We develop a simplified one-dimensional numerical model that simulates the performance of thermoelectric generators (TEG). The model is based on the energy and electrical potential field equations. The Seebeck coefficient, thermal conductivity, electrical resistivity and Thomson coefficient of the TEG material are used to predict the harvested power. Bismuth-telluride is used as semiconductors materials of the TEG, which is the most commonly used material by industry. Experiments on three TEG modules were performed to validate the numerical model. A comparison with predicted levels of harvested energy based on the TEG specifications is also performed. The results show differences between the experimental and numerical values on one hand and the predicted ones on the other hand. The reason for these differences are discussed. A procedure to estimate the sensitivity of the harvested power to different inputs and TEG parameters is detailed. In the second part of the dissertation, we integrate a thermoelectric generator with an organic storage device. The performance of the integrated system for different values of load resistances and temperature gradients is determined. Finally, we demonstrate that power generated from a TEG is related to the flow rate in a pipe and can, thus, be used as a flow meter. Particularly, a dimensionless relation between the TEG's peak power and Reynolds number is determined. / Ph. D.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2018-05-10T12:43:43Z No. of bitstreams: 2 Dissertação - Pedro Henrique Garcia Gomes - 2017.pdf: 18559039 bytes, checksum: 2c3827e2a3489268f95f4480e2a20904 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-05-10T12:44:26Z (GMT) No. of bitstreams: 2 Dissertação - Pedro Henrique Garcia Gomes - 2017.pdf: 18559039 bytes, checksum: 2c3827e2a3489268f95f4480e2a20904 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-05-10T12:44:26Z (GMT). No. of bitstreams: 2 Dissertação - Pedro Henrique Garcia Gomes - 2017.pdf: 18559039 bytes, checksum: 2c3827e2a3489268f95f4480e2a20904 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-12-05 / The objective of this work is to seek greater efficiency in energy conversion using the Seebeck modules, from the duct geometry optimization exhaust hot gases. Different materials and geometries are tested. The duct thickness was varied along the longitudinal fluid flow and optimized parameters are obtained heuristically . After the development of optimized duct model, a prototype is built for testing in the actual system. From the resistive air layer, the surface temperature gradient equalization is obtained, improving the efficiency of the system. / O objetivo deste trabalho é buscar maior eficiência na conversão energética através dos módulos Seebeck, a partir da otimização da geometria do duto de exaustão de gases quentes. Diferentes materiais e geometrias são testadas. A espessura do duto é variada segundo o escoamento longitudinal do fluido e parâmetros otimizados são obtidos heurísticamente. Após o desenvolvimento do modelo otimizado do duto, é construído protótipo para ensaio no sistema real. A partir da camada de ar resistiva, obtém-se a equalização do gradiente de temperatura na superfície, melhorando a eficiência do sistema.

Polymers that undergo dramatic changes in structural conformations in response to numerous stimuli such as temperature, pH, electric and magnetic fields, light inten- sity, biological molecules, and solvent polarity, are known as stimuli-responsive or ”smart” polymers. There is a broad range of very promising applications of these materials in catalysis, environmental remediation, sensors or actuator systems, and as delivery systems of therapeutic agents. Researchers have been trying to mimic smart polymers based on properties of polymers found in nature such as proteins, carbohydrates and nucleic acids. Novel bio-compatible polymers with a variety of chemical functional groups, diverse topologies, and cross-linking patterns with the ability to self-assemble in vivo are being engineered. Experimental and theoretical studies indicate that the thermodynamic properties relating to the hydrophobic effects play a pivotal role in determining the self-assembly process in smart polymers. At the same time, computational approaches based on simulation and modeling provide an understanding of this phenomenon on the micro- scopic level. Building empirical models based on statistical mechanics methods and simulation data helps to design polymeric materials with desirable traits. My research is mainly focused on investigating physicochemical characteristics of stimuli-responsive polymers under different conditions. I used atomistic molecular dynamics simulations to investigate these effects on polymer conformation. Given the size and complexity of our polymeric systems, we employed Graphical Process- ing Units (GPU) and enhanced sampling techniques such as REDS2 to increase the sampling time. These methods allow for the study of polymeric structural dynamics in solvents of varying polarity and in human skin epidermis. Our constant pH simulation of poly(methacrylic acid) revealed that the overall response is made up of local and global structural changes. The local structural re- sponse depends on the tacticity of the polymer, which leads to distinct cooperative effects for polymers with varying stereochemistry. Such simulations help to under- stand the principal driving forces behind the mechanism of self-assembly processes.

This master's thesis informs its reader about actual energetical situation of Poland and its probable future. The thesis focus on shale gas resesources in the world and Poland and methods of its mining and procesing. Main problematics of determining, designing and technology of TEG dehydration unit were described in this thesis.

Thermoelectric generators (TEGs) are currently a topic of interest in the field of energy harvesting for automobiles. In applying TEGs to the outside of the exhaust tailpipe of a vehicle, the difference in temperature between the hot exhaust gases and the automobile coolant can be used to generate a small amount of electrical power to be used in the vehicle. The amount of power is anticipated to be a few hundred watts based on the temperatures expected and the properties of the materials for the TEG. This study focuses on developing efficient heat exchanger modules for the cold side of the TEG through the analysis of experimental data. The experimental set up mimics conditions that were previously used in a computational fluid dynamics (CFD) model. This model tested several different geometries of cold side sections for the heat exchanger at standard coolant and exhaust temperatures for a typical car. The test section uses the same temperatures as the CFD model, but the geometry is a 1/5th scaled down model compared to an full-size engine and was fabricated using a metal-based rapid prototyping process. The temperatures from the CFD model are validated through thermocouple measurements, which provide the distribution of the temperatures across the TEG. All of these measurements are compared to the CFD model for trends and temperatures to ensure that the model is accurate. Two cold side geometries, a baseline geometry and an impingement geometry, are compared to determine which will produce the greater temperature gradient across the TEG. / Master of Science

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<p>With the rising prices of energy and the harmful environmental effects many of conventional energy generation techniques the world is pushing for new, cleaner, more efficient and more environmental renewable energy sources. Thermoelectric generators are one of the potential solutions to these problems of unclean and expensive energy. Thermoelectric generators are solid state devices that convert thermal energy into useful electrical energy.</p> <p>Over the last ten years the progress in materials science have led to advancements in thermoelectrics. However as of yet no standardised method of testing thermoelectric generators has been established and as such data provided for thermoelectric generators is regarded as questionable. This thesis deals with two commercial thermoelectric generator models, TEG1 12610-5.1 AND TEG1B 12610-5.1, and quantifies the deviation of the manufacturer’s specifications to what is experimentally achieved by the generators as 147% and 22% respectively. The variance of the outputs between thermoelectric generators was measured by comparing the maximum power output for the models in question over a sample size of four, it was found to be as much as 20% and 8% respectively.</p> <p>A full characterisation of the thermoelectric generators is performed on the two generator models to obtain the data as to their power output and thermal conductivity for the purpose of design of a waste energy harvesting device. The full characterisation was also used to validate the testing apparatus as a device capable for the use as a standardised method of characterising the performance of thermoelectric generation modules.</p> <p>A mechanistic model is created using the experimental characterisation data. This mechanistic model has the ability to accurately predict the voltage and current output of the thermoelectric generator models under any given temperatures and electrical loading condition with a minimum R-squared value of 0.94. The thermal conductivity is also found to be predictable using an established equation modified with an empirical constant.</p> / Master of Applied Science (MASc)

Thermoelectric generators (TEGs) are currently being explored for their potential in harvesting energy from automobile exhaust. TEGs in form of an appropriate TEG- Heat exchanger module can utilize the temperature difference between the hot exhaust gases and the automobile coolant and convert it into electrical voltage. The amount of power is anticipated to be a few hundred watts depending on the temperature gradient and the material of the TEGs. The focus of this study is increasing the hot side heat transfer for improved performance of the thermoelectric generators using two different internal fins — louvered fins and herringbone wavy fins. The multi-louvered fins basically have 'multi flat plate' behavior and will enhance the heat transfer by deflecting the air from its original path and aligning it with the plane of the louvers. Herringbone fins are used to lengthen the path of airflow allowing for greater residence time and better mixing of the flow. They also provide for greater wetted surface area achieving higher heat transfer. The flow and heat transfer behavior inside the exhaust pipe test section with internal fins is modeled using commercial numerical software. The thermal and flow behavior through both these internal fins depends to a large extent on geometric parameters and fin arrangement. Optimization of the fin design is considered to determine the configuration that provides highest heat transfer while providing least pressure drop across the pipe length. The heat transfer and pressure drop characteristics are compared to the baseline flow without any fin enhancement. / Master of Science

Att minska energianvändningen är något det pratats mer och mer om de senaste åren. Det finns olika sätt att minska energianvändningen på och ett av dessa är att återvinna värmeenergi. Det kan gälla både spillvärme och nyttig värme. Detta går att tillämpa i industrin, transportsektorn, hushåll och till vardags. Gemensamt för dessa processer är att det används stora mängder energi vilket till stor grad består av förluster till omgivningen eller att processerna inte optimeras. På senare tid har det forskats kring teknologi som kan ta vara på denna värmeenergi och på så vis minska förlusterna. En teknologi för detta är termoelektriska generatorer (TEG) som bygger på Seebeckeffekten för att generera elektricitet från temperaturskillnader. När ett TEG-element utsätts för värme på en sida och kyla på den andra sidan så genereras en elektrisk spänning. En elektrisk ström och effekt kan tas ur kretsen om elementet kopplas till en elektrisk last. Materialet i elementet består av halvledarmaterial med låg värmeledningsförmåga och en hög elektrisk ledningsförmåga. Teknologin har funnits länge men aldrig tillämpats i någon större grad. Nu på senare år har intresset ökat och kommersiella produkter med TEG-element har tagits fram. I detta arbete har en sådan produkt testats för att se hur lämpligt det skulle vara att använda dessa vid hushåll som inte är anslutna till elnätet och har en vedkamin för uppvärmning. TEG-enheten testas på en värmeplatta där ställbara temperaturer är möjliga för att testa prestandan vid temperaturerna 150° C, 200° C och 230° C. En krets sätts ihop för att kunna mäta av värden på spänning och ström vid olika laster som sätts med resistorer. Mätningarna görs med en ökning på 0,1 A vid varje mätning. Resultatet från dessa tester visar att maximal effekt på 14 W uppnås hos produkten vid 230° C. När modifiering av produkten görs för att öka temperaturskillnaden uppnås 17,8 W vilket tyder på att effekten ökar när delta T ökar. Den spänning som uppnås vid öppen krets var som högst 31 V och vid maximal effekt var den 17,8 V. Strömmen var då 1 A. De resultat som testerna gav levde inte upp till de 25 W som produkten sägs kunna ge. Produkten saknar även viktiga komponenter så som spänningsreglerare.Det går av både teori och tester avgöra att det är ett lämpligt sätt att använda sig av TEG-enheter för att generera små mängder elektricitet vid hushåll utan koppling till elnätet. / In recent years the topic of reducing the energy usage has been on the agenda. There are several ways of reducing the energy usage and one of these is to recycle heat energy. It could be both waste heat and useful heat. This can be implied to the industry, transport sector, households and on daily activities. The common factor between these is that large quantities of energy is used and to a large extent consists of losses to the surrounding or from processes that are not optimized. In recent time there has been done research around technology that can recycle and use this heat energy and in return reduce the energy usage. One technology to do this is thermoelectric generators (TEG) that are implementing the Seebeck effect to generate electricity from temperature differences. When a TEG-element have one side that is exposed to a heat source and one side being cooled down an electric voltage is being generated. An electric current and power can then be used from the circuit if the element is connected to an electric load. The material in the element exists of semiconductive materials with low heat conductivity and high electric conductivity. The technology has existed for a long time but has never been implemented to a larger extent. It is only in recent years that the interest has grown and some commercial products with TEG-elements has been developed. In this thesis one of these products has been tested to see how viable it would be to use these within a household that is not connected to the electrical grid and where the house is heated with a wood-burning stove. The TEG-product is tested on a heat plate where it is possible to set a desired temperature. The temperatures of 150° C, 200° C and 230° C are chosen for testing the performance of the product. A circuit is put together to be able to read the values of the voltage and current at different loads that are set with resistors. The measurements are done with an increase of 0,1 A for every measurement. The result from these tests shows that the maximum power of 14 W is achieved at 230° C on the hot side. But when modification of the product is made to increase the temperature difference a value of 17,8 W is attained. This indicate that the power is increasing when the temperature difference is increasing. The attained voltage at open circuit was as highest 31 V and at maximum power it was 17,8 V. The current was then 1 A. The results that the testing gave did not match the value of 25 W that the datasheet says the product can deliver. Also, the product is missing important components such as voltage regulator.It is possible from both the theory and the testing to see that it is suitable to use a TEG-product to generate small amount of electricity to households that are not connected to the electrical grid.