Publications
Hydrogen Embrittlement Behaviors During SSRT Tests in Gaseous Hydrogen for Cold-word Type 316 Austenitic Stainless Steel and Iron-based Supperalloy A286 Used in Hydrogen Refueling Station
Feb 2024
Publication
To consider an appropriate evaluation method for hydrogen compatibility slow strain rate tensile (SSRT) tests were conducted on high strength piping materials cold-worked type 316 austenitic stainless steel (SUS316CW) and iron-based superalloy A286 used in hydrogen stations for two years.<br/>SUS316CW used at room temperature in 82 MPa gaseous hydrogen contained 7.8 mass ppm hydrogen. The SSRT test of SUS316CW was conducted in nitrogen at -40 °C. The fracture surface showed dimples and no hydrogen embrittlement behavior was observed. While the SSRT test of SUS316CW in 70 MPa gaseous hydrogen at -40 °C showed a slight decrease in reduction area and a brittle fracture morphology in the outer layer. This was considered to be the effect of high-pressure gaseous hydrogen during the SSRT test in addition to the pre-contained hydrogen.<br/>A286 used at -40 °C in 82 MPa gaseous hydrogen contained negligible hydrogen (0.14 mass ppm). SSRT tests were conducted at 150 °C in 70 MPa gaseous hydrogen and in air and showed a low relative reduction in area (RRA) value. To investigate the decrease in the RRA we switched the gas from hydrogen to air in the middle of the SSRT test and closely examined the RRA values and fracture morphology including side cracks. The hydrogen embrittlement was found to originate from the elastic deformation region. Stress cycling in the elastic deformation region also accelerated the effect of hydrogen. These were attributed to an increase in the lattice hydrogen content. While in the plastic deformation region hydrogen trapped in the defects and hydrogen through the generated surface cracks increased the hydrogen content at the crack tips reducing the RRA value. And there was a good correlation between the crack lengths and RRA values.<br/>Then hydrogen embrittlement mechanism depends on the operating conditions (stress and temperature) of the material and evaluating the hydrogen compatibility of materials by controlling their hydrogen content and strain according to the service environment is desirable.
Hydrogen Production from Wastewater: A Comprehensive Review of Conventional and Solar Powered Technologies
Mar 2024
Publication
The need to reduce the carbon footprint of conventional energy sources has made green hydrogen a promising solution for the energy transition. The most environmentally friendly way to produce hydrogen is through water-based production using renewable energy. However the availability of fresh water is limited so switching to wastewater instead of fresh water is the key solution to this problem. In response to this issue the present review reports the main findings of the research studies dealing with the feasibility of hydrogen production from wastewater using various technologies including biological electrochemical and advanced oxidation routes. These methods have been studied in a large number of experiments with the aim of investigating and improving the potential of each method. On the other hand the maturity of solar energy technologies has led researchers to focus on the possibility of harnessing this source and combining it with wastewater treatment techniques for the production of green hydrogen. Therefore the present review pays special attention to solar driven hydrogen production from wastewater by highlighting the potential of several technologies for simultaneous water treatment and green hydrogen production from wastewater. Recent results limitations challenges possible improvements and techno-economic assessments reported by several authors as well as future directions of research and industrial implementation in this field are reported.
Multi-state Load Model for Multiple Hydrogen Electrolysers Operation in the Power Grid
Jan 2025
Publication
This paper presents multiple hydrogen electrolysers integrations in the power grid and their operational stra tegies for better performance. Electrolysers have been considered as electrical loads and multi-state load model for the operation of an electrolysers have been proposed. Strategy for the operation of multiple electrolysers at different positions in a grid are formulated and Multi-State Round Robin strategy is proposed. The proposed strategy is validated by implementing that to a coastal power grid and to meet the hydrogen energy demand of vessels at the ports. Simulation has been conducted modeling the grid and electrolysers in DIgSILENT Power factory. A comparison has been performed between two state load model and multi state load model considering Multi-State Round Robin operational strategy. Line loading and hydrogen production are the considered per formance indicators. The results show that the proposed model and strategy improves the hydrogen production and operational flexibility of the system.
Hydrogen-induced Calcite Dissolution in Amaltheenton Formation Claystones: Implications for Underground Hydrogen Storage Caprock Integrity
Aug 2022
Publication
With the rising potential of underground hydrogen storage (UHS) in depleted oil and gas reservoirs or deep saline aquifers questions remain regarding changes to geological units due to interaction with injected hydrogen. Of particular importance is the integrity of potential caprocks/seals with respect to UHS. The results of this study show significant dissolution of calcite fossil fragments in claystone caprock proxies that were treated with a combination of hydrogen and 10 wt% NaCl brine. This is the first time it has been experimentally observed in claystones. The purpose of this short communication is to document the initial results that indicate the potential alteration of caprocks with injected hydrogen and to further highlight the need for hydrogen-specific studies of caprocks in areas proposed for UHS.
Development of Electric Power Generator by Using Hydrogen
Nov 2023
Publication
In this research we developed a hydrogen (H2 ) electric generator in an H2 generation system based on chemical reactions. In the experiment we tested the performance of the H2 electric generator and measured the amount of H2 generated. The maximum output was 700 W and the thermal efficiency was 18.2%. The theoretical value and measured value were almost the same and the maximum error was 4%.
Design and Optimal Sizing of a Hydrogen Uninterruptable Power Supply (UPS) System for Addressing Residential Power Cutoffs
Jan 2025
Publication
Hydrogen (H2) offers a green medium for storing the excess from renewables production instead of dumping it thus being crucial to decarbonisation efforts. Hydrogen also offers a storage medium for the grid’s cheap electricity to be used during grid peak demand or grid power cutoffs. Funded by the Scottish Government’s Emerging Energy Technologies this paper presents the design and performance analysis of a hydrogen uninterruptible power supply (H2GEN) for Cygnas Solutions Ltd. which is intended to enable continuity of supply in the residential sector while eradicating the need for environmentally and health risky lead–acid batteries and diesel generator backup. This paper presents the design optimal sizing and analysis of two H2Gen architectures one powered by the grid alone and the other powered by both the grid and a renewable (PV) source. By developing a model of each architecture in the HOMER space and using residential location weather data the home yearly load–demand profile and the grid yearly power outages profile in the developed models the optimal sizing of each H2Gen design was realised by minimising the costs while ensuring the H2Gen meets the home power demand during grid outages To enable HOMER to optimise its selection the sizes technical specifications and costs of all the market-available H2GEN components were added in the HOMER search space. Moreover the developed models were also used in assessing the sensitivity of the simulation outputs to several changes in the modelled system design and settings. Using a residential home with frequent power outages in New Delhi India as a case study it was found that the optimal sizing of H2Gen Architecture 1 is comprised of a 2 kW electrolyser a 0.2 kg type-I tank and a 2 kW water-cooled fuel cell directly connected to the AC bus offering an operational lifetime of 14.3 years. It was also found that the optimal sizing of Architecture 2 is comprised of a 1 kV PV utilised with the same 2 kW electrolyser 0.2 kg type-I tank and 2 kW water-cooled fuel cell connected to the AC bus. While the second design was found to have a higher capital cost due to the added PV it offered a more cost-effective and environmentally friendly architecture which contributes to the ongoing energy transition. This paper further investigated the capacity expansion of each H2GEN architecture to meet higher load demands or increased grid power outages. From the analysis of the simulation results it has been concluded that the most feasible and cost-effective H2GEN system expansion for meeting increased power demands or increased grid outages can be realised by using the developed models for optimally sizing the expanded H2Gen on a case-by-case basis because the increase in these profiles is highly time-dependent (for example an increased load demand or increased grid outage in the morning can be met by the PV while in the evening it must be met by the H2GEN). Finally this paper investigated the impact of other environmental variables such as the temperature and relative humidity on the H2GEN’s performance and provided further insights into increasing the overall system efficiency and cost benefit through utilising the H2GEN’s exhaust heat in the home space for heating/cooling and selling the electrolyser exhaust’s O2 as a commodity.
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.
Experimental Investigation on the Optimal Injection and Combustion Phasing for a Direct Injection Hydrogen-fuelled Internal Combustion Engine for Heavy-duty Applications
Dec 2024
Publication
In the current context of increasing demand for clean transportation hydrogen usage in internal combustion engines (ICEs) represents a viable solution to abate all engine-out criteria pollutants and almost zeroing CO2 tailpipe emissions. Indeed the wider flammability limits thanks to the higher flame propagation speed and the lower minimum ignition energy compared with conventional fuels extend the stable combustion regime to leaner mixtures thus allowing high thermal efficiency keeping under control the NOX emissions. To fully exploit the potential of hydrogen as a fuel and to avoid undesired abnormal combustion processes a deep characterization of the combustion process is needed. With this aim a 6-cylinder 12.9-L heavy-duty engine was converted from a port-fuel injected compressed natural gas to a direct injected hydrogen spark ignition one. A wide experimental campaign was carried out consisting of several sweeps of relative air-fuel ratios spark advances and injection timings at different engine speeds and loads aiming to define a preliminary engine map. The effect of each calibration parameter at different engine load and speed has been analyzed through the combination of relevant combustion parameters as well as NOX emissions. The results have demonstrated the critical influence of the mixture inhomogeneity when the injection is retarded through the top dead center firing as indicated by the increase in NOX emissions and combustion variability. The analysis of the combustion timing has indicated the dependence of the optimal MFB50 on the relative air-fuel ratio. Lastly the analysis of 200 consecutive cycles for each operating condition has allowed the evaluation of the influence of the main calibration parameters on the cyclic variability thus providing further insights about the lean limit of hydrogen in ICE.
Optimization of Injection Molding Process Parameters for the Lining of IV Hydrogen Storage Cylinder
Jan 2023
Publication
The hydrogen storage cylinder lining was taken as the research object. The injection model of the cylinder liner was developed employing 3D software a two-cavity injection molding system was built and Moldfow was utilized for analysis to determine the best combination of injection molding process parameters. The efects of injection process parameters (melt temperature mold temperature holding pressure holding time and cooling time) on the evaluation index were analyzed by orthogonal experiment L16(45 ). The prediction data of IV hydrogen storage cylinder lining under diferent parameters were obtained by the range analysis method. The multi-objective optimization problem of injection molding process was transformed into a single-objective optimization problem by using the grey correlation analysis method. The optimal parameters such as melt temperature 270 °C mold temperature 80 °C packing pressure 55 MPa packing time 20 s and cooling time 13 s were obtained. Taguchi method was adopted to obtain SNR (signal-to-noise ratio) while range and variance methods were used for analysis. The results showed that warpage was 0.4892 mm the volume shrinkage was 12.31% the residual stress in the frst direction was 98.13 MPa and the residual stress in the second direction was 108.1 MPa. The comprehensive index was simultaneously most impacted by the melt temperature.
Review on Bubble Dynamics in Proton Exchange Membrane Water Electrolysis: Towards Optimal Green Hydrogen Yield
Dec 2023
Publication
Water electrolysis using a proton exchange membrane (PEM) holds substantial promise to produce green hydrogen with zero carbon discharge. Although various techniques are available to produce hydrogen gas the water electrolysis process tends to be more cost-effective with greater advantages for energy storage devices. However one of the challenges associated with PEM water electrolysis is the accumulation of gas bubbles which can impair cell performance and result in lower hydrogen output. Achieving an in-depth knowledge of bubble dynamics during electrolysis is essential for optimal cell performance. This review paper discusses bubble behaviors measuring techniques and other aspects of bubble dynamics in PEM water electrolysis. It also examines bubble behavior under different operating conditions as well as the system geometry. The current review paper will further improve the understanding of bubble dynamics in PEM water electrolysis facilitating more competent inexpensive and feasible green hydrogen production.
A Review of the Mechanics of Lined Engineered Cavities and their Implications on Hydrogen Storage
Jan 2025
Publication
Large-scale hydrogen storage at scales ranging from gigawatt-hours (GWh) to terawatt-hours (TWh) is currently projected to be an important component of the lowest cost options for a 100% variable renewable energy system driven partly by benefits to the grid from converting variable renewable electricity into hydrogen and partly by the anticipated growing role of hydrogen in a future net-zero energy system. Lined engineered cavities (LEC)s are among the prospective types of underground storage technology because they enable hydrogen storage at highpressure in the gaseous form and are expected to not rely on specific types of rock mass. They fill a niche in moderate storage capacity and cost because of their complementary advantages. An overview of various possible configurations and materials suitable for LECs for storing hydrogen is first reviewed to identify potential cost savings and performance improvements. Amongst the various LEC configurations lined engineered shafts (LES) are identified as having the greatest potential for cost reduction in softer rock masses such as sedimentary formations due to reduced excavation and construction complexity. Despite these advantages significant gaps remain in understanding the long-term behaviour of LES under cyclical loading as revealed through a review of the theoretical and experimental techniques used to study similar LEC configurations. This review paper con cludes with several recommendations for future research in numerical model formulation and material advancement with strong potential to increase the feasibility of LESs for hydrogen storage.
Hydrogen Balloon Transportation: A Cheap and Efficiency Mode to Transport Hydrogen
Nov 2023
Publication
The chances of a global hydrogen economy becoming a reality have increased significantly since the COVID pandemic and the war in Ukraine and for net zero carbon emissions. However intercontinental hydrogen transport is still a major issue. This study suggests transporting hydrogen as a gas at atmospheric pressure in balloons using the natural flow of wind to carry the balloon to its destination. We investigate the average wind speeds atmospheric pressure and temperature at different altitudes for this purpose. The ideal altitudes to transport hydrogen with balloons are 10 km or lower and hydrogen pressures in the balloon vary from 0.25 to 1 bar. Transporting hydrogen from North America to Europe at a maximum 4 km altitude would take around 4.8 days on average. Hydrogen balloon transportation cost is estimated at 0.08 USD/kg of hydrogen which is around 12 times smaller than the cost of transporting liquified hydrogen from the USA to Europe. Due to its reduced energy consumption and capital cost in some locations hydrogen balloon transportation might be a viable option for shipping hydrogen compared to liquefied hydrogen and other transport technologies.
Heat and Mass Transfer Modeling of Vacuum Insulated Vessel Storing Cryogenic Liquid in Loss of Vacuum Accident
Sep 2023
Publication
Cryogenic liquid is often stored in a vacuum insulated Dewar vessel for a high efficiency of thermal insulation. Multi-layer insulation (MLI) can be further applied in the double-walled vacuum space to reduce the heat transfer from the environment to the stored cryogenic fluid. However in loss-of-vacuum accident (LOVA) scenarios heat flux across the MLI will raise to orders of magnitudes larger than with an intact vacuum shield. The cryogenic liquid will boil intensively and pressurize the vessel due to the heat ingress. The pressurization endangers the integrity of the vessel and poses an extra catastrophic risk if the vapor is flammable e.g. hydrogen. Therefore safety valves have to be designed and installed appropriately to make sure the pressure is limited to acceptable levels. In this work the dynamic process of the heat and mass transfers in the LOVA scenarios is studied theoretically. The mass deposition - desublimation of gaseous nitrogen on cryogenic surfaces is modeled as it provides the dominant contribution of the thermal load to the cryogenic fluid. The conventional heat convection and radiation are modeled too although they play only secondary roles as realized in the course of the study. The temperature dependent thermal properties of e.g. gaseous and solid nitrogen and stainless steel are used to improve the accuracy of calculation in the cryogenic temperature range. Presented methodology enabling the computation of thermodynamic parameters in the cryogenic storage system during LOVA scenarios provides further support for the future risk assessment and safety system design.
Mathematical Optimization Modeling for Scenario Analysis of Integrated Steelworks Transitioning Towards Hydrogen-based Reduction
Jul 2024
Publication
To reduce carbon dioxide emissions from the steel industry efforts are made to introduce a steelmaking route based on hydrogen reduction of iron ore instead of the commonly used cokebased reduction in a blast furnace. Changing fundamental pieces of steelworks affects the functions of most every system unit involved and thus warrants the question of how such a transition could optimally take place over time and no rigorous attempts have until now been made to tackle this problem mathematically. This article presents a steel plant optimization model written as a mixed-integer non-linear programming problem where aging blast furnaces and basic oxygen furnaces could potentially be replaced with shaft furnaces and electric arc furnaces minimizing costs or emissions over a long-term time horizon to identify possible transition pathways. Example cases show how various parameters affect optimal investment pathways stressing the necessity of appropriate planning tools for analyzing diverse cases.
Influence of Air Changes Per Hour on Hydrogen Leaks in Mechanically Ventilated Enclosures
Mar 2024
Publication
The integration of hydrogen energy systems into nearly zero-emission buildings (nZEB) is emerging as a viable strategy to curtail greenhouse gas emissions associated with energy use in these buildings. However the indoor or outdoor placement of certain hydrogen system components or equipment necessitates stringent safety measures particularly in confined environments. This study aims to investigate the dynamics of hydrogen dispersion within an enclosure featuring forced ventilation analyzing the interplay between leakage flow rates and ventilation efficiency both experimentally and numerically. To simulate hydrogen's behavior helium gas which shares similar physical characteristics with hydrogen was utilized in experiments conducted at leakage flows of 4 8 and 10 L/min alongside a ventilation rate of 30 air changes per hour (ACH). The experiments revealed that irrespective of the leakage rate the oxygen concentration returned to its initial level approximately 11 min post-leakage at a ventilation rate of 30 ACH. This study also encompasses a numerical analysis to validate the experimental findings and assess the congruence between helium and hydrogen behaviors. Additionally the impact of varying ACH rates (30 45 60 75) on the concentrations of oxygen and hydrogen was quantified through numerical analysis for different hydrogen leakage rates (4 8 10 20 L/min). The insights derived from this research offer valuable guidance for building facility engineers on designing ventilation systems that ensure hydrogen and oxygen concentrations remain within safe limits in hydrogen-utilizing indoor environments.
Techno‑Economic Comparative Analysis of Two Hybrid Renewable Energy Systems for Powering a Simulated House, including a Hydrogen Vehicle Load at Jeju Island
Nov 2023
Publication
This work undertakes a techno‑economic comparative analysis of the design of photo‑ voltaic panel/wind turbine/electrolyzer‑H2 tank–fuel cell/electrolyzer‑H2 tank (configuration 1) and photovoltaic panel/wind turbine/battery/electrolyzer‑H2 tank (configuration 2) to supply electricity to a simulated house and a hydrogen‑powered vehicle on Jeju Island. The aim is to find a system that will make optimum use of the excess energy produced by renewable energies to power the hydrogen vehicle while guaranteeing the reliability and cost‑effectiveness of the entire system. In addition to evaluating the Loss of Power Supply Probability (LPSP) and the Levelized Cost of Energy (LCOE) the search for achieving that objective leads to the evaluation of two new performance indicators: Loss of Hydrogen Supply Probability (LHSP) and Levelized Cost of Hydrogen (LCOH). After anal‑ ysis for 0 < LPSP < 1 and 0 < LHSP < 1 used as the constraints in a multi‑objective genetic algorithm configuration 1 turns out to be the most efficient loads feeder with an LCOE of 0.3322 USD/kWh an LPSP of 0% concerning the simulated house load an LCOH of 11.5671 USD/kg for a 5 kg hydrogen storage and an LHSP of 0.0043% regarding the hydrogen vehicle load.
Acidification-based Direct Electrolysis of Treated Wastewater for Hydrogen Production and Water Reuse
Oct 2023
Publication
This report describes the direct electrolysis of treated wastewater (as a catholyte) to produce hydrogen and potentially reuse the water. To suppress the negative shift of the cathodic potential due to an increase in pH by the hydrogen evolution reaction (HER) the treated wastewater is acidified using the synergetic effect of protons generated from the bipolar membrane and inor ganic precipitation occurred at the surface of the cathode during the HER. Natural seawater as an accessible source for Mg2+ ions was added to the treated wastewater because the concentration of Mg2+ ions contained in the original wastewater was too low for acidification to occur. The mixture of treated wastewater with seawater was acidified to pH 3 allowing the initial cathode potential to be maintained for more than 100 h. The amount of inorganic precipitates formed on the cathode surface is greater than that in the control case (adding 0.5 M NaCl instead of seawater) but does not adversely affect the cathodic potential and Faradaic efficiency for H2 production. Additionally it was confirmed that less organic matter was adsorbed to the inorganic deposits under acidic conditions. These indicate that acidification plays an important role in improving the performance and stability of low-grade water electrolysis. Considering that the treated wastewater is discharged near the ocean acidification-based electrolysis of the effluent with seawater can be a water reuse technology for green hydrogen production enhancing water resilience and contributing to the circular economy of water resources.
Key Components and Design Strategy for a Proton Exchange Membrane Water Electrolyzer
Oct 2022
Publication
As the most attractive energy carrier hydrogen production through electro-chemical water splitting (EWS) is promising for resolving the serious environ-mental problems derived from the rapid consumption of fossil fuels globally. Theproton exchange membrane water electrolyzer (PEMWE) is one of the mostpromising EWS technologies and has achieved great advancements. To offer atimely reference for the progress of the PEMWE system the latest advancementsand developments of PEMWE technology are systematically reviewed. The keycomponents including the electrocatalysts PEM and porous transport layer(PTL) as well as bipolar plate (BPP) are first introduced and discussed followedby the membrane electrode assembly and cell design. The highlights are put onthe design of the electrocatalyst and the relationship of each component on theperformance of the PEMWE. Moreover the current challenges and future per-spectives for the development of PEMWE are also discussed. There is a hope thatthis review can provide a timely reference for future directions in PEMWEchallenges and perspectives.
A Study on Hydrogen Embrittlement of a High-strength Pipeline Steel Weldment after Microstructure Manipulation by Targeted Heat Treatments
Dec 2024
Publication
Hydrogen embrittlement (HE) is a major concern when steel pipelines are used for hydrogen transportation and storage. The weldments of steel pipelines are of particular concern because they are reported to have higher HE susceptibility compare to the base metal. In this work targeted heat treatments were used to manipulate the microstructure in a pipeline steel weldment to examine the effects of different microstructural features on HE susceptibility. Complementary analyses of the microstructure mechanical testing and fracture surface identified inclusions and ferrite morphology as the most dominant microstructural features that affect the susceptibility to HE. Specimens with different microstructures but sharing similar Ti-rich inclusions exhibited significant re ductions in elongation to failure after hydrogen charging and showed brittle fracture surfaces decorated with multiple ‘fish-eye’ features. In addition co-existence of bainitic microstructure with Ti-rich inclusions resulted in the highest susceptibility to HE.
An Overview of Hydrogen Storage Technologies - Key Challenges and Opportunities
Jul 2024
Publication
Hydrogen energy has been proposed as a reliable and sustainable source of energy which could play an integral part in demand for foreseeable environmentally friendly energy. Biomass fossil fuels waste products and clean energy sources like solar and wind power can all be employed for producing hydrogen. This comprehensive review paper provides a thorough overview of various hydrogen storage technologies available today along with the benefits and drawbacks of each technology in context with storage capacity efficiency safety and cost. Since safety concerns are among the major barriers to the broad application of H2 as a fuel source special attention has been paid to the safety implications of various H2 storage techniques. In addition this paper highlights the key challenges and opportunities facing the development and commercialization of hydrogen storage technologies including the need for improved materials enhanced system integration increased awareness and acceptance. Finally recommendations for future research and development with a particular focus on advancing these technologies towards commercial viability.
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