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 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 - Roger, Abang 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 - TY - GEN A1 - Akay, Ömer A1 - Bashkatov, Aleksandr A1 - Coy, Emerson A1 - Eckert, Kerstin A1 - Einarsrud, Kristian Etienne A1 - Friedrich, Andreas A1 - Kimmel, Benjamin A1 - Loos, Stefan A1 - Mutschke, Gerd A1 - Röntzsch, Lars A1 - Symes, Mark D. A1 - Yang, Xuegeng A1 - Brinkert, Katharina T1 - Electrolysis in reduced gravitational environments: current research perspectives and future applications T2 - npj Microgravity N2 - 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. KW - Elektrolyse KW - electrolysis Y1 - 2022 UR - https://www.nature.com/articles/s41526-022-00239-y#citeas U6 - https://doi.org/10.1038/s41526-022-00239-y SN - 2373-8065 VL - 8 ER - TY - BOOK A1 - Swat, Steffen T1 - Introduction to the simulation of power plants for EBSILON®Professional Version 15 N2 - EBSILON®Professional is a powerful modelling system developed for the simulation of thermodynamic cycles. It is suitable as a tool for plant planning, design and optimization of thermal power plants with a steam process or a gas turbine process as well as plants with renewable energies (biomass, wind energy, solar energy and geothermal energy). The introduction describes the basic principles and the working steps to create a model of the plant. Furthermore, the work with the internal programming environment EbsScript and the handling of the calculation of time series is presented. KW - power plant KW - thermodynamics KW - simulation Y1 - 2021 SN - 978-3-754142-08-0 SN - 978-3-754142-09-7 PB - Neopubli GmbH CY - Berlin ET - 1. Auflage ER - TY - GEN A1 - Dahash, Abdulrahman A1 - Mieck, Sebastian A1 - Ochs, Fabian A1 - Krautz, Hans Joachim T1 - A comparative study of two simulation tools for the technical feasibility in terms of modeling district heating systems: An optimization case study T2 - Simulation Modelling Practice and Theory N2 - 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. KW - Dynamic thermo-hydraulic modeling and simulation KW - Simscape KW - EBSILON Professional KW - District heating systems KW - Heating network as heat storage Y1 - 2019 U6 - https://doi.org/10.1016/j.simpat.2018.11.008 SN - 1569-190X VL - 91 SP - 48 EP - 68 ER - TY - GEN A1 - Mieck, Sebastian A1 - Krautz, Hans Joachim T1 - Systematic analysis and preparation of high resolution in-situ measurements for the estimation of PV module parameters T1 - Systematische Analyse und Aufbereitung von hoch-aufgelösten in-situ Messdaten für die Identifikation von Photovoltaik Modulparametern T2 - VGB PowerTech N2 - In the last two decades, a rapid expansion of photovoltaic (PV) power plants of different sizes has taken place. Along with this, the interest from science and industry is growing, exploring the strengths and weaknesses of this technology as well as further developing the efficiency in its production and operation. For planning and operating of PV power plants, valid energy yield forecasts are desirable. These forecasts are also important to draw conclusions for the monitoring of future PV technologies. The analysis, evaluation and processing of meteorological and technical measurement datasets play an essential role. In this article, high-resolution measurement data sets of a mobile, autarkic test system are analyzed firstly. The measured data are checked for plausibility and validity with the corresponding methods. After this observations and phenomena with meteorological cause are described. In a second step, a practicable procedure for the preparation of the measurement data is presented, in order to make it suitable for further calculations, e.g. identification of photovoltaic module parameters for energy yield calculations. The focus is particularly on the flexibility, adaptability and code performance of the processing procedure. Results, evaluations and outlooks on the methods used, measurement data and selected software packages are made. N2 - In den letzten zwei Dekaden ist ein rascher Zubau von Photovoltaik(PV)-Kraftwerken verschiedener Leistungsgrößen zu konstatieren. Damit einhergehend wächst das Interesse aus Wissenschaft und Wirtschaft, Stärken und Schwächen der Technologie zu ergründen sowie die Effizienz in Herstellung und Betrieb weiter zu entwickeln. Für Planung und Betrieb von PV-Kraftwerken sind z.B. valide Ertragsprognosen anzustreben, aber auch Rückschlüsse aus dem Monitoring für zukünftige PV-Technologien zu ziehen. Die Analyse, Auswertung und Verarbeitung von meteorologischen und technischen Messdatensätzen spielt dabei eine wesentliche Rolle. Im diesem Artikel werden zeitlich hoch aufgelöste Messdatensätze eines mobilen, autarken Testsystems in einem ersten Schritt analysiert. Dabei werden die Messdaten auf Plausibilität und Validität mit entsprechenden Methoden überprüft, spezielle Beobachtungen und Phänomene mit meteorologischer Ursache beschrieben. In einem zweiten Schritt wird eine praktikable Vorgehensweise für die Aufbereitung der Messdaten vorgestellt, um diese für weiterführende Berechnungen, z.B. Identifikation von Photovoltaik Modulparametern für Ertragsberechnungen, verfügbar zu machen. Im Vordergrund stehen insbesondere die Flexibilität, Adaptierbarkeit sowie Codeperformanz der Aufbereitungsprozedur. Es werden Ergebnisse, Einschätzungen und Ausblicke zu den verwendeten Methoden, Messdaten, sowie gewählter Software Pakete vorgenommen. KW - Photovoltaic KW - Data preparation Y1 - 2018 SN - 1435-3199 VL - 98 IS - 8 SP - 75 EP - 81 ER - TY - THES A1 - Ojong, Emile Tabu T1 - Characterization of the Performance of PEM Water Electrolysis Cells operating with and without Flow Channels, based on Experimentally Validated Semi-empirical Coupled-Physics Models N2 - PEM water electrolysis is a clean and efficient conversion technology for hydrogen production and energy storage, especially when coupled with renewable energy sources. In spite of its many advantages, the high component and cell manufacturing costs of the conventional PEM electrolysis cell makes the PEM water electrolysis technology commercially less competitive vis-à-vis its peers. An alternative and cost effective cell design has been proposed which has up to a 25 % costs advantage over the conventional cell. In this alternative cell design, the flow channel plate which bears the most material costs in the conventional cell design has been replaced with a 3-D Porous Transport Layer (PTL) structure. While both designs perform comparably the same at low to mid current density (0 – 2 A/cm²), it has been observed that the conventional cell by far out performs the low cost cell at high current density operations, due to increased mass transport limitation in the cell without flow channels. Since industrial and commercial hydrogen production efforts are focused towards high current density operation (> 3 A/cm²), it thus becomes obvious that, in order for the cost effective alternative cell design to establish itself over the conventional cell design, the mass transport issues at high current densities have to be well understood and described. This research work seeks to understand the source of, and to eliminate the mass transport losses in the cost effective alternative cell design in order to get it performing at least as good as the conventional cell design at current densities up to 5 A/cm². To meet this objective, 2-D non-isothermal semi-empirical fully-coupled models of both cell designs have been developed and experimentally validated. The developed validated models were then used as tools to simulate and predict the best operating conditions, design parameters and micro-structural properties of the PTL at which the mass transport issues in the design without flow channels will be at its minimum, so that both cells can exhibit comparable performance even at high current densities. The models developed in this work are based on a multi-physics approach in which thermodynamic, electrochemical, thermal and mass transport sub-models are coupled and solved numerically, to predict the cell polarization and individual overpotentials, as well as address heat and water management issues. The most unique aspect of this work however, is the development of own semi-empirical equations for predicting the mass transport overpotential imposed by the gas phase (bubbles) at high current densities. Also, for the very first time, calculated PEM water electrolysis polarization curves up to 5 A/cm² have been validated by own experimental data. The results show that, the operating temperature and pressure, inlet water flowrate and thickness of the PTL are the critical parameters for mitigating mass transport limitation at high current densities. In fact, it was found that, for the size of the cells studied (25 cm² active area each), when both cells are operating at the same temperature of 60 °C, the low cost cell design will have a comparable performance to the conventional designed cell even at 5 A/cm² current density when; the operating pressure is ≥ 5 bar, the feed water flowrate is ≥ 0.024l/min∙cm², PTL porosity is 50 %, PTL pore size is ≥ 11 µm and PTL thickness is 0.5 mm. At these operating, design and micro-structural conditions, the predicted difference between the polarizations of both cells will be only ~10 mV at 5 A/cm² operating current density. N2 - Die PEM Wasser Elektrolyse gilt als effiziente Technologie zur Herstellung von sauberem Wasserstoff zur Energiespeicherung, besonders bei Kopplung mit erneuerbaren Energien. Trotz der vielen Vorteile führen hohe Kosten für die Produktion konventioneller Komponenten und Stacks zu einer nicht konkurrenzfähigen Technologie. Ein alternatives und kostengünstiges Zelldesign wurde vorgestellt, das, verglichen mit einem konventionellen Design, einen Kostenvorteil von bis zu 25 % hervorbringt. Bei diesem alternativen Zelldesign wird die Platte mit Strömungskanälen, die den größten Kostenanteil birgt, durch eine 3-D poröse Struktur (engl. Porous transport layer, PTL) ersetzt. Während beide Designs vergleichbare Leistungsdaten im niederen und mittleren Stromdichtebereich zeigen (0 – 2 A/cm2), wurde ein signifikanter Unterschied im hohen Stromdichtebereich beobachtet. Hierbei zeigt ein Design ohne Strömungskanäle niedrigere Leistungsdaten, was durch eine gesteigerte Limitierung des Massentransportes erklärt werden kann. Da sich die industrielle und kommerzielle Wasserstoffproduktion in Richtung hoher Stromdichten (> 3 A/cm²) entwickelt, scheint das erforderliche Verständnis von Massentransporteffekten offensichtlich um das kosteneffiziente Design gegenüber des konventionellen Designs voran zu treiben. Diese Forschungsarbeit versucht den Ursprung von Massentransportlimitierung des kostengünstigen Zelldesigns zu verstehen und eliminieren, um zumindest entsprechende Leistungsdaten des konventionellen Designs bis 5 A/cm² zu erreichen. Um diese Zielvorgabe zu erreichen, wurden 2-D nicht-isotherme, semi-empirische, vollstaendig gekoppelte Modelle beider Zelldesigns entwickelt und experimentell validiert. Die entwickelten und validierten Modelle wurden als Werkzeug zur Simulation und Vorhersage der geeignetsten Betriebs- und Designparameter, sowie Eigenschaften der Mikrostrukur der PTL verwendet. Dabei sind die Verluste durch Massentransport, im Design ohne Strömungskanäle, minimal, sodass beide Designs vergleichbare Leistungsdaten bei hohen Stromdichten zeigen. Die hierin entwickelten Modelle basieren auf einem multiphysikalischen Ansatz, worin thermodynamische, elektrische und thermische Effekte sowie Massentransportuntermodelle gekoppelt und gelöst wurden, um sowohl die Zellpolarisation und individuelle Überpotentiale vorherzusagen, als auch Wärme- und Wassermanagement zu adressieren. Das Alleinstellungsmerkmal dieser Arbeit ist jedoch die Entwicklung von semi-empirischen Gleichungen, um die Überpotentiale der Massentransporthemmung, ausgehend von Gasblasen, vorhersagen zu können. Ebenso wurden zum ersten Mal berechnete PEM Wasser Elektrolyse Polarisationskurven bis zu einer Stromdichte von 5 A/cm² mit eigenen Daten validiert. Die Ergebnisse zeigen, dass Betriebstemperatur und Druck, sowie Wasserflußrate am Zelleingang und Dicke der PTL die kritischen Parameter sind, um Massentransportlimitierung bei hohen Stromdichten zu vermeiden. Es wurde sogar gezeigt, dass bei der verwendeten Zellgröße (aktive Fläche = 25 cm²) vergleichbare Leistungsdaten bei 60 °C und 5 A/cm² erreicht werden können, sofern der Betriebsdruck 5 bar übersteigt, die Flussrate des Eduktwassers größer als 0.024 l/min ist, die Porosität der PTL 50 % übersteigt, die Porendurchmesser größer als 11 µm sind und die PTL Dicke bei 0.5 mm liegt. Bei diesen Betriebsbedingungen, diesen Design- und Mikrostrukturparametern wurden Unterschiede zwischen den beiden Zelldesigns von etwa 10 mV bei 5 A/cm² vorhergesagt. KW - PEM Electrolysis KW - Porous Transport Layer KW - High Current Density KW - Mass Transport KW - Modelling KW - Experimental Validation Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:co1-opus4-46504 CY - Cottbus ; Senftenberg ER - TY - GEN A1 - Abang, Roger Atini A1 - Weiß, Sabine A1 - Krautz, Hans Joachim T1 - Impact of increased power plant cycling on the oxidation and corrosion of coal-fired superheater materials T2 - Fuel N2 - 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. KW - Power plant flexibility, Isothermal oxidation, Cyclic oxidation, High temperature corrosion, Superheaters Y1 - 2018 U6 - https://doi.org/10.1016/j.fuel.2018.02.047 SN - 0016-2361 VL - 2018 IS - 220 SP - 521 EP - 534 ER - TY - GEN A1 - Katzer, Christian A1 - Babul, Konrad A1 - Klatt, Matthias A1 - Krautz, Hans Joachim T1 - Quantitative und qualitative relationship between swirl burner operating conditions and pulverized coal flame length T2 - Fuel Processing Technology KW - Flame length KW - Flame stability KW - Swirl burner KW - Pulverized coal KW - Image processing Y1 - 2017 U6 - https://doi.org/10.1016/j.fuproc.2016.10.013 SN - 0378-3820 VL - 156 SP - 138 EP - 155 ER -