Germany
Challenges of Industrial-Scale Testing Infrastructure for Green Hydrogen Technologies
Apr 2023
Publication
Green hydrogen is set to become the energy carrier of the future provided that production technologies such as electrolysis and solar water splitting can be scaled to global dimensions. Testing these hydrogen technologies on the MW scale requires the development of dedicated new test facilities for which there is no precedent. This perspective highlights the challenges to be met on the path to implementing a test facility for large-scale water electrolysis photoelectrochemical and photocatalytic water splitting and aims to serve as a much-needed blueprint for future test facilities based on the authors’ own experience in establishing the Hydrogen Lab Leuna. Key aspects to be considered are the electricity and utility requirements of the devices under testing the analysis of the produced H2 and O2 and the safety regulations for handling large quantities of H2 . Choosing the right location is crucial not only for meeting these device requirements but also for improving financial viability through supplying affordable electricity and providing a remunerated H2 sink to offset the testing costs. Due to their lower TRL and requirement for a light source large-scale photocatalysis and photoelectrochemistry testing are less developed and the requirements are currently less predictable.
Just Energy Transition: Learning from the Past for a More Just and Sustainable Hydrogen Transition in West Africa
Dec 2022
Publication
The rising demand for energy and the aim of moving away from fossil fuels and to low-carbon power have led many countries to move to alternative sources including solar energy wind geothermal energy biomass and hydrogen. Hydrogen is often considered a “missing link” in guaranteeing the energy transition providing storage and covering the volatility and intermittency of renewable energy generation. However due to potential injustice with regard to the distribution of risks benefits and costs (i.e. in regard to competing for land use) the large-scale deployment of hydrogen is a contested policy issue. This paper draws from a historical analysis of past energy projects to contribute to a more informed policy-making process toward a more just transition to the hydrogen economy. We perform a systematic literature review to identify relevant conflict factors that can influence the outcome of hydrogen energy transition projects in selected Economic Community of West African States countries namely Nigeria and Mali. To better address potential challenges policymakers must not only facilitate technology development access and market structures for hydrogen energy policies but also focus on energy access to affected communities. Further research should monitor hydrogen implementation with a special focus on societal impacts in producing countries.
Towards a Low-Carbon Society via Hydrogen and Carbon Capture and Storage: Social Acceptance from a Stakeholder Perspective
Apr 2020
Publication
Transformation concepts towards a low-carbon society often require new technology and infrastructure that evoke protests in the population. Therefore it is crucial to understand positions and conflicts in society to achieve social acceptance. This paper analyses these positions using the example of implementing hydrogen and carbon capture and storage infrastructure to decarbonise the German energy system. The empirical basis of the study are explorative stakeholder interviews which were conducted with experts from politics economics civil society and science and analysed within a discursive and attitudinal framework using qualitative content analysis. These stakeholder positions are assumed to represent dominant social perceptions and reflect chances and risks for acceptance. The results indicate different positions while pursuing the common goal of addressing climate change. The general conflict concerns strategies towards a low-carbon society especially the speed of phasing-out fossil energies. Regarding the combination of hydrogen and carbon capture and storage as instrument in the context of the energy transition the stakeholder interviews indicate controversial as well as consensual perceptions. The assessments range from rejection to deeming it absolutely necessary. Controversial argumentations refer to security of supply competitiveness and environmental protection. In contrast consensus can be reached by balancing ecological and economic arguments e.g. by linking hydrogen technologies with renewable and fossil energy sources or by limiting the use of carbon capture and storage only to certain applications (industry bioenergy). In further decisions this balancing of arguments combined with openness of technology transparency of information and citizen participation need to be considered to achieve broad acceptance.
Multi-Objective Optimization-Based Health-Conscious Predictive Energy Management Strategy for Fuel Cell Hybrid Electric Vehicles
Feb 2022
Publication
The Energy Management Strategy (EMS) in Fuel Cell Hybrid Electric Vehicles (FCHEVs) is the key part to enhance optimal power distribution. Indeed the most recent works are focusing on optimizing hydrogen consumption without taking into consideration the degradation of embedded energy sources. In order to overcome this lack of knowledge this paper describes a new health-conscious EMS algorithm based on Model Predictive Control (MPC) which aims to minimize the battery degradation to extend its lifetime. In this proposed algorithm the health-conscious EMS is normalized in order to address its multi-objective optimization. Then weighting factors are assigned in the objective function to minimize the selected criteria. Compared to most EMSs based on optimization techniques this proposed approach does not require any information about the speed profile which allows it to be used for real-time control of FCHEV. The achieved simulation results show that the proposed approach reduces the economic cost up to 50% for some speed profile keeping the battery pack in a safe range and significantly reducing energy sources degradation. The proposed health-conscious EMS has been validated experimentally and its online operation ability clearly highlighted on a PEMFC delivery postal vehicle.
Synergistic Value in Vertically Integrated Power-to-Gas Energy Systems
Oct 2019
Publication
In vertically integrated energy systems integration frequently entails operational gains that must be traded off against the requisite cost of capacity investments. In the context of the model analyzed in this study the operational gains are subject to inherent volatility in both the price and the output of the intermediate product transferred within the vertically integrated structure. Our model framework provides necessary and sufficient conditions for the value (NPV) of an integrated system to exceed the sum of two optimized subsystems on their own. We then calibrate the model in Germany and Texas for systems that combine wind energy with Power-to-Gas (PtG) facilities that produce hydrogen. Depending on the prices for hydrogen in different market segments we find that a synergistic investment value emerges in some settings. In the context of Texas for instance neither electricity generation from wind power nor hydrogen production from PtG is profitable on its own in the current market environment. Yet provided both subsystems are sized optimally in relative terms the attendant operational gains from vertical integration more than compensate for the stand-alone losses of the two subsystems.
Knowledge and Technology Transfer via Publications, Patents, Standards: Exploring the Hydrogen Technological Innovation System
Nov 2022
Publication
Clean technologies play a crucial role in reducing greenhouse gas emissions and protecting the climate. Hydrogen is a promising energy carrier and fuel that can be used in many applications. We explore the global hydrogen technological innovation system (TIS) by analyzing the three knowledge and technology transfer channels of publications patents and standards. Since the adoption of hydrogen technologies requires trust in their safety this study specifically also focuses on hydrogen safety. Our results show that general and hydrogen safety research has increased significantly while patenting experienced stagnation. An analysis of the non-patent literature in safety patents shows little recognition of scientific publications. Similarly publications are under-represented in the analyzed 75 international hydrogen and fuel cell standards. This limited transfer of knowledge from published research to standards points to the necessity for greater involvement of researchers in standardization. We further derive implications for the hydrogen TIS and recommendations for a better and more impactful alignment of the three transfer channels.
Artificial Intelligence/Machine Learning in Energy Management Systems, Control, and Optimization of Hydrogen Fuel Cell Vehicles
Mar 2023
Publication
Environmental emissions global warming and energy-related concerns have accelerated the advancements in conventional vehicles that primarily use internal combustion engines. Among the existing technologies hydrogen fuel cell electric vehicles and fuel cell hybrid electric vehicles may have minimal contributions to greenhouse gas emissions and thus are the prime choices for environmental concerns. However energy management in fuel cell electric vehicles and fuel cell hybrid electric vehicles is a major challenge. Appropriate control strategies should be used for effective energy management in these vehicles. On the other hand there has been significant progress in artificial intelligence machine learning and designing data-driven intelligent controllers. These techniques have found much attention within the community and state-of-the-art energy management technologies have been developed based on them. This manuscript reviews the application of machine learning and intelligent controllers for prediction control energy management and vehicle to everything (V2X) in hydrogen fuel cell vehicles. The effectiveness of data-driven control and optimization systems are investigated to evolve classify and compare and future trends and directions for sustainability are discussed.
How to Reduce the Greenhouse Gas Emissions and Air Pollution Caused by Light and Heavy Duty Vehicles with Battery-electric, Fuel Cell-electric and Catenary Trucks
Mar 2021
Publication
The reduction of greenhouse gas emissions is one of the greatest global challenges through 2050. Besides greenhouse gas emissions air pollution such as nitrogen oxide and particulate matter emissions has gained increasing attention in agglomerated areas with transport vehicles being one of the main sources thereof. Alternative fuels that fulfill the greenhouse gas reduction goals also offer the possibility of solving the challenge of rising urban pollution. This work focuses on the electric drive option for heavy and light duty vehicle freight transport. In this study fuel cell-electric vehicles battery-electric vehicles and overhead catenary line trucks were investigated taking a closer look at their potential to reduce greenhouse gas emissions and air pollution and also considering the investment and operating costs of the required infrastructure. This work was conducted using a bottom-up transport model for the federal state of North Rhine-Westphalia in Germany. Two scenarios for reducing these emissions were analyzed at a spatial level. In the first of these selected federal highways with the highest traffic volume were equipped with overhead catenary lines for the operation of diesel-hybrid overhead trucks on them. For the second spatial scenario the representative urban area of the city of Cologne was investigated in terms of air pollution shifting articulated trucks to diesel-hybrid overhead trucks and rigid trucks trailer trucks and light duty vehicles to battery-electric or fuel cell-electric drives. For the economic analysis the building up of a hydrogen infrastructure in the cases of articulated trucks and all heavy duty vehicles were also taken into account. The results showed that diesel-hybrid overhead trucks are only a cost-efficient solution for highways with high traffic volume whereas battery overhead trucks have a high uncertainty in terms of costs and technical feasibility. In general the broad range of costs for battery overhead trucks makes them competitive with fuel cell-electric trucks. Articulated trucks have the highest potential to be operated as overhead trucks. However the results indicated that air pollution is only partially reduced by switching conventional articulated trucks to electric drive models. The overall results show that a comprehensive approach such as fuel cell-electric drives for all trucks would most likely be more beneficial.
Efficiency and Optimal Load Capacity of E-Fuel-Based Energy Storage Systems
Apr 2023
Publication
This work evaluates the effectiveness of chemical-based solutions for storing large amounts of renewable electricity. Four “Power-to-X-to-Power” pathways are examined comprising hydrogen methane methanol and ammonia as energy carriers. The pathways are assessed using a model scenario where they are produced with electricity from an onshore wind farm stored in suitable facilities and then reconverted to electricity to meet the energy demand of a chemical site. An energy management and storage capacity estimation tool is used to calculate the annual load coverage resulting from each pathway. All four pathways offer a significant increase in load coverage compared to a scenario without storage solution (56.19%). The hydrogen-based pathway has the highest load coverage (71.88%) and round-trip efficiency (36.93%) followed by the ammonia-based (69.62% 31.37%) methanol-based (67.85% 27.00%) and methane-based (67.64% 26.47% respectively) pathways. The substantially larger storage capacity required for gaseous energy carriers to ensure a steady supply to the consumer could be a decisive factor. The hydrogen pathway requires a storage volume up to 10.93 times larger than ammonia and 16.87 times larger than methanol. Notably ammonia and methanol whose load coverages are only 2.26 and 4.03 percentage points lower than that of hydrogen offer the possibility of implementing site-specific storage solutions avoiding potential bottlenecks due to limited pipeline and cavern capacities.
Towards Climate-neutral Aviation: Assessment of Maintenance Requirements for Airborne Hydrogen Storage and Distribution Systems
Apr 2023
Publication
Airlines are faced with the challenge of reducing their environmental footprint in an effort to push for climate-neutral initiatives that comply with international regulations. In the past the aviation industry has followed the approach of incremental improvement of fuel efficiency while simultaneously experiencing significant growth in annual air traffic. With the increase in air traffic negating any reduction in Greenhouse Gas (GHG) emissions more disruptive technologies such as hydrogen-based onboard power generation are required to reduce the environmental impact of airline operations. However despite initial euphoria and first conceptual studies for hydrogen-powered aircraft several decades ago there still has been no mass adoption to this day. Besides the challenges of a suitable ground infrastructure this can partly be attributed to uncertainties with the associated maintenance requirements and the expected operating costs to demonstrate the economic viability of this technology. With this study we address this knowledge gap by estimating changes towards scheduled maintenance activities for an airborne hydrogen storage and distribution system. In particular we develop a detailed system design for a hydrogen-powered fuel-cell-based auxiliary power generation and perform a comparative analysis with an Airbus A320 legacy system. That analysis allows us to (a) identify changes for the expected maintenance effort to enhance subsequent techno-economic assessments (b) identify implications of specific design assumptions with corresponding maintenance activities while ensuring regulatory compliance and (c) describe the impact on the resulting task execution. The thoroughly examined interactions between system design and subsequent maintenance requirements of this study can support practitioners in the development of prospective hydrogen-powered aircraft. In particular it allows the inclusion of maintenance implications in early design stages of corresponding system architectures. Furthermore since the presented methodology is transferable to different design solutions it provides a blueprint for alternative operating concepts such as the complete substitution of kerosene by hydrogen to power the main engines.
How to Make Climate-neutral Aviation Fly
Jul 2023
Publication
The European aviation sector must substantially reduce climate impacts to reach net-zero goals. This reduction however must not be limited to flight CO2 emissions since such a narrow focus leaves up to 80% of climate impacts unaccounted for. Based on rigorous life-cycle assessment and a time-dependent quantification of non-CO2 climate impacts here we show that from a technological standpoint using electricity-based synthetic jet fuels and compensating climate impacts via direct air carbon capture and storage (DACCS) can enable climate-neutral aviation. However with a continuous increase in air traffic synthetic jet fuel produced with electricity from renewables would exert excessive pressure on economic and natural resources. Alternatively compensating climate impacts of fossil jet fuel via DACCS would require massive CO2 storage volumes and prolong dependence on fossil fuels. Here we demonstrate that a European climate-neutral aviation will fly if air traffic is reduced to limit the scale of the climate impacts to mitigate.
Techno-economic Assessment of Long-distance Supply Chains of Energy Carriers: Comparing Hydrogen and Iron for Carbon-free Electricity Generation
Mar 2023
Publication
The effective usage of renewable energy sources requires ways of storage and delivery to balance energy demand and availability divergences. Carbon-free chemical energy carriers are proposed solutions converting clean electricity into stable media for storage long-distance energy trade and on-demand electricity generation. Among them hydrogen (H2) is noteworthy being the subject of significant investment and research. Metal fuels such as iron (Fe) represent another promising solution for a clean energy supply but establishing an interconnected ecosystem still requires considerable research and development. This work proposes a model to assess the supply chain characteristics of hydrogen and iron as clean carbon-free energy carriers and then examines case studies of possible trade routes between the potential energy exporters Morocco Saudi Arabia and Australia and the energy importers Germany and Japan. The work comprises the assessment of economic (levelized cost of electricity - LCOE) energetic (thermodynamic efficiency) and environmental (CO2 emissions) aspects which are quantified by the comprehensive model accounting for the most critical processes in the supply chain. The assessment is complemented by sensitivity and uncertainty analyses to identify the main drivers for energy costs. Iron is shown to be lower-cost and more efficient to transport in longer routes and for long-term storage but potentially more expensive and less efficient than H2 to produce and convert. Uncertainties related to the supply chain specifications and the sensitivity to the used variables indicate that the path to viable energy carriers fundamentally depends on efficient synthesis conversion storage and transport. A break-even analysis demonstrated that clean energy carriers could be competitive with conventional energy carriers at low renewable energy prices while carbon taxes might be needed to level the playing field. Thereby green iron shows potential to become an important energy carrier for long-distance trade in a globalized clean energy market.
What is Stored, Why, and How? Mental Models, Knowledge, and Public Acceptance of Hydrogen Storage
Nov 2016
Publication
Although electricity storage plays a decisive role for the German “Energiewende” and it has become evident that the successful diffusion of technologies is not only a question of technical feasibility but also of social acceptance research on electricity storage technologies from a social science point of view is still scarce. This study therefore empirically explores laypersons’ mindsets and knowledge related to storage technologies focusing on hydrogen. While the results indicate overall supportive attitudes and trust in hydrogen storage some misconceptions a lack of information as well as concerns were identified which should be addressed in future communication concepts.
Investigation of Different Load Characteristics, Component Dimensioning, and System Scaling for the Optimized Design of a Hybrid Hydrogen-Based PV Energy System
Jul 2023
Publication
The realization of a carbon-neutral civilization which has been set as a goal for the coming decades goes directly hand-in-hand with the need for an energy system based on renewable energies (REs). Due to the strong weather-related daily and seasonal fluctuations in supply of REs suitable energy storage devices must be included for such energy systems. For this purpose an energy system model featuring hybrid energy storage consisting of a hydrogen unit (for long-term storage) and a lithium-ion storage device (for short-term storage) was developed. With a proper design such a system can ensure a year-round energy supply by using electricity generated by photovoltaics (PVs). In the energy system that was investigated hydrogen (H2) was produced by using an electrolyser (ELY) with a PV surplus during the summer months and then stored in an H2 tank. During the winter due to the lack of PV power the H2 is converted back into electricity and heat by a fuel cell (FC). While the components of such a system are expensive a resource- and cost-efficient layout is important. For this purpose a Matlab/Simulink model that enabled an energy balance analysis and a component lifetime forecast was developed. With this model the results of extensive parameter studies allowed an optimized system layout to be created for specific applications. The parameter studies covered different focal points. Several ELY and FC layouts different load characteristics different system scales different weather conditions and different load levels—especially in winter with variations in heating demand—were investigated.
Hydrogen as Energy Carrier: Techno-economic Assessment of Decentralized Hydrogen Production in Germany
Jun 2021
Publication
Political and scientific discussions on changing German energy supply mix and challenges of such energy transition are already well established. At the supply level energy storage seems to be the biggest challenge ahead for such transition. Hydrogen could be one of the solutions for future energy transition if it is produced using renewable energy resources. In order to analyze the future role of hydrogen its economic performance analysis is inevitable. This has been done in this research for a case study site in Cologne. The potential of hydrogen production with the use of solar electricity powered electrolyzers (alkaline and proton exchange membrane (PEM)) has been analyzed. Both grid connected and off grid modes of solar hydrogen production are considered. Economic performance results are presented for six scenarios. Hydrogen produced with the grid connected solar photovoltaics system coupled with alkaline electrolyzers was found the cheapest with the levelized cost of hydrogen (LCOH) at 6.23 V/kg. These costs are comparable with the current hydrogen price at commercial refueling station in Cologne. On the other hand the LCOH of off grid systems with both alkaline and PEM electrolyzers is expensive as expected the most expensive LCOH among six scenarios reached to 57.61 V/kg.
Ammonia Decomposition in the Process Chain for a Renewable Hydrogen Supply
Jun 2022
Publication
This review article deals with the challenge to identify catalyst materials from literature studies for the ammonia decomposition reaction with potential for application in large-scale industrial processes. On the one hand the requirements on the catalyst are quite demanding. Of central importance are the conditions for the primary reaction that have to be met by the catalyst. Likewise the catalytic performance i.e. an ideally quantitative conversion and a high lifetime are critical as well as the consideration of requirements on the product properties in terms of pressure or by-products for potential follow-up processes in this case synthesis gas applications. On the other hand the evaluation of the multitude of literature studies poses difficulties due to significant varieties in catalytic testing protocols.
Green Hydrogen from Anion Exchange Membrane Water Electrolysis: A Review of Recent Developments in Critical Materials and Operating Conditions
Mar 2020
Publication
Hydrogen production using water electrolysers equipped with an anion exchange membrane (AEM) a pure water feed and cheap components such as platinum group metal-free catalysts and stainless steel bipolar plates (BPP) can challenge proton exchange membrane (PEM) electrolysis systems as the state of the art. For this to happen the performance of the AEM electrolyzer must match the compact design stability H2 purity and high current densities of PEM systems. Current research aims at bringing AEM water electrolysis technology to an advanced level in terms of electrolysis cell performance. Such technological advances must be accompanied by demonstration of the cost advantages of AEM systems. The current state of the art in AEM water electrolysis is defined by sporadic reports in the academic literature mostly dealing with catalyst or membrane development. The development of this technology requires a future roadmap for systematic development and commercialization of AEM systems and components. This will include basic and applied research technology development & integration and testing at a laboratory scale of small demonstration units (AEM electrolyzer shortstacks) that can be used to validate the technology (from TRL 2–3 currently to TRL 4–5). This review paper gathers together recent important research in critical materials development (catalysts membranes and MEAs) and operating conditions (electrolyte composition cell temperature performance achievements). The aim of this review is to identify the current level of materials development and where improvements are required in order to demonstrate the feasibility of the technology. Once the challenges of materials development are overcome AEM water electrolysis can drive the future use of hydrogen as an energy storage vector on a large scale (GW) especially in developing countries.
Hydrogen Technology Towards the Solution of Environment-Friendly New Energy Vehicles
Aug 2021
Publication
The popularity of climate neutral new energy vehicles for reduced emissions and improved air quality has been raising great attention for many years. World-wide a strong commitment continues to drive the demand for zero-emission through alternative energy sources and propulsion systems. Despite the fact that 71.27% of hydrogen is produced from natural gas green hydrogen is a promising clean way to contribute to and maintain a climate neutral ecosystem. Thereby reaching CO2 targets for 2030 and beyond requires cross-sectoral changes. However the strong motivation of governments for climate neutrality is challenging many sectors. One of them is the transport sector as it is challenged to find viable all-in solutions that satisfy social economic and sustainable requirements. Currently the use of new energy vehicles operating on green sustainable hydrogen technologies such as batteries or fuel cells has been the focus for reducing the mobility induced emissions. In Europe 50% of the total emissions result from mobility. The following article reviews the background ongoing challenges and potentials of new energy vehicles towards the development of an environmentally friendly hydrogen economy. A change management process mindset has been adapted to discuss the key scientific and commercial challenges for a successful transition.
Derivation and Validation of a Reference Data-based Real Gas Model for Hydrogen
Mar 2023
Publication
Hydrogen plays an important role for the decarbonization of the energy sector. In its gaseous form it is stored at pressures of up to 1000 bar at which real gas effects become relevant. To capture these effects in numerical simulations accurate real gas models are required. In this work new correlation equations for relevant hydrogen properties are developed based on the Reference Fluid Thermodynamic and Transport Properties Database (REFPROP). Within the regarded temperature (150e400 K) and pressure (0.1e1000 bar) range this approach yields a substantially improved accuracy compared to other databased correlations. Furthermore the developed equations are validated in a numerical simulation of a critical flow Venturi nozzle. The results are in much better accordance with experimental data compared to a cubic equation of state model. In addition the simulation is even slightly faster.
Review and Harmonization of the Life-Cycle Global Warming Impact of PV-Powered Hydrogen Production by Electrolysis
Sep 2021
Publication
This work presents a review of life-cycle assessment (LCA) studies of hydrogen electrolysis using power from photovoltaic (PV) systems. The paper discusses the assumptions strengths and weaknesses of 13 LCA studies and identifies the causes of the environmental impact. Differences in assumptions of system boundaries system sizes evaluation methods and functional units make it challenging to directly compare the Global Warming Potential (GWP) resulting from different studies. To simplify this process 13 selected LCA studies on PV-powered hydrogen production have been harmonized following a consistent framework described by this paper. The harmonized GWP values vary from 0.7 to 6.6 kg CO2-eq/kg H2 which can be considered a wide range. The maximum absolute difference between the original and harmonized GWP results of a study is 1.5 kg CO2-eq/kg H2. Yet even the highest GWP of this study is over four times lower than the GWP of grid-powered electrolysis in Germany. Due to the lack of transparency of most LCAs included in this review full identification of the sources of discrepancies (methods applied assumed production conditions) is not possible. Overall it can be concluded that the environmental impact of the electrolytic hydrogen production process is mainly caused by the GWP of the electricity supply. For future environmental impact studies on hydrogen production systems it is highly recommended to 1) divide the whole system into well-defined subsystems using compression as the final stage of the LCA and 2) to provide energy inputs/GWP results for the different subsystems.
Hybrid Energy System Model in Matlab/Simulink Based on Solar Energy, Lithium‐Ion Battery and Hydrogen
Mar 2022
Publication
In this work a model of an energy system based on photovoltaics as the main energy source and a hybrid energy storage consisting of a short‐term lithium‐ion battery and hydrogen as the long‐term storage facility is presented. The electrical and the heat energy circuits and resulting flows have been modelled. Therefore the waste heat produced by the electrolyser and the fuel cell have been considered and a heat pump was considered to cover the residual heat demand. The model is designed for the analysis of a whole year energy flow by using a time series of loads weather and heat profile as input. This paper provides the main set of equations to derive the component properties and describes the implementation into MATLAB/Simulink. The novel model was created for an energy flow simulation over one year. The results of the simulation have been verified by comparing them with well‐established simulation results from HOMER Energy. It turns out that the novel model is well suited for the analysis of the dynamic system behaviour. Moreover different characteristics to achieve an energy balance an ideal dimensioning for the particular use case and further research possibilities of hydrogen use in the residential sector are covered by the novel model.
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.
Hydrogenization of Underground Storage of Natural Gas
Aug 2015
Publication
The intermittent production of the renewable energy imposes the necessity to temporarily store it. Large amounts of exceeding electricity can be stored in geological strata in the form of hydrogen. The conversion of hydrogen to electricity and vice versa can be performed in electrolyzers and fuel elements by chemical methods. The nowadays technical solution accepted by the European industry consists of injecting small concentrations of hydrogen in the existing storages of natural gas. The progressive development of this technology will finally lead to the creation of underground storages of pure hydrogen. Due to the low viscosity and low density of hydrogen it is expected that the problem of an unstable displacement including viscous fingering and gravity overriding will be more pronounced. Additionally the injection of hydrogen in geological strata could encounter chemical reactivity induced by various species of microorganisms that consume hydrogen for their metabolism. One of the products of such reactions is methane produced from Sabatier reaction between H2 and CO2. Other hydrogenotrophic reactions could be caused by acetogenic archaea sulfate-reducing bacteria and iron-reducing bacteria. In the present paper a mathematical model is presented which is capable to reflect the coupled hydrodynamic and bio-chemical processes in UHS. The model has been numerically implemented by using the open source code DuMuX developed by the University of Stuttgart. The obtained bio-chemical version of DuMuX was used to model the evolution of a hypothetical underground storage of hydrogen. We have revealed that the behavior of an underground hydrogen storage is different than that of a natural gas storage. Both the hydrodynamic and the bio-chemical effects contribute to the different characteristics.
Nested Decomposition Approach for Dispatch Optimization of Large-Scale, Integrated Electricity, Methane and Hydrogen Infrastructures
Apr 2022
Publication
Energy system integration enables raising operational synergies by coupling the energy infrastructures for electricity methane and hydrogen. However this coupling reinforces the infrastructure interdependencies increasing the need for integrated modeling of these infrastructures. To analyze the cost-efficient sustainable and secure dispatch of applied large-scale energy infrastructures an extensive and non-linear optimization problem needs to be solved. This paper introduces a nested decomposition approach with three stages. The method enables an integrated and full-year consideration of large-scale multi-energy systems in hourly resolution taking into account physical laws of power flows in electricity and gas transmission systems as boundary conditions. For this purpose a zooming technique successively reduces the temporal scope while first increasing the spatial and last the technical resolution. A use case proves the applicability of the presented approach to large-scale energy systems. To this end the model is applied to an integrated European energy system model with a detailed focus on Germany in a challenging transport situation. The use case demonstrates the temporal regional and cross-sectoral interdependencies in the dispatch of integrated energy infrastructures and thus the benefits of the introduced approach.
Hydrogen Blowdown Release Experiments at Different Temperatures in the Discha-facility
Sep 2021
Publication
In this work experiments on horizontal hydrogen jet releases from a 2.815 dm³ volume tank to the ambience are described. For the main experimental series tank valve and release line were cooled down to a temperature of approx. 80 K in a bath of liquid nitrogen. As a reference similar experiments were also performed with the uncooled tank at ambient temperature. The releases were carried out through four nozzles with different circular orifice diameters from 0.5 to 4 mm and started from initial tank pressures from 0.5 to 20 MPa (rel.). During the releases pressures and temperatures inside the vessel as well as inside the release line were measured. Outside the nozzle further temperature and hydrogen concentration measurements were performed along and besides the jet axis. The electrostatic field builtup in the jet was monitored using two field meters in different distances from the release nozzle and optical observation via photo and video-cameras was performed for the visualization of the H2-jet via the BOS-method. The experiments were performed in the frame of the EU-funded project PRESHLY in which several tests of this program were selected for a comparative computational study the results of which will also be presented at this conference. So on the one hand the paper gives a comprehensive description of the facility on the other hands it also describes the experimental procedure and the main findings.
Shock Tube Experiments on Flame Propagation Regimes and Critical Conditions for Flame Acceleration and Detonation Transition for Hydrogen-air Mixtures at Cryogenic Temperatures
Sep 2021
Publication
A series of more than 100 experiments with hydrogen-air mixtures at cryogenic temperatures have been performed in a shock tube in the frame of the PRESLHY project. A wide range of hydrogen concentrations from 8 to 60%H2 in the shock tube of the length of 5 m and 50 mm id was tested at cryogenic temperatures from 80 to 130K at ambient pressure. Flame propagation regimes were investigated for all hydrogen compositions in the shock tube at three different blockage ratios (BR) 0 0.3 and 0.6 as a function of initial temperature. Pressure sensors and InGaAs-photodiodes have been applied to monitor the flame and shock propagation velocity of the process. The experiments at ambient pressure and temperature were conducted as the reference data for cryogenic experiments. A critical expansion ratio for an effective flame acceleration to the speed of sound was experimentally found at cryogenic temperatures. The detonability criterion for smooth and obstructed channels was used to evaluate the detonation cell sizes at cryogenic temperatures as well. The main peculiarities of cryogenic combustion with respect to the safety assessment were that the maximum combustion pressure was several times higher compared to ambient temperature and the run-up-distance to detonation was several times shorter independent of lower chemical reactivity at cryogenic conditions.
Water Electrolysis: From Textbook Knowledge to the Latest Scientific Strategies and Industrial Developments
May 2022
Publication
Replacing fossil fuels with energy sources and carriers that are sustainable environmentally benign and affordable is amongst the most pressing challenges for future socio-economic development. To that goal hydrogen is presumed to be the most promising energy carrier. Electrocatalytic water splitting if driven by green electricity would provide hydrogen with minimal CO2 footprint. The viability of water electrolysis still hinges on the availability of durable earth-abundant electrocatalyst materials and the overall process efficiency. This review spans from the fundamentals of electrocatalytically initiated water splitting to the very latest scientific findings from university and institutional research also covering specifications and special features of the current industrial processes and those processes currently being tested in large-scale applications. Recently developed strategies are described for the optimisation and discovery of active and durable materials for electrodes that ever-increasingly harness first principles calculations and machine learning. In addition a technoeconomic analysis of water electrolysis is included that allows an assessment of the extent to which a large-scale implementation of water splitting can help to combat climate change. This review article is intended to cross-pollinate and strengthen efforts from fundamental understanding to technical implementation and to improve the ‘junctions’ between the field’s physical chemists materials scientists and engineers as well as stimulate much-needed exchange among these groups on challenges encountered in the different domains.
Power-to-Gas: Electrolysis and Methanation Status Review
Jun 2019
Publication
This review gives a worldwide overview on Power-to-Gas projects producing hydrogen or renewable substitute natural gas focusing projects in central Europe. It deepens and completes the content of previous reviews by including hitherto unreviewed projects and by combining project names with details such as plant location. It is based on data from 153 completed recent and planned projects since 1988 which were evaluated with regards to plant allocation installed power development plant size shares and amounts of hydrogen or substitute natural gas producing examinations and product utilization phases. Cost development for electrolysis and carbon dioxide methanation was analyzed and a projection until 2030 is given with an outlook to 2050.<br/>The results show substantial cost reductions for electrolysis as well as for methanation during the recent years and a further price decline to less than 500 euro per kilowatt electric power input for both technologies until 2050 is estimated if cost projection follows the current trend. Most of the projects examined are located in Germany Denmark the United States of America and Canada. Following an exponential global trend to increase installed power today's Power-to-Gas applications are operated at about 39 megawatt. Hydrogen and substitute natural gas were investigated on equal terms concerning the number of projects.
Investigation of an Intensified Thermo-Chemical Experimental Set-Up for Hydrogen Production from Biomass: Gasification Process Performance—Part I
Jun 2021
Publication
Biomass gasification for energy purposes has several advantages such as the mitigation of global warming and national energy independency. In the present work the data from an innovative and intensified steam/oxygen biomass gasification process integrating a gas filtration step directly inside the reactor are presented. The produced gas at the outlet of the 1 MWth gasification pilot plant was analysed in terms of its main gaseous products (hydrogen carbon monoxide carbon dioxide and methane) and contaminants. Experimental test sets were carried out at 0.25–0.28 Equivalence Ratio (ER) 0.4–0.5 Steam/Biomass (S/B) and 780–850 °C gasification temperature. Almond shells were selected as biomass feedstock and supplied to the reactor at approximately 120 and 150 kgdry/h. Based on the collected data the in-vessel filtration system showed a dust removal efficiency higher than 99%-wt. A gas yield of 1.2 Nm3dry/kgdaf and a producer gas with a dry composition of 27–33%v H2 23–29%v CO 31–36%v CO2 9–11%v CH4 and light hydrocarbons lower than 1%v were also observed. Correspondingly a Low Heating Value (LHV) of 10.3–10.9 MJ/Nm3dry and a cold gas efficiency (CGE) up to 75% were estimated. Overall the collected data allowed for the assessment of the preliminary performances of the intensified gasification process and provided the data to validate a simulative model developed through Aspen Plus software.
A Policy Review of Green Hydrogen Economy in Southern Africa
Nov 2021
Publication
Renewable energy and clean energy have been on the global agenda for energy transition for quite a long time but recently gained strong momentum especially with the anticipated depletion of fossil fuels alongside increasing environmental degradation from their exploitation and the changing climate caused by their excessive carbon emissions. Despite this Africa’s pursuit to transition to a green economy using renewable energy resources still faces constraints that hamper further development and commercialization. These may include socio-economic technical political financial and institutional policy framework barriers. Although hydrogen demand is still low in Southern Africa the region can meet the global demands for green hydrogen as a major supplier because of its enormous renewable energy resource-base. This article reviews existing renewable energy resources and hydrogen energy policies in the Southern African Development Community (SADC). The significance of this review is that it explores how clean energy technologies that utilize renewable energy resources address the United Nations sustainable development goals (UN SDGs) and identifies the hydrogen energy policy gaps. This review further presents policy options and recommends approaches to enhance hydrogen energy production and ramp the energy transition from a fossil fuel-based economy to a hydrogen energy-based economy in Southern Africa. Concisely the transition can be achieved if the existing hydrogen energy policy framework gap is narrowed by formulating policies that are specific to hydrogen development in each country with the associated economic benefits of hydrogen energy clearly outlined.
Cost Benefits of Optimizing Hydrogen Storage and Methanation Capacities for Power-to-Gas Plants in Dynamic Operation
Oct 2019
Publication
Power-to-Gas technologies offer a promising approach for converting renewable electricity into a molecular form (fuel) to serve the energy demands of non-electric energy applications in all end-use sectors. The technologies have been broadly developed and are at the edge of a mass roll-out. The barriers that Power-to-Gas faces are no longer technical but are foremost regulatory and economic. This study focuses on a Power-to-Gas pathway where electricity is first converted in a water electrolyzer into hydrogen which is then synthetized with carbon dioxide to produce synthetic natural gas. A key aspect of this pathway is that an intermittent electricity supply could be used which could reduce the amount of electricity curtailment from renewable energy generation. Interim storages would then be necessary to decouple the synthesized part from hydrogen production to enable (I) longer continuous operation cycles for the methanation reactor and (II) increased annual full-load hours leading to an overall reduction in gas production costs. This work optimizes a Power-to-Gas plant configuration with respect to the cost benefits using a Monte Carlo-based simulation tool. The results indicate potential cost reductions of up to 17% in synthetic natural gas production by implementing well-balanced components and interim storages. This study also evaluates three different power sources which differ greatly in their optimal system configuration. Results from time-resolved simulations and sensitivity analyses for different plant designs and electricity sources are discussed with respect to technical and economic implications so as to facilitate a plant design process for decision makers.
Numerical Simulations of Suppression Effect of Water Mist on Hydrogen Deflagration in Confined Spaces
Sep 2021
Publication
Hydrogen safety issues attract focuses increasingly as more and more hydrogen powered vehicles are going to be operated in traffic infrastructures of different kinds like tunnels. Due to the confinement feature of traffic tunnels hydrogen deflagration may pose a risk when a hydrogen leak event occurs in a tunnel e.g. failure of the hydrogen storage system caused by a car accident in a tunnel. A water injection system can be designed in tunnels as a mitigation measure to suppress the pressure and thermal loads of hydrogen combustion in accident scenarios. The COM3D is a fully verified three-dimensional finite-difference turbulent flow combustion code which models gas mixing hydrogen combustion and detonation in nuclear containment with mitigation device or other confined facilities like vacuum vessel of fusion and semi-confined hydrogen facilities in industry such as traffic tunnels hydrogen refueling station etc. Therefore by supporting of the European HyTunnel-CS project the COM3D is applied to simulate numerically the hydrogen deflagration accident in a tunnel model being suppressed by water mist injection. The suppression effect of water mist and the suppression mechanism is elaborated and discussed in the study.
Steel Manufacturing Clusters in a Hydrogen Economy – Simulation of Changes in Location and Vertical Integration of Steel Production in Northwestern Europe
Feb 2022
Publication
With the move to a hydrogen-based primary steel production envisioned for the near future in Europe existing regional industrial clusters loose major assets. Such a restructuring of industries may result in a new geographical distribution of the steel industry and also to another quality of vertical integration at sites. Both implications could turn out as drivers or barriers to invest in new technologies and are thus important in respect to vertical integration of sites and to regional policy. This paper describes an approach to model production stock invest for the steel industries in North-Western Europe. Current spatial structures are reproduced with capacity technical and energy efficiency data on the level of single facilities like blast furnaces. With the model developed both investments in specific technologies and at specific production sites can be modelled. The model is used to simulate different possible future scenarios. The case with a clear move to hydrogen-based production is compared to a reference scenario without technological shift. The scenarios show that existing trends like movement of production to the coast may be accelerated by the new technology but that sites in the hinterland can also adapt to a hydrogen economy. Possible effects of business cycles or a circular economy on regional value chains are explored with a Monte-Carlo analysis.
Economic Optima for Buffers in Direct Reduction Steelmaking Under Increasing Shares of Renewable Hydrogen
Oct 2021
Publication
While current climate targets demand substantial reductions in greenhouse gas (GHG) emissions the potentials to further reduce carbon dioxide emissions in traditional primary steel-making are limited. One possible solution that is receiving increasing attention is the direct reduction (DR) technology operated either with renewable hydrogen (H2) from electrolysis or with conventional natural gas (NG). DR technology makes it possible to decouple steel and hydrogen production by temporarily using overcapacities to produce and store intermediary products during periods of low renewable electricity prices or by switching between H2 and NG. This paper aims to explore the impact of this decoupling on overall costs and the corresponding dimensioning of production and storage capacities. An optimization model is developed to determine the least-cost operation based on perfect-foresight. This model can determine the minimum costs for optimal production and storage capacities under various assumptions considering fluctuating H2 and NG prices and increasing H2 shares. The model is applied to a case study for Germany and covers the current situation the medium term until 2030 and the long term until 2050. Under the assumptions made the role of using direct reduced iron (DRI) storage as a buffer seems less relevant. DRI mainly serves as long-term storage for several weeks similar to usual balancing storage capacities. Storing H2 on the contrary is used for short-term fluctuations and could balance H2 demand in the hourly range until 2050. From an economic perspective DRI production using NG tends to be cheaper than using H2 in the short term and potential savings from the flexible operation with storages are small at first. However in the long term until 2050 NG and H2 could achieve similar total costs if buffers are used. Otherwise temporarily occurring electricity price spikes imply substantial increases in total costs if high shares of H2 need to be achieved.
Investigation on Cooling Effect of Water Sprays on Tunnel Fires of Hydrogen
Sep 2021
Publication
As one of the most promising renewable green energies hydrogen power is a popularly accepted option to drive automobiles. Commercial application of fuel cell vehicles has been started since 2015. More and more hydrogen safety concerns have been considered for years. Tunnels are an important part of traffic infrastructure with a mostly confined feature. Hydrogen leak followed possibly by a hydrogen fire is a potential accident scenario which can be triggered trivially by a car accident while hydrogen powered vehicles operate in a tunnel. Water spray is recommended traditionally as a mitigation measure against tunnel fires. The interaction between water spray and hydrogen fire is studied in a way of numerical simulations. By using the computer program of Fire Dynamics Simulator (FDS) tunnel fires of released hydrogen in different scales are simulated coupled with water droplet injections featured in different droplet sizes or varying mass flow rates. The cooling effect of spray on hot gases of hydrogen fires is apparently observed in the simulations. However in some circumstance the turbulence intensified by the water injection can prompt hydrogen combustion which is a negative side-effect of the spray.
Towards the Efficient and Time-accurate Simulations of Early Stages of Industrial Explosions
Sep 2021
Publication
Combustion during a nuclear reactor accident can result in pressure loads that are potentially fatal for the structural integrity of the reactor containment or its safety equipment. Enabling efficient modelling of such safety-critical scenarios is the goal of ongoing work. In this paper attention is given to capturing early phases of flame propagation. Transient simulations that are not prohibitively expensive for use at industrial scale are required given that a typical flame propagation study takes a large number of simulation time steps to complete. An improved numerical method used in this work is based on explicit time integration by means of Strong Stability Preserving (SSP) Runge-Kutta schemes. These allow an increased time step size for a given level of accuracy—reducing the overall computational effort. Furthermore a wide range of flow conditions is encountered in analysis of accelerating flames: from incompressible to potentially supersonic. In contrast numerical schemes for spatial discretization would often prove lacking in either stability or accuracy outside the intended flow regime—with density-based schemes being traditionally designed and applied to compressible (Ma>0.3) flows. In the present work a formulation of an all-speed density-based numerical flux scheme is used for simulation of slow flames starting from ignition. Validation was carried out using experiments with spherical lean hydrogen flames at laboratory scale. Turbulence conditions in the experiments correspond to those that can arise in a nuclear reactor containment during an accident. Results show that the new numerical method has the potential to predict flame speed and pressure rise at a reduced computational effort.
Development of Hydrogen Storage Tank Systems Based on Complex Metal Hydrides
Sep 2015
Publication
This review describes recent research in the development of tank systems based on complex metal hydrides for thermolysis and hydrolysis. Commercial applications using complex metal hydrides are limited especially for thermolysis-based systems where so far only demonstration projects have been performed. Hydrolysis-based systems find their way in space naval military and defense applications due to their compatibility with proton exchange membrane (PEM) fuel cells. Tank design modeling and development for thermolysis and hydrolysis systems as well as commercial applications of hydrolysis systems are described in more detail in this review. For thermolysis mostly sodium aluminum hydride containing tanks were developed and only a few examples with nitrides ammonia borane and alane. For hydrolysis sodium borohydride was the preferred material whereas ammonia borane found less popularity. Recycling of the sodium borohydride spent fuel remains an important part for their commercial viability.
Flexible Electricity Use for Heating in Markets with Renewable Energy
Mar 2020
Publication
Using electricity for heating can contribute to decarbonization and provide flexibility to integrate variable renewable energy. We analyze the case of electric storage heaters in German 2030 scenarios with an open-source electricity sector model. We find that flexible electric heaters generally increase the use of generation technologies with low variable costs which are not necessarily renewables. Yet making customary night-time storage heaters temporally more flexible offers only moderate benefits because renewable availability during daytime is limited in the heating season. Respective investment costs accordingly have to be very low in order to realize total system cost benefits. As storage heaters feature only short-term heat storage they also cannot reconcile the seasonal mismatch of heat demand in winter and high renewable availability in summer. Future research should evaluate the benefits of longer-term heat storage.
A Review of the MSCA ITN ECOSTORE—Novel Complex Metal Hydrides for Efficient and Compact Storage of Renewable Energy as Hydrogen and Electricity
Mar 2020
Publication
Hydrogen as an energy carrier is very versatile in energy storage applications. Developments in novel sustainable technologies towards a CO2-free society are needed and the exploration of all-solid-state batteries (ASSBs) as well as solid-state hydrogen storage applications based on metal hydrides can provide solutions for such technologies. However there are still many technical challenges for both hydrogen storage material and ASSBs related to designing low-cost materials with low-environmental impact. The current materials considered for all-solid-state batteries should have high conductivities for Na+ Mg2+ and Ca2+ while Al3+-based compounds are often marginalised due to the lack of suitable electrode and electrolyte materials. In hydrogen storage materials the sluggish kinetic behaviour of solid-state hydride materials is one of the key constraints that limit their practical uses. Therefore it is necessary to overcome the kinetic issues of hydride materials before discussing and considering them on the system level. This review summarizes the achievements of the Marie Skłodowska-Curie Actions (MSCA) innovative training network (ITN) ECOSTORE the aim of which was the investigation of different aspects of (complex) metal hydride materials. Advances in battery and hydrogen storage materials for the efficient and compact storage of renewable energy production are discussed.
Decentral Production of Green Hydrogen for Energy Systems: An Economically and Environmentally Viable Solution for Surplus Self-Generated Energy in Manufacturing Companies?
Feb 2023
Publication
Power-to-X processes where renewable energy is converted into storable liquids or gases are considered to be one of the key approaches for decarbonizing energy systems and compensating for the volatility involved in generating electricity from renewable sources. In this context the production of “green” hydrogen and hydrogen-based derivatives is being discussed and tested as a possible solution for the energy-intensive industry sector in particular. Given the sharp ongoing increases in electricity and gas prices and the need for sustainable energy supplies in production systems non-energy-intensive companies should also be taken into account when considering possible utilization paths for hydrogen. This work focuses on the following three utilization paths: “hydrogen as an energy storage system that can be reconverted into electricity” “hydrogen mobility” for company vehicles and “direct hydrogen use”. These three paths are developed modeled simulated and subsequently evaluated in terms of economic and environmental viability. Different photovoltaic system configurations are set up for the tests with nominal power ratings ranging from 300 kWp to 1000 kWp. Each system is assigned an electrolyzer with a power output ranging between 200 kW and 700 kW and a fuel cell with a power output ranging between 5 kW and 75 kW. There are also additional variations in relation to the battery storage systems within these basic configurations. Furthermore a reference variant without battery storage and hydrogen technologies is simulated for each photovoltaic system size. This means that there are ultimately 16 variants to be simulated for each utilization path. The results show that these utilization paths already constitute a reasonable alternative to fossil fuels in terms of costs in variants with a suitable energy system design. For the “hydrogen as an energy storage system” path electricity production costs of between 43 and 79 ct/kWh can be achieved with the 750 kWp photovoltaic system. The “hydrogen mobility” is associated with costs of 12 to 15 ct/km while the “direct hydrogen use” path resulted in costs of 8.2 €/kg. Environmental benefits are achieved in all three paths by replacing the German electricity mix with renewable energy sources produced on site or by substituting hydrogen for fossil fuels. The results confirm that using hydrogen as a storage medium in manufacturing companies could be economically and environmentally viable. These results also form the basis for further studies e.g. on detailed operating strategies for hydrogen technologies in scenarios involving a combination of multiple utilization paths. The work also presents the simulation-based method developed in this project which can be transferred to comparable applications in further studies.
Technical Reliability of Shipboard Technologies for the Application of Alternative Fuels
Jul 2022
Publication
Background: Naval trafc is highly dependent on depleting fossil resources and causes signifcant greenhouse gas emissions. At the same time marine transportation is a major backbone of world trade. Thus alternative fuel concepts are highly needed. Diferent fuels such as ammonia methanol liquefed natural gas and hydrogen have been proposed. For some of them frst prototype vessels have been in operation. However practical experience is still limited. Most studies so far focus on aspects such as efciency and economics. However particularly in marine applications reliability of propulsion systems is of utmost importance because failures on essential ship components at sea pose a huge safety risk. If the respective components lose their functionality repair can be much more challenging due to large distances to dockyards and the complicated transport of spare parts to the ship. Consequently evaluation of reliability should be a core element of system analysis for new marine fuels. Results: In this study reliability was studied for four potential fuels. The analysis involved several steps: estimation of overall failure rates identifcation of most vulnerable components and assessment of criticality by including severity of fault events. On the level of overall failure rate ammonia is shown to be very promising. Extending the view over a pure failure rate-based evaluation shows that other approaches such as LOHC or methanol can be competitive in terms of reliability and risk. As diferent scenarios require diferent weightings of the diferent reliability criteria the conclusion on the best technology can difer. Relevant aspects for this decision can be the availability of technical staf high-sea or coastal operation the presence of non-naval personnel onboard and other factors. Conclusions: The analysis allowed to compare diferent alternative marine fuel concepts regarding reliability. However the analysis is not limited to assessment of overall failure rates but can also help to identify critical elements that deserve attention to avoid fault events. As a last step severity of the individual failure modes was included. For the example of ammonia it is shown that the decomposition unit and the fuel cell should be subject to measures for increasing safety and reducing failure rates.
A Novel Framework for Development and Optimisation of Future Electricity Scenarios with High Penetration of Renewables and Storage
May 2019
Publication
Although electricity supply is still dominated by fossil fuels it is expected that renewable sources will have a much larger contribution in the future due to the need to mitigate climate change. Therefore this paper presents a new framework for developing Future Electricity Scenarios (FuturES) with high penetration of renewables. A multi-period linear programming model has been created for power-system expansion planning. This has been coupled with an economic dispatch model PowerGAMA to evaluate the technical and economic feasibility of the developed scenarios while matching supply and demand. Application of FuturES is demonstrated through the case of Chile which has ambitious plans to supply electricity using only renewable sources. Four cost-optimal scenarios have been developed for the year 2050 using FuturES: two Business as usual (BAU) and two Renewable electricity (RE) scenarios. The BAU scenarios are unconstrained in terms of the technology type and can include all 11 options considered. The RE scenarios aim to have only renewables in the mix including storage. The results show that both BAU scenarios have a levelised cost of electricity (LCOE) lower than or equal to today’s costs ($72.7–77.3 vs $77.6/MWh) and include 81–90% of renewables. The RE scenarios are slightly more expensive than today’s costs ($81–87/MWh). The cumulative investment for the BAU scenarios is $123-$145 bn compared to $147-$157 bn for the RE. The annual investment across the scenarios is estimated at $4.0 ± 0.4 bn. Both RE scenarios show sufficient flexibility in matching supply and demand despite solar photovoltaics and wind power contributing around half of the total supply. Therefore the FuturES framework is a powerful tool for aiding the design of cost-efficient power systems with high penetration of renewables.
Are Sustainable Aviation Fuels a Viable Option for Decarbonizing Air Transport in Europe? An Environmental and Economic Sustainability Assessment
Jan 2022
Publication
The use of drop-in capable alternative fuels in aircraft can support the European aviation sector to achieve its goals for sustainable development. They can be a transitional solution in the short and medium term as their use does not require any structural changes to the aircraft powertrain. However the production of alternative fuels is often energy-intensive and some feedstocks are associated with harmful effects on the environment. In addition alternative fuels are often more expensive to produce than fossil kerosene which can make their use unattractive. Therefore this paper analyzes the environmental and economic impacts of four types of alternative fuels compared to fossil kerosene in a well-to-wake perspective. The fuels investigated are sustainable aviation fuels produced by power-to-liquid and biomass-to-liquid pathways. Life cycle assessment and life cycle costing are used as environmental and economic assessment methods. The results of this well-towake analysis reveal that the use of sustainable aviation fuels can reduce the environmental impacts of aircraft operations. However an electricity mix based on renewable energies is needed to achieve significant reductions. In addition from an economic perspective the use of fossil kerosene ranks best among the alternatives. A scenario analysis confirms this result and shows that the production of sustainable aviation fuels using an electricity mix based solely on renewable energy can lead to significant reductions in environmental impact but economic competitiveness remains problematic.
Economic Evaluation of Low-carbon Steelmaking via Coupling of Electrolysis and Direct Reduction
Oct 2021
Publication
The transition from fossil-based primary steel production to a low-emission alternative has gained increasing attention in recent years. Various schemes including Carbon Capture and Utilization (CCU) and Carbon Direct Avoidance (CDA) via hydrogen-based as well as electrochemical routes have been proposed. With multiple technical analyses being available and technical feasibility being proven by first pilot plants pathways towards commercial market entry are of increasing interest. While multiple publications on the economic feasibility of CCU are available data on CDA approaches is scarce. In this work an economic model for the quantification of production cost as well as CO2 emission mitigation cost is presented. The approach is characterized by a seamless integration with a flowsheet-based process model of a direct reduction-based crude steel production plant detailed in a previous work and allows for the investigation of multiple economic aspects. Firstly the gradual transition from the natural gas-based state-of-the-art direct reduction towards a fossil-free hydrogen-based reduction is analyzed. Furthermore a comparison between the more mature technology of low-temperature electrolysis and a potentially more efficient solid oxide electrolysis (SOEL) is given highlighting the potential of SOEL technology. The conducted forecast to 2050 shows that SOEL-based CDA offers lower production cost when technological maturity is reached. Based on the results of the economic assessment possible legislative support mechanisms are studied showing that legislative actions are necessary to allow for market entry as well as for sustainable and economically feasible operation of fossil-free direct reduction plants.
Hydrogen Supply Chain Scenarios for the Decarbonisation of a German Multi-modal Energy System
Sep 2021
Publication
Analysing hydrogen supply chains is of utmost importance to adequately understand future energy systems with a high degree of sector coupling. Here a multi-modal energy system model is set up as linear programme incorporating electricity natural gas as well as hydrogen transportation options for Germany in 2050. Further different hydrogen import routes and optimised inland electrolysis are included. In a sensitivity analysis hydrogen demands are varied to cover uncertainties and to provide scenarios for future requirements of a hydrogen supply and transportation infrastructure. 80% of the overall hydrogen demand of 150 TWh/a emerge in Northern Germany due to optimised electrolyser locations and imports which subsequently need to be transported southwards. Therefore a central hydrogen pipeline connection from Schleswig-Holstein to the region of Darmstadt evolves already for moderate demands and appears to be a no-regret investment. Furthermore a natural gas pipeline reassignment potential of 46% is identified.
Aluminium Redox Cycle in Comparison to Pressurized Hydrogen for the Energy Supply of Multi-family Houses
Nov 2022
Publication
Power-to-X technologies that convert renewable electricity to chemically stored energy in “X” may provide a gaseous liquid or solid fuel that can be used in winter to provide both heat and electricity and thus replace fossil fuels that are currently used in many countries with cold winters. This contribution compares two options for power-to-X technologies for providing heat and electricity supply of buildings with high solar photovoltaic coverage at times of low solar availability. The option “compressed hydrogen” is based on water electrolysis that produces hydrogen on-site. This hydrogen is subsequently compressed and stored at high pressure (350 bar) for use in winter by a fuel cell. The option “aluminium redox-cycle” includes an inert electrode high temperature electrolysis process that is carried out at industrial scale. Produced aluminium is subseqeuntly transported to the site of use and converted to hydrogen and heat – and finally to electricity and heat - by aluminium-water reaction in combination with a fuel cell. Results of cost and LCA analysis show that the overall energetic efficiency of the compressed hydrogen process is slightly higher than for the aluminium redox cycle. However the aluminium redox-cycles needs far less on-site storage volume and is likely to become available at lower investment cost for the end user. Total annual cost of ownership and global warming potential of the two options are quite similar.
Green Hydrogen Production and Use in Low- and Middle-income Countries: A Least-cost Geospatial Modelling Approach Applied to Kenya
May 2023
Publication
With the rising threat of climate change green hydrogen is increasingly seen as the high-capacity energy storage and transport medium of the future. This creates an opportunity for low- and middle-income countries to leverage their high renewable energy potential to produce use and export low-cost green hydrogen creating environmental and economic development benefits. While identifying ideal locations for green hydrogen production is critical for countries when defining their green hydrogen strategies there has been a paucity of adequate geospatial planning approaches suitable to low- and middle-income countries. It is essential for these countries to identify green hydrogen production sites which match demand to expected use cases such that their strategies are economically sustainable. This paper therefore develops a novel geospatial cost modelling method to optimize the location of green hydrogen production across different use cases with a focus on suitability to low- and middle-income countries. This method is applied in Kenya to investigate the potential hydrogen supply chain for three use cases: ammonia-based fertilizer freight transport and export. We find hydrogen production costs of e3.7–9.9/kgH2 are currently achievable across Kenya depending on the production location chosen. The cheapest production locations are identified to the south and south-east of Lake Turkana. We show that ammonia produced in Kenya can be cost-competitive given the current energy crisis and that Kenya could export hydrogen to Rotterdam with costs of e7/kgH2 undercutting current market prices regardless of the carrier medium. With expected techno-economic improvements hydrogen production costs across Kenya could drop to e1.8–3.0/kgH2 by 2030.
Solar Hydrogen Fuel Generation from Wastewater—Beyond Photoelectrochemical Water Splitting: A Perspective
Oct 2022
Publication
Green hydrogen—a carbon-free renewable fuel—has the capability to decarbonise a variety of sectors. The generation of green hydrogen is currently restricted to water electrolysers. The use of freshwater resources and critical raw materials however limits their use. Alternative water splitting methods for green hydrogen generation via photocatalysis and photoelectrocatalysis (PEC) have been explored in the past few decades; however their commercial potential still remains unexploited due to the high hydrogen generation costs. Novel PEC-based simultaneous generation of green hydrogen and wastewater treatment/high-value product production is therefore seen as an alternative to conventional water splitting. Interestingly the organic/inorganic pollutants in wastewater and biomass favourably act as electron donors and facilitate the dual-functional process of recovering green hydrogen while oxidising the organic matter. The generation of green hydrogen through the dual-functional PEC process opens up opportunities for a “circular economy”. It further enables the end-of-life commodities to be reused recycled and resourced for a better life-cycle design while being economically viable for commercialisation. This review brings together and critically analyses the recent trends towards simultaneous wastewater treatment/biomass reforming while generating hydrogen gas by employing the PEC technology. We have briefly discussed the technical challenges associated with the tandem PEC process new avenues techno-economic feasibility and future directions towards achieving net neutrality.
Measurement and Modeling on Hydrogen Jet and Combustion from a Pressurize Vessel
Sep 2021
Publication
Hydrogen safety is an important topic for hydrogen energy application. Unintended hydrogen releases and combustions are potential accident scenarios which are of great interest for developing and updating the safety codes and standards. In this paper hydrogen releases and delayed ignitions were studied.
Overview of First Outcomes of PNR Project HYTUNNEL-CS
Sep 2021
Publication
Dmitry Makarov,
Donatella Cirrone,
Volodymyr V. Shentsov,
Sergii Kashkarov,
Vladimir V. Molkov,
Z. Xu,
Mike Kuznetsov,
Alexandros G. Venetsanos,
Stella G. Giannissi,
Ilias C. Tolias,
Knut Vaagsaether,
André Vagner Gaathaug,
Mark R. Pursell,
W. M. Rattigan,
Frank Markert,
Luisa Giuliani,
L.S. Sørensen,
A. Bernad,
Mercedes Sanz Millán,
U. Kummer,
C. Brauner,
Paola Russo,
J. van den Berg,
F. de Jong,
Tom Van Esbroeck,
M. Van De Veire,
D. Bouix,
Gilles Bernard-Michel,
Sergey Kudriakov,
Etienne Studer,
Domenico Ferrero,
Joachim Grüne and
G. Stern
The paper presents the first outcomes of the experimental numerical and theoretical studies performed in the funded by Fuel Cell and Hydrogen Joint Undertaking (FCH2 JU) project HyTunnel-CS. The project aims to conduct pre-normative research (PNR) to close relevant knowledge gaps and technological bottlenecks in the provision of safety of hydrogen vehicles in underground transportation systems. Pre normative research performed in the project will ultimately result in three main outputs: harmonised recommendations on response to hydrogen accidents recommendations for inherently safer use of hydrogen vehicles in underground traffic systems and recommendations for RCS. The overall concept behind this project is to use inter-disciplinary and inter-sectoral prenormative research by bringing together theoretical modelling and experimental studies to maximise the impact. The originality of the overall project concept is the consideration of hydrogen vehicle and underground traffic structure as a single system with integrated safety approach. The project strives to develop and offer safety strategies reducing or completely excluding hydrogen-specific risks to drivers passengers public and first responders in case of hydrogen vehicle accidents within the currently available infrastructure.
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