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Item type:Publication, Access status: with files , A simulation-based approach to assess the energy consumption and operational feasibility of hydrogen-powered port equipmentReplacing diesel-powered container handling equipment with zero-emission drivetrains offers major environmental benefits but raises concerns about operational feasibility. This work introduces a scalable simulation approach based on graph networks to estimate the energy consumption of container handling equipment. The method is employed to assess how operational conditions and vehicle configurations influence the operational feasibility for hydrogen-powered terminal tractors and straddle carriers. A systematic parameter variation examines the influence of driver behaviour, operational factors, and technical specifications on energy demand and operational range. Results indicate that hydrogen fuel cell systems can meet individual performance requirements of container terminal operations. Payload and driver behaviour govern the energy consumption, while tailoring tank and battery sizes to the intended application enhances feasibility. The findings provide guidance for designing and operating zero-emission container handling equipment in diverse terminal environments.Publicationtype: Journal Article18 11 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Comparison of the design and operation of various fossil-free ferry topologies with a conventional diesel-powered propulsion system – An optimization-based techno-economic-environmental analysisTo meet global greenhouse gas (GHG) reduction goals, the shipping sector must also be defossilized. Hydrogen-powered systems could be particularly advantageous for short- and medium-range routes, such as ferries for river or strait crossings. For such applications, metal hydrides offer a promising way to store the hydrogen needed to power the respective ship's propulsion system. In such metal hydrides, hydrogen can be stored safely and without any storage losses under ambient conditions (pressure/temperature). To evaluate the suitability of these metal hydride storage systems as part of a hydrogen-powered propulsion system on ships, the design and operation of ships with metal hydride storage systems must be examined in direct comparison with battery-driven and diesel-powered systems. Therefore, the overarching goal of this paper is based on an optimization-based approach to investigate how a metal hydride system can be operated and designed in a technically and economically viable manner. Furthermore, the environmental performance resulting from such a system is analyzed. The findings show that fuel costs (hydrogen system: 92%, battery system: 85% of total costs) significantly affect the economic viability. Compared to a battery-powered system and a diesel-driven system, the hydrogen-powered system requires the least amount of space. It remains a viable option even with less favorable discharge rates (ranging from 0.03 to 1.0 kW/kWh) of the metal hydride storage system. Thus, if the hydrogen fuel costs decline in the future, such a hydrogen-powered propulsion system for ships could be an alternative to pure battery-based systems. Additionally, the hydrogen-powered system can significantly reduce greenhouse gas emissions compared to a diesel-powered system as long as “green” hydrogen is used.Publicationtype: Journal Article9 12 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Exploring the impact of synergistic oxygen and waste heat utilization from electrolysis in supporting a climate-neutral energy infrastructure in GermanyHydrogen is considered a key energy carrier for comprehensive defossilization of energy systems, yet large-scale deployment of electrolyzer-based production faces significant cost barriers. The utilization of electrolyzer by-products – oxygen and waste heat – offers a promising approach to reduce production costs. This study addresses whether joint oxygen and waste heat utilization generates synergistic economic benefits within a spatially optimized energy infrastructure – a question unaddressed in prior literature that examined these by-products exclusively in isolation – and provides novel insights into how market mechanisms, electrolyzer siting decisions, and conventional supply infrastructure are affected. These effects are assessed in a cost-optimal cross-sectoral German energy system at high spatial resolution. The analysis reveals that joint by-product utilization achieves near-perfect additive cost savings: 1.9% reduction in total annual system costs and 13% reduction in levelized cost of hydrogen, combining waste heat benefits (1.1% system costs, 9.6% hydrogen costs) and oxygen benefits (0.9% system costs, 4.2% hydrogen costs). These reductions are achieved through partial substitution of conventional supply infrastructure, while enabling novel economically viable production processes (e.g., oxy-fuel processes). However, oxygen utilization's substantial system-level benefits do not adequately translate into electrolyzer operator revenues, limiting private investment incentives. By-product utilization fundamentally alters electrolyzer siting through distinct spatial patterns – short-distance redistribution for waste heat and supraregional shifts for oxygen – while creating synergy hotspots where joint utilization enables novel economically viable production sites. The study demonstrates considerable potential of joint by-product utilization for reducing hydrogen production costs, but realizing this potential requires significant changes in energy supply infrastructure and coordinated cross-sectoral planning to align private decision-making with system-optimal outcomes.Publicationtype: Journal Article13 37 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Oxygen production via electrolysis: A model-based assessment of its impact on a climate-neutral German energy systemThe integration of “green” hydrogen into the energy supply represents a key strategy for the defossilization of energy systems. However, its economic viability remains constrained by the currently high production costs. A possible strategy to enhance the economic feasibility of hydrogen-based energy systems is the system-integrated utilization of oxygen, a by-product of electrolysis. This study examines the potential of integrating electrolysis-derived oxygen into various industrial applications using an energy system optimization model of Germany. The analysis focuses on identifying the cost-saving potential, the resulting impact on the hydrogen and oxygen supply chains, and suitable industrial sites for oxygen utilization. The findings reveal that integrating electrolysis-derived oxygen into industrial processes offers substantial cost-saving opportunities while influencing the optimal configuration of hydrogen supply chains and infrastructure. Incorporating electrolysis-derived oxygen into existing industrial processes can reduce total system costs by up to 0.2% without significantly changing hydrogen infrastructure design or the average levelized costs of hydrogen. Further savings are achievable by introducing new applications such as oxy-fuel combustion and wastewater treatment. In this case, system costs can decrease by up to 1.3%, and average levelized costs of hydrogen can fall by 7%. These changes also shift optimal electrolyzer siting toward industrial locations with high oxygen demand. The high-value chemical industry, in particular, can cover nearly its entire newly created oxygen demand through electrolysis. The results highlight the systemic value of integrating electrolysis-derived oxygen and underscore the importance of including oxygen utilization in early hydrogen infrastructure planning.Publicationtype: Journal Article33 35 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Optimizing temperature and pressure in PEM electrolyzers: A model-based approach to enhanced efficiency in integrated energy systemsHydrogen stands as a promising energy carrier within the ongoing energy supply transformation, yet its production via electrolyzers remains prohibitively costly. To address this challenge, this paper proposes an advanced equation-oriented process model for a PEM (Polymer-Electrolyte-Membrane) electrolysis system, including the electrolyzer and downstream hydrogen compression, aimed at optimizing the interaction of its operating parameters (i.e., current density, temperature, pressure). Initially, the model is utilized to analyze the isolated performance of the electrolysis system through operational flowsheet optimizations, followed by its integration into a broader energy system for operational planning optimization. The study reveals several key findings: optimizing operational parameters, rather than using fixed values at the maximum, improves peak system efficiency by approximately 5 %pt. and shifts this peak to lower current densities, thus expanding the range of high-efficiency operation. Each current density has an optimal pair of temperature and pressure, with maximum temperatures only advantageous at loads above 40%, while maximum operating pressure is suboptimal across the entire load range. The analysis indicates that incorporating operating parameter optimization within the operational planning of the electrolysis system reduces energy consumption by 4% and operating costs by 7% in the evaluated energy system. Additionally, the study distinguishes between optimizing the electrolyzer's operating parameters for maximizing its own efficiency and for system efficiency (i.e., including hydrogen compression). It demonstrates that maximum system efficiency is achievable only when the electrolyzer considers hydrogen compression in its operation mode, accepting some efficiency losses individually but yielding greater efficiency gains in the context of hydrogen compression. In summary, the findings of this paper suggest that continuously operating a PEM electrolyzer at maximum temperature and pressure may not be the most efficient approach. Instead, dynamic adjustments based on current density improve operational efficiency, thereby reducing electricity consumption and operating costs. Evaluating the electrolyzer within the broader energy system context – and accepting minor efficiency losses at the electrolyzer level – can yield significant overall benefits and savings. These results underscore the importance of comprehensive, context-aware strategies in advancing cost-effective green hydrogen production.Publicationtype: Journal Article49 104 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Novel concepts for metal hydride storage tanks – numerical modeling, simulation and evaluation(Elsevier, 2025-01-31); ; ; ; The efficient, space-saving and safe storage of hydrogen is a major challenge that needs to be overcome for enabling renewable energy systems. Metal hydrides are a possible solution. But the key challenge is the identification and development of the most promising metal hydride material as well as the ideal tank design for an efficient hydrogen absorption / desorption in terms of energy demand / storage losses and loading / unloading time. Against this background this paper aims to identify suitable combinations of medium and low-temperature metal hydride materials in combination with three different tank design concepts. The goal is to determine which material fits best for each combination and could thus be a suitable solution for a future implementation in stationary and mobile applications of metal hydride storage tanks. To achieve this goal a finite element method (FEM) modeling and simulation of materials and construction designs in COMSOL Multiphysics is realized. The results are analyzed in terms of hydrogen absorption rate, temperature profile over time, and the necessary energy demand for the overall storage process. The results show that for the low-temperature metal hydride investigated here, the tank design is of subordinate importance, allowing for more application-specific design. For medium-temperature metal hydrides, the investigated construction concepts show heterogeneous results. For fast hydrogen absorption and minimal external heating time, the suggested rectangular tank design might be a promising option, requiring only 28% / 29% of the heating energy of the cylindrical concepts. If the goal is to achieve the most complete hydrogen absorption, the base design concept investigated here, consisting of a cylindrical tank with metal hydride material rolled up in a spiral, is the most favorable solution; achieving a hydrogen loading of about 3.6 wt–% for the medium-temperature metal hydride. The low-temperature metal hydride achieves a total hydrogen absorption of around 1.4 wt-% in the optimum concept. For concepts with higher operating temperatures, preheating the storage tank before feeding in the hydrogen could improve the absorption process (only examined here).Publicationtype: Journal Article41 42 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Synthetic natural gas as a green hydrogen carrier : technical, economic and environmental assessment of several supply chain conceptsBased on synthetic natural gas, existing natural gas markets and infrastructures can be used to make renewable sources of energy from sun- and/or wind-rich regions available on a global scale. To overcome the challenge of providing non-fossil CO2 for the production of this synthetic natural gas, a novel concept analyzed in this paper envisages to reform the synthetic natural gas in the importing country and transporting the captured CO2 back to the exporting country to be reused for the production of synthetic natural gas; i.e., the synthetic natural gas serves as a hydrogen carrier. This paper examines and compares the energy efficiency, cost and greenhouse gas emissions of different hydrogen supply chains using synthetic natural gas as a carrier related to the year 2030. To do so, all relevant components are taken into account to model the entire supply chains. A special focus is put on different options for providing the required CO2 and on different technologies for synthetic natural gas reforming. The assessment shows that the availability of a cheap source of biogenic CO2 at the point-of-export as well as electrified steam methane reforming result in the lowest hydrogen supply cost of 6.6 to 7.0 €2020/kgH2, also achieving best results in terms of energy efficiency (around 44%). With regard to minimizing greenhouse gas emissions, autothermal reforming of methane appears to be advantageous. A closed CO2 cycle is favorable over sole onsite CO2 provision, if no cheap CO2 of non-fossil origin is available at the point-of-export and the costly direct air capture process would have to be used.Publicationtype: Journal Article48 118 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Aboveground hydrogen storage : assessment of the potential market relevance in a carbon-neutral european energy system(Elsevier, 2024-04-15); ; ; ; Hydrogen storage is expected to play a crucial role in the comprehensive defossilization of energy systems. In this context, the focus is typically on underground hydrogen storage (e.g., in salt caverns). However, aboveground storage, which is independent of geological conditions and might offer other technical advantages, could provide systemic benefits and, thereby, gain shares in the hydrogen storage market. Against this background, this paper examines the market relevance of aboveground compared to underground hydrogen storage. Using the open-source energy system model and optimization framework of Europe, PyPSA-Eur, the influence of geological independence, storage cost relations, and technical storage characteristics (i.e., efficiencies) on mentioned market relevance of aboveground hydrogen storage are investigated. Further, the expectable market relevance based on current cost projections for the future is assessed. The studies show that in terms of hydrogen capacities, aboveground hydrogen storage plays a considerably smaller role compared to underground hydrogen storage. Even when assuming comparatively low aboveground storage cost, it will not exceed 1.7% (1.9 TWhH2,LHV) of total hydrogen storage capacities in a cost-optimal European energy system. Regarding the amounts of annually stored hydrogen, aboveground storage could play a larger role, reaching a maximum share of 32.5% (168 TWhH2,LHV a-1) of total stored hydrogen throughout Europe. However, these shares are only achievable for low cost storage in particularly suited energy system supply configurations. For higher aboveground storage costs or lower efficiencies, shares drop below 10% sharply. The analysis identifies some especially influential factors for achieving higher market relevance. Besides storage costs, the demand-orientation of a particular aboveground storage system (e.g., hydrogen storage at demand pressure levels) plays an essential role in market relevance. Further, overall efficiency can be a beneficial factor. Still, current projections of future techno-economic characteristics show that aboveground hydrogen storage is too expensive or too inefficient compared to underground storage. Therefore, to achieve notable market relevance, rather drastic cost reductions beyond current expectations would be needed for all assessed aboveground hydrogen storage technologies.Publicationtype: Journal Article37 185 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Power and biogas to methanol – a techno-economic analysis of carbon-maximized green methanol production via two reforming approachesThe limited potential of sustainably available biomass requires efficient conversion to defossilize future demands of carbon-based chemicals and energy carriers. Therefore, integrating electricity-derived hydrogen into biomass-based production concepts appears promising, maximizing carbon utilization while minimizing biomass requirement. However, specific process concepts and analyses are still lacking to quantify the potential technical and economic benefits of such hybrid production processes. Thus, this research paper investigates this novel approach for decentralized methanol production from biogas within a techno-economic analysis, considering two production configurations. One configuration (BiRef) utilizes electrically heated bi-reforming for syngas generation, while the other configuration (TriRef) uses autothermal tri-reforming. Based on stationary process simulations, in-depth knowledge about process behavior is gained, efficiencies and costs are determined, and influencing factors are assessed. Within the reference case, the BiRef configuration achieves a carbon efficiency of 93 %, while the TriRef configuration reaches 97 % due to its enhanced methane conversion. Energy efficiency is 5 %pt. higher within the BiRef configuration (74 %), primarily due to the lower hydrogen demand. Carbon and energy efficiency are crucially affected by reforming temperature and inert gas fraction in the syngas. The economic analysis shows methanol production costs of ca. 1,300 €2022/t for both configurations. Variations in economic parameters emphasize advantages for the TriRef configuration when low hydrogen costs (<6 €2022/kg) are achievable. The comparison with purely biogas-based methanol production shows that hydrogen addition increases production capacity by up to 67 %. Cost advantages result against purely electricity-based production, while cost parity is achieved with purely biogas-based production. This paper demonstrates the potential of hybrid methanol production for efficient biogas utilization and highlights decisive parameters influencing technical and economic efficiency.Publicationtype: Journal ArticleScopus© Citations 2 70 95 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Cost minimized hydrogen from solar and wind : production and supply in the European catchment area(Elsevier, 2022-08-01); ; ; ; Green hydrogen plays a major role in the net-zero greenhouse gas-reduction strategy of the European Union. To supply hydrogen as cheap as possible, a well-balanced production system is needed to handle fluctuations of solar radiation and wind energy. Thus, this paper investigates the onsite hydrogen supply costs in the European catchment area in 2020, 2030, 2040 and 2050. Furthermore, a subsequent transport per pipeline to one of the projected demand centres in Europe (exemplary Germany) is considered. Also, the sensitivity regarding the additional use of salt caverns as hydrogen storage and less restricting supply profiles is assessed as well as the technical annual supply potential for 2030 and 2050. To do so, the optimal system design for minimized hydrogen supply cost for water electrolysis based on photovoltaic and wind turbines is estimated for a 0.5° x 0.5° grid using a linear optimization model. For the best locations, coastal regions at the North Sea, Western Sahara and parts of Algeria, onsite hydrogen supply cost decreases from 3 €2020/kgH2 in 2030 to 2 €2020/kgH2 in 2050. The technical hydrogen supply potential is tremendous, especially from Northern Africa, and a supply to Central Europe (Germany) via pipeline for around 3 €2020/kgH2 is possible in 2050, while a domestic hydrogen production in Germany covering the projected demand would lead to cost up to 4.5 €2020/kgH2. Furthermore, a large scale hydrogen storage e.g. in salt caverns, can reduce the hydrogen supply costs for regions with high seasonality of solar and wind up to 50% and excess electricity to less than 10%, leading to fewer cost deviations between the sub-regions, resulting in lower import costs from Northern and Western Europe than from Northern Africa or Middle East.Publicationtype: Journal Article83