each with different near-term issues that if addressed will enhance the prospect of successful commercial deployment. These archetypes provide a framing mechanism that can help to translate experience in one region or context to other locations by clarifying the most important technical issues and policy requirements. Going forward the archetype framework also provides guidance on how different regions can converge on the most effective use of CCUS as part of global deep-decarbonization efforts over the long term.
Towards Net-zero Smart System: An Power Synergy Management Approach of Hydrogen and Battery Hybrid System with Hydrogen Safety Consideration
May 2022
Publication
The building system is one of key energy consumption sector in the market and low-carbon building will make a significant contribution for the worldwide carbon emission reduction. The multiple energy systems including renewable generations hydrogen energy and energy storage is the perspective answer to the net-zero building system. However the research gap lies in the synergy power management among the renewable flexible loads batteries and hydrogen energy systems and at the same time taking the unique characteristic of different energy sectors into account by power managing. This paper proposed the power management approach based on the game theory by which the different characteristics of the energy players are described via creating the competing relationship against net-zero emission objective so that to achieve the power synergy. Under the proposed power management method the hydrogen and battery hybrid system including the fuel cell electrolyzer and battery is designed and investigated as to unlock the power management regions and control constraints within the building system. Particularly for the hydrogen system within the hybrid system the safe and long-lifetime operation is considered respectively by high-efficiency and pressure constraints within the power management. Simulation results show that providing the same energy storage services for the building system the fuel cell with the proposed power management method sustains for 9.9 years much longer than that of equivalent consumption minimization (4.98) model predictive control (4.61) and rule-based method (7.69). Moreover the maximum tank temperature of the hydrogen tank is reduced by 3.4 K and 2.9 K compared with consumption minimization strategy and model predictive control. Also the real-time of the proposed power management is verified by a scaled-down experiment platform.
Recent Progress in Hydrogen Storage
Nov 2008
Publication
The ever-increasing demand for energy coupled with dwindling fossil fuel resources make the establishment of a clean and sustainable energy system a compelling need. Hydrogen-based energy systems offer potential solutions. Although in the long-term the ultimate technological challenge is large-scale hydrogen production from renewable sources the pressing issue is how to store hydrogen efficiently on board hydrogen fuel-cell vehicles.
Experimental Research on Low Calorific Value Gas Blended with Hydrogen Engine
Mar 2019
Publication
Experimental research on performance and emissions of engine fuelled with low calorific value gas blended with hydrogen was carried out and indicated thermal efficiency engine torque indicator diagram pressure rise rate and emissions with different hydrogen ratios were also analyzed. Experimental results show that with the increase of hydrogen fraction and CNG fraction in mixtures the indicated thermal efficiency increased. The engine power output is influenced by both low calorific value and hydrogen fractions. With the increase of hydrogen fraction in mixtures HC emissions decrease CO and NOx emissions increase. An engine operating on lean-burn low calorific value gas blended with hydrogen is favourable for getting lower emissions.
Thickness-Prediction Method Involving Tow Redistribution for the Dome of Composite Hydrogen Storage Vessels
Feb 2022
Publication
Traditional thickness-prediction methods underestimate the actual dome thickness at polar openings leading to the inaccurate prediction of the load-bearing capacity of composite hydrogen storage vessels. A method of thickness prediction for the dome section of composite hydrogen storage vessels was proposed which involved fiber slippage and tow redistribution. This method considered the blocking effect of the port on sliding fiber tows and introduced the thickness correlation to predict the dome thickness at polar openings. The arc length corresponding to the parallel circle radius was calculated and then the actual radius values corresponding to the bandwidth were obtained by the interpolation method. The predicted thickness values were compared with the actual measured thickness. The maximum relative error of the predicted thickness was 4.19% and the mean absolute percentage error was 2.04%. The results show that the present method had a higher prediction accuracy. Eventually this prediction method was used to perform progressive damage analysis on vessels. By comparing with the results of the cubic spline function method the analysis results of the present method approached the actual case. This showed that the present method improved the accuracy of the design.
A Model for Hydrogen Detonation Diffraction or Transmission to a Non-confined Layer
Sep 2021
Publication
One strategy for arresting propagating detonation waves in pipes is by imposing a sudden area enlargement which provides a rapid lateral divergence of the gases in the reaction zone and attenuates the leading shock. For sufficiently small tube diameter the detonation decays to a deflagration and the shock decays to negligible strengths. This is known as the critical tube diameter problem. In the present study we provide a closed form model to predict the detonation quenching for 2D channels. This problem also applies to the transmission of a detonation wave from a confined layer to a weakly-confined layer. Whitham’s geometric shock dynamics coupled with a shock evolution law based on shocks sustained by a constant source obtained by the shock change equations of Radulescu is shown to capture the lateral shock dynamics response to the failure wave originating at the expansion corner. A criterion for successful detonation transmission to open space is that the lateral strain rate provided by the failure wave not exceed the critical strain rate of steady curved detonations. Using the critical lateral strain rate obtained by He and Clavin a closed form solution is obtained for the critical channel opening permitting detonation transmission. The predicted critical channel width is found in excellent agreement with our recent experiments and simulations of diffracting H2/O2/Ar detonations. Model comparison with available data for H2/air detonation diffraction into open space at ambient conditions or for transmission into a weakly confined layer by air is also found in good agreement within a factor never exceeding 2 for the critical opening or layer dimension.
Hydrogen-Assisted Brittle Fracture Behavior of Low Alloy 30CrMo Steel Based on the Combination of Experimental and Numerical Analyses
Jul 2021
Publication
Compact-tension (CT) specimens made of low alloy 30CrMo steels were hydrogen-charged and then subjected to the fracture toughness test. The experimental results revealed that the higher crack propagation and the lower crack growth resistance (CTOD-R curve) are significantly noticeable with increasing hydrogen embrittlement (HE) indexes. Moreover the transition in the microstructural fracture mechanism from ductile (microvoid coalescence (MVC)) without hydrogen to a mixed quasi-cleavage (QC) fracture and QC + intergranular (IG) fracture with hydrogen was observed. The hydrogen-enhanced decohesion (HEDE) mechanism was characterized as the dominant HE mechanism. According to the experimental testing the coupled problem of stress field and hydrogen diffusion field with cohesive zone stress analysis was employed to simulate hydrogen-assisted brittle fracture behavior by using ABAQUS software. The trapezoidal traction-separation law (TSL) was adopted and the initial TSL parameters from the best fit to the load-displacement and J-integral experimental curves without hydrogen were calibrated for the critical separation of 0.0393 mm and the cohesive strength of 2100 MPa. The HEDE was implemented through hydrogen influence in the TSL and to estimate the initial hydrogen concentration based on matching numerical and experimental load-line displacement curves with hydrogen. The simulation results show that the general trend of the computational CTOD-R curves corresponding to initial hydrogen concentration is almost the same as that obtained from the experimental data but in full agreement the computational CTOD values being slightly higher. Comparative analysis of numerical and experimental results shows that the coupled model can provide design and prediction to calculate hydrogen-assisted fracture behavior prior to extensive laboratory testing provided that the material properties and properly calibrated TSL parameters are known.
Numerical Simulation of The Laminar Hydrogen Flame In The Presence of a Quenching Mesh
Sep 2009
Publication
Recent studies of J.H. Song et al. and S.Y. Yang et al. have been concentrated on mitigation measures against hydrogen risk. The authors have proposed installation of quenching meshes between compartments or around the essential equipment in order to contain hydrogen flames. Preliminary tests were conducted which demonstrated the possibility of flame extinction using metallic meshes of specific size.<br/>Considerable amount of numerical and theoretical work on flame quenching phenomenon has been performed in the second half of the last century and several techniques and models have been proposed to predict the quenching phenomenon of the laminar flame system. Most of these models appreciated the importance of heat loss to the surroundings as a primary cause of extinguishment in particular the heat transfer by conduction to the containing wall. The supporting simulations predict flame-quenching structure either between parallel plates (quenching distance) or inside a tube of a certain diameter (quenching diameter).<br/>In the present study the flame quenching is investigated assuming the laminar hydrogen flame propagating towards a quenching mesh using two-dimensional configuration and the earlier developed models. It is shown that due to a heat loss to a metallic grid the flame can be quenched numerically.
Hydrogen Inhibition Effect of Chitosan and Sodium Phosphate on ZK60 Waste Dust in a Wet Dust Removal System: A Feasible Way to Control Hydrogen Explosion
Dec 2021
Publication
Wet dust removal systems used to control dust in the polishing or grinding process of Mg alloy products are frequently associated with potential hydrogen explosion caused by magnesium-water reaction. For purpose of avoiding hydrogen explosion risks we try to use a combination of chitosan (CS) and sodium phosphate (SP) to inhibit the hydrogen evolution reaction between magnesium alloy waste dust and water. The hydrogen evolution curves and chemical kinetics modeling for ten different mixing ratios demonstrate that 0.4% wt CS + 0.1% wt SP yields the best inhibition efficiency with hydrogen generation rate of almost zero. SEM and EDS analyses indicate that this composite inhibitor can create a uniform smooth tight protective film over the surface of the alloy dust particles. FTIR and XRD analysis of the chemical composition of the surface film show that this protective film contains CS and SP chemically adsorbed on the surface of ZK60 but no detectable Mg(OH)2 suggesting that magnesium-water reaction was totally blocked. Our new method offers a thorough solution to hydrogen explosion by inhibiting the hydrogen generation of magnesium alloy waste dust in a wet dust removal system.
Effect of Relative Humidity on Mechanical Degradation of Medium Mn Steels
Mar 2020
Publication
Medium Mn steels have been considered as the next-generation materials for use in the automotive industry due to their excellent strength and ductility balance. To reduce the total weight and improve the safety of vehicles medium Mn steels look forward to a highly promising future. However hydrogen-induced delayed cracking is a concern for the use of high strength steels. This work is focused on the service characteristics of two kinds of medium Mn steels under different relative humidity conditions (40% 60% 80% and 100%). Under normal relative humidity (about 40%) at 25 °C the hydrogen concentration in steel is 0.4 ppm. When exposed to higher relative humidity the hydrogen concentration in steel increases slowly and reaches a stable value about 0.8 ppm. In slow strain rate tensile tests under different relative humidity conditions the tensile strength changed the hydrogen concentration increased and the elongation decreased as well thereby increasing the hydrogen embrittlement sensitivity. In other words the smaller the tensile rate applied the greater the hydrogen embrittlement sensitivity. In constant load tests under different relative humidity conditions the threshold value of the delayed cracking of M7B (‘M’ referring to Mn ‘7’ meaning the content of Mn ‘B’ denoting batch annealing) steel maintains a steady value of 0.82 σb (tensile strength). The threshold value of the delayed cracking of M10B significantly changed along with relative humidity. When relative humidity increased from 60% to 80% the threshold dropped sharply from 0.63 σb to 0.52 σb. We define 80% relative humidity as the ‘threshold humidity’ for M10B.
Hybrid Water Electrolysis: A New Sustainable Avenue for Energy-Saving Hydrogen Production
Oct 2021
Publication
Developing renewable energy-driven water splitting for sustainable hydrogen production plays a key role in achieving the carbon neutrality goal. Nevertheless the efficiency of traditional pure water electrolysis is severely hampered by the anodic oxygen evolution reaction (OER) due to its sluggish kinetics. In this context replacing OER with thermodynamically more favorable oxidation reactions to produce hydrogen via hybrid water electrolysis becomes an energy-saving hydrogen production scheme. Here the recent advances in hybrid water electrolysis are critically reviewed. First the fundamentals of electrochemical oxidation of typical organic molecules such as urea hydrazine and biomass are presented. Then the recent achievements in electrocatalysts for hybrid water electrolysis are introduced with an emphasis on outlining catalyst design strategies and the correlation between catalyst structure and performance. Finally future perspectives in this field for a sustainable hydrogen economy are proposed.
A Microstructure Informed and Mixed-mode Cohesive Zone Approach to Simulating Hydrogen Embrittlement
Mar 2022
Publication
Hydrogen induced failure under uniaxial tension is simulated in a duplex stainless steel considering microstructural feature of the material. There are three key ingredients in the modelling approach: image processing and finite element representation of the experimentally observed microstructure stress driven hydrogen diffusion and diffusion coupled cohesive zone modelling of fracture considering mixed failure mode. The microstructure used as basis for the modelling work is obtained from specimens cut in the transverse and longitudinal directions. It is found that the microstructure significantly influences hydrogen diffusion and fracture. The austenite phase is polygonal and randomly distributed in the transverse direction where a larger effective hydrogen diffusion coefficient and a lower hydrogen fracture resistance is found compared to the specimen in the longitudinal direction where the austenite phase is slender and laminated. This indicates that the proper design and control of the austenite phase help improve hydrogen resistance of duplex stainless steel. The strength of the interface in the shear direction is found to dominate the fracture mode and initiation site which reveals the importance of considering mixed failure mode and calibrating the hydrogen induced strength reduction in shear.
Risk Assessment on Life Safety and Financial Loss for Road Accident of Fuel Cell Vehicles
Sep 2017
Publication
Vehicular use of hydrogen is the first attempt to apply hydrogen energy in consumers’ environment in large scale and has raised safety concerns in both public authorities and private bodies such as fire services and insurance companies. This paper analyzes typical accident progressions of hydrogen fuel cell vehicles in a road collision accident. Major hydrogen consequences including impinging jet fires and catastrophic tank ruptures are evaluated separately in terms of accident duration and hazard distances. Results show that in a 70 MPa fuel cell car accident the hazards associated with hydrogen releases would normally last for no more than 1.5 min due to the empty of the tank. For the safety of general public a perimeter of 100 m is suggested in the accident scene if no hissing sound is heard. However the perimeter can be reduced to 10 m once the hissing sound of hydrogen release is heard. Furthermore risks of fatalities injuries and damages are all quantified in financial terms to assess the impacts of the accident. Results show that costs of fatalities and injuries contribute most to the overall financial loss indicating that the insurance premium of fatalities and injuries should be set higher than that of property loss.
Numerical Simulation of Combustion of Natural Gas Mixed with Hydrogen in Gas Boilers
Oct 2021
Publication
Hydrogen mixed natural gas for combustion can improve combustion characteristics and reduce carbon emission which has important engineering application value. A casing swirl burner model is adopted to numerically simulate and research the natural gas hydrogen mixing technology for combustion in gas boilers in this paper. Under the condition of conventional air atmosphere and constant air excess coefficient the six working conditions for hydrogen mixing proportion into natural gas are designed to explore the combustion characteristics and the laws of pollution emissions. The temperature distributions composition and emission of combustion flue gas under various working conditions are analyzed and compared. Further investigation is also conducted for the variation laws of NOx and soot generation. The results show that when the boiler heating power is constant hydrogen mixing will increase the combustion temperature accelerate the combustion rate reduce flue gas and CO2 emission increase the generation of water vapor and inhibit the generation of NOx and soot. Under the premise of meeting the fuel interchangeability it is concluded that the optimal hydrogen mixing volume fraction of gas boilers is 24.7%.
The Effect of Tube Internal Geometry on the Propensity to Spontaneous Ignition in Pressurized Hydrogen Release
Sep 2013
Publication
Spontaneous ignition of compressed hydrogen release through a length of tube with different internal geometries is numerically investigated using our previously developed model. Four types of internal geometries are considered: local contraction local enlargement abrupt contraction and abrupt enlargement. The presence of internal geometries was found to significantly increase the propensity to spontaneous ignition. Shock reflections from the surfaces of the internal geometries and the subsequent shock interactions further increase the temperature of the combustible mixture at the contact region. The presence of the internal geometry stimulates turbulence enhanced mixing between the shock-heated air and the escaping hydrogen resulting in the formation of more flammable mixture. It was also found that forward-facing vertical planes are more likely to cause spontaneous ignition by producing the highest heating to the flammable mixture than backward-facing vertical planes.
Hydrogen Generation from Methanol at Near-room Temperature
Sep 2017
Publication
As a promising hydrogen storage medium methanol has many advantages such as a high hydrogen content (12.5 wt%) and low-cost. However conventional methanol–water reforming methods usually require a high temperature (>200 °C). In this research we successfully designed an effective strategy to fully convert methanol to hydrogen for at least 1900 min (∼32 h) at near-room temperature. The strategy involves two main procedures which are CH3OH →HCOOH → H2 and CH3OH → NADH → H2. HCOOH and the reduced form of nicotinamide adenine dinucleotide (NADH) are simultaneously produced through the dehydrogenation of methanol by the cooperation of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). Subsequently HCOOH is converted to H2 by a new iridium polymer complex catalyst and an enzyme mimic is used to convert NADH to H2 and nicotinamide adenine dinucleotide (NAD+). NAD+ can then be reconverted to NADH by repeating the dehydrogenation of methanol. This strategy and the catalysts invented in this research can also be applied to hydrogen production from other small organic molecules (e.g. ethanol) or biomass (e.g. glucose) and thus will have a high impact on hydrogen storage and applications.
A Dynamic Performance Diagnostic Method Applied to Hydrogen Powered Aero Engines Operating under Transient Conditions
Apr 2022
Publication
At present aero engine fault diagnosis is mainly based on the steady-state condition at the cruise phase and the gas path parameters in the entire flight process are not effectively used. At the same time high quality steady-state monitoring measurements are not always available and as a result the accuracy of diagnosis might be affected. There is a recognized need for real-time performance diagnosis of aero engines operating under transient conditions which can improve their condition-based maintenance. Recent studies have demonstrated the capability of the sequential model-based diagnostic method to predict accurately and efficiently the degradation of industrial gas turbines under steady-state conditions. Nevertheless incorporating real-time data for fault detection of aero engines that operate in dynamic conditions is a more challenging task. The primary objective of this study is to investigate the performance of the sequential diagnostic method when it is applied to aero engines that operate under transient conditions while there is a variation in the bypass ratio and the heat soakage effects are taken into consideration. This study provides a novel approach for quantifying component degradation such as fouling and erosion by using an adapted version of the sequential diagnostic method. The research presented here confirms that the proposed method could be applied to aero engine fault diagnosis under both steady-state and dynamic conditions in real-time. In addition the economic impact of engine degradation on fuel cost and payload revenue is evaluated when the engine under investigation is using hydrogen. The proposed method demonstrated promising diagnostic results where the maximum prediction errors for steady state and transient conditions are less than 0.006% and 0.016% respectively. The comparison of the proposed method to a benchmark diagnostic method revealed a 15% improvement in accuracy which can have great benefit when considering that the cost attributed to degradation can reach up to $702585 for 6000 flight cycles of a hydrogen powered aircraft fleet. This study provides an opportunity to improve our understanding of aero engine fault diagnosis in order to improve engine reliability availability and efficiency by online health monitoring.
Optimal Operation of a Microgrid with Hydrogen Storage Based on Deep Reinforcement Learning
Jan 2022
Publication
Microgrid with hydrogen storage is an effective way to integrate renewable energy and reduce carbon emissions. This paper proposes an optimal operation method for a microgrid with hydrogen storage. The electrolyzer efficiency characteristic model is established based on the linear interpolation method. The optimal operation model of microgrid is incorporated with the electrolyzer efficiency characteristic model. The sequential decision-making problem of the optimal operation of microgrid is solved by a deep deterministic policy gradient algorithm. Simulation results show that the proposed method can reduce about 5% of the operation cost of the microgrid compared with traditional algorithms and has a certain generalization capability.
A Numerical Simulation on the Leakage Event of a High-Pressure Hydrogen Dispenser
Dec 2021
Publication
For the sake of the increasing demand of hydrogen fuel cell vehicles there are more concerns on the safety of hydrogen refueling stations. As one of the key pieces of equipment the hydrogen dispenser has drawn attention on this aspect since it involves massive manual operations and may be bothered by a high probability of failure. In this paper a numerical study is conducted to simulate the possible leakage events of the hydrogen dispenser based on a prototype in China whose working pressure is 70 MPa. The leakage accident is analyzed with respect to leakage sizes leak directions and the time to stop the leakage. It is found that due to the large mass flow rate under such high pressure the leak direction and the layout of the components inside the dispenser become insignificant and the ignitable clouds will form inside the dispenser in less than 1 s if there is a leakage of 1% size of the main tube. The ignitable clouds will form near the vent holes outside the dispenser which may dissipate quickly if the leakage is stopped. On the other hand the gas inside the dispenser will remain ignitable for a long time which asks for a design with no possible ignition source inside. The results can be useful in optimizing the design of the dispenser regarding the reaction time and sensitivity requirements of the leakage detector the size and amount of vent holes etc.
Improving Hydrogen Embrittlement Resistance of Hot-Stamped 1500 MPa Steel Parts That Have Undergone a Q&P Treatment by the Design of Retained Austenite and Martensite Matrix
Nov 2020
Publication
Hydrogen embrittlement is one of the largest obstacles against the commercialisation of ultra-high strength quenching and partitioning (Q&P) steels with ultimate tensile strength over 1500 MPa including the hot stamped steel parts that have undergone a Q&P treatment. In this work the influence of partitioning temperature on hydrogen embrittlement of ultra-high strength Q&P steels is studied by pre-charged tensile tests with both dog-bone and notched samples. It is found that hydrogen embrittlement resistance is enhanced by the higher partitioning temperature. Then the hydrogen embrittlement mechanism is analysed in terms of hydrogen retained austenite and martensite matrix. Thermal desorption analysis (TDA) shows that the hydrogen trapping properties are similar in the Q&P steels which cannot explain the enhancement of hydrogen embrittlement resistance. On the contrary it is found that the relatively low retained austenite stability after the higher temperature partitioning ensures more sufficient TRIP effect before hydrogen-induced fracture. Additionally dislocation recovery and solute carbon depletion at the higher partitioning temperature can reduce the flow stress of the martensite matrix improving its intrinsic toughness and reducing its hydrogen sensitivity both of which result in the higher hydrogen embrittlement resistance.
High CO2 Absorption Capacity of Metal-Based Ionic Liquids: A Molecular Dynamics Study
Apr 2020
Publication
The absorption of CO2 is of importance in carbon capture utilization and storage technology for greenhouse gas control. In the present work we clarified the mechanism of how metal-based ionic liquids (MBILs) Bmim[XCln]m (X is the metal atom) enhance the CO2 absorption capacity of ILs via performing molecular dynamics simulations. The sparse hydrogen bond interaction network constructed by CO2 and MBILs was identified through the radial distribution function and interaction energy of CO2-ion pairs which increase the absorption capacity of CO2 in MBILs. Then the dynamical properties including residence time and self-diffusion coefficient confirmed that MBILs could also promote the diffusion process of CO2 in ILs. That's to say the MBILs can enhance the CO2 absorption capacity and the diffusive ability simultaneously. Based on the analysis of structural energetic and dynamical properties the CO2 absorption capacity of MBILs increases in the order Cl− → [ZnCl4]2-→ [CuCl4]2-→ [CrCl4]- → [FeCl4]- revealing the fact that the short metal–Cl bond length and small anion volume could facilitate the performance of CO2 absorbing process. These findings show that the metal–Cl bond length and effective volume of the anion can be the effective factors to regulate the CO2 absorption process which can also shed light on the rational molecular design of MBILs for CO2 capture and other key chemical engineering processes such as IL-based gas sensors nano-electrical devices and so on.
Hydrolysis Hydrogen Production Mechanism of Mg10Ni10Ce Alloy Surface Modified by SnO2 Nanotubes in Different Aqueous Systems
May 2020
Publication
(Mg-10wt.%Ni)-10wt.%Ce (Mg10Ni10Ce) was ball-milled with SnO2 nanotubes and Mg10Ni10Ce-xSnO2 (x=0 5 10 and 15wt.%) composites have been prepared. The phase compositions microstructures morphologies and hydrolysis H2 generation performance in different aqueous systems (distilled water tap water and simulated seawater) have been investigated and the corresponding hydrolysis mechanism of Mg10Ni10Ce and Mg10Ni10Ce-SnO2 has been proposed. Adding a small amount of SnO2 nanotubes can significantly enhance the hydrolysis reaction of Mg10Ni10Ce especially the initial hydrolysis kinetics and the final H2 generation yield. Unfortunately the Mg10Ni10Ce-xSnO2 hardly react with distilled water at room temperature. The hydrolysis reaction rate of Mg10Ni10Ce-5SnO2 composite in tap water is still very slow with only 17.3% generation yield after 1 hour at 303 K. Fortunately in simulated seawater (3.5wt.% NaCl solution) the hydrolytic H2 generation behavior of the Mg10Ni10Ce-5SnO2 composite has been greatly improved which can release as high as 468.6 mL/g H2 with about 60.9% generation yield within 30 s at 303 K. The Cl- destroys the passivation layer on Mg-Ni-Ce alloy surface and the added SnO2 nanotubes accelerate the hydrolysis reaction rate and enhance the H2 generation yield. The Mg10Ni10Ce-5SnO2 composite can rapidly generate a large amount of H2 in simulate seawater in a short time which is expected to be applied on portable H2 generators in the future.
New Insights into the Electrochemical Behaviour of Porous Carbon Electrodes for Supercapacitors
Aug 2018
Publication
Activated carbons with different surface chemistry and porous textures were used to study the mechanism of electrochemical hydrogen and oxygen evolution in supercapacitor devices. Cellulose precursor materials were activated with different potassium hydroxide (KOH) ratios and the electrochemical behaviour was studied in 6 M KOH electrolyte. In situ Raman spectra were collected to obtain the structural changes of the activated carbons under severe electrochemical oxidation and reduction conditions and the obtained data were correlated to the cyclic voltammograms obtained at high anodic and cathodic potentials. Carbon-hydrogen bonds were detected for the materials activated at high KOH ratios which form reversibly under cathodic conditions. The influence of the specific surface area narrow microporosity and functional groups in the carbon electrodes on their chemical stability and hydrogen capture mechanism in supercapacitor applications has been revealed.
Hydrogen Storage Behavior of Nanocrystalline and Amorphous Mg–Ni–Cu–La Alloys
Sep 2020
Publication
Alloying and structural modification are two effective ways to enhance the hydrogen storage kinetics and decrease the thermal stability of Mg and Mg-based alloys. In order to enhance the characteristics of Mg2Ni-type alloys Cu and La were added to an Mg2Ni-type alloy and the sample alloys (Mg24Ni10Cu2)100−xLax (x = 0 5 10 15 20) were prepared by melt spinning. The influences of La content and spinning rate on the gaseous and electrochemical hydrogen storage properties of the sample alloys were explored in detail. The structural identification carried out by XRD and TEM indicates that the main phase of the alloys is Mg2Ni and the addition of La results in the formation of the secondary phases LaMg3 and La2Mg17. The as-spun alloys have amorphous and nanocrystalline structures and the addition of La promotes glass formation. The electrochemical properties examined by an automatic galvanostatic system show that the samples possess a good activation capability and achieve their maximal discharge capacities within three cycles. The discharge potential characteristics were vastly ameliorated by melt spinning and La addition. The discharge capacities of the samples achieve their maximal values as the La content changes and the discharge capacities always increase with increasing spinning rate. The addition of La leads to a decline in hydrogen absorption capacity but it can effectively enhance the rate of hydrogen absorption. The addition of La and melt spinning significantly increase the hydrogen desorption rate due to the reduced activation energy.
Risk Analysis on Mobile Hydrogen Refueling Stations in the World Expo Shanghai
Sep 2013
Publication
During the World Expo Shanghai there were one hundred fuel-cell sight-seeing cars in operation at the Expo Site. The sight-seeing cars were not allowed to drive out of the Expo Site and the stationary hydrogen refuelling station was not permitted to build at the Expo Site for the sake of safety. A flexible solution to refuel the cars was the application of mobile hydrogen refuelling stations. To better understand the hazards and risks associated with the mobile hydrogen refueling stations a risk analysis was preformed to improve the safety of the operations. The risks to the station personnel and to the public were discussed separately. Results show that the stationary risks of the mobile stations to the personnel and refueling customers are lower than the risk acceptance criteria over an order of magnitude so occupational risks and risks to customers are completely acceptable. The third party risks can be acceptable as long as the appropriate mitigation measures are implemented especially well designed parking area and operation time. Leak from boosters is the main risk contributor to the stationary risks because of its highest failure rates according to the generic data and its worst harm effects based on the consequence evaluations. As for the road risks of the mobile stations they can be acceptable as long as the appropriate mitigation measures are implemented especially well-designed moving path and transportation time.
Electrocatalysts Based on Metal@carbon Core@shell Nanocomposites: An Overview
Aug 2018
Publication
Developing low-cost high-performance catalysts is of fundamental significance for electrochemical energy conversion and storage. In recent years metal@carbon core@shell nanocomposites have emerged as a unique class of functional nanomaterials that show apparent electrocatalytic activity towards a range of reactions such as hydrogen evolution reaction oxygen evolution reaction oxygen reduction reaction and CO2 reduction reaction that are important in water splitting fuel cells and metal-air batteries. The activity is primarily attributed to interfacial charge transfer from the metal core to the carbon shell that manipulate the electronic interactions between the catalyst surface and reaction intermediates and varies with the structures and morphologies of the metal core (elemental composition core size etc.) and carbon shell (doping layer thickness etc.). Further manipulation can be achieved by the incorporation of a third structural component. A perspective is also included highlighting the current gap between theoretical modeling and experimental results and technical challenges for future research.
Improvement of Low Temperature Activity and Stability of Ni Catalysts with Addition of Pt for Hydrogen Production Via Steam Reforming of Ethylene Glycol
Nov 2018
Publication
Hydrogen production by steam reforming of ethylene glycol (EG) at 300 °C was investigated over SiO2 and CeO2 supported Pt–Ni bimetallic catalysts prepared by incipient wetness impregnation methods. It was observed that impregnation sequence of Pt and Ni can affect the performance of catalysts apparently. Catalyst with Pt first and then Ni addition showed higher EG conversion and H2 yield owing to the Ni enrichment on the surface and the proper interaction between Pt and Ni. It was observed that although SiO2 supported catalysts exhibited better activity and H2 selectivity CeO2 supported ones had better stability. This is attributed to the less coke formation on CeO2. Increasing Pt/Ni ratio enhanced the reaction activity and Pt3–Ni7 catalysts with 3 wt% Pt and 7 wt% Ni showed the highest activity and stability. Ni surficial enrichment facilitated the C—C bond rupture and water gas shift reactions; and Pt addition inhibited methanation reaction. Electron transfer and hydrogen spillover from Pt to Ni suppressed carbon deposition. These combined effects lead to the excellent performance of Pt3–Ni7 supported catalysts.
Catalysis of Oxides in Hydrogen Generation by the Reaction of Al with Water
Sep 2013
Publication
Hydrogen generation by the reaction of pure Al powder in water with the addition of Al(OH)3 γ- Al2O3 α-Al2O3 or TiO2 at mild temperatures was investigated. It was found that the reaction of Al with water is promoted and the reaction induction time decreases greatly by the above hydroxide and oxides. X-ray diffraction analyses revealed that the hydroxide and oxide phases have no any change during the Al-water reaction indicating that they are just as catalysts to assist the reaction of Al with water. A possible mechanism was proposed which shows that hydroxide and oxides could dissociate water molecules and promote the hydration of the passive oxide film on Al particle surfaces.
Explosion Venting of Rich Hydrogen-air Mixtures in a Cylindrical Vessel with Two Symmetrical Vents
Oct 2015
Publication
The safety issues related to explosion venting of hydrogen-air mixtures are significant and deserve more detailed investigation. Vented hydrogen-air explosion has been studied extensively in vessels with a single vent. However little attention has been paid to the cases with more than one vent. In this paper experiments about explosion venting of rich hydrogen-air mixtures were conducted in a cylindrical vessel with two symmetrical vents to investigate the effect of vent area and distribution on pressure build up and flame behaviours. Venting accelerates the flame front towards the vent but has nearly no effect on the opposite side. The maximum internal overpressure decreases and the maximum external flame length increases with the increase of vent area. Two pressure peaks can be identified outside of vessel which correspond to the external explosion and the burnt gas jet respectively. Compared with single vent two vents with same total vent area leads to nearly unchanged maximum internal and external overpressure but much smaller external flame length.
Reversible Ammonia-based and Liquid Organic Hydrogen Carriers for High-density Hydrogen Storage: Recent Progress
Feb 2019
Publication
Liquid hydrogen carriers are considered to be attractive hydrogen storage options because of their ease of integration into existing chemical transportation infrastructures when compared with liquid or compressed hydrogen. The development of such carriers forms part of the work of the International Energy Agency Task 32: Hydrogen-Based Energy Storage. Here we report the state-of-the-art for ammonia-based and liquid organic hydrogen carriers with a particular focus on the challenge of ensuring easily regenerable high-density hydrogen storage.
Novel Fuzzy Control Energy Management Strategy for Fuel Cell Hybrid Electric Vehicles Considering State of Health
Oct 2021
Publication
Due to the low efficiency and high pollution of conventional internal combustion engine vehicles the fuel cell hybrid electric vehicles are expected to play a key role in the future of clean energy transportation attributed to the long driving range short hydrogen refueling time and environmental advantages. The development of energy management strategies has an important impact on the economy and durability but most strategies ignore the aging of fuel cells and the corresponding impact on hydrogen consumption. In this paper a rule-based fuzzy control strategy is proposed based on the constructed data-driven online estimation model of fuel cell health. Then a genetic algorithm is used to optimize this fuzzy controller where the objective function is designed to consider both the economy and durability by combining the hydrogen consumption cost and the degradation cost characterized by the fuel cell health status. Considering that the rule-based strategy is more sensitive to operating conditions this paper uses an artificial neural network for predictive control. The results are compared with those obtained from the genetic algorithm optimized fuzzy controller and are found to be very similar where the prediction accuracy is assessed using MAPE RMSE and 10-fold cross-validation. Experiments show that the developed strategy has a good generalization capability for variable driving cycles.
Reversible Solid-oxide Cell Stack Based Power-to-x-to-power Systems: Comparison of Thermodynamic Performance
Jun 2020
Publication
The increasing penetration of variable renewable energies poses new challenges for grid management. The economic feasibility of grid-balancing plants may be limited by low annual operating hours if they work either only for power generation or only for power storage. This issue might be addressed by a dual-function power plant with power-to-x capability which can produce electricity or store excess renewable electricity into chemicals at different periods. Such a plant can be uniquely enabled by a solid-oxide cell stack which can switch between fuel cell and electrolysis with the same stack. This paper investigates the optimal conceptual design of this type of plant represented by power-to-x-to-power process chains with x being hydrogen syngas methane methanol and ammonia concerning the efficiency (on a lower heating value) and power densities. The results show that an increase in current density leads to an increased oxygen flow rate and a decreased reactant utilization at the stack level for its thermal management and an increased power density and a decreased efficiency at the system level. The power-generation efficiency is ranked as methane (65.9%) methanol (60.2%) ammonia (58.2%) hydrogen (58.3%) syngas (53.3%) at 0.4 A/cm2 due to the benefit of heat-to-chemical-energy conversion by chemical reformulating and the deterioration of electrochemical performance by the dilution of hydrogen. The power-storage efficiency is ranked as syngas (80%) hydrogen (74%) methane (72%) methanol (68%) ammonia (66%) at 0.7 A/cm2 mainly due to the benefit of co-electrolysis and the chemical energy loss occurring in the chemical synthesis reactions. The lost chemical energy improves plant-wise heat integration and compensates for its adverse effect on power-storage efficiency. Combining these efficiency numbers of the two modes results in a rank of round-trip efficiency: methane (47.5%)>syngas (43.3%) ≈ hydrogen (42.6%)>methanol (40.7%)>ammonia (38.6%). The pool of plant designs obtained lays the basis for the optimal deployment of this balancing technology for specific applications.
Empowering Hydrogen Storage Properties of Haeckelite Monolayers via Metal Atom Functionalization
Mar 2021
Publication
Using hydrogen as an energy carrier requires new technological solutions for its onboard storage. The exploration of two-dimensional (2D) materials for hydrogen storage technologies has been motivated by their open structures which facilitates fast hydrogen kinetics. Herein the hydrogen storage properties of lightweight metal functionalized r57 haeckelite sheets are studied using density functional theory (DFT) calculations. H2 molecules are adsorbed on pristine r57 via physisorption. The hydrogen storage capacity of r57 is improved by decorating it with alkali and alkaline-earth metals. In addition the in-plane substitution of r57 carbons with boron atoms (B@r57) both prevents the clustering of metals on the surface of 2D material and increases the hydrogen storage capacity by improving the adsorption thermodynamics of hydrogen molecules. Among the studied compounds B@r57-Li4 with its 10.0 wt% H2 content and 0.16 eV/H2 hydrogen binding energy is a promising candidate for hydrogen storage applications. A further investigation as based on the calculated electron localization functions atomic charges and electronic density of states confirm the electrostatic nature of interactions between the H2 molecules and the protruding metal atoms on 2D haeckelite sheets. All in all this work contributes to a better understanding of pure carbon and B-doped haeckelites for hydrogen storage.
Mechanical Properties and Hydrogen Embrittlement of Laser-Surface Melted AISI 430 Ferritic Stainless Steel
Feb 2020
Publication
Hydrogen was doped in austenitic stainless steel (ASS) 316L tensile samples produced by the laser-powder bed fusion (L-PBF) technique. For this aim an electrochemical method was conducted under a high current density of 100 mA/cm2 for three days to examine its sustainability under extreme hydrogen environments at ambient temperatures. The chemical composition of the starting powders contained a high amount of Ni approximately 12.9 wt.% as a strong austenite stabilizer. The tensile tests disclosed that hydrogen charging caused a minor reduction in the elongation to failure (approximately 3.5% on average) and ultimate tensile strength (UTS; approximately 2.1% on average) of the samples using a low strain rate of 1.2 × 10−4 s−1. It was also found that an increase in the strain rate from 1.2 × 10−4 s−1 to 4.8 × 10−4 s−1 led to a reduction of approximately 3.6% on average for the elongation to failure and 1.7% on average for UTS in the pre-charged samples. No trace of martensite was detected in the X-ray diffraction (XRD) analysis of the fractured samples thanks to the high Ni content which caused a minor reduction in UTS × uniform elongation (UE) (GPa%) after the H charging. Considerable surface tearing was observed for the pre-charged sample after the tensile deformation. Additionally some cracks were observed to be independent of the melt pool boundaries indicating that such boundaries cannot necessarily act as a suitable area for the crack propagation.
Towards the Rational Design of Stable Electrocatalysts for Green Hydrogen Production
Feb 2022
Publication
Now it is time to set up reliable water electrolysis stacks with active and robust electro‐ catalysts to produce green hydrogen. Compared with catalytic kinetics much less attention has been paid to catalyst stability and the weak understanding of the catalyst deactivation mechanism restricts the design of robust electrocatalysts. Herein we discuss the issues of catalysts’ stability evaluation and characterization and the degradation mechanism. The systematic understanding of the degradation mechanism would help us to formulate principles for the design of stable catalysts. Particularly we found that the dissolution rate for different 3d transition metals differed greatly: Fe dissolves 114 and 84 times faster than Co and Ni. Based on this trend we designed Fe@Ni and FeNi@Ni core‐shell structures to achieve excellent stability in a 1 A cm−2 current density as well as good catalytic activity at the same time
Particle Size and Crystal Phase Effects in Fischer-Tropsch Catalysts
Aug 2017
Publication
Fischer-Tropsch synthesis (FTS) is an increasingly important approach for producing liquid fuels and chemicals via syngas—that is synthesis gas a mixture of carbon monoxide and hydrogen—generated from coal natural gas or biomass. In FTS dispersed transition metal nanoparticles are used to catalyze the reactions underlying the formation of carbon-carbon bonds. Catalytic activity and selectivity are strongly correlated with the electronic and geometric structure of the nanoparticles which depend on the particle size morphology and crystallographic phase of the nanoparticles. In this article we review recent works dealing with the aspects of bulk and surface sensitivity of the FTS reaction. Understanding the different catalytic behavior in more detail as a function of these parameters may guide the design of more active selective and stable FTS catalysts.
Recent Development of Biomass Gasification for H2 Rich Gas Production
Mar 2022
Publication
Biomass gasification for hydrogen (H2) production provides outstanding advantages in terms of renewable energy resources carbon neutral high efficiency and environmental benefits. However the factors influencing H2 production from biomass gasification are complex which makes determining the optimal operating conditions challenging. Biomass gasification also poses challenges owing to the high associated tar content and low gas yield which need to be overcome. This review summarizes the influence of the gasification parameters on H2 production. Catalytic gasification technology and some of the latest catalysts such as composites and special structure catalysts are also summarized herein based on the requirements of high-purity H2 production. Moreover novel technologies such as staged gasification chemical looping gasification and adsorption-enhanced reforming for producing H2 rich gas are introduced. Finally the challenges and prospects associated with biomass gasification for H2 production are presented.
Low Temperature Autoignition of Diesel Fuel Under Dual Operation with Hydrogen and Hydrogen-carriers
Mar 2022
Publication
While electrification of light duty vehicles is becoming a real solution to abate local pollutant as well as greenhouse gases emission heavy duty applications (such as long distance freight and maritime transport) will keep requiring fuel-based propulsion systems. In these sectors dominated by compression ignition engines research on alternative biofuels and new combustion modes is still highly necessary. Dual-fuel combustion appears as a very promising concept to replace conventional diesel fuel by sustainable ones. Among the latter hydrogen-derived fuels (the so-called electrofuels or e-fuels) are maybe the most interesting. This work addresses the effect of partial substitution of diesel fuel by hydrogen and hydrogen-carriers (ammonia and methane) on the autoignition process under low temperature conditions. Tests were carried out in a constant volume combustion chamber at different temperatures (535 600 and 650 ◦C) and pressures (11 16 and 21 bar). While the cool flames timing and intensity was only slightly affected by the low reactivity fuel energy content the main ignition was delayed this effect being much more noticeable for ammonia followed by hydrogen and finally methane. Kinetic simulations showed a clear competition for active radicals between both fuels (diesel and low reactivity fuel). The combustion duration also increased with the hydrogen or hydrogen-carrier content which greatly points to the need of modifications in the injection strategy of compression ignition engines operating under dual mode. A correlation was proposed for estimating the autoignition delay time for dual-fuel lean combustion at low temperature.
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
High Proton-Conductive and Temperature-Tolerant PVC-P4VP Membranes towards Medium-Temperature Water Electrolysis
Mar 2022
Publication
Water electrolysis (WE) is a highly promising approach to producing clean hydrogen. Medium-temperature WE (100–350 ◦C) can improve the energy efficiency and utilize the low-grade water vapor. Therefore a high-temperature proton-conductive membrane is desirable to realize the medium-temperature WE. Here we present a polyvinyl chloride (PVC)-poly(4vinylpyridine) (P4VP) hybrid membrane by a simple cross-linking of PVC and P4VP. The pyridine groups of P4VP promote the loading rate of phosphoric acid which delivers the proton conductivity of the PVC-P4VP membrane. The optimized PVC-P4VP membrane with a 1:2 content ratio offers the maximum proton conductivity of 4.3 × 10−2 S cm−1 at 180 ◦C and a reliable conductivity stability in 200 h at 160 ◦C. The PVC-P4VP membrane electrode is covered by an IrO2 anode and a Pt/C cathode delivers not only the high water electrolytic reactivity at 100–180 ◦C but also the stable WE stability at 180 ◦C.
Performance of Three Typical Domestic Gas Stoves Operated with Methane-hydrogen Mixture
Dec 2022
Publication
Hydrogen blending into natural gas has attracted significant attention in domestic applications. The paper studied the effects of natural gas mixed with hydrogen at 0% (vol) 5% 10% 15% 20% and 25% on the performance of typical round-port gas stove (TRPGS) swirling strip-port gas stove (SSPGS) and radiant porous media gas stove (RPMGS). The experimental results show that flame length shortens with the increase of hydrogen proportion and the combustion remains stable when the hydrogen proportion is equal to or less than 25%. With increasing hydrogen proportion the measured heat inputs of the three types of domestic gas stoves decrease gradually and the average thermal efficiency of TRPGS and SSPGS increase by 0.82% and 1.18% respectively. In addition the average efficiency of the RPMGS first increases by 1.35% under a hydrogen proportion of 15% and then decreases by 1.36% under a hydrogen proportion of 25%. In terms of flue gas emission CO emission reduces significantly with increasing hydrogen proportion while NOX emissions remain almost unchanged.
The Influence of Grain Boundary and Hydrogen on the Indetation of Bi-crystal Nickel
Sep 2021
Publication
Three different types of symmetrical tilt grain boundaries Ȉ3 Ȉ11 and Ȉ27 were constructed to study the dislocation behavior under the indentation on bi-crystal nickel. After hydrogen charging the number of hydrogen atoms in the Ȉ3 sample is the smallest and gradually increases in Ȉ11 and Ȉ27 samples. The force-displacement curve of indentation shows that the deformation resistance of the Ȉ3 sample is significantly higher than that of Ȉ11 and Ȉ27 samples. With the presence of grain boundaries the deformation resistance of Ȉ11 and Ȉ27 samples is significantly improved while the deformation resistance of the Ȉ3 VDPSOH is weakened. The indentation depth during the formation of dislocations in single crystals is significantly greater than that of bi-crystals. Grain boundaries slow down the dislocation propagation speed. Compared with the bi-crystals without hydrogen the presence of hydrogen reduces the deformation resistance and accelerates the dislocation propagation.
What Is the Policy Effect of Coupling the Green Hydrogen Market, National Carbon Trading Market and Electricity Market?
Oct 2022
Publication
Green hydrogen has become the key to social low-carbon transformation and is fully linked to zero carbon emissions. The carbon emissions trading market is a policy tool used to control carbon emissions using a market-oriented mechanism. Building a modular carbon trading center for the hydrogen energy industry would greatly promote the meeting of climate targets. Based on this a “green hydrogen market—national carbon trading market–electricity market” coupling mechanism is designed. Then the “green hydrogen market—national carbon trading market–electricity market” mechanism is modeled and simulated using system dynamics. The results are as follows: First coupling between the green hydrogen market carbon trading market and electricity market can be realized through green hydrogen certification and carbon quota trading. It is found that the coupling model is feasible through simulation. Second simulation of the basic scenario finds that multiple-market coupling can stimulate an increase in carbon price the control of thermal power generation and an increase in green hydrogen production. Finally the proportion of the green hydrogen certification the elimination mechanism of outdated units and the quota auction mechanism will help to form a carbon pricing mechanism. This study enriches the green hydrogen trading model and establishes a multiple-market linkage mechanism.
National Policies, Recent Research Hotspots, and Application of Sustainable Energy: Case of China, USA and European Countries
Aug 2022
Publication
This study tracks the variety of nations dealing with the issue of energy transition. Through process tracing and a cross-national case study a comparison of energy policies research hotspots and technical aspects of three sustainable energy systems (solar cells recharge batteries and hydrogen production) was conducted. We provide an overview of the climate-change political process and identify three broad patterns in energy-related politics in the United States China and Europe (energy neo-liberalism authoritarian environmentalism and integrated-multinational negotiation). The core processes and optimization strategies to improve the efficiency of sustainable energy usage are analyzed. This study provides both empirical and theoretical contributions to research on energy transitions.
Progress in Electrical Energy Storage System: A Critical Review
Jan 2009
Publication
Electrical energy storage technologies for stationary applications are reviewed. Particular attention is paid to pumped hydroelectric storage compressed air energy storage battery flow battery fuel cell solar fuel superconducting magnetic energy storage flywheel capacitor/supercapacitor and thermal energy storage. Comparison is made among these technologies in terms of technical characteristics applications and deployment status.
Investigating the Impact of Economic Uncertainty on Optimal Sizing of Grid-Independent Hybrid Renewable Energy Systems
Aug 2021
Publication
One of the many barriers to decarbonization and decentralization of the energy sector in developing countries is the economic uncertainty. As such this study scrutinizes economics of three grid-independent hybrid renewable-based systems proposed to co-generate electricity and heat for a small-scale load. Accordingly the under-study systems are simulated and optimized with the aid of HOMER Pro software. Here a 20-year average value of discount and inflation rates is deemed a benchmark case. The techno-economic-environmental and reliability results suggest a standalone solar/wind/electrolyzer/hydrogen-based fuel cell integrated with a hydrogen-based boiler system is the best alternative. Moreover to ascertain the impact of economic uncertainty on optimal unit sizing of the nominated model the fluctuations of the nominal discount rate and inflation respectively constitute within the range of 15–20% and 10–26%. The findings of economic uncertainty analysis imply that total net present cost (TNPC) fluctuates around the benchmark value symmetrically between $478704 and $814905. Levelized energy cost varies from an amount 69% less than the benchmark value up to two-fold of that. Furthermore photovoltaic (PV) optimal size starts from a value 23% less than the benchmark case and rises up to 55% more. The corresponding figures for wind turbine (WT) are respectively 21% and 29%. Eventually several practical policies are introduced to cope with economic uncertainty.
Reduction Kinetics of Hematite Powder in Hydrogen Atmosphere at Moderate Temperatures
Sep 2018
Publication
Hydrogen has received much attention in the development of direct reduction of iron ores because hydrogen metallurgy is one of the effective methods to reduce CO2 emission in the iron and steel industry. In this study the kinetic mechanism of reduction of hematite particles was studied in a hydrogen atmosphere. The phases and morphological transformation of hematite during the reduction were characterized using X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. It was found that porous magnetite was formed and the particles were degraded during the reduction. Finally sintering of the reduced iron and wüstite retarded the reductive progress. The average activation energy was extracted to be 86.1 kJ/mol and 79.1 kJ/mol according to Flynn-Wall-Ozawa (FWO) and Starink methods respectively. The reaction fraction dependent values of activation energy were suggested to be the result of multi-stage reactions during the reduction process. Furthermore the variation of activation energy value was smoothed after heat treatment of hematite particles.
Hydrogen Sensing Properties of UV Enhanced Pd-SnO2 Nano-Spherical Composites at Low Temperature
Sep 2021
Publication
Metal oxide semiconductor (MOS) is promising in developing hydrogen detectors. However typical MOS materials usually work between 200-500°C which not only restricts their application in flammable and explosive gases detection but also weakens sensor stability and causes high power consumption. This paper studies the sensing properties of UV enhanced Pd-SnO2 nano-spherical composites at 80-360 ℃. In the experiment Pd of different molar ratios (0.5 2.5 5.0 10.0) was doped into uniform spherical SnO2 nanoparticles by a hydrothermal synthesis method. A xenon lamp with a filter was used as the ultraviolet excitation light source to examine the response of the spherical Pd- SnO2 nanocomposite to 50-1000 ppm H2 gas. The influence of different intensities of ultraviolet light on the gas-sensing properties of composite materials compared with dark condition was analyzed. The experiments show that the conductivity of the composites can be greatly stabilized and the thermal excitation temperature can be reduced to 180 ℃ under the effect of UV enhancement. A rapid response (4.4/ 17.4 s) to 200 ppm of H2 at 330 °C can be achieved by the Pd-SnO2 nanocomposites with UV assistance. The mechanism may be attributed to light motivated electron-hole pairs due to built-in electric fields under UV light illumination which can be captured by target gases and lead to UV controlled gas sensing performance. Catalytic active sites of hydrogen are provided on the surface of the mixed material by Pd. The results in this study can be helpful in reducing the response temperature of MOS materials and improving the performance of hydrogen detectors."
Improving Ecological Efficiency of Gas Turbine Power System by Combusting Hydrogen and Hydrogen-Natural Gas Mixtures
Apr 2023
Publication
Currently the issue of creating decarbonized energy systems in various spheres of life is acute. Therefore for gas turbine power systems including hybrid power plants with fuel cells it is relevant to transfer the existing engines to pure hydrogen or mixtures of hydrogen with natural gas. However significant problems arise associated with the possibility of the appearance of flashback zones and acoustic instability of combustion an increase in the temperature of the walls of the flame tubes and an increase in the emission of nitrogen oxides in some cases. This work is devoted to improving the efficiency of gas turbine power systems by combusting pure hydrogen and mixtures of natural gas with hydrogen. The organization of working processes in the premixed combustion chamber and the combustion chamber with a sequential injection of ecological and energy steam for the “Aquarius” type power plant is considered. The conducted studies of the basic aerodynamic and energy parameters of a gas turbine combustor working on hydrogen-containing gases are based on solving the equations of conservation and transfer in a multicomponent reacting system. A four-stage chemical scheme for the burning of a mixture of natural gas and hydrogen was used which allows for the rational parameters of environmentally friendly fuel burning devices to be calculated. The premixed combustion chamber can only be recommended for operations on mixtures of natural gas with hydrogen with a hydrogen content not exceeding 20% (by volume). An increase in the content of hydrogen leads to the appearance of flashback zones and fuel combustion inside the channels of the swirlers. For the combustion chamber of the combined-cycle power plant “Vodoley” when operating on pure hydrogen the formation of flame flashback zones does not occur.
Economic Operation Strategy of Integrated Hydrogen Energy System Considering the Uncertainty of PV Power Output
Jan 2023
Publication
To address the negative influence caused by power randomness of distributed PV output on energy system’s economic operation in this work an economic operation strategy considering the uncertainty features of PV output has been designed and applied on an integrated hydrogen energy system. First the thermal system operation model and the thermoelectric output control model are precisely built for the integrated hydrogen energy system and the hydrogen-based fuel cell respectively. Then referring to the PV output prediction data the uncertainty of light intensity variation is analyzed to correct the PV output prediction curve. Finally a cost–benefit model for the optimal economic operation of the integrated hydrogen energy system including PV hydrogen fuel cell and cogeneration unit is designed with an objective function of achieving an optimal economic operation of the multi-energy coupling devices. The simulation tests validate that considering the influence of PV output uncertainty on hydrogen fuel cell output can make the system operation more reasonable which ensures the economic and reliable operation of hydrogen energy systems.
Hydrogen Fuel Cell Vehicle Development in China: An Industry Chain Perspective
Jun 2020
Publication
Hydrogen fuel cell vehicle (FCV) technology has significant implications on energy security and environmental protection. In the past decade China has made great progress in the hydrogen and FCV industry considering both the government’s policy issuances and enterprises’ production. However there are still some technological and cost challenges obstructing the commercialization of FCVs. Herein the status of China’s hydrogen FCV industry is analyzed comprehensively from three perspectives: policy support market application and technology readiness level. The unique characteristics and key issues in each part of the industry chain are emphasized. Furthermore the energy environmental and economic performances of FCV in the life-cycle perspective are reviewed and summarized based on pre-existing literature and reports. The life-cycle analysis of hydrogen and FCV indicates that the energy and environmental impacts of FCVs are highly related to the sources of hydrogen. With the combination of industry status and technology performances it is highlighted that technology advancements in hydrogen production and fuel cells and the optimization of the manufacturing processes for fuel cell systems are equally essential in the development of hydrogen FCVs.
Development Concept of Integrated Energy Network and Hydrogen Energy Industry Based on Hydrogen Production Using Surplus Hydropower
Apr 2020
Publication
The development of hydropower industry is progressing rapidly in China and the installed capacity and power generation are increasing year by year. However due to factors such as transmission channels and power grid peaking capacity hydropower consumption in some areas is facing greater pressure. As an excellent medium for energy interconnection hydrogen energy can play an important role in promoting hydropower consumption. This paper introduces the current status and trends of hydrogen energy development in major developed countries and China and analyzes the current status of China’s hydropower abandoned water. Based on the production of hydrogen using surplus hydropower in the Dadu River Basin in Sichuan an integrated energy network research plan including hydropower electrolytic hydrogen production storage and transportation hydrogen refueling and hydrogen-powered vehicles is proposed. At the same time the development concept of hydrogen energy industry including hydrogen energy source economy hydrogen energy industry ecosphere and hydrogen energy sky road in western Sichuan is also proposed.
Hydrogen Permeation Behavior of QP1180 High Strength Steel in Simulated Coastal Atmosphere
Mar 2022
Publication
The hydrogen permeation behavior of QP1180 high strength steel for automobile was studied in simulate coastal atmosphere environment by using Devanathan-Stachurski dual electrolytic cell the cyclic corrosion test (CCT) thermal desorption spectrometry (TDS) and electrochemical measurement methods. The current density of hydrogen permeation generally increases with reducing the relative humidity from 95% to 50% and periodically changes in the CCT process. These mainly result from the evolution of corrosion and rust layer on the specimen surface with the atmospheric humidity and intermittent salt spraying. The contents of diffusible hydrogen and non-diffusible hydrogen in the steel enlarge slightly in the CCT process. The plastic deformation about 11.3% results in much higher diffusible hydrogen content in steel but noticeably reduces the hydrogen permeation current and almost has no influence on the non-diffusible hydrogen content. The combination of double electrolytic cell and standard cyclic corrosion test can effectively characterize the hydrogen permeation of high strength steel in atmospheric service environments.
Multi-Time Scale Optimal Scheduling Model of Wind and Hydrogen Integrated Energy System Based on Carbon Trading
Jan 2023
Publication
In the context of carbon trading energy conservation and emissions reduction are the development directions of integrated energy systems. In order to meet the development requirements of energy conservation and emissions reduction in the power grid considering the different responses of the system in different time periods a wind-hydrogen integrated multi-time scale energy scheduling model was established to optimize the energy-consumption scheduling problem of the system. As the scheduling model is a multiobjective nonlinear problem the artificial fish swarm algorithm–shuffled frog leaping algorithm (AFS-SFLA) was used to solve the scheduling model to achieve system optimization. In the experimental test process the Griewank benchmark function and the Rosenbrock function were selected to test the performance of the proposed AFS-SFL algorithm. In the Griewank environment compared to the SFLA algorithm the AFS-SFL algorithm was able to find a feasible solution at an early stage and tended to converge after 110 iterations. The optimal solution was −4.83. In the test of total electric power deviation results at different time scales the maximum deviation of early dispatching was 14.58 MW and the minimum deviation was 0.56 MW. The overall deviation of real-time scheduling was the minimum and the minimum deviation was 0 and the maximum deviation was 1.89 WM. The integrated energy system adopted real-time scale dispatching with good system stability and low-energy consumption. Power system dispatching optimization belongs to the objective optimization problem. The artificial fish swarm algorithm and frog algorithm were innovatively combined to solve the dispatching model which improved the accuracy of power grid dispatching. The research content provides an effective reference for the efficient use of clean and renewable energy.
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.
Synergetic Effect of Multiple Phases on Hydrogen Desorption Kinetics and Cycle Durability in Ball Milled MgH2–PrF3–Al–Ni Composite
Jan 2021
Publication
A new MgH2–PrF3–Al–Ni composite was prepared by ball milling under hydrogen atmosphere. After initial dehydrogenation and rehydrogenation Pr3Al11 MgF2 PrH3 and Mg2NiH4 nanoparticles formed accompanying the main phase MgH2. The hydrogen absorption-desorption properties were measured by using a Sieverts-type apparatus. The results showed that the MgH2–PrF3–Al–Ni composite improved cycle stability and enhanced hydrogen desorption kinetics. The improvement of hydrogen absorption-desorption properties is ascribed to the synergetic effect of the in situ formed Pr3Al11 MgF2 PrH3 and Mg2NiH4 nanoparticles. This work provides an important inspiration for the improvement of hydrogen storage properties in Mg-based materials.
Preparation, Performance and Challenges of Catalyst Layer for Proton Exchange Membrane Fuel Cell
Nov 2021
Publication
In this paper the composition function and structure of the catalyst layer (CL) of a proton exchange membrane fuel cell (PEMFC) are summarized. The hydrogen reduction reaction (HOR) and oxygen reduction reaction (ORR) processes and their mechanisms and the main interfaces of CL (PEM|CL and CL|MPL) are described briefly. The process of mass transfer (hydrogen oxygen and water) proton and electron transfer in MEA are described in detail including their influencing factors. The failure mechanism of CL (Pt particles CL crack CL flooding etc.) and the degradation mechanism of the main components in CL are studied. On the basis of the existing problems a structure optimization strategy for a high‐performance CL is proposed. The commonly used preparation processes of CL are introduced. Based on the classical drying theory the drying process of a wet CL is explained. Finally the research direction and future challenges of CL are pointed out hoping to provide a new perspective for the design and selection of CL materials and preparation equipment.
Recent Developments in High-Performance Nafion Membranes for Hydrogen Fuel Cells Applications
Aug 2021
Publication
As a promising alternative to petroleum fossil energy polymer electrolyte membrane fuel cell has drawn considerable attention due to its low pollution emission high energy density portability and long operation times. Proton exchange membrane (PEM) like Nafion plays an essential role as the core of fuel cell. A good PEM must have satisfactory performance such as high proton conductivity excellent mechanical strength electrochemical stability and suitable for making membrane electrode assemblies (MEA). However performance degradation and high permeability remain the main shortcomings of Nafion. Therefore the development of a new PEM with better performance in some special conditions is greatly desired. In this review we aim to summarize the latest achievements in improving the Nafion performance that works well under elevated temperature or methanol-fueled systems. The methods described in this article can be divided into some categories utilizing hydrophilic inorganic material metal-organic frameworks nanocomposites and ionic liquids. In addition the mechanism of proton conduction in Nafion membranes is discussed. These composite membranes exhibit some desirable characteristics but the development is still at an early stage. In the future revolutionary approaches are needed to accelerate the application of fuel cells and promote the renewal of energy structure.
Materials for Hydrogen-based Energy Storage - Past, Recent Progress and Future Outlook
Dec 2019
Publication
Michael Hirscher,
Volodymyr A. Yartys,
Marcello Baricco,
José Bellosta von Colbe,
Didier Blanchard,
Robert C. Bowman Jr.,
Darren P. Broom,
Craig Buckley,
Fei Chang,
Ping Chen,
Young Whan Cho,
Jean-Claude Crivello,
Fermin Cuevas,
William I. F. David,
Petra E. de Jongh,
Roman V. Denys,
Martin Dornheim,
Michael Felderhoff,
Yaroslav Filinchuk,
George E. Froudakis,
David M. Grant,
Evan MacA. Gray,
Bjørn Christian Hauback,
Teng He,
Terry D. Humphries,
Torben R. Jensen,
Sangryun Kim,
Yoshitsugu Kojima,
Michel Latroche,
Hai-wen Li,
Mykhaylo V. Lototskyy,
Joshua W. Makepeace,
Kasper T. Møller,
Lubna Naheed,
Peter Ngene,
Dag Noreus,
Magnus Moe Nygård,
Shin-ichi Orimo,
Mark Paskevicius,
Luca Pasquini,
Dorthe B. Ravnsbæk,
M. Veronica Sofianos,
Terrence J. Udovic,
Tejs Vegge,
Gavin Walker,
Colin Webb,
Claudia Weidenthaler and
Claudia Zlotea
Globally the accelerating use of renewable energy sources enabled by increased efficiencies and reduced costs and driven by the need to mitigate the effects of climate change has significantly increased research in the areas of renewable energy production storage distribution and end-use. Central to this discussion is the use of hydrogen as a clean efficient energy vector for energy storage. This review by experts of Task 32 “Hydrogen-based Energy Storage” of the International Energy Agency Hydrogen TCP reports on the development over the last 6 years of hydrogen storage materials methods and techniques including electrochemical and thermal storage systems. An overview is given on the background to the various methods the current state of development and the future prospects. The following areas are covered; porous materials liquid hydrogen carriers complex hydrides intermetallic hydrides electro-chemical storage of energy thermal energy storage hydrogen energy systems and an outlook is presented for future prospects and research on hydrogen-based energy storage
Research on Economic and Operating Characteristics of Hydrogen Fuel Cell Cars Based on Real Vehicle Tests
Nov 2021
Publication
With the increase of the requirement for the economy of vehicles and the strengthening of the concept of environmental protection the development of future vehicles will develop in the direction of high efficiency and cleanliness and the current power system of vehicles based on traditional fossil fuels will gradually transition to hybrid power. As an essential technological direction for new energy vehicles the development of fuel cell passenger vehicles is of great significance in reducing transportation carbon emissions stabilizing energy supply and maintaining the sustainable development of the automotive industry. To study the fuel economy of a passenger car with the proton exchange membrane fuel cell (PEMFC) during the operating phase two typical PEMFC passenger cars test vehicles A and B were compared and analyzed. The hydrogen consumption and hydrogen emission under two operating conditions namely the different steady-state power and the Chinese Vehicle Driving Conditions-Passenger Car cycle were tested. The test results show the actual hydrogen consumption rates of vehicle A and vehicle B are 9.77 g/kM and 8.28 g/kM respectively. The average hydrogen emission rates for vehicle A and vehicle B are 1.56 g/(kW·h) and 5.40 g/(kW·h) respectively. By comparing the hydrogen purge valve opening time ratio the differences between test vehicles A and B in control strategy hydrogen consumption and emission rate are analyzed. This study will provide reference data for China to study the economics of the operational phase of PEMFC vehicles.
Hydrogen Fuel and Electricity Generation from a New Hybrid Energy System Based on Wind and Solar Energies and Alkaline Fuel Cell
Apr 2021
Publication
Excessive consumption of fossil fuels has led to depletion of reserves and environmental crises. Therefore turning to clean energy sources is essential. However these energy sources are intermittent in nature and have problems meeting long-term energy demand. The option suggested by the researchers is to use hybrid energy systems. The aim of this paper is provide the conceptual configuration of a novel energy cycle based on clean energy resources. The novel energy cycle is composed of a wind turbine solar photovoltaic field (PV) an alkaline fuel cell (AFC) a Stirling engine and an electrolyzer. Solar PV and wind turbine convert solar light energy and wind kinetic energy into electricity respectively. Then the generated electricity is fed to water electrolyzer. The electrolyzer decomposes water into oxygen and hydrogen gases by receiving electrical power. So the fuel cell inlets are provided. Next the AFC converts the chemical energy contained in hydrogen into electricity during electrochemical reactions with by-product (heat). The purpose of the introduced cycle is to generate electricity and hydrogen fuel. The relationships defined for the components of the proposed cycle are novel and is examined for the first time. Results showed that the output of the introduced cycle is 10.5 kW of electricity and its electrical efficiency is 56.9%. In addition the electrolyzer uses 9.9 kW of electricity to produce 221.3 grams per hour of hydrogen fuel. The share of the Stirling engine in the output power of the cycle is 9.85% (1033.7 W) which is obtained from the dissipated heat of the fuel cell. In addition wind turbine is capable of generating an average of 4.1 kW of electricity. However 238.6 kW of cycle exergy is destroyed. Two different scenarios are presented for solar field design.
Financing Efficiency Evaluation and Influencing Factors of Hydrogen Energy Listed Enterprises in China
Jan 2022
Publication
Existing studies of financing efficiency concentrate on capital structure and a single external environment or internal management characteristic. Few of the studies include the internal and external financing environments at the same time for hydrogen energy industry financing efficiency. This paper used the data envelopment analysis (DEA) model and the Malmquist index to measure the financing efficiency of 70 hydrogen energy listed enterprises in China from 2014 to 2020 from both static and dynamic perspectives. Then a tobit model was constructed to explore the influence of external environment and internal factors on the financing efficiency. The contributions of this paper are studying the internal and external financing environments and integrating financing cost efficiency and capital allocation efficiency into the financing efficiency of hydrogen energy enterprises. The results show that firstly the financing efficiency of China’s hydrogen energy listed enterprises showed an upward trend during the years 2014–2020. Secondly China’s hydrogen energy enterprises mainly gather in the eastern coastal areas and their financing efficiency is more than that in western areas. Thirdly the regional economic development level enterprise scale financing structure capital utilization efficiency and profitability have significant effects on the financing efficiency. These results can promote the achievement of “carbon neutrality” in China.
Controlled Biosynthesis of ZnCdS Quantum Dots with Visible-Light-Driven Photocatalytic Hydrogen Production Activity
May 2021
Publication
The development of visible-light-responsive photocatalysts with high efficiency stability and eco-friendly nature is beneficial to the large-scale application of solar hydrogen production. In this work the production of biosynthetic ternary ZnCdS photocatalysts (Eg = 2.35–2.72 eV) by sulfate-reducing bacteria (SRB) under mild conditions was carried out for the first time. The huge amount of biogenic S2− and inherent extracellular proteins (EPs) secreted by SRB are important components of rapid extracellular biosynthesis. The ternary ZnCdS QDs at different molar ratios of Zn2+and Cd2+ from 15:1 to 1:1 were monodisperse spheres with good crystallinity and average crystallite size of 6.12 nm independent of the molar ratio of Cd2+ to Zn2+. All the ZnCdS QDs had remarkable photocatalytic activity and stability for hydrogen evolution under visible light without noble metal cocatalysts. Especially ZnCdS QDs at Zn/Cd = 3:1 showed the highest H2 production activity of 3.752 mmol·h−1·g−1. This excellent performance was due to the high absorption of visible light the high specific surface area and the lower recombination rate between photoexcited electrons and holes. The adhered inherent EPs on the ZnCdS QDs slowed down the photocorrosion and improved the stability in photocatalytic hydrogen evolution. This study provides a new direction for solar hydrogen production.
Review of the Hydrogen Permeability of the Liner Material of Type IV On-Board Hydrogen Storage Tank
Aug 2021
Publication
The hydrogen storage tank is a key parameter of the hydrogen storage system in hydrogen fuel cell vehicles (HFCVs) as its safety determines the commercialization of HFCVs. Compared with other types the type IV hydrogen storage tank which consists of a polymer liner has the advantages of low cost lightweight and low storage energy consumption but meanwhile higher hydrogen permeability. A detailed review of the existing research on hydrogen permeability of the liner material of type IV hydrogen storage tanks can improve the understanding of the hydrogen permeation mechanism and provide references for following-up researchers and research on the safety of HFCVs. The process of hydrogen permeation and test methods are firstly discussed in detail. This paper then analyzes the factors that affect the process of hydrogen permeation and the barrier mechanism of the liner material and summarizes the prediction models of gas permeation. In addition to the above analysis and comments future research on the permeability of the liner material of the type IV hydrogen storage tank is prospected.
Integration Design and Operation Strategy of Multi-Energy Hybrid System Including Renewable Energies, Batteries and Hydrogen
Oct 2020
Publication
In some areas the problem of wind and solar power curtailment is prominent. Hydrogen energy has the advantage of high storage density and a long storage time. Multi-energy hybrid systems including renewable energies batteries and hydrogen are designed to solve this problem. In order to reduce the power loss of the converter an AC-DC hybrid bus is proposed. A multi-energy experiment platform is established including a wind turbine photovoltaic panels a battery an electrolyzer a hydrogen storage tank a fuel cell and a load. The working characteristics of each subsystem are tested and analyzed. The multi-energy operation strategy is based on state monitoring and designed to enhance hydrogen utilization energy efficiency and reliability of the system. The hydrogen production is guaranteed preferentially and the load is reliably supplied. The system states are monitored such as the state of charge (SOC) and the hydrogen storage level. The rated and ramp powers of the battery and fuel cell and the pressure limit of the hydrogen storage tank are set as safety constraints. Eight different operation scenarios comprehensively evaluate the system’s performance and via physical experiments the proposed operation strategy of the multi-energy system is verified as effective and stable.
Improved Hydrogen Separation Performance of Asymmetric Oxygen Transport Membranes by Grooving in the Porous Support Layer
Nov 2020
Publication
Hydrogen separation through oxygen transport membranes (OTMs) has attracted much attention. Asymmetric membranes with thin dense layers provide low bulk diffusion resistances and high overall hydrogen separation performances. However the resistance in the porous support layer (PSL) limits the overall separation performance significantly. Engineering the structure of the PSL is an appropriate way to enable fast gas transport and increase the separation performance. There is no relevant research on studying the influence of the PSL on hydrogen separation performance so far. Herein we prepared Ce0.85Sm0.15O1.925 – Sm0.6Sr0.4Cr0.3Fe0.7O3-δ (SDC-SSCF) asymmetric membranes with straight grooves in PSL by tape-casting and laser grooving. A ~30% improvement in the hydrogen separation rate was achieved by grooving in the PSLs. It indicates that the grooves may reduce the concentration polarization resistance in PSL for the hydrogen separation process. This work provides a straight evidence on optimizing the structures of PSL for improving the hydrogen separation performance of the membrane reactors.
Technologies and Policies to Decarbonize Global Industry: Review and Assessment of Mitigation Drivers Through 2070
Mar 2020
Publication
Jeffrey Rissman,
Chris Bataille,
Eric Masanet,
Nate Aden,
William R. Morrow III,
Nan Zhou,
Neal Elliott,
Rebecca Dell,
Niko Heeren,
Brigitta Huckestein,
Joe Cresko,
Sabbie A. Miller,
Joyashree Roy,
Paul Fennell,
Betty Cremmins,
Thomas Koch Blank,
David Hone,
Ellen D. Williams,
Stephane de la Rue du Can,
Bill Sisson,
Mike Williams,
John Katzenberger,
Dallas Burtraw,
Girish Sethi,
He Ping,
David Danielson,
Hongyou Lu,
Tom Lorber,
Jens Dinkel and
Jonas Helseth
Fully decarbonizing global industry is essential to achieving climate stabilization and reaching net zero greenhouse gas emissions by 2050–2070 is necessary to limit global warming to 2 °C. This paper assembles and evaluates technical and policy interventions both on the supply side and on the demand side. It identifies measures that employed together can achieve net zero industrial emissions in the required timeframe. Key supply-side technologies include energy efficiency (especially at the system level) carbon capture electrification and zero-carbon hydrogen as a heat source and chemical feedstock. There are also promising technologies specific to each of the three top-emitting industries: cement iron & steel and chemicals & plastics. These include cement admixtures and alternative chemistries several technological routes for zero-carbon steelmaking and novel chemical catalysts and separation technologies. Crucial demand-side approaches include material-efficient design reductions in material waste substituting low-carbon for high-carbon materials and circular economy interventions (such as improving product longevity reusability ease of refurbishment and recyclability). Strategic well-designed policy can accelerate innovation and provide incentives for technology deployment. High-value policies include carbon pricing with border adjustments or other price signals; robust government support for research development and deployment; and energy efficiency or emissions standards. These core policies should be supported by labeling and government procurement of low-carbon products data collection and disclosure requirements and recycling incentives. In implementing these policies care must be taken to ensure a just transition for displaced workers and affected communities. Similarly decarbonization must complement the human and economic development of low- and middle-income countries.
Review on Blended Hydrogen-fuel Internal Combustion Engines: A Case Study for China
Apr 2022
Publication
Under the dual pressure of energy conservation and environmental protection the internal combustion engine industry is facing huge challenges and it is imperative to find new clean energy. Hydrogen energy is expected to replace traditional fossil fuels as an excellent fuel for internal combustion engines because of its clean continuous regeneration and good combustion performance. This review article focuses on the research and development of blended hydrogen-fuel internal combustion engines in China since the beginning of this century. The main achievements gained by Chinese researchers in performing research on the effects of the addition of hydrogen into engines which predominantly include many types of hydrogen-blended engines such as gasoline diesel natural gas and alcohol engines rotary engines are discussed and analyzed in these areas of the engine’s performance and the combustion and emission characteristics etc. The merits and demerits of blended hydrogen-fuel internal combustion engines could be concluded and summarized after discussion. Finally the development trend and direction of exploration on hydrogen-fuel internal combustion engines could also be forecasted for relevant researchers.
Optimal Planning of Hybrid Electric-hydrogen Energy Storage Systems via Multi-objective Particle Swarm Optimization
Jan 2023
Publication
In recent years hydrogen is rapidly developing because it is environmentally friendly and sustainable. In this case hydrogen energy storage systems (HESSs) can be widely used in the distribution network. The application of hybrid electric-hydrogen energy storage systems can solve the adverse effects caused by renewable energy access to the distribution network. In order to ensure the rationality and effectiveness of energy storage systems (ESSs) configuration economic indicators of battery energy storage systems (BESSs) and hydrogen energy storage systems power loss and voltage fluctuation are chosen as the fitness function in this paper. Meanwhile multi-objective particle swarm optimization (MOPSO) is used to solve Pareto non-dominated set of energy storage systems’ optimal configuration scheme in which the technique for order preference by similarity to ideal solution (TOPSIS) based on information entropy weight (IEW) is used select the optimal solution in Pareto non-dominated solution set. Based on the extended IEEE-33 system and IEEE-69 system the rationality of energy storage systems configuration scheme under 20% and 35% renewable energy penetration rate is analyzed. The simulation results show that the power loss can be reduced by 7.9%–22.8% and the voltage fluctuation can be reduced by 40.0%–71% when the renewable energy penetration rate is 20% and 35% respectively in IEEE-33 and 69 nodes systems. Therefore it can be concluded that the locations and capacities of energy storage systems obtained by multi-objective particle swarm optimization can improve the distribution network stability and economy after accessing renewable generation.
Platinum Single-atom Catalyst Coupled with Transition Metal/Metal Oxide Heterostructure for Accelerating Alkaline Hydrogen Evolution Reaction
Jun 2021
Publication
Single-atom catalysts provide an effective approach to reduce the amount of precious metals meanwhile maintain their catalytic activity. However the sluggish activity of the catalysts for alkaline water dissociation has hampered advances in highly efficient hydrogen production. Herein we develop a single-atom platinum immobilized NiO/Ni heterostructure (PtSA-NiO/Ni) as an alkaline hydrogen evolution catalyst. It is found that Pt single atom coupled with NiO/Ni heterostructure enables the tunable binding abilities of hydroxyl ions (OH*) and hydrogen (H*) which efficiently tailors the water dissociation energy and promotes the H* conversion for accelerating alkaline hydrogen evolution reaction. A further enhancement is achieved by constructing PtSA-NiO/Ni nanosheets on Ag nanowires to form a hierarchical three-dimensional morphology. Consequently the fabricated PtSA-NiO/Ni catalyst displays high alkaline hydrogen evolution performances with a quite high mass activity of 20.6 A mg−1 for Pt at the overpotential of 100 mV significantly outperforming the reported catalysts.
Evaluation of a New Combined Energy System Performance to Produce Electricity and Hydrogen with Energy Storage Option
Mar 2021
Publication
According to new findings the use of alternative energy sources such as wind energy is needed to supply the energy demand of future generations. On the other hand combined renewable energy systems can be more efficient than their stand-alone systems. Therefore clean energy-based hybrid energy systems can be a suitable solution for fossil fuels. However for their widespread commercialization more detailed and powerful studies are needed. On the other hand in order to attain sustainable development for the use of renewable energy sources due to their nature energy storage is required. The motivation of this study is introduce and examine a new energy system performance for the production of electricity and hydrogen fuel as well as energy storage. So this paper presents the energy and exergy operation of a hybrid wind turbine water electrolyzer and Pumped-hydro-compressed air system. The electricity produced by the wind turbine is used to produce hydrogen fuel in electrolyzer and the excess energy is stored using the storage system. It was found that the electrolyzer needed 512.6 W of electricity to generate 5 mol/h of hydrogen fuel which was supplied by a 10 kW-wind turbine. In such a context the efficiency of the process was 74.93%. Furthermore on average the isothermal process requires 17.53% less storage capacity than the isentropic process. The effect of key parameters such as rate of hydrogen fuel production operating pressures wind speed and components efficiency on the process operation is also examined.
A Quantitative Study of Policy-driven Changes and Forecasts in the Development of the Hydrogen Transportation Industry
Feb 2022
Publication
Through data mining and analysis of the word frequency and occurrence position of industrial policy keywords the main policy parameters affecting industrial development are determined and the functional relationship between industrial policy and industrial development is obtained through multi-parameter non-linear regression: Yit−1 (y1 y2 y3 y4 y5) = β1it X1 + β2it ln X2 + β3it ln X3 + β4it X1it ∗ ln X3 + εit . The time series function of the industrial development index: Y (t) = 0.174 ∗ e (0.256∗t) is established and the industrial development under the influence of next year’s policy is predicted. It is concluded from the mathematical expression of the statistical model that there is a certain coupling effect between different policies and that industrial development is influenced by the joint effect on the parent and sub-industries. This ultimately proves that there is a clear correlation between policy and industry development.
Irreversible Hydrogen Embrittlement Study of B1500HS High Strength Boron Steel
Dec 2020
Publication
The reversible/irreversible recovery of mechanical properties and the microstructure characteristics of a typical hot-stamped steel B1500HS have been studied under different conditions of hydrogen permeation. Initially all tested specimens were permeated by hydrogen atoms through an electrochemical hydrogen charging scheme. Then the comparisons between different currents and charging time were performed. The influence of different storage time was compared as well. Additionally the effect of the plastic strain introduced by pre-stretching was also investigated. The experimental results showed that the negative impact of hydrogen embrittlement was altered from reversible to irreversible as the magnitude of the charging current increased. The hydrogen blistering and the hydrogen charging-induced cracks were both observed and inspected in the tested samples regarding the irreversible situation. Moreover the adverse influence of hydrogen embrittlement was enhanced by plastic pre-straining or extending the charging period. At the micro-level hydrogen charging-induced cracks generally were generated at defect locations such as the prior austenite grain boundaries and lath martensite interfaces. Particularly crack direction occurred perpendicular to the orientation of lath martensite and transgranular fracture occurred at the prior austenite grains.
CFD Model Based Ann Prediction of Flammable Vapor Colour Formed by Liquid Hydrogen Spill
Sep 2021
Publication
Unintended releases can occur during the production storage transportation and filling of liquid hydrogen which may cause devastating consequences. In the present work liquid hydrogen leak is modeled in ANSYS Fluent with the numerical model validated using the liquid hydrogen spill test data. A three-layer artificial neural network (ANN) model is built in which the wind speed ground temperature leakage time and leakage rate are taken as the inputs the horizontal diffusion distance and vertical diffusion distance of combustible gas as the outputs of the ANN. The representative sample data derived from the detailed calculation results of the numerical model are selected via the orthogonal experiment method to train and verify the back propagation (BP) neural network. Comparing the calculation results of the formula fitting with the sample data the results show that the established ANN model can quickly and accurately predict the horizontal and vertical diffusion distance of flammable vapor cloud relatively. The influences of four parameters on the horizontal hazard distance as well as vertical hazard height are predicted and analyzed in the case of continuous overflow of liquid hydrogen using the ANN model.
Spherically Expanding Flame Simulations in Cantera Using a Lagrangian Formulation
Sep 2021
Publication
A Lagrangian-based one-dimensional approach has been developed using Cantera to study the dynamics of spherically expanding flames. The detailed reaction model USC-Mech II has been employed to examine flame propagating in hydrogen-air mixtures. In the first part our approach has been validated against laminar flame speed and Markstein number data from the literature. It was shown that the laminar flame speed was predicted within 5% on average but that discrepancies were observed for the Markstein number especially for rich mixtures. In the second part a detailed analysis of the thermo-chemical dynamics along the path of Lagrangian particles propagating in stretched flames was performed. For mixtures with negative Markstein lengths it was found that at high stretch rates the mixture entering the reaction-dominated period is less lean with respect to the initial mixture than at low stretch rate. This induces a faster rate of chemical heat release and of active radical production which results in a higher flame propagation speed. Opposite effects were observed for mixtures with positive Markstein lengths for which slower flame propagation was observed at high stretch rates compared to low stretch rates."
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.
Hydrogen Fuel Cell Power System—Development Perspectives for Hybrid Topologies
Mar 2023
Publication
In recent years the problem of environmental pollution especially the emission of greenhouse gases has attracted people’s attention to energy infrastructure. At present the fuel consumed by transportation mainly comes from fossil energy and the strong traffic demand has a great impact on the environment and climate. Fuel cell electric vehicles (FCEVs) use hydrogen energy as a clean alternative to fossil fuels taking into account the dual needs of transportation and environmental protection. However due to the low power density and high manufacturing cost of hydrogen fuel cells their combination with other power supplies is necessary to form a hybrid power system that maximizes the utilization of hydrogen energy and prolongs the service life of hydrogen fuel cells. Therefore the hybrid power system control mode has become a key technology and a current research hotspot. This paper first briefly introduces hydrogen fuel cells then summarizes the existing hybrid power circuit topology categorizes the existing technical solutions and finally looks forward to the future for different scenarios of hydrogen fuel cell hybrid power systems. This paper provides reference and guidance for the future development of renewable hydrogen energy and hydrogen fuel cell hybrid electric vehicles.
Utilization of Food Waste for Hydrogen-based Power Generation: Evidence from Four Cities in Ghana
Mar 2023
Publication
Hydrogen gas will be an essential energy carrier for global energy systems in the future. However non-renewable sources account for 96% of the production. Food wastes have high hydrogen generation potential which can positively influence global production and reduce greenhouse gas (GHG) emissions. The study evaluates the potential of food waste hydrogen-based power generation through biogas steam reforming and its environmental and economic impact in major Ghanaian cities. The results highlight that the annual hydrogen generation in Kumasi had the highest share of 40.73 kt followed by Accra with 31.62 kt while the least potential was in Tamale (3.41 kt). About 2073.38 kt was generated in all the major cities. Hydrogen output is predicted to increase from 54.61 kt in 2007 to 119.80 kt by 2030. Kumasi produced 977.54 kt of hydrogen throughout the 24-year period followed by Accra with 759.76 kt Secondi-Takoradi with 255.23 kt and Tamale with 81.85 kt. According to the current study Kumasi had the largest percentage contribution of hydrogen (47.15%) followed by Accra (36.60%) Secondi-Takoradi (12.31%) and Tamale (3.95%). The annual power generation potential in Kumasi and Accra was 73.24 GWh and 56.85 GWh. Kumasi and Accra could offset 8.19% and 6.36% of Ghana's electricity consumption. The total electricity potential of 3728.35 GWh could displace 17.37% of Ghana's power consumption. This electricity generated had a fossil diesel displacement capacity of 1125.90 ML and could reduce GHG emissions by 3060.20 kt CO2 eq. Based on the findings the total GHG savings could offset 8.13% of Ghana's carbon emissions. The cost of power generation from hydrogen is $ 0.074/kWh with an annual positive net present value of $ 658.80 million and a benefit-to-cost ratio of 3.43. The study lays the foundation and opens policy windows for sustainable hydrogen power generation in Ghana and other African countries.
Resource Assessment for Green Hydrogen Production in Kazakhstan
Jan 2023
Publication
Kazakhstan has long been regarded as a major exporter of fossil fuel energy. As the global energy sector is undergoing an unprecedented transition to low-carbon solutions new emerging energy technologies such as hydrogen production require more different resource bases than present energy technologies. Kazakhstan needs to consider whether it has enough resources to stay competitive in energy markets undergoing an energy transition. Green hydrogen can be made from water electrolysis powered by low-carbon electricity sources such as wind turbines and solar panels. We provided the first resource assessment for green hydrogen production in Kazakhstan by focusing on three essential resources: water renewable electricity and critical raw materials. Our estimations showed that with the current plan of Kazakhstan to keep its water budget constant in the future producing 2–10 Mt green hydrogen would require reducing the water use of industry in Kazakhstan by 0.6–3% or 0.036–0.18 km3/year. This could be implemented by increasing the share of renewables in electricity generation and phasing out some of the water- and carbon-intensive industries. Renewable electricity potential in South and West Kazakhstan is sufficient to run electrolyzers up to 5700 and 1600 h/year for wind turbines and solar panels respectively. In our base case scenario 5 Mt green hydrogen production would require 50 GW solar and 67 GW wind capacity considering Kazakhstan's wind and solar capacity factors. This could convert into 28652 tons of nickel 15832 tons of titanium and many other critical raw materials. Although our estimations for critical raw materials were based on limited geological data Kazakhstan has access to the most critical raw materials to support original equipment manufacturers of low-carbon technologies in Kazakhstan and other countries. As new geologic exploration kicks off in Kazakhstan it is expected that more deposits of critical raw materials will be discovered to respond to their potential future needs for green hydrogen production.
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.
Solid Air Hydrogen Liquefaction, the Missing Link of the Hydrogen Economy
Mar 2023
Publication
The most challenging aspect of developing a green hydrogen economy is long-distance oceanic transportation. Hydrogen liquefaction is a transportation alternative. However the cost and energy consumption for liquefaction is currently prohibitively high creating a major barrier to hydrogen supply chains. This paper proposes using solid nitrogen or oxygen as a medium for recycling cold energy across the hydrogen liquefaction supply chain. When a liquid hydrogen (LH2) carrier reaches its destination the regasification process of the hydrogen produces solid nitrogen or oxygen. The solid nitrogen or oxygen is then transported in the LH2 carrier back to the hydrogen liquefaction facility and used to reduce the energy consumption cooling gaseous hydrogen. As a result the energy required to liquefy hydrogen can be reduced by 25.4% using N2 and 27.3% using O2. Solid air hydrogen liquefaction (SAHL) can be the missing link for implementing a global hydrogen economy.
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.
Experimental Investigation of Stress Corrosion on Supercritical CO2 Transportation Pipelines Against Leakage for CCUS Applications
Nov 2022
Publication
Carbon Capture Utilization and Storage (CCUS) is one of the key technologies that will determine how humans address global climate change. For captured CO2 in order to avoid the complications associated with two-phase flow most carbon steel pipelines are operated in the supercritical state on a large scale. A pipeline has clear Stress Corrosion Cracking (SCC) sensitivity under the action of stress and corrosion medium which will generally cause serious consequences. In this study X70 steel was selected to simulate an environment in the process of supercritical CO2 transportation by using high-temperature high-pressure Slow Strain Rate Tensile (SSRT) tests and high-temperature high-pressure electrochemical test devices with different O2 and SO2 contents. Studies have shown that 200 ppm SO2 shows a clear SCC sensitivity tendency which is obvious when the SO2 content reaches 600 ppm. The SCC sensitivity increases with the increase of SO2 concentration but the increase amplitude decreases. With the help of advanced microscopic characterization techniques such as scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) through the analysis of fracture and side morphology the stress corrosion mechanism of a supercritical CO2 pipeline containing SO2 and O2 impurities was obtained by hydrogen embrittlement fracture characteristics. With the increase of SO2 content the content of Fe element decreases and the corrosion increases demonstrating that SO2 plays a leading role in electrochemical corrosion. This study further strengthens the theoretical basis of stress corrosion of supercritical CO2 pipelines plays an important role in preventing leakage of supercritical CO2 pipelines and will provide guidance for the industrial application of CCUS.
Progress in Energy Storage Technologies and Methods for Renewable Energy Systems Application
May 2023
Publication
This paper provides a comprehensive review of the research progress current state-ofthe-art and future research directions of energy storage systems. With the widespread adoption of renewable energy sources such as wind and solar power the discourse around energy storage is primarily focused on three main aspects: battery storage technology electricity-to-gas technology for increasing renewable energy consumption and optimal configuration technology. The paper employs a visualization tool (CiteSpace) to analyze the existing works of literature and conducts an in-depth examination of the energy storage research hotspots in areas such as electrochemical energy storage hydrogen storage and optimal system configuration. It presents a detailed overview of common energy storage models and configuration methods. Based on the reviewed articles the future development of energy storage will be more oriented toward the study of power characteristics and frequency characteristics with more focus on the stability effects brought by transient shocks. This review article compiles and assesses various energy storage technologies for reference and future research.
Integrated Demand Response Design of Integrated Energy System with Mobile Hydrogen Energy Storage in Time-Domain Two-Port Model
Dec 2022
Publication
With the development of energy integration technology demand response (DR) has gradually evolved into integrated demand response (IDR). In this study for the integrated energy system (IES) on the distribution grid side with electricity heat natural gas network and hydrogen energy equipment the analogy relationship between the thermal and mobile hydrogen energy storage networks is proposed. Moreover a unified model that reflects network commonalities across different energy forms is established. Then considering the time delay of the IES in the nontransient network a time-domain two-port model of the IES considering the time delay is established. This model shows the joint effect of time and space on system parameters. Finally this study validates the model in the application of DR. The verification results show that in DR the time-domain two-port model can accurately “cut peaks and fill valleys” for the IES and effectively reduce the operating cost of the IES system.
Multi-Objective Optimization-Based Health-Conscious Predictive Energy Management Strategy for Fuel Cell Hybrid Electric Vehicles
Feb 2022
Publication
The Energy Management Strategy (EMS) in Fuel Cell Hybrid Electric Vehicles (FCHEVs) is the key part to enhance optimal power distribution. Indeed the most recent works are focusing on optimizing hydrogen consumption without taking into consideration the degradation of embedded energy sources. In order to overcome this lack of knowledge this paper describes a new health-conscious EMS algorithm based on Model Predictive Control (MPC) which aims to minimize the battery degradation to extend its lifetime. In this proposed algorithm the health-conscious EMS is normalized in order to address its multi-objective optimization. Then weighting factors are assigned in the objective function to minimize the selected criteria. Compared to most EMSs based on optimization techniques this proposed approach does not require any information about the speed profile which allows it to be used for real-time control of FCHEV. The achieved simulation results show that the proposed approach reduces the economic cost up to 50% for some speed profile keeping the battery pack in a safe range and significantly reducing energy sources degradation. The proposed health-conscious EMS has been validated experimentally and its online operation ability clearly highlighted on a PEMFC delivery postal vehicle.
Multi-layer Coordinated Optimization of Integrated Energy System with Electric Vehicles Based on Feedback Correction
Sep 2022
Publication
The integrated energy system with electric vehicles can realize multi-energy coordination and complementarity and effectively promote the realization of low-carbon environmental protection goals. However the temporary change of vehicle travel plan will have an adverse impact on the system. Therefore a multi-layer coordinated optimization strategy of electric-thermal-hydrogen integrated energy system including vehicle to grid (V2G) load feedback correction is proposed. The strategy is based on the coordination of threelevel optimization. The electric vehicle charging and discharging management layer comprehensively considers the variance of load curve and the dissatisfaction of vehicle owners and the charging and discharging plan is obtained through multi-objective improved sparrow search algorithm which is transferred to the model predictive control rolling optimization layer. In the rolling optimization process according to the actual situation selectively enter the V2G load feedback correction layer to update V2G load so as to eliminate the impact of temporary changes in electric vehicle travel plans. Simulation results show that the total operating cost with feedback correction is 4.19% lower than that without feedback correction and tracking situation of tie-line planned value is improved which verifies the proposed strategy.
Optimization of High-Temperature Electrolysis System for Hydrogen Production Considering High-Temperature Degradation
Mar 2023
Publication
Solid oxide electrolysis cells (SOECs) have great application prospects because of their excellent performance but the long-term applications of the stacks are restricted by the structural degradation under the high-temperature conditions. Therefore an SOEC degradation model is developed and embedded in a process model of the high-temperature steam electrolysis (HTSE) system to investigate the influence of the stack degradation at the system level. The sensitivity analysis and optimization were carried out to study the influence factors of the stack degradation and system hydrogen production efficiency and search for the optimal operating conditions to improve the hydrogen production efficiency and mitigate the stack degradation. The analysis results show that the high temperature and large current density can accelerate the stack degradation but improve the hydrogen production efficiency while the high temperature gradually becomes unfavorable in the late stage. The low air-to-fuel feed ratio is beneficial to both the degradation rate and hydrogen production efficiency. The results show that the optimization method can improve the hydrogen production efficiency and inhibit the stack degradation effectively. Moreover part of the hydrogen production efficiency has to be sacrificed in order to obtain a lower stack degradation rate.
Optimal Design and Operation of Dual-Ejector PEMFC Hydrogen Supply and Circulation System
Jul 2022
Publication
A proton exchange membrane fuel cell (PEMFC) system requires an adequate hydrogen supply and circulation to achieve its expected performance and operating life. An ejector-based hydrogen circulation system can reduce the operating and maintenance costs noise and parasitic power consumption by eliminating the recirculation pump. However the ejector’s hydrogen entrainment capability restricted by its geometric parameters and flow control variability can only operate properly within a relatively narrow range of fuel cell output power. This research introduced the optimal design and operation control methods of a dual-ejector hydrogen supply/circulation system to support the full range of PEMFC system operations. The technique was demonstrated on a 70 kW PEMFC stack with an effective hydrogen entrainment ratio covering 8% to 100% of its output power. The optimal geometry design ensured each ejector covered a specific output power range with maximized entrainment capability. Furthermore the optimal control of hydrogen flow and the two ejectors’ opening and closing times minimized the anode gas pressure fluctuation and reduced the potential harm to the PEMFC’s operation life. The optimizations were based on dedicated computational fluid dynamics (CFD) and system dynamics models and simulations. Bench tests of the resulting ejector-based hydrogen supply/circulation system verified the simulation and optimization results.
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.
An Integrated Demand Response Dispatch Strategy for Low-carbon Energy Supply Park Considering Electricity-Hydrogen-Carbon Coordination
Apr 2023
Publication
Driven by the goal of ‘carbon peak carbon neutrality’ an integrated demand response strategy for integrated electricity– hydrogen energy systems is proposed for low-carbon energy supply parks considering the multi-level and multi-energy characteristics of campus-based microgrids. Firstly considering the spatial and temporal complementary nature of wind and photovoltaic generation and energy utilization the energy flow framework of the park is built based on the electricity and hydrogen energy carriers. Clean energy is employed as the main energy supply and power heat cooling and gas loads are considered energy consumption. Secondly the operation mechanism of coupled hydrogen storage hydrogen fuel cell and carbon capture equipment is analyzed in the two-stage power-to-gas conversion process. Thirdly considering the operating costs and environmental costs of the park an integrated demand response dispatch model is constructed for the coupled electricity– hydrogen–carbon system while satisfying the system equipment constraints network constraints and energy balance constraints of the park system. Finally Case study in an energy supply park system is implemented. The dispatch results of the integrated demand response with customer participation in the conventional electricity–hydrogen and electricity–hydrogen–carbon modes are compared to verify the effectiveness of the proposed strategy in renewable accommodation environmental protection and economic benefits.
Numerical Investigation on the Flame Structure and CO/NO Formations of the Laminar Premixed Biogas–Hydrogen Impinging Flame in the Wall Vicinity
Nov 2021
Publication
The near-wall flame structure and pollutant emissions of the laminar premixed biogashydrogen impinging flame were simulated with a detailed chemical mechanism. The spatial distributions of the temperature critical species and pollutant emissions near the wall of the laminar premixed biogas–hydrogen impinging flame were obtained and investigated quantitatively. The results show that the cold wall can influence the premixed combustion process in the flame front which is close to the wall but does not touch the wall and results in the obviously declined concentrations of OH H and O radicals in the premixed combustion zone. After flame quenching a high CO concentration can be observed near the wall at equivalence ratios (ϕ) of both 0.8 and 1.2. Compared with that at ϕ = 1.0 more unburned fuel is allowed to pass through the quenching zone and generate CO after flame quenching near the wall thanks to the suppressed fuel consumption rate near the wall and the excess fuel in the unburned gases at ϕ = 0.8 and 1.2 respectively. By isolating the formation routes of NO production it is found that the fast-rising trend of NO concentration near the wall in the post flame region at ϕ = 0.8 is attributed to the NO transportation from the NNH route primarily while the prompt NO production accounts for more than 90% of NO generation in the wall vicinity at ϕ = 1.2. It is thus known that thanks to the effectively increased surface-to-volume ratio the premixed combustion process in the downsized chamber will be affected more easily by the amplified cooling effects of the cold wall which will contribute to the declined combustion efficiency increased CO emission and improved prompt NO production.
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.
Optimal Configuration of Multi-Energy Storage in an Electric–Thermal–Hydrogen Integrated Energy System Considering Extreme Disaster Scenarios
Mar 2024
Publication
Extreme disasters have become increasingly common in recent years and pose significant dangers to the integrated energy system’s secure and dependable energy supply. As a vital part of an integrated energy system the energy storage system can help with emergency rescue and recovery during major disasters. In addition it can improve energy utilization rates and regulate fluctuations in renewable energy under normal conditions. In this study the sizing scheme of multienergy storage equipment in the electric–thermal–hydrogen integrated energy system is optimized; economic optimization in the regular operating scenario and resilience enhancement in extreme disaster scenarios are also considered. A refined model of multi-energy storage is constructed and a two-layer capacity configuration optimization model is proposed. This model is further enhanced by the integration of a Markov two-state fault transmission model which simulates equipment defects and improves system resilience. The optimization process is solved using the tabu chaotic quantum particle swarm optimization (TCQPSO) algorithm to provide reliable and accurate optimization results. The results indicate that addressing severe disaster situations in a capacity configuration fully leverages the reserve energy function of energy storage and enhances system resilience while maintaining economic efficiency; furthermore adjusting the load loss penalty coefficients offers a more targeted approach to the balancing of the system economy and resilience. Thus new algorithmic choices and planning strategies for future research on enhancing the resilience of integrated energy systems under extreme disaster scenarios are provided.
The Hydrogen Fuel Cell Battery: Replacing the Combustion Engine in Heavy Vehicles
Nov 2022
Publication
This opinion piece describes how the optimal integration of hydrogen-fuel-cell with battery in a heavy highly-utilised vehicle can extend vehicle range while cutting refuelling time and reducing cost compared to a pure battery electric vehicle.
Deep Decarbonisation Pathways of the Energy System in Times of Unprecedented Uncertainty in the Energy Sector
May 2023
Publication
Unprecedented investments in clean energy technology are required for a net-zero carbon energy system before temperatures breach the Paris Agreement goals. By performing a Monte-Carlo Analysis with the detailed ETSAPTIAM Integrated Assessment Model and by generating 4000 scenarios of the world’s energy system climate and economy we find that the uncertainty surrounding technology costs resource potentials climate sensitivity and the level of decoupling between energy demands and economic growth influence the efficiency of climate policies and accentuate investment risks in clean energy technologies. Contrary to other studies relying on exploring the uncertainty space via model intercomparison we find that the CO2 emissions and CO2 prices vary convexly and nonlinearly with the discount rate and climate sensitivity over time. Accounting for this uncertainty is important for designing climate policies and carbon prices to accelerate the transition. In 70% of the scenarios a 1.5 ◦C temperature overshoot was within this decade calling for immediate policy action. Delaying this action by ten years may result in 2 ◦C mitigation costs being similar to those required to reach the 1.5 ◦C target if started today with an immediate peak in emissions a larger uncertainty in the medium-term horizon and a higher effort for net-zero emissions.
Design of a Multi-inlet Solar Thermochemical Reactor for Steam Methane Reforming with Improved Performance
Feb 2023
Publication
Reactor structure design plays an important role in the performance of solar-thermal methane reforming reactors. Based on a conventional preheating reactor this study proposed a cylindrical solar methane reforming reactor with multiple inlets to vary the temperature field distribution which improved the temperature of the reaction region in the reactor thereby improving the reactor performance. A multi-physical model that considers mass momentum species and energy conservation as well as thermochemical reaction kinetics of methane reforming was applied to numerically investigate the reactor performance and analyze the factors that affect performance improvement. It was found that compared with a conventional preheating reactor the proposed cylindrical reactor with inner and external inlets for gas feeding enhanced heat recovery from the exhausted gas and provided a more suitable temperature field for the reaction in the reactor. Under different operating conditions the methane conversion in the cylindrical reactor with multi-inlet increased by 9.5% to 19.1% and the hydrogen production was enhanced by 12.1% to 40.3% in comparison with the conventional design even though the total reaction catalyst volume was reduced.
Environmental Economical Dispatching of Electric–Gas Integrated Energy System Considering Hydrogen Compressed-Natural Gas
Dec 2022
Publication
As a high-quality secondary energy hydrogen energy has great potential in energy storage and utilization. The development of power-to-hydrogen (P2H) technology has alleviated the problem of wind curtailment and improved the coupling between the power grid and the natural gas grid. Under the premise of ensuring safety using P2H technology to mix the produced hydrogen into the natural gas network for long-distance transmission and power generation can not only promote the development of hydrogen energy but also reduce carbon emissions. This paper presents a new model for incorporating hydrogen into natural gas pipelines. To minimize the sum of wind curtailment cost operation cost and carbon emission cost an electric–gas integrated energy system (EGIES) model of hydrogen-compressed natural gas (HCNG) containing P2H for power generation is constructed. Aiming at the problem of global warming caused by a lot of abandoned wind and carbon emissions the economy and environmental protection of the system model are analyzed. The results show that the model of EGIES considering HCNG can not only absorb excess wind power but also reduce carbon emission costs and system costs which can reduce the total cost of the environmental economic dispatch of the EGIES by about 34.1%. In the context of the EGIES the proposal of this model is of great significance to the economical and environmentally friendly operation of the system.
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