TY - CHAP A1 - Hinterreiter, Marion A1 - Brückl, Oliver A1 - Rauch, Johannes ED - Technische Universität München, T1 - Challenges and Approaches for Long-Term Reactive Power Forecasting in Power Systems T2 - PESS 2025 – IEEE Power and Energy Student Summit, October 08 – 10, 2025 in Munich, Germany N2 - The transition from fossil fuels to renewable energy sources is driving profound changes across all voltage levels of the electrical grid, altering active power (P) as well as reactive power (Q) behavior. This transformation involves a shift from predominantly top-down, unidirectional electricity flows to bidirectional and increasingly complex flow patterns, fundamentally altering the operation and utilization of power systems. Many countries are already reporting notable changes in their transmission grid Q. This can lead to increased costs for grid expansion and compensation equipment, as well as grid losses. To minimize these losses and ensure grid stability and efficiency, understanding and forecasting Q long-term becomes essential. This paper addresses the challenges of long-term (1-20 years) Q forecasting in general by analyzing Q behavior in grids, the main influencing grid parameters, and reviewing existing forecasting approaches. It evaluates the applicability of these approaches and highlights current research gaps and trends. By focusing on this underexplored area, the paper aims to support the development of more advanced and reliable long-term Q forecasting techniques. KW - reactive power KW - forecasting KW - long-term KW - network models Y1 - 2025 SN - 978-3-8007-6656-7 SP - 109 EP - 114 PB - VDE Verlag ER - TY - JOUR A1 - Lambert, Jerry A1 - Kraus, Hermann A1 - Doepfert, Markus A1 - He, Miaomiao A1 - Gschossmann, David A1 - Ceruti, Amedeo A1 - Nemeth, Isabell A1 - Brückl, Oliver A1 - Hamacher, Thomas A1 - Spliethoff, Hartmut T1 - Assessing the techno-economic impact of district heating on electrical distribution grid reinforcements JF - Advances in Applied Energy N2 - Enhanced sector coupling across electricity, mobility, and heating sectors leads to higher efforts for distribution grid upgrades. Based on a case study, this paper evaluates the role of district heating networks in reducing electrical distribution grid reinforcements and compares their economic viability against a building-specific heat supply using heat pumps. A detailed energy system model is used to analyze two building energy renovation scenarios: a business-as-usual scenario with a 1 % annual renovation rate and an ambitious scenario with a rate of 2 %. Using a two-step optimization, the impact of different district heating network penetration levels on the distribution grid is evaluated, followed by an ex-post analysis to incorporate a simultaneity factor into district heating networks. Overall, district heating networks can reduce distribution grid reinforcements, but the associated savings alone do not justify their construction, particularly in the ambitious renovation scenario. In the business-as-usual scenario, a district heating network can reduce reinforcement costs by up to 71 %. However, in the ambitious scenario, grid reinforcements are already reduced due to lower heat peak demand, and the maximal reinforcement cost savings only amount to 35 %. Compared economically, district heating networks are cost-competitive with building-specific heating only in the business-as-usual scenario, up to a heat supply share of 70 % and in the ambitious scenario, up to 40 %. In both scenarios, a district heating network can be a robust solution to lower macroeconomic costs for a carbon-neutral heat supply. KW - Energy system optimization KW - Distribution grid KW - Grid reinforcement KW - District heating KW - Benchmark Y1 - 2025 U6 - https://doi.org/10.1016/j.adapen.2025.100251 SN - 2666-7924 VL - 20 PB - Elsevier ER - TY - GEN A1 - Rill, Georg A1 - Eiselt, Uwe A1 - Kelichhaus, Thomas T1 - Vehicle dynamics with RecurDyn based on the TMeasy tire model T2 - 26th International Conference on Theoretical and Applied Mechanics (ICTAM), August 25-30, 2024, Daegu, Korea Y1 - 2024 UR - https://www.researchgate.net/publication/383658881_VEHICLE_DYNAMICS_WITH_RECURDYN_BASED_ON_THE_TMEASY_TIRE_MODEL ER - TY - JOUR A1 - Tremmel, Florian A1 - Nagler, Oliver A1 - Kutter, Christoph A1 - Holmer, Rainer T1 - Double-Beam Cantilever Probe for Crack Probability Analysis of Multilayer Substrates During Wafer Probing JF - IEEE Sensors Journal N2 - During wafer testing, small probes are contacting pads on the wafer surface to check the chip functionality and identify faulty dies. To prevent damaging structures underneath, a mechanical load limit needs to be defined. This is done by intentionally overstressing the pads and searching for cracks that appear. A customized test bench with a patented sensor-indenter (SI) system is currently used to perform the contact cycles and identify crack formations in real time using the generated acoustic emissions (AEs). This method is faster and more accurate compared with previous optical detection methods. This article presents an improved version of the SI system usable in a wafer prober, featuring a double-beam cantilever beam with an exchangeable indenter tip. This leads to measurement conditions closer to productive wafer testing, enabling more accurate load limit definitions. The cantilever beam contains a strain gauge Wheatstone bridge for contact force measurement and a piezoelectric sensor element for AE signal detection. Amplifier circuits are designed for both sensors, and a data acquisition (DAQ) system is developed. A prototype of the sensor cantilever combination (SCC) is shown together with simulated and experimental results. The accuracy of the force sensor ( ±0.5 → ±1.3 mN) and the signal-to-noise ratios (SNRs) of the AE signals ( 29.1 → 21 dB) show only a small decrease compared with the previous SI system. A crack probability analysis of a test specimen confirms the usability of the SCC, as AE crack signals are detected at a similar mechanical load with both sensor setups. KW - Acoustic emission (AE) testing KW - double-beam cantilever load senso KW - fracture load limit KW - operational amplifier circuit Y1 - 2024 U6 - https://doi.org/10.1109/JSEN.2024.3486355 VL - 24 IS - 24 SP - 40295 EP - 40304 PB - IEEE ER - TY - JOUR A1 - Salama, Amgad A1 - Kou, Jisheng A1 - Dawoud, Belal A1 - Simonson, Carey T1 - A modeling approach for capillary-driven flow of a wetting fluid in a rectangular open microchannel of arbitrary axisymmetric width profile BT - Application to heat pipes JF - International Journal of Thermal Sciences N2 - Microchips are intensively used in almost all nowadays electronic devices. With the continuous advancement of our technologies, they get smaller in size than ever before. They generate high-intensity heat loads that need to be transported effectively such that they may function properly. Heat pipes have proven to be very effective in transporting relatively large heat loads from miniature components. They are of seamless structure that involves a working fluid capable of evaporation and condensation at the working temperature of the electronic chips. The working fluid is derived to move from the condenser to the evaporator via multiple microgrooves using capillary forces. It is important that the condensate reaches the evaporator at a proper rate such that no dry-out or flooding occur. In this work, we are particularly interested in the case of capillary-driven flows in rectangular microchannels. A generalized model is developed that works for axe-symmetric rectangular channels of arbitrary, moderately varying width profiles. It also accounts for any contrast of viscosity between the liquid and the vapor under isothermal conditions. The model shows to reduce to the special case of imbibition in straight and uniform microchannels, for which comparisons with experimental and modeling works show an excellent match. Cases representing linearly and quadratically varying converging/diverging width profiles have been explored. It is found that the viscosity ratio has a significant influence on the rate at which the meniscus advances. The model also negates the common practice found in the literature of using the formula developed for imbibition rates in capillary tubes for rectangular microchannels by replacing the diameter of the tube with the hydraulic diameter. It is also found that the channel profile has an influential effect on the imbibition rates. For tapered microchannels, the capillary force increases along the channel length while it decreases for diverging ones. It is interestingly demonstrated that, for quadratically tapered microchannel, the speed of the meniscus increases towards the end of the microchannel compared with linearly varying microchannels. On the other hand, for diverging microchannels, the speed of the meniscus decreases due to the increase in the cross-sectional area. Computational fluid dynamics (CFD) analysis has been conducted to provide a framework for confirmation and verification for which very good match has been established, which builds confidence in the modeling approach. KW - Microfluidics KW - Miniature devices KW - Capillary-driven flows KW - Microchannels KW - Heat pipes Y1 - 2024 U6 - https://doi.org/10.1016/j.ijthermalsci.2023.108622 SN - 1290-0729 VL - 195 PB - Elsevier ER - TY - CHAP A1 - Fuhrmann, Thomas A1 - Niemetz, Michael T1 - Analysis and Improvement of Engineering Exams Toward Competence Orientation by Using an AI Chatbot T2 - Towards a Hybrid, Flexible and Socially Engaged Higher Education: Proceedings of the 26th International Conference on Interactive Collaborative Learning (ICL2023), Volume 1 N2 - ChatGPT is currently one of the most advanced general chatbots. This development leads to diverse challenges in higher education, like new forms of teaching and learning, additional exam methods, new possibilities for plagiarism, and many more topics. On the other side with the development of advanced AI tools, pure knowledge will be less and less important, and demands from industry will change toward graduates with higher competencies. Education has therefore to be changed from knowledge-centered toward competence centered. The goal of this article is to use ChatGPT for analyzing and improving the competence orientation of exams in engineering education. The authors use ChatGPT to analyze exams from different engineering subjects to evaluate the performance of this chatbot and draw conclusions about the competence orientation of the tested exams. The obtained information is used to develop ideas for increasing the competence orientation of exams. From this analysis, it is visible that ChatGPT gives good performance mainly where knowledge is tested. It has, however, much more problems with transfer questions or tasks where students need creativity or complex insights for finding new solutions. Based on this result, exams and also lectures can be optimized toward competence orientation. KW - Engineering education KW - Competence orientation KW - Exam analysis KW - AI chatbot KW - ChatGPT Y1 - 2024 SN - 9783031519789 U6 - https://doi.org/10.1007/978-3-031-51979-6_42 SN - 2367-3370 SP - 403 EP - 411 PB - Springer Nature CY - Cham ER - TY - CHAP A1 - Rieger, Anna A1 - van de Par, Steven A1 - Rabl, Hans-Peter A1 - Oetjen, Arne T1 - Schärfeurteile für tonhaltige Geräusche und die Konsequenzen für die instrumentelle psychoakustische Analyse T2 - Fortschritte der Akustik - DAGA 2024, 50. Jahrestagung für Akustik, 18.-21. März 2024 in Hannover N2 - In einer vorrangegangenen Studie wurde der Einfluss psychoakustischer Parameter auf Präferenzurteile für konsonante und dissonante Geräusche untersucht. Diese Geräusche hatten die gleiche Lautheit und basierten auf einem festen Rauschhintergrund und eingebetteten hochfrequenten Tonkomponenten. Es zeigte sich, dass die Präferenzurteile eines Probandenkollektives durch ebenfalls erhobene Subjektivurteile zu Schärfe, Tonhaltigkeit und Dissonanz mit hoher Präzision vorhergesagt werden konnten.Durch das angewandte Versuchsdesign konnte diese rein auf Subjektivbeurteilungen bestehende Vorhersage mit einer instrumentellen Vorhersage der Präferenzurteile verglichen werden. Der Vergleich ergab einen niedrigeren Korrelationskoeffizienten für die modellbasierte Vorhersage, was auch durch die sehr niedrige Korrelation (R2<0,2) der berechneten Schärfe nach DIN45692 mit den Schärfe-Subjektivurteilen zu begründen war. Eine mögliche Erklärung der unzureichenden Prognose der Schärfeurteile könnte in der Bewertungsstrategie der Proband:innen zu finden sein. Für die getesteten Geräusche mit auffälligen tonalen Komponenten könnte statt der Schärfe des Gesamtgeräuschs nur die Schärfe des tonalen Geräuschobjekts berücksichtigt worden sein. Die Schärfe-Analyse der auf ihren tonalen Anteil reduzierten Signale zeigt eine sehr gute Übereinstimmung mit den Subjektivurteilen, was die Hypothese einer Trennung von Ton- und Rauschobjekten unterstützt. Es wird diskutiert, ob und wie das Paradigma der akustischen Objekttrennung in der Modellierung psychoakustischer Empfindungsgrößen Anwendung finden kann. Y1 - 2024 UR - https://pub.dega-akustik.de/DAGA_2024/konferenz?article=479 SN - 978-3-939296-22-5 SP - 1210 EP - 1213 PB - Deutsche Gesellschaft für Akustik e.V. (DAGA) CY - Berlin ER - TY - JOUR A1 - Heberl, Michael A1 - Withelm, Christian A1 - Kaul, Anja A1 - Rank, Daniel A1 - Sterner, Michael T1 - Prospective Life Cycle Assessment of Biological Methanation in a Trickle-Bed Pilot Plant and a Potential Scale-Up JF - Energies N2 - The fluctuating nature of renewable energies results in the need for sustainable storage technologies to defossilize the energy system without other negative consequences for humans and the environment. In this study, a pilot-scale trickle-bed reactor for biological methanation and various scale-up scenarios for 2024 and 2050 were investigated using life cycle assessment. A best- and worst-case scenario for technology development until 2050 was evolved using cross-consistency analysis and a morphological field, based on which the data for the ecological models were determined. The results show that the plant scale-up has a very positive effect on the ecological consequences of methanation. In the best-case scenario, the values are a factor of 23–780 lower than those of the actual plant today. A hot-spot analysis showed that electrolysis operation has an especially large impact on total emissions. The final Monte Carlo simulation shows that the technology is likely to achieve a low global warming potential with a median of 104.0 kg CO2-eq/MWh CH4 and thus can contribute to decarbonization. KW - Ökobilanzierung KW - Power-to-Gas KW - Elektrolyse KW - Methanisierung KW - erneuerbare Energien Y1 - 2024 U6 - https://doi.org/https://doi.org/10.3390/en17092206 SN - 1996-1073 VL - 17 IS - 9 PB - MDPI AG CY - Basel ER - TY - INPR A1 - Schumm, Leon A1 - Abdel-Khalek, Hazem A1 - Brown, Tom A1 - Ueckerdt, Falko A1 - Sterner, Michael A1 - Fioriti, Davide A1 - Parzen, Max T1 - The impact of temporal hydrogen regulation on hydrogen exporters and their domestic energy transition N2 - As global demand for green hydrogen rises, potential hydrogen exporters move into the spotlight. However, the large-scale installation of on-grid hydrogen electrolysis for export can have profound impacts on domestic energy prices and energy-related emissions. Our investigation explores the interplay of hydrogen exports, domestic energy transition and temporal hydrogen regulation, employing a sector-coupled energy model in Morocco. We find substantial co-benets of domestic climate change mitigation and hydrogen exports, whereby exports can reduce domestic electricity prices while mitigation reduces hydrogen export prices. However, increasing hydrogen exports quickly in a system that is still dominated by fossil fuels can substantially raise domestic electricity prices, if green hydrogen production is not regulated. Surprisingly, temporal matching of hydrogen production lowers domestic electricity cost by up to 31% while the effect on exporters is minimal. This policy instrument can steer the welfare (re-)distribution between hydrogen exporting firms, hydrogen importers, and domestic electricity consumers and hereby increases acceptance among actors. KW - Energy Transition KW - Hydrogen regulation KW - Hydrogen export KW - Climate-neutral KW - Domestic prices KW - Hydrogen prices KW - Power-to-X Y1 - 2024 U6 - https://doi.org/10.21203/rs.3.rs-4285425/v1 N1 - Der Aufsatz wurde peer-reviewed veröffentlicht und ist ebenfalls in diesem Repositorium verzeichnet unter: https://opus4.kobv.de/opus4-oth-regensburg/8485 PB - Research Square Platform LLC ER - TY - JOUR A1 - Tremmel, Florian A1 - Nagler, Oliver A1 - Kutter, Christoph A1 - Holmer, Rainer T1 - Mechanical robustness analysis of semiconductors with a single needle probe card using acoustic emissions JF - e-Journal of Nondestructive Testing N2 - The combination of indentation testing and acoustic emission (AE) is widely used to analyze the fracture toughness of test substrates. In the manufacturing of semiconductor devices this material parameter also plays an important role. During the so-called wafer testing inside a wafer prober small probe tips are pressed onto the chip surface to check its performance. To prevent damaging the chip by that, the fracture toughness and load limit of it has to be defined in a prequalification step. This paper presents a test system that imitates the wafer testing process as close as possible and uses acoustic emission to detect appearing cracks and thereby also the load limit. The frontend of the test setup consists of a modular single needle probe card which can be placed in a wafer prober. Also, the indenter properties (tip diameter, stiffness, etc.) can be adjusted to the probe used later on during productive wafer testing to ensure realistic probing conditions. A piezoelectric sensor and a full strain gauge Wheatstone bridge are implemented close to the single indenter to measure the AEs and the applied contact force respectively. The signal-to-noise-ratios (SNRs) of both sensors are improved with an own analog amplifier module before recording them with an USB oscilloscope. A developed measurement software (LabVIEW) is used to adjust measurement parameters (trigger limit, record length, conversion factors, etc.) and automatically store and separate measurement data from different acoustic events and imprints. To evaluate the result files a second software tool (MATLAB) reads the files out and clusters the recorded events to separate crack signals from electrical and mechanical disturbances. With a prototype first test results are generated and the functionality and accuracy of the measurement concept is proven. KW - Acoustic Emission KW - Crack probability distribution KW - Fracture load limit KW - Wafer testing Y1 - 2024 U6 - https://doi.org/10.58286/30254 SN - 1435-4934 VL - 29 IS - 10 PB - NDT.net ER -