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Piesciorovsky, Emilio Carlos. "Heat gain from power panelboard." Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/2348.
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Chagnon-Lessard, Noémie. "Maximizing power output of heat engines through design optimization : Geothermal power plants and novel exhaust heat recovery systems." Doctoral thesis, Université Laval, 2020. http://hdl.handle.net/20.500.11794/38297.
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Le design de machines thermiques menant à une puissance maximale dépend souvent des températures de la source chaude et de la source froide. C’est pourquoi dégager des lignes directrices à partir des designs optimaux de ces machines selon diverses températures d’opération peut faciliter leur conception. Une telle étude est proposée par cette thèse pour deux types de systèmes thermiques. En premier lieu, le cycle de Rankine organique (ORC) est un cycle thermodynamique de puissance utilisé entre autres dans les centrales géothermiques exploitant des réservoirs à basse température. Depuis quelques années, ce type de centrales suscite un vif intérêt à travers le monde, étant un des modes de production de puissance parmi les plus respectueux de l’environnement. Il s’agit de pomper un géofluide du sol pour transférer sa chaleur à un fluide de travail qui opère en cycle fermé, et de le réinjecter ensuite dans le bassin géologique. Les chercheurs tentent actuellement de mieux caractériser le potentiel géothermique de divers environnements géologiques. Le sous-sol du Québec est relativement froid, alors des études essaient de déterminer s’il serait possible d’y exploiter de manière rentable des centrales géothermiques. Une autre question de recherche importante est de savoir, pour un contexte donné, quel est le design optimal d’une centrale géothermique et quelle est la puissance que l’on peut espérer produire. Pour répondre à cette question, les cycles de Rankine organiques de base (de type souscritique ou transcritique) sont dans un premier temps simulés et optimisés pour des températures du géofluide de 80 à 180°C et pour des températures de condensation du fluide de travail de 0.1 à 50°C. Trente-six (36) fluides pures sont investigués pour toutes les combinaisons de températures. Par la suite, des cycles de Rankine organiques plus avancés sont aussi investigués (ajout d’une tour de refroidissement, d’un système de récupération, et d’une contrainte sur la température de réinjection du géofluide). Les ORCs avec deux pressions de chauffage souscritique et transcritique sont aussi simulés et optimisés. Les optimisations sont faites pour 20 fluides de travail selon la même plage de température du géofluide et selon des températures du thermomètre mouillé de l’air ambient de 10 à 32°C. En second lieu, le cycle de Brayton inversé (IBC) est un cycle thermodynamique qui pourrait être utilisé comme système de récupération de la chaleur perdue dans les gaz d’échappement de moteurs. Il s’agit d’un cycle ouvert comprenant dans sa configuration de base une turbine à gaz, un échangeur de chaleur et un compresseur. Il existe une configuration où l’eau qui se condense lors du refroidissement des gaz est évacuée avant le compresseur pour réduire le débit massique et améliorer le rendement global du système. Le Powertrain and Vehicle Research Centre (PVRC) de l’University of Bath s’est intéressé à savoir si certaines variantes de l’IBC découlant de cette configuration seraient des options viables. Ces variantes ont mené à la création de trois nouveaux cycles thermodynamiques couplant l’IBC avec (i) une turbine à vapeur, (ii) un cycle de réfrigération, et (iii) ces deux ajouts. En comptant les deux cycles déjà existants décrits au paragraphe précédent, cinq configurations de l’IBC sont simulées et optimisées pour des températures de gaz d’échappement de 600 à 1200 K et températures de la source froide de 280 à 340 K. La finalité de cette thèse est d’offrir un outil aidant les ingénieurs à concevoir les systèmes introduits précédemment (ORC et IBC) de sorte qu’ils aient un travail spécifique net maximisé. Sous forme d’un ensemble de diagrammes, cet outil peut ainsi être utilisé pour une large plage de température de la source chaude (géofluide ou gaz d’échappement) et de température de la source froide.Heat engines design leading to maximum power output often depends on the hot source temperature and the cold source temperature. This is why drawing guidelines from optimal designs of these machines according to diverse operating temperatures may facilitate their conception. Such a study is proposed by this thesis for two types of heat engines. In the first instance, the Organic Rankine Cycle (ORC) is a power thermodynamic cycle used among others in geothermal power plants exploiting low-temperature reservoirs. This type of power plants raises keen interest around the world for being one the most environmentally friendly power production modes. In these power plants, a geofluid is pumped from the ground to transfer its heat to a working fluid operating in a closed cycle. The geofluid is then reinjected in the geological basin. Researchers are currently attempting to characterize in a better way the geothermal potential of diverse geological environments. Considering the province of Québec’s relatively cold underground, studies try to determinate whether it is possible to profitably operate geothermal power plants. Another important research question is to determine, for a given context, the optimal geothermal power plant design, and the amount of power that could be generated. To answer this question, Organic Rankine Cycles (subcritical and transcritical) are first simulated and optimized for geofluid temperatures from 80 to 180°C and for condensing temperatures of the working fluid from 0.1 to 50°C. Thirty-six (36) pure fluids are investigated for each temperature combination. Next, cycles models are improved by adding a cooling tower, a recuperative system and a constraint on the minimum reinjection temperature. ORCs with dual-pressure heater are simulated and optimized as well. Optimization runs are performed considering 20 working fluids for the same range of geofluid temperature and for ambient air wet bulb temperature from 10 to 32°C. In the second instance, the Inverted Brayton Cycle (IBC) is a thermodynamic cycle that could be used as a waste heat recovery system for engines exhaust gases. This is an open cycle which includes a gas turbine, a heat exchanger and a compressor as a basic layout. There is a configuration where the water condensed during the cooling of the gases is evacuated upstream of the compressor in order to reduce the mass flow rate and improve the system global efficiency. The Powertrain and Vehicle Research Centre (PVRC) of the University of Bath is interested in finding out whether particular IBC variants arising from this configuration could be viable options. These variants led to the creation of three novel thermodynamic cycles that couple the IBC with (i) a steam turbine, (ii) a refrigeration cycle, and (iii) both additions. Including both already existing cycles described in the preceding paragraph, five IBC layouts are simulated and optimized for exhaust gases temperatures from 600 to 1200 K and for heat sink temperatures from 280 to 340 K. The purpose of this thesis is to offer a tool that help engineers designing the systems previously introduced (ORC and IBC), so that they produced a maximized specific work output. As a set of charts, this tool can be used for a large range of hot source temperature (geofluid or exhaust gases) and of heat sink temperature.
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Midtsjø, Alexander. "Power Production from Low Temperature Heat Sources." Thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9902.
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As part of the energy recovery part of the ROMA (Resource Optimization and recovery in the Materials industry) project, a laboratory prototype power production system is being built and completed in 2009. The laboratory prototype is based on a new technology for power production from low to medium temperature heat sources (the off gas from electrolysis cells in the aluminum industry) where CO2 is used as a working medium in a trans-critical Rankine cycle. The laboratory rig consists of the power cycle with a prototype expander as the core unit, an air loop to provide the heat, and an ethylene glycol loop to provide condensation of the working fluid in the power cycle. As a preparation to the assembling and instrumentation of the prototype rig, a simulation and an uncertainty analysis were conducted for the prototype rig in the autumn of 2008. This report focuses on the continuation of that work by an experimental investigation of the individual loops and the components of the prototype rig. The emphasis of this investigation has been put on the air loop and the expander unit of the power cycle. This is basically because these are of great importance to the performance of the power production prototype rig. The air loop was thoroughly tested, and from the investigations it was discovered that there was an unfavorable temperature distribution of the air going into the air-to-CO2 heat exchanger. This is the heat exchanger where heat is provided to the power cycle. The source for this temperature maldistribution was identified, and solutions were investigated to improve on the problem without results. The reduced performance of the air loop was incorporated in a new simulation of the power cycle in order to quantify the consequences for the optimization of the power cycle. The simulation was carried out for warm air temperature of 80 °C. The new calculations showed a reduction in maximum net work output of 27 % compared to the original simulation. The optimal conditions for the power cycle were also changed as a consequence of the reduced air loop performance. The investigation of the expander unit revealed that the expander isentropic efficiency was a strong function of the pressure difference across the expander, and a weak function of the expander inlet pressure. It also revealed that overall the isentropic efficiency was much less than the value of 80 % which was used in the original simulation. A new simulation of the power cycle was carried out where the expander isentropic efficiency was incorporated as a function of the pressure difference across the expander. This function was based on the data from the expander testing. The simulation showed a reduction in maximum net work output from 225 W to about 60 W, for warm air temperature of 80 °C. The new expander characteristics also affected the optimization of the power cycle. The simulation results and the results from the prototype investigation will be important in the optimization and control procedures of the assembled prototype power production system.
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Pfaff, Michael. "Power Production from Low Temperature Heat Sources." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18330.
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SummaryThis Master Thesis is a conclusion on work done as part of the Resource Optimizationand recovery in the Materials industry project (Roma). This project is involved in thedevelopment of a new technology for power production from low temperature heat sourcesfor off gases from aluminum production cells. The technology is based on an transcriticalRankine cycle with CO2 as a working fluid, as the work recovery circuit. The center ofthe test facility is the expander, a prototype provided by Obrist Engineering . 81 testswere perfomed to investigate the behavoir of the expander cycle. Effect of three mainparameters were investigated:• Effect CO2 massflow rate• Effect of heat source temperature• Effect of CO2 condensation pressureFor each parameter combination, the high pressure side of the expander cycle was variedin order to find the maximum power output.This study clearly showed limitation of the turbine which cannot maintain large pressuredifference probably due to large internal leakages. As a result, turbine outlet is highlysuperheated. This superheat is lost energy for the power cycle, and is simply dumpedinto the heat sink. One possible improvement would be to include a recuperator thatrecovers superheat after the pump.The results also indicate that the fan of the air loop is too small: increasing the CO2 flowrate to limit superheat at turbine outlet leads to turbine inlet temperature reduction.Last, for large CO2 mass flow rate (3.5 kgmin) which is required for proper operation ofthe turbine, the power generated is too large for the generator installed on the loop. Itstemperature reached 120 °C for some conditions. A new solution should be seeked.Based on experimental results, a mode of the power cycle was implemented in Pro/IIand simulations were run in order to find an improved design. The main goal is to beable to run the cycle at high CO2 mass flow rate: 3.5 kgmin. It was found that the airloop fan should be able to deliver up to 1 260 m3h . The new generator or braking systemshould be able to absorb up to 297 W.
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Colella, W. G. "Combined heat and power fuel cell systems." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411153.
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Starfelt, Fredrik. "From Combined Heat and Power to Polygeneration." Doctoral thesis, Mälardalens högskola, Framtidens energi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-28442.
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In order to reach targets on reducing greenhouse gas emissions from fossil resources it is necessary to reduce energy losses in production processes. In polygeneration, several processes are combined to complement each other to avoid sub-optimization of the standalone processes. This thesis addresses polygeneration with focus on Combined Heat and Power (CHP) production integrated with other processes. Biomass-fired CHP plants are commonly dimensioned to have surplus heat production capacity during periods with lower heat demand. At the same time, production of biomass based vehicle fuels and fuel upgrading are heat demanding processes. The opportunity to combine CHP with ethanol production from lignocellulosic feedstock and torrefaction with the aim of replacing fossil fuels are used as cases during the evaluation of polygeneration. Simulation models are used to investigate the performance of CHP integrated with production of ethanol and torrefaction. Measured data from commercial CHP plants have been used to reflect the operation boundaries. The findings show that polygeneration can compete with stand-alone production in both energy and economic performance. Polygeneration offers a wider operating range where reduced minimum load gives increased annual operating time. Therefore, under limited heat demand more renewable electricity production is possible due to increased operating hours and steam extraction from the turbine during part-load operation. Resource availability and fluctuations in fuel price have the largest impact on the profit of polygeneration. Other aspects that have substantial effects on the economy in polygeneration are the electricity spot price and subsidies. Furthermore, it has been proven that the yield of each product in a multiproduct process plant, the size of the plant and the heat demand have a large impact on the economy. Polygeneration turns by-products into buy-products.
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McCance, Gavin John. "Event shapes and power corrections at HERA." Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342040.
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Gibbons, Jonathan S. (Jonathan Scott) 1979, and Stephen V. 1982 Samouhos. "Mobile power plants : waste body heat recovery." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32814.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references.
Novel methods to convert waste metabolic heat into useful and useable amounts of electricity were studied. Thermoelectric, magneto hydrodynamic, and piezo-electric energy conversions at the desired scope were evaluated to understand their role and utility in the efficient conversion of waste body heat. The piezo-electric generator holds the most promise for the efficient conversion of waste body heat into electricity. In the future, this same device could be easily extended into a combustion based power plant. An experimental apparatus investigating the use of magneto hydrodynamics was designed, built, and tested. A room temperature liquid inetal was propelled through a magneto hydrodynamic channel of 4 inches by 0.1875 inches at a rate of 10 mL/s. A 2 T induction field was applied within the channel. However, the results of the analysis did not find the magneto hydrodynamic device to be an effective electric generator at the scale tested.
by Jonathan S. Gibbons and Stephen V. Samouhos.
S.B.
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Binder, Felix Christoph. "Work, heat, and power of quantum processes." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:279871ea-3b2e-4baf-975c-1bd42b4961c3.
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The central purpose of this thesis is to study the familiar processes of quantum information theory from a thermodynamic point of view. Chapter 1 introduces equilibrium thermodynamics and its laws. The laws are then motivated in a statistical mechanics approach which explicitly employs the language of quantum information theory. Chapter 2 is dedicated to the concept of work extraction, in particular in non- equilibrium scenarios. In this context a generalised notion of equilibrium called passivity is introduced. The chapter's final section gives an introduction and an overview of various approaches to work extraction ranging from classical to explicitly quantum scenarios. Chapter 3 considers the question of powerful unitary operations. Focussing on the case of qubits (or rather wits, short for 'work bits') the chapter's first result is an explicit protocol for maximally powerful driving for any given initial state. Building onto this, the chapter's second main result is a proof that the evolution time (and hence the power of the corresponding work deposition process) can be decreased by a factor of 1/N for an array of N wits if global driving is permitted (rather than individual driving in parallel). Lastly, the thermodynamics of completely-positive and trace-preserving (CPTP) maps is considered in Chapter 4. It is shown that the energy change during such a process can be split into three parts: a work-like equilibrium contribution, a heat-like equilibrium contribution, and a third genuinely non-equilibrium energy difference. All three terms obtain their meaning when considering how much work can be extracted from the input and output state of the CPTP process, respectively. Furthermore, the identification of work and heat in this manner complies with a recently published version of the second law, which applies to the same class of processes. This is demonstrated by considering unital and thermal maps.
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Hu, Shih-Yung. "Heat transfer enhancement in thermoelectric power generation." [Ames, Iowa : Iowa State University], 2009.
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Nicholas, Jack Robert. "Heat transfer for fusion power plant divertors." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:efedf39b-401b-418f-b510-386a512314a8.
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Exhausting the thermal power from a fusion tokamak is a critical engineering challenge. The life of components designed for these conditions has a strong influence on the availability of the machine. For a fusion power plant this dependence becomes increasingly important, as it will influence the cost of electricity. The most extreme thermal loading for a fusion power plant will occur in the divertor region, where components will be expected to survive heat fluxes in excess of 10 MW/m2 over a number of years. This research focussed on the development of a heat sink module for operation under such conditions, drawing on advanced cooling strategies from the aerospace industry. A reference concept was developed using conjugate Computational Fluid Dynamics. The results were experimentally validated by matching Reynolds numbers on a scaled model. Heat transfer data was captured using a transient thermochromic liquid crystal technique. The results showed excellent agreement with the corresponding numerical simulations. To facilitate comparison against other divertor heat sink proposals, a nondimensional figure of merit for cooling performance was developed. When plotted against a non-dimensional mass flow rate, the reference heat sink was shown to have superior cooling performance to all other divertor proposals to date. Results from Finite Element Analysis were used in conjunction with the ITER structural design criteria to life the heat sink. The sensitivity of life to both boundary conditions, and local geometric features, were explored. The reference design was shown to be capable of exceeding the life requirements for heat fluxes in excess of 15 MW/m2. A number of heat sinks, based on the reference design, were fabricated. These underwent non-destructive testing, before experimentation in a high-heat flux facility developed by the author. The heat transfer performance of the tested modules was found to exceed that predicted by numerical modelling, which was concluded to be caused by the fabrication processes used.
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Harnoto, Monica. "Value of distribution-level reactive power for combined heat and power systems." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/126901.
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Thesis: M.B.A., Massachusetts Institute of Technology, Sloan School of Management, in conjunction with the Leaders for Global Operations Program at MIT, May, 2020Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, in conjunction with the Leaders for Global Operations Program at MIT, May, 2020
Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 56-59).
As the U.S. electric grid continues to experience an increase in the penetration of distributed energy resources (DER), electric utilities are evaluating new approaches for utilizing DER to help cost-effectively maintain grid resilience and reliability. One such approach is to create a transactive market for DER to provide grid services, which are services required to support reliable grid operation. Though work has been done to understand some of the technical mechanisms of this type of market, gaps still exist in understanding the value and market opportunity of ancillary services at the distribution level. One type of ancillary service - reactive power - is of particular interest because of the theoretic ability to source from existing assets on the distribution network. This paper aims to build understanding of the value of procuring reactive power from one of these assets: Combined Heat and Power (CHP) systems. The value of procuring reactive power from a CHP system will be quantified by 1) characterizing CHP systems' capacity to produce and absorb reactive power, 2) assessing the annual cost of procuring reactive power from CHP systems, and 3) comparing the CHP system technical capability and cost to the utility's conventional solution: capacitor banks. This study finds that, while there are promising scenarios in which CHP systems can technically and economically provide reactive power in a comparable or slightly advantaged manner to capacitor banks, the overall statistics for the 29 CHP systems analyzed in the New York fleet do not conclusively demonstrate an advantage that supports outright replacement of capacitor banks. Further assessment of CHP systems as a complementary source of reactive power and site-specific case studies are recommended to inform the next step in the decision making process for determining whether this path should be pursued as a source of reactive power.
by Monica Harnoto.
M.B.A.
S.M.
M.B.A. Massachusetts Institute of Technology, Sloan School of Management
S.M. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering
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Wright, Michele E. "Power suits her : an arts-based portrayal of women and power." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79813.
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This arts-based study examines how three women, who hold senior positions in development organizations, perceive of power. Emphasis is placed not only on how the participants describe their power identities, but also on how those identities can be portrayed. Based on data collected in interviews and drawing on the metaphors of portraiture, the power suit and the feminist conception of "voice", the women's power identities are represented in three ways: textually (in the form of "power identity profiles"), visually (in the form of "power suit" costume designs) and aurally (in the form of dramatic monologues). Through notes, descriptions, outlines and explanations the entire process of this aesthetic/interpretive inquiry is documented.While not being offered as a generalizable or even representative sample, the three women in this study illustrate the importance of diverse, individualized inquiry approaches in order to appreciate and represent the nuance and contradiction inherent to women's thoughts and feelings about power.
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Souza, Anderson Alves de. "Mortals, hear the sacred cry." Florianópolis, SC, 2003. http://repositorio.ufsc.br/xmlui/handle/123456789/85670.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão. Programa de Pós-Graduação em Letras/Inglês e Literatura Correspondente.Made available in DSpace on 2012-10-20T21:25:25Z (GMT). No. of bitstreams: 0
Os símbolos nacionais e, mais especificamente, os hinos nacionais desempenham um papel importante nas lutas pela manutenção e disputa do poder político nas sociedades. Entretanto, poucos estudos têm sido realizados a respeito da natureza, funções e características dos hinos nacionais. Além disso, a maioria do material sobre hinos nacionais limita-se a publicações que trazem apenas as letras e os nomes dos autores dos hinos. Nesta dissertação, eu investigo 9 hinos nacionais sob a perspectiva da Análise Crítica do Discurso (Fairclough, 1989) e da Gramática Sistêmica Funcional (Halliday 1978, 1989, 1994). Os hinos analisados foram sub-divididos em 3 grupos: a) monárquicos, b) revolucionários, e c) hinos de consolidação. Os resultados sugerem que (i) os hinos monárquicos refletem a tentativa dos Monarcas de permanecerem no poder através de uma caracterização positiva que objetiva representa-los como seres humanos especiais, principalmente na posição de Meta e Beneficiários; (ii) os hinos revolucionários refletem a tentativa de um grupo de conquistar o poder exortando os cidadãos à luta e representando-os na posição de Atores, Portadores, Identificados, e Possuidores; e (iii) os hinos de consolidação refletem a fase pós-conquista do poder através da representação de elementos simbólicos tais como países e bandeiras na posição de Atores, Portadores, Identificados, e Possuidores. Além disso, os hinos nacionais trazem em sua estrutura os quatro elementos exortativos (Longacre, 1992) que os permitem serem classificados como um tipo de discurso exortativo. A importância deste trabalho reside no fato de que o mesmo contribui para uma melhor compreensão de como as lutas pelo poder político moldam a produção dos hinos nacionais e como os detentores de poder e os cidadãos são representados neste processo.
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Su, Yu-Hao. "Power Enhancement of Piezoelectric Technology based Power Devices by Using Heat Transfer Technology." Thesis, Cachan, Ecole normale supérieure, 2014. http://www.theses.fr/2014DENS0025/document.
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L’objectif de cette étude est d’améliorer les performances des transformateurs piézoélectriques en terme de courant de sortie et de puissance pour des applications d’alimentation DC/DC, grâce à la gestion de l’échauffement. Le courant de sortie des transformateurs piézoélectriques, et donc la puissance transmise, sont directement liés à la vitesse de vibration qui pour des valeurs élevées engendre des pertes et une forte élévation de température. Cette élévation excessive de la température a comme conséquence le changement des caractéristiques du transformateur et plus particulièrement la diminution du facteur de qualité Q. Ainsi cela entraine une limite structurelle de la puissance transmise du transformateur. Une solution pour augmenter le courant de sortie est l’utilisation d’un redresseur doubleur de courant, qui grâce à 2 inductances permet, à courant de charge donné, de diminuer la vitesse de vibration du transformateur, mais ne permet pas de régler le problème d’échauffement du transformateur. Dans cette thèse nous proposons des moyens d’évacuation de la chaleur ainsi que le choix de l’environnement dans lequel le transformateur devra fonctionner. L’influence de différents systèmes de refroidissement d’un convertisseur DC/DC à base transformateur piézoélectrique est étudiée. L’étude thermique du transformateur piézoélectrique multicouche polarisé en épaisseur et ayant des électrodes circulaires met en évidence un comportement non linéaire. Une plaque vibrante piézoélectrique est d’abord envisagée pour créer un flux d’air qui augmente l’évacuation de chaleur par convection, puis un module de refroidissement utilisant l’effet thermoélectrique. Les mesures montrent que la première solution est plus avantageuse car elle améliore sensiblement les performances du transformateur pour un coût énergétique très faible. Une étude thermique par éléments finis complète cette étude, montrant que l’approche par schéma électrique est pertinente. La puissance que peut délivrer le transformateur sur une charge optimale est encore augmentée. Enfin, ce travail montre qu’en combinant les dispositifs de refroidissement tout en respectant la condition de température inférieure à 55°C, le rendement du convertisseur reste raisonnable (70%) et la puissance disponible peut doubler dans le meilleur des casThe objective of this study was to increase the output current and power in a piezoelectric transformer (PT) based DC/DC converter by adding a cooling system. It is known that the output current of PT is limited by temperature build-up because of losses especially when driving at high vibration velocity. Excessive temperature rise will decrease the quality factor Q of piezoelectric component during the operational process. Simultaneously the vibration energy cannot be increased even if under higher excitation voltage. Although connecting different inductive circuits at the PT secondary terminal can increase the output current, the root cause of temperature build-up problem is not solved.This dissertation presents the heat transfer technology to deal with the temperature build-up problem. With the heat transfer technology, the threshold vibration velocity of PT can be increased and thus the output current and output power (almost three times).Furthermore, a comparison between heat transfer technology and current-doubler rectifier applied to the piezoelectric transformer based DC/DC converter was also studied. The advantages and disadvantages of the proposed technique were investigated. A theoretical-phenomenological model was developed to explain the relationship between the losses and the temperature rise. It will be shown that the vibration velocity as well as the heat generation increases the losses. In our design, the maximum output current capacity can increase 100% when the operating condition of PT temperature is kept below 55°C. The study comprises of a theoretical part and experimental proof-of-concept demonstration of the proposed design method
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Ramdal, Jørgen. "Efficiency measurements in low head hydro power plants." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14578.
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The work presented in this thesis involves efficiency measurements performed with thethermodynamic method and the pressure time method. The thermodynamic method haslimitations with regards to the power plant head, as uncertainty will increase as the headbecomes low. The Pressure-Time method has limitations concerning geometrical propertiesof the waterways, as it demands a certain length of closed conduit with uniform area. Bothmethods are considered to cause relatively short downtime for turbines to be measured, andit is therefore of interest, for economical reasons, to expand the use of the methods to morepower plants. In the thermodynamic method, a large source of errors and uncertainties comes from flowand temperature variations in the draft tube outlet. To investigate if this source of errors anduncertainties could be reduced, a setup with multipoint temperature and velocitymeasurements was installed in a low head hydro power plant. The general conclusion is thata multipoint measurement is beneficial in connection with low head measurements.Uncertainty from temperature variations in the water from the reservoir, and difference inthe energy at the inlet is also discussed. For the Pressure-Time method, this thesis presents investigations made with shorterdistances between measurement cross sections than prescribed in the standards, and withbends between the measurement cross sections. The investigations were performed both inlaboratory and in a field measurement. For laboratory experiments it was also investigated ifdeveloped models for unsteady friction could be used to correct the flow estimates. Thegeneral conclusions are: Measurements with short distances should not introduce large errors, but theuncertainty and spread of measured points will increase. Bends give an underestimation of the flow rate that, under certain circumstances, isconstant independent of initial velocity. How large the underestimation ratio willbe can yet not be predicted. Introducing unsteady friction in the Pressure-Time calculations improves the flowestimate. However, the results are not fully satisfactorily, and more work has to bedone to investigate the correction due to unsteady friction.
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Blanquart, Fanny. "Perspectives for Power Generation fromIndustrial Waste Heat Recovery." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-215985.
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Bong-Toh, Mei Choo Aileen. "Fictions of power : the novels of Bessie Head." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59862.
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Bessie Head's fiction reflects the author's consciousness of power as the definitive force in the South African context. By considering Head as a social realist, the thesis relates sociological evidence to authorial interest and demonstrates Head's treatment of the power issue in her three novels, When Rain Clouds Gather, Maru, and A Question of Power. Biographical data, particularly Head's unique, though socially marginal position as a political exile, a Coloured, and a woman are also applied. The thesis covers three areas--politics, race, and gender. The first explores the nature of power in South African politics within the time-frame of the present, past, and future. The second which focuses on the institution of apartheid examines racial relations between the blacks and whites and also among the blacks, with attention given to the dilemma of the Coloured. The third section discusses sexual politics, looking at male-female relationships in both traditional and contemporary societies.
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Smith, Martin Alan. "Small scale and micro combined heat and power." Thesis, De Montfort University, 1999. http://hdl.handle.net/2086/4178.
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Perez-Davis, Marla Esther. "Heat receivers for solar dynamic space power systems." Case Western Reserve University School of Graduate Studies / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1055525095.
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Feng, Xin. "Experimental and analytical study on two-phase impingement cooling with and without electric field." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4853.
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Thesis (Ph.D.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 10, 2009) Includes bibliographical references.
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Nordahl, Kristina. "Authentic Authority: The Heart of Effective Teaching." Thesis, Malmö högskola, Lärarutbildningen (LUT), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-29795.
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The purpose of this thesis paper is to explore the elements of effective teaching. The main research questions that are dealt with regard how teachers can establish themselves as authentic authorities in the classroom and what strategies are conducive to effective teaching. The thesis paper aims to identify specific strategies and techniques that can be employed to increase teachers’ authority and provide a learning environment conducive to cooperative, on-task learning.This investigation will be in the form of a case study of an eighth grade English teacher at a secondary school in southern Sweden. The case study consists of two parts: an in-class observation of six English lessons forms the basis for a follow-up semi-structured interview.This thesis highlights the importance of teachers’ ability to establish referent and expert authority in their teaching role.
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Faka, Marianthi. "Heat stability of skim milk powder." Thesis, University of Reading, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499360.
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Skim milk powder (SMP) is a widely used commodity in the food industry; hence its physical and chemical characteristics should be controlled for ensuring the successful functionality of the powder in the end product. An important characteristic of SMP is its heat stability. The current study involved a thorough examination of heat stability and other characteristics of low-heat and high-heat SMP. The main differences between these two powders were related to a lower pH, smaller particle size and a lower level of denatured whey proteins in the low-heat SMP.
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Engelke, Kylan Wynn. "Novel thermoelectric generator for stationary power waste heat recovery." Thesis, Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/engelke/EngelkeK0510.pdf.
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Internal combustion engines produce much excess heat that is vented to the atmosphere through the exhaust fluid. Use of solid-state thermoelectric (TE) energy conversion technology is a promising technique to recapture some of the energy lost. The TE effect, discovered in 1821 by Thomas Seebeck, is essentially the solid-state conversion of a temperature gradient into an electric potential. The scope of this work was the design, testing and evaluation of a novel and robust TE generator that is amendable to use in a vast array of convective thermal processes. Seebeck testing of TE elements was combined with thermal/hydraulic and thermoelectric modeling to develop the design of a working prototype system. A proof-of-concept small-scale prototype (SSP) TE generator was built to evaluate concepts intended for the construction of a fully-functional field demonstration prototype (FDP). The SSP was used to evaluate electrical contact integrity, thermal characteristics, various TE materials and the feasibility of using compression-based TE contacts. The SSP featured 9 P/N TE pairs and has thus far produced a maximum open-circuit voltage of 380mV and a maximum electrical power of 1.47W. Knowledge gained from the SSP construction and testing was utilized in the design and fabrication of the FDP. A liquid-cooled Honda ES6500 6.0kW genset was procured to provide a test-bed for the FDP. The primary goal was to power the electric radiator fan with the heat energy contained in its exhaust, thus decreasing the genset's fuel consumption rate. The FDP contained 256 P/N pairs and thus far has produced an open-circuit voltage of 5.5VDC and a maximum power of 8.49W. Replacing the stock muffler reduced fuel consumption by 11.6% whereas removing the fan load reduced it an additional 1.64%. Through the recovery and conversion of wasted thermal energy, the genset's fuel consumption rate was successfully lowered, therefore validating the benefits of secondary TE power systems. The radiator fan of the Honda ES6500 consumes approximately 1% of the overall power output of the genset. Radiator fans in larger gensets can draw as much as 12-16% of their peak output. By recuperating waste heat, substantially higher fuel savings could be achieved.
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Cole, David Graham. "Design of heat-resistant steels for small power plant." Thesis, University of Cambridge, 2000. https://www.repository.cam.ac.uk/handle/1810/219196.
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Yakah, Noah. "Heat Exchanger Design for Solar Gas-Turbine Power Plant." Thesis, KTH, Energiteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-107277.
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The aim of this project is to select appropriate heat exchangers out of available gas-gas heat exchangers for used in a proposed power plant. The heat exchangers are to be used in the power plant for the purposes of waste heat recovery, recuperation and intercooling.In selecting an optimum heat exchanger for use, the PCHE was identified as the best candidate for waste heat recovery and recuperation. In order to ascertain the viability of this assertion the PCHE was designed and a 1D modeling performed in MATLAB using the conditions that the heat exchanger for waste heat recovery would be subjected to. The choice of using the conditions that the waste recovery heat exchanger would be subjected to was due to the fact that, it is the heat exchanger that would be subjected to much harsh conditions (thus higher temperatures of up to 650 ºC). The PFHE was also designed and similarly a 1D modeling performed in MATLAB. The decision to consider the design of the PFHE was to offer a platform to compare and contrast the performance of the PCHE in order to have a strong basis for deciding on whether to stick to the choice for the PCHE or otherwise.The results obtained from the 1D modeling of the design of the heat exchangers indicates that the PCHE performed better with regards to pressure drops across the heat exchangers (with values of 1.17 and 2.47 % for the cold and hot sides respectively), compactness (with a value of 1300 m2/m3 for the PCHE compared to the 855 m2/m3 recorded from the PFHE), however the PFHE recorded higher heat transfer coefficients, and a subsequent higher overall transfer coefficient.Results obtained from the simulation of the 3D model buttress the decision to employ the PCHE as heat exchangers to be used for waste heat recovery and recuperation as a wise one, with an effectiveness of 0.94 as against the design value of 0.90, and with pressure drops as desired of the optimum heat exchanger.
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Burzynski, Katherine Morris. "Printed Nanocomposite Heat Sinks for High-Power, Flexible Electronics." University of Dayton / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1619702252056433.
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Rajasekeran, Sangeetha. "Enabling Grid Integration of Combined Heat and Power Plants." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99730.
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In a world where calls for climate action grow louder by the day, the role of renewable energy and energy efficient generation sources has become extremely important. One such energy efficient resource that can increase the penetration of renewable energy into the grid is the Combined Heat and Power technology. Combined Heat and Power (CHP) plants produce useful thermal and electrical power output from a single input fuel source and are widely used in the industrial and commercial sectors for reliable on-site power production. However, several unfavorable policies combined with inconsistent regulations have discouraged investments in this technology and reduced participation of such facilities in grid operations. The potential benefits that could be offered by this technology are numerous - improving grid resiliency during emergencies, deferring transmission system updates and reducing toxic emissions, to name a few. With increased share of renewable energy sources in the generation mix, there is a pressing need for reliable base generation that can meet the grid requirements without contributing negatively to the environment. Since CHP units are good candidates to help achieve this two-fold requirement, it is important to understand the present barriers to their deployment and grid involvement. In this thesis work, we explore some of these challenges and propose suitable grid integration technology as well as market participation approaches for better involvement of distributed CHP units in the industrial and commercial sectors.Master of Science
Combined Heat and Power is a generation technology which uses a single fuel source to produce two useful outputs - electric power and thermal energy - by capturing and reusing the exhaust steam by-product. These generating units have much higher efficiencies than conventional power plants, lower fuel emissions and have been a popular choice among several industries and commercial buildings with a need for uninterrupted heat and power. With increasing calls for climate action and large scale deployment of renewable based energy generation sources, there is a higher need for reliable base-line generation which can handle the fluctuations and uncertainty of such renewables. This need can be met by CHP units owing to their geographic distribution and their high operating duration. CHPs also provide a myriad of other benefits for the grid operators and environmental benefits, compared to the conventional generators. However, unfavorable and inconsistent regulatory procedures have discouraged these facility owners from actively engaging in providing grid services. Therefore, it is imperative to look into some of the existing policies and understand where the changes and incentives need to be made. In this work, we look into methods that can ease CHP integration from a technological and an economic point of view, with the aim of encouraging grid operators and CHP owners to be more active participants.
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Boltyanskiy, Boris. "Operation of the heat and power complex Alatyr to power Russian oil and gas facilities." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-264245.
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B. Boltyansky Operation of the heat and power complex Alatyr to power Russian oil and gas facilities, Master's Dissertation, 2017 - 102 pages, 26 tables, 30 figures Supervisor Prof. V. G. Kucherov, Doctor of Sciences, Department of Energy Technology. The work includes the following. A calculation of the main thermodynamic cycle of the heat and power complex Alatyr heat and power complex. A consideration of various schemes of using the Rankine organic cycle WERE integrated in the Alatyr heat and power complex with the aim of increasing energy efficiency. Conclusions about the feasibility of using the heat and power complex Alatyr. Conclusions about the feasibility of integration of the organic Rankine cycle. Economic comparison of the heat and power complex Alatyr with similar facilities on the distributed power generation market. Economic analysis of the comparison of energy blocks of HPC Alatyr with similar designs from other countries.B. Boltyansky Drift av värme- och kraftkomplexet Alatyr till makten Ryska olje- och gasanläggningar, Masters uppläggning, 2017 - 102 sidor, 26 tabeller, 30 figurer Handledare Prof. VG Kucherov, doktorsexamen, kandidatexamen för teknisk vetenskap, institutionen för termodynamik och termisk motorer. Arbetet innehåller följande. En beräkning av värmekraftkomplexets värmeoch kraftkomplex Alatyrs värmekomplex. En övervägning av olika system för användning av Rankine organiska cykeln var integrerad i Alatyr värme- och kraftkomplexet i syfte att öka energieffektiviteten. Slutsatser om möjligheten att använda värme- och kraftkomplexet Alatyr. Slutsatser om möjligheten att integrera den organiska Rankine-cykeln. Ekonomisk jämförelse av värme- och kraftkomplexet Alatyr med liknande anläggningar på den distribuerade kraftproduktionsmarknaden. Ekonomisk analys av jämförelsen av energiblock av HPC Alatyr med liknande konstruktioner från andra länder.
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Яковлева, Ирина Геннадиевна, Ірина Геннадієвна Яковлєва, Irina Yakovleva, Алексей Анатольевич Петрик, Олексій Анатолійович Петрик, and Alexey Petrik. "Общая характеристика и особенности дутьевых устройств для верхней продувки ванны сталеплавильного агрегата кислородом." ЗДІА, 2017. https://dspace.znu.edu.ua/jspui/handle/12345/487.
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RU : Выполнен анализ литературных источников в части конструктивных особенностей дутьевых устройств
для продувки ванны сталеплавильных агрегатов кислородом. Установлено отсутствие однозначных
рекомендаций относительно выбора конструкции и оптимального расхода кислорода, подаваемого на
продувку и дожигание оксида углерода, выделяемого из ванны сталеплавильного агрегата. Анализ
указывает на необходимость разработки новых конструктивных решений кислородных фурм, которые
позволят сочетать достоинства известных конструкций и повысить эффективность дожигания отходящих газов в полости сталеплавильного агрегата с улучшением теплового баланса плавки применительно к реальным производственным условиям.UA : Виконано аналіз літературних джерел в частині конструктивних особливостей дуттьових пристроїв для продування ванни сталеплавильних агрегатів киснем. Встановлена відсутність однозначних рекомендацій щодо вибирання конструкції та оптимальної витрати кисню, якого подають на продування та допалювання монооксиду вуглецю, що виділяється з ванни сталеплавильного агрегату. Аналіз вказує на необхідність розробки нових конструктивних вирішень кисневих фурм, які дозволять поєднувати переваги відомих конструкцій та підвищити ефективність допалювання газів у порожнині сталеплавильного агрегату з поліпшенням теплового балансу плавки відповідно до реальних виробничих умов.
EN : To analyze the literature in conditions of the constitutive features of blowing devices for scavenging of bath in steel-smelting aggregate by oxygen. Absence of univalent recommendations in relation to the choice and the optimal consumption and optimal expense of oxygen given on scavenging and after-burning of carbon monoxide distinguished from bath of steel-smelting aggregate is set. An analysis specifies on the necessity of development of new structural solutions for oxygen lances which will allow to combine dignities of the known construction and to promote efficiency of after-burning of carbon monoxide in the cavity of steel-smelting aggregate with improvement of heat balance of melting as it applies to the real productive conditions.
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Boyes, Haydn. "Sensitivity analysis of the secondary heat balance at Koeberg Nuclear Power Station." Master's thesis, Faculty of Engineering and the Built Environment, 2021. http://hdl.handle.net/11427/33686.
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At Koeberg Nuclear Power Station, the reactor thermal power limit is one of the most important quantities specified in the operating licence, which is issued to Eskom by the National Nuclear Regulator (NNR). The reactor thermal power is measured using different methodologies, with the most important being the Secondary Heat Balance (SHB) test which has been programmed within the central Koeberg computer and data processing system (KIT). Improved accuracy in the SHB will result in a more accurate representation of the thermal power generated in the core. The input variables have a significant role to play in determining the accuracy of the measured power. The main aim of this thesis is to evaluate the sensitivity of the SHB to the changes in all input variables that are important in the determination of the reactor power. The guidance provided by the Electric Power Research institute (EPRI) is used to determine the sensitivity. To aid with the analysis, the SHB test was duplicated using alternate software. Microsoft Excel VBA and Python were used. This allowed the inputs to be altered so that the sensitivity can be determined. The new inputs included the uncertainties and errors of the instrumentation and measurement systems. The results of these alternate programmes were compared with the official SHB programme. At any power station, thermal efficiency is essential to ensure that the power station can deliver the maximum output power while operating as efficiently as possible. Electricity utilities assign performance criteria to all their stations. At Koeberg, the thermal performance programme is developed to optimize the plant steam cycle performance and focusses on the turbine system. This thesis evaluates the thermal performance programme and turbine performance. The Primary Heat Balance (PHB) test also measures reactor power but uses instrumentation within the reactor core. Due to its location inside the reactor coolant system, the instrumentation used to calculate the PHB is subject to large temperature fluctuations and therefore has an impact on its reliability. To quantify the effects of these fluctuations, the sensitivity of the PHB was determined. The same principle, which was used for the SHB sensitivity analysis, was applied to the PHB. The impact of each instrument on the PHB test result was analysed using MS Excel. The use of the software could be useful in troubleshooting defects in the instrumentation. A sample of previously authorised tests and associated data were used in this thesis. The data for these tests are available from the Koeberg central computer and data processing system.
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Worthington, D. R. E. "The cooling of electronic power supplies by natural convection." Thesis, University of Exeter, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380691.
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Karadag, Rukiye. "Temperature Distribution In Power Transformers." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12615162/index.pdf.
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As in all other electrical equipments it is essential to estimate the temperature distribution in transformer components in the design stage and during the operation since temperatures above thermal limits of these components might seriously damage them. Thermal models are used to predict this vital information prior to actual operations. In this study, a three dimensional model based on the Finite Element Method (FEM) is proposed to estimate the temperature distribution in the three phase, SF6 gas insulated-cooled power transformer. This model can predict the temperature distribution at the specific discredited locations in the transformer successfully.
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Weerasiri, Udayani Priyadarshana. "A waste heat recovery steam power generation system for ACE Power Embilipitiya (Pvt) Ltd, Sri Lanka." Thesis, KTH, Kraft- och värmeteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-157832.
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In this study, the heat recovery from exhaust gas at the ACE Power Embilipitiya (Pvt) Ltd (APE) in Sri Lanka was conceptually proposed and evaluated. APE has an installed capacity of 100 MW comprising 14 units of 7.5MW medium speed diesel engines fired with heavy fuel oil. There is only a minimum recovery of waste heat in the plant at the moment, only for fuel preheating, whereas waste heat recovery (WHR) boilers of 750kWth are equipped on eight engines. The larger portion of the waste heat is dumped into the environment without being used in any reasonable way. The objective of this work was to design a HRSG system for the remaining six engines to recover maximum possible heat from the exhaust gas and select a suitable steam turbine according to the heat demand capacity of the proposed HRSG, for generating additional power and thus converting the APE plant into a sort of a combined cycle. At the initial stage of the investigation, the amount of recoverable waste heat was estimated by evaluating the known parameters of the engines at fully loaded condition. The maximum theoretical waste heat recovery potential from the exhaust gas stream of one engine was calculated as 9807.87 MJ/h, equivalent to a heat rate of 2724.4 kW. The modelling and optimization of the proposed HRSG was done using the Engineering Equation Solver (EES) software, considering technical and practical limitations such as pinch point temperature difference, approach point temperature difference, terminal temperature difference and sulphur dew point in the stack. A commercially available steam turbine with a power output of 3.579 MW was selected as the optimum steam turbine for the desired conditions, utilising 12884.4 MJ/h of recovered waste energy amounting to 21.89% of the total available energy in the flue gas.
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Green, Jeffrey Andrew. "IMPROVING THE ENERGY EFFICIENCY OF A MID-SIZE POWER PLANT BY REDUCTION IN AUXILIARY POWER AND IMPROVED HEAT TRANSFER." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1502.
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This study incorporates the potential use of Variable Frequency Drives on various motors as well as areas of improved heat transfer in an older, mid-sized coal fired power plant. In power plants, fluid flow rates are often controlled using dampers or valves while the motors that power the pumps stay at full speed resulting in a significant amount of wasted electrical power; energy is also lost due to poor heat recovery prior to gases leaving the system. By examining pump usage as well as additional heat available for recovery, potential energy savings will be determined. Preliminary results of five motors suggested for variable frequency drive application show annual savings that total 31.1 GWh, resulting in a 1.66% increase in overall plant efficiency. Total project costs are near $2 million resulting in a simple payback period of less than two years assuming 0.04 $/kWh. For every degree reduction of the flue gas temperature by means of heat recovery that is reused elsewhere in the cycle, 2 Billion BTU of coal would be saved annually. One realistic scenario suggested heat recovery resulting in a 120°F degree reduction of flue gas temperature amounting to a 2.54% increase in cycle efficiency.
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Mostaghim, Besarati Saeb. "Analysis of Advanced Supercritical Carbon Dioxide Power Cycles for Concentrated Solar Power Applications." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5431.
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Solar power tower technology can achieve higher temperatures than the most common commercial technology using parabolic troughs. In order to take advantage of higher temperatures, new power cycles are needed for generating power at higher efficiencies. Supercritical carbon dioxide (S-CO2) power cycle is one of the alternatives that have been proposed for the future concentrated solar power (CSP) plants due to its high efficiency. On the other hand, carbon dioxide can also be a replacement for current heat transfer fluids (HTFs), i.e. oil, molten salt, and steam. The main disadvantages of the current HTFs are maximum operating temperature limit, required freeze protection units, and complex control systems. However, the main challenge about utilizing s-CO2 as the HTF is to design a receiver that can operate at high operating pressure (about 20 MPa) while maintaining excellent thermal performance. The existing tubular and windowed receivers are not suitable for this application; therefore, an innovative design is required to provide appropriate performance as well as mechanical strength.
This research investigates the application of s-CO2 in solar power tower plants. First, a computationally efficient method is developed for designing the heliostat field in a solar power tower plant. Then, an innovative numerical approach is introduced to distribute the heat flux uniformly on the receiver surface. Next, different power cycles utilizing s-CO2 as the working fluid are analyzed. It is shown that including an appropriate bottoming cycle can further increase the power cycle efficiency. In the next step, a thermal receiver is designed based on compact heat exchanger (CHE) technology utilizing s-CO2 as the HTF. Finally, a 3MWth cavity receiver is designed using the CHE receivers as individual panels receiving solar flux from the heliostat field. Convective and radiative heat transfer models are employed to calculate bulk fluid and surface temperatures. The receiver efficiency is obtained as 80%, which can be further improved by optimizing the geometry of the cavity.
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Ha, Min Seok. "Thermal analysis of high power led arrays." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31803.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010.Committee Chair: Samuel Graham; Committee Member: J. Rhett Mayor; Committee Member: Yogendra Joshi. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Melbye, Anne-Marit. "Life Cycle Assessment of Norwegian Bioenergy Heat and Power Systems." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-20382.
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This thesis assesses several value chains for bioenergy production in Norway and combines these representing two Norwegian scenarios. The environmental impacts are assessed using the methodology of life cycle assessment (LCA). A complete assessment of climate change impact has been a core task, and biogenic CO2 emissions are accounted for throughout the value chains investigated. Surface albedo effects are included in the assessment of forest resources. In addition to global warming potential, the value chains are assessed for three other impact categories; acidification potential, particulate matter formation potential and terrestrial ecotoxicity potential. Life cycle inventories are constructed for a set of six feedstocks, seven treatment options, ten energy conversion options and three energy distribution choices. The different options are then combined to 80 feasible value chains. Transport is included throughout all the value chains. All inventories are assembled to represent Norwegian conditions. Energy flows for the different value chains investigated are found to represent the current bioenergy system, with a potential increase for each value chain towards 2020 - representing the alternative scenario. Results are generated for the individual value chains, the reference scenario and the alternative scenario. The results show large differences between the different value chains. Energy wood and waste wood are the most beneficial feedstocks for bioenergy production, highly dependent on both the GWPbio factors utilised and inclusion of surface albedo effects. Pelletising is the pre-treatment option resulting in the lowest GWP, while integrated torrefaction and pelletising results in the highest GWP. Overall, a CHP plant with electricity demand is the most advantageous conversion route. A stand-alone thermal electricity plant has the definite highest impact, mainly because of low conversion efficiency. Heat distribution shows high impacts compared to electricity and steam distribution, and the resources resulting in lower impacts is therefore recommended as inputs for such units. Generally, handling of biogenic CO2 emissions is of high importance. The same is the case for surface albedo effects, changing the GWP for forest resources considerably. CHP plants are recommended for electricity production from biomass, and use of TOP, forest residues and stemwood are recommended to take place in the same conversion technology. The environmental impacts from a CHP plant is low, and TOP, forest residues and stemwood show high GWP. The GWP from energy wood, wood waste and pellets are low, and are therefore recommended for use in district heating plants. As stand-alone electricity production is not recommended, the GWP from a district heating plant is limited with the use of the mentioned resources. Pelletising is recommended for pre-treatment of Norwegian biomass because of low climate change impacts. The Norwegian Government has put forth ambitious goals to reduce the GHG emissions substantially towards 2020 and become climate neutral by 2030. The reference scenario assessed show a GWP of 134 grams CO2-equivalents per kWh, while the scenario for 2020 results in a climate change impact of 136 grams CO2-equivalents per kWh. Based on this, Norwegian bioenergy can offer a means to reduce the GHG emissions towards 2020, but because of considerable GWP from biogenic CO2 emissions, bioenergy should not be pursued for a goal of becoming climate neutral by 2030.
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Faulkner, Simon A. "A simplified low head propeller turbine for micro hydroelectric power." Thesis, University of Canterbury. Engineering, 1991. http://hdl.handle.net/10092/6456.
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This thesis describes the development of a simplified propeller turbine unit to produce power in a low head micro hydroelectric power installation.
To be appropriate for remote areas and developing countries, a micro hydro system needs to be simple in design. There are good turbine designs for medium to high heads but traditional designs for heads under about 10m, ie, the crossflow turbine and waterwheel, are slow running, requiring substantial speed increase to drive an AC generator. Propeller turbines have a higher running speed but are normally too complicated for micro hydro installations.
In this thesis a suitable propeller turbine was developed. The effect of flat blades and optimum turbine blade and guide vane angles has been determined, as has the effect of various cones attached to the downstream end of the hub. The large hub diameter is an important compromise.
A prototype turbine for installation on a New Zealand farm was developed from model tests. The turbine has a hub diameter to blade tip diameter ratio of 0.66 and 8 flat blades set at 30° to tangential (60° from axial). The best efficiency of the model turbine was 62%, with an efficiency of 57% at the best power point. Using scaling laws it is predicted that the prototype, with a blade tip diameter of 0.410m, will produce 6.0kW at 612 RPM from a head of 2.7m and a flow rate of 0.41m³/s. This gives 4.3kW output from the 50Hz 2-pole generator. This prediction is for no cone fitted on the downstream end of the hub, but model tests indicate that the power could be improved by about 5% with the addition of a straight sided cone on the hub.
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Langston, Paul. "The role of ceramic heat exchangers in advanced power generation." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389927.
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BENITO, YIPSY ROQUE. "MODELING OF OFFSHORE PRODUCTION OF COLD, HEAT AND ELECTRICAL POWER." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=11017@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORFUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
AGÊNCIA NACIONAL DE PETRÓLEO
FINANCIADORA DE ESTUDOS E PROJETOS
O presente trabalho divide-se em dois estudos: uma análise global de sistemas de cogeração e uma modelagem de um ciclo de refrigeração por absorção. O primeiro estudo apresenta as equações dos balanços energéticos de um sistema de cogeração operando com dois motores térmicos distintos (turbina a gás e motor de combustão interna, ambos utilizando diesel como combustível). Para a produção de frio emprega-se um chiller de absorção, acionado a partir de calor de rejeito dos motores, e outro de compressão de vapor auxiliar. As equações de balanço de energia e de exergia, aplicadas a cada componente, formam um sistema não linear de equações que, resolvido, fornece o desempenho do sistema para diferentes condições de operação. O segundo estudo é parte de um projeto mais abrangente, destinado a desenvolver a tecnologia de um sistema de refrigeração por absorção. É apresentado o modelo matemático que caracteriza uma instalação de pequeno porte operando com uma mistura água-amônia. Foram aplicadas as equações de conservação de massa e energia para cada componente do ciclo, determinadas as propriedades termodinâmicas em cada ponto do ciclo e aplicadas hipóteses simplificadoras de modo a descrever matematicamente os processos físicos envolvidos. O modelo resultante foi aplicado a um sistema existente. A comparação entre os resultados previstos pelo modelo e os obtidos experimentalmente foi satisfatória. Uma vez implementados os modelos de ambos os estudos, realizaram-se simulações para casos particulares de operação, possibilitando a verificação da influência das principais variáveis sobre o desempenho dos sistemas analisados. Na solução dos modelos matemáticos foi utilizado o software EES.
The present work embodies two studies: a global analysis of cogeneration systems and an absorption refrigeration cycle model. The first study presents the main equations for energy and exergy balances of a cogeneration system operating with two distinct prime movers (a gas turbine and an internal combustion engine, both powered by diesel oil). For cooling production, an absorption chiller, driven by the prime movers` waste heat, and an auxiliary vapor compression chiller are employed. The energy and exergy balance equations were applied to each component of the system, composing a non-linear system of algebraic equations whose solution provides the performance of the system under different operating conditions. The second study is part of a broader project aiming at the development of an absorption refrigeration system. A mathematical model is presented, describing a small-size absorption refrigeration installation employing a water-ammonia mixture as working fluid. Mass and energy conservation equations were applied to each component of the cycle. Thermodynamic properties of the working fluids were calculated at each point of the cycle. Also, simplifying assumptions were applied. The resulting model was applied to simulate the behavior of an existing system. Comparison of predicted results with experimental data was satisfactory. A parametric analysis was also carried out with the simulation model. The models of both studies were implemented in ESSA software. Simulations were carried out so as to analyze the systems under particular operational conditions and to assess the influence of the main variables on system performance.
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Botros, Barbara Brenda. "Improving heat capture for power generation in coal gasification plants." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/69493.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 181-187).
Improving the steam cycle design to maximize power generation is demonstrated using pinch analysis targeting techniques. Previous work models the steam pressure level in composite curves based on its saturation temperature alone. The present work examines the effect of including both sensible and latent heating of steam in the composite curve. It is shown that including sensible heating allows for better thermal matching between the process and steam system which results in improving the overall efficiency while minimizing the capital cost. Additionally, fixed steam headers, such as assumed in total site analysis, give no allowance for reheating before turbine expansion, which can be valuable to consider when optimizing the steam system for certain plant configurations. A case study using an integrated gasification combined cycle (IGCC) plant with carbon capture and sequestration (CCS) is analyzed to assess changes in steam cycle design on the plant efficiency and cost. In addition to improving the steam system within an IGCC plant to improve efficiency, losses within the radiant heat exchanger can also be reduced. Instead of using high temperature syngas, cooling from 1300°C to 760°C, to boil steam at 330°C, another heat transfer fluid can be used and heated to higher temperatures. Material constraints restrict the maximum allowable temperature of the heat transfer fluid. To maintain high heat transfer coefficients in the heat transfer fluid, a fluid with high thermal conductivity, such as a liquid metal, can be used and heated to high temperatures (~700°C). Liquid metals can then act as an intermediate heat transfer medium, absorbing heat from high temperature syngas and rejecting it to steam at temperatures in excess of 500°C. The use of liquid metals leads to a 0.75 point increase in plant efficiency. Gases, such as carbon dioxide and helium, are also considered as potential heat transfer fluids in the radiant heat exchanger. These gases can be at equal pressure to the syngas pressure in the radiant heat exchanger, reducing the tensile stress in tube walls, but their low thermal conductivities still necessitate high strength materials at high temperature. A Brayton power cycle with recuperation is considered in this work, absorbing heat from the hot syngas and rejecting it to steam. Over a range of different Brayton cycle pressure ratios and maximum temperatures, no improvement in plant efficiency was found with respect to the case where steam is boiled in the same sized heat exchanger.
by Barbara Brenda Botros.
Ph.D.
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Kazuz, Ramadan. "Hybrid solar thermo-electric systems for combined heat and power." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/72508/.
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Solar energy has been extensively used in the renewable technology field, especially for domestic applications, either for heating, electrical generation or for a combination of heat and power (CHP) in one system. For CHP system solar photoelectric/thermal (PV/T) is the most commonly used technology for roof top applications. However, combination between solar hot water and thermoelectric generators has become an attractive for CHP system, this is due to its simplicity of construction and its high reliability. Moreover, this technology does not rely simply on sunlight and it can work with any other heat source, such as waste heat. However, its main drawback is its low efficiency. Recent publications by Kraemer et al (2011) and Arturo (2013) have shown that the efficiency of solar thermoelectric systems has improved dramatically, especially when combined with a solar concentrator system, as well as within a vacuum environment. The project recorded in this thesis focused on the design, construction and investigation of an experimental solar thermoelectric system based on a flat plate solar absorber. The aim was to study the technical feasibility and economical viability of generating heat and electric power using a solar thermoelectric hot water system. The design procedure involved on determining the heat absorbed and emitted, as well as the electrical power that was generated by the system. It began by obtaining the efficiency of the solar absorber, including selecting its paint, this was done through an experimental technique to determine the heat absorbed by the absorber, and the results obtained were verified by direct measurements of the light intensity. xvi An intensity meter was used, and results from both the experimental and theoretical models showed good agreement. The process also included calculating the heat from the system that was gained, lost and generated, as well as the electrical power provided. This was done to provide the system optimal size optimization to obtain the best and most economical system. Further improvement was made to the system by assembling a vacuum cavity, to improve the system’s efficiency. Although the maximum electrical efficiency obtained was relatively low (0.9%), compared to results recorded in the literature (Kraemer et al ,2011 and Arturo, 2013). However, the results of the electrical power output, under a vacuum level of 5 x 10-2mbar, increased approximately three times compared to the results obtained under normal (atmospheric) conditions. Additionally, the thermal power increased by 37% at this level of vacuum. The process involved determining the best thermoelectric geometries to achieve the optimum power outcome under different environmental conditions. The results showed that the system, which included the Thermoelectric device (TEG) with a larger geometric size, produced the best thermal power among other sizes. It was concluded that the system with the smallest TEG geometric size provided the best electrical power output.
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Tichagwa, Anesu. "Micro combined heat and power management for a residential system." Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/16914.
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Fuel cell technology has reached commercialisation of fuel cells in application areas such as residential power systems, automobile engines and driving of industrial manufacturing processes. This thesis gives an overview of the current state of fuel cell-based technology research and development, introduces a μCHP system sizing strategy and proposes methods of improving on the implementation of residential fuel cell-based μCHP technology. The three methods of controlling residential μCHP systems discussed in this thesis project are heat-led, electricity-led and cost-minimizing control. Simulations of a typical HT PEMFC -based residential μCHP unit are conducted using these control strategies. A model of a residential μCHP system is formulated upon which these simulated tests are conducted. From these simulations, equations to model the costs of running a fuel-cell based μCHP system are proposed. Having developed equations to quantify the running costs of the proposed μCHP system a method for determining the ideal size of a μCHP system is developed. A sizing technique based on industrial CHP sizing practices is developed in which the running costs and capital costs of the residential μCHP system are utilised to determine the optimal size of the system. Residential thermal and electrical load profile data of a typical Danish household are used. Having simulated the system a practical implementation of the power electronics interface between the fuel cell and household grid is done. Two topologies are proposed for the power electronics interface a three-stage topology and a two-stage topology. The efficiencies of the overall systems of both topologies are determined. The system is connected to the grid so the output of each system is phase-shifted and DC injection, harmonic distortion, voltage range and frequency range are determined for both systems to determine compliance with grid standards. Deviations between simulated results and experimental results are recorded and discussed and relevant conclusions are drawn from these.
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Sheikhi, Mehrabadi Elham. "Multi-Objective Optimization of Combined Heat and Power Industrial Microgrid." Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/21868.
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With the advent of distributed energy resources (DERs), such as solar photovoltaic (PV), distributed storages (DSs), and combined heat and power (CHP) generators, an opportunity was given to various customers to be satisfied with their local electricity and heat providers. Microgrid is a small-scale, localized power network that encompasses DERs, loads, and controllers. Microgrids could be a promising alternative for the conventional power system to solve environmental and economic concerns. Recently, CHP-based microgrids have widely attracted attention due to the cost effectiveness and pollution reduction. Most of the recent studies attempted to simplify microgrid components, loads, and constraints to decrease the analysis complexity; however, in this work, a comprehensive study of an industrial microgrid (IMG) comprising natural gas-based CHPs with different generation limits, PVs with intermittent outputs, PV storages, and boilers is taken into the consideration to totally satisfy variant electrical and heat demand over 24-hour period. Emission and cost are conflicting concerns in microgrid generation scheduling optimization and simultaneous optimization of these objectives was challenging. Optimization process is viable using various algorithms and techniques. Among all different approaches, NSGA-II and PSO are among the top-rated algorithms. In this innovative study, NSGA-II and PSO have been developed to reduce cost and emission objectives simultaneously with applying the most critical constraints and variable loads. The practical ability of the optimization process using the applied algorithms are demonstrated by analyzing two scenarios at the presence and absence of PV systems. Although both methods could satisfy electrical and thermal demands, the NSGA-II presented an improved solution compared to PSO method. Also, PV system effect on cost and pollution reduction was significant.
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Aghaeimeybodi, Mehdi. "Optimum Prime Mover Sizing in Combined Heat and Power Systems." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/10298.
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Combined heat and power (CHP) systems due to their high efficiency compared to the conventional power generation systems have received considerable attention as they have less harmful impact on the environment. Optimum selection of prime movers in CHP systems is of crucial importance due to the fact that inappropriate choices reduce the benefits of CHP systems considerably. In the selection procedure the performance characteristics of prime movers as well as economic parameters should be taken into consideration. As a variant of CHP systems, trigeneration systems are formed by adding an absorption chiller to combined heat and power systems to convert some of the recovered heat into required cooling loads. This results in a more efficient use of energy as the heat demand is subject to seasonal variations. In this thesis, thermo-economic approaches to selecting the optimum prime movers of small and medium scale CHP and turbine-based trigeneration systems as well as planning their operational strategy are studied. The prime movers considered include microturbine, gas turbine, internal combustion engines, and Stirling engine. Appropriate relations for estimating thermodynamic and economic parameters of the system in the context of Net Annual Cost (NAC) as well as Net Present Worth (NPW) criteria are introduced. As the commonly applied methods of dealing with the environmental concerns, the impact of a carbon tax as well as an emissions trading scheme has also been studied. For the purpose of demonstration, the developed methodologies have been used to optimally size potential prime movers of a number of operational case studies and to determine their operational strategy. Further, to determine the sensitivity of results to input parameters (e.g. electricity price) comprehensive sensitivity analyses have been conducted.
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Pearce, James Michael. "Combined heat and power in the home : a realistic concept?" Thesis, University of Manchester, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488114.
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Alanis, Francisco J. "Thermodynamic optimisation of industrial cogeneration systems and conventional power plant." Thesis, University of Manchester, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292578.
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Telesz, Mark P. "Design and Testing of a Thermoacoustic Power Converter." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11495.
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Thermoacoustic engines convert heat into acoustic pressure waves with no moving parts; this inherently results in high reliability, low maintenance and low manufacturing costs. Significant increases in the performance of these devices have enabled rivalry with more mature energy conversion methods in both efficiency and power output. This optimal production of acoustic power can be ultimately used to achieve cryogenic temperatures in thermoacoustic refrigerators, or can be interfaced with reciprocating electro-acoustic power transducers to generate electricity.
This thesis describes the design, fabrication and testing of a Thermoacoustic Power Converter. The system interfaces a thermoacoustic-Stirling heat engine with a pair of linear alternators to produce 100 watts of electricity from a heat input. It operates with helium at 450 psig internal pressure and a hot side temperature of 1200F. Through thermoacoustic phenomena, these conditions sustain a powerful pressure wave at a system specific 100 Hz. This pressure wave is used to drive the two opposed linear alternators in equal and opposite directions to produce a single phase AC electrical output at that same system frequency. The opposing motion of the two alternators enables a vibration-balanced system.
The engine has created 110 watts of acoustic power and the complete Thermoacoustic Power Converter system has produced 70 watts of AC electricity. Compensating for some heat leaks, the converter reaches 26.3% heat to acoustic power efficiency and 16.8% heat to electric efficiency when those maximum values are achieved. This conversion of heat to acoustic power is 40% of the Carnot thermodynamic efficiency limit.
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Berretta, Sara. "FEASIBILITY STUDY OF USING WIND POWER DRIVEN HEAT PUMP TO SUPPLY HEAT FOR A SINGLE HOUSE." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-23554.
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