Nonlinear model predictive control for hydrogen production in an ethanol steam reformer with membrane separation

© 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThis paper presents a new Nonlinear Model Predictive Control (NMPC) design for an Ethanol Steam Reformer with Pd-Ag membrane separation stage. The reformer is used to produce pure hydrogen able to feed a Proton Exchange Membrane Fuel Cell. Mass and energy balances are used to obtain the nonlinear dynamic model of both the reforming and the separation stages. Constraints, system nonlinearities and flexible cost function are the main reasons to select an NMPC controller, which is tested against the ordinary differential equations as simulation model, and has an internal model based on the sample data technique.Accepted versio

Control and optimization of a three-phase catalytic slurry intensified continuous chemical reactor

International audienceIntensified continuous mini-reactors working in high pressure and temperature conditions are particularly effective at coping with mass transfer limitations during three-phase catalytic reactions. They are highly non-linear, multivariable systems and behave differently from conventional batch, fed-batch or continuous non-intensified reactors. In this paper, the optimization and control of this new process are presented using a two-layer approach consisting of a hierarchical control structure with an optimization layer which calculates the set points for an advanced controller. The latter is based on the concavity of the entropy function and the use of thermodynamic availability as a Lyapunov function. The three-phase catalytic o-cresol hydrogenation performed under high pressure and temperature in a small-scale pilot of the RAPTOR® reactor designed by the French company AETGROUP SAS, is taken as a representative test example to illustrate the strategy. The performance of the control structure is illustrated by simulation

Utilizing Methods of Fluid Dynamics to Model Acoustic Movement

Acoustic theory is a branch of theoretical physics that attempts to explain the movement of sound through models of fluid dynamics and derivations from the Navier-Stokes equation of fluid movement. Foundational models of acoustic theory aimed to explain how sound moves on a microscopic level but have been unable to find reasonable evidence of how models of particle movement relate to what can be heard on a macroscopic scale. This thesis explores current models and research spawned from original models while attempting to unify and apply micro and macro aspects of acoustics, while finding applications of the unifying theory. There is an emphasis on the proposition and predictions of sound movement within a constantly changing environment. Findings illustrate potential links between the models of fluid dynamics and characteristics of acoustics, while current gaps from both fluid dynamics and links between topics prevent a fully cohesive theory from being established. Despite this, applications of how this theory can be used in live sound were found and lay a foundation for new types of technology and methods to be developed once the theory becomes fully established through continued research

Aeronautical engineering. A continuing bibliography with indexes

This bibliography lists 326 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1982. Topics on aeronautical engineering and aerodynamics such as flight control systems, avionics, computer programs, computational fluid dynamics and composite structures are covered

Mathematical modelling and advanced control design applied to high-pressure electrolyzers for hydrogen production

Tesi en modalitat de cotutela: Universitat Politècnica de Catalunya i Instituto Tecnológico de Buenos Aires. Aplicat embargament des de la defensa de la tesi fins al dia 30 de setembre de 2022This thesis is mainly dedicated to the study of high-pressure alkaline electrolysis. Alkaline electrolysis is a well established technology and is commercially available. However, the operation at high pressure for dispensing compressors was not fully investigated. Moreover, there is a lack of dynamic models and publications related to control strategies. Therefore, this thesis contributes especially in the modelling and control of high pressure alkaline electrolyzers in order to improve purity of produced gases. The thesis is framed within a general idea about the renewed concern for the care of the environment, which involves reducing greenhouse gas emissions without sacrificing modern comforts. Widespread proposal focuses on energy produced from renewable sources and its subsequent storage and transportation based on hydrogen. Currently, this gas applies to the chemical industry and its production is based on fossil fuels. The introduction of this energy vector requires the development of environmental-friendly methods for obtaining it. Existing techniques are presented and the main focus is made on electrolysis, a mature procedure. In turn, some developed proposals as previous steps to the hydrogen economy are presented. Moreover, some lines of research to improve electrolysis technology are commented. Afterwards, a phenomenological-based semiphysical model for a self-pressurized alkaline electrolyzer is proposed. The model, based on mass and energy balances, represents the dynamic behavior of hydrogen and oxygen production using electrolysis. The model allows to anticipate operational variables as dynamic responses in the concentrations of the electrolytic cell, and variations in both, level and pressure, at the gas separation chambers due to the change in electric current. The model parameters have been adjusted based on experimental measurements taken from an available prototype and through a suitable identification process. Simulation results replicate the current dynamic response of the experimental self-pressurized electrolyzer assembly. This model proves to be useful in the improvement of the control of gas production rate in this kind of assemblies, both as a validated simulation platform and as a source of reduced order models for model-based control design. Later, this thesis presents two control strategies that mitigate the cross contamination of H2 and O2 in a high-pressure alkaline electrolyzer, which consequently increases the supplied purity of the gases: one based on a decoupled PI scheme and the other based on optimal control tools. In order to reduce the diffusion of gases through the membrane, the controllers establish the opening of two outlet valves based on the pressure of the system and the difference in liquid level between both separation chambers. Therefore, two multiple input - multiple output controllers are designed. For this purpose, the high-fidelity model previously mentioned was simplified in order to obtain a control-oriented model. The proposed controllers were evaluated in simulation using the high-fidelity nonlinear model in a wide operating range, which resulted in less than 1% impurity of gases. In addition, tests were carried out in the prototype electrolyzer where the operation of the PI control was verified, obtaining even better results, with a maximum contamination of 0.2%.Aquesta tesi es dedica principalment a l'estudi de l'electròlisi alcalina d'alta pressiò. L'electròlisi alcalina és una tecnologia ben establerta i està disponible comercialment. Tanmateix, no s'ha investigat completament el funcionament a alta pressiò per a la distribuciò de compressors. A més, falten models dinàmics i publicacions relacionades amb les estratègies de control. Per tant, aquesta tesi contribueix especialment en el modelatge i control d'electrolitzadors alcalins d'alta pressió per tal de millorar la puresa dels gasos produïts. La tesi s'emmarca dins d'una idea general sobre la renovada preocupació per la cura del medi ambient, que consisteix a reduir les emissions de gasos d'efecte hivernacle sense sacrificar les comoditats modernes. Una proposta generalitzada es centra en l'energia produïda a partir de fonts renovables i el seu posterior emmagatzematge i transport basat en hidrogen. Actualment, aquest gas s'aplica a la indústria química i la seva producció es basa en combustibles fòssils. La introduccio d'aquest vector energètic requereix el desenvolupament de mètodes respectuosos amb el medi ambient per obtenir-lo. Es presenten les tècniques existents i es centra principalment en l'electròlisi, un procediment madur. Al seu torn, es presenten algunes propostes desenvolupades com a passos previs a l'economia de l'hidrogen. A més, es comenten algunes línies de recerca per millorar la tecnologia d'electròlisi. Posteriorment, es proposa un model semifísic de base fenomenològica per a un electrolitzador alcalí auto-pressuritzat. El model, basat en els balanços de massa i energia, representa el comportament dinàmic de la producció d'hidrogen i oxigen mitjançant electròlisi. El model permet anticipar variables operatives com a respostes dinàmiques en les concentracions de la cèl·lula electrolítica i variacions en el nivell i la pressió de les cambres de separació de gas a causa del canvi de corrent elèctric. Els paràmetres del model s'han ajustat en funció de mesures experimentals obtingudes en d'un prototip disponible i mitjançant un procés d'identificació adequat. Els resultats de la simulació repliquen la resposta dinàmica actual del conjunt experimental d'electrolitzador auto-pressuritzat. Aquest model demostra ser útil per millorar el control de la taxa de producció de gas en aquest tipus d'assemblatges, tant com a plataforma de simulació validada com a font de models d'ordre reduït per al disseny de control basat en models. Posteriorment, aquesta tesi presenta dues estratègies de control que mitiguen la contaminació creuada de H2 i O2 en un electrolitzador alcalí d'alta pressió, que en conseqüència augmenta la puresa subministrada dels gasos: una basada en un esquema de PI desacoblat i l'altra basada en un esquema de control òptim. Per tal de reduir la difusió de gasos a través de la membrana, els controladors estableixen l'obertura de dues vàlvules de sortida en funció de la pressió del sistema i de la diferència de nivell de líquid entre les dues cambres de separació. Per tant, es dissenyen dos controladors d'entrada i sortida múltiple. Amb aquest propòsit, el model d'alta fidelitat esmentat anteriorment s'ha simplificat per obtenir un model orientat al control. Els controladors proposats han estat avaluats en simulació mitjançant el model no lineal d'alta fidelitat en un ampli rang operatiu, el qual ha resultat en una impuresa de gasos inferior a 1%. A més, es van realitzar assajos al electrolitzador prototip on es va constatar el funcionament de l'control PI, obtenint inclusivament millors resultats, amb una contaminació màxima de 0,2%.Esta tesis está dedicada principalmente al estudio de la electrólisis alcalina de alta presión. La electrolisis alcalina es una tecnología bien establecida y está disponible comercialmente. Sin embargo, la operación a alta presión para dispensar el uso de compresores no ha sido investigada completamente. Además, hay una falta de modelos dinámicos y publicaciones relacionadas con las estrategias de control. Por tanto, esta tesis contribuye especialmente en el modelado y control de electrolizadores alcalinos de alta presión para mejorar la pureza de los gases producidos. La tesis se enmarca dentro de una idea general sobre la renovada preocupación por el cuidado del medio ambiente, que pasa por reducir las emisiones de gases de efecto invernadero sin sacrificar las comodidades modernas. La propuesta generalizada se centra en la energía producida a partir de fuentes renovables y su posterior almacenamiento y transporte a base de hidrogeno. Actualmente, este gas se utiliza en la industria química y su producción se basa en combustibles fósiles. La introducción de este vector energético requiere el desarrollo de métodos amigables con el medio ambiente para su obtención. Se presentan las técnicas existentes y se hace hincapié en la electrolisis, un procedimiento maduro. A su vez, se presentan algunas propuestas desarrolladas como pasos previos a la economía del hidrogeno. Además, se comentan algunas líneas de investigación para mejorar la tecnología de electrolisis. Posteriormente, se propone un modelo semifísico de base fenomenológica para un electrolizador alcalino autopresurizado. El modelo, basado en balances de masa y energía, representa el comportamiento dinámico de la producción de hidrogeno y oxígeno mediante electrolisis. El modelo permite anticipar variables operativas como respuestas dinámicas en las concentraciones de la celda electrolítica y variaciones tanto de nivel como de presión en las cámaras de separación de gases debido al cambio de corriente eléctrica. Los parámetros del modelo se han ajustado en base a medidas experimentales tomadas de un prototipo disponible y mediante un proceso de identificación adecuado. Los resultados de la simulación replican la respuesta dinámica actual del conjunto electrolizador autopresurizado experimental. Este modelo demuestra ser útil en la mejora del control de la tasa de producción de gas en este tipo de montajes, tanto como plataforma de simulación validada como fuente de modelos de orden reducido para el diseño de control basado en modelos. Después, esta tesis presenta dos estrategias de control que mitigan la contaminación cruzada de H2 y O2 en un electrolizador alcalino de alta presión, lo que consecuentemente aumenta la pureza suministrada de los gases: una basada en un esquema de PI desacoplado y otra basada en herramientas de control óptimo. Para reducir la difusión de gases a través de la membrana, los controladores establecen la apertura de dos válvulas de salida en función de la presión del sistema y la diferencia de nivel de líquido entre ambas cámaras de separación. Por lo tanto, se diseñan dos controladores de múltiples entradas y múltiples salidas. Para ello, se simplificó el modelo de alta fidelidad anteriormente mencionado para obtener un modelo orientado al control. Los controladores propuestos se evaluaron en simulación utilizando el modelo no lineal de alta fidelidad en un amplio rango operativo, lo que resultó en menos de 1% de impureza de gases. Además, se realizaron ensayos en el electrolizador prototipo donde se constató el funcionamiento de los controles PI y H1, obteniendo inclusive mejores resultados, con una contaminación máxima de 0;2 %.Postprint (published version

Off-design performance model of Organic Rankine Cycle systems

In questa tesi un modello di off-deisign dinamico di un ciclo Rankine organico è presentato. L'obiettivo del lavoro è sviluppare un modello dinamico per ogni singolo componente del sistema, creando una libreria di componenti pronti all'uso, utilizzabile anche in futuro per diverse simulazioni e diversi studi. Il modello sviluppato è utilizzato per simulare un'applicazione di recupero di calore di scarto da processi industrialiopenEmbargo per motivi di segretezza e/o di proprietà  dei risultati e informazioni di enti esterni o aziende private che hanno partecipato alla realizzazione del lavoro di ricerca relativo alla tes

Modelling And Optimization Of Micro-Channel And Thermal Energy Storage Heatsinks For Microelectronic Devices [TK7874. J44 2007 f rb].

Pemodelan dan pengoptimuman penyerap haba mikro-alur dan penyerap haba muatan dikaji dalam penyelidikan sini. Penyerap haba mikro-alur merupakan teknologi penyejukan yang berkesan untuk menyingkirkan tenaga haba yang tinggi daripada kawasan yang kecil dan terhad di dalam perkakasan mikroelektronik. The modelling and optimization of micro-channel and Thermal Energy Storage (TES) heatsinks in electronic cooling are investigated in the present study. The microchannels heatsinks is an efficient cooling technology to remove large amount of heat from very small and constrained areas of the high heat flux of microelectronic devices

Formation of screen-printed contacts on multicrystalline silicon (mc-Si) solar cells

Commercial multicrystalline silicon (me-Si) solar cells use screen-printing process for depositing both the Ag paste based gridded front and Al based back (whole area) metal contacts.. This thesis relates to experimental and theoretical studies of contact formation mechanisms in silicon solar cells. Temperature distribution studies during optical processing by. attached thermocouples to cells indicates that the maximum temperature reached under the front silver metal is less. than 800°C; this is lower than the eutectic point of Ag-Si (≈835°C). An analysis of the interaction of Ag particles and Si via the constituents of glass is given. This mechanism leaches metallic ions (solvent metals such as Pb, Bi or Zn), which cover the Ag particles and form a material of surface composition with low-melting-point. The low-temperature melt facilitates agglomeration of Ag and formation of a shallow alloy between Si, Ag, and the solvent metal. Ag-glass-Si interactions lead to the formation of Ag-rich and Si-rich areas at the metal-semiconductor .interface. The non-uniformity of the Ag-si interaction leads to degradation of various electrical parameters (i.e., fill factor and open circuit voltage (Voc)). A hypothesis invoking ion .exchange phenomena for front contact formation is presented. Ag-Si, Ag-glass, glass-Si and Ag-glass-Si reactions are discussed. SIMS study on etched cells shows that a significant consumption of phosphorous occurs during Si-Ag interaction. Scanning Kelvin Probe Microscopy profiles have been studied to measure the surface potential of the metal semiconductor region. Current Voltage characteristics of the fired cells are presented. An improved technique to cross-section large lengths of wafers/solar. Cells for statistically meaningful analyses of the metal semiconductor interface is presented. Results and applications of study of the temperature distribution across. the cell during firing, by contact thermocouples are presented. Thermal modeling predicts a temperature gradient of more than 10°C across the cell width due to combined effect of shadowing and thermal mass of the metal grid. However, experimentally, no systematic effect of the temperature gradient is seen on the front contact formation mechanism. A study on the back Al -contact formation revealed that Si diffusion led to several defects (e,g. bumps, holes, shunts) in the cells