Die vorliegende Arbeit forciert die Steigerung der Leistungsfähigkeit netzautarker thermoelektrischer Systeme. Hierunter werden im Folgenden Apparate verstanden, die mittels thermoelektrischer Generatoren (TEG) thermische Energie in Elektroenergie umwandeln, um damit netzautark und dezentral elektrische Kleinstverbraucher an großtechnischen Anlagen und Maschinen zu speisen. Bei den elektrischen Verbrauchern kann es sich beispielsweise um Sensoren zum Vermessen unterschiedlicher Prozessgrößen handeln. Aber auch eine Energieversorgung von Geräten zur drahtlosen Datenübertragung und Aktoren mit entsprechend geringer Leistungsaufnahme ist mittels netzautarker thermoelektrischer Systeme technisch möglich. Zum Erreichen der Zielstellung werden die TEG zur Energieumwandlung nicht isoliert betrachtet, sondern der optimierte Systemaufbau ganzheitlich forciert. Denn zur Steigerung der Leistungsfähigkeit netzautarker thermoelektrischer Systeme müssen alle Komponenten betrachtet: Angefangen von den TEG über die notwendige Wärmekopplung bis hin zu weiteren Peripheriegeräten. Im Konkreten basiert die in dieser Dissertation dargelegte Entwicklungsarbeit zum einen auf einem mathematischen Modell zur Berechnung verlustbehafteter TEG-Wärmeübertrager-Systeme, zum anderen auf der Entwicklung eines effizienten Wärmeübertragers zur passiven Kühlung thermoelektrischer Module sowie der Darstellung und Diskussion eines Gleichstromwandler-Schaltkreises für die Regelung des Betriebszustands eines angekoppelten TEG.

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Wastewater treatment has developed as a mature technology over time. However, conventional wastewater treatment is a very energy-intensive process. Bioelectrochemical system (BES) is an emerging technology that can treat wastewater and also recover resources such as energy in the form of electricity/hydrogen gas and nutrients such as nitrogen and phosphorus compounds. Microbial electrolysis cell (MEC) is a type of BES that, in the presence of an additional voltage, can treat wastewater and generate hydrogen gas. This is a promising approach for wastewater treatment and value-added product generation, though it may not be sustainable in the long run, as it relies on fossil fuels to provide that additional energy. Thus, it is important to explore alternative renewable resources that can provide energy to power MEC. Waste heat is one such resource that has not been researched extensively, particularly at the low-temperature spectrum. This was utilized as a renewable resource by converting waste heat to electricity using a device called thermoelectric generator (TEG). TEG converted simulated waste heat from an anaerobic digester to power an MEC. The feasibility of TEG to act as a power source for an MEC was investigated and its performance compared to the external power source. Various cold sources were analyzed to characterize TEG performance. To explore this integrated TEG-MEC system further, a hydraulic connection was added between the two systems. Wastewater was used as a cold source for TEG and it was recirculated to the anode of the MEC. This system showed improved performance with both systems mutually benefitting each other. The operational parameters were analyzed for the optimization of the system. The integrated system could generate hydrogen at a rate of 0.36 ± 0.05 m3 m-3 d-1 for synthetic domestic wastewater treatment. For the practical application, it is necessary to estimate the cost and narrow the focus on the functions of the system. Techno-economic analysis was performed for MEC with cost estimation and net present value model to understand the economic viability of the technology. The application niche of the BES was described and directions for addressing the challenges towards a full-scale operation were discussed. The present system provides a sustainable method for wastewater treatment and resource recovery which can play an important role in human health, social and economic development and a strong ecosystem. / Doctor of Philosophy / An average person produces about 50-75 gallons of wastewater every day. In addition to the households, wastewater is generated from industries and agricultural practices. As the population increases, the quantity of wastewater production will inevitably increase. To keep our rivers and oceans clean and safe, it is essential to treat the wastewater before it is discharged to the water bodies. However, the conventional wastewater treatment is a very energy (and thus cost) intensive process. For low-income and developing parts of the world, it is difficult to adapt the technology everywhere in its present form. Furthermore, as the energy is provided mostly by fossil fuels, their limited reserves and harmful environmental effects make it critical to find alternative methods that can treat the wastewater at a much lower energy input. For a circular and sustainable economy, it is important to realize wastewater as a resource which can provide us energy, nutrients, and water, rather than discard it as a waste. Bioelectrochemical systems (BES) is an emerging technology that can simultaneously treat wastewater and recover resources in the form of electricity/hydrogen gas, and nitrogen and phosphorus compounds. Microbial electrolysis cell (MEC) is a type of BES that is used to treat wastewater and generate hydrogen gas. An additional voltage is supplied to the MEC for producing hydrogen. In the long run, this may not be sustainable as it relies on fossil fuels to provide that additional energy. Thus, it is important to explore alternative renewable resources that can provide energy to power MEC. Waste heat is a byproduct of many industrial processes and widely available. This was utilized as a renewable resource by converting waste heat to electricity using a device called thermoelectric generator (TEG). TEG converted simulated waste heat from an anaerobic digester to power an MEC. The mutual benefit for MEC and TEG was also explored by connecting the system electrically and hydraulically. Cost-estimation of the system was performed to understand the economic viability and functions of the system were developed. The present system provides a sustainable method for wastewater treatment and resource recovery which can play an important role in human health, social and economic development and a strong ecosystem.

L'augmentation du prix du pétrole ainsi qu'une possible future réglementation des émissions de CO2 encourage les fabricants de véhicules industriels à trouver de nouvelles solutions pour améliorer encore la performance de la chaine cinématique. Dans ce cadre, deux solutions de récupérations d'énergie prometteuses sont très souvent rapportées dans la littérature: le système de récupération d'énergie par cycle de Rankine et le générateur thermoélectrique. Après un rappel des conditions limites du fonctionnement d'un camion long routier, cette thèse démontre tout d’abord la modélisation 0-D et 1-D (logiciels commerciaux utilisés) de ces deux systèmes de récupération d’énergie. Pour le générateur thermoélectrique, des études paramétriques (hauteur de jambe thermoélectrique, prix, puissance électrique produite) sont effectuées se basant principalement sur l'utilisation de deux matériaux prometteurs. Une conception du système Rankine est présentée et modélisée avec le solveur 1-D. Des validations partielles sont réalisées sur les composants (turbine). Ce modèle a ensuite permis d'étudier les transitoires du système ainsi que la charge en réfrigérant et un système de contrôle possible. Cette étude montre que le générateur thermoélectrique n’est pas encore mature pour son utilisation dans un camion long routier. Le système Rankine doit quant à lui être testé sur un camion prototype pour pouvoir véritablement estimer son potentiel final / Fuel price increase as well as future fuel consumption regulations lead truck manufacturers to further enhance the current powertrain. In such a context, two waste heat recovery technologies appear as promising: the Rankine system as well as the thermoelectric generator. After a reminding of truck boundary conditions, this thesis work defines 0-D and 1-D modeling (commercial tool used) for both systems.For the thermoelectric generator , parametric 1-D studies are done on the integration/design (number of thermoelements, price, electrical power) of a thermoelecric generator upstream the existing engine exhaust gas recirculation cooler. Main studies are done with thermoelectric materials but other materials are also considered. A Rankine system design is presented and modeled under a 1-D solver. Preliminary validations are presented. Transient aspects are evaluated to better understand the behavior of the system and its bottlenecks. The amount of refrigerant in the circuit and the control schematic are also addressed.From these studies, it appears that the thermoelectric generator technology is not yet mature for a long haul truck due to the low performance of thermoelectric materials. The Rankine system technology should handle a complete truck prototype testing to estimate its potential

Une des préoccupations majeures de la recherche dans le domaine de l’énergie est la diminution de la production des gaz à effet de serre et la réduction de notre empreinte écologique. Les générateurs thermoélectriques participent à une démarche globale d’efficacité énergétique en convertissant directement une partie de l’énergie thermique qui les traverse en énergie électrique. Ces derniers sont encore peu utilisés et rares sont les travaux qui traitent de leur optimisation. Ce travail a permis d’explorer les stratégies d’intégration des modules thermoélectriques dans les ensembles définis par les utilisateurs finaux en utilisant une méthodologie basée sur une modélisation complète des systèmes du flux de chaleur à la production électrique. Un code numérique couplant les équations de la thermique, de la thermoélectricité et de l’électricité a été développé et permet d’observer l’influence de plusieurs paramètres sur la production d’électricité (débit et température de la source chaude, débit et température de la source froide, type de modules thermoélectriques, emplacement des modules,…). La validation de ce modèle a nécessité la réalisation et l’instrumentation de plusieurs prototypes expérimentaux dont le plus conséquent est une boucle d’air à haute température alimentant un prototype de générateur thermoélectrique modulable. La conception et la réalisation de convertisseurs électriques dédiés, à recherche du point de fonctionnement maximal (MPPT), a permis de tester ces prototypes au point d’adaptation optimale. Enfin, une méthode d’optimisation appliquée au modèle nous délivre le nombre de modules ainsi que leur emplacement pour une production électrique maximale. Un outil de dimensionnement et d’optimisation de générateurs thermoélectriques est maintenant disponible. Il nous a permis tout d’abord d’étudier la faisabilité d’une production d’électricité en zones isolées au travers d’un prototype de cuisinière à bois thermoélectrique. Puis nous avons analysé la faisabilité dans le domaine de l’automobile en se plaçant à un point de fonctionnement précis correspondant au gaz d’échappement. / A major concern of research in the field of energy is the decrease in the production of greenhouse gas emissions and reducing our ecological footprint. Thermoelectric generators participate in a comprehensive approach to energy efficiency by directly converting a part of the thermal energy that flows through in electricity. This work explore strategies for integrating thermoelectric modules in sets defined by end users using a methodology based on a complete systems modelling from heat flow to power generation. A numerical code coupling equations of heat transfers and thermoelectricity was developed and used to observe the influence of several parameters on the production of electricity (flow and temperature of the hot source, flow and temperature of the cold source, type of thermoelectric modules, module location...). The validation of this model has necessitated the construction and the instrumentation of several experimental prototypes which for the most important is a hot air loop supplying a prototype flexible thermoelectric generator. The design and the realization of dedicated electrical converters to research the maximum operating point (MPPT) was performed to test these prototypes optimal adaptation issue. Finally, an optimization method applied to the model delivers us the number of modules and their location for maximum power production. A tool for design and optimization of thermoelectric generators is now available. It has allowed us to study the feasibility of an integrated thermoelectric generation in a variety of systems such as the automobile using exhaust gas or a specific cook stove for developing countries.

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<p dir="ltr">Sensing and communication circuits and systems are crucial components in various electronic devices and technologies. These systems are designed to acquire information from the surrounding environment through sensors, process that information, and facilitate communication between different devices or systems. It plays a vital role in modern electronic devices, enabling them to collect, process, and exchange information to perform various functions in applications such as IoB (Internet of Body), healthcare, hardware security, industrial automation, and more.</p><p dir="ltr">This work focuses on innovations in sensing and communication circuits spanning two independent application areas – human body communication and hardware emanations security.</p><p dir="ltr">First, an ultra-low power ECG monitoring system is implemented to perpetually power itself using Thermoelectric Generator (TEG) to harvest body energy while securely transmitting sensed data through on-body communication, achieving closed-loop operation without external charging or batteries. Custom circuits allow demonstrated feasibility of self-sustaining wearables leveraging Human Body Communication’s advantages.</p><p dir="ltr">Second, investigations reveal vulnerabilities introduced when repairing broken cables, with unintended monopole antennas boosting electromagnetic emissions containing signal correlations. Experiments characterize long-range detection regimes post-repair across USB keyboard cables. Further circuit and structural innovations provide localized shielding at repair points as a potential mitigation. Advancements offer contributions in understanding hardware emission security risks to inform protection strategies.</p><p dir="ltr">The two separate research work demonstrate specialized circuits advancing the state-of-the-art in sensing and communication for wearable body-based systems and hardware security through greater awareness of vulnerabilities from unintended emissions.</p><p><br></p>

Aufgrund von steigenden Energiekosten und einer sukzessive steigenden öffentlichen sowie politischen Forderung nach Umweltbewusstsein und Nachhaltigkeit, ist die Effizienzsteigerung von Gesamtsystemen einer der treibenden Kräfte für innovative, technologische Neuheiten geworden. Besonders bei der Entwicklung von verbrennungsmotorisch angetriebenen Fahrzeugen wurden z.B. durch die Hybridisierung von Antriebssträngen, die die Rekuperation von kinetischer Energie ermöglichen, Technologien zur Energieeinsparung etabliert. Da bei Verbrennungsmotoren ein hoher Anteil der im Kraftstoff gespeicherten Energie technologiebedingt als Abwärme im Abgas verloren geht, bietet die Wärmerekuperation ein weiteres hohes Potential für weitere Einsparungen. Diese ist z.B. mit Hilfe von thermoelektrischen Generatoren (TEG) möglich, die einen Wärmestrom direkt in elektrische Energie umwandeln. Zur effizienten TEG-Systemgestaltung ist ein hoher Temperaturgradient über dem thermoelektrisch aktivem Material notwendig, der wiederum zu kritischen thermomechanischen Spannungen im Bauteil führen kann. Diese werden zum einen durch die unterschiedlichen Temperaturausdehnungskoeffizienten der verschiedenen Materialien und zum anderen durch die mechanische Anbindung auf der heißen und kalten Seite des TEG verursacht. Somit liegt ein Zielkonflikt zwischen dem thermoelektrischen Systemwirkungsgrad und der mechanischen Festigkeit des Bauteils vor. In dieser Arbeit wird mit Hilfe einer mehrkriteriellen Parameteroptimierung eines vollparametrisierten FE-Modells des TEG in ANSYS WORKBENCH eine Methode vorgestellt, den thermoelektrischen Wirkungsgrad bei gleichzeitiger Reduktion der thermomechanischen Spannungen zu optimieren. Zur Optimierung kommt dabei ein genetischer Algorithmus der MATLAB GLOBAL OPTIMIZATION TOOLBOX zum Einsatz. Der Modellaufbau wird in ANSYS WORKBENCH mit der Makro-Programmiersprache JSCRIPT realisiert. Als Ziel- und Bewertungsfunktionen wird die mechanische Belastung jedes Bauteils im TEG ausgewertet und dessen elektrische Leistungsdichte berechnet. Die Ergebnisse zeigen, dass mit Hilfe der vorgestellten Methodik eine paretooptimale Lösung gefunden werden kann, die den gestellten Anforderungen entspricht.

Cette thèse porte sur le développement d’un cogénérateur résidentiel constitué d’un générateur linéaire asynchrone entraîné par deux moteurs Stirling fonctionnant en mode ‘piston libre double effet’. Les critères caractérisant un tel cogénérateur sont décrits ainsi que ses différents modes d’utilisation dans le domaine résidentiel. Les différentes technologies sont passées en revue.Les équations de la mécanique sur lesquelles se fondent le contrôle du couplage thermoélectrique du cogénérateur et sa stabilité y sont définies. Le générateur électrique est modélisé en vue de calculer les grandeurs électriques des équations à bobines couplées et les grandeurs du schéma électrique équivalent, ce schéma permet d’inverser le modèle.Les résultats des modèles analytiques sont validés par des mesures faites sur des maquettes spécialement conçues. Une étude paramétrique de la structure du générateur a permis d’optimiser ses performances. Les équations de la mécanique et le modèle électrique sont utilisés pour poser les bases d’une optimisation ‘système’ du cogénérateur. / This thesis focuses on the development of a residential cogenerator which consists of a linear induction generator driven by two Stirling engines, free-piston double-acting operating mode. The criteria characterizing such cogenerator are described and its various modes of use in the residential sector. The various technologies are reviewed.The equations of mechanics that underlie the control of the coupling of thermoelectric cogeneration and stability are defined.The electric generator is modeled to calculate the electrical coil coupled equations and the magnitudes of the equivalent circuit, this scheme allows us to reverse the pattern. The results of analytical models are validated by measurements on specially designed models. A parametric study of the structure of the generator has optimized its performances. The equations of mechanical and electrical model are used to lay the groundwork for optimization of all the cogenerator, considered as a system.

Os materiais cerâmicos termoelétricos preparados a partir de ligas de SiGe, são utilizados em Geradores de Potência a Radioisótopos (GTR), na conversão de energia por efeitos termoelétricos. Neste trabalho de pesquisa foram estudadas as condições de preparação destas cerâmicas a partir de ligas de Silício-Germânio. Visou-se, portanto obter a melhor eficiência, pela otimização da \"Fator de Mérito\" (ou Número de loffe) , através dos processos de preparação e tratamentos térmicos da liga, e também na dopagem das cerâmicas. As ligas de silício-germânio (Si80Ge20) foram obtidas pela técnica de crescimento Czochralski, com campo elétrico aplicado (ECZ) e também por outras técnicas de fusão e solidificação, para comparação. Amostras com homogeneidade satisfatória foram quebradas e moídas para processamento cerâmico. E em seguida o pó da liga foi então dopado, misturando-se este com pó de boro amorfo e depois prensado, a fim de se obter elementos cerâmicos semicondutores tipo-p, com propriedades termoelétricas para altas temperaturas (&#8776 1000&#176C). A sinterização foi feita por três técnicas diferentes: pela técnica dos Pós Discretos ou PIES (Pulverized and Intermixed Elements of Sintering), pelo procedimento cerâmico convencional, e pela Prensagem a Quente (HotPressing), sendo esta última usada como padrão de comparação. As amostras obtidas foram analisadas e caracterizadas por técnicas convencionais de caracterização cerâmica tais como: medidas da densidade, dos tamanhos dos grãos, porosidade, área superficial, etc. e também por medidas de alguns dos parâmetros físicos que influenciam diretamente na eficiência termoelétrica tais como: coeficiente Seebeck, calor específico e parâmetro de rede, para ligas de composição nominal Si80Ge20 sem e com dopantes para semicondutores tipo-p. Uma amostra preparada pela General Electric usando a técnica de Prensagem a Quente (Hot-Pressing), foi usada como padrão de comparação. A liga obtida pela técnica ECZ apresentou boa homogeneidade. Foi encontrado que a qualidade microestrutural das cerâmicas tais como: densidade, a regularidade e a composição química dos grãos das cerâmicas depende muito da técnica de processamento. Estes elementos cerâmicos termoelétricos poderão ser usados como fonte de energia em Geradores de Potência Termoelétrica a Radioisótopos (GTR) mais especificamente na alimentação de satélites brasileiros fabricados pelo Centro Técnico Aeroespacial (CTA) junto com o Instituto de Estudos Avançados (IEAv) através da Divisão de Energia Nuclear (IEAvENU) deste Instituto, ou entre outras aplicações para fins militares e civil / Doped ceramics elements, prepared from Si-Ge alloy are used in Radioisotopic Thermoelectric Generators (GTR) for energy conversion by thermoelectrical effects. In this research the experimentais conditions to prepare thermoeletric ceramics from Silicon-Germanium alloys have been determined. The purpose was to get the best efficiency, by optimization of the \"Merit Figure\" (or \"loffe Number\'), using different preparation methods and thermal treatments of alloys, as well as the doping of these ceramics. Silicon-Gemanium alloys (Si80Ge20) have been grown by the Czochralski technique under applied eletric field (ECZ) , as well as by others fusion techniques for comparison. Afier the fusion of the alloy, samples with satisfactory homogeneity have been smashed and milled for ceramic processing. Powder of Si-Ge alloy was then heavely doped by mixing with amorphous boron powder and pressed to get type-P semiconductor thermoelectrical ceramics elements, at high temperatures (&#8776 1000 &#176C). The sintering was made by three differents techniques: PIES method (Pulverized and Intermixed Elements of Sintering), convencional ceramic processing, and Hot-Pressing sintering, for comparison. The samples have been analyzed and characterized by conventional ceramics technique such as: determination of density, grain size, porosity, surface area, etc. and measuring toa some physical parameters that affect directly the thermoelectrical efficiency such as: Seebeck coefficient, specific heat and lattice parameter to Silicon-Germanium alloys with nominal composition Si80Ge20 with or without dopings to type-P semiconductors. A sample prepared by General Electric Company using the Hot-Pressing technique was used as standard. The alloy grown by ECZ technique showed a good homogeneity. It was found that the microstructural quality of the ceramics such as: density, grains regularity and chemical composition of the ceramics depend of the ceramic processing technique. These thermoelectrical elements can be used as power supply for the Brazilian satellites made by the Centro Técnico Aeroespacial (CTA) together with the Instituto de Estudos Avançados (IEAv) through the Divisão de Engenharia Nuclear (ENU) , and among other applications for military and civil purposes