Kogeneracija – techniškai pažangus šilumos ir elektros energijos gamybos būdas. Elektros energija gaunama iš generatoriaus, o šilumos energija gaunama variklio aušinimo metu. Kadangi Lietuvoje elektros ir šilumos gamyba iš atsinaujinančių energijos šaltinių yra labai aktualu, darbo tikslas: suprojektuoti kogeneracinės jėainės vidaus elektros tinklą, parinkti kogeneratorių. / Cogeneration technologically advanced of heat and electricity production. It is particularly relevant for Lithuania, because there exists a strong need for heat production, the restructuring of heat and electricity networks, is changing its legal framework, the development of market relations. Undergraduate work is designed combined heat and power plant. Cogeneration plant will be used for alternative fuel: biogas which derived from the landfill. However, in order to improve the efficiency of cogeneration landfill gas is mixed with natural gas in certain proportion. Combined heat and power plant is designed according to the Republic of Lithuania laws and regulations. Heat comes from cogeneration emissions into the atmosphere in summer. It was found that in order to increase the heat recovery efficiency, not only in winter but in summer, for example to be equipped with heated vegetable production complexes.

Two studies are presented quantifying the impact of plug-in hybrid vehicles (PHEVs) on power systems. The first study quantifies this impact in terms of (a) primary fuel utilization shifts, (b) pollution shifts, and (c) total cost for consumers. The second study quantifies this impact on distribution transformers. In the first study vehicle and power system simulations are used to compute the expected power system fuels utilized to meet a projected level of power demand. The projected electric power demand includes business as usual electric load and random PHEV charging electric load. In the second study the impact on distribution transformers is quantified through a loss of life calculation. The loss of life calculation is based on distribution transformer hot-spot temperature. The hot-spot temperature is estimated using an electro-thermal distribution transformer model and is a function of the transformer currents. The transformer currents are computed using a center-tapped single phase transformer model. Random business as usual and PHEV charging electric loading is assumed.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-03-14T21:37:10Z No. of bitstreams: 1 NATÁLIA DE OLIVEIRA SANTIAGO - DISSERTAÇÃO PPGEQ 2015..pdf: 2885726 bytes, checksum: 42752aa08c69c959e3a3f1367b0e8e7a (MD5) / Made available in DSpace on 2018-03-14T21:37:10Z (GMT). No. of bitstreams: 1 NATÁLIA DE OLIVEIRA SANTIAGO - DISSERTAÇÃO PPGEQ 2015..pdf: 2885726 bytes, checksum: 42752aa08c69c959e3a3f1367b0e8e7a (MD5) Previous issue date: 2015 / Capes / O uso desenfreado de combustíveis fósseis tem causado problemas climáticos graves em todo o planeta, tais como o aquecimento global e a poluição do ar. Além de seus efeitos negativos perante a natureza, estes acarretam custos cada vez maiores de energia, devido à disponibilidade cada vez menor de reservas de petróleo, de produção e de fornecimento. Nesse contexto o hidrogênio vem a ser um vetor energético, devido a principalmente à sua alta eficiência de conversão, reciclagem e natureza não-poluente. É um combustível que não se encontra na natureza, mas ele pode ser facilmente produzido. Este trabalho apresenta a produção do hidrogênio através da eletrólise da água em meio alcalino (hidróxido de potássio, KOH) num reator de tipo bipolar usando eletrodos de espuma de níquel. A avaliação do reator eletrolítico, constituído de uma célula unitária, foi realizada pelo método estatístico de superfície de resposta visando a otimização dos experimentos através de dois planejamentos com duas variáveis dependentes: a tensão aplicada e a concentração em porcentagem de massa do KOH. A resposta é dada na forma de fluxo de hidrogênio (L/h) com o intuito de analisar o comportamento do reator em diferentes situações. A partir dos parâmetros analisados, foi encontrado o ponto ótimo de funcionamento do reator, obtido com uma concentração de 16,6% em massa de KOH e uma tensão aplicada de 2,6 V, produzindo 0,841 L/h de H2, valor máximo obtido para ambos planejamentos. / The society development is associated to the increasing use of fossil fuels, creating serious climatic problems such as global warning and air pollution. The ecological disasters, like floods and droughts, are a consequence of the increasing release of CO2 and other greenhouse gases. Besides these environmental problems, the costs relied to the extraction, production and supply of oil, are increasing due to its availability. Changes are necessary to control this situation and a way out is the use of another fuel in order to guarantee sustainability. This fuel of the future can be hydrogen, mainly due to its high conversion efficiency, recycling and non-polluting nature. It is particularly attractive as a promising substitute of the fossil fuels. This work presents the production of hydrogen by alkaline water electrolysis (potassium hydroxide, KOH) using nickel foam based electrodes. The evaluation of the electrolytic reactor, consisting of a unit cell, was performed by the statistical method of response surface experiments through two plans with two dependent variables: applied tension and KOH concentration. The response is the hydrogen flow (L/h) in order to analyze the reactor behavior in different situations. The optimum point of the reactor operation for both schedules was obtained with a concentration of 16,6% KOH and an applied voltage of 2.6 V, producing 0,841 L/h of H2.

O principal objetivo do presente projeto é verificar a interação entre a estrutura da fundação de uma máquina - um ventilador industrial - com a fonte de excitação, no caso seu próprio motor, com o intuito de identificar possível ocorrência do chamado \"fenômeno do salto\", também conhecido como Efeito Sommerfeld. Tal fenômeno é decorrente do acoplamento dinâmico entre a fonte excitadora e a estrutura durante a passagem pelos diferentes estados de ressonância, à medida que o motor é acelerado, até chegar ao regime permanente, sendo possível observar-se o mesmo fenômeno também no momento da desaceleração. Conceitua-se, neste trabalho, o modelo fonte não-ideal de energia como aquele que decorre da efetiva interação do motor da máquina com a estrutura, diferentemente do modelo de fonte ideal, aqui compreendida como sendo isenta de qualquer tipo de interação com a estrutura. Em razão do modelo adotado, a estrutura em estudo apresenta poucos graus de liberdade, definem-se as equações do movimento, tanto para o sistema ideal, como para o não-ideal, por meio da formulação de Lagrange, e obtêm-se as soluções numéricas. Conclui-se que se as Normas usuais de projeto de fundações de máquinas são empregadas em casos reais da engenharia, os fenômenos não-ideais procurados não são observados. / The main objective of the present project is to verify the interaction between the foundation structure of a machine - an industrial fan - with the excitation source, its own motor, in this case to identify possible occurrence of the so called \"jump phenomenon\", also known as Sommerfeld Effect. Such phenomenon is derived from the dynamic coupling between the excitation source and the structure during the passage through the different resonance states as the motor is accelerated until it arrives to its steady-state. It is possible to observe the same phenomenon at the moment of the deceleration. It is considered, in this work, the non-ideal source of energy model as the one that derives from the effective interaction between the motor of the machine with the structure, differently of the ideal source model, herein understood as exempted of any kind of interaction with the structure. As a consequence of the adopted model of the structure under analysis presenting few degrees of freedom, the equations of motion are defined, both for ideal and for nonideal systems, through the formulation of Lagrange, and their numerical solutions are obtained. It is concluded that if usual design Codes for machine foundations are applied to real engineering cases, the searched for phenomena are not observed.

Made available in DSpace on 2016-08-17T17:11:02Z (GMT). No. of bitstreams: 1 DISSERTACAO_ OSMAN JOSE DE AGUIAR GERUDE NETO.pdf: 613149 bytes, checksum: 997fcf93a5907fc80e81a28d149b2118 (MD5) Previous issue date: 2015-06-25 / The objectives of this study were to evaluate the intake, eeding behavior, nutrient digestibility and ruminal measures of lambs fed diets with increasing levels (0, 10, 20 and 30%, DM basis) of FS inclusion (babassu flour starch). Twenty lambs (without defined breed), uncastrated male sheep ( 21.57 ± 3.53 kg BW) were sed in a complete randomized block housed individually in covered pens (1.45m x 1.45m) with floor concreted for 50 days in feedlot trough to feed, mineralized salt and water . The diets were formulated to be isonitrogenous and consisted of 30% forage and 70% concentrate based on dry matter (DM). At the end of feedlot period, the animals were subjected to 3 days for collection of the offered food, orts and feces for calculated digestibility of nutrients. The rumen fluid as collected in the last day of experimental period for determination of pH, N-NH3 and short chain fatty acids concentration. The addition of 30% BFS decreased dry matter and crude protein intakes.The digestibility of DM, CP, OM, TC and NDF corrected for ash reduced (P < 0.05) with increasing levels of BFS. The BFS increased NFC and EE digestibilities. The variables feeding time, feed efficiency of dry matter (Fedm), feed efficiency of neutral detergent fiber (Fendf), rumination efficiency of dry matter (Redm) and mination efficiency of neutral detergent fiber (Rendf) did not change (P > 0.05) with increasing levels of BFS in feed. The feed time was lower (P < 0.05) in the control treatment. The BFS addition did not change the pH in ruminal fluid and concentrations of N-NH3, propionic acid and butyric acid. However, the concentration of acetic acid and the acetic:propionic ratio were higher (P < 0.05) with increasing BFS levels in the diet. Already concentrations of iso-butyric, valeric and iso-valeric acids decreased (P < 0.05) in the ruminal fluid of lambs with increased BFS levels in the diets. Thus, BFS characterized as a goo / Os objetivos neste trabalho foram avaliar o consumo, o comportamento ingestivo, a digestibilidade de nutrientes e os parâmetros ruminais de ovinos alimentados com dietas contendo até 30% de farinha amilácea de babaçu (FAB), com base na MS. Vinte cordeiros SPRD (sem padrão racial definido), inteiros com peso médio de 21,57 ± 3,53 kg foram utilizados em um delineamento em blocos completos casualisados alojados individualmente em baias cobertas (1,45m x 1,45m) com piso concretado contendo cocho para ração e sal mineral, e bebedouro durante 14 dias sendo 10 para adaptação e 4 para a coleta de sobras, ração ofertada e fezes, sendo ainda o último dia destinado à colheita de líquido ruminal. As dietas foram formuladas para serem isonitrogenadas, sendo constituídas por 30% de volumoso e 70% de concentrado com base na matéria seca (MS). No final do confinamento, durante três dias, coletou-se amostras do alimento ofertado, sobras e fezes para as avaliações de digestibilidade. No último dia do período experimental, coletou-se amostras do líquido ruminal para determinação do pH, N-NH3 e concentração de ácidos graxos de cadeia curta. A adição de 30% de FAB reduziu (P<0,05) o consumo de matéria seca e proteína bruta. A digestibilidade da MS, MO, PB, CHOT e FDNcp diminuíram (P<0,05) com a inclusão de FAB na dieta. A FAB aumentou a digestibilidade do EE e do CNF. O tempo de alimentação (T. Alimentação), eficiência de alimentação na matéria seca (Eams), eficiência alimentar de FDN (Eafdn), eficiência de ruminação da matéria seca (Erms) e eficiência de ruminação da FDN (Erfdn) não variaram (P>0,05) com a inclusão de FAB na ração. O tempo de ruminação (T. Ruminação) dos animais alimentados com 20% de FAB foi maior (P<0,05) em relação a 30%. Os animais do tratamento com 30% FAB permaneceram mais tempo (P<0,05) em ócio (T.Ócio). Em relação ao tempo gasto com outras atividades (T.OA), os nimais alimentados com 10% de FAB apresentaram maior (P<0,05) T.O.A. em relação aos animais do tratamento com 20% de FAB. O tempo de mastigação total (TMT) foi superior (P<0,05) para os animais com 20% de inclusão de FAB em relação aos de 30%. A adição de FAB não alterou (P>0,05) o pH do líquido ruminal, e as concentrações de N-NH3, ácido propiônico e ácido butírico. As concentrações do ácido acético e a relação entre o ácido acético e o propiônico aumentaram (P<0,05) de acordo com os teores crescentes de FAB na dieta. Entretanto, as oncentrações dos ácidos iso-butírico, valérico e iso-valérico diminuíram (P<0,05) conforme o aumento dos teores da FAB nas dietas. A FAB é uma boa alternativa de subproduto para a alimentação de cordeiros confinados, desde

O presente trabalho analisa o papel que a avaliação da conformidade de produtos, pessoas, serviços e instalações apresenta dentro do processo da construção de infraestrutura predial para a distribuição e uso dos gases combustíveis. Analisam-se as condições obrigatórias para a garantia de segurança ao consumidor final na expansão desse mercado nos países em desenvolvimento como o Brasil. Discute-se a necessidade do controle de um conjunto de objetos (elementos e agentes) diretamente vinculados a essa infraestrutura e a sua correlação com os aspectos de qualidade e segurança no setor. Parte-se do levantamento dos conceitos de avaliação da conformidade e das metodologias e critérios de seleção, aplicáveis a cenários específicos para determinação dos sistemas ideais a serem utilizados. Esse aparato conceitual é aplicado ao estudo de caso dos sistemas de avaliação da conformidade existentes no segmento do gás em países representantes dos principais blocos econômicos internacionais. Realiza-se uma análise comparativa entre os diversos cenários pesquisados, apresentando um exercício de reflexão a respeito da situação de integração dos sistemas de avaliação da conformidade para o setor do gás. O trabalho desenvolve uma análise crítica do cenário brasileiro, a partir do estabelecimento de um modelo ideal de sistema integrado de avaliação da conformidade, contemplando os principais objetos vinculados à infraestrutura para distribuição e uso do gás no segmento residencial. Avaliam-se detalhes da situação de conformidade de materiais, mão de obra, empresas instaladoras e instalações no Brasil, em contraponto ao modelo ideal e a realidade internacional. A observação da situação dos sistemas de avaliação da conformidade no cenário internacional indica a necessidade de sistemas integrados e aplicáveis aos objetos (materiais, mão de obra, serviços e instalações prediais) vinculados à infraestrutura predial para distribuição e uso residencial de gases combustíveis. Igualmente, relaciona a existência desses sistemas com a diminuição de acidentes e o aumento da segurança no setor. A análise crítica sobre a situação brasileira, em comparação com os sistemas de avaliação da conformidade ideais e a realidade internacional, revela fragilidades e dificuldades nacionais que precisam ser superadas. / This paper examines the role that the conformity assessment of products, persons, services and installations presents within the process of building infrastructure construction for gas distribution and use. Analyze the conditions required for the security guarantee to the consumer in the expansion of this market in developing countries like Brazil. It discusses the need for control of a set of objects (elements and agents) directly linked to this infrastructure and its correlation with quality and safety aspects in the industry. Part of the survey of conformity assessment concepts and methodologies and selection criteria, which apply to specific scenarios for determination of ideal systems to be used. This conceptual framework is applied to the case study of conformity assessment systems existing in the segment of the gas in countries representatives of major international economic blocs. Performs a comparative analysis between the various scenarios surveyed, showing an exercise of reflection on the situation of conformity assessment integrated systems for the gas sector. The work develops a critical analysis of the Brazilian scenario, from the establishment of an ideal model of conformity assessment integrated system, covering key subjects related to the infrastructure for distribution and use of gas in the residential segment. Assesses compliance situation details of materials, labor, installation companies and facilities in Brazil, in contrast to the ideal model and international reality. The observation of the conformity assessment systems situation in the international scenario indicates the need for integrated systems and applicable to objects (material, labor, services and facilities) related to building infrastructure for distribution and residential use of gas. Also, relates the existence of these systems with the decrease of accidents and increased security in the industry. Critical analysis on the situation in Brazil, compared with the ideals conformity assessment systems and international reality, reveals weaknesses and national problems that must to be overcome.

The thesis deals with the assessing of investment opportunity in the field of renewable natural resources. Fundamental analysis is carried out on First Solar which is a company producing solar modules. Thus, the work is focused on the area of photovoltaics. To determine the company's value, the method of discounted cash flow is used. The overall situation of the company is analyzed by the implementation of global, industry and company analysis.

Since the last United Nations Climate Change Conference in 2015 in Paris (the COP 21), world leaders acknowledged climate change. There is no need any more to justify the switch from fossil fuel-based to renewable energy sources. Nevertheless, this transition is far from being straightforward. Besides technologies that are not yet mature -- or at least not always financially viable in today's economy -- the power grid is currently not ready for a rapid and massive integration of renewable energy sources. A main challenge for the power grid is the inadequacy between electric production and consumption that will rise along with the integration of such sources. Indeed, due to their dependence on weather, renewable energy sources are intermittent and difficult to forecast with today's tools. As a commodity, electricity is a quite distinct good for which there must be perfect adequacy of production and consumption at all time and characterized by a very inelastic demand. High shares of renewable energy sources lead to high price volatility and a higher risk to jeopardize the security of supply. Additionally, the switch to renewable energy sources will lead to an electrification of loads and transportation, and thus the emergence of new higher-consumption loads such as electric vehicles and heat pumps. These new and higher-consumption loads, combined with the population growth, will cause over-rated power load increases with less predictable load patterns in the future.This work focuses on issues specific to the distribution power grid in the context of the current energy transition. Traditional low-voltage grids are perhaps the most passive circuits in power grids. Indeed, they are designed primarily using a fit and forget approach where power flows go from the distribution transformer to the consumers and no element has to be operated or regularly managed. In fact, low-voltage networks completely lack observability due to very low monitoring. The distribution grid will especially undergo drastic changes from this energy transition. Distributed sources and new high-consumption -- and uncoordinated -- loads result in new power flow patterns, as well as exacerbated evening peaks for which it is not designed. The consequences are power overloads and voltage imbalances that deteriorate grid components, such as a main asset like the medium-to-low voltage transformer. Additionally, the distribution grid is characterized by end-users that pay a price for electricity that does not reflect the grid situation -- that is, mostly constant over a year -- and allow little to no actions on their consumption.These issues have motivated authorities to propose a global approach to ensure security of electricity supply at short and medium-term. The latter requires, among others, the development of demand response programs that encourage users to take advantage of load flexibility. First, we propose adequate electricity pricing structures that will allow users to unlock the potential of such demand response programs; namely, dynamic pricings combined with a prosumer structure. Second, we propose a fast and robust two-level optimization, formulated as a mixed-integer linear program, that coordinates flexible loads. We focus on two types of loads; electric vehicles and heat pumps, in an environment with solar PV panels. The lower level aims at minimizing individual electricity bills while, at the second level, we optimize the power load curve, either to maximize self-consumption, or to smoothen the total power load of the transformer. We propose a parametric study on the trade-off between only minimizing the individual bills versus only optimizing power load curves, which have proven to be antagonist objectives. Additionally, we assess the impact of the rising share of flexible loads and renewable energy sources for scenarios from today until 2050. A macro-analysis of the results allows us to assess the benefits of load flexibility for every actor of the distribution grid, and depending on the choice of a pricing structure. Our optimization has proved to prevent evening peaks, which increases the lifetime of the distribution transformer by up to 200%, while individual earnings up to 25% can be made using adequate pricings. Consequently, the optimization significantly increases the power demand elasticity and increases the overall welfare by 10%, allowing the high shares of renewable energy sources that are foreseen. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

Nowadays, the number of applications which need more than one power source is increasing. Distributed generating systems or micro-grid systems normally use more than one power source or more than one kind of energy source. Also, to increase the utilization of renewable energy sources, diversified energy source combination is recommended. For example, a wind-photovoltaic generating system, a combination of a wind generator and photovoltaic array, can give a greater degree of freedom when choosing the install location. The combination of more power sources and diversified power sources makes it possible to obtain higher availability in a power system. A parallel connection of converters has been used to integrate more than one energy source in a power system. However, a multiple-input converter (MIC) can generally have the following advantages compare to a combination of several individual converters; (1) cost reduction, (2) compactness, (3) more expandability and (4) greater manageability. First, this research suggests MIC topology comparison criteria that can be used as a decision guide for choosing a MIC topology depending on the application. Even though there are some MIC topology classification methods such as by the kind of combining methods, the classification methods are not enough to choose one particular topology. The comparison criteria presented in this dissertation are practical enough to decide which topology is suitable and should be chosen. Second, a new MI modified inverse Watkins-Johnson converter (MIMIWJC) without a coupled inductor is proposed. The circuit configuration of this converter and its operation principles are described, including the open-loop and closed-loop circuit. For control purposes, a small signal model of the proposed converter is developed using Middlebrook’s extra element theorem. In addition, two possible control methods are introduced in this dissertation. Finally, the theoretical analysis of the proposed converter is verified with simulations and experiments. / text

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-03-15T16:40:52Z No. of bitstreams: 1 ALDREANY PEREIRA DO NASCIMENTO - DISSERTAÇÃO PPGEQ 2016..pdf: 4384493 bytes, checksum: 8cf20c9f79749f12b562389c82ec5d3f (MD5) / Made available in DSpace on 2018-03-15T16:40:52Z (GMT). No. of bitstreams: 1 ALDREANY PEREIRA DO NASCIMENTO - DISSERTAÇÃO PPGEQ 2016..pdf: 4384493 bytes, checksum: 8cf20c9f79749f12b562389c82ec5d3f (MD5) Previous issue date: 2016-10-30 / Capes / A crise do petróleo juntamente com a grande necessidade de novas fontes de energias sustentáveis leva ao desenvolvimento de tecnologias mais limpas e eficientes. Neste contexto, as células a combustível aparecem como uma das soluções promissoras para a geração de energia elétrica, tendo como produto da reação, basicamente água e calor. Este trabalho de dissertação consiste na caracterização de uma célula a combustível PEM (Polymer Electrolyte Membrane) alimentada com hidrogênio e ar para a conversão de energia elétrica da energia química contida no gás hidrogênio. A célula a combustível utilizada é de potência nominal de 1 kW, constituída por 72 células ligadas em série com um sistema de controle próprio. A caracterização é feita através da utilização de uma carga resistiva configurável com base num microcontrolador. A partir dos parâmetros registrados (corrente e tensão), a curva de polarização, a densidade de corrente e a eficiência foram calculadas com base nos sistemas de curto circuito ligado e desligado (SCU: ON e SCU: OFF, respectivamente). Os resultados mostram uma potência máxima de saída de aproximadamente 623 W (37,09 V, 16,78 A), e uma densidade de corrente de 209,75 mA/cm2, com uma eficiência operacional em torno de 42 %, com o sistema de SCU: OFF. Para o sistema SCU: ON a potência máxima de saída é em torno de 664 W (39,10 V, 17,81 A) com densidade de corrente de 222,62 mA/cm2 e uma eficiência operacional de 44 %. O sistema de carga variável mostrou-se satisfatório para testar a célula, com um desvio entre a potência nominal e a real inferior a 20 %. Os relativamente baixos valores de eficiência do sistema (<20 %) são explicados pelo tempo de vida da célula. / The use of new sustainable energy sources is dependent on the development of clearer and more efficient technologies. Therefore, the fuel cells appear like a promising solution for the electrical energy generation, since that the reaction products are water and heat. This work plans to characterize a polymer electrolyte membrane fuel cell, feeding with hydrogen and air. The tested 1 kW nominal power fuel cell is constituted by 72 cells connected in serial. The characterization is made using a variable resistive charge system. It comprises 64 resistors (20 W) together with blowers for cooling. From the electrical parameters (voltage and current), the polarization curve, the current density and the efficiency of the fuel cell were calculated, with the short-circuit system on and off (SCU: ON and SCU: OFF). A maximum output power of 623 W (37.09 V and 16.78 A), with a current density of approx. 209.75 mA/cm2 and an efficiency around 42 % are obtained when the SCU is OFF. With the SCU: ON, the values are 664 W (39.10 V and 17.81 A), 222.62 mA/cm2 and 44 %, respectively. The results show that the resistive charge system is appropriate to test this kind of fuel cell. The low global efficiency values (< 20 %) can be explained by the fuel cell age.