Germany
Hydrogen-related Challenges for the Steelmaker: The Search for Proper Testing
Jun 2017
Publication
The modern steelmaker of advanced high-strength steels has always been challenged with the conflicting targets of increased strength while maintaining or improving ductility. These new steels help the transportation sector including the automotive sector to achieve the goals of increased passenger safety and reduced emissions. With increasing tensile strengths certain steels exhibit an increased sensitivity towards hydrogen embrittlement (HE). The ability to characterize the material's sensitivity in an as-delivered condition has been developed and accepted (SEP1970) but the complexity of the stress states that can induce an embrittlement together with the wide range of applications for high-strength steels make the development of a standardized test for HE under in-service conditions extremely challenging. Some proposals for evaluating the material's sensitivity give an advantage to materials with a low starting ductility. Despite this newly developed materials can have a higher original elongation with only a moderate reduction in elongation due to hydrogen. This work presents a characterization of new materials and their sensitivity towards HE.
This article is part of the themed issue ‘The challenges of hydrogen and metals’.
Link to document download on Royal Society Website
This article is part of the themed issue ‘The challenges of hydrogen and metals’.
Link to document download on Royal Society Website
Numerical study of the release and dispersion of a light gas using 3D CFD code GASFLOW-MPI
Sep 2017
Publication
With the development of the hydrogen economy it requires a better understanding of the potential for fires and explosions associated with the unintended release of hydrogen within a partially confined space. In order to mitigate the hydrogen fire and explosion risks effectively accurate predictions of the hydrogen transport and mixing processes are crucial. It is well known that turbulence modelling is one of the key elements for a successful simulation of gas mixing and transport. GASFLOW-MPI is a scalable CFD software solution used to predict fluid dynamics conjugate heat and mass transfer chemical kinetics aerosol transportation and other related phenomena. In order to capture more turbulence information the Large Eddy Simulation (LES) model and LES/RANS hybrid model Detached Eddy Simulation (DES) have been implemented and validated in 3-D CFD code GASFLOW-MPI. The standard Smagorisky SGS model is utilized in LES turbulence model. And the k-epsilon based DES model is employed. This paper assesses the capability of algebraic k-epsilon DES and LES turbulence model to simulate the mixing and transport behavior of highly buoyant gases in a partially confined geometry. Simulation results agree well with the overall trend measured in experiments conducted in a reduced scale enclosure with idealized leaks which shows that all these four turbulent models are validated and suitable for the simulation of light gas behavior. Furthermore the numerical results also indicate that the LES and DES model could be used to analysis the turbulence behavior in the hydrogen safety problems.
Review of Power-to-Gas Projects in Europe
Nov 2018
Publication
Core of the Power-to-Gas (PtG) concept is the utilization of renewable electricity to produce hydrogen via water electrolysis. This hydrogen can be used directly as final energy carrier or can be converted to e.g. methane synthesis gas liquid fuels electricity or chemicals. To integrate PtG into energy systems technical demonstration and systems integration is of mayor importance. In total 128 PtG research and demonstration projects are realized or already finished in Europe to analyze these issues by May 2018. Key of the review is the identification and assessment of relevant projects regarding their field of application applied processes and technologies for electrolysis type of methanation capacity location and year of commissioning. So far main application for PtX is the injection of hydrogen or methane into the natural gas grid for storing electricity from variable renewable energy sources. Producing fuels for transport is another important application of PtX. In future PtX gets more important for refineries to lower the carbon food print of the products.
Experimental Investigation of Unconfined Spherical and Cylindrical Flame Propagation in Hydrogen-air Mixtures
Sep 2019
Publication
This paper presents results of experimental investigations on spherical and cylindrical flame propagation in pre-mixed H2/air-mixtures in unconfined and semi-confined geometries. The experiments were performed in a facility consisting of two transparent solid walls with 1 m2 area and four weak side walls made from thin plastic film. The gap size between the solid walls was varied stepwise from thin layer geometry (6 mm) to cube geometry (1 m). A wide range of H2/air-mixtures with volumetric hydrogen concentrations from 10% to 45% H2 was ignited between the transparent solid walls. The propagating flame front and its structure was observed with a large scale high speed shadow system. Results of spherical and cylindrical flame propagation up to a radius of 0.5 m were analyzed. The presented spherical burning velocity model is used to discuss the self-acceleration phenomena in unconfined and unobstructed pre-mixed H2/air flames.
Hydrogen Embrittlement: The Game Changing Factor in the Applicability of Nickel Alloys in Oilfield Technology
Jun 2017
Publication
Precipitation hardenable (PH) nickel (Ni) alloys are often the most reliable engineering materials for demanding oilfield upstream and subsea applications especially in deep sour wells. Despite their superior corrosion resistance and mechanical properties over a broad range of temperatures the applicability of PH Ni alloys has been questioned due to their susceptibility to hydrogen embrittlement (HE) as confirmed in documented failures of components in upstream applications. While extensive work has been done in recent years to develop testing methodologies for benchmarking PH Ni alloys in terms of their HE susceptibility limited scientific research has been conducted to achieve improved foundational knowledge about the role of microstructural particularities in these alloys on their mechanical behaviour in environments promoting hydrogen uptake. Precipitates such as the γ′ γ′′ and δ-phase are well known for defining the mechanical and chemical properties of these alloys. To elucidate the effect of precipitates in the microstructure of the oil-patch PH Ni alloy 718 on its HE susceptibility slow strain rate tests under continuous hydrogen charging were conducted on material after several different age-hardening treatments. By correlating the obtained results with those from the microstructural and fractographic characterization it was concluded that HE susceptibility of oil-patch alloy 718 is strongly influenced by the amount and size of precipitates such as the γ′ and γ′′ as well as the δ-phase rather than by the strength level only. In addition several HE mechanisms including hydrogen-enhanced decohesion and hydrogen-enhanced local plasticity were observed taking place on oil-patch alloy 718 depending upon the characteristics of these phases when present in the microstructure.
Link to document download on Royal Society Website
Link to document download on Royal Society Website
Initial Assessment of a Fuel Cell—Gas Turbine Hybrid Propulsion Concept
Jan 2022
Publication
A fuel cell—gas turbine hybrid propulsion concept is introduced and initially assessed. The concept uses the water mass flow produced by a hydrogen fuel cell in order to improve the efficiency and power output of the gas turbine engine through burner steam injection. Therefore the fuel cell product water is conditioned through a process of condensation pressurization and revaporization. The vaporization uses the waste heat of the gas turbine exhaust. The functional principles of the system concept are introduced and discussed and appropriate methodology for an initial concept evaluation is formulated. Essential technology fields are surveyed in brief. The impact of burner steam injection on gas turbine efficiency and sizing is parametrically modelled. Simplified parametric models of the fuel cell system and key components of the water treatment process are presented. Fuel cell stack efficiency and specific power levels are methodically derived from latest experimental studies at the laboratory scale. The overall concept is assessed for a liquid hydrogen fueled short-/medium range aircraft application. Block fuel savings of up to 7.1% are found for an optimum design case based on solid oxide fuel cell technology. The optimum design features a gas turbine water-to-air ratio of 6.1% in cruise and 62% reduced high-level NOx emissions.
Sector Coupling Potential of Wind-based Hydrogen Production and Fuel Cell Train Operation in Regional Rail Transport in Berlin and Brandenburg
Jan 2021
Publication
As the transport sector is ought to be decarbonized fuel-cell-powered trains are a viable zero-tailpipe technology alternative to the widely employed diesel multiple units in regional railway service on non-electrified tracks. Carbon-free hydrogen can be provided by water-electrolysis from renewable energies. In this study we introduce an approach to assess the potential of wind-based hydrogen for use in adjacent regional rail transport by applying a GIS approach in conjunction with a site-level cost model. In Brandenburg about 10.1 million train-km annually could be switched to fuel cell electric train operation. This relates to a diesel consumption of appr. 9.5 million liters today. If fuel cell trains would be employed that translated to 2198 annual tons hydrogen annually. At favorable sites hydrogen costs of approx. 6.40 €/kg - including costs of hydrogen refueling stations - could be achieved. Making excess hydrogen available for other consumers would further decrease hydrogen production costs.
Hydrogen Refueling Station Networks for Heavy-duty Vehicles in Future Power Systems
May 2020
Publication
A potential solution to reduce greenhouse gas (GHG) emissions in the transport sector is to use alternatively fuelled vehicles (AFV). Heavy-duty vehicles (HDV) emit a large share of GHG emissions in the transport sector and are therefore the subject of growing attention from global regulators. Fuel cell and green hydrogen technologies are a promising option to decarbonize HDVs as their fast refuelling and long vehicle ranges are consistent with current logistic operational requirements. Moreover the application of green hydrogen in transport could enable more effective integration of renewable energies (RE) across different energy sectors. This paper explores the interplay between HDV Hydrogen Refuelling Stations (HRS) that produce hydrogen locally and the power system by combining an infrastructure location planning model and an electricity system optimization model that takes grid expansion options into account. Two scenarios – one sizing refuelling stations to support the power system and one sizing them independently of it – are assessed regarding their impacts on the total annual electricity system costs regional RE integration and the levelized cost of hydrogen (LCOH). The impacts are calculated based on locational marginal pricing for 2050. Depending on the integration scenario we find average LCOH of between 4.83 euro/kg and 5.36 euro/kg for which nodal electricity prices are the main determining factor as well as a strong difference in LCOH between north and south Germany. Adding HDV-HRS incurs power transmission expansion as well as higher power supply costs as the total power demand increases. From a system perspective investing in HDV-HRS in symbiosis with the power system rather than independently promises cost savings of around seven billion euros per annum. We therefore conclude that the co-optimization of multiple energy sectors is important for investment planning and has the potential to exploit synergies.
Expected Impacts on Greenhouse Gas and Air Pollutant Emissions Due to a Possible Transition Towards a Hydrogen Economy in German Road Transport
Nov 2020
Publication
Transitioning German road transport partially to hydrogen energy is among the possibilities being discussed to help meet national climate targets. This study investigates impacts of a hypothetical complete transition from conventionally-fuelled to hydrogen-powered German transport through representative scenarios. Our results show that German emissions change between −179 and +95 MtCO2eq annually depending on the scenario with renewable-powered electrolysis leading to the greatest emissions reduction while electrolysis using the fossil-intense current electricity mix leads to the greatest increase. German energy emissions of regulated pollutants decrease significantly indicating the potential for simultaneous air quality improvements. Vehicular hydrogen demand is 1000 PJ annually requiring 446–525 TWh for electrolysis hydrogen transport and storage which could be supplied by future German renewable generation supporting the potential for CO2-free hydrogen traffic and increased energy security. Thus hydrogen-powered transport could contribute significantly to climate and air quality goals warranting further research and political discussion about this possibility.
Multistage Risk Analysis and Safety Study of a Hydrogen Energy Station
Sep 2017
Publication
China has plenty of renewable energy like wind power and solar energy especially in the northwest part of the country. Due to the volatile and intermittent characters of the green powers high penetration level of renewable resources could arise grid stabilization problem. Therefore electricity storage is considered as a solution and hydrogen energy storage is proposed. Instead of storing the electricity directly it converts electricity into hydrogen and the energy in hydrogen will be released as needed from gas to electricity and heat. The transformed green power can be fed to the power grid and heat supply network. State Grid Corporation of China carried out its first hydrogen demonstration project. In the demonstration project an alkaline electrolyzer and a PEM hydrogen fuel cell stack are decided as the hydrogen producer and consumer respectively. Hydrogen safety issue is always of significant importance to secure the property. In order to develop a dedicated safety analysis method for hydrogen energy storage system in power industry the risk analysis for the power-to-gas-topower&heat facility was made. The hazard and operability (HAZOP) study and the failure mode and effects analysis (FMEA) are performed sequentially to the installation to identify the most problematic parts of the system in view of hydrogen safety and possible failure modes and consequences. At the third step the typical hydrogen leak accident scenarios are simulated by using computational fluid dynamics (CFD) computer code. The resulted pressure loads of the possibly ignited hydrogen-air mixture in the facility container are estimated conservatively. Important safeguards and mitigation measures are proposed based on the three-stage risk and safety studies.
Mineral Reactions in the Geological Underground Induced by H2 and CO2 Injections
Dec 2014
Publication
The R&D project H2STORE is part of the German program to reduce environmental pollution by energy production and in saving fossil natural resources. Thereby physico-chemical processes in the CO2-H2 system by organic and inorganic reactions receive increasing attention. In H2STORE siliciclastic reservoirs and their caprocks from 25 well sites in Germany and Austria are investigated by different analytical methods before and after H2/CO2 batch experiments under sample specific reservoir conditions (p T XFluid). Mineral dissolution precipitation and their impact on reservoir quality (poro-perm fluid pathways) and on the generation of methane by microbial metabolism triggered by CO2/H2 exposure are studied.
Comparative Life Cycle Assessment of Battery and Fuel Cell Electric Cars, Trucks, and Buses
Mar 2024
Publication
Addressing the pressing challenge of global warming reducing greenhouse gas emissions in the transportation sector is a critical imperative. Battery and fuel cell electric vehicles have emerged as promising solutions for curbing emissions in this sector. In this study we conducted a comprehensive life cycle assessment (LCA) for typical passenger vehicles heavy-duty trucks and city buses using either proton-exchange membrane fuel cells or Li-ion batteries with different cell chemistries. To ensure accuracy we supplemented existing studies with data from the literature particularly for the recycling phase as database limitations were encountered. Our results highlight that fuel cell and battery systems exhibit large emissions in the production phase. Recycling can significantly offset some of these emissions but a comparison of the technologies examined revealed considerable differences. Overall battery electric vehicles consistently outperform fuel cell electric vehicles regarding absolute greenhouse gas emissions. Hence we recommend prioritizing battery electric over fuel cell vehicles. However deploying fuel cell electric vehicles could become attractive in a hydrogen economy scenario where other factors e. g. the conversion and storage of surplus renewable electricity via electrolysis become important.
Investigation on Cooling Effect of Water Sprays on Tunnel Fires of Hydrogen
Sep 2021
Publication
As one of the most promising renewable green energies hydrogen power is a popularly accepted option to drive automobiles. Commercial application of fuel cell vehicles has been started since 2015. More and more hydrogen safety concerns have been considered for years. Tunnels are an important part of traffic infrastructure with a mostly confined feature. Hydrogen leak followed possibly by a hydrogen fire is a potential accident scenario which can be triggered trivially by a car accident while hydrogen powered vehicles operate in a tunnel. Water spray is recommended traditionally as a mitigation measure against tunnel fires. The interaction between water spray and hydrogen fire is studied in a way of numerical simulations. By using the computer program of Fire Dynamics Simulator (FDS) tunnel fires of released hydrogen in different scales are simulated coupled with water droplet injections featured in different droplet sizes or varying mass flow rates. The cooling effect of spray on hot gases of hydrogen fires is apparently observed in the simulations. However in some circumstance the turbulence intensified by the water injection can prompt hydrogen combustion which is a negative side-effect of the spray.
Shock Tube Experiments on Flame Propagation Regimes and Critical Conditions for Flame Acceleration and Detonation Transition for Hydrogen-air Mixtures at Cryogenic Temperatures
Sep 2021
Publication
A series of more than 100 experiments with hydrogen-air mixtures at cryogenic temperatures have been performed in a shock tube in the frame of the PRESLHY project. A wide range of hydrogen concentrations from 8 to 60%H2 in the shock tube of the length of 5 m and 50 mm id was tested at cryogenic temperatures from 80 to 130K at ambient pressure. Flame propagation regimes were investigated for all hydrogen compositions in the shock tube at three different blockage ratios (BR) 0 0.3 and 0.6 as a function of initial temperature. Pressure sensors and InGaAs-photodiodes have been applied to monitor the flame and shock propagation velocity of the process. The experiments at ambient pressure and temperature were conducted as the reference data for cryogenic experiments. A critical expansion ratio for an effective flame acceleration to the speed of sound was experimentally found at cryogenic temperatures. The detonability criterion for smooth and obstructed channels was used to evaluate the detonation cell sizes at cryogenic temperatures as well. The main peculiarities of cryogenic combustion with respect to the safety assessment were that the maximum combustion pressure was several times higher compared to ambient temperature and the run-up-distance to detonation was several times shorter independent of lower chemical reactivity at cryogenic conditions.
Green Hydrogen in Europe: Do Strategies Meet Expectations?
Dec 2021
Publication
The possibility of producing hydrogen as an energy carrier or raw material through electrolysis of water so-called green hydrogen has been on the table as a technological option for a long time. However low conversion efficiency and a dubious climate balance have stood in the way of large-scale application ever since. Within the last three to four years however this view has changed significantly. In addition to technological improvements the increasing speed of the expansion of volatile renewable energies in Europe has also contributed to this since in principle a nearly climate-neutral utilisation of excess generation is possible through the use of hydrogen as an energy carrier in electrolysis. In addition hydrogen or products derived from it can be used in a variety of ways as a final energy carrier in all energy-intensive activities: industry heating and transport. For this reason green hydrogen production could play a key role in interconnecting all energy consuming sectors (sector coupling) a long-term goal necessary for achieving the decarbonisation of the European economy.
Pneumatic and Optical Characterization and Optimization of Hydrogen Injectors for Internal Combustion Engine Application
Aug 2022
Publication
To achieve future emission targets for internal combustion engines the use of hydrogen gas generated by renewable energy sources (known as “green” hydrogen) instead of fossil fuels plays a key role in the development of new combustion-based engine concepts. For new hydrogen engine generations there are different challenges concerning the injector layout and functionality. Especially when talking about direct hydrogen injection the key challenge is to ensure a proper mixing between hydrogen and the combustion air—the mixing of gas with a gas is not trivial as shown in this article. In terms of injector functionality it must be ensured that the requested amount of hydrogen gas needs to be provided in time and on the other hand accurately metered to provide an appropriate mixing formation quality inside the combustion chamber. This contribution discusses deep injector analysis techniques with pneumatic and optical approaches for an improved overall understanding of functionality and effects caused by operation with a gaseous fuel. A metering technique for gas flow characterization and for test simplification a comparison of hydrogen with helium and nitrogen as possible surrogate gases indicate that helium and nitrogen can act as a substitute for hydrogen in functional testing. Furthermore this contribution focuses on the usability of helium instead of hydrogen for the determination of spray properties. This is shown by the comparison of spray propagation images that were observed with the Schlieren technique in a pressure vessel proving comparable spray properties. In a next step the usage of spray-guiding devices to improve the global gas distribution during the injection period is discussed. Here it turns out that the volume increase does obviously not depend on the nozzle design. Thus the advantage of multi-hole guiding-devices is based on its flexible gas-jet orientation.
Ecological and Economic Evaluation of Hydrogen Production by Different Water Electrolysis Technologies
Jul 2020
Publication
The economic and ecological production of green hydrogen by water electrolysis is one of the major challenges within Carbon2Chem and other power-to-X projects. This paper presents an evaluation of the different water electrolysis technologies with respect to their specific energy demand carbon footprint and the forecast production costs in 2030. From a current perspective alkaline water electrolysis is evaluated as the most favorable technology for the cost-effective production of low-carbon hydrogen with fluctuating renewables.
Determining the Production and Transport Cost for H2 on a Global Scale
May 2022
Publication
Hydrogen (H2) produced using renewable energy could be used to reduce greenhouse gas (GHG) emissions in industrial sectors such as steel chemicals transportation and energy storage. Knowing the delivered cost of renewable H2 is essential to decisionmakers looking to utilize it. The cheapest location to source it from as well as the transport method and medium are also crucial information. This study presents a Monte Carlo simulation to determine the delivered cost for renewable H2 for any usage location globally as well as the most cost-effective production location and transport route from nearly 6000 global locations. Several industrially dense locations are selected for case studies the primary two being Cologne Germany and Houston United States. The minimum delivered H2 cost to Cologne is 9.4 €/kg for small scale (no pipelines considered) shipped from northern Egypt as a liquid organic hydrogen carrier (LOHC) and 7.6 €/kg piped directly as H2 gas from southern France for large scale (pipelines considered). For smallscale H2 in Houston the minimum delivered cost is 8.6 €/kg trucked as H2 gas from the western Gulf of Mexico and 7.6 €/kg for large-scale demand piped as H2 gas from southern California. The south-west United States and Mexico northern Chile the Middle East and north Africa south-west Africa and north-west Australia are identified as the regions with the lowest renewable H2 cost potential with production costs ranging from 6.7—7.8 €/kg in these regions. Each is able to supply differing industrially dominant areas. Furthermore the effect of parameters such as year of construction electrolyser and H2 demand is analysed. For the case studies in Houston and Cologne the delivered H2 cost is expected to reduce to about 7.8 €/kg by 2050 in Cologne (no pipelines considered PEM electrolyser) and 6.8 €/kg in Houston.
Fundamentals, Materials, and Machine Learning of Polymer Electrolyte Membrane Fuel Cell Technology
Jun 2020
Publication
Polymer electrolyte membrane (PEM) fuel cells are electrochemical devices that directly convert the chemical energy stored in fuel into electrical energy with a practical conversion efficiency as high as 65%. In the past years significant progress has been made in PEM fuel cell commercialization. By 2019 there were over 19000 fuel cell electric vehicles (FCEV) and 340 hydrogen refueling stations (HRF) in the U.S. (~8000 and 44 respectively) Japan (~3600 and 112 respectively) South Korea (~5000 and 34 respectively) Europe (~2500 and 140 respectively) and China (~110 and 12 respectively). Japan South Korea and China plan to build approximately 3000 HRF stations by 2030. In 2019 Hyundai Nexo and Toyota Mirai accounted for approximately 63% and 32% of the total sales with a driving range of 380 and 312 miles and a mile per gallon (MPGe) of 65 and 67 respectively. Fundamentals of PEM fuel cells play a crucial role in the technological advancement to improve fuel cell performance/durability and reduce cost. Several key aspects for fuel cell design operational control and material development such as durability electrocatalyst materials water and thermal management dynamic operation and cold start are briefly explained in this work. Machine learning and artificial intelligence (AI) have received increasing attention in material/energy development. This review also discusses their applications and potential in the development of fundamental knowledge and correlations material selection and improvement cell design and optimization system control power management and monitoring of operation health for PEM fuel cells along with main physics in PEM fuel cells for physics-informed machine learning. The objective of this review is three fold: (1) to present the most recent status of PEM fuel cell applications in the portable stationary and transportation sectors; (2) to describe the important fundamentals for the further advancement of fuel cell technology in terms of design and control optimization cost reduction and durability improvement; and (3) to explain machine learning physics-informed deep learning and AI methods and describe their significant potentials in PEM fuel cell research and development (R&D).
Water Electrolysis: From Textbook Knowledge to the Latest Scientific Strategies and Industrial Developments
May 2022
Publication
Replacing fossil fuels with energy sources and carriers that are sustainable environmentally benign and affordable is amongst the most pressing challenges for future socio-economic development. To that goal hydrogen is presumed to be the most promising energy carrier. Electrocatalytic water splitting if driven by green electricity would provide hydrogen with minimal CO2 footprint. The viability of water electrolysis still hinges on the availability of durable earth-abundant electrocatalyst materials and the overall process efficiency. This review spans from the fundamentals of electrocatalytically initiated water splitting to the very latest scientific findings from university and institutional research also covering specifications and special features of the current industrial processes and those processes currently being tested in large-scale applications. Recently developed strategies are described for the optimisation and discovery of active and durable materials for electrodes that ever-increasingly harness first principles calculations and machine learning. In addition a technoeconomic analysis of water electrolysis is included that allows an assessment of the extent to which a large-scale implementation of water splitting can help to combat climate change. This review article is intended to cross-pollinate and strengthen efforts from fundamental understanding to technical implementation and to improve the ‘junctions’ between the field’s physical chemists materials scientists and engineers as well as stimulate much-needed exchange among these groups on challenges encountered in the different domains.
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