China, People’s Republic
A Model for Assessing the Potential Impact Radius of Hydrogen Pipelines Based on Jet Fire Radiation
Jan 2024
Publication
The accurate determination of the potential impact radius is crucial for the design and risk assessment of hydrogen pipelines. The existing methodologies employ a single point source model to estimate radiation and the potential impact radius. However these approaches overlook the jet fire shape resulting from high-pressure leaks leading to discrepancies between the calculated values and real-world incidents. This study proposes models that account for both the mass release rate while considering the pressure drop during hydrogen pipeline leakage and the radiation while incorporating the flame shape. The analysis encompasses 60 cases that are representative of hydrogen pipeline scenarios. A simplified model for the potential impact radius is subsequently correlated and its validity is confirmed through comparison with actual cases. The proposed model for the potential impact radius of hydrogen pipelines serves as a valuable reference for the enhancement of the precision of hydrogen pipeline design and risk assessment.
Review on the Thermal Neutrality of Application-orientated Liquid Organic Hydrogen Carrier for Hydrogen Energy Storage and Delivery
Aug 2023
Publication
The depletion and overuse of fossil fuels present formidable challenge to energy supply system and environment. The human society is in great need of clean renewable and sustainable energy which can guarantee the long-term utilization without leading to escalation of greenhouse effect. Hydrogen as an extraordinary secondary energy is capable of realizing the target of environmental protection and transferring the intermittent primary energy to the application terminal while its nature of low volumetric energy density and volatility need suitable storage method and proper carrier. In this context liquid organic hydrogen carrier (LOHC) among a series of storage methods such as compressed and liquefied hydrogen provokes a considerable amount of research interest since it is proven to be a suitable carrier for hydrogen with safety and stability. However the dehydrogenation of hydrogen-rich LOHC materials is an endothermic process and needs large energy consumption which hampers the scale up of the LOHC system. The heat issue is thus essential to be addressed for fulfilling the potential of LOHC. In this work several strategies of heat intensification and management for LOHC system including the microwave irradiation circulation of exhaust heat and direct LOHC fuel cell are summarized and analyzed to provide suggestions and directions for future research.
Forecasting the Development of Clean Energy Vehicles in Large Cities: A System Dynamics Perspective
Jan 2024
Publication
Clean energy vehicles (CEVs) e.g. battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs) are being adopted gradually to substitute for internal combustion engine vehicles (ICEVs) around the world. The fueling infrastructure is one of the key drivers for the development of the CEV market. When the government develops funding policies to support the fueling infrastructure development for FCEVs and BEVs it has to assess the effectiveness of different policy options and identify the optimal policy combination which is very challenging in transportation research. In this paper we develop a system dynamics model to study the feedback mechanism between the fueling infrastructure funding policies and the medium- to long-term diffusion of FCEVs and BEVs and the competition between FCEVs and BEVs based on relevant policy and market data in Guangzhou China. The results of the modeling analysis are as follows. (1) Funding hydrogen refueling stations and public charging piles has positive implications for achieving the substitution of CEVs for ICEVs. (2) Adjusting the funding ratio of hydrogen refueling stations and public charging piles or increasing the funding budget and extending the funding cycle does not have a significant impact on the overall substitution of CEVs for ICEVs but only impacts the relative competitive advantage between FCEVs and BEVs. (3) An equal share of funding for hydrogen refueling stations and public charging piles would have better strategic value for future net-zero-emissions urban transportation. (4) Making a moderate-level full investment in hydrogen refueling stations coupled with hydrogen refueling subsidies can provide the ideal conditions for FCEV diffusion.
Operation Optimization of Wind/Battery Storage/Alkaline Electrolyzer System Considering Dynamic Hydrogen Production Efficiency
Aug 2023
Publication
Hydrogen energy is regarded as a key path to combat climate change and promote sustainable economic and social development. The fluctuation of renewable energy leads to frequent start/stop cycles in hydrogen electrolysis equipment. However electrochemical energy storage with its fast response characteristics helps regulate the power of hydrogen electrolysis enabling smooth operation. In this study a multi-objective constrained operation optimization model for a wind/battery storage/alkaline electrolyzer system is constructed. Both profit maximization and power abandonment rate minimization are considered. In addition some constraints such as minimum start/stop times upper and lower power limits and input fluctuation limits are also taken into account. Then the non-dominated sorting genetic algorithm II (NSGA-II) algorithm and the entropy method are used to optimize the operation strategy of the hybrid energy system by considering dynamic hydrogen production efficiency and through optimization to obtain the best hydrogen production power of the system under the two objectives. The change in dynamic hydrogen production efficiency is mainly related to the change in electrolyzer power and the system can be better adjusted according to the actual supply of renewable energy to avoid the waste of renewable energy. Our results show that the distribution of Pareto solutions is uniform which indicates the suitability of the NSGA-II algorithm. In addition the optimal solution indicates that the battery storage and alkaline electrolyzer can complement each other in operation and achieve the absorption of wind power. The dynamic hydrogen production efficiency can make the electrolyzer operate more efficiently which paves the way for system optimization. A sensitivity analysis reveals that the profit is sensitive to the price of hydrogen energy.
Study on the Effects of the Hydrogen Substitution Rate on the Performance of a Hydrogen–Diesel Dual-Fuel Engine under Different Loads
Aug 2023
Publication
Due to having zero carbon emissions and renewable advantages hydrogen has great prospects as a renewable form of alternate energy. Engine load and hydrogen substitution rate have a considerable influence on a hydrogen–diesel dual-fuel engine’s efficiency. This experiment’s objective is to study the influence of hydrogen substitution rate on engine combustion and emission under different loads and to study the impact of exhaust gas recirculation (EGR) technology or main injection timing on the engine’s capability under high load and high hydrogen substitution rate. The range of the maximum hydrogen substitution rate was determined under different loads (30%~90%) at 1800 rpm and then the effects of the EGR rate (0%~15%) and main injection timing (−8 ◦CA ATDC~0 ◦CA ATDC) on the engine performance under 90% high load were studied. The research results show that the larger the load the smaller the maximum hydrogen substitution rate that can be added to the dual-fuel engine. Under each load with the increase of the hydrogen substitution rate the cylinder pressure and the peak heat release rate (HRR) increase the equivalent brake-specific fuel consumption (BSFCequ) decreases the thermal efficiency increases the maximum thermal efficiency is 43.1% the carbon dioxide (CO2 ) emission is effectively reduced by 35.2% and the nitrogen oxide (NOx) emission decreases at medium and low loads and the maximum increase rate is 20.1% at 90% load. Under high load with the increase of EGR rate or the delay of main injection timing the problem of NOx emission increases after hydrogen doping can be effectively solved. As the EGR rate rises from 0% to 15% the maximum reduction of NOx is 63.1% and with the delay of main injection timing from −8 ◦CA ATDC to 0 ◦CA ATDC the maximum reduction of NOx is 44.5%.
Greenhouse Gas Reduction Potential and Economics of Green Hydrogen via Water Electrolysis: A Systematic Review of Value-Chain-Wide Decarbonization
May 2024
Publication
Green hydrogen generated via water electrolysis has become an essential energy carrier for achieving carbon neutrality globally because of its versatility in renewable energy consumption and decarbonization applications in hard-to-abate sectors; however there is a lack of systematic analyses of its abatement potential and economics as an alternative to traditional technological decarbonization pathways. Based on bibliometric analysis and systematic evaluation methods this study characterizes and analyzes the literature on the Web of Science from 1996 to 2023 identifying research hotspots methodological models and research trends in green hydrogen for mitigating climate change across total value chain systems. Our review shows that this research theme has entered a rapid development phase since 2016 with developed countries possessing more scientific results and closer partnerships. Difficult-to-abate sectoral applications and cleaner production are the most famous value chain links and research hotspots focus on three major influencing factors: the environment; techno-economics; and energy. Green hydrogen applications which include carbon avoidance and embedding to realize carbon recycling have considerable carbon reduction potential; however uncertainty limits the influence of carbon reduction cost assessment indicators based on financial analysis methods for policy guidance. The abatement costs in the decarbonization sector vary widely across value chains electricity sources baseline scenarios technology mixes and time scenarios. This review shows that thematic research trends are focused on improving and optimizing solutions to uncertainties as well as studying multisectoral synergies and the application of abatement assessment metrics.
Review of the Status and Prospects of Fiber Optic Hydrogen Sensing Technology
Aug 2023
Publication
With the unprecedented development of green and renewable energy sources the proportion of clean hydrogen (H2 ) applications grows rapidly. Since H2 has physicochemical properties of being highly permeable and combustible high-performance H2 sensors to detect and monitor hydrogen concentration are essential. This review discusses a variety of fiber-optic-based H2 sensor technologies since the year 1984 including: interferometer technology fiber grating technology surface plasma resonance (SPR) technology micro lens technology evanescent field technology integrated optical waveguide technology direct transmission/reflection detection technology etc. These technologies have been evolving from simply pursuing high sensitivity and low detection limits (LDL) to focusing on multiple performance parameters to match various application demands such as: high temperature resistance fast response speed fast recovery speed large concentration range low cross sensitivity excellent long-term stability etc. On the basis of palladium (Pd)-sensitive material alloy metals catalysts or nanoparticles are proposed to improve the performance of fiberoptic-based H2 sensors including gold (Au) silver (Ag) platinum (Pt) zinc oxide (ZnO) titanium oxide (TiO2 ) tungsten oxide (WO3 ) Mg70Ti30 polydimethylsiloxane (PDMS) graphene oxide (GO) etc. Various microstructure processes of the side and end of optical fiber H2 sensors are also discussed in this review.
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.
PEM Water Electrolysis for Hydrogen Production: Fundamentals, Advances, and Prospects
Jun 2022
Publication
Hydrogen as a clean energy carrier is of great potential to be an alternative fuel in the future. Proton exchange membrane (PEM) water electrolysis is hailed as the most desired technology for high purity hydrogen production and self-consistent with volatility of renewable energies has ignited much attention in the past decades based on the high current density greater energy efficiency small mass-volume characteristic easy handling and maintenance. To date substantial efforts have been devoted to the development of advanced electrocatalysts to improve electrolytic efficiency and reduce the cost of PEM electrolyser. In this review we firstly compare the alkaline water electrolysis (AWE) solid oxide electrolysis (SOE) and PEM water electrolysis and highlight the advantages of PEM water electrolysis. Furthermore we summarize the recent progress in PEM water electrolysis including hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts in the acidic electrolyte. We also introduce other PEM cell components (including membrane electrode assembly current collector and bipolar plate). Finally the current challenges and an outlook for the future development of PEM water electrolysis technology for application in future hydrogen production are provided.
Small-Scale High-Pressure Hydrogen Storage Vessels: A Review
Feb 2024
Publication
Nowadays high-pressure hydrogen storage is the most commercially used technology owing to its high hydrogen purity rapid charging/discharging of hydrogen and low-cost manufacturing. Despite numerous reviews on hydrogen storage technologies there is a relative scarcity of comprehensive examinations specifically focused on high-pressure gaseous hydrogen storage and its associated materials. This article systematically presents the manufacturing processes and materials used for a variety of high-pressure hydrogen storage containers including metal cylinders carbon fiber composite cylinders and emerging glass material-based hydrogen storage containers. Furthermore it introduces the relevant principles and theoretical studies showcasing their advantages and disadvantages compared to conventional high-pressure hydrogen storage containers. Finally this article provides an outlook on the future development of high-pressure hydrogen storage containers.
Storage Integrity During Underground Hydrogen Storage in Depleted Gas Reservoirs
Nov 2023
Publication
The transition from fossil fuels to renewable energy sources particularly hydrogen has emerged as a central strategy for decarbonization and the pursuit of net-zero carbon emissions. Meeting the demand for large-scale hydrogen storage a crucial component of the hydrogen supply chain has led to the exploration of underground hydrogen storage as an economically viable solution to global energy needs. In contrast to other subsurface storage options such as salt caverns and aquifers which are geographically limited depleted gas reservoirs have garnered increasing attention due to their broader distribution and higher storage capacity. However the safe storage and cycling of hydrogen in depleted gas reservoirs require the preservation of high stability and integrity in the caprock reservoir and wellbore. Nevertheless there exists a significant gap in the current research concerning storage integrity in underground hydrogen storage within depleted gas reservoirs and a systematic approach is lacking. This paper aims to address this gap by reviewing the primary challenges associated with storage integrity including geochemical reactions microbial activities faults and fractures and perspectives on hydrogen cycling. The study comprehensively reviews the processes and impacts such as abiotic and biotic mineral dissolution/precipitation reactivation and propagation of faults and fractures in caprock and host-rock wellbore instability due to cement degradation and casing corrosion and stress changes during hydrogen cycling. To provide a practical solution a technical screening tool has been developed considering controlling variables risks and consequences affecting storage integrity. Finally this paper highlights knowledge gaps and suggests feasible methods and pathways to mitigate these risks facilitating the development of large-scale underground hydrogen storage in depleted gas reservoirs.
CFD Analysis of Hydrogen Leakage from a Small Hole in a Sloping Roof Hydrogen Refueling Station
Sep 2023
Publication
As a key link in the application of hydrogen energy hydrogen refueling stations are significant for their safe operation. This paper established a three-dimensional 1:1 model for a seaport hydrogen refueling station in Ningbo City. In this work the CFD software FLUENT was used to study the influence of leakage angles on the leakage of high-pressure hydrogen through a small hole. Considering the calculation accuracy and efficiency this paper adopted the pseudo-diameter model. When the obstacle was far from the leakage hole it had almost no obstructive effect on the jet's main body. Still it affected the hydrogen whose momentum in the outer layer of the jet has been significantly decayed. In this condition there would be more hydrogen in stagnation. Thus the volume of the flammable hydrogen cloud was hardly affected while there was a significant increase in the volume of the hazardous hydrogen cloud. When the obstacle was close to the leakage hole it directly affected the jet's main body. Therefore the volume of the flammable hydrogen cloud increased. However the air impeded the hydrogen jet relatively less because the hydrogen jet contacted the obstacle more quickly. The hydrogen jet blocked by the obstacle still has some momentum. Therefore there was no more hydrogen in stagnation and no significant increase in the volume of the hazardous hydrogen cloud.
Gas Crossover Predictive Modelling Using Artificial Neural Networks Based on Original Dataset Through Aspen Custom Modeler for Proton Exchange Membrane Electrolyte System
Sep 2023
Publication
Proton exchange membrane electrolyzer cell (PEMEC) will play a central role in future power-to-H2 plants. Current research focuses on the materials and operation parameters. Setting up experiments to explore operational accident scenarios about safety feasibility is not always practical. This paper focuses on building mathematical and prediction models of hydrogen and oxygen mixing scenarios of PEMEC. A mathematical model of the PEMEC device was customized in the Aspen Custom Model (ACM) software and integrated various critical Physico-chemical phenomena as the original data set for the prediction model. The results of the mathematical simulation verified the experimental results. The prediction model proposes an artificial neural network (ANN) framework to predict component distribution in the gas stream to prevent hydrogen-oxygen explosion scenarios. The presented approach by training ANN to 1000 sets of hydrogen-oxygen mixing simulation data from ACM is applicable to bypass tedious and non-smooth systems of equations for PEMEC.
Effect of Wall Friction on Shock-flame Interactions in a Hydrogen-air Mixture
Sep 2023
Publication
Shock-flame interactions (SFI) occur in a variety of combustion scenarios of scientific and engineering interest which can distort the flame extend the flame surface area and subsequently enhance heat release. This process is dominated by Richtmyer-Meshkov instability (RMI) that features the perturbation growth of a density-difference interface (flame) after the shock passage. The main mechanism of RMI is the vorticity deposition results from a misalignment between pressure and density gradients. This paper focuses on the multi-dimensional interactions between shock wave and flame in a hydrogen-air mixture. The simulations of this work were conducted by solving three-dimensional fully-compressible reactive Navier-Stokes equations using a high-order numerical method on a dynamically adapting mesh. The effect of wall friction on the SFI was examined by varying wall boundary condition (free-slip/no-slip) on sidewall. The results show that the global flame perturbation grows faster with the effect of wall friction in the no-slip case than that in the free-slip case in the process of SFI. Two effects of wall friction on SFI were found: (1) flame stretching close to the no-slip wall and (2) damping of local flame perturbation at the no-slip wall. The flame stretch effect leads to a significantly higher growth rate in the global flame perturbation. By contrast the damping effect locally moderates the flame perturbation induced by RMI in close proximity to the no-slip wall because less vorticity is deposited on this part of flame during SFI.
Analytical Model of Cryogenic Hydrogen Releases
Sep 2023
Publication
Hydrogen is one of the most promising alternative sources to relieve the energy crisis and environmental pollution. Hydrogen can be stored as cryogenic compressed hydrogen (CcH2) to achieve high volumetric energy densities. Reliable safety codes and standards are needed for hydrogen production delivery and storage to promote hydrogen commercialization. Unintended hydrogen releases from cryogenic storage systems are potential accident scenarios that are of great interest for updating safety codes and standards. This study investigated the behavior of CcH2 releases and dispersion. The extremely low-temperature CcH2 jets can cause condensation of the air components including water vapor nitrogen and oxygen. An integral model considering the condensation effects was developed to predict the CcH2 jet trajectories and concentration distributions. The thermophysical properties were obtained from the COOLPROP database. The model divides the CcH2 jet into the underexpanded initial entrainment and heating flow establishment and established flow zones. The condensation effects on the heat transfer and flow were included in the initial entrainment and heating zones. The empirical coefficients in the integral model were then modified based on measured concentration results. Finally the analytical model predictions are shown to compare well with measured data to verify the model accuracy. The present study can be used to develop quantitative risk assessment models and update safety codes and standards for cryogenic hydrogen facilities.
Numerical Simulation of Underexpanded Cryogenic Hydrogen Jets
Sep 2023
Publication
As a clean and renewable energy carrier hydrogen is one of the most promising alternative fuels. Cryogenic compressed hydrogen can achieve high storage density without liquefying hydrogen which has good application prospects. Investigation of the safety problems of cryogenic compressed hydrogen is necessary before massive commercialization. The present study modeled the instantaneous flow field using the Large Eddy Simulation (LES) for cryogenic (50 and 100 K) underexpanded hydrogen jets released from a round nozzle of 1.5 mm diameter at pressures of 0.5-5.0 MPa. The simulation results were compared with the experimental data for validation. The axial and radial concentration and velocity distributions were normalized to show the self-similar characteristics of underexpanded cryogenic jets. The shock structures near the nozzle were quantified to correlate the shock structure sizes to the source pressure and nozzle diameter. The present study on the concentration and velocity distributions of underexpanded cryogenic hydrogen jets is useful for developing safety codes and standards.
Hydrogen Release Modelling for Analysis Using Data-driven Autoencoder with Convolutional Neural Networks
Sep 2023
Publication
High-accuracy gas dispersion models are necessary for predicting hydrogen movement and for reducing the damage caused by hydrogen release accidents in chemical processes. In urban areas where obstacles are large and abundant computational fluid dynamics (CFD) would be the best choice for simulating and analyzing scenarios of the accidental release of hydrogen. However owing to the large computation time required for CFD simulation it is inappropriate in emergencies and real-time alarm systems. In this study a non-linear surrogate model based on deep learning is proposed. Deep convolutional layer data-driven autoencoder and batch normalized deep neural network is used to analyze the effects of wind speed wind direction and release degree on hydrogen concentration in real-time. The typical parameters of hydrogen diffusion accidents at hydrogen refuelling stations were acquired by CFD numerical simulation approach and a database of hydrogen diffusion accident parameters is established. By establishing an appropriate neural network structure and associated activation function a deep learning framework is created and then a deep learning model is constructed. The accuracy and timeliness of the model are assessed by comparing the results of the CFD simulation with those of the deep learning model. To develop a dynamic reconfiguration prediction model for the hydrogen refuelling station diffusion scenario the algorithm is continuously enhanced and the model is improved. After training is finished the model's prediction time is measured in seconds which is 105 times quicker than field CFD simulations. The deep learning model of hydrogen release in hydrogen refuelling stations is established to realize timely and accurate prediction and simulation of accident consequences and provide decision-making suggestions for emergency rescue and personnel evacuation which is of great significance for the protection of human life health and property safety.
Examining the Nature of Two-dimensional Transverse Waves in Marginal Hydrogen Detonations using Boundary Layer Loss Modeling with Detailed Chemistry
Sep 2023
Publication
Historically it has been a challenge to simulate the experimentally observed cellular structures and marginal behavior of multidimensional hydrogen-oxygen detonations in the presence of losses even with detailed chemistry models. Very recently a quasi-two-dimensional inviscid approach was pursued where losses due to viscous boundary layers were modeled by the inclusion of an equivalent mass divergence in the lateral direction using Fay’s source term formulation with Mirels’ compressible boundary layer solutions. The same approach was used for this study along with the inclusion of thermally perfect detailed chemistry in order to capture the correct ignition sensitivity of the gas to dynamic changes in the thermodynamic state behind the detonation front. In addition the strength of transverse waves and their impact on the detonation front was investigated. Here the detailed San Diego mechanism was applied and it has been found that the detonation cell sizes can be accurately predicted without the need to prescribe specific parameters for the combustion model. For marginal cases where the detonation waves approach their failure limit quasi-stable mode behavior was observed where the number of transverse waves monotonically decreased to a single strong wave over a long enough distance. The strong transverse waves were also found to be slightly weaker than the detonation front indicating that they are not overdriven in agreement with recent studies.
Design of Long-Life Wireless Near-Field Hydrogen Gas Sensor
Sep 2023
Publication
A wireless near-field hydrogen gas sensor is proposed which detects the leaking hydrogen near its source to achieve fast response and high reliability. The proposed sensor can detect leaking hydrogen in 100ms with nearly no delay due to hydrogen diffusion in space. The overall response time is shortened by orders of magnitude compared to conventional sensors according to simulation results. Over 1 year of maintenance interval is empowered by wireless design based on Bluetooth low energy protocol.
Improvement of MC Method in SAE J2601 Hydrogen Refuelling Protocol Using Dual-zone Dual-Temperature Model
Sep 2023
Publication
The MC method refuelling protocol in SAE J2601 has been published by the Society of Automotive Engineers (SAE) in order to safely and quickly refuel hydrogen vehicles. For the calculation method of the pressure target to control the refuelling stop we introduced a dual-zone dual-temperature model that distinguishes the hydrogen temperature in the tank from the wall temperature to replace the dual-zone single-temperature model of the original MC method. The total amount of heat transferred by convection between hydrogen and the inner tank wall during the filling process was expressed as an equation of final hydrogen temperature final wall temperature final refuelling time tank inner surface area and the correction factor. The correction factor equations were determined by fitting simulation data from the 0D1D model where hydrogen inside the tank is lumped parameter model (0D) and the tank wall is a one-dimensional model (1D). For the correction factor of the linear equation its first-order coefficient and constant term have a linear relationship with the initial pressure of the storage tank and their R2 values obtained from the fitting are greater than 0.99. Finally we derived a new equation to calculate the final hydrogen temperature which can be combined with the 100% SOC inside the vehicle tank to determine the pressure target. The simulation results show that the final SOC obtained are all greater than 96% using the modified pressure target and the correction factor of the linear equation.
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