@article{WendelKaramanakosGebhardtetal.2021, author = {Wendel, Sebastian and Karamanakos, Petros and Gebhardt, Philipp and Dietz, Armin and Kennel, Ralph}, title = {Flux Linkage-Based Direct Model Predictive Current Control for Synchronous Machines}, series = {IEEE Transactions on Power Electronics}, volume = {36}, journal = {IEEE Transactions on Power Electronics}, number = {12}, publisher = {Institute of Electrical and Electronics Engineers (IEEE)}, issn = {0885-8993}, doi = {10.1109/tpel.2021.3083657}, pages = {14237 -- 14256}, year = {2021}, abstract = {This article presents a flux linkage-based direct model predictive current control approach that achieves favorable performance both during steady-state and transient operation. The former is achieved by computing the optimal time instants at which a new switch position is applied to the converter. To this end, the future current behavior is not computed based on the machine inductances or inductance look-up tables; instead, flux linkage maps are utilized to predict the trajectory of the magnetic flux linkage, and subsequently of the current. This is advantageous for electric drives with noticeable magnetic nonlinearity in terms of saturation and/or cross-coupling effects. Hence, by using flux linkage maps in the prediction process, the evolution of the stator current can be calculated more accurately, enabling the controller to make better switching decisions. Moreover, the discussed predictive controller exhibits excellent dynamic performance owing to its direct control nature, i.e., the control and modulation tasks are performed in one computational stage rendering a dedicated modulation stage redundant. Three different drive systems based on permanent magnet synchronous motors are examined to demonstrate the effectiveness of the presented control approach.}, language = {en} } @article{DietzDiTommasoMarignettietal.2020, author = {Dietz, Armin and Di Tommaso, Antonino Oscar and Marignetti, Fabrizio and Miceli, Rosario and Nevoloso, Claudio}, title = {Enhanced Flexible Algorithm for the Optimization of Slot Filling Factors in Electrical Machines}, series = {Energies}, volume = {13}, journal = {Energies}, number = {5}, publisher = {MDPI AG}, issn = {1996-1073}, doi = {10.3390/en13051041}, pages = {21}, year = {2020}, abstract = {The continuous development in the field of industrial automation and electric mobility has led to the need for more efficient electrical machines with a high power density. The improvement of electrical machines' slot filling factors is one of the measures to satisfy these requirements. In recent years, this topic has aroused greater interest in the industrial sector, since the evolution of the winding technological manufacturing processes allows an economically sustainable realization of ordered winding arrangements, rather than random ones. Moreover, the manufacture of electrical machines' windings must be preceded by an accurate design phase in which it is possible to evaluate the maximum slot filling factor obtainable for a given wire shape and for its dimensions. For this purpose, this paper presents an algorithmic approach for the evaluation of maximum slot filling factors in electrical machines under an ideal geometric premise. In particular, this algorithm has a greater degree of flexibility with respect to the algorithm approaches found in the literature, since the study has been extended to round, rectangular and hexagonal wire sections. Furthermore, the slot filling factor calculation was carried out both for standard and non-standard slots. The algorithmic approach proposed can be considered as an additional useful tool for the fast design of electrical machine windings.}, language = {en} } @article{Hess2023, author = {Heß, Max}, title = {Wave runup and wave deflection within the freebord design at dams}, series = {WASSERWIRTSCHAFT}, volume = {113}, journal = {WASSERWIRTSCHAFT}, number = {6}, publisher = {Springer Science and Business Media LLC}, issn = {0043-0978}, doi = {10.1007/s35147-023-1827-1}, pages = {72 -- 75}, year = {2023}, abstract = {The wave overtopping in context with the freebord design at dams is generally not accepted. With the implementation of independent investigations, the prognostic capability of numerical methods regarding the wave run-up and wave deflection processes on dam embankments with and without wave deflectors was verified. Furthermore, a dimensioning concept was developed that is based on data sets obtained by means of calibrated hydrodynamic-numerical models to estimate the required size of deflection structures.}, language = {de} } @article{KuglerAumuellerKrcmaretal.2022, author = {Kugler, Felix and Aum{\"u}ller, Jessica and Krcmar, Wolfgang and Teipel, Ulrich}, title = {Construction and Demolition Residuals as Raw Materials for the Production of Novel Geopolymer Building Materials}, series = {Crystals}, volume = {12}, journal = {Crystals}, number = {5}, publisher = {MDPI AG}, issn = {2073-4352}, doi = {10.3390/cryst12050678}, year = {2022}, abstract = {The increasing number of new construction projects requiring high-quality building products, which, in turn, emit enormous amounts of CO2, runs counter to European and global climate goals. The increasing occupation of valuable landfill space is also an ecological problem. To meet these challenges without having to lower living standards, more ecological building materials should be used in the future. Geopolymers or alkali-activated materials, which, unlike conventional building materials, can be produced and used without a prior burning or calcination process, offer a comparatively low-CO2 alternative. Significant CO2 emissions can already be saved by using this technology. The aim of this work is to investigate whether geopolymers can also be produced from construction and demolition residuals generated by the construction industry in order to counteract the problem of the increasing use of landfill space and, at the same time, to further reduce greenhouse gas emissions in the production of building materials. For this purpose, various residual materials from the construction and demolition industry are investigated by means of XRF, XRD, and IR spectroscopy for their setting behavior by alkaline activation. At the same time, the characteristic values of compressive strength, flexural strength, bulk density, and thermal conductivity, which are important for building materials, are determined in order to test the possible applications of the resulting materials as building materials.}, language = {en} } @article{KuglerFehnSandneretal.2022, author = {Kugler, Felix and Fehn, Thomas and Sandner, Maximilian and Krcmar, Wolfgang and Teipel, Ulrich}, title = {Microstructural and mechanical properties of geopolymers based on brick scrap and fly ash}, series = {International Journal of Ceramic Engineering \& Science}, volume = {4}, journal = {International Journal of Ceramic Engineering \& Science}, number = {2}, publisher = {Wiley}, issn = {2578-3270}, doi = {10.1002/ces2.10120}, pages = {92 -- 101}, year = {2022}, abstract = {In the present work, the influence of increasing brick scrap additions on the setting behavior and material properties of fly ash-based geopolymers is investigated. The geopolymers produced are tested for their compressive strengths, bulk densities, and thermal conductivities, among other properties. Both the starting materials and the produced geopolymers are also investigated by infrared spectroscopy, X-ray diffraction analysis, and scanning electron microscopy to show the relationship between the solidification behavior and the resulting material properties. The investigations show that brick scrap is very suitable as a matrix material for geopolymer production. Increasing brick scrap additions lead, among other things, to a reduction in bulk density, thermal conductivity and compressive strength.}, language = {en} } @article{KuglerKarrerKrcmaretal.2022, author = {Kugler, Felix and Karrer, J{\"o}rg and Krcmar, Wolfgang and Teipel, Ulrich}, title = {Setting behavior and mechanical properties of concrete rubble fly ash geopolymers}, series = {Open Ceramics}, volume = {11}, journal = {Open Ceramics}, publisher = {Elsevier BV}, issn = {2666-5395}, doi = {10.1016/j.oceram.2022.100286}, pages = {11}, year = {2022}, abstract = {Due to concerns about the very high primary raw material consumption and CO2 emissions of the economically important construction sector, the demand for "green" binders is growing. One option that is receiving particular attention is the material class of "geopolymers", which could be used as a substitute for Portland cement. This new group of binders not only exhibits improved mechanical properties, but is also characterized by particularly low carbon dioxide emissions in the course of its production. This work focuses on the influence of concrete rubble on the setting behavior and microstructural properties of fly ash-based geopolymers. In the course of the investigations, the manufactured geopolymer samples are examined for the material parameters relevant to building materials, namely compressive strength, raw density and thermal conductivity. The setting behavior and the forming structures are investigated by infrared spectroscopy, X-ray diffraction analysis and scanning electron microscopy. The present work is intended to contribute to the development of a suitable recycling strategy for the material recycling of concrete rubble in novel substitute construction materials, the geopolymers.}, language = {en} } @article{FehnKuglerTuebkeetal.2021, author = {Fehn, Thomas and Kugler, Felix and T{\"u}bke, Beatrice and Schweppe, Rainer and Mebert, Phillip and Krcmar, Wolfgang and Teipel, Ulrich}, title = {Charakterisierung und St{\"o}rstoffanalyse von r{\"u}ckgewonnenen Stoffstr{\"o}men aus W{\"a}rmed{\"a}mmverbundsystemen}, series = {Chemie Ingenieur Technik}, volume = {93}, journal = {Chemie Ingenieur Technik}, number = {5}, publisher = {Wiley}, issn = {0009-286X}, doi = {10.1002/cite.202000215}, pages = {771 -- 780}, year = {2021}, abstract = {Aufgrund steigender energetischer Anforderungen ist der Anteil an verbauten W{\"a}rmed{\"a}mmverbundsystemen (WDVS) in den vergangenen 50 Jahren deutlich gestiegen. Trotz der Langlebigkeit dieser Systeme fallen zunehmend WDVS-Abf{\"a}lle an, deren Nutzungsphase beendet ist. Aufgrund der komplexen Bauweise sowie einer Vielzahl an unterschiedlich verbauten Materialien der vergangenen Generationen bestehen viele Unsicherheiten und Probleme bei der sortenreinen und schadstoffarmen Aufbereitung solcher Systeme. Im Rahmen der vorliegenden Arbeit wurde ein Aufbereitungsverfahren f{\"u}r WDVS entwickelt. Damit gelingt eine weitestgehende R{\"u}ckgewinnung verwertbarer Werkstofffraktionen. Diese wurden auf etwaige St{\"o}r- und Schadstoffe wie Flammschutzmittel sowie auf deren Reinheit untersucht.}, language = {de} } @article{GumpertJanssenBrabecetal.2023, author = {Gumpert, Fabian and Janßen, Annika and Brabec, Christoph J. and Egelhaaf, Hans-Joachim and Lohbreier, Jan and Distler, Andreas}, title = {Predicting layer thicknesses by numerical simulation for meniscus-guided coating of organic photovoltaics}, series = {Engineering Applications of Computational Fluid Mechanics}, volume = {17}, journal = {Engineering Applications of Computational Fluid Mechanics}, number = {1}, publisher = {Informa UK Limited}, issn = {1994-2060}, doi = {10.1080/19942060.2023.2242455}, year = {2023}, abstract = {To achieve maximum efficiency in organic photovoltaics (OPV), functional layers with uniform and exactly predefined thickness are required. An in-depth understanding of the coating process is therefore crucial for an accurate process control. In this paper, the meniscus-guided blade coating process, which is the most commonly used process for the manufacturing of organic electronics, is investigated by experimental and numerical methods. A computational fluid dynamics (CFD) model is created to simulate the coating behaviour of P3HT:O IDTBR, an industrial state-of-the-art active material system used in OPV, and its results' independence of numerical parameters is ensured. In particular, the influence of the coating velocity and the initially injected fluid volume on the resulting wet film thickness is studied. The developed CFD analysis is able to reproduce the experimental results with very high accuracy. It is found that the film thickness follows a power law dependence on the velocity (˜v 2/3) and a linear dependence on the ink volume (˜V). Accordingly, an analytical expression based on our theoretical considerations is presented, which predicts the wet film thickness as a function of the coating velocity and the ink volume only based on easily accessible ink properties. Consequently, this CFD model can effectively substitute time-consuming and expensive experiments, which currently have to be performed manually in the laboratory for a multitude of novel material systems, and thus supports highly accelerated material research. Moreover, the results of this work can be used to achieve homogeneous large-area coatings by utilising accelerated blade coating.}, language = {en} } @article{BasuGumpertLohbreieretal.2024, author = {Basu, Robin and Gumpert, Fabian and Lohbreier, Jan and Morin, Pierre-Olivier and Vohra, Varun and Liu, Yang and Zhou, Yinhua and Brabec, Christoph J. and Egelhaaf, Hans-Joachim and Distler, Andreas}, title = {Large-area organic photovoltaic modules with 14.5\% certified world record efficiency}, series = {Joule}, volume = {8}, journal = {Joule}, number = {4}, publisher = {Elsevier BV}, issn = {2542-4351}, doi = {10.1016/j.joule.2024.02.016}, pages = {970 -- 978}, year = {2024}, abstract = {Organic photovoltaics (OPVs) have experienced a significant increase in power conversion efficiency (PCE) recently, now approaching 20\% on small-cell level. Since the efficiencies on the module level are still substantially lower, focused upscaling research is necessary to reduce the gap between cells and modules. In this work, we present the upscaling of PM6:Y6-C12:PC 61 BM-based devices, processed in ambient air from non-halogenated solvents, from small-area cells to large-area modules with barely any performance loss. Supported by computational fluid dynamics simulations, an acceler- ated blade coating process that enables homogeneous coatings with <5\% thickness deviation over 200 cm 2 is developed. Additional finite element method simulations are used to optimize the module layout and minimize the inevitable losses caused by electrode resistances and inactive interconnect areas to 1.9\% and 3.5\%, respectively. Finally, a 204-cm 2 OPV module with a certified PCE of 14.5\% (15.0\% on active area) is fabricated, which constitutes the new world record.}, language = {en} } @article{GumpertJanssenBasuetal.2024, author = {Gumpert, Fabian and Janßen, Annika and Basu, Robin and Brabec, Christoph J. and Egelhaaf, Hans-Joachim and Lohbreier, Jan and Distler, Andreas}, title = {On the theoretical framework for meniscus-guided manufacturing of large-area OPV modules}, series = {Progress in Organic Coatings}, volume = {192}, journal = {Progress in Organic Coatings}, publisher = {Elsevier BV}, issn = {0300-9440}, doi = {10.1016/j.porgcoat.2024.108505}, pages = {10}, year = {2024}, abstract = {Although the formation of plasma electrolytic oxidation (PEO) coatings on aluminum alloys can significantly enhance their service life, they may still suffer from corrosion damage when exposed to harsh environments with strong corrosivity for a long time. In this work, chitosan (CS) was dissolved in four acids, i.e. hydrochloric acid (HCl), citric acid (CA), lactic acid (LA), and acetic acid (HAc), and deposited onto the PEO-coated 5052 aluminum alloy using dip coating method. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS), atomic force microscope (AFM), contact angle (CA) meter, grazing incidence X-ray diffraction (GIXRD), Fourier transform infrared spectrometer (FTIR), and electrochemical workstation system were used to explore the enhancement of the corrosion resistance of PEO-coated 5052 aluminum alloy by application of CS film prepared in different solvent acids. The results showed that the interactions between chitosan and acid ions affects the uniformity, hydrophobicity, thickness and surface roughness of the CS/PEO coating. The HAc-CS/PEO coating had the lowest surface roughness of 32.4 ± 3.9 nm, the largest contact angle of 85.7 ± 2.0◦, and the thickest CS film of 20 μm, which significantly improved corrosion resistance of PEO-coated aluminum alloy.}, language = {en} }