- Home
- A-Z Publications
- Publications
Publications
Experimental Investigation of the Effect of Hydrogen on Fracture Toughness of 2.25Cr-1Mo-0.25V Steel and Welds after Annealing
Mar 2018
Publication
Hydrogen embrittlement (HE) is a critical issue that hinders the reliability of hydrogenation reactors. Hence it is of great significance to investigate the effect of hydrogen on fracture toughness of 2.25Cr-1Mo-0.25V steel and weld. In this work the fracture behavior of 2.25Cr-1Mo-0.25V steel and welds was studied by three-point bending tests under hydrogen-free and hydrogen-charged conditions. The immersion charging method was employed to pre-charge hydrogen inside specimen and the fracture toughness of these joints was evaluated quantitatively. The microstructure and grain size of the specimens were observed by scanning electron microscopy (SEM) and by metallurgical microscopy to investigate the HE mechanisms. It was found that fracture toughness for both the base metal (BM) and the weld zone (WZ) significantly decreased under hydrogen-charged conditions due to the coexistence of the hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP) mechanisms. Moreover the formation and growth of primary voids were observed in the BM leading to a superior fracture toughness. In addition the BM compared to the WZ shows superior resistance to HE because the finer grain size in the BM leads to a larger grain boundary area thus distributing more of the diffusive hydrogen trapped in the grain boundary and reducing the hydrogen content.
The Role of Initial Tank Temperature on Refuelling of On-board Hydrogen Tanks
Jun 2016
Publication
The influence of the initial tank temperature on the evolution of the internal gas temperature during the refuelling of on-board hydrogen tanks is investigated in this paper. Two different types of tanks four different fuel delivery temperatures (from ambient temperature refuelling to a pre-cooled hydrogen at −40 °C) several filling rates and initial pressures are considered. It has been found that the final gas temperature increases linearly with the increase of the initial tank temperature while the temperature increase (ΔT) and the final state of charge (SOC) decrease linearly with increasing the initial temperature. This dependency has been found to be larger on type III than on type IV tank and larger the larger the initial pressure. Additionally CFD simulations are performed to better understand the role of the relevant phenomena on the gas temperature histories e.g. gas compression gas mixing and heat transfer. By comparing the results of calculations with adiabatic and diathermal tank walls the effect of the initial gas temperature has been separated from the effect of the initial wall temperature on the process.
Experimental Study on Accumulation of Helium Released into a Semi-confined Enclosure without Ventilation
Sep 2019
Publication
This paper examines the helium dispersion behaviour in a 16.6 m3 enclosure with a small opening in the floor and distributed leaks along the edges. Helium a simulant for hydrogen was injected near the center of the floor with an injection rate ranging from 2 to 50 standard liters per minute (Richardson number of 0.3–134) through an upward-facing nozzle. In a short-term transient the helium distribution predicted with the models of Baines & Turner (1969) and Worster & Huppert (1983) matched the measured distributions reasonably well. In a long-term transient the vertical helium profile always reached a steady state which consisted of a homogenous layer at the top overlaying a stratified layer at the bottom. The helium transients in the uniform layer predicted with the models of Lowesmith (2009) and Prasad & Yang (2010) assuming a vent was located in the ceiling were in good agreement with the measured transients.
The Curious Case of the Conflicting Roles of Hydrogen in Global Energy Scenarios
Oct 2019
Publication
As energy systems transition from fossil-based to low-carbon they face many challenges particularly concerning energy security and flexibility. Hydrogen may help to overcome these challenges with potential as a transport fuel for heating energy storage conversion to electricity and in industry. Despite these opportunities hydrogen has historically had a limited role in influential global energy scenarios. Whilst more recent studies are beginning to include hydrogen the role it plays in different scenarios is extremely inconsistent. In this perspective paper reasons for this inconsistency are explored considering the modelling approach behind the scenario scenario design and data assumptions. We argue that energy systems are becoming increasingly complex and it is within these complexities that new technologies such as hydrogen emerge. Developing a global energy scenario that represents these complexities is challenging and in this paper we provide recommendations to help ensure that emerging technologies such as hydrogen are appropriately represented. These recommendations include: using the right modelling tools whilst knowing the limits of the model; including the right sectors and technologies; having an appropriate level of ambition; and making realistic data assumptions. Above all transparency is essential and global scenarios must do more to make available the modelling methods and data assumptions used.
Large-scale Compressed Hydrogen Storage as Part of Renewable Electricity Storage Systems
Mar 2021
Publication
Storing energy in the form of hydrogen is a promising green alternative. Thus there is a high interest to analyze the status quo of the different storage options. This paper focuses on the large-scale compressed hydrogen storage options with respect to three categories: storage vessels geological storage and other underground storage alternatives. In this study we investigated a wide variety of compressed hydrogen storage technologies discussing in fair detail their theory of operation potential and challenges. The analysis confirms that a techno-economic chain analysis is required to evaluate the viability of one storage option over another for a case by case. Some of the discussed technologies are immature; however this does not rule out these technologies; rather it portrays the research opportunities in the field and the foreseen potential of these technologies. Furthermore we see that hydrogen would have a significant role in balancing intermittent renewable electricity production.
A Panoramic Analysis of Hydrogen Utilization Systems Using an Input-output Table for Next Generation Energy Systems
Apr 2017
Publication
The objective of this study is to analyze a government proposal from a panoramic perspective concerning the economic and environmental effects associated with the construction and operation of hydrogen utilization systems by the year 2030. We focused on a marine transport system for hydrogen produced offshore hydrogen gas turbine power generation fuel cell vehicles (FCVs) and hydrogen stations as well as residential fuel cell systems (RFCs). In this study using an Input-Output Table for Next Generation Energy Systems (IONGES) we evaluated the induced output labor and CO2 emissions from the construction and operation of these hydrogen technologies using a uniform approach. This may be helpful when considering future designs for the Japanese energy system. In terms of per 1 t-H2 of hydrogen use CO2 reductions from the use of FCVs are considerably higher than the additional CO2 emissions from foreign production and transportation of hydrogen. Because new construction of a hydrogen pipeline network is not considered to be realistic RFCs is assumed to consume hydrogen generated by refining town gas. In this case the CO2 reductions from using RFCs will decline under the electricity composition estimated for 2030 on the condition of a substantial expansion of electricity generation from renewable energy sources. However under the present composition of electricity production we can expect a certain amount of CO2 reductions from using RFCs. If hydrogen is directly supplied to RFCs CO2 reductions increase substantially. Thus we can reduce a significant amount of CO2 emissions if various unused energy sources dispersed around local areas or unharnessed renewable energies such as solar and wind power can be converted into hydrogen to be supplied to FCVs and RFCs.
The Battle between Battery and Fuel Cell Powered Electric Vehicles: A BWM Approach
Oct 2017
Publication
The transition to a more sustainable personal transportation sector requires the widespread adoption of electric vehicles. However a dominant design has not yet emerged and a standards battle is being fought between battery and hydrogen fuel cell powered electric vehicles. The aim of this paper is to analyze which factors are most likely to influence the outcome of this battle thereby reducing the uncertainty in the industry regarding investment decisions in either of these technologies. We examine the relevant factors for standard dominance and apply a multi-criteria decision-making method best worst method to determine the relative importance of these factors. The results indicate that the key factors include technological superiority compatibility and brand reputation and credibility. Our findings show that battery powered electric vehicles have a greater chance of winning the standards battle. This study contributes to theory by providing further empirical evidence that the outcome of standards battles can be explained and predicted by applying factors for standard success. We conclude that technology dominance in the automotive industry is mostly driven by technological characteristics and characteristics of the format supporter.
Impact of Depth on Underground Hydrogen Storage Operations in Deep Aquifers
Mar 2024
Publication
Underground hydrogen storage in geological structures is considered appropriate for storing large amounts of hydrogen. Using the geological Konary structure in the deep saline aquifers an analysis of the influence of depth on hydrogen storage was carried out. Hydrogen injection and withdrawal modeling was performed using TOUGH2 software assuming different structure depths. Changes in the relevant parameters for the operation of an underground hydrogen storage facility including the amount of H2 injected in the initial filling period cushion gas working gas and average amount of extracted water are presented. The results showed that increasing the depth to approximately 1500 m positively affects hydrogen storage (flow rate of injected hydrogen total capacity and working gas). Below this depth the trend was reversed. The cushion gas-to-working gas ratio did not significantly change with increasing depth. Its magnitude depends on the length of the initial hydrogen filling period. An increase in the depth of hydrogen storage is associated with a greater amount of extracted water. Increasing the duration of the initial hydrogen filling period will reduce the water production but increase the cushion gas volume.
Balancing GHG Mitigation and Land-use Conflicts: Alternative Northern European Energy System Scenarios
Jan 2022
Publication
Long-term power market outlooks suggest a rapid increase in renewable energy deployment as a main solution to greenhouse gas mitigation in the Northern European energy system. However the consequential area requirement is a non-techno-economic aspect that currently is omitted by many energy system optimization models. This study applies modeling to generate alternatives (MGA) technique to the Balmorel energy system model to address spatial conflicts related to increased renewable energy deployment. The approach searches for alternative solutions that minimize land-use conflicts while meeting the low-carbon target by allowing a 1% to 15% increase in system costs compared to the least-cost solution. Two alternative objectives are defined to reflect various aspects of spatial impact. The results show that the least-cost solution requires 1.2%–3.6% of the land in the modeled countries in 2040 for onshore wind and solar PV installations. A 10% increase in costs can reduce the required land area by 58% by relying more on offshore wind. Nuclear energy may also be an option if both onshore and offshore areas are to be reduced or in a less flexible system. Both offshore wind and nuclear energy technologies are associated with higher risks and pose uncertainties in terms of reaching the climate targets in time. The changes in costs and required land areas imply significantly higher annual costs ranging from 200 to 750 kEUR/km2 to avoid land use for energy infrastructure. Overall this study confirms that the energy transition strategies prioritizing land savings from energy infrastructure are feasible but high risks and costs of averted land are involved.
A Chicken and Egg Situation: Enhancing Emergency Service Workers' Knowledge of Hydrogen
Sep 2021
Publication
This paper reports on the results of interviews conducted with 21 representatives from emergency services organisations within Australia and New Zealand. With a relative emergent industry such as future fuels a chicken and egg situation does emerge with regards to how much training needs to be in place in advance of large-scale industry development or not. These respondents were employed in a variety of roles being directly involved in research and training of emerging technologies frontline operational managers and other senior roles across the emergency services sector. Participants' responses to a series of questions were able to provide insights into the state of knowledge and training requirements within their organisations in relation to hydrogen and other future fuels. The findings suggest that formal and informal processes currently exist to support the knowledge development and transferal around the adoption of hydrogen and other future fuels. From the interviews it became clear that there are a number of processes that have emerged from the experiences gained through the implementation of rooftop solar PV and battery storage that provide some background context for advancing future fuels information across the sector. Because safety is a critical component for securing a social licence to operate engagement and knowledge sharing with any representatives from across this sector will only help to build confidence in the industry. Similarly because interviewees were very keen to access information they expressed a clear willingness to learn more through more formalised relationships rather than an ad hoc information seeking that has been employed to date. The presentation will identify key recommendations and also highlight the importance of QR Codes in the emergency responder landscape. Implications for industry and policy makers are discussed.
Location-dependent Effect of Nickel on Hydrogen Dissociation and Diffusion on Mg (0001) Surface: Insights into Hydrogen Storage Material Design
Apr 2021
Publication
Density functional theory (DFT) calculations have been performed to investigate the hydrogen dissociation and diffusion on Mg (0001) surface with Ni incorporating at various locations. The results show that Ni atom is preferentially located inside Mg matrix rather than in/over the topmost surface. Further calculations reveal that Ni atom locating in/over the topmost Mg (0001) surface exhibits excellent catalytic effect on hydrogen dissociation with an energy barrier of less than 0.05 eV. In these cases the rate-limiting step has been converted from hydrogen dissociation to surface diffusion. In contrast Ni doping inside Mg bulk not only does little help to hydrogen dissociation but also exhibits detrimental effect on hydrogen diffusion. Therefore it is crucial to stabilize the Ni atom on the surface or in the topmost layer of Mg (0001) surface to maintain its catalytic effect. For all the case of Ni-incorporated Mg (0001) surfaces the hydrogen atom prefers firstly immigrate along the surface and then penetrate into the bulk. It is expected that the theoretical findings in the present study could offer fundamental guidance to future designing on efficient Mg-based hydrogen storage materials.
HyUnder – Hydrogen Underground Storage at Large Scale: Case Study Spain
Aug 2015
Publication
Hydrogen as an energy carrier is understood as a system capable of storing energy for a later use in a controlled manner. Surplus electricity from renewable energy serves for green hydrogen generation via electrolysis. Once produced the hydrogen is stored for later consumption. This paper describes the Spanish Case Study of the HyUnder project which aims to evaluate the potential of underground hydrogen storage for large-scale energy storage along Europe analysing besides the Spanish Case France Germany the Netherlands Romania and the United Kingdom. This case study has considered for the assessment the competitiveness of hydrogen storage against other large scale energy storage concepts the geological potential for hydrogen storage in the region how to embed the hydrogen energy storage in the energy market and the possible business cases in four different applications: transport Power to Gas re-electrification and industry taking into account all the economic aspects such us the electrolyser OPEX and CAPEX or the cavern electricity and water costs. It is shown that the Spanish geology can provide four technical options for hydrogen underground storage. Results have shown the interest of the technology in short – medium term especially linked to certain conditions of high intermittent renewable energy penetration in the Spanish power grid that result in surplus or residual electricity. Hydrogen storage is interesting because it can integrate renewable energy systems in other sectors which do not have overcapacity and a high use of fossil fuels as the natural gas sector and the transport sector. Moreover all the economic issues have been analysed for two different horizons 2025 and 2050; concluding that the average price of electricity is the main cost. From the financial results transport application represents a business case which although in order has enough values of hydrogen demand to be stored combination of different applications must be needed in order to make sense to the development of the cavern.
Direct Conversion of CO2 to Dimethyl Ether in a Fixed Bed Membrane Reactor: Influence of Membrane Properties and Process Conditions
Jun 2021
Publication
The direct hydrogenation of CO2 to dimethyl ether (DME) is a promising technology for CO2 valorisation. In this work a 1D phenomenological reactor model is developed to evaluate and optimize the performance of a membrane reactor for this conversion otherwise limited by thermodynamic equilibrium and temperature gradients. The co-current circulation of a sweep gas stream through the permeation zone promotes both water and heat removal from the reaction zone thus increasing overall DME yield (from 44% to 64%). The membrane properties in terms of water permeability (i.e. 4·10−7 mol·Pa−1m−2s−1) and selectivity (i.e. 50 towards H2 30 towards CO2 and CO 10 towards methanol) for optimal reactor performance have been determined considering for the first time non-ideal separation and non-isothermal operation. Thus this work sheds light into suitable membrane materials for this applications. Then the non-isothermal performance of the membrane reactor was analysed as a function of the process parameters (i.e. the sweep gas to feed flow ratio the gradient of total pressure across the membrane the inlet temperature to the reaction and permeation zone and the feed composition). Owing to its ability to remove 96% of the water produced in this reaction the proposed membrane reactor outperforms a conventional packed bed for the same application (i.e. with 36% and 46% improvement in CO2 conversion and DME yield respectively). The results of this work demonstrate the potential of the membrane reactor to make the CO2 conversion to DME a feasible process.
Production of High-purity Hydrogen from Paper Recycling Black Liquor via Sorption Enhanced Steam Reforming
Jul 2020
Publication
Environmentally friendly and energy saving treatment of black liquor (BL) a massively produced waste in Kraft papermaking process still remains a big challenge. Here by adopting a Ni-CaO-Ca12Al14O33 bifunctional catalyst derived from hydrotalcite-like materials we demonstrate the feasibility of producing high-purity H2 (∼96%) with 0.9 mol H2 mol-1 C yield via the sorption enhanced steam reforming (SESR) of BL. The SESRBL performance in terms of H2 production maintained stable for 5 cycles but declined from the 6th cycle. XRD Raman spectroscopy elemental analysis and energy dispersive techniques were employed to rationalize the deactivation of the catalyst. It was revealed that gradual sintering and agglomeration of Ni and CaO and associated coking played important roles in catalyst deactivation and performance degradation of SESRBL while deposition of Na and K from the BL might also be responsible for the declined performance. On the other hand it was demonstrated that the SESRBL process could effectively reduce the emission of sulfur species by storing it as CaSO3. Our results highlight a promising alternative for BL treatment and H2 production thereby being beneficial for pollution control and environment governance in the context of mitigation of climate change.
Analysis of Hydrogen Production Potential from Waste Plastics by Pyrolysis and In Line Oxidative Steam Reforming
Oct 2021
Publication
A study was carried out on the valorization of different waste plastics (HDPE PP PS and PE) their mixtures and biomass/HDPE mixtures by means of pyrolysis and in line oxidative steam reforming. A thermodynamic equilibrium simulation was used for determining steam reforming data whereas previous experimental results were considered for setting the pyrolysis volatile stream composition. The adequacy of this simulation tool was validated using experimental results obtained in the pyrolysis and in line steam reforming of different plastics. The effect the most relevant process conditions i.e. temperature steam/plastic ratio and equivalence ratio have on H2 production and reaction enthalpy was evaluated. Moreover the most suitable conditions for the oxidative steam reforming of plastics of different nature and their mixtures were determined. The results obtained are evidence of the potential interest of this novel valorization route as H2 productions of up to 25 wt% were obtained operating under autothermal conditions.
Experimental Characterization of an Alkaline Electrolyser and a Compression System for Hydrogen Production and Storage
Aug 2021
Publication
Storing renewable energy in chemicals like hydrogen can bring various benefits like high energy density seasonal storability possible cost reduction of the final product and the potential to let renewable power penetrate other markets and to overcome their intermittent availability. In the last year’s production of this gas from renewable energy sources via electrolysis has grown its reputation as one feasible solution to satisfy future zero-emission energy demand. To extend the exploitation of Renewable Energy Source (RES) small-scale conversion plants seem to be an interesting option. In view of a possible widespread adoption of these types of plants the authors intend to present the experimental characterization of a small-scale hydrogen production and storage plant. The considered experimental plant is based on an alkaline electrolyser and an air-driven hydrogen compression and storage system. The results show that the hydrogen production-specific consumption is on average 77 kWh/kgH2 . The hydrogen compressor energy requirement is on average 15 kWh/kgH2 (data referred to the driving compressed air). The value is higher than data found in literature (4.4–9.3 kWh/kgH2 ) but the difference can be attributed to the small size of the considered compressor and the choice to limit the compression stages.
Small-Scaled Production of Blue Hydrogen with Reduced Carbon Footprint
Aug 2021
Publication
This article reviews a method of hydrogen production based on partial non-catalytic oxidation of natural gas in an original synthesis gas generator. The working principles of the unit are similar to those of liquid-propellant rocket engines. This paper presents a description of the operation and technical characteristics of the synthesis gas generator. Its application in the creation of small-scaled plants with a capacity of up to 5–7 thousand m3/h of hydrogen is justified. Hydrogen production in the developed installation requires a two-stage method and includes a technological unit for producing a hydrogen-containing gas. Typical balance compositions of hydrogen-containing gas at the synthesis gas generator’s outlet are given. To increase the hydrogen concentration it is proposed to carry out a two-stage steam catalytic conversion of carbon monoxide contained in the hydrogen-containing gas at the synthesis gas generator’s outlet using a single Cu–Zn–cementcontaining composition. Based on thermodynamic calculations quasi-optimal modes of natural gas partial oxidation with oxygen are formulated and the results of material balance calculation for the installation are presented. In order to produce “blue” hydrogen the scheme of carbon dioxide separation and liquefaction is developed. The conclusion section of the paper contains the test results of a pilot demonstration unit and the recommendations for improving the technology and preventing soot formation.
Effect of Supercharging on Improving Thermal Efficiency and Modifying Combustion Characteristics in Lean-burn Direct-injection Near-zero-emission Hydrogen Engines
Oct 2021
Publication
The authors have proposed a new combustion process called the Plume Ignition Combustion Concept (PCC) in which with an optimal combination of hydrogen injection timing and controlled jet geometry the plume of the hydrogen jet is spark-ignited to accomplish combustion of a rich mixture. This combustion process markedly improves thermal efficiency by reducing cooling loss which is essential for increasing thermal efficiency in a hydrogen engine while maintaining high power. In order to improve thermal efficiency and reduce NOx formation further PCC was applied to a lean-burn regime to burn a leaner mixture globally. In this study the effect of supercharging which was applied to recover the reduced output power due to the leaner mixture on improving thermal efficiency was confirmed along with clarifying the cause.
Hydrogen Storage in Pure and Boron-Substituted Nanoporous Carbons—Numerical and Experimental Perspective
Aug 2021
Publication
Nanoporous carbons remain the most promising candidates for effective hydrogen storage by physisorption in currently foreseen hydrogen-based scenarios of the world’s energy future. An optimal sorbent meeting the current technological requirement has not been developed yet. Here we first review the storage limitations of currently available nanoporous carbons then we discuss possible ways to improve their storage performance. We focus on two fundamental parameters determining the storage (the surface accessible for adsorption and hydrogen adsorption energy). We define numerically the values nanoporous carbons have to show to satisfy mobile application requirements at pressures lower than 120 bar. Possible necessary modifications of the topology and chemical compositions of carbon nanostructures are proposed and discussed. We indicate that pore wall fragmentation (nano-size graphene scaffolds) is a partial solution only and chemical modifications of the carbon pore walls are required. The positive effects (and their limits) of the carbon substitutions by B and Be atoms are described. The experimental ‘proof of concept’ of the proposed strategies is also presented. We show that boron substituted nanoporous carbons prepared by a simple arc-discharge technique show a hydrogen adsorption energy twice as high as their pure carbon analogs. These preliminary results justify the continuation of the joint experimental and numerical research effort in this field.
Graphene Oxide/metal Nanocrystal Multilaminates as the Atomic Limit for Safe and Selective Hydrogen Storage
Mar 2016
Publication
Interest in hydrogen fuel is growing for automotive applications; however safe dense solid-state hydrogen storage remains a formidable scientific challenge. Metal hydrides offer ample storage capacity and do not require cryogens or exceedingly high pressures for operation. However hydrides have largely been abandoned because of oxidative instability and sluggish kinetics. We report a new environmentally stable hydrogen storage material constructed of Mg nanocrystals encapsulated by atomically thin and gas-selective reduced graphene oxide (rGO) sheets. This material protected from oxygen and moisture by the rGO layers exhibits exceptionally dense hydrogen storage (6.5 wt% and 0.105 kg H2 per litre in the total composite). As rGO is atomically thin this approach minimizes inactive mass in the composite while also providing a kinetic enhancement to hydrogen sorption performance. These multilaminates of rGO-Mg are able to deliver exceptionally dense hydrogen storage and provide a material platform for harnessing the attributes of sensitive nanomaterials in demanding environments.
Tetrahydroborates: Development and Potential as Hydrogen Storage Medium
Oct 2017
Publication
The use of fossil fuels as an energy supply becomes increasingly problematic from the point of view of both environmental emissions and energy sustainability. As an alternative hydrogen is widely regarded as a key element for a potential energy solution. However differently from fossil fuels such as oil gas and coal the production of hydrogen requires energy. Alternative and intermittent renewable energy sources such as solar power wind power etc. present multiple advantages for the production of hydrogen. On the one hand the renewable sources contribute to a remarkable reduction of pollutants released to the air and on the other hand they significantly enhance the sustainability of energy supply. In addition the storage of energy in form of hydrogen has a huge potential to balance an effective and synergetic utilization of renewable energy sources. In this regard hydrogen storage technology is a key technology towards the practical application of hydrogen as “energy carrier”. Among the methods available to store hydrogen solid-state storage is the most attractive alternative from both the safety and the volumetric energy density points of view. Because of their appealing hydrogen content complex hydrides and complex hydride-based systems have attracted considerable attention as potential energy vectors for mobile and stationary applications. In this review the progresses made over the last century on the synthesis and development of tetrahydroborates and tetrahydroborate-based systems for hydrogen storage purposes are summarized.
Study of Hydrogen Enriched Premixed Flames
Sep 2005
Publication
In the present paper the theoretical study of the un-stretched laminar premixed flames of hydrogen-methane mixtures is carried out by using the detailed reaction mechanism GRI-Mech 3.0 implemented in the CHEMKIN software to find out the effect of hydrogen addition on the hybrid fuel burning velocity. The model results show that the laminar burning velocity of the hydrogen-methane mixtures is not the linear regression of those of the pure fuels since it results substantially less than the proportional averaging of the values for the fuel constituents. Moreover the effect of hydrogen addition in terms of enhancement of the mixture laminar burning velocity with respect to the methane is relevant only at very high values of the hydrogen content in the hybrid mixtures (> 70 % mol.). The performed sensitivity analysis shows that these results can be attributed to kinetics and in particular to the concentration of H radicals: depending on the hydrogen content in the fuels mixture the production of the H radicals can affect the limiting reaction step for methane combustion. Two regimes are identified in the hydrogen-methane combustion. The first regime is controlled by the methane reactivity the hydrogen being not able to significantly affect the laminar burning velocity (< 70 % mol.). In the second regime the hydrogen combustion has a relevant role as its high content in the hybrid fuel leads to a significant H radicals pool thus enhancing the reaction rate of the more slowly combusting methane.
Healthy Power: Reimagining Hospitals as Sustainable Energy Hubs
Oct 2020
Publication
Human health is a key pillar of modern conceptions of sustainability. Humanity pays a considerable price for its dependence on fossil-fueled energy systems which must be addressed for sustainable urban development. Public hospitals are focal points for communities and have an opportunity to lead the transition to renewable energy. We have reimagined the healthcare energy ecosystem with sustainable technologies to transform hospitals into networked clean energy hubs. In this concept design hydrogen is used to couple energy with other on-site medical resource demands and vanadium flow battery technology is used to engage the public with energy systems. This multi-generation system would reduce harmful emissions while providing reliable services tackling the linked issues of human and environmental health.
HyDeploy Report: Keele Information
Jun 2018
Publication
Keele University was chosen as the site for the HyDeploy project as it was seen as the site offered a high degree of control regarding safety functions high availability of operational data and minimal supply chain interfaces given that Keele University is the supplier transporter and distributer of natural gas at the site. The site was offered to the project as a living laboratory in line with the university's ambition to be at the forefront of energy innovation through the Smart Energy Network Demonstrator (SEND). Evidenced within this report is the supporting data that confirms the rationale for selecting Keele University and the necessary data to profile the section of the gas network which hydrogen will be injected into. The gas network at Keele University is segregated via the governor stations which regulate pressure within the network. The section of network which has been chosen for the HyDeploy project is the G3 network which is regulated by the G3 governor.
Evaluation of Hydrogen-induced Cracking in High-strength Steel Welded Joints by Acoustic Emission Technique
Feb 2020
Publication
Hydrogen-induced cracking behavior in high-strength steel mainly composed of martensite was analyzed by acoustic emission (AE) technique and finite element method (FEM) in slow strain-rate tensile (SSRT) tests and welding tests. The crack initiation was detected by the AE signals and the time evolution of stress concentration and hydrogen diffusion were calculated by FEM. The effect of hardness and plastic strain on the hydrogen diffusion coefficientwas explicitly introduced into the governing equation in FEM. The criterion and indicator parameter for the crack initiation were derived as a function of maximum principal stress and locally accumulated hydrogen concentration. The results showed that the cracking criterion derived by AE and FEM is useful for predicting the cold cracking behavior and determining the critical preheat temperature to prevent hydrogeninduced cracking.
An Optimal Fuzzy Logic-Based Energy Management Strategy for a Fuel Cell/Battery Hybrid Power Unmanned Aerial Vehicle
Feb 2022
Publication
With the development of high-altitude and long-endurance unmanned aerial vehicles (UAVs) optimization of the coordinated energy dispatch of UAVs’ energy management systems has become a key target in the research of electric UAVs. Several different energy management strategies are proposed herein for improving the overall efficiency and fuel economy of fuel cell/battery hybrid electric power systems (HEPS) of UAVs. A rule-based (RB) energy management strategy is designed as a baseline for comparison with other strategies. An energy management strategy (EMS) based on fuzzy logic (FL) for HEPS is presented. Compared with classical rule-based strategies the fuzzy logic control has better robustness to power fluctuations in the UAV. However the proposed FL strategy has an inherent defect: the optimization performances will be determined by the heuristic method and the past experiences of designers to a great extent rather than a specific cost function of the algorithm itself. Thus the paper puts forward an improved fuzzy logic-based strategy that uses particle swarm optimization (PSO) to track the optimal thresholds of membership functions and the equivalent hydrogen consumption minimization is considered as the objective function. Using a typical 30 min UAV mission profile all the proposed EMS were verified by simulations and rapid controller prototype (RCP) experiments. Comprehensive comparisons and analysis are presented by evaluating hydrogen consumption system efficiency and voltage bus stability. The results show that the PSO-FL algorithm can further improve fuel economy and achieve superior overall dynamic performance when controlling a UAV’s fuel-cell powertrain.
Electrolyzers Enhancing Flexibility in Electric Grids
Nov 2017
Publication
This paper presents a real-time simulation with a hardware-in-the-loop (HIL)-based approach for verifying the performance of electrolyzer systems in providing grid support. Hydrogen refueling stations may use electrolyzer systems to generate hydrogen and are proposed to have the potential of becoming smarter loads that can proactively provide grid services. On the basis of experimental findings electrolyzer systems with balance of plant are observed to have a high level of controllability and hence can add flexibility to the grid from the demand side. A generic front end controller (FEC) is proposed which enables an optimal operation of the load on the basis of market and grid conditions. This controller has been simulated and tested in a real-time environment with electrolyzer hardware for a performance assessment. It can optimize the operation of electrolyzer systems on the basis of the information collected by a communication module. Real-time simulation tests are performed to verify the performance of the FEC-driven electrolyzers to provide grid support that enables flexibility greater economic revenue and grid support for hydrogen producers under dynamic conditions. The FEC proposed in this paper is tested with electrolyzers however it is proposed as a generic control topology that is applicable to any load.
Critical Materials for Water Electrolysers at the Example of the Energy Transition in Germany
Feb 2021
Publication
The present work aims to identify critical materials in water electrolysers with potential future supply constraints. The expected rise in demand for green hydrogen as well as the respective implications on material availability are assessed by conducting a case study for Germany. Furthermore the recycling of end‐of‐life (EoL) electrolysers is evaluated concerning its potential in ensuring the sustainable supply of the considered materials. As critical materials bear the risk of raising production costs of electrolysers substantially this article examines the readiness of this technology for industrialisation from a material perspective. Except for titanium the indicators for each assessed material are scored with a moderate to high (platinum) or mostly high (iridium scandium and yttrium) supply risk. Hence the availability of these materials bears the risk of hampering the scale‐up of electrolysis capacity. Although conventional recycling pathways for platinum iridium and titanium already exist secondary material from EoL electrolysers will not reduce the dependence on primary resources significantly within the period under consideration—from 2020 until 2050. Notably the materials identified as critical are used in PEM and high temperature electrolysis whereas materials in alkaline electrolysis are not exposed to significant supply risks.
Assessment of an Innovative Way to Store Hydrogen in Vehicles
May 2019
Publication
The use of hydrogen as an alternative to fossil fuels for vehicle propulsion is already a reality. However due to its physical characteristics storage is still a challenge. There is an innovative way presented in this study to store hydrogen in conventional vehicles propelled by spark-ignition reciprocating engines and fuel cells using hydrogen as fuel; the storage of hydrogen will be at high pressure within small spheres randomly packed in a tank like the conventional tank of fuel used nowadays in current vehicles. Therefore the main purpose of the present study is to assess the performance of this storage system and compare it to others already applied by car manufacturers in their cars. In order to evaluate the performance of this storage system some parameters were taken into account: The energy stored by volume and stored by weight hydrogen leakage and compliance with current standards. This system is safer than conventional storage systems since hydrogen is stored inside small spheres containing small amounts of hydrogen. Besides its gravimetric energy density (GED) is threefold and the volumetric energy density (VED) is about half when compared with homologous values for conventional systems and both exceed the targets set by the U.S. Department of Energy. Regarding the leakage of hydrogen it complies with the European Standards provided a suitable choice of materials and dimensions is made.
Effect of the Strain Rate on the Fracture Behaviour of High Pressure Pre-Charged Samples
Dec 2018
Publication
The aim of this work is to study the effect of the displacement rate on the hydrogen embrittlement of two different structural steels grades used in energetic applications. With this purpose samples were pre-charged with gaseous hydrogen at 19.5 MPa and 450 °C for 21 h. Then fracture tests of the pre-charged specimens were performed using different displacement rates. It is showed that the lower is the displacement rate and the largest is the steel strength the strongest is the reduction of the fracture toughness due to the presence of internal hydrogen.
The Challenges of Integrating the Principles of Green Chemistry and Green Engineering to Heterogeneous Photocatalysis to Treat Water and Produce Green H2
Jan 2023
Publication
Nowadays heterogeneous photocatalysis for water treatment and hydrogen production are topics gaining interest for scientists and developers from different areas such as environmental technology and material science. Most of the efforts and resources are devoted to the development of new photocatalyst materials while the modeling and development of reaction systems allowing for upscaling the process to pilot or industrial scale are scarce. In this work we present what is known on the upscaling of heterogeneous photocatalysis to purify water and to produce green H2. The types of reactors successfully used in water treatment plants are presented as study cases. The challenges of upscaling the photocatalysis process to produce green H2 are explored from the perspectives of (a) the adaptation of photoreactors (b) the competitiveness of the process and (c) safety. Throughout the text Green Chemistry and Engineering Principles are described and discussed on how they are currently being applied to the heterogeneous photocatalysis process along with the challenges that are ahead. Lastly the role of automation and high-throughput methods in the upscaling following the Green Principles is discussed.
Mobility from Renewable Electricity: Infrastructure Comparison for Battery and Hydrogen Fuel Cell Vehicles
May 2018
Publication
This work presents a detailed breakdown of the energy conversion chains from intermittent electricity to a vehicle considering battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs). The traditional well-to-wheel analysis is adapted to a grid to mobility approach by introducing the intermediate steps of useful electricity energy carrier and on-board storage. Specific attention is given to an effective coupling with renewable electricity sources and associated storage needs. Actual market data show that compared to FCEVs BEVs and their infrastructure are twice as efficient in the conversion of renewable electricity to a mobility service. A much larger difference between BEVs and FCEVs is usually reported in the literature. Focusing on recharging events this work additionally shows that the infrastructure efficiencies of both electric vehicle (EV) types are very close with 57% from grid to on-board storage for hydrogen refilling stations and 66% for fast chargers coupled with battery storage. The transfer from the energy carrier at the station to on-board storage in the vehicle accounts for 9% and 12% of the total energy losses of these two modes respectively. Slow charging modes can achieve a charging infrastructure efficiency of 78% with residential energy storage systems coupled with AC chargers.
Molecular Dynamics Studies of Hydrogen Effect on Intergranular Fracture in α-Iron
Nov 2020
Publication
In the current study the effect of hydrogen atoms on the intergranular failure of α-iron is examined by a molecular dynamics (MD) simulation. The effect of hydrogen embrittlement on the grain boundary (GB) is investigated by diffusing hydrogen atoms into the grain boundaries using a bicrystal body-centered cubic (BCC) model and then deforming the model with a uniaxial tension. The Debye Waller factors are applied to illustrate the volume change of GBs and the simulation results suggest that the trapped hydrogen atoms in GBs can therefore increase the excess volume of GBs thus enhancing intergranular failure. When a constant displacement loading is applied to the bicrystal model the increased strain energy can barely be released via dislocation emission when H is present. The hydrogen pinning effect occurs in the current dislocation slip system <111>{112}. The hydrogen atoms facilitate cracking via a decrease of the free surface energy and enhance the phase transition via an increase in the local pressure. Hence the failure mechanism is prone to intergranular failure so as to release excessive pressure and energy near GBs. This study provides a mechanistic framework of intergranular failure and a theoretical model is then developed to predict the intergranular cracking rate
Modeling of Thermal Performance of a Commercial Alkaline Electrolyzer Supplied with Various Electrical Currents
Nov 2021
Publication
Hydrogen produced by solar and other clean energy sources is an essential alternative to fossil fuels. In this study a commercial alkaline electrolyzer with different cell numbers and electrode areas are simulated for different pressure temperature thermal resistance and electrical current. This alkaline electrolyzer is considered unsteady in simulations and different parameters such as temperature are obtained in terms of time. The obtained results are compared with similar results in the literature and good agreement is observed. Various characteristics of this alkaline electrolyzer as thermoneutral voltage faraday efficiency and cell voltage are calculated and displayed. The outlet heat rate and generated heat rate are obtained as well. The pressure and the temperature in the simulations are between 1 and 100 bar and between 300 and 360 Kelvin respectively. The results show that the equilibrium temperature is reached 2-3 hours after the time when the Alkaline electrolyzer starts to work.
Flare Gas Monetization and Greener Hydrogen Production via Combination with Crypto Currency Mining and Carbon Dioxide Capture
Jan 2022
Publication
In view of the continuous debates on the environmental impact of blockchain technologies in particular crypto currency mining accompanied by severe carbon dioxide emissions a technical solution has been considered assuming direct monetization of associated petroleum gas currently being flared. The proposed approach is based on the technology of low-temperature steam reforming of hydrocarbons which allows flare gas conditioning towards the requirements for fuel for gas piston and gas turbine power plants. The generation of electricity directly at the oil field and its use for on-site crypto currency mining transforms the process of wasteful flaring of valuable hydrocarbons into an economically attractive integrated processing of natural resources. The process is not carbon neutral and is not intended to compete zero-emission technologies but its combination with technologies for carbon dioxide capture and re-injection into the oil reservoir can both enhance the oil recovery and reduce carbon dioxide emissions into the atmosphere. The produced gas can be used for local transport needs while the generated heat and electricity can be utilized for on-site food production and biological carbon dioxide capture in vertical greenhouse farms. The suggested approach allows significant decrease in the carbon dioxide emissions at oil fields and although it may seem paradoxically on-site cryptocurrency mining actually may lead to a decrease in the carbon footprint. The amount of captured CO2 could be transformed into CO2 emission quotas which can be spent for the production of virtually “blue” hydrogen by steam reforming of natural gas in locations where the CO2 capture is technically impossible and/or unprofitable.
Road Map to a US Hydrogen Energy: Reducing Emissions and Driving Growth Across the Nation
Oct 2020
Publication
This US Hydrogen Road Map was created through the collaboration of executives and technical industry experts in hydrogen across a broad range of applications and sectors who are committed to improving the understanding of hydrogen and how to increase its adoption across many sectors of the economy. For the first time this coalition of industry leaders has convened to develop a targeted holistic approach for expanding the use of hydrogen as an energy carrier. Due to great variation among national and state policies infrastructure needs and community interests each state and region of the US will likely have its own specific policies and road maps for implementing hydrogen infrastructure. The West Coast for example has traditionally had progressive policies on reducing transportation emissions so it is likely that hydrogen will scale sooner for vehicles in this region especially California. Experts also acknowledge the role that hydrogen in combination with renewables can play in supplying microgrid-type power to communities with the highest risk of shut-offs during seasonal weather-related issues such as high temperatures or wildfire-related power interruptions. Some states have emphasized the need to decarbonize the gas grid so blending hydrogen in natural gas networks and using hydrogen as feedstock may advance more quickly in these regions. Other states are interested in hydrogen as a means to address power grid issues enable the deployment of renewables and support competitive nuclear power. The launch of hydrogen technologies in some states or regions will help to scale hydrogen in various applications across the country laying the foundation for energy security grid resiliency economic growth and the reduction of both greenhouse gas (GHG) emissions and air pollutants. This report outlines the benefits and impact of fuel cell technologies and hydrogen as a viable solution to the energy challenges facing the US through 2030 and beyond. As such it can serve as the latest comprehensive industry-driven national road map to accelerate and scale up hydrogen in the economy across North America
The Potential of Green Ammonia Production to Reduce Renewable Power Curtailment and Encourage the Energy Transition in China
Apr 2022
Publication
The pursuing of inter-regional power transmission to address renewable power curtailment in China has resulted in disappointing gains. This paper evaluates the case of local green ammonia production to address this issue. An improved optimization-based simulation model is applied to simulate lifetime green manufacturing and the impacts of main institutional incentives and oxygen synergy on investment are analysed. Levelized cost of ammonia is estimated at around 820 USD/t which is about twice the present price. The operating rate ammonia price the electrical efficiency of electrolysers and the electricity price are found to be the key factors in green ammonia investment. Carbon pricing and value-added tax exemption exert obvious influences on the energy transition in China. A subsidy of approximately 450 USD/t will be required according to the present price; however this can be reduced by 100 USD/t through oxygen synergy. Compared to inter-regional power transmission green ammonia production shows both economic and environmental advantages. Therefore we propose an appropriate combination of both options to address renewable power curtailment and the integration of oxygen manufacturing into hydrogen production. We consider the findings and policy implications will contribute to addressing renewable power curtailment and boosting the hydrogen economy in China.
Laser Induced Hydrogen Emission from Ethanol with Dispersed Graphene Particles
Apr 2021
Publication
Efficient hydrogen emission from ethanol with disperse graphene foam particles by using a continuous wave infrared laser diode is reported. The products of ethanol dissociation - hydrogen methane and carbon oxide were measured using mass spectrometry. It was found that the most efficient generation of hydrogen was observed when graphene particles were irradiated by a focused laser beam proceeded at the surface of ethanol solution. The process was assisted by intense white light emission resulting from the laser induced multiphoton ionization of graphene combined with the simultaneous emission of hot electrons. The hot electron emission enables the efficient dissociation of ethanol molecules located close to the solution surface with graphene foam particles.
Vented Hydrogen-air Explosion in a Small Obstructed Rectangular Container- effect of the Blockage Ratio
Sep 2019
Publication
The explosion venting is an effective way to reduce hydrogen-air explosion hazards but the explosion venting has been hardly touched in an obstructed container. Current experiments focused on the effects of different blockage ratios on the explosion venting in a small obstructed rectangular container. Experimental results show that three overpressure peaks are formed in the case with the obstacle while only two can be observed in the case of no obstacle. The obstacle blockage ratio has a significant influence on the peak overpressure induced by the obstacle-acoustic interactions but it has an ignorable effect on the peak overpressure caused by the rupture of the vent film. The obstacle-induced overpressure peak first increases and then decreases with the increase of the blockage ratio. In addition all overpressure peaks inside the container decreases with the increase of the vent area and its appearance time is relatively earlier for larger vent area.
Development of a Flashback Correlation for Burner-stabilized Hydrogen-air Premixed Flames
Feb 2022
Publication
With a growing need for replacing fossil fuels with cleaner alternatives hydrogen has emerged as a viable candidate for providing heat and power. However stable and safe combustion of hydrogen is not simple and as such a number of key issues have been identified that need to be understood for a safe design of combustion chambers. One such issue is the higher propensity of hydrogen flames to flashback compared to that for methane flames. The flashback problem is coupled with higher burner temperatures that could cause strong thermal stresses in burners and could hinder their performance. In order to systematically investigate flashback in premixed hydrogen-air flames for finding a global flashback criteria in this study we use numerical simulations as a basic tool to study flashback limits of slit burners. Flashback limits are found for varying geometrical parameters and equivalence ratios and the sensitivity of each parameter on the flashback limit and burner temperatures are identified and analyzed. It is shown that the conventional flashback correlation with critical velocity gradient does not collapse the flashback data as it does not take into account stretch induced preferential diffusion effects. A new Karlovitz number definition is introduced with physical insights that collapses the flashback data at all tested conditions in an excellent manner.
The Use of Metal Hydrides in Fuel Cell Applications
Feb 2017
Publication
This paper reviews state-of-the-art developments in hydrogen energy systems which integrate fuel cells with metal hydride-based hydrogen storage. The 187 reference papers included in this review provide an overview of all major publications in the field as well as recent work by several of the authors of the review. The review contains four parts. The first part gives an overview of the existing types of fuel cells and outlines the potential of using metal hydride stores as a source of hydrogen fuel. The second part of the review considers the suitability and optimisation of different metal hydrides based on their energy efficient thermal integration with fuel cells. The performances of metal hydrides are considered from the viewpoint of the reversible heat driven interaction of the metal hydrides with gaseous H2. Efficiencies of hydrogen and heat exchange in hydrogen stores to control H2 charge/discharge flow rates are the focus of the third section of the review and are considered together with metal hydride – fuel cell system integration issues and the corresponding engineering solutions. Finally the last section of the review describes specific hydrogen-fuelled systems presented in the available reference data.
Hydrogen—An Alternative Fuel for Automotive Diesel Engines Used in Transportation
Nov 2020
Publication
Considering the current environmental restrictions particularly those imposed on fossil fuel exploitation hydrogen stands out as a very promising alternative for the power and transportation sectors. This paper investigates the effects of the employment of hydrogen in a K9K automotive diesel engine. Experiments were conducted at a speed of 2000 min−1 with various engine load levels of 40% 55% 70% and 85%; several quantities were monitored to evaluate the performance with hydrogen use in terms of brake-specific energetic consumption (BSEC) fuel economy maximum pressure and heat-release characteristics. It was found that at 55% engine load the engine efficiency increased by 5.3% with hydrogen addition achieving a diesel fuel economy of 1.32 kg/h. The rate of increase of the peak pressure and maximum pressure started to increase as a consequence of the higher fuel quantity that burned in the premixed combustion phase while still remaining within reliable operational limits. The accelerated combustion and augmented heat release rate resulted in a combustion duration that was reduced by 3◦ CA (crank angle degree) achieving a mass fraction burned percentage of 10% to 90% earlier in the cycle and the combustion variability was also influenced. Hydrogen use assured the decrease of CO2 HC NOx and smoke emission levels in comparison with classic fueling.
Investment Frameworks for Development of CCUS in the UK
Jul 2019
Publication
The CCUS Advisory Group (CAG) established in March 2019 is an industry-led group considering the critical challenges facing the development of CCUS market frameworks and providing insight into potential solutions. The CAG brings together experts from across the CCUS industry finance and legal sectors.<br/>The CAG has examined a range of business models focusing on industrial CCUS power production CO? transport and storage and hydrogen production. It has considered how the proposed business models interact in order to minimise issues such as cross-chain risk and has considered issues such as delivery capability. The conclusions of the CAG can be found in this report.
HyDeploy Project - First Project Progress Report
Dec 2017
Publication
The HyDeploy Project seeks to address a key issue for UK customers: how to reduce the carbon they emit in heating their homes. The UK has a world class gas grid delivering heat conveniently and safely to over 83% of homes. Emissions could be reduced by lowering the carbon content of gas through blending with hydrogen. Compared with solutions such as heat pumps this means that customers would not need disruptive and expensive changes in their homes. This Network Innovation Competition (NIC) funded project seeks to establish the level of hydrogen that can be safely blended with natural gas for transport and use in a UK network.
Under its Smart Energy Network Demonstration innovation programme Keele University is establishing its electricity and gas networks as facilities to drive forward innovation in the energy sector. The objective of HyDeploy is to trial natural gas blended with potentially up to 20% volume of hydrogen in a part of the Keele gas network. Before any hydrogen can be blended with natural gas in the network the percentage of hydrogen to be delivered must be approved by the Health and Safety Executive (HSE). It must be satisfied that the approved blended gas will be as safe to use as normal gas. Any approval will be given as an exemption to the Gas Safety (Management) Regulations. These regulations ensure the safe use and management of gas through the gas network in the UK. The evidence presented to the HSE comprises critically appraised literature combined with the results from a specifically commissioned experimental and testing programme. Based on engagement with all local customers this includes detailed safety checks on the network appliances and installations at Keele. Subject to approval by the HSE the hydrogen production and grid injection units will be installed and an extensive trial programme of blending will be undertaken. If hydrogen were blended at 20% volume with natural gas across the UK it would save around 6 million tonnes of carbon dioxide emissions every year the equivalent of taking 2.5 million cars off the road.
This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.
Under its Smart Energy Network Demonstration innovation programme Keele University is establishing its electricity and gas networks as facilities to drive forward innovation in the energy sector. The objective of HyDeploy is to trial natural gas blended with potentially up to 20% volume of hydrogen in a part of the Keele gas network. Before any hydrogen can be blended with natural gas in the network the percentage of hydrogen to be delivered must be approved by the Health and Safety Executive (HSE). It must be satisfied that the approved blended gas will be as safe to use as normal gas. Any approval will be given as an exemption to the Gas Safety (Management) Regulations. These regulations ensure the safe use and management of gas through the gas network in the UK. The evidence presented to the HSE comprises critically appraised literature combined with the results from a specifically commissioned experimental and testing programme. Based on engagement with all local customers this includes detailed safety checks on the network appliances and installations at Keele. Subject to approval by the HSE the hydrogen production and grid injection units will be installed and an extensive trial programme of blending will be undertaken. If hydrogen were blended at 20% volume with natural gas across the UK it would save around 6 million tonnes of carbon dioxide emissions every year the equivalent of taking 2.5 million cars off the road.
This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.
Hydrogen Storage: Thermodynamic Analysis of Alkyl-Quinolines and Alkyl-Pyridines as Potential Liquid Organic Hydrogen Carriers (LOHC)
Dec 2021
Publication
The liquid organic hydrogen carriers (LOHC) are aromatic molecules which can be considered as an attractive option for the storage and transport of hydrogen. A considerable amount of hydrogen up to 7–8% wt. can be loaded and unloaded with a reversible chemical reaction. Substituted quinolines and pyridines are available from petroleum coal processing and wood preservation or they can be synthesized from aniline. Quinolines and pyridines can be considered as potential LOHC systems provided they have favorable thermodynamic properties which were the focus of this current study. The absolute vapor pressures of methyl-quinolines were measured using the transpiration method. The standard molar enthalpies of vaporization of alkyl-substituted quinolines and pyridines were derived from the vapor pressure temperature dependencies. Thermodynamic data on vaporization and formation enthalpies available in the literature were collected evaluated and combined with our own experimental results. The theoretical standard molar gas-phase enthalpies of formation of quinolines and pyridines calculated using the quantum-chemical G4 methods agreed well with the evaluated experimental data. Reliable standard molar enthalpies of formation in the liquid phase were derived by combining high-level quantum chemistry values of gas-phase enthalpies of formation with experimentally determined enthalpies of vaporization. The liquid-phase hydrogenation/dehydrogenation reaction enthalpies of alkyl-substituted pyridines and quinolines were calculated and compared with the data for other potential liquid organic hydrogen carriers. The comparatively low enthalpies of reaction make these heteroaromatics a seminal LOHC system.
Hydrogen Safety Aspects Related to High Pressure - PEM Water Electrolysis
Sep 2007
Publication
Polymer electrolyte membrane (PEM) water electrolysis has demonstrated its potentialities in terms of cell efficiency (energy consumption ≈ 4.0-4.2 kW/Nm3 H2) and gas purity (> 99.99% H2). Current research activities are aimed at increasing operating pressure up to several hundred bars for direct storage of hydrogen in pressurized vessels. Compared to atmospheric pressure electrolysis high-pressure operation yields additional problems especially with regard to safety considerations. In particular the rate of gases (H2 and O2) cross-permeation across the membrane and their water solubility both increase with pressure. As a result gas purity is affected in both anodic and cathodic circuits and this can lead to the formation of explosive gas mixtures. To prevent such risks two different solutions reported in this communication have been investigated. First the chemical modification of the solid polymer electrolyte in order to reduce cross-permeation phenomena. Second the use of catalytic H2/O2 recombiners to maintain H2 levels in O2 and O2 levels in H2 at values compatible with safety requirements.
Simulation Analysis on the Risk of Hydrogen Releases and Combustion in Subsea Tunnels
Oct 2015
Publication
Hydrogen is considered to be a very promising potential energy carrier due to its excellent characteristics such as abundant resources high fuel value clean and renewable. Its safety features greatly influence the potential use. Several safety problems need to be analyzed before using in transportation industry. With the development of the tunnel transportation technology the safe use of hydrogen in tunnels will receive a lot of research attentions. In this article the risk associated with hydrogen release from onboard high-pressure vessels and the induced combustion in tunnels was analyzed using the Partially Averaged Navier–Stokes (PANS) turbulence model. The influences of the tunnel ventilation facilities on the hydrogen flow characteristics and the flammable hydrogen cloud sizes were studied. The tunnel layouts were designed according to the subsea tunnel. And a range of longitudinal ventilation conditions had been considered to investigate the hydrogen releases and the sizes of the flammable hydrogen cloud. Then the hydrogen combustion simulation was carried out after the fixed leaking time. The overpressures induced after the ignition of leaking hydrogen were studied. The influences of ventilation and ignition delay time on the overpressure were also investigated. The main aim was to research the phenomena of hydrogen releases and combustion risk inside subsea tunnels and to lay the foundation of risk assessment methodology developed for hydrogen energy applications on transportation.
Measurement Challenges for Hydrogen Vehicles
Apr 2019
Publication
Uptake of hydrogen vehicles is an ideal solution for countries that face challenging targets for carbon dioxide reduction. The advantage of hydrogen fuel cell electric vehicles is that they behave in a very similar way to petrol engines yet they do not emit any carbon containing products during operation. The hydrogen industry currently faces the dilemma that they must meet certain measurement requirements (set by European legislation) but cannot do so due to a lack of available methods and standards. This paper outlines the four biggest measurement challenges that are faced by the hydrogen industry including flow metering quality assurance quality control and sampling.
A Barrier Analysis of a Generic Hydrogen Refuelling Station
Sep 2009
Publication
Any technical installation need appropriate safety barriers installed to prevent or mitigate any adverse effects concerning people property and environment. In this context a safety barrier is a series of elements each consisting of a technical system or human action that implement a planned barrier function to prevent control or mitigate the propagation of a condition or event into an undesired condition or event. This is also important for new technologies as hydrogen refuelling stations being operated at very high pressures up to 900bar. In order to establish the needed barriers a hazard identification of the installation has to be carried out to identify the possible hazardous events. In this study this identification was done using the generic layout of a future large hydrogen refuelling station that has been developed by the EU NoE HySafe. This was based on experiences with smaller scale refuelling stations that has been in operation for several years e.g. being used in the former CUTE and ECTOS projects. Using this approach the object of the study is to support activities to further improve the safety performance of future larger refuelling stations. This will again help to inform the authorities and the public to achieve a proper public awareness and to support building up a realistic risk and safety perception of the safety on such future refuelling stations. In the second step the hazardous events that may take place and the barriers installed to stop hazards and their escalation are analysed also using in-house developed software to model the barriers and to quantify their performance. The paper will present an overview and discuss the state-of-the-art of the barriers established in the generic refuelling station.
Materials Considerations in Hydrogen Production
Sep 2007
Publication
Correct selection and application of materials is essential to ensure safety and economy in production transportation and storage of hydrogen. There are several sources of materials challenges related to hydrogen. Established component producers may have limited experience in this specific field. Process developments may involve new process conditions with new demands on the materials. Further new materials will be added to the engineering toolbox to be used. The behaviour of these materials for hydrogen service may need additional documentation. Finally focus on hydrogen susceptibility and hydrogen damages alone may take away awareness of other subjects as trace elements by-products and change in raw materials which may be of as high importance for safety and quality. This overview of challenges and recommendations is made with emphasis on water electrolysis.
Experimental Study on a Hydrogen Stratification Induced by PARs Installed in a Containment
Oct 2020
Publication
Hydrogen can be produced in undesired ways such as a high temperature metal oxidation during an accident. In this case the hydrogen must be carefully managed. A hydrogen mitigation system (HMS) should be installed to protect a containment of a nuclear power plant (NPP) from hazards of hydrogen produced by an oxidation of the fuel cladding during a severe accident in an NPP. Among hydrogen removal devices passive auto-catalytic recombiners (PARs) are currently applied to many NPPs because of passive characteristics such as not requiring a power supply nor an operators’ manipulations. However they offer several disadvantages resulting in issues related to hydrogen control by PARs. One of the issues is a hydrogen stratification in which hydrogen is not well-mixed in a compartment due to the high temperature exhaust gas of PARs and accumulation in the lower part. Therefore experimental simulation on hydrogen stratification phenomenon by PARs is required. When the hydrogen stratification by PARs is observed in the experiment the verification and improvement of a PAR analysis model using the experimental results can be performed and the hydrogen removal characteristics by PARs installed in an NPP can be evaluated using the improved PAR model. View Full-Text
A Temperature Controlled Mechanical Test Facility to Ensure Safe Materials Performance in Hydrogen at 1000 Bar
Sep 2007
Publication
Increasingly car manufacturers are turning to high pressure hydrogen storage for on-board power applications. Many prototypes use costly materials and fabrication methods such as Type 316L austenitic stainless steel and processes such as TIG (GTA) welding. There is a need to move to less expensive options without compromising safety to assist in developing economic vehicles. It is important that the behaviour of new/modified materials and joints (including those fabricated by new technologies) is understood at anticipated service temperatures and hydrogen pressure as the consequences of poor material choice could be severe. The greatest detrimental effect of gaseous hydrogen on the mechanical properties of metallic materials is commonly observed under conditions of dynamic plastic strain. Under such conditions an atomically clean surface is produced where hydrogen molecules will dissociate and penetrate the material. Thus static load test methods with hydrogen charging are not reliable for engineering data generation. To meet the need for dynamically straining material in a pressurised hydrogen environment TWI has developed a facility to load specimens in a high pressure environment for tensile toughness and fatigue testing. The design of this has involved a number of innovative steps. This paper outlines the requirements and the design and construction issues that were encountered when installing a facility which can not only perform tests at up to 1000bar (100MPa) but also for temperatures between –150°C to +85°C.
Risk Analysis of the Storage Unit in Hydrogen Refuelling Station
Sep 2007
Publication
Nowadays consumer demand for local and global environmental quality in terms of air pollution and in particular greenhouse gas emissions reduction may help to drive to the introduction of zero emission vehicles. At this regard the hydrogen technology appears to have future market valuablepotential. On the other hand the use of hydrogen vehicles which requires appropriate infrastructures for production storage and refuelling stages presents a lot of safety problems due to the peculiar chemicophysical hydrogen characteristics. Therefore safe at the most practices are essential for the successful proliferation of hydrogen vehicles. Indeed to avoid limit hazards it is necessary to implement practices that if early adopted in the development of a fuelling station project can allow very low environmental impact safety being incorporated in the project itself. Such practices generally consist in the integrated use of Failure Mode and Effect Analysis (FMEA) HAZard OPerability (HAZOP) and Fault Tree Analysis (FTA) which constitute well established standards in reliability engineering. At this regard however a drawback is the lack of experience and the scarcity of the relevant data collection. In this work we present the results obtained by the integrated use of FMEA HAZOP and FTA analyses relevant for the moment the high-pressure storage equipment in a hydrogen gas refuelling station. The study that is intended to obtain elements for improving safety of the system can constitute a basis for further more refined works.
Guidelines and Recommendations for Indoor Use of Fuel Cells and Hydrogen Systems
Oct 2015
Publication
Deborah Houssin-Agbomson,
Simon Jallais,
Elena Vyazmina,
Guy Dang-Nhu,
Gilles Bernard-Michel,
Mike Kuznetsov,
Vladimir V. Molkov,
Boris Chernyavsky,
Volodymyr V. Shentsov,
Dmitry Makarov,
Randy Dey,
Philip Hooker,
Daniele Baraldi,
Evelyn Weidner,
Daniele Melideo,
Valerio Palmisano,
Alexandros G. Venetsanos,
Jan Der Kinderen and
Béatrice L’Hostis
Hydrogen energy applications often require that systems are used indoors (e.g. industrial trucks for materials handling in a warehouse facility fuel cells located in a room or hydrogen stored and distributed from a gas cabinet). It may also be necessary or desirable to locate some hydrogen system components/equipment inside indoor or outdoor enclosures for security or safety reasons to isolate them from the end-user and the public or from weather conditions.<br/>Using of hydrogen in confined environments requires detailed assessments of hazards and associated risks including potential risk prevention and mitigation features. The release of hydrogen can potentially lead to the accumulation of hydrogen and the formation of a flammable hydrogen-air mixture or can result in jet-fires. Within Hyindoor European Project carried out for the EU Fuel Cells and Hydrogen Joint Undertaking safety design guidelines and engineering tools have been developed to prevent and mitigate hazardous consequences of hydrogen release in confined environments. Three main areas are considered: Hydrogen release conditions and accumulation vented deflagrations jet fires and including under-ventilated flame regimes (e.g. extinguishment or oscillating flames and steady burns). Potential RCS recommendations are also identified.
Simulation of Shock-Initiated Ignition
Sep 2009
Publication
The scenario of detonative ignition in shocked mixture is significant because it is a contributor to deflagration to detonation transition for example following shock reflections. However even in one dimension simulation of ignition between a contact surface or a flame and a shock moving into a combustible mixture is difficult because of the singular nature of the initial conditions. Initially as the shock starts moving into reactive mixture the region filled with reactive mixture has zero thickness. On a fixed grid the number of grid points between the shock and the contact surface increases as the shock moves away from the latter. Due to initial lack of resolution in the region of interest staircasing may occur whereby the resulting plots consist of jumps between few values a few grid points and these numerical artifacts are amplified by the chemistry which is very sensitive to temperature leading to unreliable results. The formulation is transformed replacing time and space by time and space over time as the independent variables. This frame of reference corresponds to the self-similar formulation in which the non-reactive problem remains stationary and the initial conditions are well-resolved. Additionally a solution obtained from short time perturbation is used as initial condition at a time still short enough for the perturbation to be very accurate but long enough so that there is sufficient resolution. The numerical solution to the transformed problem is obtained using an essentially non-oscillatory algorithm which is adequate not only for the early part of the process but also for the latter part when chemistry leads to appearance of a shock and eventually a detonation wave is formed. A validation study was performed and the results were compared with the literature for single step Arrhenius chemistry. The method and its implementation were found to be effective. Results are presented for values of activation energy ranging from mild to stiff.
Detonation Dynamics in a Curved Chamber for an Argon Diluted Hydrogen-oxygen Mixture
Sep 2019
Publication
The dynamics of detonation transmission from a straight channel into a curved chamber was investigated as a function of initial pressure using a combined experimental and numerical study. Hi-speed Schlieren and *OH chemiluminescense were used for flow visualization; numerical simulations considered the two-dimensional reactive Euler equations with detailed chemistry. Results show the highly transient sequence of events (i.e. detonation diffraction re-initiation attempts and wave reflections) that precede the formation of a steadily rotating Mach detonation along the outer wall of the chamber. An increase in pressure from 15 kPa to 26 kPa expectedly resulted in detonations that are less sensitive to diffraction. Local quenching of the initial detonation occurred for all pressures considered. The location where this decoupling occurred along the inner wall determined the location where transition from regular reflection to a rather complex wave structure occurred along the outer wall. This complex wave structure includes a steadily rotating Mach detonation (stem) an incident decoupled shock-reaction zone region and a transverse detonation that propagates in pre-shocked mixture.
A Comparison of Alternative Fuels for Shipping in Terms of Lifecycle Energy and Cost
Dec 2021
Publication
Decarbonization of the shipping sector is inevitable and can be made by transitioning into low‐ or zero‐carbon marine fuels. This paper reviews 22 potential pathways including conventional Heavy Fuel Oil (HFO) marine fuel as a reference case “blue” alternative fuel produced from natural gas and “green” fuels produced from biomass and solar energy. Carbon capture technology (CCS) is installed for fossil fuels (HFO and liquefied natural gas (LNG)). The pathways are compared in terms of quantifiable parameters including (i) fuel mass (ii) fuel volume (iii) life cycle (Well‐To‐ Wake—WTW) energy intensity (iv) WTW cost (v) WTW greenhouse gas (GHG) emission and (vi) non‐GHG emissions estimated from the literature and ASPEN HYSYS modelling. From an energy perspective renewable electricity with battery technology is the most efficient route albeit still impractical for long‐distance shipping due to the low energy density of today’s batteries. The next best is fossil fuels with CCS (assuming 90% removal efficiency) which also happens to be the lowest cost solution although the long‐term storage and utilization of CO2 are still unresolved. Biofuels offer a good compromise in terms of cost availability and technology readiness level (TRL); however the non‐GHG emissions are not eliminated. Hydrogen and ammonia are among the worst in terms of overall energy and cost needed and may also need NOx clean‐up measures. Methanol from LNG needs CCS for decarbonization while methanol from biomass does not and also seems to be a good candidate in terms of energy financial cost and TRL. The present analysis consistently compares the various options and is useful for stakeholders involved in shipping decarbonization.
Computational Modelling of Pressure Effects from Hydrogen Explosions
Sep 2007
Publication
The statement of the problem and algorithm of computational modelling of the processes of formation of the hydrogen-air mixture in the atmosphere its explosion (taking into account chemical interaction) and dispersion of the combustion materials in the open space with complex relief are presented. The finite-difference scheme was developed for the case of the three-dimensional system of gas dynamics equations complemented by the mass conservation laws of the gas admixture and combustion materials. The algorithm of the computation of thermal and physical parameters of the gas mixture appearing as a result of the instantaneous explosion taking into account chemical interaction was developed. The algorithm of computational solution of the difference scheme obtained on the basis of Godunov method was considered. The verification of the mathematical model showed its acceptable accuracy in comparison with known experimental data. It allows using the developed model for the modelling of pressure and thermal consequences of possible failures at the industrial enterprises which store and use hydrogen. The computational modelling of an explosion of the gas hydrogen cloud appearing as a result of instantaneous destruction of high pressure containers at the fuelling station was carried out. The analysis of different ways of protection of the surrounding buildings from destructive effects of the shock wave was conducted. The recommendations considering the choice of dimensions of the protection area around the fuelling station were worked out.
Experimental Study of Hydrogen Releases Combustion
Sep 2009
Publication
The objectives of the presented experimental work were investigation of hydrogen release distribution and combustion modelling possible emergency situation at industry scale. Results of large scale experiments on distribution and combustion in an open and congested area are presented. The mass of hydrogen in experiments varied from 50g to 1000g with release rate from 180 to 220 g/s. Qualitative characteristics of high momentum hydrogen jet releases distribution and subsequent combustion were obtained. It is shown that obstacles slow down jet speed promote combustible mixture formation in a large volume and accelerate combustion process. The maximum overpressure in experiments with additional congested area reached ΔР = 0.4 atm. Using partial confinement of congested area turbulent combustion regime with the maximum overpressure more than 10 atm. was obtained.
Measurement of Hydrogen Mixing Process by High Response Hydrogen Sensor
Sep 2017
Publication
According to the Global technical regulation on hydrogen and fuel cell vehicles (FCV) fuel cell discharge system at the vehicle exhaust system`s point of discharge the hydrogen concentration level shall not exceed 4 % average by volume during any moving three-second time interval during normal operation including start-up and shut down [1]. FC stack need to washout by the concentrated hydrogen as the purge gas and how to exhaust gas without exceeding 4 % is the most concerns. Also how to measure hydrogen pulse of millisecond in exhaust is also the rising up issue. In this paper model of FCV hydrogen discharge system was composed and variety of simple experiments were carried out to control the H2 concentration and release. In the case which the semiconductor sensor with porous material (average size less than quench distance) were applied to check H2 concentration the short pulse of high concentration of H2 in millisecond was hard to find. In this experiment the simple exhaust gas model H2/N2 flow was used instead of Air/H2. In the exhaust gas test experiment was conducted under the atmospheric condition in room temperature with small pressure difference and the fast solenoid valve to create quick hydrogen control. Most of the experiments except the turbulent flow experiments laminar flow is expected to be dominated when steady state condition is satisfied but the most result discussed here is the measurement of H2 concentration during the start point at the time of discharge within seconds. The results showed when H2 was added to N2 flow the boundary layer between N2 and H2 contained the high concentration of H2 at the initial wave front and decrease to reach steady state. This H2 pulse is typical in the FCV exhaust gas and topics of this paper.
The Role of Trust and Familiarity in Risk Communication
Sep 2009
Publication
In socio-economics it is well known that the success of an innovation process not only depends upon the technological innovation itself or the improvement of economic and institutional system boundaries but also on the public acceptance of the innovation. The public acceptance can as seen with genetic engineering for agriculture be an obstacle for the development and introduction of a new and innovative idea. In respect to hydrogen technologies this means that the investigation compilation and communication of scientific risk assessments are not sufficient to enhance or generate public acceptance. Moreover psychological social and cultural aspects of risk perception have to be considered when introducing new technologies. Especially trust and familiarity play an important role for risk perception and thus public acceptance of new technologies.
Inhomogeneous Hydrogen Deflagrations in the Presence of Obstacles in 25 m3 Enclosure. Experimental Results
Sep 2019
Publication
Explosion venting is a frequently used measure to mitigate the consequence of gas deflagrations in closed environments. Despite the effort to predict the vent area needed to achieved the protection through engineering formulas and CFD tools work has still to be done to reliably predict the outcome of a vented gas explosion. Blind-prediction exercises recently published show a large spread in the prediction of both engineering formula than CFD tools. University of Pisa performed experimental tests in a 25 m3 facility in inhomogeneous conditions and with the presence of simple obstacles constituted by plates bolted to HEB beams. The present paper is aimed to share the results of hydrogen dispersion and deflagration tests and discuss the comparison of maximum peak overpressure generated with different blockage ratio and repeated obstacles sets. Description of the experimental set-up includes all the details deemed necessary to reproduce the phenomenon with a CFD tool.
Fire Risk on High-pressure Full Composite Cylinders for Automotive Applications
Sep 2011
Publication
In the event of a fire the TPRD (Thermally activated Pressure Relief Device) prevents the high-pressure full composite cylinder from bursting by detecting high temperatures and releasing the pressurized gas. The current safety performance of both the vessel and the TPRD is demonstrated by an engulfing bonfire test. However there is no requirement concerning the effect of the TPRD release which may produce a hazardous hydrogen flame due to the high flow-rate of the TPRD. It is necessary to understand better the behavior of an unprotected composite cylinder exposed to fire in order to design appropriate protection for it and to be able to reduce the length of any potential hydrogen flame. For that purpose a test campaign was performed on a 36 L cylinder with a design pressure of 70 MPa. The time from fire exposure to the bursting of this cylinder (the burst delay) was measured. The influence of the fire type (partial or global) and the influence of the pressure in the cylinder during the exposure were studied. It was found that the TPRD orifice diameter should be significantly reduced compared to current practice.
Evaluation of Safety Distances Related to Unconfined Hydrogen Explosions
Sep 2005
Publication
A simple approximate method for evaluation of blast effects and safety distances for unconfined hydrogen explosions is presented. The method includes models for flame speeds hydrogen distribution blast parameters and blast damage criteria. An example of the application of this methodology for hydrogen releases in three hypothetical obstructed areas with different levels of congestion is presented. The severity of the blast effect of unconfined hydrogen explosions is shown to depend strongly on the level of congestion for relatively small releases. Extremely large releases of hydrogen are predicted to be less sensitive to the congestion level.
Attained Temperature During Gas Fuelling and Defueling Cycles of Compressed Hydrogen Tanks for FCV
Sep 2011
Publication
In this study we conducted hydrogen gas filling and discharging cycling tests to examine the thermal behaviour in hydrogen storage tanks under actual use conditions. As a result it was confirmed that the gas temperature in the tank varied depending on the initial test conditions such as the ambient temperature of the tank and the filling gas temperature and that the gas temperature tended to stabilize after several gas filling and discharging cycles.
Evaluation of the Protection Effectiveness Against Overpressure From Hydrogen-air Explosion
Sep 2017
Publication
The aim of this study is to assess the probability of the damage to hydrogen fuelling station personnel exposed to the hydrogen explosion shock wave. A three-dimensional mathematical model of the explosion of hydrogen-air cloud formed after the destruction of the high-pressure storage cylinders is developed. A computer technology how to define the personnel damage probability field on the basis of probit analysis of the generated shock wave is developed. To automate the process of computing the "probit function-damage probability" tabular dependence is replaced by a piecewise cubic spline. The results of calculations of overpressure fields impulse loading and the probability of damage to fuelling station personnel exposed to the shock wave are obtained. The mathematical model takes into account the complex terrain and three-dimensional non-stationary nature of the shock wave propagation process. The model allows to obtain time-spatial distribution of damaging factors (overpressure in the shock wave front and the compression phase impulse) required to determine the three-dimensional non-stationary damage probability fields based on probit analysis. The developed computer technology allows to carry out an automated analysis of the safety situation at the fuelling station and to conduct a comparative analysis of the effectiveness of different types of protective facilities.
Dynamic Load Analysis of Explosion in Inhomogeneous Hydrogen-air Mixtures
Sep 2017
Publication
This paper presents results from experiments on gas explosions in inhomogeneous hydrogen-air mixtures. The experimental channel is 3 m with a cross section of 100 mm by 100 mm and a 0.25 mm ID nozzle for hydrogen release into the channel. The channel is open in one end. Spectral analysis of the pressure in the channel is used to determine dynamic load factors for SDOF structures. The explosion pressures in the channel will fluctuate with several frequencies or modes and a theoretical high DLF is seen when the pressure frequencies and eigen frequencies of the structure matches.
The CALIF3S-P2remics Software – An Application to Underexpanded Hydrogen Jet Deflagration
Sep 2019
Publication
To assess explosion hazard the French Institut de Radioprotection et de Sûreté Nucléaire (IRSN) is developing the P2REMICS software (for Partially PREMIxed Combustion Solver) on the basis of the generic CFD solver library CALIF3S (for Components Adaptive Library for Fluid Flow Simulation). Both P2REMICS and CALIF3S are in-house IRSN softwares released under an open-source license. CALIF3S-P2REMICS is dedicated to the simulation of explosion scenarii (explosive atmosphere formation deflagration or detonation and blast waves propagation) for hydrogen as more generally for any explosive gas or gas/dust mixture. It is based on staggered space discretizations and implements fractional-steps time algorithms well suited for massively parallel computations. A wide range of experiments is used for the software validation. Among them we focus here on a free underexpanded hydrogen jet deflagration performed in two steps: first the hydrogen is released in air up to obtain a steady jet (dispersion phase) then the deflagration is triggered. For the dispersion phase simulation a notional nozzle approach is used to get rid of the description of the shocked zone located near the nozzle. Then a so-called turbulent flame velocity approach is chosen for the deflagration simulation. The computations allow to highlight the complex flow structures induced by the inhomogeneity fuel concentration in the jet. A large dispersion of results is observed depending on the chosen correlation for the turbulent flame speed.
Hydrogen Related Risks Within a Private Garage: Concentration Measurements in a Realistic Full Scale Experimental Facility
Sep 2007
Publication
Next generation of hydrogen energy based vehicles is expected to come into widespread use in the near future. Various topics related to hydrogen including production storage and application of hydrogen as an energy carrier have become subjects of discussion in the framework of various European and International projects. Safety information is vital to support the successful introduction into mainstream and public acceptance of hydrogen as an energy carrier. One of such issues which is seeking major attention is related to hydrogen powered vehicles parked inside a confined area (such as in a private garage). It is of utmost importance to predict if uncontrolled release of hydrogen from a vehicle parked inside a confined area can create an explosive atmosphere. Subsequently how the preventive measures can be implied to control these explosive atmospheres if present inside a confined area? There is a little guidance currently developed for confined areas accommodating hydrogen fuelled vehicles. It is essential that mitigation measures for such conditions become established.<br/>Characterization of different scenarios those may arise in a real situation from hydrogen fuelled vehicle parked inside a garage and furthermore the investigation of an optimal ventilation rate for hydrogen risk mitigation are some of the main objectives described in the framework of the present study. This work is an effort to provide detail experimental information’s in view of establishing guidelines for hydrogen powered vehicles parked inside a private garage. The present work is developed in the framework of a European Network of Excellence HySafe and French project DRIVE. Present paper describes a purpose built realistic Garage test facility at CEA to study the dispersion of hydrogen leakage. The studied test cases evaluate the influence of injected volumes of hydrogen and the initial conditions at the leakage source on the dispersion and mixing characteristics inside the free volume of the unventilated garage. The mixing process and build-up of hydrogen concentration is measured for the duration of 24 hours. Due to safety reasons helium gas is used to simulate the hydrogen dispersion characteristics.
Analysis of Composite Hydrogen Storage Cylinders under Transient Thermal Loads
Sep 2007
Publication
In order to ensure safe operation of hydrogen storage cylinders under adverse conditions one should be able to predict the extremities under which these cylinders are capable of operating without failing catastrophically. It is therefore necessary to develop a comprehensive model which can predict the behavior and failure of composite storage cylinders when subjected to various types of loading conditions and operating environments. In the present work a finite element model has been developed to analyze composite hydrogen storage cylinders subjected to transient localized thermal loads and internal pressure. The composite cylinder consists of an aluminium liner that serves as a hydrogen gas permeation barrier. A filament-wound carbon/epoxy composite laminate placed over the liner provides the desired load bearing capacity. A glass/epoxy layer or other material is placed over the carbon/epoxy laminate to provide damage resistance for the carbon/epoxy laminates. A doubly curved composite shell element accounting for transverse shear deformation and geometric nonlinearity is used. A temperature dependent material model has been developed and implemented in ABAQUS using user subroutine. A failure model based on Hashin's failure theory is used to predict the various types of failure in the cylinder. A progressive damage model has also been implemented to account for reduction in modulus due to failure. A sublaminate model has been developed to save computational time and reduce the complications in the analysis. A numerical study is conducted to analyze a typical hydrogen storage cylinder and possible failure trends due to localized thermal loading and internal pressure is presented.
Blending Ammonia into Hydrogen to Enhance Safety through Reduced Burning Velocity
Sep 2019
Publication
Laminar burning velocities (SL) of hydrogen/ammonia mixtures in air at atmospheric pressure were studied experimentally and numerically. The blending of hydrogen with ammonia two fuels that have been proposed as promising carriers for renewable energy causes the laminar flame speed of the mixture SL to decrease significantly. However details of this have not previously available. Systematic measurements were therefore performed for a series of hydrogen/ammonia mixtures with wide ranges of mole fractions of blended ammonia (XNH3) and equivalence ratio using a heat flux method based on heat flux of a flat flame transferred to the burner surface. It was found that the mixture of XNH3 = 40% has a value of SL close to that of methane which is the dominant component of natural gas. Using three chemical kinetic mechanisms available in the literature i.e. the well-known GRI-Mech 3.0 mechanism and two mechanisms recently released SL were also modelled for the cases studied. However the discrepancies between the experimental and numerical results can exceed 50% with the GRI-Mech 3.0 mechanism. Discrepancies were also found between the numerical results obtained with different mechanisms. These results can contribute to an increase in both the safety and efficiency of the coutilization of these two types of emerging renewable fuel and to guiding the development of better kinetic models.
Full Scale Experimental Campaign to Determine the Actual Heat Flux Produced by Fire on Composite Storages - Calibration Tests on Metallic Vessels
Oct 2015
Publication
If Hydrogen is expected to be highly valuable some improvements should be conducted mainly regarding the storage safety. To prevent from high pressure hydrogen composite tanks bursting the comprehension of the thermo-mechanics phenomena in the case of fire should be improved. To understand the kinetic of strength loss the heat flux produced by fire of various intensities should be assessed. This is the objective of this real scale experimental campaign which will allow studying in future works the strength loss of composite high-pressure vessels in similar fire conditions to the ones determined in this study. Fire calibration tests were performed on metallic cylinder vessels. These tests with metallic cylinders are critical in the characterization of the thermal load of various fire sources (pool fire propane gas fire hydrogen gas fire) so as to evaluate differences related to different thermal load. Radiant panels were also used as thermal source for reference of pure radiation heat transfer. The retained thermal load might be representative of accidental situations in worst case scenarios and relevant for a standardized testing protocol. The tests performed show that hydrogen gas fires and heptane pool fire allow reaching the target in terms of absorbed energy regarding the results of risk analysis performed previously. Other considerations can be taken into account that will led to retain an hydrogen gas fire for further works. Firstly hydrogen gas fire is the more realistic scenario: Hydrogen is the combustible that we every time find near an hydrogen storage. Secondly as one of the objectives of the project is to make recommendations for standardization issues it’s important to note that gas fires are not too complex to calibrate control and reproduce. Finally due to previous considerations Hydrogen gas fire will be retained for thermal load of composite cylinders in future works.
Hydrogen for Renewable Energy Export: Broadening the Concept of Hydrogen Safety
Sep 2019
Publication
Recently we have seen hydrogen (re)emerge as an important component of widespread decarbonisation of energy sectors. From an Australian perspective this brings with it an opportunity to store transport and export renewable energy—either as liquefied hydrogen or in a carrier such as ammonia. The growth of the hydrogen industry to now include the power and transport sectors as well as the notion of hydrogen export has broadened the range of safety considerations required and seen them extend into the realm of the consumer for the first time.<br/>Hydrogen as well as ammonia and other carriers such as methanol are existing industrial chemicals which have established protocols for their handling and use in the chemicals sector. As their use in energy and transport increases especially in the context of widespread domestic use their handling and use by inexperienced people in less-controlled environments expands shifting the risk profiles and management systems required. There is also the potential for novel hydrogen carriers such as methylcyclohexane/toluene to reach commercial viability at industrial scale.<br/>This paper will discuss some of these emerging applications of hydrogen and its carriers and discuss some of the technological innovations under development that may accompany a new energy industry— with some consideration given to their potential risks and the required safety considerations. In addition we will also provide an overview of global activity in this area and how new standards and regulations would need to be developed for the adaption of these technologies in an Australian context.
The Hydrogen Executive Leadership Panel (HELP) Initiative for Emergency Responder Training
Sep 2007
Publication
In close cooperation with their Canadian counterparts United States public safety authorities are taking the first steps towards creating a proper infrastructure to ensure the safe use of the new hydrogen fuel cells now being introduced commercially. Currently public safety officials are being asked to permit hydrogen fuel cells for stationary power and as emergency power backups for the telecommunications towers that exist everywhere. Consistent application of the safety codes is difficult – in part because it is new – yet it is far more complex to train emergency responders to deal safely with the inevitable hydrogen incidents. The US and Canadian building and fire codes and standards are similar but not identical. The US and Canadian rules are unlikely to be useful to other nations without modification to suit different regulatory systems. However emergency responder safety training is potentially more universal. The risks strategies and tactics are unlikely to differ much by region. The Hydrogen Executive Leadership Panel (HELP) made emergency responder safety training its first priority because the transition to hydrogen depends on keeping incidents small and inoffensive and the public and responders safe from harm. One might think that advising 1.2 million firefighters and 800000 law enforcement officers about hydrogen risks is no more complicated than adding guidance to a website. One would be wrong. The term “training” has specific legal implications which may vary by state. For hazardous materials federal requirements apply. Insurance companies place training requirements on the policies they sell to fire departments including the thousands of small all-volunteer departments which may operate as private corporations. Union contracts may define training and promotions may be based on satisfactorily completed certain levels of training. Emergency responders could no sooner learn how to extinguish a<br/>hydrogen fire by reading a webpage than a person could learn to ride a bicycle by reading a book. Procedures must be learned by listening reading and then doing. Regular practice is necessary. As new hydrogen applications are commercialized additional responder training may be necessary. This highlights another obstacle emergency responders’ ability to travel distances and take the time to undergo training. Historically fire academies established adjunct instructor programs and satellite academies to bring the training to firefighters. The large well-equipped academies are typically used for specialized training. States rarely have enough instructors and instructors often must take the time to create a course outline research each point and produce a program that is informative useful and holds the attention of responders. The challenge of training emergency responders seems next to impossible but public safety authorities are asked to tackle the impossible every day and a model exists to move forward in the U.S. Over the past few years the National Association of State Fire Marshals and U.S. Department of Transportation enlisted the help of emergency responders and industry to create a standardized approach to train emergency responders to deal with pipeline incidents. A curriculum and training materials were created and more than 26000 sets have been distributed for free to public safety agencies nationwide. More than 8000 instructors have been trained to use these materials that are now part of the regular training in 23 states. Using this model HELP intends to ensure that all emergency responders are trained to address hydrogen risks. The model and the rigorous scenario analysis and review used to developing the operational and technical training is addressed in this paper.
Defect Assessment on Pipe Used For Transport of Mixture of Hydrogen and Natural Gas
Sep 2009
Publication
The present article indicates the change of mechanical properties of X52 gas pipe steel in presence of hydrogen and its consequence on defect assessment particularly on notch like defects. The purpose of this work is to determine if the transport of a mixture of natural gas and hydrogen in the actual existing European natural gas pipe network can be done with a reasonable low failure risk (i.e. a probability of failure less than 10-6). To evaluate this risk a deterministic defect assessment method has been established. This method is based on Failure Assessment Diagram and more precisely on a Modified Notch Failure Assessment Diagram (MNFAD) which has been proposed for this work. This MNFAD is coupled with the SINTAP failure curve and allows determining the safety factor associated with defect geometry loading conditions and material resistance. The work described in this paper was performed within the NATURALHY work package 3 on ’Durability of pipeline material’.
Synthesis and Performance of Photocatalysts for Photocatalytic Hydrogen Production: Future Perspectives
Dec 2021
Publication
Photocatalysis for “green” hydrogen production is a technology of increasing importance that has been studied using both TiO2–based and heterojunction composite-based semiconductors. Different irradiation sources and reactor units can be considered for the enhancement of photocatalysis. Current approaches also consider the use of electron/hole scavengers organic species such as ethanol that are “available” in agricultural waste in communities around the world. Alternatively organic pollutants present in wastewaters can be used as organic scavengers reducing health and environmental concerns for plants animals and humans. Thus photocatalysis may help reduce the carbon footprint of energy production by generating H2 a friendly energy carrier and by minimizing water contamination. This review discusses the most up-to-date and important information on photocatalysis for hydrogen production providing a critical evaluation of: (1) The synthesis and characterization of semiconductor materials; (2) The design of photocatalytic reactors; (3) The reaction engineering of photocatalysis; (4) Photocatalysis energy efficiencies; and (5) The future opportunities for photocatalysis using artificial intelligence. Overall this review describes the state-of-the-art of TiO2–based and heterojunction composite-based semiconductors that produce H2 from aqueous systems demonstrating the viability of photocatalysis for “green” hydrogen production.
Hydrogen Effect on Fatigue and Fracture of Pipe Steels
Sep 2009
Publication
Transport by pipe is one the most usual way to carry liquid or gaseous energies from their extraction point until their final field sites. To limit explosion risk or escape to avoid pollution problems and human risks it is necessary to assess nocivity of defect promoting fracture. This need to know the mechanical properties of the pipes steels. Hydrogen is considered to day as a new energy vector and its transport in one of the key problems to extension of its use. Within the European project NATURALHY it has been proposed to transport a mixture of natural gas and hydrogen. 39 European partners have combined their efforts to assess the effects of hydrogen presence on the existing gas network. Key issues are durability of pipeline material integrity management safety aspects life cycle and socio-economic assessment and end-use. The work described in this paper was performed within the NATURALHY work package on ’Durability of pipeline material’. This study makes it possible to emphasize the hydrogen effect on mechanical properties of several pipe steels as X52 X70 or X100 in fatigue and fracture and in two different environments: air and hydrogen electrolytic.
Development of NaBH4-Based Hydrogen Generator for Fuel Cell Unmanned Aerial Vehicles with Movable Fuel Cartridge
Mar 2019
Publication
NaBH4-based hydrogen generator for fuel cell Unmanned Aerial Vehicle (UAVs) with movable fuel cartridge was developed in the present study. The main fuel of hydrogen generator is Sodium borohydride (NaBH4) that is a kind of chemical hydride and has a high hydrogen storage density. In the previous studies hydrogen generators were developed in which hydrogen was directly generated from solid state NaBH4. However it was a prototype so inconvenient to replace the fuel after used up and lacked user convenience. Therefore the performance evaluation and the development procedure of NaBH4-based hydrogen generator that was designed taking user convenience in consideration for commercialization were described in this paper.
Hydrogen Safety- New Challenges Based on BMW Hydrogen 7
Sep 2007
Publication
The BMW Hydrogen 7 is the world’s first premium sedan with a bi-fuelled internal combustion engine concept that has undergone the series development process. This car also displays the BMW typical driving pleasure. During development the features of the hydrogen energy source were emphasized. Engine tank system and vehicle electronics were especially developed as integral parts of the vehicle for use with hydrogen. The safety-oriented development process established additional strict hydrogen-specific standards for the Hydrogen 7. The fulfilment of these standards were demonstrated in a comprehensive experimentation and testing program which included all required tests and a large number of additional hydrogen-specific crash tests such as side impacts to the tank coupling system or rear impacts. Furthermore the behaviour of the hydrogen tank was tested under extreme conditions for instance in flames and after strong degradation of the insulation. Testing included over 1.7 million km of driving; and all tests were passed successfully proving the intrinsic safety of the vehicle and also confirming the success of the safety-oriented development process which is to be continued during future vehicle development. A safety concept for future hydrogen vehicles poses new challenges for vehicles and infrastructure. One goal is to develop a car fuelled by hydrogen only while simultaneously optimizing the safety concept. Another important goal is removal of (self-imposed) restrictions for parking in enclosed spaces such as garages. We present a vision of safety standards requirements and a program for fulfilling them.
Integrating IT-SOFC and Gasification Combined Cycle with Methanation Reactor and Hydrogen Firing for Near Zero-emission Power Generation from Coal
Apr 2011
Publication
Application of Solid Oxide Fuel Cells (SOFC) in gasification-based power plants would represent a turning point in the power generation sector allowing to considerably increase the electric efficiency of coal-fired power stations while reducing CO2 and other pollutant emissions. The aim of this paper is the thermodynamic assessment of a SOFC-based IGFC plant with methanation reactor hydrogen post-firing and CO2 capture by physical absorption. The configuration proposed allows to obtain a very high net efficiency (51.6%) overcoming the main limits of configurations assessed in previous works.
Real-gas Equations-of-State for the GASFLOW CFD Code
Sep 2011
Publication
GASFLOW is a finite-volume computer code that solves the time-dependent two-phase homogeneous equilibrium model compressible Navier–Stokes equations for multiple gas species with turbulence. The fluid-dynamics algorithm is coupled with conjugate heat and mass transfer models to represent walls floors ceilings and other internal structures to describe complex geometries such as those found in nuclear containments and facilities. Recent applications involve simulations of cryogenic hydrogen tanks at elevated pressures. These applications which often have thermodynamic conditions near the critical point require more accurate real-gas Equations-of-State (EoS) and transport properties than the standard ideal gas EoS and classical kinetic-theory transport properties. This paper describes the rigorous implementation of the generalized real-gas EoS into the GASFLOW CFD code as well as the specific implementation of respective real-gas models (Leachman's NIST hydrogen EoS a modified van der Waals EoS and a modified Nobel-Abel EoS); it also includes a logical testing procedure based upon a numerically exact benchmark problem. An example of GASFLOW simulations is presented for an ideal cryo-compressed hydrogen tank of the type utilized in fuel cell vehicles.
Decarbonizing Russia: Leapfrogging from Fossil Fuel to Hydrogen
Jan 2022
Publication
We examine a different approach to complete the decarbonization of the Russian economy in a world where climate policy increasingly requires the radical reduction of emissions wherever possible. We propose an energy system that can supply solar and wind-generated electricity to fulfill demand and which accounts for intermittency problems. This is instead of the common approach of planning for expensive carbon capture and storage and a massive increase in energy efficiency and therefore a drastic reduction in energy use per unit of Gross Domestic Product (GDP). Coupled with this massive increase in alternative energy we also propose using excess electricity to generate green hydrogen. Hydrogen technology can function as storage for future electricity needs or for potential fuel use. Importantly green hydrogen can potentially be used as a replacement export for Russia’s current fossil fuel exports. The analysis was carried out using the highly detailed modeling framework the High-Resolution Renewable Energy System for Russia (HIRES-RUS) representative energy system. The modeling showed that there are a number of feasible combinations of wind and solar power generation coupled with green hydrogen production to achieve 100% decarbonization of the Russian economy.
Evaluation of Optical and Spectroscopic Experiments of Hydrogen Jet Fires
Sep 2009
Publication
This paper reports results of evaluating joint experiments under the work programme of Hysafe occurring at HSL who provided the test facilities and basic measurements to generate jet fires whereas Fraunhofer ICT applied their equipment to visualise the jet fires by fast video techniques IR-cameras and fast scanning spectroscopy in the NIR/IR spectral region. Another paper describes the experimental set up and main findings of flame structures and propagation resolved in time. The spatial distribution of species and temperate as well as their time history and fluctuations give a basis of the evaluation of effects caused by such jet fires. Fraunhofer ICT applied their comprehensive evaluation codes to model the radiation emission from 3-atomic species in the flame especially H2O in the Infrared spectral range. The temperatures of the hydrogen flame were about 2000 K as found by least squares fit of the measured molecular bands by the codes. In comparison with video and thermo camera frames these might enable to estimate on a qualitative level species distribution and air entrainment and temperatures to identify hot and reactive zones. The risk analysis could use this information to estimate heat transfer and the areas of risk to direct inflammation from the jet fires by semi-empirical approaches.
Energy Storage as Part of a Secure Energy Supply
Mar 2017
Publication
Florian Ausfelder,
Christian Beilmann,
Martin Bertau,
Sigmar Bräuninger,
Angelika Heinzel,
Renate Hoer,
Wolfram Koch,
Falko Mahlendorf,
Anja Metzelthin,
Marcell Peuckert,
Ludolf Plass,
Konstantin Räuchle,
Martin Reuter,
Georg Schaub,
Sebastian Schiebahn,
Ekkehard Schwab,
Ferdi Schüth,
Detlef Stolten,
Gisa Teßmer,
Kurt Wagemann and
Karl-Friedrich Ziegahn
The current energy system is subject to a fundamental transformation: A system that is oriented towards a constant energy supply by means of fossil fuels is now expected to integrate increasing amounts of renewable energy to achieve overall a more sustainable energy supply. The challenges arising from this paradigm shift are currently most obvious in the area of electric power supply. However it affects all areas of the energy system albeit with different results. Within the energy system various independent grids fulfill the function of transporting and spatially distributing energy or energy carriers and the demand-oriented supply ensures that energy demands are met at all times. However renewable energy sources generally supply their energy independently from any specific energy demand. Their contribution to the overall energy system is expected to increase significantly.<br/>Energy storage technologies are one option for temporal matching of energy supply and demand. Energy storage systems have the ability to take up a certain amount of energy store it in a storage medium for a suitable period of time and release it in a controlled manner after a certain time delay. Energy storage systems can also be constructed as process chains by combining unit operations each of which cover different aspects of these functions. Large-scale mechanical storage of electric power is currently almost exclusively achieved by pumped-storage hydroelectric power stations.<br/>These systems may be supplemented in the future by compressed-air energy storage and possibly air separation plants. In the area of electrochemical storage various technologies are currently in various stages of research development and demonstration of their suitability for large-scale electrical energy storage. Thermal energy storage technologies are based on the storage of sensible heat exploitation of phase transitions adsorption/desorption processes and chemical reactions. The latter offer the possibility of permanent and loss-free storage of heat. The storage of energy in chemical bonds involves compounds that can act as energy carriers or as chemical feedstocks. Thus they are in direct economic competition with established (fossil fuel) supply routes. The key technology here – now and for the foreseeable future – is the electrolysis of water to produce hydrogen and oxygen.<br/>Hydrogen can be transformed by various processes into other energy carriers which can be exploited in different sectors of the energy system and/or as raw materials for energy-intensive industrial processes. Some functions of energy storage systems can be taken over by industrial processes. Within the overall energy system chemical energy storage technologies open up opportunities to link and interweave the various energy streams and sectors. Chemical energy storage not only offers means for greater integration of renewable energy outside the electric power sector it also creates new opportunities for increased flexibility novel synergies and additional optimization.<br/>Several examples of specific energy utilization are discussed and evaluated with respect to energy storage applications. The article describes various technologies for energy storage and their potential applications in the context of Germany’s Energiewende i.e. the transition towards a more sustainable energy system. Therefore the existing legal framework defines some of the discussions and findings within the article specifically the compensation for renewable electricity providers defined by the German Renewable Energy Sources Act which is under constant reformation. While the article is written from a German perspective the authors hope this article will be of general interest for anyone working in the areas of energy systems or energy technology.
Effect of Expansion Ratio on Flame Acceleration During Hydrogen Fueled Gas Explosions
Sep 2019
Publication
A precise understanding of the flame turbulence induced by cellular instabilities is indispensable to perform an appropriate risk assessment of hydrogen fuelled gas explosion. In this research Darrieus Landau instability (DL instability) whose effect on gas explosion is remarkable was experimentally examined. The DL instability is essentially caused by a volumetric expansion of burned gas at flame front. Therefore in order to examine the effects of volumetric expansion ratio the experiments were conducted using H2-O2-N2-Ar gas mixtures of various volumetric expansion ratio conditions by changing N2-Ar ratio. When Ar content ratio is increased the flame temperature becomes higher and volumetric expansion ratio is increased owing to lower specific heat of Ar. The experiments were conducted in nearly unconfined conditions of laboratory-scale and large-scale. Gas mixtures were filled in a 10 cm diameter soap bubble for the laboratory-scale and in a plastic tent of thin vinyl sheet of 1m3 for the large-scale. The gas mixtures were ignited by an electric spark and blast wave and flame speed were measured simultaneously by using a pressure sensor and a high-speed video camera. The DL instability owing to volumetric expansion accelerates flame propagation. In addition the intensity of blast wave was greatly raised depending on flame acceleration which can be explained by an acoustic theory. The effects of expansion ratio and experimental scales on flame propagation and blast wave were analyzed in detail. These results are quite important to perform an appropriate consequence analysis of accidental explosion of hydrogen.
Application of DFT Simulation to the Investigation of Hydrogen Embrittlement Mechanism and Design of High Strength Low Alloy Steel
Dec 2022
Publication
In this work first-principles methods were performed to simulate interactions between hydrogen and common alloying elements of high strength low alloy (HSLA) steel. The world has been convinced that hydrogen could be one of the future clean energy sources. HSLA steel with a balance of strength toughness and hydrogen embrittlement susceptibility is expected for application in large-scale hydrogen storage and transportation. To evaluate the property deterioration under a hydrogen atmosphere hydrogen embrittlement (HE) of HSLA steel attracts attention. However due to the small size of hydrogen atoms the mechanism of HE is challenging to observe directly by current experimental methods. To understand the HE mechanism at an atomic level DFT methods were applied to simulate the effects of alloying elements doping in bcc-Fe bulk structure and grain boundary structure. Furthermore the potential application of DFT to provide theoretical advice for HSLA steel design is discussed.
Vented Explosion Overpressures From Combustion of Hydrogen and Hydrocarbon Mixtures
Sep 2009
Publication
Experimental data obtained for hydrogen mixtures in a room-size enclosure are presented and compared with data for propane and methane mixtures. This set of data was also used to develop a three-dimensional gas dynamic model for the simulation of gaseous combustion in vented enclosures. The experiments were performed in a 64 m3 chamber with dimensions of 4.6 × 4.6 × 3.0 m and a vent opening on one side and vent areas of either 2.7 or 5.4 m2 were used. Tests were performed for three ignition locations at the wall opposite the vent at the center of the chamber or at the center of the wall containing the vent. Hydrogen–air mixtures with concentrations close 18% vol. were compared with stoichiometric propane–air and methane–air mixtures. Pressure data as function of time and flame time-of-arrival data were obtained both inside and outside the chamber near the vent. Modelling was based on a Large Eddy Simulation (LES) solver created using the OpenFOAM CFD toolbox using sub-grid turbulence and flame wrinkling models. A comparison of these simulations with experimental data is discussed.
Enhancing the Efficiency of Power- and Biomass-to-liquid Fuel Processes Using Fuel-assisted Solid Oxide Electrolysis Cells
Apr 2022
Publication
Power- and biomass-to-liquid fuel processes (PBtL) can utilize renewable energy and residual forestry waste to produce liquid synthetic fuels which have the potential to mitigate the climate impacts of the current transportation infrastructure including the long-haul aviation sector. In a previous study we demonstrated that implementing a solid oxide electrolysis cell (SOEC) in the PBtL process can significantly increase the energy efficiency of fuel production by supplying the produced hydrogen to a reverse water gas shift (RWGS) reactor to generate syngas which is then fed downstream to a Fischer–Tropsch (FT) reactor. The tail gas emitted from the FT reactor consists primarily of a mixture of hydrogen carbon monoxide and methane and is often recycled to the entrained flow gasifier located at the beginning of the process. In this analysis we investigate the efficiency gains of the PBtL process as a result of redirecting the tail gas of the FT reactor to the anode of an SOEC to serve as fuel. Supplying fuel to an SOEC can lower the electrical work input required to facilitate steam electrolysis when reacting electrochemically with oxide ions in the anode which in turn can reduce oxygen partial pressures and thus alleviate material degradation. Accordingly we develop a thermodynamic framework to reveal the performance limits of fuel-assisted SOECs (FASOECs) and provide strategies to minimize oxygen partial pressures in the SOEC anode. Additionally we elucidate how much fuel is required to match the heating demands of a cell when steam is supplied to the cathode over a broad range of inlet temperatures and demonstrate the influence of a set of reaction pathways of the supplied fuel on the operating potential of an FASOEC and the corresponding efficiency gain of the PBtL process. Based on preliminary calculations we estimate that implementing an FASOEC in the PBtL process can increase the energy efficiency of fuel production to more than 90% depending on the amount of FT tail gas available to the system.
Effect of Microstructural and Environmental Variables on Ductility of Austenitic Stainless Steels
Sep 2019
Publication
Austenitic stainless steels are used extensively in harsh environments including for high-pressure gaseous hydrogen service. However the tensile ductility of this class of materials is very sensitive to materials and environmental variables. While tensile ductility is generally insufficient to qualify a material for hydrogen service ductility is an effective tool to explore microstructural and environmental variables and their effects on hydrogen susceptibility to inform understanding of the mechanisms of hydrogen effects in metals and to provide insight to microstructural variables that may improve relative performance. In this study hydrogen precharging was used to simulate high-pressure hydrogen environments to evaluate hydrogen effects on tensile properties. Several austenitic stainless steels were considered including both metastable and stable alloys. Room temperature and subambient temperature tensile properties were evaluated with three different internal hydrogen contents for type 304L and 316L austenitic stainless steels and one hydrogen content for XM-11. Significant ductility loss was observed for both metastable and stable alloys suggesting the stability of the austenitic phase is not sufficient to characterize the effects of hydrogen. Internal hydrogen does influence the character of deformation which drives local damage accumulation and ultimately fracture for both metastable and stable alloys. While a quantitative description of hydrogen-assisted fracture in austenitic stainless steels remains elusive these observations underscore the importance of the hydrogen-defect interactions and the accumulation of damage at deformation length scales.
CFD Benchmark Based on Experiments of Helium Dispersion in a 1m3 Enclosure–intercomparisons for Plumes
Sep 2013
Publication
In the context of the French DIMITRHY project ANR-08-PANH006 experiments have been carried out to measure helium injections in a cubic 1 m3 box - GAMELAN in a reproducible and quantitative manner. For the present work we limit ourselves to the unique configuration of a closed box with a small hole at its base to prevent overpressure. This case leads to enough difficulties of modelisations to deserve our attention. The box is initially filled with air and injections of helium through a tube of diameter 20 mm is operated. The box is instrumented with catharometres to measure the helium volume concentration within an accuracy better than 0.1%. We present the CFD (Fluent and CASTEM ANSYS-CFX and ADREA-HF) calculations results obtained by 5 different teams participating to the benchmark in the following situation: the case of a plume release of helium in a closed box (4NL/min). Parts of the CFD simulations were performed in the European co-funded project HyIndoor others were performed in the French ANR-08-PANH006 DimitrHy project.
First Responder Training Supporting Commercialization of Hydrogen and Fuel Cell Technologies
Oct 2015
Publication
A properly trained first responder community is critical to the successful introduction of hydrogen fuel cell applications and their transformation in how we use energy. Providing resources with accurate information and current knowledge is essential to the delivery of effective hydrogen and fuel cell-related first responder training. The California Fuel Cell Partnership and the Pacific Northwest National Laboratory have over 15 years of experience in developing and delivering hydrogen safety-related first responder training materials and programs. A National Hydrogen and Fuel Cell Emergency Response Training Resource was recently released. This training resource serves the delivery of a variety of training regimens. Associated materials are adaptable for different training formats ranging from high-level overview presentations to more comprehensive classroom training. This paper presents what has been learned from the development and delivery of hydrogen safety-related first responder training programs (online classroom hands-on) by the respective organizations. The collaborative strategy being developed for enhancing training materials and methods for greater accessibility based on stakeholder input will be discussed.
Experimental Investigation of Spherical-flame Acceleration in Lean Hydrogen-air Mixtures
Oct 2015
Publication
Large-scale experiments examining spherical-flame acceleration in lean hydrogen-air mixtures were performed in a 64 m3 constant-pressure enclosure. Equivalence ratios ranging from 0.33 to 0.57 were examined using detailed front tracking for flame diameters up to 1.2 m through the use of a Background Oriented Schlieren (BOS) technique. From these measurements the critical radii for onset of instability for these mixtures on the order of 2–3 cm were obtained. In addition the laminar burning velocity and rate of flame acceleration as a function of radius were also measured.
Material Testing and Design Recommendations for Components Exposed to Hydrogen Enhanced Fatigue – the Mathryce Project
Sep 2013
Publication
The three years European MATHRYCE project dedicated to material testing and design recommendations for components exposed to hydrogen enhanced fatigue started in October 2012. Its main goal is to provide an “easy” to implement methodology based on lab-scale experimental tests under hydrogen gas to assess the service life of a real scale component taking into account fatigue loading under hydrogen gas. Dedicated experimental tests will be developed for this purpose. In the present paper the proposed approach is presented and compared to the methodologies currently developed elsewhere in the world.
Heading for Hydrogen - The Oil and Gas Industry’s Outlook for Hydrogen, From Ambition to Reality
May 2020
Publication
The future of hydrogen energy is wrapped up with the future of natural gas renewable energy and carbon capture and storage (CCS). This yields useful synergies but also political economic and technical complexity. Nevertheless our survey of more than 1000 senior oil and gas professionals suggests a more certain future for hydrogen and that the time is right to begin scaling the hydrogen economy.
Inhibition of Hydrogen-yielding Dark Fermentation by Ascomycetous Yeasts
May 2018
Publication
Hydrogen-yielding fermentation conducted in bioreactors is an alternative method of hydrogen production. However unfavourable processes can seriously inhibit bio-hydrogen generation during the acidogenic step of anaerobic digestion. Here ascomycetous yeasts were identified as a major factor inhibiting the production of bio-hydrogen by fermentation. Changes in the performance of hydrogen-producing bioreactors including metabolic shift quantitative changes in the fermentation products decreased pH instability of the microbial community and consequently a dramatic drop in bio-hydrogen yield were observed following yeast infection. Ascomycetous yeasts from the genera Candida Kazachstania and Geotrichum were isolated from hydrogen-producing bioreactors. Yeast metabolites secreted into the growth medium showed antibacterial activity. Our studies indicate that yeast infection of hydrogen-producing microbial communities is one of the serious obstacles to use dark fermentation as an alternative method of bio-hydrogen production. It also explains why studies on hydrogen fermentation are still limited to the laboratory or pilot-scale systems.
To Adopt CCU Technology or Not? An Evolutionary Game between Local Governments and Coal-Fired Power Plants
Apr 2022
Publication
Carbon dioxide capture and utilization (CCU) technology is a significant means by which China can achieve its ambitious carbon neutrality goal. It is necessary to explore the behavioral strategies of relevant companies in adopting CCU technology. In this paper an evolutionary game model is established in order to analyze the interaction process and evolution direction of local governments and coal-fired power plants. We develop a replicator dynamic system and analyze the stability of the system under different conditions. Based on numerical simulation we analyze the impact of key parameters on the strategies of stakeholders. The simulation results show that the unit prices of hydrogen and carbon dioxide derivatives have the most significant impact: when the unit price of hydrogen decreases to 15.9 RMB/kg or the unit price of carbon dioxide derivatives increases to 3.4 RMB/kg the evolutionary stabilization strategy of the system changes and power plants shift to adopt CCU technology. The results of this paper suggest that local governments should provide relevant support policies and incentives for CCU technology deployment as well as focusing on the synergistic development of CCU technology and renewable energy hydrogen production technology
Hydrogen Fast Filling to a Type IV Tank Developed for Motorcycles
Oct 2015
Publication
If Hydrogen is expected to be highly valuable some improvements should be conducted mainly regarding the storage safety. To prevent from high pressure hydrogen composite tanks bursting the comprehension of the thermo-mechanics phenomena in the case of fire should be improved. To understand the kinetic of strength loss the heat flux produced by fire of various intensities should be assessed. This is the objective of this real scale experimental campaign which will allow studying in future works the strength loss of composite high-pressure vessels in similar fire conditions to the ones determined in this study. Fire calibration tests were performed on metallic cylinder vessels. These tests with metallic cylinders are critical in the characterization of the thermal load of various fire sources (pool fire propane gas fire hydrogen gas fire) so as to evaluate differences related to different thermal load. Radiant panels were also used as thermal source for reference of pure radiation heat transfer. The retained thermal load might be representative of accidental situations in worst case scenarios and relevant for a standardized testing protocol. The tests performed show that hydrogen gas fires and heptane pool fire allow reaching the target in terms of absorbed energy regarding the results of risk analysis performed previously. Other considerations can be taken into account that will led to retain an hydrogen gas fire for further works. Firstly hydrogen gas fire is the more realistic scenario: Hydrogen is the combustible that we every time find near an hydrogen storage. Secondly as one of the objectives of the project is to make recommendations for standardization issues it's important to note that gas fires are not too complex to calibrate control and reproduce. Finally due to previous considerations Hydrogen gas fire will be retained for thermal load of composite cylinders in future works.
LES Modelling Of Hydrogen Release and Accumulation Within a Non-Ventilated Ambient Pressure Garage Using The Adrea-HF CFD Code
Sep 2011
Publication
Computational Fluid Dynamics (CFD) has already proven to be a powerful tool to study the hydrogen dispersion and help in the hydrogen safety assessment. In this work the Large Eddy Simulation (LES) recently incorporated into the ADREA-HF CFD code is evaluated against the INERIS-6C experiment of hydrogen leakage in a supposed garage which provides detailed experimental measurements visualization of the flow and availability of previous CFD results from various institutions (HySafe SBEP-V3). The short-term evolution of the hydrogen concentrations in this confined space is examined and comparison with experimental data is provided along with comments about the ability of LES to capture the transient phenomena occurring during hydrogen dispersion. The influence of the value of the Smagorinsky constant on the resolved and on the unresolved turbulence is also presented. Furthermore the renormalization group (RNG) LES methodology is also tested and its behaviour in both highly-turbulent and less-turbulent parts of the flow is highlighted.
Influence of the Location of a Buoyant Gas Release in Several Configurations Varying the Height of the Release and the Geometry of the Enclosure
Sep 2013
Publication
The present work proposes a parametric study on the influence of the height of the release source on the helium dispersion regimes inside a naturally ventilated enclosure. Several configurations were experimentally addressed in order to improve knowledge on dispersion considering conditions close to hydrogen energy systems in terms of operating characteristics and design. Thus the varying parameters of the study were mainly the height of the release and also the releasing flow rate the volume and the geometry of the enclosure. Experimental results were compared to existing analytical models and considered through model improvements allowing a better approach of these specific cases for hydrogen systems risk assessment.
Simulation of the Efficiency of Hydrogen Recombiners as Safety Devices
Sep 2011
Publication
Passive auto-catalytic recombiners (PARs) are used as safety devices in the containments of nuclear power plants (NPPs) for the removal of hydrogen that may be generated during specific reactor accident scenarios. In the presented study it was investigated whether a PAR designed for hydrogen removal inside a NPP containment would perform principally inside a typical surrounding of hydrogen or fuel cell applications. For this purpose a hydrogen release scenario inside a garage – based on experiments performed by CEA in the GARAGE facility (France) – has been simulated with and without PAR installation. For modelling the operational behaviour of the PAR the in-house code REKO-DIREKT was implemented in the CFD code ANSYS-CFX. The study was performed in three steps: First a helium release scenario was simulated and validated against experimental data. Second helium was replaced by hydrogen in the simulation. This step served as a reference case for the unmitigated scenario. Finally the numerical garage setup was enhanced with a commercial PAR model. The study shows that the PAR works efficiently by removing hydrogen and promoting mixing inside the garage. The hot exhaust plume promotes the formation of a thermal stratification that pushes the initial hydrogen rich gas downwards and in direction of the PAR inlet. The paper describes the code implementation and simulation results.
No more items...