@misc{DanilaVollmerKunz, author = {Danila, Kevin and Vollmer, Jan and Kunz, Philip}, title = {Performance evaluation of reanalysis models for upsampling of solar irradiance and wind speed data}, series = {Renewable energy}, volume = {261}, journal = {Renewable energy}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0960-1481}, doi = {10.1016/j.renene.2026.125301}, pages = {1 -- 13}, abstract = {The transition to renewable energy sources is a cornerstone of modern energy system transformation. Yet, the integration of solar and wind power remains challenging due to limited availability of high-resolution time series data. Accurate modeling and forecasting of renewable energy generation are essential for grid stability, and the effective deployment of technologies such as water electrolysis. However, most available datasets are provided at coarse temporal resolutions, which restricts their utility for dynamic system analysis and hinders the development of robust operational strategies. This study addresses this critical gap by evaluating the performance of reanalysis models and introducing a statistical upsampling approach that generates data with 1-min resolution from reanalysis data with 1-h resolution using a first-order Markov chain Monte Carlo method. The method is validated against measured data. The normalized root-mean-square error of the simulated data is less than 10\% and the mean intra-hour standard deviation differs from 4.8\% to 9.1\% compared to measured values for solar irradiance and wind speed. The generated data facilitates the optimization of system operation, and enhances the planning of sector-coupled infrastructures. Ultimately, this approach enables reliable integration of renewable energy despite limited data availability and thus contributes to the advancement of the sustainable energy transition.}, language = {en} } @misc{DanilaKunzRoentzsch, author = {Danila, Kevin and Kunz, Philip and R{\"o}ntzsch, Lars}, title = {Dynamic operation of low-temperature electrolyzer systems in modular large-scale chemical plants}, series = {Chemie - Ingenieur - Technik : CIT}, volume = {2025}, journal = {Chemie - Ingenieur - Technik : CIT}, publisher = {Wiley-VCH GmbH}, issn = {0009-286X}, doi = {10.1002/cite.202400140}, pages = {1 -- 11}, abstract = {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.}, language = {en} } @misc{SharmaRoentzschShahi, author = {Sharma, Prerana and R{\"o}ntzsch, Lars and Shahi, Vinod K.}, title = {Advancements towards optimization of metal-organic framework-based polymer electrolyte membranes for aqueous redox flow batteries}, series = {Journal of materials chemistry : A, materials for energy and sustainability}, volume = {13}, journal = {Journal of materials chemistry : A, materials for energy and sustainability}, number = {17}, publisher = {Royal Society of Chemistry (RSC)}, address = {London}, issn = {2050-7488}, doi = {10.1039/D4TA08720H}, pages = {11952 -- 11988}, abstract = {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.}, language = {en} } @misc{JanaChauhanMuthukumaretal., author = {Jana, Sayantan and Chauhan, Nikhil and Muthukumar, Palanisamy and R{\"o}ntzsch, Lars}, title = {Transient analysis and performance prediction of a metal hydride based thermal energy storage system with Integrated cooling and heat upgradation}, series = {Heat transfer engineering : an international journal}, journal = {Heat transfer engineering : an international journal}, publisher = {Taylor \& Francis}, address = {London}, issn = {0145-7632}, doi = {10.1080/01457632.2025.2521599}, pages = {1 -- 13}, abstract = {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.}, language = {en} } @misc{SakkasGillungThummaretal., author = {Sakkas, Nikolaos P. and Gillung, Frank and Thummar, Krunalkumar and Abang, Roger and R{\"o}ntzsch, Lars}, title = {Advanced pressurized alkaline water electrolysis at high temperatures up to 130 °C}, series = {International journal of hydrogen energy}, volume = {149}, journal = {International journal of hydrogen energy}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0360-3199}, doi = {10.1016/j.ijhydene.2025.150075}, pages = {1 -- 12}, abstract = {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.}, language = {en} } @misc{ThummarAbangMenzeletal., author = {Thummar, Krunalkumar and Abang, Roger Atini and Menzel, Katharina and Groot, Matheus Theodorus de}, title = {Coupling a Chlor-Alkali Membrane Electrolyzer Cell to a Wind Energy Source: Dynamic Modeling and Simulations}, series = {Energies}, volume = {15}, journal = {Energies}, number = {2}, issn = {1996-1073}, doi = {10.3390/en15020606}, pages = {1 -- 26}, abstract = {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.}, language = {en} } @misc{SakkasAbang, author = {Sakkas, Nikolaos Panagiotis and Abang, Roger Atini}, title = {Thermal load prediction of communal district heating systems by applying data-driven machine learning methods}, series = {Energy Reports}, volume = {8}, journal = {Energy Reports}, issn = {2352-4847}, doi = {10.1016/j.egyr.2021.12.082}, pages = {1883 -- 1895}, abstract = {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.}, language = {en} } @misc{AkayBashkatovCoyetal., author = {Akay, {\"O}mer and Bashkatov, Aleksandr and Coy, Emerson and Eckert, Kerstin and Einarsrud, Kristian Etienne and Friedrich, Andreas and Kimmel, Benjamin and Loos, Stefan and Mutschke, Gerd and R{\"o}ntzsch, Lars and Symes, Mark D. and Yang, Xuegeng and Brinkert, Katharina}, title = {Electrolysis in reduced gravitational environments: current research perspectives and future applications}, series = {npj Microgravity}, volume = {8}, journal = {npj Microgravity}, issn = {2373-8065}, doi = {10.1038/s41526-022-00239-y}, abstract = {Electrochemical energy conversion technologies play a crucial role in space missions, for example, in the Environmental Control and Life Support System (ECLSS) on the International Space Station (ISS). They are also vitally important for future long-term space travel for oxygen, fuel and chemical production, where a re-supply of resources from Earth is not possible. Here, we provide an overview of currently existing electrolytic energy conversion technologies for space applications such as proton exchange membrane (PEM) and alkaline electrolyzer systems. We discuss the governing interfacial processes in these devices influenced by reduced gravitation and provide an outlook on future applications of electrolysis systems in, e.g., in-situ resource utilization (ISRU) technologies. A perspective of computational modelling to predict the impact of the reduced gravitational environment on governing electrochemical processes is also discussed and experimental suggestions to better understand efficiency-impacting processes such as gas bubble formation and detachment in reduced gravitational environments are outlined.}, language = {en} } @misc{DahashMieckOchsetal., author = {Dahash, Abdulrahman and Mieck, Sebastian and Ochs, Fabian and Krautz, Hans Joachim}, title = {A comparative study of two simulation tools for the technical feasibility in terms of modeling district heating systems: An optimization case study}, series = {Simulation Modelling Practice and Theory}, volume = {91}, journal = {Simulation Modelling Practice and Theory}, issn = {1569-190X}, doi = {10.1016/j.simpat.2018.11.008}, pages = {48 -- 68}, abstract = {District heating dynamic models arise as an alternative approach to in-situ experimental investigations. The main advantage of dynamic modeling and simulation is the possibility to avoid technical and operational risks that might occur during in-situ experimental investigations (e.g. heat demand is not met, damages in the energy systems etc.). Within this study, the authors present two models for an existing district heating system in Cottbus, Germany. One model is developed using the tool EBSILON Professional, while the other one is developed using the Simscape toolbox for physical modeling in Matlab/Simulink. The models were experimentally validated against measured data from the considered district heating system. The results show that the Simscape model has a better fit and better response than the EBSILON model. Yet, some discrepancies were found between the measured and the simulated data and, therefore, the uncertainties of the models were addressed. A comparative study between both tools is presented. The EBSILON models permit only unidirectional flow, whereas the Simscape toolbox permits reverse flow. Nevertheless, the EBSILON model outperforms the Simscape model in computation time. In addition, this study presents an approach for dynamic thermo-hydraulic modeling of district heating networks. This approach is utilized to examine the role of district heating networks as heat storage as an optimization configuration. The numerical results show less start-ups for additional heat sources. Yet, higher heat losses from the network are observed due to the installation of unburied pipelines.}, language = {en} } @misc{AbangWeissKrautz, author = {Abang, Roger Atini and Weiß, Sabine and Krautz, Hans Joachim}, title = {Impact of increased power plant cycling on the oxidation and corrosion of coal-fired superheater materials}, series = {Fuel}, volume = {2018}, journal = {Fuel}, number = {220}, issn = {0016-2361}, doi = {10.1016/j.fuel.2018.02.047}, pages = {521 -- 534}, abstract = {As power generation from variable renewable energy sources such as wind and solar power continues to increase in the future, fewer baseload power plants will be needed. As a result, high operational flexibility is becoming a vital requirement for conventional power plants to allow for the smooth integration of the variable renewable energy sources (v-RES) into the grid. To understand the impact of high operational flexibility (increased cycling) for coal-fired power plant materials, five commercial coal boiler superheater and reheater materials were investigated under isothermal and cyclic conditions for 1000 h each. The candidate alloys investigated were: T91, VM12-SHC, TP347-HFG, DMV304 HCu and DMV310 N. The results (weight change kinetics and metallographic analysis) after exposure at a metal surface temperature of 650 °C clearly showed the impact of increased flexibility on the corrosion and oxidation of the materials. Oxide growth (weight gain), metal loss, oxide spallation, and grain boundary attack were found to be more severe under cyclic conditions than under isothermal conditions.}, language = {en} }