Energía y Ambiente (ITBA-KIT)

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  • Tesis de maestría
    Development of an end-effector for an industrial robot for the automates integration of threaded inserts into a hybrid additive manufactoring process
    (0022-01-28) von Deyn, Lennart
    In this thesis, a novel approach to automatically install threaded inserts into additive manufactured parts is developed and validated. Such an approach is highly relevant in the context of process automation and production of function-integrated parts. Automated production in combination with additive manufacturing has the potential for resource and energy-efficient production. This is becoming an increasingly important factor during decision making, due to climate change. Furthermore, additive manufacturing can support the development of climate-friendly solutions across all fields of application, as it enables quickly adaptable designs and flexible production methods. In addition, new design approaches to produce function-integrated components are becoming available. Integrating mechanical and electrical functional components during manufacturing makes it possible to realise an efficient and cost-effective integration procedure. The Fused Filament Fabrication (FFF) process can be used for this purpose, as it allows easy automation and expandability compared to other additive processes, plus a wide variety of materials can be processed. Initial literature research on the state of the art shows, that currently no process has been described, that combines the FFF process with a subtractive process and conductive filament. The 4K-FFF unit, the subject of this thesis, offers a unique approach to the automated production of function-integrated components. The system consists of a multi-material FFF printer with a milling and handling module. Manufacturing inaccuracies resulting from the FFF process can be compensated by the milling module. An industrial robot on the handling module is used to add functional components to the process. This setup enables the fully automated production of function-integrated components. For fastening and contacting the function-integrated components, threaded inserts are used, which have to be installed manually due to a lack of a suitable alternative. Literature research shows that there are no methods for the automated installation of threaded inserts into individual components, which are common in FFF. This shortcoming is addressed in this thesis. A new end-effector for the industrial robot is developed, which can grip, heat and install threaded inserts into a component. In addition, a quick-change system is established. Both expansions further increase the degree of automation of the 4K-FFF unit. A parameter optimisation procedure is carried out to determine the ideal operating parameters for the new end-effector. The functionality of the development and the quick-change system is validated by the production of demonstrator components.
  • Tesis de maestría
    Experimental examination of the MoNiKa-ORC-Turbine and comparison of the results with thermodynamical calculation
    (2022-04-11) Mardon Pérez, Joaquín; Schulenberg, Thomas; Hans-Achim, Wiemer
    The aim of this work is to understand the propane turbine behaviour located at MoNiKa facility in Campus North (KIT). Starting with the thermodynamic simulations, continuing with the selection of different load points to evaluate them experimentally on site and ending with the data analysis to finally reach the correction of the Stodola’s law equation and the turbine efficiency correction. The simulations were performed using GESI software developed in MATLAB® by ITES, and in addition, to perform these simulations, all the calculations of the thermodynamic properties were performed with the REFPROP software, NIST fluid properties database. The working medium of this work is either propane or a mixture between propane and nitrogen. The runs were carried out at the beginning of November 2021, where different types of assays were performed, previously analysed in GESI. First a test of different turbine load points was performed, the following day the response of the turbine was evaluated by progressively opening the turbine control valve and, the last day, another sensitivity test was performed, but this time the turbine was evaluated with the response of a progressive increase of the mass flow rate through the turbine. Stodola's equation provides a calculation method for the highly nonlinear dependence of the turbine inlet pressure with a flow for a multistage turbine with high backpressure. From its correction we find its behavior for this turbine. In turn, we sought to understand the dependence of the turbine efficiency, and an equation that solves it within certain boundary conditions. The current experiment performed during winter semester 2021/2022 and is the continuous work of previous thesis and experiments at the facility. Each test performed in MoNiKa brings the possibility to increase the know-how of the facility and optimize the performance of a Binary ORCs (supercritical organic Rankine cycle) power plant with a low temperature geothermal heat source.
  • Tesis de maestría
    Experimental investigation of the combustion properties of CO2 diluted CO-O2 mixtures with variation of initial temperature and pressure
    (2022-03-15) Torres de Ritter, Eugenio Luis; Veser, Anke; Kuznetsov, Mikhail
    With the increasing relevance of energy transition, synthetic fuels have arisen as an alternative to storage green energy. In the processing of this fuels, carbon monoxide is widely used. Understanding the behaviour of the combustion of this gas is of high importance. To date, very limited knowledge is available on how combustion of carbon monoxide behaves alone or diluted with carbon dioxide as much focus were given towards mixtures that included hydrogen and water. The focus of this work is to investigate the combustion of carbon monoxide in dry ambient and characterize the flame speed of the combustion through two different methods, the Shadowgraph Method and the Constant Volume Bomb Method. For this purpose, combustion experiments in an explosion bomb were conducted. An experimental matrix of nine different initial pressures-temperature combinations and five different mixtures of CO-O2-CO2 were tested.
  • Tesis de maestría
    Methodology for energetic and economic evaluation for the geothermal heat exploitation in an industrial facility
    (2022-02-21) Wagner, Federico José; Kuhn, Dietmar; Fraguío, Martín
    This work aims to analyse the use of low enthalpy geothermal heat in Bahía Blanca by evaluating different alternatives when using it in a specific project. In Bahía Blanca, Argentina, several boreholes with geothermal water have been used for many years. Although there are ageing wells in this area, many of which are proof of the existing considerable geothermal potential, only a few are deemed heat sources. The first section introduces general concepts for the contextualisation of the document. Then, the second section details all the performed methodology and an explanation about the selection of the industrial case is given. Then, the industrial system and pipelines are presented, followed by a description of the mass and energy balances. Later, the heat pump calculous, economic evaluation and CO2 footprint analysis procedures are presented. Finally, the fourth section presents all the obtained results in graphics and tables, and at the end, the conclusions are assessed.
  • Tesis de maestría
    Sensitivity study and improvement of a film cooling configuration of a high-pressure turbine blade
    (2022) Giménez, Juan Ignacio
    Much effort has been expended in the aerospace industry in order to achieve the highest quality standards required for nowadays technical and environmental necessities. This involves the increase of specific power and overall engine performance, together with the reduction of noise, specific fuel and heat to fuel consumption. Fundamentally, thermal efficiency and power output increase while increasing turbine rotor inlet temperatures. For this purpose, it is necessary to optimize engines with regard to the overall thermodynamic process. Advanced gas turbine engines operate at high temperatures to improve thermal efficiency and power output. As the turbine inlet temperature increases, the heat transferred to the turbine blades also increases. The level and variation in the temperature within the blade material, which causes thermal stresses, must be restricted to achieve reasonable durability goals. The operating temperatures for aircraft engines are far above the permissible metal temperatures, therefore it is necessary to cool the blades internally and externally. The blades are cooled by extracted air from the compressor of the engine and, since this extraction incurs in a reduction of thermal efficiency, it is necessary to understand and optimize the cooling techniques, operating conditions, and turbine blade geometry. Increasing demands confront the cooling systems of turbine blades. High temperature material development, such as thermal barrier coating (TBC) or highly sophisticated cooling schemes, are a necessary challenge to overcome, in order to ensure high-performance gas turbines for the upcoming years. The suggested designs hereby are to achieve an optimum cooling by a minimum use of cooling air and minimum aerodynamic losses which are an unwanted consequence of film cooling injection. Cooling techniques in advanced gas turbine engines can be distinguished between internal and external cooling. In convection cooling or internal cooling, the secondary flow extracts the heat flux through the blade walls and transports it away via channels inside the turbine blade. A vast amount of studies for different types of geometry arrangements have been carried out and applied, in order to increase heat flux transfer. These geometries include rib turbulators, pin fins, dimpled surfaces, surfaces with arrays of protrusions, swirl chambers, and rough surfaces. For external cooling, film cooling technology made possible the nowadays achievements in high efficiency gas turbine engines. The art and science of film cooling concerns the bleeding of internal cooling air through the external walls to form a protective layer between the hot gases and the component external surfaces. The application of effective film-cooling techniques provides a reliable defense for hot gas path surfaces against the high heat fluxes, serving to directly reduce the incident convective heat flux on the surface. Several investigations have been made regarding the major effects of cooling holes arrangements, turbulence, interaction between flows and vorticity production in order to improve film cooling technology. To address the main challenges of designing an optimal film cooling configuration, it is necessary to understand the behaviour of the main gas flow and the coolant flow. For this purpose, CFD calculations are carried out to visualise and understand the complex physical phenomena under study. However, numerical models should be validated with experimental data as this path leads not only to the understanding of the physical phenomena involved in the experiment, but also provides correct guidance on how the different variables under study can lead to engineering improvement. A test rig at the Institute for Thermal Turbomachinery (ITS) at the Karlsruhe Institute of Technology (KIT) is used to validate the related CFD set-up. In this work, a sensitivity study of different conventional film cooling configurations is introduced. This involves the study and modification of different geometrical variables in specific regions of the blade. Also, the complex vortex structures generated due to the interaction of the main hot gas with the coolant, that enhances heat flux transfer through the blade, is analysed. The most promising configurations in terms of blade temperature reduction, will be considered as possible candidates for blade manufacturing
  • Tesis de maestría
    Design of a MoNiKa-ORC-turbine model in Simulink and comparison with experimental results
    (2022) Filipe, Julia; Schulenberg, Thomas; Wiemer, Hans-Joachim
    This work consists in the development of a computational model for the steam turbine currently operational in MoNiKa test facility plant, located in KIT-Campus Nord, Germany. Given that this corresponds to the first attempt to model the mentioned turbine, the selected approach was to elaborate a highly simplified model that considers the system as a whole, unique element, and therefore calculates in terms of the turbine’s inlet and outlet parameters. The development was made in Simulink, using a basic configuration of blocks and features, and also some specific parts were coded in MATLAB. The building process resulted firstly in a simplified version of the model that supports constant inputs and outputs and consequently is independent of time; and a final version that supports time-dependent inputs and outputs, and can be employed to simulate transient operation conditions. The validation was made using real data provided by the plant, with a selection of several cases that reflected different operation conditions. Final results showed that the model is successful in predicting stationary operation cases, and also achieved good results with some transient operation conditions that presented progressive variations. However, the model is not suitable for simulation of fast-varying conditions.
  • Tesis de maestría
    Development of the processing step from MOF to supported catalyst by electrospinning
    (2022) Alvarez, Macarena; Maletzko, Annabelle
    In order to increase the flexibility of renewable energies and improve their integration into existing energy grids, efficient intermediate storage is necessary. High-purity hydrogen produced in a water electrolysis cell is a suitable energy carrier. However, the use of some electrolyzers is associated with high costs due to the required use of precious metals as catalysts, while others have disadvantages in terms of load modulation. In this sense anion exchange membrane water electrolysis (AEMWE) arises as an attractive alternative technology that combines convenient features of other type of electrolyzers. Nevertheless, there is a necessity in improvement regarding the performance of AEMWE. The oxygen evolution reaction (OER) in the anode, is the major source of energy loss and therefore, there is potential to optimize OER catalysts. In this work, supported catalysts for the OER were developed using Metal-Organic Frameworks (MOF74) dopped with Ni and/or Co and fibers obtained from an electrospinning process, as supporting material. The MOFs were pyrolyzed to obtain a carbon scaffold with finely dispersed transition metals, as well as the polymer fibers, which structure the catalyst, allowing to tune conductivity and mass transport. Two different routes for combining the MOFs with the fibers were studied. In order to investigate the electrospinning process, polymer concentration, solvent, applied voltage and polymer were varied. The improved parameters were selected and Polyacrylonitrile (PAN) fibers were successfully electrospun and pyrolyzed. The MOFs were characterized physically, chemically and electrochemically. Pure Ni-MOF74 showed increasing current along the Cyclic Voltammetry cycles, reaching a mass-specific current of 732 mA mg -1 after 50 cycles. A supported catalyst was obtained after impregnation of the Ni-MOF74 over the pyrolyzed fibers and characterized. The combined catalyst showed a similar behavior compared with the pure Ni-MOF74.
  • Tesis de maestría
    Machine learning-based analysis of residential electricity consumption behavior for consumers and prosumers
    (2021) Werner, Tamo; Jiao, Jiao
    With the shift towards a more sustainable energy system, the need for a better understanding of the behavior development over time of consumers and prosumers arises. Despite the growing penetration of smart meter infrastructure, the availability of energy usage behavior data is still limited, due to privacy and security concerns. Thus, connecting and comparing existing datasets is the key to observe the user behavior shifts as well as enhancing the utility of the available data. In the present work, a novel work!ow for combined analysis on multiple smart meter datasets is proposed, which links datasets with diferent scopes, temporal origins and speci#cations. In general, there are 4 steps: data preprocessing, clustering, location dependency check and dataset linking. First, the meteorological seasons combined with weekdays and weekends are picked for data segmentation in the data preprocessing, followed by missing value validation and normalization based on the maximum and minimum consumption value of each household. Thereafter, K-means clustering algorithm is applied to group the user behaviors, which stands out by 0.8186 Silhouette coe$cient (SIL) and 0.2884 Davies-Bouldin Index (DBI) among Fuzzy C-Means and hierarchical clustering approach. Subsequently, two validation approaches on the location dependency, cluster center correlation (0.8048) and location share among clusters (4.99 % variability), prove the minor impact of the household location on the electricity consumption behavior within Germany. Based on the location dependency check, ultimately, the combined analysis of the two datasets reveals the temporal development of the residential consumption behaviors. It shows that new technologies, especially Photovoltaics (PV), Electric Vehicles (EV) and heat pumps, have in!uence on the user behavior shift and the energy consumption level.
  • Tesis de maestría
    Investigations on energy optimal solutions to control a forestry crane
    (2021) Schulz, Tim; Geimer, Marcus; Geiger, Chris
    Due to the progressing climate change, climate-neutral resources are becoming increasingly important. The forest industry is aware of this problem and hence, is looking for new technologies to make the production of its natural resource more ecient. Therefore, this thesis presents an energetic optimization of a forestry crane. For this purpose, a pseudoinverse solution of the crane kinematics is optimized by the gradient projection method according to minimum hydraulic pressure and ow rate. The hydraulic pressure reveals to be the relevant optimization parameter. By increasing the feedback pressure, its inuence on high-pressure peaks is increased in order to successfully reduce these. To maximize the energy savings, a hydraulic transformer is included in this approach. By coupling the inner and outer boom, potential energy is utilized for contrary motions of these. The developed algorithm for optimizing the energy demand is implemented in a holistic simulation model of a forestry crane arm. The eectiveness of this approach is tested in the model using representative trajectories. Energy savings of up to 26.9 % compared to a least norm pseudoinverse solution can be determined using the optimized control system. When the energy-saving potential of the coupling of the inner and outer boom is also considered, the total reduction in energy increases to up to 31.8 %.
  • Tesis de maestría
    Automation and optimization of agricultural soil tillage applying machine learning based on machine- and process sensor systems
    (2021) Kazenwadel, Benjamin; Geimer, Marcus; Stein, Alexander; Becker, Simon
    Climate change and cost pressure lead to new environmental and economic challenges that increase the demand for innovative control systems to automate and optimize agricultural tasks. Automating speed control during power-intensive soil tillage can increase eciency and sustainability and counteract the lack of qualied personnel in agriculture. A survey was carried out focused on tillage by cultivating to obtain an overview of the challenges farmers face during their work, including their target preferences. Based on the obtained requirements for tillage by cultivating, a system was developed automating working depth control by online Lidar plane detection to ensure tillage quality and establish a basis for good plant growth. Automated speed control is realized based on an online-parameterized draft force and traction model combined with the usage of a neural network for fuel rate prediction. The network is trained oine and adaptable to the individual preferences of the farms and varying implements. Thereby, the operator can choose and customize optimization objectives such as fuel eciency, performance, or total cost. During the evaluation, the control system was tested with various objectives against a human driver and was able to perform optimization on the individual objective. Furthermore, the transferability of the system was demonstrated with the usage of another implement.
  • Tesis de maestría
    Optimization of the organic Rankine cycle power plant MoNiKa's control system
    (2021-02-08) Gutiérrez Guerra, Juan Francisco; Wiemer, Hans-Joachim; Nemirovsky, Nicolás
    ENG: The aim of this work was to optimize the MoNiKa organic Rankine cycle power plant control system. In particular, performance and robustness of the PID control loops were evaluated for the main and support feed pumps and throttling valve. Each component was physically modelled in Simscape, while control simulations were performed in Simulink based on process transfer functions. The tuning methods were chosen in order to achieve faster, more robust responses to setpoint and disturbances changes. Stability, sensitivity and settling time values were calculated on MATLAB based on frequency response techniques, and results were compared with a set of previously measured data. Final results showed that, using the Continuous Cycling Method, the optimized controllers’ parameters were able to provide a better setpoint tracking and disturbance rejection, while accomplishing up to 10 times faster responses than the preliminary PID controllers’ settings. SPA: El objetivo de este trabajo fue optimizar el sistema de control del ciclo orgánico Rankine de potencia MoNiKa. En particular, se evaluó el desempeño y robustez de los lazos de control PID de las bombas principal y de soporte y de la válvula de estrangulación. Los componentes fueron modelados en Simscape, mientras que las simulaciones de los sistemas de control se ejecutaron en Simulink, en base a funciones de transferencia. Los métodos de ajuste fueron seleccionados para brindar respuestas más rápidas y robustas ante cambios de setpoint y perturbaciones. Valores de estabilidad, sensibilidad y tiempo de asentamiento fueron calculados en MATLAB en base a técnicas de respuesta en frecuencia, y los resultados fueron comparados con un conjunto de mediciones previamente tomadas. Los resultados finales demostraron que, usando el Método de Ciclo Continuo, los parámetros optimizados lograron un mejor seguimiento de setpoint, mejor rechazo a perturbaciones y respuestas hasta 10 veces más rápidas que los parámetros preliminares.
  • Tesis de maestría
    Lamination for Long-term Stability of Perovskite Solar Cells
    (2021) Clement, David; Singh, Roja
    The climate change and the constantly rising demand of energy worldwide requires the development of efficient, though environment-friendly, systems to generate renewable power. The use of perovskite solar cells in photovoltaic applications has proven to be a promising approach facing this task. The main issue preventing commercialization of this new technology is the instability of the perovskite material when exposed to moisture, oxygen, and elevated temperatures. This work aims to face this concern by improving encapsulation of perovskite solar cells with a glass-to-glass encapsulation method, using butyl rubber as edge sealant and polyolefin as encapsulant. Furthermore, this encapsulation technique is applied to perovskite solar modules. High temperatures usually required for encapsulation is optimized for CsFAPbI3 and MAPbI3 based solar cells and modules, so that power conversion efficiency does not decrease after lamination. The quality of the encapsulation is tested at 85 % relative humidity and 25 °C wherein devices encapsulated at 85 °C reach 80 % of their initial efficiency after approximately 550 h. A rapid decrease in performance of encapsulated perovskite cells under constant illumination and biased is attributed to the Ag electrode. In contrast, devices with Au electrode are stable for 62 h. Further optimization of the encapsulation method by using the transparent conducting oxide layer as conductive path through the encapsulation increases device stability. This is shown by comparing different contacting methods with an electrical calcium test. Applying and testing this contacting method to the encapsulation of perovskite cells and modules is a task for future research.
  • Tesis de maestría
    Large eddy and rans simulations of V-RIB structured cooling channels of the first wall of future fusion reactors
    (2020) Winzig, Manuel; Klein, Christine
    This work contributes to the development of the future fusion reactor DEMO. It investigates the cooling of the first wall blankets by rib structured cooling channels. For this purpose, RANS simulations using the 𝑘 − 𝜔 − 𝑆𝑆𝑇 model and the Reynolds Stress Model as well as Large Eddy Simulation were carried out on a channel with V-shaped ribs on one side at a Reynolds number of 𝑅𝑒 = 1.56 ⋅ 10 As a working fluid helium was used at an operating pressure of 𝑝 = 8 𝑀𝑃𝑎. The relative roughness of the channel was 𝑒⁄𝐷ℎ = 0.0461 and the rib pitch was 𝑝⁄𝑒 = 10. The focus of the analysis of the results has been on heat transfer quantities, pressure loss and flow patterns. It was shown that the rib induced vortical structures that were associated with a large increase in heat transfer downstream of the rib but also caused a heat transfer deterioration directly behind it. The comparison between the simulations has shown that the 𝑘 − 𝜔 − 𝑆𝑆𝑇 model resolves well the magnitude of the averaged heat transfer but fails to reproduce the flow patterns and friction factor accurately when compared to the Large Eddy Simulation. On the other side, the Reynolds Stress Model showed better accuracy resolving the flow patterns and friction factor but strongly underpredicts the heat transfer for the given case. Additionally, the results of the Large Eddy simulation have been compared to previous simulation results that have been conducted on a smooth and a rib structured channel with 𝑒 = 0.9 𝑚𝑚. It was shown that reducing the rib height led to a slight decrease in heat transfer on the rib structured side but also reduced the pressure loss significantly.
  • Tesis de maestría
    Re-engineering of Pelton runner hydraulic cfd profile to systemize the Fabrication process in Software to include hydraulic tests design & manufacturing
    (2020) Stellner, Julia; Guerra, Carlos
    Uno de los objetivos del Centro de Investigación y Recuperación de Turbinas hidráulicas y Partes Industriales (CIRT) que pertenece a un holding estatal llamado CORPORACIÓN ELÉCTRICA DEL ECUADOR - CELEC EP con la unidad de negocios Hidroagoyán, es la reparación y reconstrucción de turbinas y piezas de repuesto que forman parte de una central hidroeléctrica. La meta es remediar los defectos y desgastes ocasionados durante la operación y llevar los componentes a su estado nominal o bien, mejorar el perfil hidráulico para obtener un funcionamiento adecuado con menos fallas. Los rodetes recuperados del CIRT llegan de todas partes del país que se pueden clasificar por los tipos Kaplan, Francis y Pelton. La turbina Pelton, a pesar de ser una tecnología relativamente antigua, tiene un estado de investigación y comprensión del funcionamiento comparativamente bajo. Durante años el desarrollo de la turbina Pelton continuó y se logró mejorar el funcionamiento, siendo una de las turbinas hidráulicas más eficientes hoy en día. Sin embargo, la comprensión más profunda de los mecanismos de flujo durante la interacción del chorro con el cangilón todavía no se ha logrado, ya que se trata de un flujo complejo. Por causa de las complejidades se pueden realizar simulaciones con Dinámica de Fluidos Computacionales (CFD por sus siglas en inglés) sin embargo estas presentan dificultades tecnológicas y en algunos casos imprecisiones. Es por ello que hoy en día, aún se realizan los estudios acerca de la tecnología Pelton en un banco de pruebas que produce un costo alto y un tiempo de ensayos y estudios prolongado. En muchos de los casos los rodetes llegan al CIRT sin planos dimensionales o debido a la complejidad propia de su perfil hidráulico no se puede plasmar en un documento 2D, tal caso requiere el proceso de una ingeniería inversa; para automatizar, simplificar y reducir el tiempo del proceso de diseño, un programa para la sistematización del diseño fue desarrollado, lo cual ayuda en el proceso de la ingeniería inversa, como en el rediseño de rodetes fallados. Este programa aporta a la solución de la dificultad de la simulación de los cangilones, lo cual genera perfiles hidráulicos de cangilones Pelton con características deseadas de manera automática cuya ventaja principal es la creación de modelos simples y modificables de forma rápida para su uso en pruebas de flujo en CFD, con los cuales la obtención de resultados de la idoneidad del perfil y las dimensiones del cangilón es lograda. Los diseños virtuales de los cangilones de la central Pucará – Ecuador sirven como base de diseño del programa. En la evolución del trabajo un rango de buen funcionamiento de 15 a 20% de diferencia del tamaño entre Pucará y el cangilón modelado fue establecido.
  • Tesis de maestría
    Development and programming of an engineering tool regarding the heat radiation of Hydrogen vertical jet flames
    (2020) Redosado León, Kevin Arturo; Jedicke, Olaf
    Esta tesis tiene como objetivo entender, programar y desarrollar una herramienta de ingeniería sobre la radiación de las llamas de chorros verticales de hidrógeno. El lenguaje de programación de Python 3.7 es utilizado para programar la herramienta electronica. El trabajo actual estudia las propiedades termodinámicas del hidrógeno mientras se somete a un purgado. El análisis utiliza la ecuación de estado de Abel-Noble (EOS) para modelar el hidrógeno como un gas real. Con estas propiedades, diferentes parámetros sobre la llama de hidrógeno son hallados empleando diferentes correlaciones para determinar parámetros como la fracción de calor radiado (𝐹), la longitud de la llama (𝐿𝑓) y el flujo de calor de la radiación térmica (𝑄𝑟). Los resultados calculados se comparan con los datos experimentales para determinar su validez. El algoritmo utilizado para programar la herramienta electronica se muestra en este trabajo. Además, el procedimiento para resolver problemas como el refinamiento del pasos del tiempo y la resolución espacial se dan en este trabajo.
  • Tesis de maestría
    The role of gas transmission networks in future scenarios for the European energy system
    (2020) Plett Palomar, Kilian; Brown, Thomas William
    Para lograr la desafiante y ambiciosa reducción de emisiones de dióxido de carbono (CO2) que ha acordado la Unión Europea (UE), será necesario llevar a cabo fuertes transformaciones en todo el sistema energético europeo en los próximos años. El objetivo de este trabajo es integrar y validar los últimos datos disponibles sobre la actual red europea de gas natural (capacidades transfronterizas, demanda y suministro de metano) en el sistema acoplado por sectores (sector coupling), así como analizar sus efectos en tres escenarios seleccionados con cero emisiones netas de CO2: un primer escenario totalmente nuevo sin ninguna red de gas previa, en el que se construye una nueva red de hidrógeno entre 33 países europeos; un segundo escenario donde la red de metano existente opera en paraleloa una nueva red de hidrógeno; y un tercer escenario en el que las capacidades existentes de la red de metano se pueden reconvertir para transporte de hidrógeno, si es necesario, para satisfacer las demandas del sistema. En los tres escenarios, además de la conversión de la red de gas natural, se pueden construir nuevas tuberías de hidrógeno con mayores costos de inversión. El presente trabajo está basado en el software de código abierto (open software) PyPSA-Eur-Sec, un modelo integrado a nivel continental del sistema energético europeo. Los resultados muestran que la red de metano está transportando metano a niveles hasta 10 veces inferiores a las capacidades actuales de las tuberías, dependiendo de cada capacidad transfronteriza. A pesar de esta reducción global en el transporte y consumo de metano, la red de transporte sigue siendo necesaria y sirve para transportar adicionalmente el biogás que se prevee en estos escenarios, concretamente un 47 % (352 TWh) de la demanda total de metano, 740 TWh. Las grandes cantidades de hidrógeno generado mediante electrólisis en estos futuros escenarios, son cantidades similares al mentano extraido en Noruega y otros países europeos hoy en día, con hasta 3189 TWh por año. Las soluciones optimizadas comparadas entre los escenarios, muestran poca o ninguna diferencia entre ellas. Esto se debe a que los excedentes de generación de energía renovable proveniente predominantemente de energía eólica generada predominantemente en sólo cuatro países alrededor del Mar del Norte y el Océano Atlántico. Las rutas para transportar hidrógeno no son las mismas que las actuales para metano, por lo que la reconversión de las tuberías juega un papel importante para reducir los costos. Junto a la reconversión de tuberías de metano, todavía es necesario construir nuevas tuberías de hidrógeno, ya que las renovadas por sí solas no son suficientes para transportar y cubrir las demandas energéticas en Europa. Aunque los escenarios no influyen significativamente en la configuración de las distintas tecnologías, se pueden ahorrar costos de 2 mil millones de euros por año al convertir parcialmente la red de metano existente en hidrógeno. El funcionamiento de las redes de metano e hidrógeno no presenta el mismo funcionamiento estacional que en la actualidad, sino un funcionamiento más congestionado en ambas redes de H2 y CH4; esto es causa inherente a la optimización del problema, pero muestra que la operación de las tuberías de hidrógeno reconvertidas pueden ser operadas de manera estacionaria, lo cual es un requisito del método de reconversión seleccionado en este trabajo. El propósitode este método de operación es el de extender la vida útil de las tuberías de transporte. Por otro lado, las tecnologías de los procesos power-to-gas, Sabatier y HELMETH, y SMR tienen capacidades instaladas no signi cativas en los escenarios estudiados.
  • Tesis de maestría
    Applicability of a state-of-the-art engineering toolkit in the risk analysis of a prototypical Hydrogen refueling station
    (2020) Ordóñez, Marco; Jordan, Thomas
    En el desarrollo actual de los vehículos de celdas de combustible, las estaciones de servicio de hidrógeno desempeñan un papel importante como fuente directa de combustible. Uno de los principales aspectos que deben considerarse durante la instalación y el funcionamiento de una estación de servicio de hidrógeno es la seguridad tanto de la infraestructura como del personal que trabaja en ella. Sin embargo, la falta de herramientas de cálculo ampliamente aceptadas hace que las evaluaciones de riesgos sean difíciles de reproducir de una estación a otra. En el presente trabajo se estudia el potencial de aplicabilidad y se identifican las limitaciones de un software de cálculo ingenieril de código abierto para evaluación de riesgos, denominado HyRAM, para un proceso de evaluación de riesgos de una estación de servicio de hidrógeno prototípica basada en un caso real. Para ello, este trabajo inicia con una investigación de marco teórico sobre la metodología de evaluación de riesgos, el funcionamiento de una estación de servicio de hidrógeno y los peligros más relevantes presentes en este tipo de instalaciones. Para el análisis de consecuencias y probabilidades, luego se describen los principales modelos de cálculo de HyRAM y se seleccionan los escenarios de fallo a ser simulados con estos modelos. Se detallan las principales características de la estación prototipo de abastecimiento de hidrógeno. Se analizan dos conjuntos de escenarios de fugas de hidrógeno en la conexión roscada a la salida de la zona del compresor (donde interesan la gravedad de las consecuencias y la frecuencia de ocurrencia) mediante la radiación de la llama de jet para una ignición inmediata, y la sobrepresión para una combustión retardada. Para concluir la evaluación de riesgos, los resultados se convierten en una ponderación global de riesgos. Las principales conclusiones de este trabajo muestran como más importante que HyRAM es adecuada para un número acotado de escenarios, y que necesita incluir condiciones de borde adicionales para satisfacer el análisis de un caso real prototípico. En particular para el modelo de llama de jet, se observa la falta de un perfil de radiación de la llama que evolucione en el tiempo y facilite un cálculo preciso de la dosis térmica. Para el modelo de sobrepresión, el principal aspecto identificado es la falta de fiabilidad para describir los complejos fenómenos durante la evolución inicial de la mezcla aire-hidrógeno.
  • Tesis de maestría
    Development of an empirical body force model for plasma-based flow control in CFD applications
    (2020) Günther, Maiken; Frohnapfel, Bettina; Kriegseis, Jochen
    In the present work a new empirical model for the phase-resolved body forces of an DBD (Dielectric-Barrier-Discharge)-plasma actuator is developed. Therefore planar body forces have been derived from existing PIV (Particle-Image Velocimetry) measurements. A new approach is introduced that makes use of the similarity of fluid dynamic and electrostatic potential theory. The body forces are derived with the gradient of a scalar potential field that consists of superimposed single body force potentials. A system of linear equations describes the relation between the gradient field, the magnitude of the single potentials and the resulting body forces. A least-square fit of this equation system to the experimental body forces approximates the local magnitude of the potentials. The modeling results are compared to the experimental data regarding their phase-averaged and phase-resolved integral body force, the spatial body force distribution and the physical plausibility of the potential magnitudes. Centering around a baseline state, different numeric configurations of the model and their results are presented and discussed. This baseline state strongly indicates the validity of the developed approach, particularly regarding the resulting values of phase-resolved integral body forces. A future improvement of the numeric setup of the model is expected to prove the similarity of the distribution of body force potentials and free charges in the discharge area. This could lead towards a model that is independent from experimental validations. Finally, the new model is drawn into comparison with former modeling approaches by Shyy et al. [28], Suzen et al. [31] and Maden et al. [23]. Here it asserts itself with its unique capability to represent both components of phase-resolved body forces with good accuracy.
  • Tesis de maestría
    Analysis and evaluation of Monika’s first result in bypass configuration
    (2020) Gardella, Luciano Javier; Schulenberg, Thomas
    El objetivo de esta tesis es mostrar, discutir y evaluar los resultados de la Central Eléctrica MoNiKa en régimen estacionario trabajando con diferentes partes de carga en operación de bypass. Los experimentos realizados para esta tesis durante el semestre de invierno de 2019, son los primeros resultados que salen de la instalación. MoNiKa fue autorizada para operar a finales de 2018, y hoy en día sigue en desarrollo. El trabajo actual, estudiará la planta de energía para definir su situación real. Las principales cuestiones a responder fueron la cuestión de la fiabilidad y la precisión de los datos medidos. Definir el grado de fiabilidad de las mediciones, es esencial para tener un punto de partida para llevar a cabo una correcta evaluación de la instalación. Así como las condiciones límite y los límites operacionales de la central. Cada prueba realizada en este trabajo contribuye a tener una mejor comprensión de la instalación y sus componentes. Además, contribuye a construir el conocimiento del MoNiKa. Y determinará la base para los próximos pasos de la investigación. Un software desarrollado por el instituto fue la principal herramienta utilizada para analizar la información obtenida de la instalación. GESI (Simulación Geotérmica). La definición de las necesidades de entrada para hacer coincidir el modelo con la instalación fue parte del desafío en este trabajo también. La comparación de los resultados del MoNiKa con el GESI se convierte en un proceso de retroalimentación. Donde al final de cada paso, se obtuvo una mejor comprensión de la instalación. Como resultado, se estudió en profundidad toda la prosa, la central eléctrica, y se desarrolló un módulo de GESI para simular futuros escenarios de MoNiKa.
  • Tesis de maestría
    Transient simulation and validation of a condenser for a supercritical organic Rankine cycle
    (2020) Fossati, Mariano Javier; Schulenberg, Thomas
    Este trabajo contiene el desarrollo de un modelo tanto, fluidodinámico como termodinámico, para un condensador con tubos horizontales y aletas planas, además de su aplicación para un modelo dinámico en Simulink con el propósito de estudiar los regímenes transitorios del condensador en una planta de investigación geotérmica móvil ubicada en Campus Nord KIT llamada MoNiKa. Durante el diseño del modelo, se probaron diferentes métodos y correlaciones para la predicción de la pérdida de presión y la transferencia de calor. Los resultados de la versión final, son presentados comparados con valores medidos para su validación. La validación se llevó a cabo en dos pasos, el primero se trata de una primera aproximación con diferentes puntos estacionarios, y el segundo con datos transitorios de las pruebas del MoNiKa. El modelo dinámico se construyó en Simulink con diferentes bloques basados en el código Matlab. Todas las propiedades físicas de los fluidos fueron extraídas del REFPROP, que es una base de datos del Instituto Nacional de Estándares y Tecnología (NIST). Todas las propiedades necesarias para la simulación se migran primero a una base de datos en Matlab y luego son utilizadas por el programa como tablas de búsqueda dinámica, esto ayuda a mejorar la respuesta temporal de la simulación. Parámetros como presión, entalpía y temperatura fueron comparados para la validación y el análisis de los valores predichos, donde se muestra una buena aproximación de la realidad. En el caso específico de la pérdida de presión, mejores sensores son necesarios para lograr un análisis conclusivo. Este primer modelo para un condensador transitorio es una buen modelo base, pero necesita ser mejorado, por ejemplo, para un escenario de aire húmedo, que es una de las características del condensador instalado.