France
Numerical Simulations of Atmospheric Dispersion of Large-scale Liquid Hydrogen Releases
Sep 2021
Publication
Numerical simulations have been conducted for LH2 massive releases and the subsequent atmospheric dispersion using an in-house modified version of the open source computational fluid dynamics (CFD) code OpenFOAM. A conjugate heat transfer model has been added for heat transfer between the released LH2 and the ground. Appropriate interface boundary conditions are applied to ensure the continuities of temperature and heat fluxes. The significant temperature difference between the cryogenic hydrogen and the ground means that the released LH2 will instantly enter in a boiling state resulting in a hydrogen- air gaseous cloud which will initially behave like a dense gas. Numerical predictions have been conducted for the subsequent atmospheric dispersion of the vaporized LH2 for a series of release scenarios - with and without retention pits - to limit the horizontal spread of the LH2 on the ground. The considered cases included the instantaneous release of 1 10 and 50 tons of LH2 under neutral (D) and stable (F) weather conditions. More specifically 3F and 5D conditions were simulated with the former representing stable weather conditions under wind speed of 3 m/s at 10 m above the ground and the later corresponding to neutral weather conditions under 5 m/s wind speed (10 m above the ground). Specific numerical tests have also been conducted for selected scenarios under different ambient temperatures from 233 up to 313 K. According to the current study although the retention pit can extend the dispersion time it can significantly reduce the extent of hazards due to much smaller cloud size within both the flammability and explosion limits. While the former has negative impact on safety the later is beneficial. The use of retention pit should hence be considered with caution in practical applications.
Hydrogen-assisted Fatigue Crack Growth: Pre-charging vs In-situ Testing in Gaseous Environments
Mar 2023
Publication
We investigate the implications of conducting hydrogen-assisted fatigue crack growth experiments in a hydrogen gas environment (in-situ hydrogen charging) or in air (following exposure to hydrogen gas). The study is conducted on welded 42CrMo4 steel a primary candidate for the future hydrogen transport infrastructure allowing us to additionally gain insight into the differences in behavior between the base steel and the coarse grain heat affected zone. The results reveal significant differences between the two testing approaches and the two weld regions. The differences are particularly remarkable for the comparison of testing methodologies with fatigue crack growth rates being more than one order of magnitude higher over relevant loading regimes when the samples are tested in a hydrogen-containing environment relative to the pre-charged samples. Aided by finite element modelling and microscopy analysis these differences are discussed and rationalized. Independent of the testing approach the heat affected zone showed a higher susceptibility to hydrogen embrittlement. Similar microstructural behavior is observed for both testing approaches with the base metal exhibiting martensite lath decohesion while the heat affected zone experienced both martensite lath decohesion and intergranular fracture.
Proton Exchange Membrane Electrolyzer Emulator for Power Electronics Testing Applications
Mar 2021
Publication
This article aims to develop a proton exchange membrane (PEM) electrolyzer emulator. This emulator is realized through an equivalent electrical scheme. It allows taking into consideration the dynamic operation of PEM electrolyzers which is generally neglected in the literature. PEM electrolyzer dynamics are reproduced by the use of supercapacitors due to the high value of the equivalent double-layer capacitance value. Steady-state and dynamics operations are investigated in this work. The design criteria are addressed. The PEM electrolyzer emulator is validated by using a 400-W commercial PEM electrolyzer. This emulator is conceived to test new DC-DC converters to supply the PEM ELs and their control as well avoiding the risk to damage a real electrolyzer for experiment purposes. The proposed approach is valid both for a single cell and for the whole stack emulation.
Risk Assessment and Mitigation Evaluation for Hydrogen Vehicles in Private Garages. Experiments and Modelling
Sep 2021
Publication
Governments and local authorities introduce new incentives and regulations for cleaner mobility as part of their environmental strategies to address energy challenges. Fuel cell electric vehicles (FCEVs) are becoming increasingly important and will extend beyond captive fleets reaching private users. Research on hydrogen safety issues is currently led in several projects in order to highlight and manage risks of FCEVs in confined spaces such as tunnels underground parkings repair garages etc. But what about private garages - that involve specific geometries volumes congestion ventilation? This study has been carried out in the framework of PRHyVATE JIP project which aims at better understanding hydrogen build-up and distribution in a private garage. The investigation went through different rates and modes of ventilation. As first step an HAZID (Hazard Identification) has been realized for a generic FCEV. This preliminary work allowed to select and prioritize accidental release scenarios to be explored experimentally with helium in a 40-m3 garage. Several configurations of release ventilation modes and congestion – in transient regime and at steady state – have been tested. Then analytical and numerical calculation approaches have been applied and adjusted to develop a simplified methodology. This methodology takes into account natural ventilation for assessment of hydrogen accumulation and mitigation means optimization. Finally a global risk evaluation – including ignition of a flammable hydrogen-air mixture – has been performed to account for the mostly feared events and to evaluate their consequences in a private garage. Thus preliminary recommendations good practices and safety features for safely parking FCEVs in private garages can be proposed.
Impacts of Greenhouse Gas Neutrality Strategies on Gas Infrastructure and Costs: Implications from Case Studies Based on French and German GHG-neutral Scenarios
Sep 2022
Publication
The European Union’s target to reach greenhouse gas neutrality by 2050 calls for a sharp decrease in the consumption of natural gas. This study assesses impacts of greenhouse gas neutrality on the gas system taking France and Germany as two case studies which illustrate a wide range of potential developments within the European Union. Based on a review of French and German GHG-neutral scenarios it explores impacts on gas infrastructure and estimates the changes in end-user methane price considering a business-as-usual and an optimised infrastructure pathway. Our results show that gas supply and demand radically change by mid-century across various scenarios. Moreover the analysis suggests that deep transformations of the gas infrastructure are required and that according to the existing pricing mechanisms the end-user price of methane will increase driven by the switch to low-carbon gases and intensified by infrastructure costs.
Sizing of a Fuel Cell–battery Backup System for a University Building Based on the Probability of the Power Outages Length
Jul 2022
Publication
Hydrogen is a bright energy vector that could be crucial to decarbonise and combat climate change. This energy evolution involves several sectors including power backup systems to supply priority facility loads during power outages. As buildings now integrate complex automation domotics and security systems energy backup systems cause interest. A hydrogen-based backup system could supply loads in a multi-day blackout; however the backup system should be sized appropriately to ensure the survival of essential loads and low cost. In this sense this work proposes a sizing of fuel cell (FC) backup systems for low voltage (LV) buildings using the history of power outages. Historical data allows fitting a probability function to determine the appropriate survival of loads. The proposed sizing is applied to a university building with a photovoltaic generation system as a case study. Results show that the sizing of an FC–battery backup system for the installation is 7.6% cheaper than a battery-only system under a usual 330-minutes outage scenario. And 59.3% cheaper in the case of an unusual 48-hours outage scenario. It ensures a 99% probability of supplying essential load during power outages. It evidences the pertinence of an FC backup system to attend to outages of long-duration and the integration of batteries to support the abrupt load variations. This research is highlighted by using historical data from actual outages to define the survival of essential loads with total service probability. It also makes it possible to determine adequate survival for non-priority loads. The proposed sizing is generalisable and scalable for other buildings and allows quantifying the reliability of the backup system tending to the resilience of electrical systems.
The Vision of France, Germany, and the European Union on Future Hydrogen Energy Research and Innovation
Jul 2021
Publication
Hydrogen (H2) is an essential vector for freeing our societies from fossil fuels and effectively initiating the energy transition. Offering high energy density hydrogen can be used for mobile stationary or industrial applications of all sizes. This perspective on the crucial role of hydrogen is shared by a growing number of countries worldwide (e.g. China Germany Japan Republic of Korea Australia and United States) which are publishing ambitious roadmaps for the development of hydrogen and fuel cell technologies supported by substantial financial efforts.
Combustion Regimes of Hydrogen-air-steam Mixtures
Sep 2021
Publication
In the case of a severe nuclear power plant accident hydrogen gas formation may occur from the core degradation and cooling water evaporation and subsequent oxidation of zircaloy. These phenomena increase the risk of hazardous combustion events in the reactor especially when combined with an ignition source. If not handled carefully these types of accidents can cause severe damage to the reactor building with potential radioactive effects on the environment. Although hydrogen-air combustion has been investigated before hydrogen-air-steam mixtures remain unstudied under reactor-like conditions. Thus this study investigated such mixtures’ combustion regimes. A closed tube of 318 liters (7.65m tall and 0.23m inner diameter) measures the flame speed flame propagation and shock wave behaviors for 11-15 %vol hydrogen mixtures combined with 0 20 or 30 %vol steam and air. Thus both the effect of steam and hydrogen content was investigated and compared. The experimental setup combined photomultiplier tubes pressure sensors and shock detectors to give a full view of the different combustion regimes. A number of obstacles changed the in-chamber turbulence during flame propagation to provide further reactor-like environments. This changed turbulence affected the combustion regimes and enhanced the flame speed for some cases. The results showed varying combustion behaviors depending on the water vapor concentration where a higher concentration meant a lower flame speed reduced pressure load and sometimes combustion extinction. At 0 %vol steam dilution the flame speed remained supersonic for all H2 concentrations while at 30 %vol steam dilution the flame speed remained subsonic for all H2 concentrations. Thus with high levels of steam dilution the risk for shock waves leading to potential reactor building destruction decreases."
Hydrogen Energy Storage: New Techno-economic Emergence Solution Analysis
Aug 2015
Publication
The integration of various renewable energy sources as well as the liberalization of electricity markets are established facts in modern electrical power systems. The increased share of renewable sources within power systems intensifies the supply variability and intermittency. Therefore energy storage is deemed as one of the solutions for stabilizing the supply of electricity to maintain generation-demand balance and to guarantee uninterrupted supply of energy to users. In the context of sustainable development and energy resources depletion the question of the growth of renewable energy electricity production is highly linked to the ability to propose new and adapted energy storage solutions. The purpose of this multidisciplinary paper is to highlight the new hydrogen production and storage technology its efficiency and the impact of the policy context on its development. A comprehensive techno/socio/economic study of long term hydrogen based storage systems in electrical networks is addressed. The European policy concerning the different energy storage systems and hydrogen production is explicitly discussed. The state of the art of the techno-economic features of the hydrogen production and storage is introduced. Using Matlab-Simulink for a power system of rated 70 kW generator the excess produced hydrogen during high generation periods or low demand can be sold either directly to the grid owners or as filled hydrogen bottles. The affordable use of Hydrogen-based technologies for long term electricity storage is verified.
Improvement of SI Engine Combustion with Ammonia as Fuel: Effect of Ammonia Dissociation Prior to Combustion
Mar 2022
Publication
Although recent studies have shown the possibility of running ‘standard’ spark-ignition engines with 6 pure ammonia the operating range remains limited mainly due to the unfavorable characteristics of 7 ammonia for premixed combustion and often requires the addition of a complementary fuel such as H2 8 to extend it. As the best way to add H2 is to crack ammonia directly on-board this paper focuses on 9 the impact of the upstream cracking level of ammonia on the performance and emissions of a single 10 cylinder spark ignition engine. Experiments were performed over several equivalence ratios 11 dissociation rates and load conditions. It is confirmed that only a slight rate of ammonia dissociation 12 (10%) upstream of the combustion considerably enhances the engine's operating range thanks to a 13 better combustion stability. In terms of pollutant emissions the partial dissociation of ammonia 14 especially for slightly lean mixtures induces a very clear trade-off between high NOx and high 15 unburned ammonia level for high and low ammonia dissociation rates respectively. Therefore 16 cracking NH3 does not only improve the operating range of ammonia-fueled spark ignition engines but 17 can also help to reduce NH3. However to reach the same engine output work higher ammonia fuel 18 consumption will be necessary since the global system efficiency is lower using fuel dissociation. In 19 addition the global warming effect is increased with dissociation level since a higher level of N2O is 20 generated by the hydrogen contribution.
Optimal Multi-layer Economical Schedule for Coordinated Multiple Mode Operation of Wind-solar Microgrids with Hybrid Energy Storage Systems
Nov 2023
Publication
The aim of this paper is the design and implementation of an advanced model predictive control (MPC) strategy for the management of a wind–solar microgrid (MG) both in the islanded and grid-connected modes. The MG includes energy storage systems (ESSs) and interacts with external hydrogen and electricity consumers as an extra feature. The system participates in two different electricity markets i.e. the daily and real-time markets characterized by different time-scales. Thus a high-layer control (HLC) and a low-layer control (LLC) are developed for the daily market and the real-time market respectively. The sporadic characteristics of renewable energy sources and the variations in load demand are also briefly discussed by proposing a controller based on the stochastic MPC approach. Numerical simulations with real wind and solar generation profiles and spot prices show that the proposed controller optimally manages the ESSs even when there is a deviation between the predicted scenario determined at the HLC and the real-time one managed by the LLC. Finally the strategy is tested on a lab-scale MG set up at Khalifa University Abu Dhabi UAE.
Expert Perceptions of Game-changing Innovations towards Net Zero
Dec 2022
Publication
Current technological improvements are yet to put the world on track to net-zero which will require the uptake of transformative low-carbon innovations to supplement mitigation efforts. However the role of such innovations is not yet fully understood; some of these ‘miracles’ are considered indispensable to Paris Agreement-compliant mitigation but their limitations availability and potential remain a source of debate. We evaluate such potentially game-changing innovations from the experts’ perspective aiming to support the design of realistic decarbonisation scenarios and better-informed net-zero policy strategies. In a worldwide survey 260 climate and energy experts assessed transformative innovations against their mitigation potential at-scale availability and/or widescale adoption and risk of delayed diffusion. Hierarchical clustering and multi-criteria decision-making revealed differences in perceptions of core technological innovations with next generation energy storage alternative building materials iron-ore electrolysis and hydrogen in steelmaking emerging as top priorities. Instead technologies highly represented in well-below-2◦C scenarios seemingly feature considerable and impactful delays hinting at the need to re-evaluate their role in future pathways. Experts’ assessments appear to converge more on the potential role of other disruptive innovations including lifestyle shifts and alternative economic models indicating the importance of scenarios including non-technological and demand-side innovations. To provide insights for expert elicitation processes we finally note caveats related to the level of representativeness among the 260 engaged experts the level of their expertise that may have varied across the examined innovations and the potential for subjective interpretation to which the employed linguistic scales may be prone to.
An Insight into Underground Hydrogen Storage in Italy
Apr 2023
Publication
Hydrogen is a key energy carrier that could play a crucial role in the transition to a low-carbon economy. Hydrogen-related technologies are considered flexible solutions to support the large-scale implementation of intermittent energy supply from renewable sources by using renewable energy to generate green hydrogen during periods of low demand. Therefore a short-term increase in demand for hydrogen as an energy carrier and an increase in hydrogen production are expected to drive demand for large-scale storage facilities to ensure continuous availability. Owing to the large potential available storage space underground hydrogen storage offers a viable solution for the long-term storage of large amounts of energy. This study presents the results of a survey of potential underground hydrogen storage sites in Italy carried out within the H2020 EU Hystories “Hydrogen Storage In European Subsurface” project. The objective of this work was to clarify the feasibility of the implementation of large-scale storage of green hydrogen in depleted hydrocarbon fields and saline aquifers. By analysing publicly available data mainly well stratigraphy and logs we were able to identify onshore and offshore storage sites in Italy. The hydrogen storage capacity in depleted gas fields currently used for natural gas storage was estimated to be around 69.2 TWh.
Review on Ammonia as a Potential Fuel: From Synthesis to Economics
Feb 2021
Publication
Ammonia a molecule that is gaining more interest as a fueling vector has been considered as a candidate to power transport produce energy and support heating applications for decades. However the particular characteristics of the molecule always made it a chemical with low if any benefit once compared to conventional fossil fuels. Still the current need to decarbonize our economy makes the search of new methods crucial to use chemicals such as ammonia that can be produced and employed without incurring in the emission of carbon oxides. Therefore current efforts in this field are leading scientists industries and governments to seriously invest efforts in the development of holistic solutions capable of making ammonia a viable fuel for the transition toward a clean future. On that basis this review has approached the subject gathering inputs from scientists actively working on the topic. The review starts from the importance of ammonia as an energy vector moving through all of the steps in the production distribution utilization safety legal considerations and economic aspects of the use of such a molecule to support the future energy mix. Fundamentals of combustion and practical cases for the recovery of energy of ammonia are also addressed thus providing a complete view of what potentially could become a vector of crucial importance to the mitigation of carbon emissions. Different from other works this review seeks to provide a holistic perspective of ammonia as a chemical that presents benefits and constraints for storing energy from sustainable sources. State-of-the-art knowledge provided by academics actively engaged with the topic at various fronts also enables a clear vision of the progress in each of the branches of ammonia as an energy carrier. Further the fundamental boundaries of the use of the molecule are expanded to real technical issues for all potential technologies capable of using it for energy purposes legal barriers that will be faced to achieve its deployment safety and environmental considerations that impose a critical aspect for acceptance and wellbeing and economic implications for the use of ammonia across all aspects approached for the production and implementation of this chemical as a fueling source. Herein this work sets the principles research practicalities and future views of a transition toward a future where ammonia will be a major energy player.
A Comparative Study on Energy Efficiency of the Maritime Supply Chains for Liquefied Hydrogen, Ammonia, Methanol and Natural Gas
Jun 2023
Publication
To cope with climate change emerging fuels- hydrogen ammonia and methanol- have been proposed as promising energy carriers that will replace part of the liquefied natural gas (LNG) in future maritime scenarios. Energy efficiency is an important indicator for evaluating the system but the maritime supply system for emerging fuels has yet to be revealed. In this study the energy efficiency of the maritime supply chain of hydrogen ammonia methanol and natural gas is investigated considering processes including production storage loading transport and unloading. A sensitivity analysis of parameters such as ambient temperature storage time pipeline length and sailing time is also carried out. The results show that hydrogen (2.366%) has the highest daily boil-off gas (BOG) rate and wastes more energy than LNG (0.413%) with ammonia and methanol both being lower than LNG. The recycling of BOG is of great importance to the hydrogen supply chain. When produced from renewable energy sources methanol (98.02%) is the most energy efficient followed by ammonia with hydrogen being the least (89.10%). This assessment shows from an energy efficiency perspective that ammonia and methanol have the potential to replace LNG as the energy carrier of the future and that hydrogen requires efficient BOG handling systems to increase competitiveness. This study provides some inspirations for the design of global maritime supply systems for emerging fuels.
Assessing and Modelling Hydrogen Reactivity in Underground Hydrogen Storage: A Review and Models Simulating the Lobodice Town Gas Storage
Apr 2023
Publication
Underground Hydrogen storage (UHS) is a promising technology for safe storage of large quantities of hydrogen in daily to seasonal cycles depending on the consumption requirements. The development of UHS requires anticipating hydrogen behavior to prevent any unexpected economic or environmental impact. An open question is the hydrogen reactivity in underground porous media storages. Indeed there is no consensus on the effects or lack of geochemical reactions in UHS operations because of the strong coupling with the activity of microbes using hydrogen as electron donor during anaerobic reduction reactions. In this work we apply different geochemical models to abiotic conditions or including the catalytic effect of bacterial activity in methanogenesis acetogenesis and sulfate-reduction reactions. The models are applied to Lobodice town gas storage (Czech Republic) where a conversion of hydrogen to methane was measured during seasonal gas storage. Under abiotic conditions no reaction is simulated. When the classical thermodynamic approach for aqueous redox reactions is applied the simulated reactivity of hydrogen is too high. The proper way to simulate hydrogen reactivity must include a description of the kinetics of the aqueous redox reactions. Two models are applied to simulate the reactions of hydrogen observed at Lobodice gas storage. One modeling the microbial activity by applying energy threshold limitations and another where microbial activity follows a Monod-type rate law. After successfully calibrating the bio-geochemical models for hydrogen reactivity on existing gas storage data and constraining the conditions where microbial activity will inhibit or enhance hydrogen reactivity we now have a higher confidence in assessing the hydrogen reactivity in future UHS in aquifers or depleted reservoirs.
Renewable Hydrogen Production Processes for the Off-Gas Valorization in Integrated Steelworks through Hydrogen Intensified Methane and Methanol Syntheses
Nov 2020
Publication
Within integrated steelmaking industries significant research efforts are devoted to the efficient use of resources and the reduction of CO2 emissions. Integrated steelworks consume a considerable quantity of raw materials and produce a high amount of by-products such as off-gases currently used for the internal production of heat steam or electricity. These off-gases can be further valorized as feedstock for methane and methanol syntheses but their hydrogen content is often inadequate to reach high conversions in synthesis processes. The addition of hydrogen is fundamental and a suitable hydrogen production process must be selected to obtain advantages in process economy and sustainability. This paper presents a comparative analysis of different hydrogen production processes from renewable energy namely polymer electrolyte membrane electrolysis solid oxide electrolyze cell electrolysis and biomass gasification. Aspen Plus® V11-based models were developed and simulations were conducted for sensitivity analyses to acquire useful information related to the process behavior. Advantages and disadvantages for each considered process were highlighted. In addition the integration of the analyzed hydrogen production methods with methane and methanol syntheses is analyzed through further Aspen Plus®-based simulations. The pros and cons of the different hydrogen production options coupled with methane and methanol syntheses included in steelmaking industries are analyzed
Identifying Social Aspect Related to the Hydrogen Economy: Review, Synthesis, and Research Perspectives
Oct 2023
Publication
Energy transition will reshape the power sector and hydrogen is a key energy carrier that could contribute to energy security. The inclusion of sustainability criteria is crucial for the adequate design/deployment of resilient hydrogen networks. While cost and environmental metrics are commonly included in hydrogen models social aspects are rarely considered. This paper aims to identify the social criteria related to the hydrogen economy by using a systematic hybrid literature review. The main contribution is the identification of twelve social aspects which are described ranked and discussed. “Accessibility” “Information” “H2 markets” and “Acceptability” are now emerging as the main themes of hydrogen-related social research. Identified gaps are e.g. lack of the definition of the value of H2 for society insufficient research for “socio-political” aspects (e.g. geopolitics wellbeing) scarce application of social lifecycle assessment and the low amount of works with a focus on social practices and cultural issues.
Hydrogen Refuelling Station Calibration with a Traceable Gravimetric Standard
Apr 2020
Publication
Of all the alternatives to hydrocarbon fuels hydrogen offers the greatest long-term potential to radically reduce the many problems inherent in fuel used for transportation. Hydrogen vehicles have zero tailpipe emissions and are very efficient. If the hydrogen is made from renewable sources such as nuclear power or fossil sources with carbon emissions captured and sequestered hydrogen use on a global scale would produce almost zero greenhouse gas emissions and greatly reduce air pollutant emissions. The aim of this work is to realise a traceability chain for hydrogen flow metering in the range typical for fuelling applications in a wide pressure range with pressures up to 875 bar (for Hydrogen Refuelling Station - HRS with Nominal Working Pressure of 700 bar) and temperature changes from −40 °C (pre-cooling) to 85 °C (maximum allowed vehicle tank temperature) in accordance with the worldwide accepted standard SAE J2601. Several HRS have been tested in Europe (France Netherlands and Germany) and the results show a good repeatability for all tests. This demonstrates that the testing equipment works well in real conditions. Depending on the installation configuration some systematic errors have been detected and explained. Errors observed for Configuration 1 stations can be explained by pressure differences at the beginning and end of fueling in the piping between the Coriolis Flow Meter (CFM) and the dispenser: the longer the distance the bigger the errors. For Configuration 2 where this distance is very short the error is negligible.
THyGA - Roadmap H2NG for Europe
May 2023
Publication
This report aims at summarizing the different stakeholders’ opinions on H2NG blends and cross them with the THyGA results to recommend some necessary actions to prepare the field for operational large-scale blending (liability delayed ignition adjustment…).
No more items...