Germany
Numerical Study on Shockwave Attenuation by Water Mist in Confined Spaces
Sep 2021
Publication
Hydrogen safety has become the first consideration especially after fuel cell automobiles were pushed into commercial auto market. Tunnels are important parts of traffic infrastructure featured in confinement or semi-confinement. Hydrogen detonation is a potential accident scenario while hydrogen fuel cell vehicles are operated in a traffic tunnel with a confined space. Pressure shockwaves are mostly produced by hydrogen detonation and propagate along the tunnel. As a designed safety measure water mist injection is hopefully to mitigate the pressure loads of such shocks. To model the interaction between shockwaves and water droplets a droplet breakup model has been developed for the COM3D code which is a highly validated three-dimensional hydrogen explosion simulation code. By using the model the hydrogen detonation shockwave propagation in confined volumes is simulated in the study. The attenuation effects of water mist on the pressure shocks in the simulations are elaborated and discussed based on the simulation results.
Current Legislative Framework for Green Hydrogen Production by Electrolysis Plants in Germany
Mar 2022
Publication
(1) The German energy system transformation towards an entirely renewable supply is expected to incorporate the extensive use of green hydrogen. This carbon-free fuel allows the decarbonization of end-use sectors such as industrial high-temperature processes or heavy-duty transport that remain challenging to be covered by green electricity only. However it remains unclear whether the current legislative framework supports green hydrogen production or is an obstacle to its rollout. (2) This work analyzes the relevant laws and ordinances regarding their implications on potential hydrogen production plant operators. (3) Due to unbundling-related constraints potential operators from the group of electricity transport system and distribution system operators face lacking permission to operate production plants. Moreover ownership remains forbidden for them. The same applies to natural gas transport system operators. The case is less clear for natural gas distribution system operators where explicit regulation is missing. (4) It is finally analyzed if the production of green hydrogen is currently supported in competition with fossil hydrogen production not only by the legal framework but also by the National Hydrogen Strategy and the Amendment of the Renewable Energies Act. It can be concluded that in recent amendments of German energy legislation regulatory support for green hydrogen in Germany was found. The latest legislation has clarified crucial points concerning the ownership and operation of electrolyzers and the treatment of green hydrogen as a renewable energy carrier.
Storage System of Renewable Energy Generated Hydrogen for Chemical Industry
Nov 2012
Publication
Chemical industry is the base of the value chains and has strong influence on the competitiveness of almost all branches in economics. To develop the technologies for sustainability and climate protection and at the same time to guarantee the supply of raw material is a big challenge for chemical industry. In the project CO2RRECT (CO2 - Reaction using Regenerative Energies and Catalytic Technologies) funded by the German federal ministry of Education and Research carbon dioxide is used as the source of carbon for chemical products with certain chemical processes. Hydrogen that is needed in these processes is produced by electrolyzing water with renewable energy. To store a large amount of hydrogen different storage systems are studied in this project including liquid hydrogen tanks/cryo tanks high pressure tanks pipelines and salt cavities. These systems are analyzed and compared considering their storage capacity system costs advantages and disadvantages. To analyze capital and operational expenditure of the hydrogen storage systems a calculation methodology is also developed in this work.
System Analysis and Requirements Derivation of a Hydrogen-electric Aircraft Powertrain
Sep 2022
Publication
In contrast to sustainable aviation fuels for use in conventional combustion engines hydrogen-electric powertrains constitute a fundamentally novel approach that requires extensive effort from various engineering disciplines. A transient system analysis has been applied to a 500 kW shaft-power-class powertrain. The model was fed with high-level system requirements to gain a fundamental understanding of the interaction between sub-systems and components. Transient effects such as delays in pressure build up heat transfer and valve operation substantially impact the safe and continuous operation of the propulsion system throughout a typical mission profile which is based on the Daher TBM850. The lumped-parameters network solver provides results quickly which are used to derive requirements for subsystems and components which support their in-depth future development. E.g. heat exchanger transfer rates and pressure drop of the motor's novel hydrogen cooling system are established. Furthermore improvements to the system architecture such as a compartmentalization of the tank are identified.
Ammonia Production from Clean Hydrogen and the Implications for Global Natural Gas Demand
Jan 2023
Publication
Non-energy use of natural gas is gaining importance. Gas used for 183 million tons annual ammonia production represents 4% of total global gas supply. 1.5-degree pathways estimate an ammonia demand growth of 3–4-fold until 2050 as new markets in hydrogen transport shipping and power generation emerge. Ammonia production from hydrogen produced via water electrolysis with renewable power (green ammonia) and from natural gas with CO2 storage (blue ammonia) is gaining attention due to the potential role of ammonia in decarbonizing energy value chains and aiding nations in achieving their net-zero targets. This study assesses the technical and economic viability of different routes of ammonia production with an emphasis on a systems level perspective and related process integration. Additional cost reductions may be driven by optimum sizing of renewable power capacity reducing losses in the value chain technology learning and scale-up reducing risk and a lower cost of capital. Developing certification and standards will be necessary to ascertain the extent of greenhouse gas emissions throughout the supply chain as well as improving the enabling conditions including innovative finance and de-risking for facilitating international trade market creation and large-scale project development.
Mathematical Modeling of Unstable Transport in Underground Hydrogen Storage
Apr 2015
Publication
Within the framework of energy transition hydrogen has a great potential as a clean energy carrier. The conversion of electricity into hydrogen for storage and transport is an efficient technological solution capable of significantly reducing the problem of energy shortage. Underground hydrogen storage (UHS) is the best solution to store the large amount of excess electrical energy arising from the excessive over-production of electricity with the objective of balancing the irregular and intermittent energy production typical of renewable sources such as windmills or solar. Earlier studies have demonstrated that UHS should be qualitatively identical to the underground storage of natural gas. Much later however it was revealed that UHS is bound to incur peculiar difficulties as the stored hydrogen is likely to be used by the microorganisms present in the rocks for their metabolism which may cause significant losses of hydrogen. This paper demonstrates that besides microbial activities the hydrodynamic behavior of UHS is very unique and different from that of a natural gas storage.
Sustainability Assessment and Engineering of Emerging Aircraft Technologies—Challenges, Methods and Tools
Jul 2020
Publication
Driven by concerns regarding the sustainability of aviation and the continued growth of air traffic increasing interest is given to emerging aircraft technologies. Although new technologies such as battery-electric propulsion systems have the potential to minimise in-flight emissions and noise environmental burdens are possibly shifted to other stages of the aircraft’s life cycle and new socio-economic challenges may arise. Therefore a life-cycle-oriented sustainability assessment is required to identify these hotspots and problem shifts and to derive recommendations for action for aircraft development at an early stage. This paper proposes a framework for the modelling and assessment of future aircraft technologies and provides an overview of the challenges and available methods and tools in this field. A structured search and screening process is used to determine which aspects of the proposed framework are already addressed in the scientific literature and in which areas research is still needed. For this purpose a total of 66 related articles are identified and systematically analysed. Firstly an overview of statistics of papers dealing with life-cycle-oriented analysis of conventional and emerging aircraft propulsion systems is given classifying them according to the technologies considered the sustainability dimensions and indicators investigated and the assessment methods applied. Secondly a detailed analysis of the articles is conducted to derive answers to the defined research questions. It illustrates that the assessment of environmental aspects of alternative fuels is a dominating research theme while novel approaches that integrate socio-economic aspects and broaden the scope to battery-powered fuel-cell-based or hybrid-electric aircraft are emerging. It also provides insights by what extent future aviation technologies can contribute to more sustainable and energy-efficient aviation. The findings underline the need to harmonise existing methods into an integrated modelling and assessment approach that considers the specifics of upcoming technological developments in aviation.
How Flexible Electricity Demand Stabilizes Wind and Solar Market Values: The Case of Hydrogen Electrolyzers
Nov 2021
Publication
Wind and solar energy are often expected to fall victim to their own success: the higher their share in electricity generation the more their revenue in electricity markets (their “market value”) declines. While market values may converge to zero in conventional power systems this study argues that “green” hydrogen production can effectively and permanently halt the decline by adding flexible electricity demand in low-price hours. To support this argument this article further develops the merit order model and uses price duration curves to include flexible hydrogen electrolysis and to derive an analytical formula for the minimum market value of renewables in the long-term market equilibrium. This hydrogen-induced minimum market value is quantified for a wide range of parameters using Monte Carlo simulations and complemented with results from a more detailed numerical electricity market model. It is shown that—due to flexible hydrogen production alone—market values across Europe will likely stabilize above €19 ± 9 MWh− 1 for solar energy and above €27 ± 8 MWh− 1 for wind energy in 2050 (annual mean estimate ± standard deviation). This is in the range of the projected levelized cost of renewables and other types of flexible electricity demand may further increase renewable market values. Market-based renewables may hence be within reach.
Blast Wave Generated by Delayed Ignition of Under-Expanded Hydrogen Free Jet at Ambient and Cryogenic Temperatures
Nov 2022
Publication
An under-expanded hydrogen jet from high-pressure equipment or storage tank is a potential incident scenario. Experiments demonstrated that the delayed ignition of a highly turbulent under-expanded hydrogen jet generates a blast wave able to harm people and damage property. There is a need for engineering tools to predict the pressure effects during such incidents to define hazard distances. The similitude analysis is applied to build a correlation using available experimental data. The dimensionless blast wave overpressure generated by delayed ignition and the follow-up deflagration or detonation of hydrogen jets at an any location from the jet ∆Pexp/P0 is correlated to the original dimensionless parameter composed of the product of the dimensionless ratio of storage pressure to atmospheric pressure Ps/P0 and the ratio of the jet release nozzle diameter to the distance from the centre of location of the fast-burning near-stoichiometric mixture on the jet axis (30% of hydrogen in the air by volume) to the location of a target (personnel or property) d/Rw. The correlation is built using the analysis of 78 experiments regarding this phenomenon in the wide range of hydrogen storage pressure of 0.5–65.0 MPa and release diameter of 0.5–52.5 mm. The correlation is applicable to hydrogen free jets at ambient and cryogenic temperatures. It is found that the generated blast wave decays inversely proportional to the square of the distance from the fast-burning portion of the jet. The correlation is used to calculate the hazard distances by harm thresholds for five typical hydrogen applications. It is observed that in the case of a vehicle with onboard storage tank at pressure 70 MPa the “no-harm” distance for humans reduces from 10.5 m to 2.6 m when a thermally activated pressure relief device (TPRD) diameter decreases from 2 mm to a diameter of 0.5 mm.
Effect of Heat Transfer through the Release of Pipe on Simulations of Cryogenic Hydrogen Jet Fires and Hazard Distances
Sep 2021
Publication
Jet flames originated by cryo-compressed ignited hydrogen releases can cause life-threatening conditions in their surroundings. Validated models are needed to accurately predict thermal hazards from a jet fire. Numerical simulations of cryogenic hydrogen flow in the release pipe are performed to assess the effect of heat transfer through the pipe walls on jet parameters. Notional nozzle exit diameter is calculated based on the simulated real nozzle parameters and used in CFD simulations as a boundary condition to model jet fires. The CFD model was previously validated against experiments with vertical cryogenic hydrogen jet fires with release pressures up to 0.5 MPa (abs) release diameter 1.25 mm and temperatures as low as 50 K. This study validates the CFD model in a wider domain of experimental release conditions - horizontal cryogenic jets at exhaust pipe temperature 80 K pressure up to 2 MPa abs and release diameters up to 4 mm. Simulation results are compared against experimentally measured parameters as hydrogen mass flow rate flame length and radiative heat flux at several locations from the jet fire. The CFD model reproduces well experiments with reasonable engineering accuracy. Jet fire hazard distances established using three different criteria - temperature thermal radiation and thermal dose - are compared and discussed based on CFD simulation results.
Potentials of Hydrogen Technologies for Sustainable Factory Systems
Mar 2021
Publication
The industrial sector is the world’s second largest emitter of greenhouse gases hence a methodology for decarbonizing factory systems is crucial for achieving global climate goals. Hydrogen is an important medium for the transition towards carbon neutral factories due to its broad applicability within the factory including its use in electricity and heat generation and as a process gas or fuel. One of the main challenges is the identification of economically and environmentally suitable design scenarios such as for the entire value chain for hydrogen generation and application. For example the infrastructure for renewable electricity hydrogen generation hydrogen conversion (e.g. into synthetic fuels) storage and transport systems as well as application in the factory. Due to the high volatility of energy generation and the related dynamic interdependencies within a factory system a valid technical economic and environmental evaluation of benefits induced by hydrogen technologies can only be achieved using digital factory models. In this paper we present a framework to integrate hydrogen technologies into factory systems. This enables decision makers to identify promising measures according to their expected impact and collect data for appropriate factory modelling. Furthermore a concept for factory modelling and simulation is presented and demonstrated in a case study from the electronics industry assessing the use of hydrogen for decentralized power and heat generation.
Life Cycle Assessment of Improved High Pressure Alkaline Electrolysis
Aug 2015
Publication
This paper investigates environmental impacts of high pressure alkaline water electrolysis systems. An advanced system with membranes on polymer basis is compared to a state-of-the-art system with asbestos membranes using a Life Cycle Assessment (LCA) approach. For the advanced system a new improved membrane technology has been investigated within the EU research project “ELYGRID”. Results indicate that most environmental impacts are caused by the electricity supply necessary for operation. During the construction phase cell stacks are the main contributor to environmental impacts. New improved membranes have relatively small contributions to impacts caused by cell construction within the advanced systems. As main outcome the systems comparison illustrates a better ecological performance of the new developed system
Site-Dependent Environmental Impacts of Industrial Hydrogen Production by Alkaline Water Electrolysis
Jun 2017
Publication
Industrial hydrogen production via alkaline water electrolysis (AEL) is a mature hydrogen production method. One argument in favor of AEL when supplied with renewable energy is its environmental superiority against conventional fossil-based hydrogen production. However today electricity from the national grid is widely utilized for industrial applications of AEL. Also the ban on asbestos membranes led to a change in performance patterns making a detailed assessment necessary. This study presents a comparative Life Cycle Assessment (LCA) using the GaBi software (version 6.115 thinkstep Leinfelden-Echterdingen Germany) revealing inventory data and environmental impacts for industrial hydrogen production by latest AELs (6 MW Zirfon membranes) in three different countries (Austria Germany and Spain) with corresponding grid mixes. The results confirm the dependence of most environmental effects from the operation phase and specifically the site-dependent electricity mix. Construction of system components and the replacement of cell stacks make a minor contribution. At present considering the three countries AEL can be operated in the most environmentally friendly fashion in Austria. Concerning the construction of AEL plants the materials nickel and polytetrafluoroethylene in particular used for cell manufacturing revealed significant contributions to the environmental burden.
Future Hydrogen Markets for Transportation and Industry: The Impact of CO2 Taxes
Dec 2019
Publication
The technological lock-in of the transportation and industrial sector can be largely attributed to the limited availability of alternative fuel infrastructures. Herein a countrywide supply chain analysis of Germany spanning until 2050 is applied to investigate promising infrastructure development pathways and associated hydrogen distribution costs for each analyzed hydrogen market. Analyzed supply chain pathways include seasonal storage to balance fluctuating renewable power generation with necessary purification as well as trailer- and pipeline-based hydrogen delivery. The analysis encompasses green hydrogen feedstock in the chemical industry and fuel cell-based mobility applications such as local buses non-electrified regional trains material handling vehicles and trucks as well as passenger cars. Our results indicate that the utilization of low-cost long-term storage and improved refueling station utilization have the highest impact during the market introduction phase. We find that public transport and captive fleets offer a cost-efficient countrywide renewable hydrogen supply roll-out option. Furthermore we show that at comparable effective carbon tax resulting from the current energy tax rates in Germany hydrogen is cost-competitive in the transportation sector by the year 2025. Moreover we show that sector-specific CO2 taxes are required to provide a cost-competitive green hydrogen supply in both the transportation and industrial sectors.
Simulation of Coupled Power and Gas Systems with Hydrogen-Enriched Natural Gas
Nov 2021
Publication
Due to the increasing share of renewable energy sources in the electrical network the focus on decarbonization has extended into other energy sectors. The gas sector is of special interest because it can offer seasonal storage capacity and additional flexibility to the electricity sector. In this paper we present a new simulation method designed for hydrogen-enriched natural gas network simulation. It can handle different gas compositions and is thus able to accurately analyze the impact of hydrogen injections into natural gas pipelines. After describing the newly defined simulation method we demonstrate how the simulation tool can be used to analyze a hydrogen-enriched gas pipeline network. An exemplary co-simulation of coupled power and gas networks shows that hydrogen injections are severely constrained by the gas pipeline network highlighting the importance and necessity of considering different gas compositions in the simulation.
Transient Reversible Solid Oxide Cell Reactor Operation – Experimentally Validated Modeling and Analysis
Oct 2018
Publication
A reversible solid oxide cell (rSOC) reactor can operate efficiently in both electrolysis mode and in fuel cell mode. The bidirectional operability enables rSOC reactors to play a central role as an efficient energy conversion system for energy storage and sector coupling for a renewable energy driven society. A combined system for electrolysis and fuel cell operation can result in complex system configurations that should be able to switch between the two modes as quickly as possible. This can lead to temperature profiles within the reactor that can potentially lead to the failure of the reactor and eventually the system. Hence the behavior of the reactor during the mode switch should be analyzed and optimal transition strategies should be taken into account during the process system design stage. In this paper a one dimensional transient reversible solid oxide cell model was built and experimentally validated using a commercially available reactor. A simple hydrogen based system model was built employing the validated reactor model to study reactor behavior during the mode switch. The simple design leads to a system efficiency of 49% in fuel cell operation and 87% in electrolysis operation where the electrolysis process is slightly endothermic. Three transient operation strategies were studied. It is shown that the voltage response to transient operation is very fast provided the reactant flows are changed equally fast. A possible solution to ensure a safe mode switch by controlling the reactant inlet temperatures is presented. By keeping the rate of change of reactant inlet temperatures five to ten times slower than the mode switch a safe transition can be ensured.
Thermodynamic and Ecological Preselection of Synthetic Fuel Intermediates from Biogas at Farm Sites
Jan 2020
Publication
Background: Synthetic fuels based on renewable hydrogen and CO2 are a currently highly discussed piece of the puzzle to defossilize the transport sector. In this regard CO2 can play a positive role in shaping a sustainable future. Large potentials are available as a product of biogas production however occurring in small scales and in thin spatial distributions. This work aims to evaluate suitable synthetic fuel products to be produced at farm sites.<br/>Methods: A thermodynamic analysis to assess the energetic efficiency of synthesis pathways and a qualitative assessment of product handling issues is carried out.<br/>Results: Regarding the technical and safety-related advantages in storage liquid products are the superior option for fuel production at decentralized sites. Due to the economy of scale multi-stage synthesis processes lose economic performance with rising complexity. A method was shown which covers a principle sketch of all necessary reaction separation steps and all compression and heat exchanger units. The figures showed that methanol and butanol are the most suitable candidates in contrast to OME3-5 for implementation in existing transportation and fuel systems. These results were underpin by a Gibbs energy analysis.<br/>Conclusions: As long as safety regulations are met and the farm can guarantee safe storage and transport farm-site production for all intermediates can be realized technically. Ultimately this work points out that the process must be kept as simple as possible favoring methanol production at farm site and its further processing to more complicated fuels in large units for several fuel pathways.
Alternative Energy Technologies as a Cultural Endeavor: A Case Study of Hydrogen and Fuel Cell Development in Germany
Feb 2012
Publication
Background: The wider background to this article is the shift in the energy paradigm from fossil energy sources to renewable sources which should occur in the twenty-first century. This transformation requires the development of alternative energy technologies that enable the deployment of renewable energy sources in transportation heating and electricity. Among others hydrogen and fuel cell technologies have the potential to fulfill this requirement and to contribute to a sustainable and emission-free transport and energy system. However whether they will ever reach broad societal acceptance will not only depend on technical issues alone. The aim of our study is to reveal the importance of nontechnical issues. Therefore the article at hand presents a case study of hydrogen and fuel cells in Germany and aims at highlighting the cultural context that affects their development.<br/>Methods: Our results were obtained from a rich pool of data generated in various research projects through more than 30 in-depth interviews direct observations and document analyses.<br/>Results: We found that individual and collective actors developed five specific supportive practices which they deploy in five diverse arenas of meaning in order to attach certain values to hydrogen and fuel cell technologies.<br/>Conclusions: Based on the results we drew more general conclusions and deducted an overall model for the analysis of culture in technological innovations that is outlined at the end of the article. It constitutes our contribution to the interdisciplinary collaboration required for tackling the shift in this energy paradigm.
Reliable Off-grid Power Supply Utilizing Green Hydrogen
Jun 2021
Publication
Green hydrogen produced from wind solar or hydro power is a suitable electricity storage medium. Hydrogen is typically employed as mid- to long-term energy storage whereas batteries cover short-term energy storage. Green hydrogen can be produced by any available electrolyser technology [alkaline electrolysis cell (AEC) polymer electrolyte membrane (PEM) anion exchange membrane (AEM) solid oxide electrolysis cell (SOEC)] if the electrolysis is fed by renewable electricity. If the electrolysis operates under elevated pressure the simplest way to store the gaseous hydrogen is to feed it directly into an ordinary pressure vessel without any external compression. The most efficient way to generate electricity from hydrogen is by utilizing a fuel cell. PEM fuel cells seem to be the most favourable way to do so. To increase the capacity factor of fuel cells and electrolysers both functionalities can be integrated into one device by using the same stack. Within this article different reversible technologies as well as their advantages and readiness levels are presented and their potential limitations are also discussed.
Is Blue Hydrogen a Bridging Technology? - The Limits of a CO2 Price and the Role of State-induced Price Components for Green Hydrogen Production in Germany
Jun 2022
Publication
The European Commission aims to establish green hydrogen produced through electrolysis using renewable electricity and in a transition phase hydrogen produced in a low-carbon process or blue hydrogen. In an extensive cost analysis for Germany up to 2050 based on scenario data and a component-based learning rate approach we find that blue hydrogen is likely to establish itself as the most cost-effective option and not only as a medium-term low-carbon alternative. We find that expected CO2 prices below €480/tCO2 have a limited impact on the economic feasibility of electrolysis and show that substantial increases in excise tax on natural gas could lead blue hydrogen to reach a sufficient cost level for electrolysed hydrogen. Unless alternatives for green hydrogen supply through infrastructure and imports become available at lower cost electrolysed hydrogen may require long-term subsidies. As blue hydrogen comprises fugitive methane emissions and financing needs for green hydrogen support have implications for society and competition in the internal market we suggest that policymakers rely on hydrogen for decarbonising only essential energy applications. We recommend further investigations into the cost of hydrogen infrastructure and import options as well as efficient subsidy frameworks.
Linking the Power and Transport Sectors—Part 2: Modelling a Sector Coupling Scenario for Germany
Jul 2017
Publication
“Linking the power and transport sectors—Part 1” describes the general principle of “sector coupling” (SC) develops a working definition intended of the concept to be of utility to the international scientific community contains a literature review that provides an overview of relevant scientific papers on this topic and conducts a rudimentary analysis of the linking of the power and transport sectors on a worldwide EU and German level. The aim of this follow-on paper is to outline an approach to the modelling of SC. Therefore a study of Germany as a case study was conducted. This study assumes a high share of renewable energy sources (RES) contributing to the grid and significant proportion of fuel cell vehicles (FCVs) in the year 2050 along with a dedicated hydrogen pipeline grid to meet hydrogen demand. To construct a model of this nature the model environment “METIS” (models for energy transformation and integration systems) we developed will be described in more detail in this paper. Within this framework a detailed model of the power and transport sector in Germany will be presented in this paper and the rationale behind its assumptions described. Furthermore an intensive result analysis for the power surplus utilization of electrolysis hydrogen pipeline and economic considerations has been conducted to show the potential outcomes of modelling SC. It is hoped that this will serve as a basis for researchers to apply this framework in future to models and analysis with an international focus.
New Control Strategy for Heating Portable Fuel Cell Power Systems for Energy-Efficient and Reliable Operation
Dec 2022
Publication
Using hydrogen fuel cells for power systems temperature conditions are important for efficient and reliable operations especially in low-temperature environments. A heating system with an electrical energy buffer is therefore required for reliable operation. There is a research gap in finding an appropriate control strategy regarding energy efficiency and reliable operations for different environmental conditions. This paper investigates heating strategies for the subfreezing start of a fuel cell for portable applications at an early development stage to enable frontloading in product engineering. The strategies were investigated by simulation and experiment. A prototype for such a system was built and tested for subfreezing start-ups and non-subfreezing start-ups. This was done by heating the fuel cell system with different control strategies to test their efficiency. It was found that operating strategies to heat up the fuel cell system can ensure a more reliable and energy efficient operation. The heating strategy needs to be adjusted according to the ambient conditions as this influences the required heating energy efficiency and reliable operation of the system. A differentiation in the control strategy between subfreezing and non-subfreezing temperatures is recommended due to reliability reasons.
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.
Cryogenic and Ambient Gaseous Hydrogen Blowdown with Discharge Line Effects
Sep 2021
Publication
The present work performed within the PRESLHY EC-project presents a simplified 1-d transient modelling methodology to account for discharge line effects during blowdown. The current formulation includes friction extra resistance area change and heat transfer through the discharge line walls and is able to calculate the mass flow rate and distribution of all physical variables along the discharge line. Choked flow at any time during the transient is calculated using the Possible Impossible Flow (PIF) algorithm. Hydrogen single phase physical properties and vapour-liquid equilibrium are calculated using the Helmholtz Free Energy (HFE) formulation. Homogeneous Equilibrium Mixture (HEM) model is used for two-phase physical properties. Validation is performed against the new experiments with compressed gaseous hydrogen performed at the DISCHA facility in the framework of PRESLHY (200 bar ambient and cryogenic initial tank temperature 77 K and 4 nozzle diameters 0.5 1 2 and 4 mm) and an older experiment at 900 bar ambient temperature and 2 mm nozzle. Predictions are compared against measured data from the experiments and the relative importance of line heat transfer compared to flow resistance is analysed.
Hydrogen-Assisted Cracking in GMA Welding of High-Strength Structural Steel—A New Look into This Issue at Narrow Groove
Jun 2021
Publication
Modern arc processes such as the modified spray arc (Mod. SA) have been developed for gas metal arc welding of high-strength structural steels with which even narrow weld seams can be welded. High-strength joints are subjected to increasingly stringent requirements in terms of welding processing and the resulting component performance. In the present work this challenge is to be met by clarifying the influences on hydrogen-assisted cracking (HAC) in a high-strength structural steel S960QL. Adapted samples analogous to the self-restraint TEKKEN test are used and analyzed with respect to crack formation microstructure diffusible hydrogen concentration and residual stresses. The variation of the seam opening angle of the test seams is between 30° and 60°. To prevent HAC the effectiveness of a dehydrogenation heat treatment (DHT) from the welding heat is investigated. As a result the weld metals produced at reduced weld opening angle show slightly higher hydrogen concentrations on average. In addition increased micro- as well as macro-crack formation can be observed on these weld metal samples. On all samples without DHT cracks in the root notch occur due to HAC which can be prevented by DHT immediately after welding.
Alkaline Water Electrolysis Powered by Renewable Energy: A Review
Feb 2020
Publication
Alkaline water electrolysis is a key technology for large-scale hydrogen production powered by renewable energy. As conventional electrolyzers are designed for operation at fixed process conditions the implementation of fluctuating and highly intermittent renewable energy is challenging. This contribution shows the recent state of system descriptions for alkaline water electrolysis and renewable energies such as solar and wind power. Each component of a hydrogen energy system needs to be optimized to increase the operation time and system efficiency. Only in this way can hydrogen produced by electrolysis processes be competitive with the conventional path based on fossil energy sources. Conventional alkaline water electrolyzers show a limited part-load range due to an increased gas impurity at low power availability. As explosive mixtures of hydrogen and oxygen must be prevented a safety shutdown is performed when reaching specific gas contamination. Furthermore the cell voltage should be optimized to maintain a high efficiency. While photovoltaic panels can be directly coupled to alkaline water electrolyzers wind turbines require suitable converters with additional losses. By combining alkaline water electrolysis with hydrogen storage tanks and fuel cells power grid stabilization can be performed. As a consequence the conventional spinning reserve can be reduced which additionally lowers the carbon dioxide emissions.
Hydrogen Embrittlement Mechanism in Fatigue Behavior of Austenitic and Martensitic Stainless Steels
May 2018
Publication
In the present study the influence of hydrogen on the fatigue behavior of the high strength martensitic stainless steel X3CrNiMo13-4 and the metastable austenitic stainless steels X2Crni19-11 with various nickel contents was examined in the low and high cycle fatigue regime. The focus of the investigations were the changes in the mechanisms of short crack propagation. Experiments in laboratory air with uncharged and precharged specimen and uncharged specimen in pressurized hydrogen were carried out. The aim of the ongoing investigation was to determine and quantitatively describe the predominant processes of hydrogen embrittlement and their influence on the short fatigue crack morphology and crack growth rate. In addition simulations were carried out on the short fatigue crack growth in order to develop a detailed insight into the hydrogen embrittlement mechanisms relevant for cyclic loading conditions. It was found that a lower nickel content and a higher martensite content of the samples led to a higher susceptibility to hydrogen embrittlement. In addition crack propagation and crack path could be simulated well with the simulation model.
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).
Boosting the H2 Production Efficiency via Photocatalytic Organic Reforming: The Role of Additional Hole Scavenging System
Nov 2021
Publication
The simultaneous photocatalytic H2 evolution with environmental remediation over semiconducting metal oxides is a fascinating process for sustainable fuel production. However most of the previously reported photocatalytic reforming showed nonstoichiometric amounts of the evolved H2 when organic substrates were used. To explain the reasons for this phenomenon a careful analysis of the products and intermediates in gas and aqueous phases upon the photocatalytic hydrogen evolution from oxalic acid using Pt/TiO2 was performed. A quadrupole mass spectrometer (QMS) was used for the continuous flow monitoring of the evolved gases while high performance ion chromatography (HPIC) isotopic labeling and electron paramagnetic resonance (EPR) were employed to understand the reactions in the solution. The entire consumption of oxalic acid led to a ~30% lower H2 amount than theoretically expected. Due to the contribution of the photoKolbe reaction mechanism a tiny amount of formic acid was produced then disappeared shortly after the complete consumption of oxalic acid. Nevertheless a much lower concentration of formic acid was generated compared to the nonstoichiometric difference between the formed H2 and the consumed oxalic acid. Isotopic labeling measurements showed that the evolved H2 HD and/or D2 matched those of the solvent; however using D2O decreased the reaction rate. Interestingly the presence of KI as an additional hole scavenger with oxalic acid had a considerable impact on the reaction mechanism and thus the hydrogen yield as indicated by the QMS and the EPR measurements. The added KI promoted H2 evolution to reach the theoretically predictable amount and inhibited the formation of intermediates without affecting the oxalic acid degradation rate. The proposed mechanism by which KI boosts the photocatalytic performance is of great importance in enhancing the overall energy efficiency for hydrogen production via photocatalytic organic reforming.
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.
Hydrogen-powered Aviation in Germany: A Macroeconomic Perspective and Methodological Approach of Fuel Supply Chain Integration into an Economy-wide Dataset
Oct 2022
Publication
The hydrogen (H2) momentum affects the aviation sector. However a macroeconomic consideration is currently missing. To address this research gap the paper derives a methodology for evaluating macroeconomic effects of H2 in aviation and applies this approach to Germany. Three goals are addressed: (1) Construction of a German macroeconomic database. (2) Translation of H2 supply chains to the system of national accounts. (3) Implementation of H2-powered aviation into the macroeconomic data framework. The article presents an economy-wide database for analyzing H2-powered aviation. Subsequently the paper highlights three H2 supply pathways provides an exemplary techno-economic cost break-down for ten H2 components and translates them into the data framework. Eight relevant macroeconomic sectors for H2-powered aviation are identified and quantified. Overall the paper contributes on a suitable foundation to apply the macroeconomic dataset to and conduct macroeconomic analyses on H2-powered aviation. Finally the article highlights further research potential on job effects related to future H2 demand.
Methane Cracking as a Bridge Technology to the Hydrogen Economy
Nov 2016
Publication
Shifting the fossil fuel dominated energy system to a sustainable hydrogen economy could mitigate climate change through reduction of greenhouse gas emissions. Because it is estimated that fossil fuels will remain a significant part of our energy system until mid-century bridge technologies which use fossil fuels in an environmentally cleaner way offer an opportunity to reduce the warming impact of continued fossil fuel utilization. Methane cracking is a potential bridge technology during the transition to a sustainable hydrogen economy since it produces hydrogen with zero emissions of carbon dioxide. However methane feedstock obtained from natural gas releases fugitive emissions of methane a potent greenhouse gas that may offset methane cracking benefits. In this work a model exploring the impact of methane cracking implementation in a hydrogen economy is presented and the impact on global emissions of carbon dioxide and methane is explored. The results indicate that the hydrogen economy has the potential to reduce global carbon dioxide equivalent emissions between 0 and 27% when methane leakage from natural gas is relatively low methane cracking is employed to produce hydrogen and a hydrogen fuel cell is applied. This wide range is a result of differences between the scenarios and the CH4 leakage rates used in the scenarios. On the other hand when methane leakage from natural gas is relatively high methane steam reforming is employed to produce hydrogen and an internal combustion engine is applied the hydrogen economy leads to a net increase in global carbon dioxide equivalent emissions between 19 and 27%.
Assessment of Fossil-free Steelmaking Based on Direct Reduction Applying High-temperature Electrolysis
Jun 2021
Publication
Preventing humanity from serious impact of climate crisis requires carbon neutrality across all economic sectors including steel industry. Although fossil-free steelmaking routes receiving increasing attention fundamental process aspects especially approaches towards the improvement of efficiency and flexibility are so far not comprehensively studied. In this paper optimized process concepts allowing for a gradual transition towards fossil-free steelmaking based on the coupling of direct reduction process electric arc furnace and electrolysis are presented. Both a high-temperature and low-temperature electrolysis were modeled and possibilities for the integration into existing infrastructure are discussed. Various schemes for heat integration especially when using high-temperature electrolysis are highlighted and quantified. It is demonstrated that the considered direct reduction-based process concepts allow for a high degree of flexibility in terms of feed gas composition when partially using natural gas as a bridge technology. This allows for an implementation in the near future as well as the possibility of supplying power grid services in a renewable energy system. Furthermore it is shown that an emission reduction potential of up to 97.8% can be achieved with a hydrogen-based process route and 99% with a syngas-based process route respectively provided that renewable electricity is used.
Carbon-Negative Hydrogen Production (HyBECCS) from Organic Waste Materials in Germany: How to Estimate Bioenergy and Greenhouse Gas Mitigation Potential
Nov 2021
Publication
Hydrogen derived from biomass feedstock (biohydrogen) can play a significant role in Germany’s hydrogen economy. However the bioenergy potential and environmental benefits of biohydrogen production are still largely unknown. Additionally there are no uniform evaluation methods present for these emerging technologies. Therefore this paper presents a methodological approach for the evaluation of bioenergy potentials and the attainable environmental impacts of these processes in terms of their carbon footprints. A procedure for determining bioenergy potentials is presented which provides information on the amount of usable energy after conversion when applied. Therefore it elaborates a four-step methodical conduct dealing with available waste materials uncertainties of early-stage processes and calculation aspects. The bioenergy to be generated can result in carbon emission savings by substituting fossil energy carriers as well as in negative emissions by applying biohydrogen production with carbon capture and storage (HyBECCS). Hence a procedure for determining the negative emissions potential is also presented. Moreover the developed approach can also serve as a guideline for decision makers in research industry and politics and might also serve as a basis for further investigations such as implementation strategies or quantification of the benefits of biohydrogen production from organic waste material in Germany
Direct Evidence for Solid-like Hydrogen in a Nanoporous Carbon Hydrogen Storage Material at Supercritical Temperatures
Jul 2015
Publication
Here we report direct physical evidence that confinement of molecular hydrogen (H2) in an optimized nanoporous carbon results in accumulation of hydrogen with characteristics commensurate with solid H2 at temperatures up to 67 K above the liquid vapor critical temperature of bulk H2. This extreme densification is attributed to confinement of H2 molecules in the optimally sized micropores and occurs at pressures as low as 0.02 MPa. The quantities of contained solid-like H2 increased with pressure and were directly evaluated using in situ inelastic neutron scattering and confirmed by analysis of gas sorption isotherms. The demonstration of the existence of solid-like H2 challenges the existing assumption that supercritical hydrogen confined in nanopores has an upper limit of liquid H2 density. Thus this insight offers opportunities for the development of more accurate models for the evaluation and design of nanoporous materials for high capacity adsorptive hydrogen storage.
Cost-optimized Design Point and Operating Strategy of Polymer Electrolyte Membrane Electrolyzers
Nov 2022
Publication
Green hydrogen is a key solution for reducing CO2 emissions in various industrial applications but high production costs continue to hinder its market penetration today. Better competitiveness is linked to lower investment costs and higher efficiency of the conversion technologies among which polymer electrolyte membrane electrolysis seems to be attractive. Although new manufacturing techniques and materials can help achieve these goals a less frequently investigated approach is the optimization of the design point and operating strategy of electrolyzers. This means in particular that the questions of how often a system should be operated and which cell voltage should be applied must be answered. As existing techno-economic models feature gaps which means that these questions cannot be adequately answered a modified model is introduced here. In this model different technical parameters are implemented and correlated to each other in order to simulate the lowest possible levelized cost of hydrogen and extract the required designs and strategies from this. In each case investigated the recommended cost-based cell voltage that should be applied to the system is surprisingly low compared to the assumptions made in previous publications. Depending on the case the cell voltage is in a range between 1.6 V and 1.8 V with an annual operation of 2000e8000 h. The wide range of results clearly indicate how individual the design and operation must be but with efficiency gains of several percent the effect of optimization will be indispensable in the future.
The Role of Hydrogen in a Greenhouse Gas-neutral Energy Supply System in Germany
Sep 2022
Publication
Hydrogen is widely considered to play a pivotal role in successfully transforming the German energy system but the German government’s current “National Hydrogen Strategy” does not specify how hydrogen utilization production storage or distribution will be implemented. Addressing key uncertainties for the German energy system’s path to greenhouse gas-neutrality this paper examines hydrogen in different scenarios. This analysis aims to support the concretization of the German hydrogen strategy. Applying a European energy supply model with strong interactions between the conversion sector and the hydrogen system the analysis focuses on the requirements for geological hydrogen storages and their utilization over the course of a year the positioning of electrolyzers within Germany and the contributions of hydrogen transport networks to balancing supply and demand. Regarding seasonal hydrogen storages the results show that hydrogen storage facilities in the range of 42 TWhH2 to 104 TWhH2 are beneficial to shift high electricity generation volumes from onshore wind in spring and fall to winter periods with lower renewable supply and increased electricity and heat demands. In 2050 the scenario results show electrolyzer capacities between 41 GWel and 75 GWel in Germany. Electrolyzer sites were found to follow the low-cost renewable energy potential and are concentrated on the North Sea and Baltic Sea coasts with their high wind yields. With respect to a hydrogen transport infrastructure there were two robust findings: One a domestic German hydrogen transport network connecting electrolytic hydrogen production sites in northern Germany with hydrogen demand hubs in western and southern Germany is economically efficient. Two connecting Germany to a European hydrogen transport network with interconnection capacities between 18 GWH2 and 58 GWH2 is cost-efficient to meet Germany’s substantial hydrogen demand.
Methanol as a Renewable Energy Carrier: An Assessment of Production and Transportation Costs for Selected Global Locations
Jun 2021
Publication
The importing of renewable energy will be one part of the process of defossilizing the energy systems of countries and regions which are currently heavily dependent on the import of fossil-based energy carriers. This study investigates the possibility of importing renewable methanol comprised of hydrogen and carbon dioxide. Based on a methanol synthesis simulation model the net production costs of methanol are derived as a function of hydrogen and carbon dioxide expenses. These findings enable a comparison of the import costs of methanol and hydrogen. For this the hydrogen production and distribution costs for 2030 as reported in a recent study for four different origin/destination country combinations are considered. With the predicted hydrogen production costs of 1.35–2 €/kg and additional shipping costs methanol can be imported for 370–600 €/t if renewable or process-related carbon dioxide is available at costs of 100 €/t or below in the hydrogen-producing country. Compared to the current fossil market price of approximately 400 €/t renewable methanol could therefore become cost-competitive. Within the range of carbon dioxide prices of 30–100 €/t both hydrogen and methanol exhibit comparable energy-specific import costs of 18–30 €/GJ. Hence the additional costs for upgrading hydrogen to methanol are balanced out by the lower shipping costs of methanol compared to hydrogen. Lastly a comparison for producing methanol in the hydrogen’s origin or destination country indicates that carbon dioxide in the destination country must be 181–228 €/t less expensive than that in the origin country to balance out the more expensive shipping costs for hydrogen.
Spatially-resolved Analysis of the Challenges and Opportunities of Power-to-Gas (PtG) in Baden-Württemberg until 2040
Mar 2017
Publication
The increasing penetration of renewable energies will make new storage technologies indispensable in the future. Power-to-Gas (PtG) is one long-term storage technology that exploits the existing gas infrastructure. However this technology faces technical economic environmental challenges and questions. This contribution presents the final results of a large research project which attempted to address and provide answers to some of these questions for Baden-Württemberg (south west Germany). Three energy scenarios out to 2040 were defined one oriented towards the Integrated Energy and Climate Protection Concept of the Federal State Government and two alternatives. Timely-resolved load profiles for gas and electricity for 2015 2020 2030 and 2040 have been generated at the level of individual municipalities. The profiles include residential and industrial electrical load gas required for heating (conventional and current-controlled CHP) as well as gas and electricity demand for mobility. The installation of rooftop PV-plants and wind power plants is projected based on bottom up cost-potential analyses which account for some social acceptance barriers. Residential load profiles are derived for each municipality. In times with negative residual load the PtG technology could be used to convert electricity into hydrogen or methane. The detailed analysis of four structurally-different model regions delivered quite different results. While in large cities no negative residual load is likely due to the continuously high demand and strong networks rural areas with high potentials for renewables could encounter several thousand hours of negative residual load. A cost-effective operation of PtG would only be possible under favorable conditions including high full load hours a strong reduction in costs and a technical improvement of efficiency. Whilst these conditions are not expected to appear in the short to mid-term but may occur in the long term in energy systems with very high shares of renewable energy sources
Carbon-negative Hydrogen from Biomass Using Gas Switching Integrated Gasification: Techno-economic Assessment
Sep 2022
Publication
Ambitious decarbonization pathways to limit the global temperature rise to well below 2 ◦C will require largescale CO2 removal from the atmosphere. One promising avenue for achieving this goal is hydrogen production from biomass with CO2 capture. The present study investigates the techno-economic prospects of a novel biomass-to-hydrogen process configuration based on the gas switching integrated gasification (GSIG) concept. GSIG applies the gas switching combustion principle to indirectly combust off-gas fuel from the pressure swing adsorption unit in tubular reactors integrated into the gasifier to improve efficiency and CO2 capture. In this study these efficiency gains facilitated a 5% reduction in the levelized cost of hydrogen (LCOH) relative to conventional O2-blown fluidized bed gasification with pre-combustion CO2 capture even though the larger and more complex gasifier cancelled out the capital cost savings from avoiding the air separation and CO2 capture units. The economic assessment also demonstrated that advanced gas treatment using a tar cracker instead of a direct water wash can further reduce the LCOH by 12% and that the CO2 prices in excess of 100 €/ton consistent with ambitious decarbonization pathways will make this negative-emission technology economically highly attractive. Based on these results further research into the GSIG concept to facilitate more efficient utilization of limited biomass resources can be recommended.
Fostering Macroeconomic Research on Hydrogen-Powered Aviation: A Systematic Literature Review on General Equilibrium Models
Feb 2023
Publication
Hydrogen is a promising fuel to decarbonize aviation but macroeconomic studies are currently missing. Computable general equilibrium (CGE) models are suitable to conduct macroeconomic analyses and are frequently employed in hydrogen and aviation research. The main objective of this paper is to investigate existing CGE studies related to (a) hydrogen and (b) aviation to derive a macroeconomic research agenda for hydrogen-powered aviation. Therefore the well-established method of systematic literature review is conducted. First we provide an overview of 18 hydrogen-related and 27 aviation-related CGE studies and analyze the literature with respect to appropriate categories. Second we highlight key insights and identify research gaps for both the hydrogen and aviation-related CGE literature. Our findings comprise inter alia hydrogen’s current lack of cost competitiveness and the macroeconomic relevance of air transportation. Research gaps include among others a stronger focus on sustainable hydrogen and a more holistic perspective on the air transportation system. Third we derive implications for macroeconomic research on hydrogen-powered aviation including (I) the consideration of existing modeling approaches (II) the utilization of interdisciplinary data and scenarios (III) geographical suitability (IV) the application of diverse policy tools and (V) a holistic perspective. Our work contributes a meaningful foundation for macroeconomic studies on hydrogen-powered aviation. Moreover we recommend policymakers to address the macroeconomic perspectives of hydrogen use in air transportation.
Sector Coupling and Business Models Towards Sustainability: The Case of the Hydrogen Vehicle Industry
Mar 2022
Publication
The concept of sector coupling has been gaining increased momentum in political discourses during 18 the past few years but it has only recently received the attention of international academics. The 19 private sector is particularly relevant to foster sector coupling through entrepreneurial action – 20 specifically innovative business models for more sustainable technologies are needed to promote a 21 transition towards more sustainability. So far however the literature on business models from a 22 sector coupling perspective is scarce yet strongly emerging. To address the identified research gaps 23 and enhance the current knowledge on the emerging hydrogen vehicle industry and sector coupling 24 this study adopts a qualitative and exploratory research approach and builds on information gained 25 in 103 semi-structured interviews to discuss emerging business models in Germany. In particular 33 26 business cases have been analyzed. Anchoring business model theory to the concept of sector 27 coupling this study identifies 12 business model archetypes in the emerging hydrogen vehicle 28 industry and its value chain. It can be shown that while the market is still emerging and the market 29 players are not defined and are evolving companies are currently engaged in finding their position 30 along the value chain fostering vertical integration and promoting cooperation between the 31 different sectors. While this study is relevant for both the academia and the industry it is particularly 2 32 interesting for policy makers shaping the future of sustainable development specifically considering 33 integrated energy systems.
Underground Bio-methanation: Concept and Potential
Feb 2020
Publication
As a major part of the energy turn around the European Union and other countries are supporting the development of renewable energy technologies to decrease nuclear and fossil energy production. Therefore efficient use of renewable energy resources is one challenge as they are influenced by environmental conditions and hence the intensity of resources such as wind or solar power fluctuates. To secure constant energy supply suitable energy storage and conversion techniques are required. An upcoming solution is the utilization and storage of hydrogen or hydrogen-rich natural gas in porous formations in the underground. In the past microbial methanation was observed as a side effect during these gas storage operations. The concept of underground bio-methanation arised which uses the microbial metabolism to convert hydrogen and carbon dioxide into methane. The concept consists of injecting gaseous hydrogen and carbon dioxide into an underground structure during energy production peaks which are subsequently partly converted into methane. The resulting methane-rich gas mixture is withdrawn during high energy demand. The concept is comparable to engineered bio-reactors which are already locally integrated into the gas infrastructure. In both technologies the conversion process of hydrogen into methane is driven by hydrogenotrophic methanogenic archaea present in the aqueous phase of the natural underground or above-ground engineered reactor. Nevertheless the porous medium in the underground provides compared to the engineered bio-reactors a larger interface between the gas and aqueous phase caused by the enormous volume in the underground porous media. The following article summarizes the potential and concept of underground methanation and the current state of the art in terms of laboratory investigations and pilot tests. A short system potential analysis shows that an underground bio-reactor with a storage capacity of 850 Mio. Sm3 could deliver methane to more than 600000 households based on a hydrogen production from renewable energies.
Green Hydrogen Production Potential in West Africa – Case of Niger
Jul 2022
Publication
Niger offers the possibility of producing green hydrogen due to its high solar energy potential. Due to the still growing domestic oil and coal industry the use of green hydrogen in the country currently seems unlikely at the higher costs of hydrogen as an energy vector. However the export of green hydrogen to industrialized countries could be an option. In 2020 a hydrogen partnership has been established between Germany and Niger. The potential import of green hydrogen represents an option for Germany and other European countries to decarbonize domestic energy supply. Currently there are no known projects for the electrolytic production of hydrogen in Niger. In this work potential hydrogen demand across electricity and transport sectors is forecasted until 2040. The electricity demand in 2040 is expected at 2934 GWh and the gasoline and diesel demand at 964 m3 and 2181 m3 respectively. Accordingly the total hydrogen needed to supply electricity and the transport sector (e.g. to replace 1% gasoline and diesel demand in 2040) is calculated at 0.0117 Mt. Only a small fraction of 5% of the land area in Niger would be sufficient to generate the required electricity from solar PV to produce hydrogen.
Biological CO2-Methanation: An Approach to Standardization
May 2019
Publication
Power-to-Methane as one part of Power-to-Gas has been recognized globally as one of the key elements for the transition towards a sustainable energy system. While plants that produce methane catalytically have been in operation for a long time biological methanation has just reached industrial pilot scale and near-term commercial application. The growing importance of the biological method is reflected by an increasing number of scientific articles describing novel approaches to improve this technology. However these studies are difficult to compare because they lack a coherent nomenclature. In this article we present a comprehensive set of parameters allowing the characterization and comparison of various biological methanation processes. To identify relevant parameters needed for a proper description of this technology we summarized existing literature and defined system boundaries for Power-to-Methane process steps. On this basis we derive system parameters providing information on the methanation system its performance the biology and cost aspects. As a result three different standards are provided as a blueprint matrix for use in academia and industry applicable to both biological and catalytic methanation. Hence this review attempts to set the standards for a comprehensive description of biological and chemical methanation processes.
Simulation of Hydrogen Mixing and Par Operation During Accidental Release in an LH2 Carrier Engine Room
Sep 2021
Publication
Next-generation LH2 carriers may use the boil-off gas from the cargo tanks as additional fuel for the engine. As a consequence hydrogen pipes will enter the room of the ship’s propulsion system and transport hydrogen to the main engine. The hydrogen distribution resulting from a postulated hydrogen leak inside the room of the propulsion system has been analyzed by means of Computational Fluid Dynamics (CFD). In a subsequent step simulations with passive auto-catalytic recombiners (PARs) were carried out in order to investigate if the recombiners can increase the safety margins during such accident scenarios. CFD enables a 3D prediction of the transient distribution with a high resolution allowing to identify local accumulation of hydrogen and consequently to identify optimal PAR positions as well as to demonstrate the efficiency of the PARs. The simulation of the unmitigated reference case reveals a strong natural circulation driven by the density difference of hydrogen and the incoming cold air from the ventilation system. Globally this natural circulation dilutes the hydrogen and removes a considerable amount from the room of the ship’s propulsion system via the ventilation ducts. However a hydrogen accumulation beyond the flammability limit is identified below the first ceiling above the leak position and the back-side wall of the engine room. Based on these findings suitable positions for recombiners were identified. The design objectives of the PAR system were on the one hand to provide both high instantaneous and integral removal rate and on the other hand to limit build-up of flammable clouds by means of depletion and PAR induced mixing processes. The simulations performed with three different PAR arrangements (variation of large and<br/>small PAR units at different positions) confirm that the PARs reduce efficiently the hydrogen<br/>accumulations.
Law and Policy Review on Green Hydrogen Potential in ECOWAS Countries
Mar 2022
Publication
This paper aims to review existing energy-sector and hydrogen-energy-related legal policy and strategy documents in the ECOWAS region. To achieve this aim current renewable-energyrelated laws acts of parliament executive orders presidential decrees administrative orders and memoranda were analyzed. The study shows that ECOWAS countries have strived to design consistent legal instruments regarding renewable energy in developing comprehensive legislation and bylaws to consolidate it and to encourage investments in renewable energy. Despite all these countries having a legislative basis for regulating renewable energy there are still weaknesses that revolve around the law and policy regarding its possible application in green hydrogen production and use. The central conclusion of this review paper is that ECOWAS member states presently have no official hydrogen policies nor bylaws in place. The hydrogen rise presents a challenge and opportunity for members to play an important role in the fast-growing global hydrogen market. Therefore these countries need to reform their regulatory frameworks and align their policies by introducing green hydrogen production in order to accomplish their green economy transition for the future and to boost the continent’s sustainable development.
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.
The More the Merrier? Actors and Ideas in the Evolution of Germany Hydrogen Policy Discourse
Feb 2023
Publication
Hydrogen has set high hopes for decarbonization due to its flexibility and ability to decarbonize sectors of the economy where direct electrification appears unviable. Broad hydrogen policies have therefore started to emerge. Nevertheless it is still a rather niche technology not integrated or adopted at scale and not regulated through particular policy provisions. The involved stakeholders are thus still rushing to set the agenda over the issue. All this plays out publicly and shapes the public discourse. This paper explores how the composition of stakeholders their positions and the overall discourse structure have developed and accompanied the political agenda-setting in the early public debate on hydrogen in Germany. We use discourse network analysis of media where stakeholders' claims-making is documented and their positions can be tracked over time. The public discourse on hydrogen in Germany shows the expected evolution of statements in connection with the two milestones chosen for the analyses the initiation of the Gas 2030 Dialogue and the publication of the National Hydrogen Strategy. Interestingly the discourse was comparatively feeble in the immediate aftermath of the respective milestones but intensified in a consolidation phase around half a year later. Sequencing the discourse and contextualizing its content relative to political societal and economic conditions in a diachronic way is essential because it helps to avoid misinterpreting the development of stakeholders' standpoints as conflict-driven rather than mere repositioning. Thus we observed no discourse “polarization” even though potentially polarizing issues were already present in the debate.
Design of Fuel Cell Systems for Aviation: Representative Mission Profiles and Sensitivity Analyses
Apr 2019
Publication
The global transition to a clean and sustainable energy infrastructure does not stop at aviation. The European Commission defined a set of environmental goals for the “Flight Path 2050”: 75% CO2 reduction 90% NOx reduction and 65% perceived noise reduction. Hydrogen as an energy carrier fulfills these needs while it would also offer a tenable and flexible solution for intermittent large-scale energy storage for renewable energy networks. If hydrogen is used as an energy carrier there is no better device than a fuel cell to convert its stored chemical energy. In order to design fuel cell systems for passenger aircraft it is necessary to specify the requirements that the system has to fulfill. In this paper a statistical approach to analyze these requirements is presented which accounts for variations in the flight mission profile. Starting from a subset of flight data within the desired class (e.g. mid-range inter-European flights) a stochastic model of the random mission profile is inferred. This model allows for subsequent predictions under uncertainty as part of the aircraft design process. By using Monte Carlo-based sampling of flight mission profiles the range of necessary component sizes as well as optimal degrees of hybridization with a battery is explored and design options are evaluated. Furthermore Monte Carlo-based sensitivity analysis of performance parameters explores the potential of future technological developments. Results suggest that the improvement of the specific power of the fuel cell is the deciding factor for lowering the energy system mass. The specific energy of the battery has a low influence but acts in conjunction with the specific power of the fuel cell.
Life Cycle Costing Approaches of Fuel Cell and Hydrogen Systems: A Literature Review
Apr 2023
Publication
Hydrogen is a versatile energy carrier which can be produced from variety of feedstocks stored and transported in various forms for multi-functional end-uses in transportation energy and manufacturing sectors. Several regional national and supra-national climate policy frameworks emphasize the need value and importance of Fuel cell and Hydrogen (FCH) technologies for deep and sector-wide decarbonization. Despite these multi-faceted advantages familiar and proven FCH technologies such as alkaline electrolysis and proton-exchange membrane fuel cell (PEMFC) often face economic technical and societal barriers to mass-market adoption. There is no single unified standardized and globally harmonized normative definition of costs. Nevertheless the discussion and debates surrounding plausible candidates and/or constituents integral for assessing the economics and value proposition of status-quo as well as developmental FCH technologies are steadily increasing—Life Cycle Costing (LCC) being one of them if not the most important outcome of such exercises.<br/>To that end this review article seeks to improve our collective understanding of LCC of FCH technologies by scrutinizing close to a few hundred publications drawn from representative databases—SCOPUS and Web of Science encompassing several tens of technologies for production and select transportation storage and end-user utilization cases. This comprehensive review forms part of and serves as the basis for the Clean Hydrogen Partnership funded SH2E project whose ultimate goal is the methodical development a formal set of principles and guardrails for evaluating the economic environmental and social impacts of FCH technologies. Additionally the SH2E projects will also facilitate the proper comparison of different FCH technologies whilst reconciling range of technologies methodologies modelling assumptions and parameterization found in existing literature.
Power Sector Effects of Green Hydrogen Production in Germany
Aug 2023
Publication
The use of green hydrogen can support the decarbonization of sectors which are difficult to electrify such as industry or heavy transport. Yet the wider power sector effects of providing green hydrogen are not well understood so far. We use an open-source electricity sector model to investigate potential power sector interactions of three alternative supply chains for green hydrogen in Germany in the year 2030. We distinguish between model settings in which Germany is modeled as an electric island versus embedded in an interconnected system with its neighboring countries as well as settings with and without technology-specific capacity bounds on wind energy. The findings suggest that large-scale hydrogen storage can provide valuable flexibility to the power system in settings with high renewable energy shares. These benefits are more pronounced in the absence of flexibility from geographical balancing. We further find that the effects of green hydrogen production on the optimal generation portfolio strongly depend on the model assumptions regarding capacity expansion potentials. We also identify a potential distributional effect of green hydrogen production at the expense of other electricity consumers of which policy makers should be aware.
Energy System Changes in 1.5 °C, Well Below 2 °C and 2 °C Scenarios
Dec 2018
Publication
Meeting the Paris Agreement's goal to limit global warming to well below 2 °C and pursuing efforts towards 1.5 °C is likely to require more rapid and fundamental energy system changes than the previously-agreed 2 °C target. Here we assess over 200 integrated assessment model scenarios which achieve 2 °C and well-below 2 °C targets drawn from the IPCC's fifth assessment report database combined with a set of 1.5 °C scenarios produced in recent years. We specifically assess differences in a range of near-term indicators describing CO2 emissions reductions pathways changes in primary energy and final energy across the economy's major sectors in addition to more detailed metrics around the use of carbon capture and storage (CCS) negative emissions low-carbon electricity and hydrogen.
Technology Transfer from Fuel Processing for Fuel Cells to Fuel Synthesis from Hydrogen and Carbon Dioxide
Aug 2023
Publication
Improving the energy efficiency of existing technologies such as the on-board power supply of trucks ships and aircraft is an important endeavor for reducing primary energy consumption. The approach consists of using fuel cell technology in conjunction with hydrogen production from liquid fuels. However the energy transition with the goal of complete climate-neutrality requires technological changes in the use of hydrogen produced from renewable energy via electrolysis. Synthetic fuels are an important building block for drive systems that will continue to require liquid energy carriers in the future due to their range. This study addresses the question of whether technical devices that were developed for the generation of hydrogen from liquid fuels for fuel cells to generate electricity are now suitable for the reverse process chain or can play an important role in it. The new process chain produces hydrogen from sustainable electricity combining it with carbon dioxide to create a synthetic liquid fuel.
H2-powered Aviation at Airports – Design and Economics of LH2 Refueling Systems
Feb 2022
Publication
In this paper the broader perspective of green hydrogen (H2) supply and refueling systems for aircraft is provided as an enabling technology brick for more climate friendly H2-powered aviation. For this two H2 demand scenarios at exemplary airports are determined for 2050. Then general requirements for liquid hydrogen (LH2) refueling setups in an airport environment are derived and techno-economic models for LH2 storage liquefaction and transportation to the aircraft are designed. Finally a cost tradeoff study is undertaken for the design of the LH2 setup including LH2 refueling trucks and a LH2 pipeline and hydrant system. It is found that for airports with less than 125 ktLH2 annual demand a LH2 refueling truck setup is the more economic choice. At airports with higher annual LH2 demands a LH2 pipeline & hydrant system can lead to slight cost reductions and enable safer and faster refueling. However in all demand scenarios the refueling system costs only mark 3 to 4% of the total supply costs of LH2. The latter are dominated by the costs for green H2 produced offsite followed by the costs for liquefaction of H2 at an airport. While cost reducing scaling effects are likely to be achieved for H2 liquefaction plants other component capacities would already be designed at maximum capacities for medium-sized airports. Furthermore with annual LH2 demands of 100 ktLH2 and more medium and larger airports could take a special H2 hub role by 2050 dominating regional H2 consumption. Finally technology demonstrators are required to reduce uncertainty around major techno-economic parameters such as the investment costs for LH2 pipeline & hydrant systems.
Experimental Study of Cycle-by-cycle Variations in a Spark Ignition Internal Combustion Engine Fueled with Hydrogen
Feb 2024
Publication
High fluctuations in the combustion process from one cycle to another referred to as cycle-by-cycle variations can have adverse effects on internal combustion engine performances particularly in spark ignition (SI) engines. These effects encompass incomplete combustion the potential for misfires and adverse impacts on fuel economy. Furthermore the cycle-by-cycle variations can also affect a vehicle’s drivability and overall comfort especially when operating under lean-burn conditions. Although many cycle-by-cycle analyses have been investigated extensively in the past there is limited in-depth knowledge available regarding the causes of cycle-by-cycle (CbC) variations in hydrogen lean-burn SI engines. Trying to contribute to this topic the current study presents a comprehensive analysis of the CbC variations based on the cylinder pressure data. The study was carried out employing a hydrogen single-cylinder research SI engine. The experiments were performed by varying more than fifty operating conditions including the variations in lambda spark advance boost pressure and exhaust gas recirculation however the load and speed were kept constant throughout the experimental campaign. The results indicate that pressure exhibits significant variations during the combustion process and minor variations during non-combustion processes. In the period from the inlet valve close till the start of combustion pressure exhibits the least variations. The coefficient of variation of pressure (COVP) curve depicts three important points in H2-ICE as well: global minima global maxima and second local minima. The magnitude of the COVP curve changes across all the operating conditions however the shape of the COVP curve remains unchanged across all the operating conditions indicating its independence from the operating condition in an H2-ICE. This study presents an alternative approach for a quick combustion analysis of hydrogen engines. Without the need for more complex methodologies like heat release rate analysis the presented cylinder pressure cycle-by-cycle analysis enables a quick and precise identification of primary combustion features (start of combustion center of combustion end of combustion and operation condition stability). Additionally the engine control unit could implement these procedures to automatically adjust cycle-by-cycle variations therefore increasing engine efficiency.
Parameterization Proposal to Determine the Feasibility of Geographic Areas for the Green Hydrogen Industry under Socio-environmental and Technical Constraints in Chile
Oct 2023
Publication
Chile abundant in solar and wind energy resources presents significant potential for the production of green hydrogen a promising renewable energy vector. However realizing this potential requires an understanding of the most suitable locations for the installation of green hydrogen industries. This study proposes a quantitative methodology that identifies and ranks potential public lands for industrial use based on a range of technical parameters (such as solar and wind availability) and socio-environmental considerations (including land use restrictions and population density). The results reveal optimal locations that can facilitate informed sustainable decision-making for large-scale green hydrogen implementation in Chile. While this methodology does not replace project-specific technical or environmental impact studies it provides a flexible general classification to guide initial site selection. Notably this approach can be applied to other regions worldwide with abundant solar and wind resources such as Australia and Northern Africa promoting more effective and sustainable global decision-making for green hydrogen production.
Global Hydrogen and Synfuel Exchanges in an Emission-Free Energy System
Apr 2023
Publication
This study investigates the global allocation of hydrogen and synfuels in order to achieve the well below 2 ◦C preferably 1.5 ◦C target set in the Paris Agreement. For this purpose TIMES Integrated Assessment Model (TIAM) a global energy system model is used. In order to investigate global hydrogen and synfuel flows cost potential curves are aggregated and implemented into TIAM as well as demand technologies for the end use sectors. Furthermore hydrogen and synfuel trades are established using liquid hydrogen transport (LH2 ) and both new and existing technologies for synfuels are implemented. To represent a wide range of possible future events four different scenarios are considered with different characteristics of climate and security of supply policies. The results show that in the case of climate policy the renewable energies need tremendous expansion. The final energy consumption is shifting towards the direct use of electricity while certain demand technologies (e.g. aviation and international shipping) require hydrogen and synfuels for full decarbonization. Due to different security of supply policies the global allocation of hydrogen and synfuel production and exports is shifting while the 1.5 ◦C target remains feasible in the different climate policy scenarios. Considering climate policy Middle East Asia is the preferred region for hydrogen export. For synfuel production several regions are competitive including Middle East Asia Mexico Africa South America and Australia. In the case of security of supply policies Middle East Asia is sharing the export volume with Africa while only minor changes can be seen in the synfuel supply.
Can an Energy Only Market Enable Resource Adequacy in a Decarbonized Power System? A Co-simulation with Two Agent-based-models
Feb 2024
Publication
Future power systems in which generation will come almost entirely from variable Renewable Energy Sources (vRES) will be characterized by weather-driven supply and flexible demand. In a simulation of the future Dutch power system we analyze whether there are sufficient incentives for market-driven investors to provide a sufficient level of security of supply considering the profit-seeking and myopic behavior of investors. We cosimulate two agent-based models (ABM) one for generation expansion and one for the operational time scale. The results suggest that in a system with a high share of vRES and flexibility prices will be set predominantly by the demand’s willingness to pay particularly by the opportunity cost of flexible hydrogen electrolyzers. The demand for electric heating could double the price of electricity in winter compared to summer and in years with low vRES could cause shortages. Simulations with stochastic weather profiles increase the year-to-year variability of cost recovery by more than threefold and the year-to-year price variability by more than tenfold compared to a scenario with no weather uncertainty. Dispatchable technologies have the most volatile annual returns due to high scarcity rents during years of low vRES production and diminished returns during years with high vRES production. We conclude that in a highly renewable EOM investors would not have sufficient incentives to ensure the reliability of the system. If they invested in such a way to ensure that demand could be met in a year with the lowest vRES yield they would not recover their fixed costs in the majority of years.
The Potential Role of a Hydrogen Network in Europe
Jul 2023
Publication
Europe’s electricity transmission expansion suffers many delays despite its significance for integrating renewable electricity. A hydrogen network reusing the existing gas network could not only help to supply the demand for low-emission fuels but could also balance variations in wind and solar energies across the continent and thus avoid power grid expansion. Our investigation varies the allowed expansion of electricity and hydrogen grids in net-zero CO2 scenarios for a sector-coupled European energy system capturing transmission bottlenecks renewable supply and demand variability and pipeline retrofitting and geological storage potentials. We find that a hydrogen network connecting regions with low-cost and abundant renewable potentials to demand centers electrofuel production and cavern storage sites reduces system costs by up to 26 bnV/a (3.4%). Although expanding both networks together can achieve the largest cost reductions by 9.9% the expansion of neither is essential for a net-zero system as long as higher costs can be accepted and flexibility options allow managing transmission bottlenecks.
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.
Thermodynamic Evaluation and Carbon Footprint Analysis of the Application of Hydrogen-Based Energy-Storage Systems in Residential Buildings
Sep 2016
Publication
This study represents a thermodynamic evaluation and carbon footprint analysis of the application of hydrogen based energy storage systems in residential buildings. In the system model buildings are equipped with photovoltaic (PV) modules and a hydrogen storage system to conserve excess PV electricity from times with high solar irradiation to times with low solar irradiation. Short-term storages enable a degree of self-sufficiency of approximately 60% for a single-family house (SFH) [multifamily house (MFH): 38%]. Emissions can be reduced by 40% (SFH) (MFH: 30%) compared to households without PV modules. These results are almost independent of the applied storage technology. For seasonal storage the degree of self-sufficiency ranges between 57 and 83% (SFH). The emission reductions highly depend on the storage technology as emissions caused by manufacturing the storage dominate the emission balance. Compressed gas or liquid organic hydrogen carriers are the best options enabling emission reductions of 40%.
The Role of Liquid Hydrogen in Integrated Energy Systems - A Case Study for Germany
May 2023
Publication
Hydrogen (H2) is expected to be a key building block in future greenhouse gas neutral energy systems. This study investigates the role of liquid hydrogen (LH2) in a national greenhouse gas-neutral energy supply system for Germany in 2045. The integrated energy system model suite ETHOS is extended by LH2 demand profiles in the sectors aviation mobility and chemical industry and means of LH2 transportation via inland vessel rail and truck. This case study demonstrates that the type of hydrogen demand (liquid or gaseous) can strongly affect the cost-optimal design of the future energy system. When LH2 demand is introduced to the energy system LH2 import transportation and production grow in importance. This decreases the need for gaseous hydrogen (GH2) pipelines and affects the location of H2 production plants. When identifying no-regret measures it must be considered that the largest H2 consumers are the ones with the highest readiness to use LH2.
Evaluation of Surplus Hydroelectricity Potential in Nepal until 2040 and its Use for Hydrogen Production Via Electrolysis
May 2023
Publication
The abundant hydro resources in Nepal have resulted in the generation of electricity almost exclusively from hydropower plants. Several hydropower plants are also currently under construction. There is no doubt that the surplus electricity will be significantly high in the coming years. Given the previous trend in electricity consumption it will be a challenge to maximize the use of surplus electricity. In this work the potential solutions to maximize the use of this surplus electricity have been analysed. Three approached are proposed: (i) increasing domestic electricity consumption by shifting the other energy use sectors to electricity (ii) cross-border export of electricity and (iii) conversion of electricity to hydrogen via electrolysis. The current state of energy demand and supply patterns in the country are presented. Future monthly demand forecasts and surplus electricity projections have been made. The hydrogen that can be produced with the surplus electricity via electrolysis is determined and an economic assessment is carried out for the produced hydrogen. The analysis of levelized cost of hydrogen (LCOH) under different scenarios resulted values ranging from 3.8 €/kg to 4.5 €/kg.
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.
Grid-supported Electrolytic Hydrogen Production: Cost of Climate Impact Using Dynamic Emission Factors
Aug 2023
Publication
Hydrogen production based on a combination of intermittent renewables and grid electricity is a promising approach for reducing emissions in hard-to-decarbonise sectors at lower costs. However for such a configuration to provide climate benefits it is crucial to ensure that the grid electricity consumed in the process is derived from low-carbon sources. This paper examined the use of hourly grid emission factors (EFs) to more accurately determine the short-term climate impact of dynamically operated electrolysers. A model of the interconnected northern European electricity system was developed and used to calculate average grid-mix and marginal EFs for the four bidding zones in Sweden. Operating a 10 MW electrolyser using a combination of onshore wind and grid electricity was found to decrease the levelised cost of hydrogen (LCOH) to 2.40–3.63 €/kgH2 compared with 4.68 €/kgH2 for wind-only operation. A trade-off between LCOH and short-term climate impact was revealed as specific marginal emissions could exceed 20 kgCO2eq/kgH2 at minimum LCOH. Both an emission-minimising operating strategy and an increased wind-to-electrolyser ratio was found to manage this trade-off by enabling simultaneous cost and emission reductions lowering the marginal carbon abatement cost (CAC) from 276.8 €/tCO2eq for wind-only operation to a minimum of 222.7 and 119.3 €/tCO2eq respectively. Both EF and LCOH variations were also identified between the bidding zones but with no notable impact on the marginal CAC. When using average grid-mix emission factors the climate impact was low and the CAC could be reduced to 71.3–200.0 €/tCO2eq. In relation to proposed EU policy it was demonstrated that abiding by hourly renewable temporal matching principles could ensure low marginal emissions at current levels of fossil fuels in the electricity mix.
Hydrogen Role in the Valorization of Integrated Steelworks Process Off-gases through Methane and Methanol Syntheses
Jun 2021
Publication
The valorization of integrated steelworks process off-gases as feedstock for synthesizing methane and methanol is in line with European Green Deal challenges. However this target can be generally achieved only through process off-gases enrichment with hydrogen and use of cutting-edge syntheses reactors coupled to advanced control systems. These aspects are addressed in the RFCS project i3 upgrade and the central role of hydrogen was evident from the first stages of the project. First stationary scenario analyses showed that the required hydrogen amount is significant and existing renewable hydrogen production technologies are not ready to satisfy the demand in an economic perspective. The poor availability of low-cost green hydrogen as one of the main barriers for producing methane and methanol from process off-gases is further highlighted in the application of an ad-hoc developed dispatch controller for managing hydrogen intensified syntheses in integrated steelworks. The dispatch controller considers both economic and environmental impacts in the cost function and although significant environmental benefits are obtainable by exploiting process off-gases in the syntheses the current hydrogen costs highly affect the dispatch controller decisions. This underlines the need for big scale green hydrogen production processes and dedicated green markets for hydrogen-intensive industries which would ensure easy access to this fundamental gas paving the way for a C-lean and more sustainable steel production.
Assessing the Social Acceptance of Key Technologies for the German Energy Transition
Jan 2022
Publication
Background: The widespread use of sustainable energy technologies is a key element in the transformation of the energy system from fossil-based to zero-carbon. In line with this technology acceptance is of great importance as resistance from the public can slow down or hinder the construction of energy technology projects. The current study assesses the social acceptance of three energy technologies relevant for the German energy transition: stationary battery storage biofuel production plants and hydrogen fuel station. Methods: An online survey was conducted to examine the public’s general and local acceptance of energy technologies. Explored factors included general and local acceptance public concerns trust in relevant stakeholders and attitudes towards financial support. Results: The results indicate that general acceptance for all technologies is slightly higher than local acceptance. In addition we discuss which public concerns exist with regard to the respective technologies and how they are more strongly associated with local than general acceptance. Further we show that trust in stakeholders and attitudes towards fnancial support is relatively high across the technologies discussed. Conclusions: Taken together the study provides evidence for the existence of a “general–local” gap despite measuring general and local acceptance at the same level of specifcity using a public sample. In addition the collected data can provide stakeholders with an overview of worries that might need to be addressed when planning to implement a certain energy project.
Comprehensive Techno-economic Assessment of Power Technologies and Synthetic Fuels under Discussion for Ship Applications
Jun 2023
Publication
The decarbonization of the global ship traffic is one of the industry’s greatest challenges for the next decades and will likely only be achieved with the introduction of synthetic fuels. Until now however not one single best technology solution emerged to ideally fit this task. Instead different energy carriers including hydrogen ammonia methanol methane and synthetic diesel are subject of discussion for usage in either internal combustion engines or fuel cells. In order to drive the selection procedure a case study for the year 2030 with all eligible combinations of power technologies and fuels is conducted. The assessment quantifies the technologies’ economic performances for cost-optimized system designs and in dependence of a ship’s mission characteristics. Thereby the influence of trends for electrofuel prices and shipboard volume opportunity costs are examined. Even if gaseous hydrogen is often considered not suitable for large ship applications due to its low volumetric energy density both the comparatively small fuel price and the high efficiency of fuel cells lead to the overall smallest system costs for passages up to 21 days depending on assumed cost parameters. Only for missions longer than seven days fuel cells operating on methanol or ammonia can compete with gaseous hydrogen economically.
The Market Introduction of Hydrogen Focussing on Bus Refueling
Dec 2023
Publication
Public transport plays a prominent role with respect to mitigating transport-related environmental effects by improving passenger transport efficiency and the quality of life in cities. Batteries and fuel cells are at the forefront of the technological shift to zero-emission powertrains. Within the scope of the German-funded project BIC H2 corresponding systems analysis research focuses on the market introduction of fuel cell–electric buses in the Rhine–Ruhr Metropolitan Region through 2035. This study presents the related methods and major outcomes of this techno-economic research which spans spatially-resolved hydrogen demand modeling of all relevant sectors to hydrogen refueling stations and upstream infrastructure modeling to scenario-based analyses. The latter builds upon an empirical study supporting the development of the Hydrogen Roadmap of the State of North Rhine–Westphalia (NRW). Our results show that the demand in NRW alone is expected to account for one third of total German hydrogen use. Hydrogen bus refueling could substantially support market introduction during its early phases. In the long term however hydrogen demand in industry is significantly higher compared to that in the transport sector. Furthermore spatial analysis identifies regions with pronounced hydrogen demands that could therefore be candidates for initial infrastructure investments. With the Cologne area showing the highest hydrogen demand levels such regions can offer particularly high infrastructure utilization e.g. for bus refueling. On the infrastructure side trailers for transporting gaseous hydrogen to refueling stations are the most favorable option through 2035. Pipelines would be the preferred solution soon after 2035 due to increased hydrogen demand. If effectively deployed converted natural gas pipelines would be the most cost-effective option even earlier.
Seasonal Hydrogen Storage for Residential On- and Off-grid Solar Photovoltaics Prosumer Applications: Revolutionary Solution or Niche Market for the Energy Transition until 2050?
Apr 2023
Publication
Appropriate climate change mitigation requires solutions for all actors of the energy system. The residential sector is a major part of the energy system and solutions for the implementation of a seasonal hydrogen storage system in residential houses has been increasingly discussed. A global analysis of prosumer systems including seasonal hydrogen storage with water electrolyser hydrogen compressor storage tank and a fuel cell studying the role of such a seasonal household storage in the upcoming decades is not available. This study aims to close this research gap via the improved LUT-PROSUME model which models a fully micro sector coupled residential photovoltaic prosumer system with linear optimisation for 145 regions globally. The modelling of the cost development of hydrogen storage components allows for the simulation of a residential system from 2020 until 2050 in 5-year steps in hourly resolution. The systems are cost-optimised for either on– or off-grid operation in eight scenarios including battery electric vehicles which can act as an additional vehicle-to-home electricity storage for the system. Results show that implementation of seasonal hydrogen systems only occurs in least cost solutions in high latitude countries when the system is forced to run in off-grid mode. In general a solar photovoltaic plus battery system including technologies that can cover the heat demand is the most economic choice and can even achieve lower cost than a full grid supply in off-grid operation for most regions until 2050. Additional parameters including the self-consumption ratio the demand cover ratio and the heat cover ratio can therefore not be improved by seasonal storage systems if economics is the main deciding factor for a respective system. Further research opportunities and possible limitations of the system are then identified.
The Industry Transformation from Fossil Fuels to Hydrogen will Reorganize Value Chains: Big Picture and Case Studies for Germany
Jan 2024
Publication
In many industries low-carbon hydrogen will substitute fossil fuels in the course of the transformation to climate neutrality. This paper contributes to understanding this transformation. This paper provides an overview of energy- and emission-intensive industry sectors with great potential to defossilize their production processes with hydrogen. An assessment of future hydrogen demand for various defossilization strategies in Germany that rely on hydrogen as a feedstock or as an energy carrier to a different extent in the sectors steel chemicals cement lime glass as well as pulp and paper is carried out. Results indicate that aggregate industrial hydrogen demand in those industries would range between 197 TWh and 298 TWh if production did not relocate abroad for any industry sector. The range for hydrogen demand is mainly due to differences in the extent of hydrogen utilization as compared to alternative transformation paths for example based on electrification. The attractiveness of production abroad is then assessed based on the prospective comparative cost advantage of relocating parts of the value chain to excellent production sites for low-carbon hydrogen. Case studies are provided for the steel industry as well as the chemical industry with ethylene production through methanol and the production of urea on the basis of ammonia. The energy cost of the respective value chains in Germany is then compared to the case of value chains partly located in regions with excellent conditions for renewable energies and hydrogen production. The results illustrate that at least for some processes – as ammonia production – relocation to those favorable regions may occur due to substantial comparative cost advantages.
The Impact of the Russian War against Ukraine on the German Hydrogen Discourse
Jan 2024
Publication
This contribution delves into the transformative effects of the Russian–Ukrainian war on the discourse surrounding German hydrogen. Employing structural topical modeling (STM) on a vast dataset of 2192 newspaper articles spanning from 2019 to 2022 it aims to uncover thematic shifts attributed to the Russian invasion of Ukraine. The onset of the war in February 2022 triggered a significant pivot in the discourse shifting it from sustainability and climate-change mitigation to the securing of energy supplies through new partnerships particularly in response to Russia’s unreliability. Germany started exploring alternative energy trading partners like Canada and Australia emphasizing green hydrogen development. The study illustrates how external shocks can expedite the uptake of new technologies. The adoption of the “H2 readiness” concept for LNG terminals contributes to the successful implementation of green hydrogen. In summary the Russian–Ukrainian war profoundly impacted the German hydrogen discourse shifting the focus from sustainability to energy supply security underscoring the interconnectedness of energy security and sustainability in Germany’s hydrogen policy.
Underground Hydrogen Storage to Balance Seasonal Variations in Energy Demand: Impact of Well Configuration on Storage Performance in Deep Saline Aquifers
Mar 2023
Publication
Grid-scale underground hydrogen storage (UHS) is essential for the decarbonization of energy supply systems on the path towards a zero-emissions future. This study presents the feasibility of UHS in an actual saline aquifer with a typical dome-shaped anticline structure to balance the potential seasonal mismatches between energy supply and demand in the UK domestic heating sector. As a main requirement for UHS in saline aquifers we investigate the role of well configuration design in enhancing storage performance in the selected site via numerical simulation. The results demonstrate that the efficiency of cyclic hydrogen recovery can reach around 70% in the short term without the need for upfront cushion gas injection. Storage capacity and deliverability increase in successive storage cycles for all scenarios with the co-production of water from the aquifer having a minimal impact on the efficiency of hydrogen recovery. Storage capacity and deliverability also increase when additional wells are added to the storage site; however the distance between wells can strongly influence this effect. For optimum well spacing in a multi-well storage scenario within a dome-shaped anticline structure it is essential to attain an efficient balance between well pressure interference effects at short well distances and the gas uprising phenomenon at large distances. Overall the findings obtained and the approach described can provide effective technical guidelines pertaining to the design and optimization of hydrogen storage operations in deep saline aquifers.
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.
Development and Testing of a 100 kW Fuel-flexible Micro Gas Turbine Running on 100% Hydrogen
Jun 2023
Publication
Hydrogen as a carbon-free energy carrier has emerged as a crucial component in the decarbonization of the energy system serving as both an energy storage option and fuel for dispatchable power generation to mitigate the intermittent nature of renewable energy sources. However the unique physical and combustion characteristics of hydrogen which differ from conventional gaseous fuels such as biogas and natural gas present new challenges that must be addressed. To fully integrate hydrogen as an energy carrier in the energy system the development of low-emission and highly reliable technologies capable of handling hydrogen combustion is imperative. This study presents a ground-breaking achievement - the first successful test of a micro gas turbine running on 100% hydrogen with NOx emissions below the standard limits. Furthermore the combustor of the micro gas turbine demonstrates exceptional fuel flexibility allowing for the use of various blends of hydrogen biogas and natural gas covering a wide range of heating values. In addition to a comprehensive presentation of the test rig and its instrumentation this paper illuminates the challenges of hydrogen combustion and offers real-world operational data from engine operation with 100% hydrogen and its blends with methane.
Evaluation of Sourcing Decision for Hydrogen Supply Chain Using an Integrated Multi-Criteria Decision Analysis (MCDA) Tool
Apr 2023
Publication
The use of fossil fuels has caused many environmental issues including greenhouse gas emissions and associated climate change. Several studies have focused on mitigating this problem. One dynamic direction for emerging sources of future renewable energy is the use of hydrogen energy. In this research we evaluate the sourcing decision for a hydrogen supply chain in the context of a case study in Thailand using group decision making analysis for policy implications. We use an integrative multi-criteria decision analysis (MCDA) tool which includes an analytic hierarchy process (AHP) fuzzy AHP (FAHP) and data envelopment analysis (DEA) to analyze weighted criteria and sourcing alternatives using data collected from a group of selected experts. A list of criteria related to sustainability paradigms and sourcing decisions for possible use of hydrogen energy including natural gas coal biomass and water are evaluated. Our results reveal that political acceptance is considered the most important criterion with a global weight of 0.514 in the context of Thailand. Additionally natural gas is found to be the foreseeable source for hydrogen production in Thailand with a global weight of 0.313. We also note that the analysis is based on specific data inputs and that an alternative with a lower score does not imply that the source is not worth exploring.
Semi-Systematic Literature Review on the Contribution of Hydrogen to Universal Access to Energy in the Rationale of Sustainable Development Goal Target 7.1
Feb 2023
Publication
As part of the United Nations’ (UN) Sustainable Development Goal 7 (SDG7) SDG target 7.1 recognizes universal electrification and the provision of clean cooking fuel as two fundamental challenges for global society. Faltering progress toward SDG target 7.1 calls for innovative technologies to stimulate advancements. Hydrogen has been proposed as a versatile energy carrier to be applied in both pillars of SDG target 7.1: electrification and clean cooking. This paper conducts a semi-systematic literature review to provide the status quo of research on the application of hydrogen in the rationale of SDG 7.1 covering the technical integration pathways as well as the key economic environmental and social aspects of its use. We identify decisive factors for the future development of hydrogen use in the rationale of SDG target 7.1 and by complementing our analysis with insights from the related literature propose future avenues of research. The literature on electrification proposes that hydrogen can serve as a backup power supply in rural off-grid communities. While common electrification efforts aim to supply appliances that use lower amounts of electricity a hydrogen-based power supply can satisfy appliances with higher power demands including electric cook stoves while simultaneously supporting clean cooking efforts. Alternatively with the exclusive aim of stimulating clean cooking hydrogen is proposed to be used as a clean cooking fuel via direct combustion in distribution and utilization infrastructures analogous to Liquid Petroleum Gas (LPG). While expected economic and technical developments are seen as likely to render hydrogen technologies economically competitive with conventional fossil fuels in the future the potential of renewably produced hydrogen usage to reduce climate-change impacts and point-of-use emissions is already evident today. Social benefits are likely when meeting essential safety standards as a hydrogen-based power supply offers service on a high tier that might overachieve SDG 7.1 ambitions while hydrogen cooking via combustion fits into the existing social habits of LPG users. However the literature lacks clear evidence on the social impact of hydrogen usage. Impact assessments of demonstration projects are required to fill this research gap.
Benchmark of J55 and X56 Steels on Cracking and Corrosion Effects Under Hydrogen Salt Cavern Boundary Conditions
Feb 2024
Publication
Salt caverns have great potential to store relevant amounts of hydrogen as part of the energy transition. However the durability and suitability of commonly used steels for piping in hydrogen salt caverns is still under research. In this work aging effects focusing on corrosion and cracking patterns of casing steel API 5CT J55 and “H2ready” pipeline steel API 5L X56 were investigated with scanning electron microscopy and energy dispersive X-ray spectroscopy after accelerated stress tests with pressure/temperature cycling under hydrogen salt cavern-like conditions. Compared to dry conditions significant more corrosion by presence of salt ions was detected. However compared to X56 only for J55 an intensification of corrosion and cracking at the surface due to hydrogen atmosphere was revealed. Pronounced surface cracks were observed for J55 over the entire samples. Overall the results strongly suggest that X56 is more resistant than J55 under the conditions of a hydrogen salt cavern.
THyGA - Long Term Effect of H2 on Appliances Tested
May 2023
Publication
The goals of the long-term tests were to see the impact of blends of hydrogen and natural gas on the technical condition of the appliances and their performance after several hours of operation. To do so they were run through an accelerated test program amounting to more than 3000 testing hours for the boilers and more than 2500 testing hours for the cookers. The percentage of hydrogen in the test gas was 30% by volume. Three boilers and two cookers were tested by DGC and two boilers by GWI. This report describes the test protocol the results and analysis on the seven appliances tested.
Analyzing the Future Potential of Defossilizing Industrial Specialty Glass Production with Hydrogen by LCA
Mar 2022
Publication
The glass industry is part of the energy-intensive industry with most of the energy needed to melt the raw materials. To produce glass temperatures between 1000 and 1600 °C are necessary. Presently mostly fossil natural gas is the dominant energy source. As direct electrification is not always possible in this paper a Life Cycle Assessment (LCA) for specialty glass production is conducted where the conventional fossil-based reference process is compared to a hydrogen-fired furnace. This hydrogen can be produced on-site in an water electrolyzer using not only the hydrogen for the combustion but also the produced oxygen. Hydrogen can be produced alternatively off-site in a large scale electrolyzer to facilitate economy of scale. For the transport and distribution of this hydrogen different options are available. A rather new option are liquid organic hydrogen carriers (LOHC) which bind the hydrogen in a chemical substance. However temperatures around 300 °C are necessary to separate the hydrogen from the LOHC after transport. At the glass trough waste heat is available at the required temperature level to facilitate the dehydrogenation. The comparison is completed by the production of off-site hydrogen transported to the glass trough as conventional liquefied hydrogen in cooling tanks by truck or in hydrogen pipelines. In this assessment to power the electrolyzers the national grid mix of Germany is used. A time frame from 2020 till 2050 and its changing energy system towards defossilisation is analyzed. Regarding climate change on-site hydrogen production causes the least impact for specialty glass production in 2050. However negative trade-offs for other environmental impact categories e.g. Metal depletion are recorded.
Carbon-negative Hydrogen Production (HyBECCS): An Exemplary Techno-economic and Environmental Assessment
Sep 2023
Publication
An exemplary techno-economic and environmental assessment of carbon-negative hydrogen (H2) production is carried out in this work. It is based on the so-called “dark photosynthesis” with carbon dioxide (CO2) capture and geological storage. As a special feature of the assessment the economic consequences due to the impact on the global climate are taken into account. The results indicate that the example project would be capable of generating negative GHG emissions under the assumptions made. The amount is estimated to be 17.72 kgCO2 to be removed from the atmosphere per kilogram of H2 produced. The levelized costs of carbon-negative hydrogen are obtained considering the economic impact of greenhouse gas emissions and removals. They are estimated to be 0.013 EUR/kWhH2. Compared to grey hydrogen from natural gas (0.12 EUR/kWhH2) and green hydrogen from electrolysis using renewable electricity (0.18 EUR/kWhH2) this shows a potential environmental-economic advantage of the considered example. Even without internalization of GHG impacts an economic advantage of the project (0.12 EUR/kWhH2) over green hydrogen (0.17 EUR/kWhH2) is indicated. Compared to other NETs the GHG removal efficiency is at the lower end of both BECCS and DACCS approaches.
Implementation of Fuel Cells in Aviation from a Maintenance, Repair and Overhaul Perspective
Dec 2022
Publication
Hydrogen is one of the most promising power sources for meeting the aviation sector’s long-term decarbonization goals. Although on-board hydrogen systems namely fuel cells are extensively researched the maintenance repair and overhaul (MRO) perspective remains mostly unaddressed. This paper analyzes fuel cells from an MRO standpoint based on a literature review and comparison with the automotive sector. It also examines how well the business models and key resources of MRO providers are currently suited to provide future MRO services. It is shown that fuel cells require extensive MRO activities and that these are needed to meet the aviation sector’s requirements for price safety and especially durability. To some extent experience from the automotive sector can be built upon particularly with respect to facility requirements and qualification of personnel. Yet MRO providers’ existing resources only partially allow them to provide these services. MRO providers’ underlying business models must adapt to the implementation of fuel cells in the aviation sector. MRO providers and services should therefore be considered and act as enablers for the introduction of fuel cells in the aviation industry.
Review of Power-to-X Demonstration Projects in Europe
Sep 2020
Publication
At the heart of most Power-to-X (PtX) concepts is the utilization of renewable electricity to produce hydrogen through the electrolysis of water. This hydrogen can be used directly as a final energy carrier or it can be converted into for example methane synthesis gas liquid fuels electricity or chemicals. Technical demonstration and systems integration are of major importance for integrating PtX into energy systems. As of June 2020 a total of 220 PtX research and demonstration projects in Europe have either been realized completed or are currently being planned. The central aim of this review is to identify and assess relevant projects in terms of their year of commissioning location electricity and carbon dioxide sources applied technologies for electrolysis capacity type of hydrogen post-processing and the targeted field of application. The latter aspect has changed over the years. At first the targeted field of application was fuel production for example for hydrogen buses combined heat and power generation and subsequent injection into the natural gas grid. Today alongside fuel production industrial applications are also important. Synthetic gaseous fuels are the focus of fuel production while liquid fuel production is severely under-represented. Solid oxide electrolyzer cells (SOECs) represent a very small proportion of projects compared to polymer electrolyte membranes (PEMs) and alkaline electrolyzers. This is also reflected by the difference in installed capacities. While alkaline electrolyzers are installed with capacities between 50 and 5000 kW (2019/20) and PEM electrolyzers between 100 and 6000 kW SOECs have a capacity of 150 kW. France and Germany are undertaking the biggest efforts to develop PtX technologies compared to other European countries. On the whole however activities have progressed at a considerably faster rate than had been predicted just a couple of years ago.
Conceptual Design of a Hydrogen-Hybrid Dual-Fuel Regional Aircraft Retrofit
Jan 2024
Publication
A wide range of aircraft propulsion technologies is being investigated in current research to reduce the environmental impact of commercial aviation. As the implementation of purely hydrogenpowered aircraft may encounter various challenges on the airport and vehicle side combined hydrogen and kerosene energy sources may act as an enabler for the first operations with liquid hydrogen propulsion technologies. The presented studies describe the conceptual design of such a dual-fuel regional aircraft featuring a retrofit derived from the D328eco under development by Deutsche Aircraft. By electrically assisting the sustainable aviation fuel (SAF) burning conventional turboprop engines with the power of high-temperature polymer-electrolyte fuel cells the powertrain architecture enables a reduction of SAF consumption. All aircraft were modeled and investigated using the Bauhaus Luftfahrt Aircraft Design Environment. A description of this design platform and the incorporated methods to model the hydrogen-hybrid powertrain is given. Special emphasis was laid on the implications of the hydrogen and SAF dual-fuel system design to be able to assess the potential benefits and drawbacks of various configurations with the required level of detail. Retrofit assumptions were applied particularly retaining the maximum takeoff mass while reducing payload to account for the propulsion system mass increase. A fuel cell power allocation of 20% led to a substantial 12.9% SAF consumption decrease. Nonetheless this enhancement necessitated an 18.1% payload reduction accompanied by a 34.5% increment in propulsion system mass. Various additional studies were performed to assess the influence of the power split. Under the given assumptions the design of such a retrofit was deemed viable.
Economic Complexity of Green Hydrogen Production Technologies - A Trade Data-based Analysis of Country-sepcific Industrial Preconditions
May 2023
Publication
Countries with high energy demand but limited renewable energy potential are planning to meet part of their future energy needs by importing green hydrogen. For potential exporting countries in addition to sufficient renewable resources industrial preconditions are also relevant for the successful implementation of green hydrogen production value chains. A list of 36 “Green H2 Products” needed for stand-alone hydrogen production plants was defined and their economic complexity was analyzed using international trade data from 1995 to 2019. These products were found to be comparatively complex to produce and represent an opportunity for countries to enter new areas of the product space through green diversification. Large differences were revealed between countries in terms of industrial preconditions and their evolution over time. A detailed analysis of nine MENA countries showed that Turkey and Tunisia already possess industrial know-how in various green hydrogen technology components and perform only slightly worse than potential European competitors while Algeria Libya and Saudi Arabia score the lowest in terms of calculated hydrogen-related green complexity. These findings are supported by statistical tests showing that countries with a higher share of natural resources rents in their gross domestic product score significantly lower on economic and green complexity. The results thus provide new perspectives for assessing the capabilities of potential hydrogen-producing countries which may prove useful for policymakers and investors. Simultaneously this paper contributes to the theory of economic complexity by applying its methods to a new subset of products and using a dataset with long-term coverage.
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.
Study on the Use of Fuel Cells in Shipping
Jan 2017
Publication
Fuel Cells are a promising technology in the context of clean power sustainability and alternative fuels for shipping. Different specific developments on Fuel Cells are available today with research and pilot projects under evaluation that have revealed strong potential for further scaled up implementation. The EMSA Study on the use of Fuel Cells in Shipping has been the result of this Agency’s initiative under the agreement of the Commission and in support of EU Member States an important instrument developed in close partnership with DNV-GL.
Notwithstanding the close dependency of Fuel Cell technology and the development of hydrogen fuel solutions different solutions are today in place making use of LNG methanol and other low flashpoint fuels. EMSA participates in support of the Commission in the 2nd phase development of the IGF Code where provisions for Fuel Cells are to be included as a new part of the text.
The EMSA Study on the use of Fuel Cells in Shipping includes a technology and regulatory review identifying gaps to be further explored the selection of the most promising Fuel Cell technologies for shipping and finally a generic Safety Assessment where the selected technologies are evaluated according to Risk & Safety aspects in generic ship design applications.
Notwithstanding the close dependency of Fuel Cell technology and the development of hydrogen fuel solutions different solutions are today in place making use of LNG methanol and other low flashpoint fuels. EMSA participates in support of the Commission in the 2nd phase development of the IGF Code where provisions for Fuel Cells are to be included as a new part of the text.
The EMSA Study on the use of Fuel Cells in Shipping includes a technology and regulatory review identifying gaps to be further explored the selection of the most promising Fuel Cell technologies for shipping and finally a generic Safety Assessment where the selected technologies are evaluated according to Risk & Safety aspects in generic ship design applications.
THyGA - Test Report on Mitigation Solutions for Residential Natural Gas Appliances Not Designed for Hydrogen Admixture
Apr 2023
Publication
This report from the WP5 “Mitigation” provides information and test results regarding perturbations that hydrogen could cause to gas appliances when blended to natural gas especially on anatural draught for exhaust fumes or acidity for the condensates. The important topic of on-site adjustment is also studied with test results on alternative technologies and proposals of mitigation approaches.
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.
Refuelling Tests of a Hydrogen Tank for Heavy-duty Applications
Sep 2023
Publication
A transition towards zero-emission fuels is required in the mobility sector in order to reach the climate goals. Here (green) renewable hydrogen for use in fuel cells will play an important role especially for heavy duty applications such as trucks. However there are still challenges to overcome regarding efficient storage infrastructure integration and optimization of the refuelling process. A key aspect is to reduce the refuelling duration as much as possible while staying below the maximum allowed temperature of 85 C. Experimental tests for the refuelling of a 320 l type III tank were conducted at different operating conditions and the tank gas temperature measured at the front and back ends. The results indicate a strongly inhomogeneous temperature field where measuring and verifying the actual maximum temperatures proves difficult. Furthermore a simulation approach is provided to calculate the average tank gas temperature at the end of the refuelling process.
International Experience of Carbon Neutrality and Prospects of Key Technologies: Lessons for China
Feb 2023
Publication
Carbon neutrality (or climate neutrality) has been a global consensus and international experience exchange is essential. Given the differences in the degree of social development resource endowment and technological level each country should build a carbon-neutral plan based on its national conditions. Compared with other major developed countries (e.g. Germany the United States and Japan) China's carbon neutrality has much bigger challenges including a heavy and time-pressured carbon reduction task and the current energy structure that is over-dependent on fossil fuels. Here we provide a comprehensive review of the status and prospects of the key technologies for low-carbon near-zero carbon and negative carbon emissions. Technological innovations associated with coal oil-gas and hydrogen industries and their future potential in reducing carbon emissions are particularly explained and assessed. Based on integrated analysis of international experience from the world's major developed countries in-depth knowledge of the current and future technologies and China's energy and ecological resources potential five lessons for the implementation of China's carbon neutrality are proposed: (1) transformation of energy production pattern from a coal-dominated pattern to a diversified renewable energy pattern; (2) renewable power-to-X and large-scale underground energy storage; (3) integration of green hydrogen production storage transport and utilization; (4) construction of clean energy systems based on smart sector coupling (ENSYSCO); (5) improvement of ecosystem carbon sinks both in nationwide forest land and potential desert in Northwest China. This paper provides an international perspective for a better understanding of the challenges and opportunities of carbon neutrality in China and can serve as a theoretical foundation for medium-long term carbon neutral policy formulation.
Techno-Economic Evaluation of Hydrogen-Based Cooking Solutions in Remote African Communities—The Case of Kenya
Apr 2023
Publication
Hydrogen has recently been proposed as a versatile energy carrier to contribute to archiving universal access to clean cooking. In hard-to-reach rural settings decentralized produced hydrogen may be utilized (i) as a clean fuel via direct combustion in pure gaseous form or blended with Liquid Petroleum Gas (LPG) or (ii) via power-to-hydrogen-to-power (P2H2P) to serve electric cooking (e-cooking) appliances. Here we present the first techno-economic evaluation of hydrogen-based cooking solutions. We apply mathematical optimization via energy system modeling to assess the minimal cost configuration of each respective energy system on technical and economic measures under present and future parameters. We further compare the potential costs of cooking for the end user with the costs of cooking with traditional fuels. Today P2H2P-based e-cooking and production of hydrogen for utilization via combustion integrated into the electricity supply system have almost equal energy system costs to simultaneously satisfy the cooking and electricity needs of the isolated rural Kenyan village studied. P2H2P-based e-cooking might become advantageous in the near future when improving the energy efficiency of e-cooking appliances. The economic efficiency of producing hydrogen for utilization by end users via combustion benefits from integrating the water electrolysis into the electricity supply system. More efficient and cheaper hydrogen technologies expected by 2050 may improve the economic performance of integrated hydrogen production and utilization via combustion to be competitive with P2H2P-based e-cooking. The monthly costs of cooking per household may be lower than the traditional use of firewood and charcoal even today when applying the current life-line tariff for the electricity consumed or utilizing hydrogen via combustion. Driven by likely future technological improvements and the expected increase in traditional and fossil fuel prices any hydrogen-based cooking pathway may be cheaper for end users than using charcoal and firewood by 2030 and LPG by 2040. The results suggest that providing clean cooking in rural villages could economically and environmentally benefit from utilizing hydrogen. However facing the complexity of clean cooking projects we emphasize the importance of embedding the results of our techno-economic analysis in holistic energy delivery models. We propose useful starting points for future aspects to be investigated in the discussion section including business and financing models.
Green Hydrogen Production and Its Land Tenure Consequences in Africa: An Interpretive Review
Sep 2023
Publication
Globally a green hydrogen economy rush is underway and many companies investors governments and environmentalists consider it as an energy source that could foster the global energy transition. The enormous potential for hydrogen production for domestic use and export places Africa in the spotlight in the green hydrogen economy discourse. This discourse remains unsettled regarding how natural resources such as land and water can be sustainably utilized for such a resource-intensive project and what implications this would have. This review argues that green hydrogen production (GHP) in Africa has consequences where land resources (and their associated natural resources) are concerned. It discusses the current trends in GHP in Africa and the possibilities for reducing any potential pressures it may put on land and other resource use on the continent. The approach of the review is interpretive and hinges on answering three questions concerning the what why and how of GHP and its land consequences in Africa. The review is based on 41 studies identified from Google Scholar and sources identified via snowballed recommendations from experts. The GHP implications identified relate to land and water use mining-related land stress and environmental ecological and land-related socioeconomic consequences. The paper concludes that GHP may not foster the global energy transition as is being opined by many renewable energy enthusiasts but rather could help foster this transition as part of a greener energy mix. It notes that African countries that have the potential for GHP require the institutionalization of or a change in their existing approaches to land-related energy governance systems in order to achieve success.
Evaluation of Hydrogen Transportation Networks - A Case Study on the German Energy System
May 2023
Publication
Not only due to the energy crisis European policymakers are exploring options to substitute natural gas with renewable hydrogen. A condition for the application of hydrogen is a functioning transportation infrastructure. However the most efficient transport of large hydrogen quantities is still unclear and deeper analyses are missing. A promising option is converting the existing gas infrastructure. This study presents a novel approach to develop hydrogen networks by applying the Steiner tree algorithm to derive candidates and evaluate their costs. This method uses the existing grid (brownfield) and is compared to a newly built grid (Greenfield). The goal is the technical and economic evaluation and comparison of hydrogen network candidates. The methodology is applied to the German gas grid and demand and supply scenarios covering the industry heavy-duty transport power and heating sector imports and domestic production. Five brownfield candidates are compared to a greenfield candidate. The candidates differ by network length and pipeline diameters to consider the transported volume of hydrogen. The economic evaluation concludes that most brownfield candidates’ cost is significantly lower than those of the greenfield candidate. The candidates can serve as starting points for flow simulations and policymakers can estimate the cost based on the results.
How to Connect Energy Islands: Trade-offs Between Hydrogen and Electricity Infrastructure
Apr 2023
Publication
In light of offshore wind expansions in the North and Baltic Seas in Europe further ideas on using offshore space for renewable-based energy generation have evolved. One of the concepts is that of energy islands which entails the placement of energy conversion and storage equipment near offshore wind farms. Offshore placement of electrolysers will cause interdependence between the availability of electricity for hydrogen production and for power transmission to shore. This paper investigates the trade-offs between integrating energy islands via electricity versus hydrogen infrastructure. We set up a combined capacity expansion and electricity dispatch model to assess the role of electrolysers and electricity cables given the availability of renewable energy from the islands. We find that the electricity system benefits more from connecting close-to-shore wind farms via power cables. In turn electrolysis is more valuable for far-away energy islands as it avoids expensive long-distance cable infrastructure. We also find that capacity investment in electrolysers is sensitive to hydrogen prices but less to carbon prices. The onshore network and congestion caused by increased activity close to shore influence the sizing and siting of electrolysers.
Subcooled Liquid Hydrogen Technology for Heavy-Duty Trucks
Jan 2024
Publication
Subcooled liquid hydrogen (sLH2) is an onboard storage as well as a hydrogen refueling technology that is currently being developed by Daimler Truck and Linde to boost the mileage of heavy-duty trucks while also improving performance and reducing the complexity of hydrogen refueling stations. In this article the key technical aspects advantages challenges and future developments of sLH2 at vehicle and infrastructure levels will be explored and highlighted.
Design Investigation of Potential Long-Range Hydrogen Combustion Blended Wing Body Aircraft with Future Technologies
Jun 2023
Publication
Present work investigates the potential of a long-range commercial blended wing body configuration powered by hydrogen combustion engines with future airframe and propulsion technologies. Future technologies include advanced materials load alleviation techniques boundary layer ingestion and ultra-high bypass ratio engines. The hydrogen combustion configuration was compared to the configuration powered by kerosene with respect to geometric properties performance characteristics energy demand equivalent CO2 emissions and Direct Operating Costs. In addition technology sensitivity studies were performed to assess the potential influence of each technology on the configuration. A multi-fidelity sizing methodology using low- and mid-fidelity methods for rapid configuration sizing was created to assess the configuration and perform robust analyses and multi-disciplinary optimizations. To assess potential uncertainties of the fidelity of aerodynamic analysis tools high-fidelity aerodynamic analysis and optimization framework MACHAero was used for additional verification. Comparison of hydrogen and kerosene blended wing body aircraft showed a potential reduction of equivalent CO2 emission by 15% and 81% for blue and green hydrogen compared to the kerosene blended wing body and by 44% and 88% with respect to a conventional B777-300ER aircraft. Advancements in future technologies also significantly affect the geometric layout of aircraft. Boundary layer ingestion and ultra-high bypass ratio engines demonstrated the highest potential for fuel reduction although both technologies conflict with each other. However operating costs of hydrogen aircraft could establish a significant problem if pessimistic and base hydrogen price scenarios are achieved for blue and green hydrogen respectively. Finally configurational problems featured by classical blended wing body aircraft are magnified for the hydrogen case due to the significant volume requirements to store hydrogen fuel.
The Role of Hydrogen for the Defossilization of the German Chemical Industry
Apr 2023
Publication
Within the European Green Deal the European industry is summoned to transform towards a green and circular economy to reduce CO2-emissions and reach climate goals. Special focus is on the chemical industry to boost recycling processes for plastics exploit resource efficiency potentials and switch to a completely renewable feedstock (defossilization). Despite common understanding that drastic changes have to take place it is yet unknown how the industrial transformation should be accomplished. This work explains how a cost-optimal defossilization of the chemical industry in the context of national greenhouse gas (GHG) mitigation strategies look like. The central part of this investigation is based on a national energy system model to optimize the future energy system design of Germany as a case study for a highly industrialized country. A replacement of fossil-based feedstocks by renewable feedstocks leads to a significant increase in hydrogen demand by þ40% compared to a reference scenario. The resulting demand of hydrogen-based energy carriers including the demand for renewable raw materials must be produced domestically or imported. This leads to cumulative additional costs of the transformation that are 32% higher than those of a reference scenario without defossilization of the industry. Fischer-Tropsch synthesis and the methanol-to-olefins route can be identified as key technologies for the defossilization of the chemical industry.
Prospective Assessment of Transformation Pathways Toward Low-carbon Steelmaking: Evaluating Economic and Climate Impacts in Germany
Jan 2024
Publication
Due to climate change there is an urgent need to decarbonize high-emission industries. As coal-based operations predominate in primary steelmaking the steel industry offers an exceptionally high potential for reducing greenhouse gas emissions. Alternative processes for almost fully decarbonized primary steelmaking exist but require substantial investments by steelmakers for their implementation while maintaining desired production levels during the transformation periods. In this context the energy carriers required change such that the transformation of the steelmaking processes is deeply intertwined with the transformation of the background system. For the first time we evaluate potential transformation pathways from the steelmakers’ perspective using a prospective life cycle assessment approach. We find that hydrogen may facilitate a reduction of direct emissions by around 96 % compared to conventional steelmaking in 2050. However indirect emissions remain at a high level throughout the transformation period unless the upstream stages of the value chain are transformed accordingly.
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