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Investigation of Overpotential Distributions in a Solid Oxide Electrolysis Cell using Experimental and Modeling Approaches
No full textThis thesis investigates the distribution of overpotentials in a solid oxide cell using both experimental and modeling methods. A 3D finite element model is employed in COMSOL Multiphysics to simulate electrochemical, thermal, and transport phenomena. Experimental validation includes \textit{I/U} curve measurements, electrochemical impedance spectroscopy, and gas composition analysis via mass spectrometry. The model shows good agreement with experiments and is able to capture variations in overpotentials along the cell. Electrolysis operation at thermoneutral voltage is studied in detail with the model to evaluate overpotentials and local heat sources and sinks. The results highlight the importance of spatially resolved modeling in understanding and optimizing solid oxide cell performance. The model enables detailed analysis of current density distribution, local overpotential behavior, and heat source contributions. Combined with experimental data, it provides a valuable tool for evaluating operating strategies and guiding design improvements in high-temperature electrolysis systems
Numerical Modeling of Degas in EV Battery Cooling Plates: A Multiphase CFD Study
No full textEfficient thermal management in electric vehicles (EVs) is critical to battery performance and safety. Liquid-cooled battery plates are commonly used, but the presence of trapped air bubbles during coolant filling can degrade heat transfer and lead to localized overheating. This study presents a numerical framework for simulating the degassing process in EV battery cooling plates using the Volume of Fluid (VOF) method in STAR-CCM+. The model is validated against experimental data with image-based bubble detection, resulting in a correlation of 75% in the number of bubbles and 99% of total remaining air in the system. A comparison of three turbulence models (URANS, LES, DES) showed consistent air entrapment predictions, with LES providing the highest resolution of turbulent structures. Additionally, velocity magnitude was identified as an effective single-phase indicator for predicting regions prone to air retention, reducing computational cost of more than 90% in early-stage design evaluation. Design modifications informed by simulation results demonstrated improved degassing performance. The proposed framework enables reliable analysis of air removal in battery cooling systems and supports the optimization of geometry without extensive physical testing
Development of a Distributed Test Architecture for Reformed Methanol HT-PEM Fuel Cell Systems: with Real-Time Integration of Simulation and HiL Modules
No full textThis thesis presents the development of a distributed test architecture for reformed methanol high-temperature proton exchange membrane fuel cell (HT-PEMFC) systems, aimed at combined heat and power (CHP) applications in microgrids. The system integrates both real-time simulation and hardware-in-the-loop (HiL) components to enable modular, scalable, and realistic testing. A key contribution is the implementation of a physical methanol steam reformer test bench, which provides dynamic gas composition data to a real-time fuel cell model. The fuel cell model, developed using a gray-box approach, simulates electrical and thermal behavior and was validated against experimental data with 8.45% average relative error. A mid-level control layer coordinates the reformer, fuel cell, and thermal modules, and interfaces with a high-level energy management system (EMS). A novel gas composition control strategy was implemented to regulate CO and methanol slip by adjusting reformer temperature. Validation tests demonstrated effective gas shaping under varying flow rates. A full-system test confirmed the architecture’s ability to manage dynamic loads, coordinate module behavior, and maintain safety. The results highlight the system’s potential for future research in degradation analysis, remote testing, supporting the broader adoption of HT-PEMFC systems in sustainable energy applications.This thesis presents the development of a distributed test architecture for reformed methanol high-temperature proton exchange membrane fuel cell (HT-PEMFC) systems, aimed at combined heat and power (CHP) applications in microgrids. The system integrates both real-time simulation and hardware-in-the-loop (HiL) components to enable modular, scalable, and realistic testing. A key contribution is the implementation of a physical methanol steam reformer test bench, which provides dynamic gas composition data to a real-time fuel cell model. The fuel cell model, developed using a gray-box approach, simulates electrical and thermal behavior and was validated against experimental data with 8.45% average relative error. A mid-level control layer coordinates the reformer, fuel cell, and thermal modules, and interfaces with a high-level energy management system (EMS). A novel gas composition control strategy was implemented to regulate CO and methanol slip by adjusting reformer temperature. Validation tests demonstrated effective gas shaping under varying flow rates. A full-system test confirmed the architecture’s ability to manage dynamic loads, coordinate module behavior, and maintain safety. The results highlight the system’s potential for future research in degradation analysis, remote testing, supporting the broader adoption of HT-PEMFC systems in sustainable energy applications
Preparing organizations for Digital Transformation: A thesis from an employee perspective
No full textBeyond Silence - Representations of Afghan Women's Voices on X After the Taliban Takeover in 2021.
No full textThe Algorithm Game: A study of how danish students perceive and navigate algorithms on short video platforms
No full textThis thesis explores how Danish high school students experience and interpret algorithms on short video platforms, as well as how they perceive and attempt to influence both the videos they are shown and their own engagement with the platforms. Guided by a phenomenological approach, this study uses ethnographic methods, including mobile ethnography and interviews, to collect empirical data from six Danish high school students. The theoretical framework was derived from Science, Technology, Society studies, in particular the concept of multistability and intentionality from postphenomenology as well as blackboxing and programs & anti-programs from Actor-Network-Theory. Grounded Theory inspired an inductive and iterative approach to processing data. The findings show that the students have varying degrees of algorithmic awareness, and their knowledge is primarily shaped by personal experience rather than formal education. They primarily use short video platforms for entertainment, relaxation and passing time, but often describe the experience as unproductive or emotionally draining, especially after prolonged sessions. The students often engage with short videos impulsively, without consciously deciding to, and occasionally lose track of time and place while scrolling. The students attempt to manage their usage through various strategies with varying success, and their ability to do so depends on factors such as self-discipline, time of day, and social environment. Students actively attempt to influence their content feeds through actions such as liking, commenting, and following. They are aware that the algorithm recommends videos based on their interactions, generally sharing similar ideas although having differing views on specific actions that the algorithm reacts to. Most students view algorithms critically, acknowledging their persuasive power and potential risk of creating echo chambers
Numerical Modelling and Performance Analysis of a Packed Bed Electric Thermal Energy Storage System Integrated with a Rankine Cycle
No full textThe transition towards renewable energysources necessitates efficient energy storage so-lutions to balance supply and demand fluctua-tions. This thesis presents a numerical model-ing and performance analysis of a packed bedthermal energy storage (PBTES) system inte-grated with a Rankine cycle. The study de-velops a one-dimensional, transient numericalmodel to simulate temperature evolution andheat transfer during charging and dischargingcycles. The model is validated against existingreference data from a PBTES facility, demon-strating its reliability in predicting system be-havior. A parametric sensitivity analysis is con-ducted exploring the effects of particle size,mass flow rate, and void fraction on temper-ature distribution and pressure loss. To evalu-ate system performance during discharge, bothsingle-pressure and Dual- Pressure (DP) Rank-ine cycles are integrated with a Heat RecoverySteam Generator, and metrics such as thermalefficiency, power output, and round-trip effi-ciency are assessed. The integration of a DPRankine cycle improves heat recovery whilemaintaining a thermal efficiency of approxi-mately 36%. In conclusion, this thesis demon-strates the viability of a packed bed thermal en-ergy storage system integrated with a Rankinecycle for flexible, grid-scale energy storag
How problem representations in "Børnene Først" affect the exercise of discretion in social work
No full textWhen the Network Makes a Difference: Social Relationships and Inequality in Cognitive Decline Among Older Adults: A Longitudinal Study of the Association Between Different Dimensions of Social Networks and Cognitive Decline Among Older Adults in Denmark
No full textLeveraging Green-Blue Infrastructure in Kalundborg's Urban Transformation
No full textKalundborg is expanding as educational and industrial hub, yet it faces challenges related to urban cohesion, social wellbeing, and student retention. This thesis aims understand the causes of these issues and investigate how Green-Blue Infrastructure (GBI) can be strategically implemented to improve spatial connections and social vibrancy, supporting the city’s evolving development opportunities. The study employs a mixed-methods approach that combines GIS analysis with citizen participation and placemaking principles to identify gaps and opportunities for GBI interventions. Findings show that small-scale GBI interventions can be strategically integrated in central Kalundborg’s existing infrastructure to improve spatial and social connections for its students, and achieving higher multifunctionality potential if developed with the surrounding urban context in mind.<br/