The utilization of renewable energy resources such as wind and solar energy for electric power supply has received considerable attention in recent years due to adverse environmental impacts and fuel cost escalation associated with conventional generation. At the present time, wind and/or solar energy sources are utilized to generate electric power in many applications. Wind and solar energy will become important sources for power generation in the future because of their environmental, social and economic benefits, together with public support and government incentives. <p>The wind and sunlight are, however, unstable and variable energy sources, and behave far differently than conventional sources. Energy storage systems are, therefore, often required to smooth the fluctuating nature of the energy conversion system especially in small isolated applications. The research work presented in this thesis is focused on the development and application of reliability and economic benefits assessment associated with incorporating wind energy, solar energy and energy storage in power generating systems. A probabilistic approach using sequential Monte Carlo simulation was employed in this research and a number of analyses were conducted with regards to the adequacy and economic assessment of generation systems containing wind energy, solar energy and energy storage. The evaluation models and techniques incorporate risk index distributions and different operating strategies associated with diesel generation in small isolated systems. Deterministic and probabilistic techniques are combined in this thesis using a system well-being approach to provide useful adequacy indices for small isolated systems that include renewable energy and energy storage. The concepts presented and examples illustrated in this thesis will help power system planners and utility managers to assess the reliability and economic benefits of utilizing wind energy conversion systems, solar energy conversion systems and energy storage in electric power systems and provide useful input to the managerial decision process.

The utilization of renewable energy resources such as wind and solar energy for electric power supply has received considerable attention in recent years due to adverse environmental impacts and fuel cost escalation associated with conventional generation. At the present time, wind and/or solar energy sources are utilized to generate electric power in many applications. Wind and solar energy will become important sources for power generation in the future because of their environmental, social and economic benefits, together with public support and government incentives. <p>The wind and sunlight are, however, unstable and variable energy sources, and behave far differently than conventional sources. Energy storage systems are, therefore, often required to smooth the fluctuating nature of the energy conversion system especially in small isolated applications. The research work presented in this thesis is focused on the development and application of reliability and economic benefits assessment associated with incorporating wind energy, solar energy and energy storage in power generating systems. A probabilistic approach using sequential Monte Carlo simulation was employed in this research and a number of analyses were conducted with regards to the adequacy and economic assessment of generation systems containing wind energy, solar energy and energy storage. The evaluation models and techniques incorporate risk index distributions and different operating strategies associated with diesel generation in small isolated systems. Deterministic and probabilistic techniques are combined in this thesis using a system well-being approach to provide useful adequacy indices for small isolated systems that include renewable energy and energy storage. The concepts presented and examples illustrated in this thesis will help power system planners and utility managers to assess the reliability and economic benefits of utilizing wind energy conversion systems, solar energy conversion systems and energy storage in electric power systems and provide useful input to the managerial decision process.

The experience of electric energy shortage in 2001 demonstrated that our dependence almost exclusively on hydroelectricity could fetch great problems to Brazil. Thus being, the existence of trustworthy alternatives of energy must exist, at the very least, as a reserve. For this reason, the perspective of decentralizing the energy production as a form of promoting the socioeconomic development of remote communities not connected to the public distribution system as well for mass production of electricity, are the motivations of this work. Such situation justified the analysis of performance and development of the integration of diverse types of alternative primary sources by transforming them into current sources as a means of preventing the circulation of current due to voltage differences across the sources. Control of the load voltage uses the modulation of a secondary load in parallel with a primary load in such a way that current excesses from the current sources are drained only through the secondary load, remaining unchanged the conditions for the primary load. To manage the voltage and current distribution in the main load, a module, dedicated and expandable controller is proposed for hybrid systems of electric energy generation such as those using wind-solar-storage for generation of electric energy in a trustworthy form, unassisted and independent. The proposed integrated system of energy does allow the control and integration of the most usual forms of energy generation such as hydraulic, wind, storage of energy, specially, in batteries. The control program is also adjusted to integrate other forms of generation, independent of its origin. The control as a whole is based on the algorithm "Hill Climbing Control" (HCC) for individual maximization of the generated power and rotation in each source and regulating the voltage across the load, in order to get the best advantage from the installations. In this dissertation is also shown some practical results about the proposed theory on a prototype of control based on the micro controller PIC18F452 for distribution of energy from a power plant of electric energy generation installed and operating in the CEEMA-UFSM campus. Furthermore, the controller module of power as presented in this work is more useful among others because it allows the use of hybrid electronics and microelectronics that are able of concentrating several circuits in a only "chip", including control functions for power conversion, A/D devices, program memory, data memory, modules for capture and comparison, timers and PWM modules. / A experiência do racionamento de energia elétrica no ano de 2001 no Brasil demonstrou que nossa dependência quase que exclusivamente da hidroeletricidade pode nos trazer grandes problemas. Assim sendo, a existência de alternativas de energia confiáveis deve existir, no mínimo, como reserva. Por esse motivo, a perspectiva da descentralização da produção de energia como forma de promoção do desenvolvimento sócio-econômico de comunidades não atendidas pelas formas convencionais de energia bem como para produção em massa de energias alternativas para grandes sistemas de potência, foram as motivações deste trabalho. A necessidade de um conhecimento melhor da integração entre as fontes de energia. Tais temas justificaram a realização da análise do desempenho e o desenvolvimento de tecnologia para a integração de diversos tipos de fontes alternativas transformadas em fontes de corrente como forma de se evitar a circulação de correntes entre as fontes por diferenças individuais de tensão. O controle da tensão de carga usa a modulação de uma carga secundária em paralelo com outra primária tal que os excessos de corrente das fontes sejam drenados apenas para a carga secundária mantendo-se inalteradas as condições da carga primária. Para gerenciar a distribuição das correntes e a tensão na carga principal, utilizou-se um controlador modular, dedicado e expansível para sistemas híbridos de geração de energia elétrica tais como o eólico-solararmazenamento para geração de energia elétrica de forma confiável, desassistida e autônoma. O sistema de energia desenvolvido permite o controle e o acionamento integrados das formas mais conhecidas de geração de energia envolvendo fontes como a hidráulica, a eólica, armazenadores de energia, em especial, as baterias. O programa de controle é adequado para integrar outras formas de geração, independente de sua origem. O controle como um todo, baseia-se no algoritmo "Hill Climbing Control" (HCC) para maximização individual da potência gerada em cada fonte e para o contingenciamento da rotação pela carga, de modo a se obter o melhor proveito das instalações. Por outro lado, a tensão de saída é modulada através da carga secundária de tal forma a compor uma impedância a ser vista pela fonte de corrente resultante das fontes primárias que estabilize em torno da tensão nominal. Esta dissertação mostra os resultados práticos relativos a um protótipo de controle baseado no PIC18F452 para distribuição de energia a partir de uma central de geração de energia elétrica instalado e funcionando no campus da UFSM. O módulo controlador de potência como se apresenta, presta-se para a utilização dos recursos da eletrônica híbrida e da microeletrônica que podem concentrar num único "chip" diversos circuitos, incluindo conversores de potência, conversores A/D, memória de programa, memória de dados, módulos de captura e comparação, temporizadores e módulos PWM, entre outros.

In a nuclear fuel cask, the heat generating spent fuel rods are packed in a housing and the resulting bundle is placed inside a cask of thick outer shell made of materials like lead or concrete. The cask presents a wide variation in geometrical dimensions ranging from the diameter of the rods to the diameter of the cask. To make the problem tractable, first the heat generating rod bundle alone is considered for analysis and the effective thermal conductance of the bundle is correlated in terms of the relevant parameters. In the second part, the bundle is represented as a solid of equivalent thermal conductance and the attention is focused on the modelling of the cask. The first part, dealing with the effective thermal conductance is solved using Fluent software, considering coupled conduction, natural convection and surface radiation in the heat generating rod bundle encased in a hexagonal sheath. Helium, argon, air and nitrogen are considered as working media inside the bundle. A correlation is obtained for the critical Rayleigh number which signifies the onset of natural convection. A correlation is also developed for the effective thermal conductance of the bundle, considering all the modes of transport, in terms of the maximum temperature in the rod bundle, pitch-to-diameter ratio, bundle dimension (or number of rods), heat generation rate and the sheath temperature. The correlation covers pitch-to-diameter ratios in the range 1.1-2, number of rods ranging from 19 to 217 and the heat generation rates encountered in practical applications. The second part deals with the heat transfer modeling of the cask with the bundle represented as a solid of effective (or equivalent) thermal conductance. The mathematical model describes two-dimensional conjugate natural convection and its interaction with surface radiation in the cask. Both Boussinesq and non-Boussinesq formulations have been considered for convection. Numerical solutions are obtained on a staggered mesh with a pressure correction method using a custom-made Fortran code. The surface radiation is coupled to the conduction and convection at the solid-fluid interfaces. Steady-state results are obtained using time-marching. Results for various quantities of interest, namely, the flow and temperature distributions, Nusselt numbers, and interface temperatures, are presented. The Grashof number based on the volumetric heat generation and gap width is varied from 105 to 5 ×109. The emissivities of the interfaces are varied from 0.2-0.8 for the radiative calculations. The solid-to-fluid thermal conductivity ratio for the inner cylinder is varied in the range 5-20 in the parametric studies. Simulations are also performed with thermal conductivity calculated in an iterative manner from bundle parameters. The dimensionless outer wall conductivity ratio is chosen to correspond to cask walls made of lead or concrete. The dimensionless thickness (with respect to gap width) of the outer shell is in the range of 0.0825-1, while the inner cylinder dimensionless radius is 0.2. Air is the working medium in the cask for which the Prandtl number is 0.71. Correlations are obtained for the average temperatures and Nusselt numbers at the inner interface in terms of the parameters. The radiation heat transfer is found to contribute significantly to the heat dissipation.

Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2017-07-03T12:59:51Z No. of bitstreams: 2 Dissertação - Guilherme Resende Deus - 2016.pdf: 3406372 bytes, checksum: aaa431a0fa0dd2323a74cf35fb63f892 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-07-10T11:44:22Z (GMT) No. of bitstreams: 2 Dissertação - Guilherme Resende Deus - 2016.pdf: 3406372 bytes, checksum: aaa431a0fa0dd2323a74cf35fb63f892 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-07-10T11:44:22Z (GMT). No. of bitstreams: 2 Dissertação - Guilherme Resende Deus - 2016.pdf: 3406372 bytes, checksum: aaa431a0fa0dd2323a74cf35fb63f892 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-02-02 / The objective of this work is to find reasonable solutions to the problem of optimization of hydrothermal generating systems by means of metaheuristics based on particle swarms. The proposed problem is complex, dynamic, nonlinear and presents some stochastic variables. The study consisted of the implementation of particle swarm algorithms, more specifically the variants of the Particle Swarm Optimization (PSO) algorithm: LSSPSO, ABeePSO and KFPSO. The algorithms were run in a mill simulator containing data from eight National Interconnected System mills during the five year period. The results were compared with the studies using the Nonlinear Programming (NLP) algorithm, and it was concluded that although the presented meta-heuristics were able to obtain a Final Storage Energy value equal to NLP, they did not have a generation cost Equivalent to or less than the Nonlinear Programming method. / O trabalho objetiva encontrar soluções razoáveis para o problema de otimização de sistemas hidrotérmicos de geração por meio de meta-heurísiticas baseadas em enxame de partículas. O problema proposto é complexo, dinâmico, não linear e apresenta algumas variáveis estocásticas. O estudo consistiu na implementação de algoritmos baseados em enxame de partículas, mais especificamente das variantes do algoritmo Particle Swarm Optimization (PSO): LSSPSO, ABeePSO e KFPSO. Os algoritmos foram executados em um simulador de usinas que contém dados de oito usinas do Sistema Interligado Nacional durante o período de cinco anos. Os resultados foram comparados com os estudos que utilizam o algoritmo de Programação Não-Linear (PNL), e conclui-se que apesar de as meta-heurísticas apresentadas conseguirem obter um valor de Energia Armazenada Final igual ao PNL, não obtiveram um custo de geração equivalente ou inferior ao método de Programação Não-Linear.

[pt] A avaliação de confiabilidade da capacidade de geração é extremamente útil em diversos estudos de planejamento da expansão, na avaliação dos riscos relacionados ao dimensionamento da reserva operativa e também na programação da manutenção de unidades geradoras. O principal objetivo é avaliar se uma determinada configuração de unidades de geração atende de forma aceitável à carga do sistema, assumindo que os equipamentos de transmissão sejam totalmente confiáveis e sem limitações de capacidade. Na última década, a inserção de fontes renováveis nos sistemas elétricos de potência tem crescido de forma acentuada, na grande maioria dos países desenvolvidos como também em desenvolvimento. As flutuações de suas capacidades de geração se tornaram parte da complexidade do problema de planejamento e operação de redes elétricas, uma vez que dependem das condições ambientais em que foram instaladas. Além disso, representações detalhadas da carga têm se tornado uma preocupação a mais de muitos planejadores, tendo em vista as análises de risco ao atendimento da demanda nessas redes. Novos modelos e ferramentas computacionais devem ser desenvolvidos para tratar dessas variáveis principalmente com dependência espaço-temporal. Esta dissertação apresenta diversos estudos para avaliar a confiabilidade da capacidade de sistemas de geração via simulação Monte Carlo quasi-sequencial (SMC-QS), considerando fontes de geração e carga com forte dependência espaço-temporal. Esta ferramenta é escolhida devido à sua fácil implementação computacional e capacidade de simular eventos cronológicos. A técnica de redução de variância denominada amostragem por importância baseada no método Cross Entropy (CE) foi utilizada em conjunto com a SMC-QS. As simulações terão como base o sistema teste IEEE-RTS 96, o qual é adequada-mente modificado para incluir fontes renováveis eólicas e hídricas. Portanto, o principal objetivo desta dissertação é definir a melhor maneira de lidar com as séries temporais representativas da geração renovável e carga, nos diferentes estágios do método SMC-QS via CE, de modo a maximizar sua eficiência computacional. Vários testes de simulação são realizados com o sistema IEEE-RTS 96 modificado e os resultados obtidos são amplamente discutidos. / [en] The reliability evaluation of the generating capacity is extremely useful in several expansion planning studies, in the assessment of risks related to the requirements of the operating reserve and also in the scheduling of maintenance of generating units. The main objective is to assess whether a given generating configuration meets the system load in an acceptable manner, assuming that the transmission equipment is completely reliable and without capacity limitations. In the last decade, the insertion of renewable sources in electrical power systems has grown markedly, in the vast majority of developed and developing countries. Fluctuations in their generation capacities have become part of the complexity of the problem of planning and operating electrical networks, since they depend on the environmental conditions in which they are installed. In addition, detailed representations of the load have become a concern among many planners, given the risk analyzes to meet demand in these networks. New computational models and tools must be developed to deal with these variables mainly with space-time dependence. This dissertation presents several studies to evaluate the reliability of the capacity of generation systems via quasi-sequential Monte Carlo simulation (QS-MCS), considering generation and load sources with strong space-time dependence. This tool is chosen due to its easy computational implementation and the ability to simulate chronological events. The variance reduction technique named importance sampling based on the cross-entropy (CE) method is used in conjunction with the QS-MCS. The simulations will be carried out with the IEEE-RTS 96 test system, which is adequately modified to include renewable wind and hydro sources. Therefore, the main objective of this dissertation is to define the best way to deal with the time series representing the renewable generation and load, in the different stages of the SMC-QS method via CE, in order to maximize its computational efficiency. Several simulation tests are performed with the modified IEEE-RTS 96 system and the obtained results are widely discussed.