Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2018-01-17T21:17:50Z No. of bitstreams: 1 IsaúMB_DISSERT.pdf: 2720241 bytes, checksum: 6f834d2d4c55c17ad70d6fca472fbb7a (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2018-02-20T14:29:04Z (GMT) No. of bitstreams: 1 IsaúMB_DISSERT.pdf: 2720241 bytes, checksum: 6f834d2d4c55c17ad70d6fca472fbb7a (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2018-02-20T14:31:25Z (GMT) No. of bitstreams: 1 IsaúMB_DISSERT.pdf: 2720241 bytes, checksum: 6f834d2d4c55c17ad70d6fca472fbb7a (MD5) / Made available in DSpace on 2018-02-20T14:31:33Z (GMT). No. of bitstreams: 1 IsaúMB_DISSERT.pdf: 2720241 bytes, checksum: 6f834d2d4c55c17ad70d6fca472fbb7a (MD5) Previous issue date: 2017-08-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Environmental problems, like global warming and pollution, together with the rising fossil fuels prices in recent years have increased search for alternative energy sources, that are clean and sustainable at the same time. Among the main sources, it is possible to highlight the photovoltaic solar energy. For being a source of clean renewable energy with a low maintenance rate, photovoltaic solar energy has been gaining attention worldwide, and with this the Grid-Connected Photovoltaic System (GCPV) has grown in the last decades. Despite the benefits from the GCPV, for being a relatively new technology when compared with other energy sources, the same is not yet fully consolidated, and its installation requires care in regard to quality of electrical power. Problems such as production of harmonics, overvoltage and low power factor are common to these types of systems. Several researches are conducted every year and regulations are created, in order to reconcile the photovoltaic generation with the power distribution network. Therefore, the present work aims to identify, measure and analyze the behavior of GCPV of 3 kWp of UFERSA, in the city of Mossoró-RN, in order to verify the possible impacts to the quality of the electric energy associated with GCPV. In this research it was noticed that all the parameters are within the current standard regulations, however the high indexes of harmonic distortion rate made necessary the elaboration of a low-pass filter to attenuate the unwanted frequencies. With the simulation of the filter in Simulink, an attenuation of up to more than 60% was verified, thus improving the quality of the energy generated by the system / Os problemas ambientais, como o aquecimento global e a poluição, juntamente com o crescente preço dos combustíveis fósseis nos últimos anos, elevaram a procura por fontes alternativas de energia, que ao mesmo tempo fossem limpas e sustentáveis. Dentre as principais fontes, pode-se destacar a energia solar fotovoltaica. Por ser uma fonte de energia limpa, renovável e com baixo índice de manutenção, a energia solar fotovoltaica vem ganhando destaque no mundo inteiro, e com isso os Sistemas Fotovoltaicos Conectados à Rede (SFCR) cresceu nas últimas décadas. Apesar dos benefícios oriundos dos SFCR, por ser uma tecnologia relativamente nova quando comparada com outras fontes de energia, a mesma ainda não está totalmente consolidada, e sua instalação requer cuidados no que diz respeito à qualidade de energia elétrica. Problemas como produção de harmônicos, sobretensão e baixo fator de potência são comuns a estes tipos de sistemas. Várias pesquisas são realizadas todos os anos, e normas e regulamentos são criados, a fim de conciliar a geração fotovoltaica com a rede elétrica de distribuição. Portanto, o presente trabalho tem como objetivo identificar, medir e analisar o comportamento do SFCR de 3 kWp da UFERSA, na cidade de Mossoró-RN, a fim de se verificar os possíveis impactos à qualidade da energia elétrica associados aos SFCR’s. Nesta pesquisa percebeu-se que todos os parâmetros estão dentro das normas vigentes, porém os altos índices de taxa de distorção harmônica fizeram necessário a elaboração de um filtro passa-baixa para atenuar as frequências indesejadas. Com a simulação do filtro no Simulink, constatou-se uma atenuação de até mais de 60%, melhorando assim a qualidade da energia gerada pelo sistema / 2018-01-17

Electrical energy plays an indispensable role in our contemporary society. However, we mostly realize its position in agriculture in a situation which often already entails irreversible consequences. Therefore, the thesis aims to assess the consequences of power blackout on agricultural farming. In connection with the selected objective, a question arises whether long-term power blackouts also constitute a serious threat to agricultural farms of South Bohemia? The theoretical part briefly describes electrical energy, its production and method of transmission. It also includes basic elements of the power system including its stability and safety. The chapter also acquaints the reader with the critical infrastructure of the Czech Republic and its legislative base. Then, it globally analyzes the term blackout.Given the topic of the thesis, it is necessary to mention the valuable work of the integrated rescue system which in addition to the basic obligations to ensure the protection of human life and property is required to provide missions to rescue animals in emergency situations. Finally, this chapter deals with the application of electrical energy in agriculture, including the characteristics of surveyed farms and a high degree of automation used in farming.The research part is based on the search of the current state of selected agricultural farms. The research was focused on the South Bohemian Region which makes no exception in relation to this issue. Used for the research was a qualitative method of data collection with the information obtained through the techniques of controlled interviews and the secondary analysis of data provided by competent employees of farms in South Bohemia. The results are then outlined in two planes. During recent years, breeding stations have been completely renovated, especially in the section of technological processes. Modern electronic devices which include e.g. automated milking, feeding, suction and washing equipment, heating of service water and heating, should ensure trouble-free operation in such farms. However, what the vast majority of farms is not adequately prepared for is to ensure their smooth operation even during a failure of the electrical system. A number of farms do not have an alternate source of electrical energy. The percentage of self-sufficient farms having on its premises a pumping station that can supply the local diesel-aggregate, is also negligible. Moreover, in case of a diesel-aggregate failure, no alternative source is available. A crucial problem arises in the category of poultry. The animals are situated in large-volume halls where all processes are controlled by fully automated control systems. An alternative source of electrical energy is a crucial element needed to ensure normal operation of the farms. Unless the established criteria are in compliance (ventilation, lighting, etc.), reaction of the animals becomes evident within tens of minutes. Any deviation results in rapid loss of animals. It is assumed that the resulting data will be used both for research purposes in the area of secondary impacts in case of electrical system failures and for objective assessment of the effectiveness in farming security within the current methods. The purpose is to educate the above entities.

Submitted by Maike Costa (maiksebas@gmail.com) on 2016-04-25T12:59:29Z No. of bitstreams: 1 arquivo total.pdf: 2399944 bytes, checksum: b31ffd454938b9e66e2494032cb6d9ee (MD5) / Made available in DSpace on 2016-04-25T12:59:29Z (GMT). No. of bitstreams: 1 arquivo total.pdf: 2399944 bytes, checksum: b31ffd454938b9e66e2494032cb6d9ee (MD5) Previous issue date: 2015-08-28 / In recent years, several studies where published regarding to the estimation of variables related to the use of electricity, where the most varied methodologies are used to perform modeling and estimation of demand for energy of countries, States, companies in general and educational systems. In this dissertation where chosen this last category and the focus is on Higher Education Institutions (HEIs). Looking for drawing up an estimate of Wing Maxim Demand (WMD), monthly of electrical energy power, for the (HEIs), from the amount of students and, if necessary, from other causal variables, which can contribute to managerial way for the renegotiation of contracts with concessionaires that lead to annual cost savings and still contribute to a better control of the levels of maxim demand of electricity. To achieve this objective, it was realized a review of the literature regarding to the variables that could introduce correlation with the dependent variable WMD. This review indicated several methodologies that could contribute to the solution of the problem proposed: Markov Chain, Support vector Regression methodology, Genetic Programming Model and Artificial Neural Networks. It was adopted the methodology of Multiple Linear Regression (MLR) because it is less complex and a methodology directed at large companies. It was selected an IES and were carried out interviews with some engineers and technician of his electrical engineering division, seeking to better understand energy use and the behavior of the variable WMD in this IES being made available the reports of power energy monitoring where the WMD data of January-December 2008 of 2014 were contained. So on the basis of these data and documental research of the independent variables, and, through the methodologies of Multiple Linear Regression (MLR), it was developed a model from the data of 72 months which had their waste evaluated, showing a coefficient of determination R ^ 2 equal to 0.883. Independent variables that remained in the model, from the use of the backward method, were 4 (four) Dummy variables associated with the years, six variables of this type associated with the months and a variable which is the product of school days for graduates and the quantity of graduate students registered. This model was able to identify seasonality presents in the behavior of the WMD of this HIE. It would allow the hiring of WMD per month, that would make savings of 57% compared to the traditional contracting mode (WMD fixed for the entire period), considering the period from July to December, before the period left for validation. In conclusion, a forecast for the period of January to May 2015 and the adoption of the proposed model was able to provide a savings of 45% in relation to the scheme currently used by this HEI. / Nos últimos anos, diversos trabalhos foram publicados em relação à estimativa de variáveis relacionadas ao uso da energia elétrica, onde as mais variadas metodologias são utilizadas para realizar a modelagem e estimação da demanda por energia de países, Estados, empresas em geral e dos sistemas de ensino. Nesta dissertação foi escolhida esta última categoria e o foco consiste nas Instituições de Ensino Superior (IES). Procurando elaborar uma estimativa de Demanda Máxima de Ponta (DMP), mensal de potência de energia elétrica adequada às IESS, a partir da quantidade de alunos, e, se necessário, a partir de outras variáveis causais, que possam contribuir de maneira gerencial para a renegociação de contratos com concessionárias que levem à redução de custos anuais e que ainda podem contribuir para um melhor controle dos níveis de demanda máxima de energia elétrica. Para alcançar tal objetivo, foi realizada uma revisão da literatura a respeito de variáveis que poderiam apresentar correlação com a variável dependente DMP. Esta revisão indicou várias metodologias que poderiam contribuir para a solução do problema proposto: a Cadeia de Markov, a Metodologia de Regressão do vetor de Suporte, o Modelo de Programação Genética e as Redes Neurais Artificiais. Por ser uma metodologia menos complexa e direcionada a empresas de grande porte, adotou-se a Metodologia de Regressão Linear Múltipla (RLM). Foi selecionada uma IES e foram realizadas entrevistas com alguns engenheiros e técnico da sua divisão de engenharia elétrica, procurando entender melhor o uso da energia e o comportamento da variável DMP nesta IES, sendo disponibilizados os relatórios de energia do sistema de monitoração de energia onde os dados de DMP de janeiro de 2008 a dezembro de 2014 estavam contidos. Então, com base nestes dados e em pesquisa documental das candidatas a variáveis independentes, e, através da Metodologia (RLM), foi desenvolvido um modelo a partir dos dados de 72 meses, que teve seus resíduos avaliados, apresentando um coeficiente de determinação 𝑅2 igual a 0,883 .As variáveis independentes que permaneceram no modelo, a partir da utilização do método backward, foram 4(quatro) variáveis Dummy associadas a anos, seis variáveis deste tipo associadas a meses e uma variável fruto do produto entre dias letivos de graduação e quantidade de alunos da graduação matriculados. O modelo foi capaz de identificar a sazonalidade presente no comportamento da DMP da IES em estudo. Ele possibilitaria a contratação de DMP por mês, o que daria uma economia de 57% em relação ao modo de contratação tradicional (DMP fixo para todo o período), considerando o período de julho a dezembro, antes do período deixado para validação. Concluindo, foi realizada uma previsão para o período de janeiro a maio de 2015 e a adoção do modelo proposto foi capaz de proporcionar uma economia de 45% em relação ao esquema utilizado atualmente pela IES.

Made available in DSpace on 2014-12-17T14:55:18Z (GMT). No. of bitstreams: 1 ArrheniusVCO_da_capa_ate_pag_12.pdf: 7828798 bytes, checksum: b0f0c76e1aebc32a2155c024e0abc8a9 (MD5) Previous issue date: 2004-12-17 / The objective of the present work is develop a model to simulate electrical energy networks in transient and stead states, using the software ATP (Alternative Transient Program), able to be a way to join two distinct themes, present in classical methodology planning networks: short circuit analysis and load flow theory. Beyond that, using a tool for relay simulation, this paper intend to use the new developed model to investigate the influence of transient phenomenon in operation of protection relays, and calibrate the enterprise's protections relays. For testing the model, some relays, actually, installed at COSERN were used / O presente trabalho objetiva ao desenvolvimento de um modelo para simular redes de energia el?trica em regimes transit?rio e permanente, utilizando o software ATP (Alternative Transient Program), para servir como elo entre dois temas distintos, presentes na metodologia cl?ssica de planejamento de redes: a an?lise de curtos-circuitos e o estudo de fluxo de carga. Al?m disso, dispondo de uma ferramenta de simula??o de rel?s, pretende-se usar o novo modelo, tanto para averiguar a influ?ncia de fen?menos transit?rios na opera??o dos rel?s de prote??o, quanto para calibrar esses rel?s. Para testar o modelo, utilizaram-se alguns dos rel?s atualmente instalados na COSERN

Made available in DSpace on 2014-12-17T14:56:08Z (GMT). No. of bitstreams: 1 AlynneCSQ_DISSERT.pdf: 5674522 bytes, checksum: 276b6f887cbd025afcc9fc319a3dbc2e (MD5) Previous issue date: 2012-09-24 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The opening of the Brazilian market of electricity and competitiveness between companies in the energy sector make the search for useful information and tools that will assist in decision making activities, increase by the concessionaires. An important source of knowledge for these utilities is the time series of energy demand. The identification of behavior patterns and description of events become important for the planning execution, seeking improvements in service quality and financial benefits. This dissertation presents a methodology based on mining and representation tools of time series, in order to extract knowledge that relate series of electricity demand in various substations connected of a electric utility. The method exploits the relationship of duration, coincidence and partial order of events in multi-dimensionals time series. To represent the knowledge is used the language proposed by M?rchen (2005) called Time Series Knowledge Representation (TSKR). We conducted a case study using time series of energy demand of 8 substations interconnected by a ring system, which feeds the metropolitan area of Goi?nia-GO, provided by CELG (Companhia Energ?tica de Goi?s), responsible for the service of power distribution in the state of Goi?s (Brazil). Using the proposed methodology were extracted three levels of knowledge that describe the behavior of the system studied, representing clearly the system dynamics, becoming a tool to assist planning activities / A abertura do mercado brasileiro de energia el?trica e a competitividade entre as empresas do setor energ?tico fazem com que a busca por informa??es ?teis e ferramentas que venham a auxiliar na tomada de decis?es, aumente por parte das concession?rias. Uma importante fonte de conhecimento para essas concession?rias s?o as s?ries temporais de consumo de energia. A identifica??o de padr?es de comportamento e a descri??o de eventos se tornam necess?rias para a execu??o de atividades de planejamento, buscando melhorias na qualidade de atendimento e vantagens financeiras. A presente disserta??o apresenta uma metodologia baseada em ferramentas de minera??o e representa??o de s?ries temporais, com o objetivo de extrair conhecimento que relacionam s?ries de demanda de energia el?trica de diversas subesta??es interligadas de uma concession?ria. O m?todo utilizado explora rela??es de dura??o, coincid?ncia e ordem parcial de eventos em s?ries temporais multidimensionais. Para a representa??o do conhecimento ser? utilizada a linguagem proposta por M?rchen (2005) chamada Time Series Knowledge Representation (TSKR). Foi realizado um estudo de caso usando s?ries temporais de demanda de energia de 8 subesta??es interligadas por um sistema em anel, que alimenta a regi?o metropolitana de Goi?nia-GO, cedidas pela CELG (Companhia Energ?tica de Goi?s), permission?ria do servi?o de distribui??o de energia no estado de Goi?s (Brasil). Utilizando a metodologia proposta foram extra?dos tr?s n?veis de conhecimento que descrevem o comportamento do sistema estudado, representando a din?mica do sistema de forma clara, constituindo-se em uma ferramenta para auxiliar em atividades de planejamento

Made available in DSpace on 2014-07-29T15:08:20Z (GMT). No. of bitstreams: 1 dissertacao joao carlos pre textuais.pdf: 617522 bytes, checksum: bb07bb21bb4875ee05bd7e833ba62c51 (MD5) Previous issue date: 2009-02-10 / This work presents a case analysis of energetic harnessing in a piggery, based on the use of biogas generated from pig sewage. The analysis shows that the energy from the biogas produced in the farm processes can be partially used through Clean Development Mechanisms (CDM) in order to improve the system efficiency. The utilized process presents environmental and economical benefits as carbon emissions are reduced and their credits can be traded. Moreover, an economic analysis of alternatives for biogas use was carried out taking into account technical, environmental and financial aspects. The case study was realized on a piggery farm in the south-west of the Goiás State where the economical viability of each of the presented alternatives was analyzed considering the following: total burning of biogas; generation of electrical energy; heating; or the combined heat and power generation (CHP). / Este trabalho apresenta a análise de um caso baseado no aproveitamento do biogás gerado a partir de rejeitos de suínos. A análise mostra que a energia do biogás produzido nos processos da granja pode ser parcialmente aproveitada através de mecanismos de desenvolvimento limpos (MDL) com a finalidade de aumentar a eficiência energética do sistema. O processo utilizado apresenta benefícios ambientais e econômicos, já que as emissões de carbono são reduzidas e seus créditos podem ser negociados. Uma análise econômica de alternativas de geração energética do biogás é também apresentada, considerando-se aspectos técnicos, ambientais e financeiros. O estudo foi realizado em uma granja no sudoeste do estado de Goiás, e analisa a viabilidade de cada uma das alternativas apresentadas para o aproveitamento energético do gás, que são: queima total do biogás; geração de energia elétrica; aquecimento; ou a combinação de aquecimento e geração de energia elétrica.

Submitted by Goret Pereira Paulo (goret.paulo@fgv.br) on 2012-12-13T17:48:24Z No. of bitstreams: 1 TESE_FINAL_versao final.pdf: 1970825 bytes, checksum: 9eb828cc4cae7a7908af2fbff6d27c8a (MD5) / Approved for entry into archive by Suzinei Teles Garcia Garcia (suzinei.garcia@fgv.br) on 2012-12-13T18:41:48Z (GMT) No. of bitstreams: 1 TESE_FINAL_versao final.pdf: 1970825 bytes, checksum: 9eb828cc4cae7a7908af2fbff6d27c8a (MD5) / Made available in DSpace on 2012-12-14T12:10:56Z (GMT). No. of bitstreams: 1 TESE_FINAL_versao final.pdf: 1970825 bytes, checksum: 9eb828cc4cae7a7908af2fbff6d27c8a (MD5) Previous issue date: 2012-08-15 / Com o objetivo de contribuir com a literatura sobre a regulação dos setores de infraestrutura, este trabalho apresenta uma análise do modelo regulatório utilizado para viabilizar a expansão de capacidade do setor de transmissão de energia elétrica no Brasil. Neste país, de dimensões continentais, o setor de transmissão tem um papel de fundamental importância para garantir o suprimento de energia elétrica e, consequentemente, para viabilizar uma trajetória de crescimento sustentável da atividade econômica. Grandes quantidades de energia são transportadas entre as unidades geradoras, principalmente hidroelétricas que, em muitos casos, estão localizadas em regiões bem distantes dos grandes centros de consumo. Devido à similaridade entre as dimensões continentais e os volumes de energia produzidos e consumidos, são comparados os modelos regulatórios utilizados para a expansão da transmissão no Brasil e Argentina. Aspectos institucionais e dos sistemas políticos nos dois países são ressaltados para explicar as diferenças entre os dois modelos e os resultados alcançados em cada um dos países. Neste caso destacam-se os desafios para expansão da infraestrutura de transmissão de elevada tensão e grande extensão no caso argentino e os benefícios do modelo brasileiro que combina a realização de leilões com um mecanismo de planejamento centralizado. As especificidades do modelo regulatório brasileiro, principalmente do modelo híbrido de leilões de contratos de concessões de transmissão, acompanhado de revisões periódicas da receita dos investidores têm especial atenção. Através de uma análise dos lances apresentados nos leilões realizados no Brasil entre 2002 e 2008, testa-se a reação dos participantes com relação à mudança no modelo regulatório introduzida em 2006, ano em que foi introduzida a revisão tarifária periódica nos contratos de concessão para serviços de transmissão. Evidencia-se que, com esta mudança, os participantes não diminuíram os deságios praticados nos leilões, indicando que não houve aumento da percepção de risco do negócio para os investidores devido a esta mudança na regulação. As informações utilizadas pelos participantes para formulação dos lances, no modelo de leilões para a expansão da transmissão no Brasil, são analisadas através de uma amostra ampliada dos lances apresentados no período 1999-2011. Encontram-se evidências empíricas de que os lances dos participantes são correlacionados, indicando que estes levam em consideração os lances dos seus competidores para formulação de seus próprios lances. / With the purpose of contributing to the literature about regulation of infrastructure sectors, this paper shows an analysis of the regulatory model used to enable the expansion of the electrical energy transmission capacity in Brazil. In this country, of continental dimensions, the transmission sector plays a vital role enabling the electrical energy supply and, thus, enabling a sustainable growth path for the economic activity. Large amounts of energy are transmitted among generator units, mainly hydroelectric power plants, which, in many cases, are located in regions quite faraway from big consumption centers. Due to the similarity among continental dimensions and volumes of energy produced and consumed, the regulatory models used for the expansion of the transmission in Brazil and Argentina are compared. Institutional and political system aspects in both countries are highlighted in order to explain the differences between the two models as well as the results achieved in each country. In this case, the challenges are highlighted for the expansion of the transmission infrastructure of high tension and large extensions in the Argentinean case, as well as the advantages of the Brazilian model that matches auctioning and a centralized planning mechanism. The peculiarities of the Brazilian regulatory model, mainly concerning the hybrid model of transmission award agreement auctions, along with periodical reviews of investor's revenue, get special attention. Through an analysis of the bids presented in the auctions carried out in Brazil between 2002 and 2008, the reaction of participants is tested as regards the change in the regulatory model introduced in 2006, when the periodical tariff review was introduced in award agreements for transmission services. With this change, participants have not increased the value of their bids at the auctions, indicating that there has not been an increase in the perception of the business risk for investors due to this regulatory change. The information used by the participants to present their bids, in the auction model for transmission expansion in Brazil, is analyzed through an extended sample of the bids presented between 1999-2011. Empirical evidences are found that the participants' bids are correlated, indicating that they take competitors' bids into account in order to elaborate their own bids.

Continued emission of green house gases has energized research activity worldwide to develop efficient ways to harness renewal energy. The availability of large scale energy storage technologies is essential to make renewal energy a reliable source of energy. Redox flow batteries show potential in this direction. These batteries typically need expensive membranes which need replacement be-cause of fouling. The recently proposed soluble lead redox flow battery (SLRFB), in which lead ions deposit on electrodes in charge cycle and dissolve back in discharge cycle, can potentially cut down the cost of energy storage by eliminating membrane. A number of challenges need to be overcome though. Low cycleability, residue formation, and low efficiencies are foremost among these, all of which require an understanding of the underlying mechanisms. A model of laminar flow-through SLRFB is first developed to understand buildup of residue on electrodes with continued cycling. The model accounts for spatially and temporally growing concentration boundary layers on electrodes in a self consistent manner by permitting local deposition/dissolution rates to be controlled by local ion transport and reaction conditions. The model suggests controlling role for charge transfer reaction on electrodes (anode in particular) and movement of ions in the bulk and concentration boundary layers. The non-uniform current density on electrodes emerges as key to formation of bare patches, steep decrease in voltage marking the end of discharge cycle, and residue buildup with continuing cycles. The model captures the experimental observations very well, and points to improved operational efficiency and decreased residue build up with cylindrical electrodes and alternating flow direction of recirculation. The underlying mechanism for more than an order of magnitude increase in cycle life of a beaker cell battery with increase in stirrer speed is unraveled next. Our experiments show that charging with and without stirring occurs identically, which brings up the hitherto unknown but quite strong role of natural convection in SLRFB. The role of stirring is determined to be dislodgement/disintegration of residue building up on electrodes. The depletion of active material from electrolyte due to residue formation is offset by “internal regeneration mechanism”, unraveled in the present work. When the rate of residue formation, rate of dislodging/disintegration from electrode, and rate of regeneration of active material in bulk of the electrolyte becomes equal, perpetual operation of SLRFB is expected. The identification of strong role of free convection in battery is put to use to demonstrate a battery that requires stirring/mixing only intermittently, during open circuit stages between charge and discharge cycles when no current is drawn. Inspired by our experimental finding that the measured currents for apparently diffusion limited situations (no external flow) are far larger than the maxi-mum possible theoretical value, the earlier model is modified to account for natural convection driven by concentration gradient of lead ions in electrolyte. The model reveals the presence of strong natural convection in battery. The induced flow in the vicinity of the electrodes enhances mass transport rates substantially, to the extent that even in the absence of external flow, normal charge/discharge of battery is predicted. The model predicted electrochemical characteristics are verified quantitatively through voltage-time measurements. The formation of flow circulation loops driven by electrode processes is validated qualitatively through PIV measurements. Natural convection is predicted to play a significant role in the presence of external flow as well. The hitherto unexplained finding in the literature on insensitivity of charge-discharge characteristics to electrolyte flow rate is captured by the model when mixed mode of convection is invoked. Flow reversal and wavy flow are predicted when natural convection and forced convection act in opposite directions in the battery. The effect of the presence of non-conducting material (PbO on anode) on the performance of SLRFB is studied using a simplified approach in the model. The study reveals the presence of charge coup de fouet phenomenon in charge cycle. The phenomenon as well as the predicted effect of depth of discharge on the magnitude of charge coup de fouet are confirmed experimentally.

Rapporten avhandlar en konceptstudie för omvandling av termisk energi till elektrisk samt mekanisk energi, i den autonoma undervattensfarkosten SAPPHIRES. Inledningsvis utreds vilka förväntningar och krav som finns på konceptet för energiomvandling samt om där finns någon publicerad litteratur som redan gjort ansträngningar för att lösa det aktuella problemet. Allmän teori kring värmemotorer och en bred, systematisk litteratursökning inkluderas även i det arbetet. Energiomvandlingen antas kunna ske enligt två fall kallade ”hög-prestanda” och ”låg/medel-prestanda”, vilka innebär att mekanisk samt elektrisk effekt, respektive endast elektrisk effekt ska kunna levereras av konceptet. De mekaniska samt elektriska effekterna ska, vidare, kunna levereras om maximalt 600, respektive 6 kW, och konceptet ska åtminstone kunna uppfylla ett av energiomvandlingsfallen. Den faktiska konceptstudien utgörs av två iterationer av konceptgenereringar, -utvärderingar och -val och de visar att ett koncept kallat ”Öppet system inspirerat av nukleär värmeframdrivning” förefaller vara det bästa sättet att omvandla termisk energi i SAPPHIRES. Därtill indikerar en mer detaljerad analys, bestående av bland annat matematisk modellering och konceptuell konstruktion, att konceptet möjligen skulle kunna uppfylla så kallad ”hög-prestanda” och sedermera leverera både mekanisk och elektrisk effekt om 600, respektive 6 kW. Mer specifikt visar en matematisk analys, med hjälp av vissa antaganden rörande konceptets funktion, att ett ”Öppet system inspirerat av nukleär värmeframdrivning” skulle kunna leverera en mekanisk effekt om 1025 kW samt en elektrisk effekt om 141 kW. En grov, konceptuell konstruktion bekräftar också att konceptets vitala, ingående komponenter faktiskt kan rymmas inom de specificerade dimensionskraven (en cylinderformad volym med en längd och diameter om 1,7, respektive 0,5 m.). Det står dock klart att de möjliga koncepten för energiomvandling kraftigt begränsas av deras möjligheter att leverera tillräcklig mekanisk effekt, för att uppnå ”hög-prestanda”. Om endast ”låg/medel-prestanda” ska uppfyllas tillåts fler av de möjliga koncepten och i ett sådant fall skulle faktorer som underhåll, miljöpåverkan och SAPPHIRES signatur kunna prioriteras i högre utsträckning. / The report discusses a concept study regarding the conversion of thermal energy into electrical and mechanical energy, in the autonomous underwater vehicle SAPPHIRES. First, the requirements and expectations regarding the concept of energy conversion are investigated and efforts are made to identify any published literature, which has already made attempts of solving the issue. General theory regarding heat engines and an extensive literature study are also included in this work. The energy conversion is assumed to perform according to two cases called "high-performance" and "low/medium-performance", meaning mechanical and electrical energy or electrical power should be delivered by the concept, respectively. More specifically, the mechanical and electrical powers should be delivered of a maximum of 600 and 6 kW, respectively and the concept should at least fulfill one of the performance settings. The actual concept study comprises of two iterations of concept generations, evaluations and selections and shows that a concept called "Open system inspired by nuclear thermal propulsion" seems to be the best way of converting thermal energy on-board SAPPHIRES. Moreover, a more detailed analysis, comprising of, inter alia, mathematical modelling and conceptual design, indicates that the concept possibly can meet the so-called "high-performance" and thus, deliver both mechanical and electrical powers of 600 and 6 kW, respectively. More specifically, a mathematical analysis, based on some assumptions regarding the concept's functionality, shows that an "Open system inspired by nuclear thermal propulsion" could deliver a mechanical power of 1025 kW and an electrical power of 141 kW. Rough conceptual design also shows that the vital parts of the concept could fit within the specified maximal dimensions (a cylinder-shaped volume with a length and diameter of 1.7 and 0.5 m, respectively). However, it is clear the possible concepts of energy conversion are severely limited by their capacities of delivering enough mechanical energy, to meet the "high-performance" demands. Assuming only the "low/medium-performance" has to be met, more possible concepts becomes available and in that case, factors such as maintenance, environmental impact and signature of SAPPHIRES could be considered to a greater extent.

Orientador: Prof. Dr. Thales Souza / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, Santo André, 2018. / Atualmente, no Brasil, a matriz elétrica é composta predominantemente por fonte hidráulica e térmica, na proporção de 70% e 30%, respectivamente. Nesse sentido, para a segurança do Sistema Interligado Nacional, o mesmo é considerado um sistema hidrotérmico, onde a disponibilidade de armazenamento das bacias hidráulicas e de combustíveis representa a quantidade de energia elétrica disponível para atendimento a demanda. Assim, os critérios para cálculo de Energia Assegurada representam as Garantias Físicas das Usinas Hidrelétricas e Usinas Térmicas, que são calculadas através das médias de gerações dos empreendimentos disponíveis no Sistema Interligado Nacional com a previsão de 15 anos. Contudo, a expansão dos aproveitamentos de usinas com reservatório encontra-se no limite de exploração no sul e sudeste/centro-oeste, havendo apenas na região Norte potenciais a serem avaliados. Entretanto, devido às restrições ambientais, não há previsão de construção de novas Usinas Hidrelétricas com reservatório na região Norte, o que indica a necessidade de viabilização de outras fontes de energia elétrica. Nesse sentido, a Garantia Física é utilizada para balizar qual o risco de déficit futuro considerando o balanço de demanda e oferta no sistema. Dessa forma, o presente trabalho propôs a análise dos parâmetros de risco da Garantia Física do sistema imputados no modelo de projeção elétrico NEWAVE. Por fim, com objetivo de validar a análise proposta, as projeções de Garantias Físicas das Usinas Hidrelétricas e Usinas Térmicas que fazem parte do Sistema Interligado Nacional foram avaliadas, a partir do método de escolha do risco de déficit. / Currently, in Brazil, the electrical matrix is mainly composed of hydraulic and thermal sources, in the proportion of 70% and 30%, respectively. In this sense, for the safety of the National Interconnected System, it is considered a hydrothermal system, in which the storage capability of the hydraulic basins and fuel availability represent the amount of electrical energy available to meet demand. Thus, the criteria for calculation of Assured Energy represent the Physical Guarantees of the Hydroelectrical Power Plant and Thermal Power Plants, which are calculated through the average of generations of the enterprises available in the National Interconnected System with a forecast of 15 years. However, the expansion of uses of power plants with reservoirs is at the exploration limit in the South, Southeast/Center-West, with only the North region with potential to be evaluated. Still, due to environmental restrictions, there is no prevision of construction of new Hydroelectrical Power Plant with reservoir in the North region. Being so, the Physical Guarantee is used to identify the future deficit risk by making a balance of supply and demand in the system. In this way, the present work proposed an analyze of Physical Guarantee system risk parameters imputed in the electrical projection model NEWAVE. So, to validate the methodology proposed the Physical Guarantee projection of the Hydroelectrical Power Plant and Thermal Power Plants that are part of the National Interconnected System were evaluated consdering the method of choosing the risk of deficit.