TY - JOUR A1 - Reimann, Ansgar A1 - Kohlenbach, Paul A1 - Röntzsch, Lars A1 - Schneider, Clemens T1 - Development and validation of a quasi-2D electrolysis stack model with a focus on dynamic thermal behavior JF - International Journal of Hydrogen Energy N2 - - Novel dynamic PEM stack model with focus on thermal behavior is presented. - Model incorporates gas-liquid heat transfer and pressure drop phenomena. - Electrochemical and dynamic thermal behavior is validated with experimental data. - Validation shows higher gas fraction in cooling water increases heat transfer. Maintaining a constant stack temperature and minimizing temperature gradients within the stack during operation is critical to the efficiency and durability of proton exchange membrane (PEM) electrolyzers. At the same time, the significant amount of heat released during operation provides opportunities to reuse this heat, potentially improving economic efficiency and contributing to the decarbonization of the heating sector. The design of stack temperature and heat recovery control systems requires accurate and effective models that describe the dynamic thermal behavior of the stack during load changes without being overly computationally intensive. Therefore, this paper presents a dynamic quasi-2D model of a PEM electrolysis stack that rapidly calculates these dynamic processes in a generally applicable manner. The model also incorporates phenomena such as gas and liquid crossover and pressure drop. We validated the performance of the model with experimental data from a PEM electrolysis test bench and demonstrated its accuracy in describing the electrochemical and dynamic thermal behavior. The stack voltage was simulated with a mean absolute deviation (MAD) of 0.0895 V and the anode outlet temperature with an MAD of 0.127 K, while the simulated time constants of the thermal step responses showed an MAD of 4.06 %. Y1 - 2025 U6 - https://doi.org/10.1016/j.ijhydene.2025.03.225 SN - 0360-3199 VL - 118 SP - 457 EP - 471 PB - Elsevier BV ER - TY - GEN A1 - Danila, Kevin A1 - Kunz, Philip A1 - Röntzsch, Lars T1 - Dynamic operation of low-temperature electrolyzer systems in modular large-scale chemical plants T2 - Chemie - Ingenieur - Technik : CIT N2 - As one of the main contributors to the greenhouse gas emissions worldwide, the reduction of emissions in chemical industry is indispensable. The production of hydrogen from renewable energy sources using water electrolysis can contribute to this goal. However, the dynamic character of renewable energy sources leads to major challenges regarding the dynamic operation of the production process. Here, a model of a modular low-temperature electrolyzer plant is presented. The effect of available time resolution of the source electricity as well as the impact of the integration time step is studied. With the presented model the positive effect of load-dependent operation of modular electrolyzer plants with fluctuating availability of source electricity on the total hydrogen output is demonstrated. KW - Dynamic simulation KW - Electrolyzer systems KW - Modularization KW - Renewable energy KW - Water electrolysis Y1 - 2025 U6 - https://doi.org/10.1002/cite.202400140 SN - 0009-286X VL - 2025 SP - 1 EP - 11 PB - Wiley-VCH GmbH ER - TY - GEN A1 - Sharma, Prerana A1 - Röntzsch, Lars A1 - Shahi, Vinod K. T1 - Advancements towards optimization of metal–organic framework-based polymer electrolyte membranes for aqueous redox flow batteries T2 - Journal of materials chemistry : A, materials for energy and sustainability N2 - Aqueous redox flow batteries (ARFBs) are considered a potential technology for large-scale energy storage owing to their eco-friendliness, high current density, and tuneable capacity. Polymer electrolyte membranes (PEMs) are vital components of ARFB, but they suffer from significant capacity/efficiency deterioration due to a lack of advancement in structural framing. To enhance the effectiveness of ARFBs, various membrane types have been optimized. However, the development of an efficient PEM remains a significant problem. Metal–organic frameworks (MOFs) made up of metal sites and organic linkers have gained significant scientific interest. As a result of their large surface area, adjustable pore diameters, and customized functionality, MOF-based PEMs are regarded as effective separators for ARFB. This review covers the state of the art MOF-based PEMs as ARFB separators. In recent years, significant efforts have been made to utilize the unique characteristics of MOFs as they not only improve the conductivity (attributed to their 3D channel structure) and gradient distribution in the polymer framework but also stabilize and mitigate active species cross-over by regulating the effective pore size. The aforementioned tactics can stimulate more research on energy storage technologies and provide future insight into the development and design of size-sieving separators for ARFB. Y1 - 2025 U6 - https://doi.org/10.1039/D4TA08720H SN - 2050-7488 VL - 13 IS - 17 SP - 11952 EP - 11988 PB - Royal Society of Chemistry (RSC) CY - London ER - TY - GEN A1 - Jana, Sayantan A1 - Chauhan, Nikhil A1 - Muthukumar, Palanisamy A1 - Röntzsch, Lars T1 - Transient analysis and performance prediction of a metal hydride based thermal energy storage system with Integrated cooling and heat upgradation T2 - Heat transfer engineering : an international journal N2 - This work embodies a numerical model development and simulation of a metal hydride-based thermal energy storage system with integrated cooling as well heat upgradation. The concept of this system is unique as it operates on thermal drive during the energy storage cycle while during the energy release cycle it is compressor-operated. The utility of the mechanical compressor in the system is two-fold i.e., one operation mode would harness cooling, and another operation mode would fetch heat upgradation. The numerical model devised is a lumped parameter model which solves for hydrogen concentration and temperature of the linked metal hydride reactors. The proposed thermal energy storage system is of 5 MJ capacity which engages tube bundle reactor settings for both high-temperature and low-temperature hydride alloys. Each energy storage and release cycles are simulated for a fixed duration of 10000 s. For a fixed heat supply and heat recovery temperatures of 623 K and 573 K, the system offered cooling coefficient of performance in the range of 1.43–1.58 at 283–293 K. Also, approximately 77% of the energy stored at 623 K could be retrieved at 573 K. In heat upgradation operation mode, 10–30 K temperature lift was accomplished. KW - Metal Hydride KW - Thermal Energy Storage System KW - Simulation Y1 - 2025 U6 - https://doi.org/10.1080/01457632.2025.2521599 SN - 0145-7632 SP - 1 EP - 13 PB - Taylor & Francis CY - London ER - TY - GEN A1 - Sakkas, Nikolaos P. A1 - Gillung, Frank A1 - Thummar, Krunalkumar A1 - Abang, Roger A1 - Röntzsch, Lars T1 - Advanced pressurized alkaline water electrolysis at high temperatures up to 130 °C T2 - International journal of hydrogen energy N2 - Operating alkaline water electrolysers above 100 °C improves electrolyte conductivity and reaction kinetics significantly. To examine alkaline water electrolysis in this area in more detail a high-temperature pressurized test rig is designed and constructed. Nickel (Ni) foam electrodes coated with Raney nickel (Raney Ni) or nickel manganese (NiMn) and expanded Ni mesh electrodes coated with nickel(II) oxide (NiO) are utilized and the effect of electrolyte flow rate, electrode structure, pressure and temperature variation on the cell performance at temperatures up to 130 °C and pressures up to 16 bar are investigated. At the maximum current density of 1.67 A/cm2, 110 °C and 16 bar the electrode combination of Raney Ni coated Ni foam as cathode and NiO coated expanded Ni mesh electrode as anode attain the best outcome with a cell voltage of 2.29 V. In a 70 h duration test three-dimensional (3D) Ni foam electrodes with Raney Ni cathode and NiMn anode catalyst show a moderate cell degradation of 9.26 μV/h. KW - Hydrogen production KW - Alkaline water electrolysis KW - 3D electrodes KW - High temperature operation KW - Pressurized operation Y1 - 2025 U6 - https://doi.org/10.1016/j.ijhydene.2025.150075 SN - 0360-3199 VL - 149 SP - 1 EP - 12 PB - Elsevier BV CY - Amsterdam ER - TY - GEN A1 - Sampangi, Shiva Kumar A1 - Jarubula, Charath Krishna A1 - Elasmar, Mohamed A1 - Röntzsch, Lars T1 - Advanced anion exchange membrane electrolyser with 360 cm² active cell area T2 - EFCF 2025 : Fuel Cells, Electrolysers & H2 Processing N2 - Anion Exchange Membrane Water Electrolysis (AEMWE) has emerged as a promising technology for generating green hydrogen, particularly using intermittent renewable energy sources. AEMWE offers a compelling opportunity for cost-effective and sustainable hydrogen production by combining the advantages of traditional alkaline water electrolysis, such as the use of abundant and low-cost catalysts, with the benefits of Proton Exchange Membrane (PEM) electrolysis, which includes membrane separation with pure or low-concentration alkaline water and operation at high current densities. However, the widespread commercialization of AEMWE remains in its early stages, with small-scale active cell areas (less than 300 cm²) and ongoing challenges related to performance and durability. Consequently, it is vital to develop high-performance, durable AEMWE cells with larger active areas to facilitate the broader adoption of this technology. This contribution presents our recent progress in AEMWE, focusing on the development of cells with an active area of up to 360 cm². In particular, we are advancing AEMWE technology to Technology Readiness Level (TRL) 5/6, incorporating precious metal-free catalysts and advanced membranes to enhance the flexibility and efficiency of hydrogen production. As part of this effort, we have designed and experimentally tested a 100 cm² AEMWE cell and conceptualized and designed a 4-kW short-stack with a total active cell area of 1800 cm², as shown in Figure. 1, for high-pressure operation at 30 bar. Our ongoing efforts includes the laboratory testing of this newly designed stack at high pressure operation and evaluating its electrochemical performance and durability up to 1,000 h continuous operation using precious metal-free electrocatalysts. Y1 - 2025 U6 - https://doi.org/10.5281/zenodo.17244119 SP - 1 EP - 6 PB - European Fuel Cell Forum AG CY - Luzern ER - TY - CHAP A1 - Sampangi, Shiva Kumar A1 - Röntzsch, Lars ED - Reedijk, Jan T1 - Electrolysis – Proton-exchange membrane electrolyzer | Proton exchange membrane water electrolysis: State-of-the-art technique and systems T2 - Reference Module in Chemistry, Molecular Sciences and Chemical Engineering Y1 - 2024 SN - 978-0-12-409547-2 U6 - https://doi.org/10.1016/B978-0-323-96022-9.00237-1 PB - Elsevier ER - TY - GEN A1 - Reimann, Ansgar A1 - Kohlenbach, Paul A1 - Röntzsch, Lars T1 - Development of a novel quasi-2D PEM Electrolyzer Model in Modelica T2 - Proceedings of the 15th International Modelica Conference 2023, Aachen, October 9-11 N2 - To increase the efficiency of PEM electrolysis, simulation models are required that accurately describe the system's electrochemical and thermal behavior in a computationally efficient manner and are thus suitable for developing control strategies. Therefore, a pseudo-2D PEM electrolyzer model is presented in this paper, which is a compromise between the previously developed models regarding their model complexity. The electrochemical behavior is described with equations commonly used in the literature and the thermal behavior with correlations for gas-liquid heat transfer. Preliminary validation indicates that the model can describe the electrochemical behavior and thermal dynamics of a PEM electrolysis stack with good accuracy. Y1 - 2023 U6 - https://doi.org/10.3384/ecp20463 SN - 1650-3686 PB - Linköping University Electronic Press ER - TY - GEN A1 - Thummar, Krunalkumar A1 - Abang, Roger Atini A1 - Menzel, Katharina A1 - Groot, Matheus Theodorus de T1 - Coupling a Chlor-Alkali Membrane Electrolyzer Cell to a Wind Energy Source: Dynamic Modeling and Simulations T2 - Energies N2 - Renewable energy sources are becoming a greater component of the electrical mix, while being significantly more volatile than conventional energy sources. As a result, net stability and availability pose significant challenges. Energy-intensive processes, such as chlor-alkali electrolysis, can potentially adjust their consumption to the available power, which is known as demand side management or demand response. In this study, a dynamic model of a chlor-alkali membrane cell is developed to assess the flexible potential of the membrane cell. Several improvements to previously published models were made, making the model more representative of state-of-the-art CA plants. By coupling the model with a wind power profile, the current and potential level over the course of a day was simulated. The simulation results show that the required ramp rates are within the regular operating possibilities of the plant for most of the time and that the electrolyte concentrations in the cell can be kept at the right level by varying inlet flows and concentrations. This means that a CA plant can indeed be flexibly operated in the future energy system. Y1 - 2022 U6 - https://doi.org/10.3390/en15020606 SN - 1996-1073 VL - 15 IS - 2 SP - 1 EP - 26 ER - TY - GEN A1 - Sakkas, Nikolaos Panagiotis A1 - Abang, Roger Atini T1 - Thermal load prediction of communal district heating systems by applying data-driven machine learning methods T2 - Energy Reports N2 - Load forecasting is an essential part of the operational management of combined heat and electrical power units, since a reliable hour- and day-ahead estimation of their thermal and electrical load can significantly improve their technical and economic performance, as well as their reliability. Among different types of prediction techniques, data-driven machine learning methods appear to be more suitable for load estimation in operational systems, compared to the classical forward approach. Research so far has been concentrated mainly on the magnitude of buildings with single load types. It has only been extended to a limited degree on the level of a district heating network where several end users with different characteristics merge into one bigger scale heat consumer (city or group of communities). In this study, artificial neural networks are utilized, to develop a load prediction model for district heating networks. A segmented analytical multi-phase approach is employed, to gradually optimize the predictor by varying the characteristics of the input variables and the structure of the neural network. The comparison against the load prediction time series generated by a local communal energy supplier using a commercial software reveals that, although the latter is enhanced by manual human corrections, the optimized fully automatic predictors developed in the present study generate a more reliable load forecast. Y1 - 2022 UR - https://www.sciencedirect.com/science/article/pii/S2352484721015213 U6 - https://doi.org/10.1016/j.egyr.2021.12.082 SN - 2352-4847 VL - 8 SP - 1883 EP - 1895 ER -