Com a crescente busca por fontes energéticas renováveis alternativas aos combustíveis fósseis, o uso de biomassa lignocelulósica, como bagaço de cana-de-açúcar e serragem de eucalipto, surge como uma alternativa para a produção de etanol de segunda geração. Porém, são necessários pré-tratamentos para facilitar a ação das enzimas sobre a biomassa. Entre os métodos de pré-tratamentos, o biológico tem sido estudado, por não demandar o uso de químicos e altos custos energéticos, apresentar condições brandas de processo e não levar à formação de compostos inibidores às etapas posteriores. No presente trabalho, bagaço de cana-de-açúcar e serragem de eucalipto foram pré-tratados por diferentes espécies de basidiomicetos. As amostras pré-tratadas foram hidrolisadas com complexo enzimático de Peninillium echinulatum e posteriormente realizou-se a fermentação dos açúcares liberados. Com relação à produção de enzimas lignolíticas, as espécies que se destacaram em bagaço de cana-de-açúcar foram Marasmiellus palmivorus VE111, Pleurotus pulmonarius PS2001, Pleurotus albidus 88F-13, Pycnoporus sanguineus PR32 e Trametes villosa 82I6. Em serragem de eucalipto, os teores destas enzimas foram significativamente inferiores aos obtidos com as mesmas espécies em bagaço de cana-de-açúcar. Em análise de espectros de FTIR, T. villosa 82I6 e P. pulmonarius PS2001 apresentaram proporções favoráveis entre o consumo de celulose, hemicelulose e lignina em ambas as biomassas testadas. Em ensaios de hidrólise enzimática, pré-tratamento biológico por T. villosa 82I6 aumentou a digestibilidade da celulose presente na serragem de 3,7% para 42% e do bagaço de cana-de-açúcar de 12,9% para 22%. T. villosa 82I6 destacou-se, visto que, em ambas as biomassas, foi o basidiomiceto que promoveu o maior liberação de glicose na etapa de hidrólise em amostras pré-tratadas por menores tempos. Em fermentação alcoólica dos hidrolisados de ambas as biomassas pré-tratadas por T. villosa 82I6, o rendimento em etanol a partir de bagaço de cana-de-açúcar foi aumentado para 20,2±0,5 mg/g após 49 dias de tratamento, enquanto que o controle apresentava rendimento de 10,1±0,8 mg/g. O rendimento em etanol a partir de serragem de eucalipto foi aumentado para 25,5±0,7, 18,2±0,03 e 25,5±3,8 mg/g, após respectivamente 7, 28 e 42 dias de tratamento, enquanto que o controle apresentava rendimento de 6,5±0,2 mg/g. Foi demonstrado o potencial do T. villosa 82I6 como agente biológico em pré-tratamentos de biomassas lignocelulósicas e o impacto do pré-tratamento sobre as etapas subsequentes. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2017-11-30T19:22:32Z No. of bitstreams: 1 Dissertacao Caroline Hartmann.pdf: 2412511 bytes, checksum: a07736115b288116c6298b801c3ef764 (MD5) / Made available in DSpace on 2017-11-30T19:22:32Z (GMT). No. of bitstreams: 1 Dissertacao Caroline Hartmann.pdf: 2412511 bytes, checksum: a07736115b288116c6298b801c3ef764 (MD5) Previous issue date: 2017-11-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / With the growing demand for renewable energy sources as alternatives to fossil fuels, the use of lignocellulosic biomass, such as sugarcane bagasse and eucalyptus sawdust, is an alternative for the production of second generation ethanol. However, pretreatments are needed to facilitate the action of enzymes on biomass. Among the pretreatment methods, the biological has been studied, since it does not require the use of chemicals and high energy costs, to present soft conditions of process and not formation of inhibitory compounds to the later stages. In the present study, sugarcane bagasse and eucalyptus sawdust were pretreated by different basidiomycete species. The pretreated samples were hydrolyzed with enzymatic complex of Peninillium echinulatum and later the fermentation of the liberated sugars was carried out. In relation to the production of lignolytic enzymes, the species that stood out in sugarcane bagasse were Marasmiellus palmivorus VE111, Pleurotus pulmonarius PS2001, Pleurotus albidus 88F-13, Pycnoporus sanguineus PR32 and Trametes villosa 82I6. In eucalyptus sawdust, these enzymes were significantly lower than those obtained by the same species in sugarcane bagasse. In the analysis of FTIR spectra, T. villosa 82I6 and P. pulmonarius PS2001 presented favorable proportions between cellulose, hemicellulose and lignin consumption in both biomasses tested. In enzymatic hydrolysis assays, biological pretreatment with T. villosa 82I6 increased the digestibility of the pulp present in the sawdust to 42% and of the sugarcane bagasse to 22%. T. villosa 82I6 was highlighted, since in both biomass, it was the basidiomycete that promoted the highest glucose release in the hydrolysis step, in samples pretreated for shorter times. In alcoholic fermentation of the hydrolysates of both biomasses pretreated with T. villosa 82I6, ethanol yield from sugarcane bagasse was increased to 20.2±0.5 mg/g after 49 days of treatment, while the control presented yield of 10.1±0.8 mg/g. The ethanol yield from eucalyptus sawdust was increased to 25.5±0.7, 18.2±0.03 and 25.5±3.8 mg/g, respectively after 7, 28 and 42 days of treatment, while the control presented yield of 6.5±0.2 mg/g. The potential of T. villosa 82I6 as a biological agent in pretreatments of lignocellulosic biomass and the impact of pretreatment on subsequent steps has been demonstrated.

Orientador: José Manoel Balthazar / Banca: Airton Nabarrete / Banca: Angelo Marcelo Tusset / Banca: Vinicius Piccirillo / Banca: Atila Madureira Bueno / Abstract: Recently, the interest and research about energy harvesting has been increasing substantially in the technical-scientific community. With the great world demand for electrical energy, many researchers, in Brazil and in the World, have concentrated their efforts to seek new energy sources. In addition, with the technological advances is possible to use low-power consumption devices, that are, most of time, powered by a battery, which are limited energy sources having the necessity of recharging or substituting them periodically. In the energy harvesting process, the electrical energy is obtained through the conversion of mechanical energy created by a vibrating source in the environment using a transducer. Among the most common energy transduction mean, the use of piezoelectric materials has been of great interest in the energy harvesting matter due to its ease of application and its use to harvest energy in a wide range of frequencies. Vibration sources in the environment may occur in structures by vehicle traffics, a train movement, sea waves and even people. With that, the objective of this work is to study the energy harvesting using a nonlinear two-degrees-of-freedom portal frame platform with a nonlinear piezoelectric material coupled to one of its columns and externally base-excited. The nonlinear platform possesses two-to-one internal resonance between its two vibration modes. The nonlinearities of the piezoelectric material is considered as a nonlinear mathematical r... (Complete abstract click electronic access below) / Resumo: Recentemente, o interesse e a pesquisa de coleta de energia têm aumentado substancialmente no meio técnico-científico. Com a grande demanda mundial por energia elétrica, muitos pesquisadores, no Brasil e no Mundo, têm concentrado seus esforços na busca de novas fontes de energia. Além disso, com os avanços da tecnologia, é possível utilizar dispositivos de baixo consumo de energia, que são, na maioria das vezes, alimentados por uma bateria, que são fontes de energia finita havendo a necessidade da recarga ou troca periodicamente, das mesmas. No processo de coleta de energia, a energia elétrica é obtida através da conversão de energia mecânica criada por uma fonte de vibração do meio ambiente através de um transdutor. Entre os mais comuns meios de transdução de energia, o uso de materiais piezoelétricos vêm sendo de grande interesse em meio a coleta de energia devido sua facilidade de aplicação e seu uso para coleta de energia em um amplo intervalo de frequências. Fontes de vibração do meio ambiente podem ser causadas em estruturas através do movimento de veículos, um trêm, ondas do mar e até o deslocamento de pessoas. Com isso, este trabalho tem como objetivo estudar a coleta de energia utilizando uma plataforma aporticada não-linear de dois graus de liberdade contendo um material piezoelétrico não-linear acoplado a uma de suas colunas e excitado externamente em sua base. A plataforma não-linear possui ressonância interna 2:1 entre seus modos de vibrar. A não-linearidade do... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

Orientador: Percival Bueno de Araujo / Co-orientador: Bala Venkatesh / Banca: Dilson Amancio Alves / Banca: Fábio Bertequini Leão / Banca: Gideon Villar Leandro / Banca: Marcos Amorielle Furini / Resumo: Os sistemas de transmissão em todo o mundo, que foram projetados e construídos para operar, predominantemente, com geração síncrona convencional, como a geração hídrica. Entretanto, agora se faz necessária a integração de energia renovável, tais como a energia eólica e energia solar. Estes geradores de energias renováveis estão localizados em locais ricos em recursos, causando uma injeções de potência em sistemas de transmissão, submetendo-os a indevidos esforços e obrigando-os a operar em novos pontos de operação. Em muitos sistemas de transmissão, a capacidade de integração se aproximou do limite, sendo necessárias atualizações para acomodar uma maior penetração de geração eólica. Os exemplos podem ser vistas na Alemanha, Ontario (Canadá) e Texas. Nestas situações, onde as capacidades do sistema de transmissão estão próximas do limite de operação, é importante para avaliar a estabilidade de tensão, considerando (a) a geração eólica e (b) possível efeito da incerteza na previsão. Neste trabalho, é proposta uma abordagem sistemática para estabilidade de tensão. Com a utilização de um algoritmo de fluxo de potência ótimo e da construção da matriz hessiana, será determinada a relação entre as mudanças nos valores mínimos singulares do sistema Jacobiano e as mudanças na injeção de potência no barramento em tempo real. Esta relação é usada para examinar o efeito da incerteza da previsão de energia eólica na estabilidade de tensão. O método proposto é usado para estudar os efeitos da incerteza sobre a estabilidade de tensão dos sistemas 6-barras, 57-barras e 118-barras do IEEE; do Sistema Sul Brasileiro reduzido e também foi usado um sistema real 600 barras. Os resultados são detalhados nesta tese / Abstract: Transmission Systems worldwide, that were designed and built to operate with predominantly conventional synchronous generation, are advancing to integrate large amounts of renewable energy generators. These renewable generators are sited at resource-rich locations, causing a geographical shift in power injections into transmission systems, subjecting them to undue stress and making them operate in new states. In many transmission systems, capacities to integrate wind resource are exhausted or are being upgraded to accommodate higher wind generation penetration. Examples may be seen in Germany, Ontario (Canada) and Texas. In these situations, where transmission system capacities have been reached, it is important to assess voltage stability by considering (a) wind generation and (b) possible effect of uncertainty in forecast. In this work, a systematic approach of studying voltage stability is proposed. Using an optimal power flow algorithm, the Hessianmatrix of power balance equations is determined that relates changes in minimum singular values of system Jacobian to changes in bus-wise real power injections. This relationship is used to examine effect of uncertainty of wind power forecast on voltage stability. The proposed method is used to study the effects of uncertainty on system voltage stability of 6-bus, 57-bus and 118-bus IEEE and 45-bus South Brazilian test systems, for the real analyses is used 600-bus and results are reported. Considering the simplification of computation, the proposed method has a clear advantage compared to the conventional Jacobian technique using repeated OPF solutions / Doutor

Orientador: Agnelo Marotta Cassula / Coorientador: José Luz Silveira / Banca: José Antonio Perrella Balestieri / Banca: José Feliciano Adami / Banca: Edson da Costa Bortoni / Banca: Ronney Arismel Mancebo Boloy / Resumo: Sistemas Híbridos de Geração de Energia (SHGE) baseados em fontes renováveis, quando dimensionados de forma correta, apresentam menor custo de energia gerada, maior confiabilidade no fornecimento de energia, além de benefícios ambientais, comparados a sistemas baseados em uma única fonte renovável ou em fontes tradicionais de geração. No entanto, o dimensionamento deste tipo de sistema apresenta-se como uma tarefa complexa, devido à variabilidade dos recursos renováveis e da demanda de energia, além das caraterísticas não lineares de alguns dos seus componentes e a alta interação entre as variáveis do sistema. No presente trabalho propõe-se um método de otimização baseado em simulação para o dimensionamento de SHGE considerando a presença de incertezas nas variáveis de entrada. O método proposto permite dimensionar o sistema considerando aspectos econômicos, de confiabilidade e ambientais como critério de otimização, e incorporar incertezas na disponibilidade dos recursos renováveis, na demanda de energia e na indisponibilidade dos componentes sujeitos a falha. A otimização é feita por meio da metaheurística de Algoritmos Genéticos. O método de amostragem de Hipercubo Latino (LHS - Latin Hypercube Sampling) é utilizado para gerar os cenários de incerteza nos recursos renováveis e na demanda, enquanto que Simulação de Monte Carlo é empregada para gerar históricos de operação dos componentes do sistema. A metodologia de otimização baseada em simulação é aplicada a um caso de es... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: When properly design, Hybrid Power Systems (HPS) based on renewable sources, present technical, economic and environmental benefits when compared to single source-based renewable power systems or traditional source-based power systems. Nonetheless, the optimal design of HPS is a daunting task, due to the stochastic behavior of the renewable resources availability and the demand to be met, the non-linear characteristic of some of the components and the high interaction between the system variables. This study proposes a simulation-based optimization approach for dimensioning HPS considering uncertainties in the input variables. The proposed methodology allows to optimal design the system considering economic, reliability and environmental criteria, while incorporating the presence of uncertainty related to the renewable resources availability, the power demand, and the availability of the components subjected to failure. The optimization is performed by means of Genetic Algorithms. The Latin Hypercube Sampling method is used to generate uncertainty scenarios related to the renewable resources and the load, while Monte Carlo simulation is employed to generate chronological system state transition process for each component of the system. The proposed methodology was applied in a case study showing satisfactory results. The simulation-based optimization approach is especially useful for dimensioning hybrid power systems that require both optimality and robustness. However, due t... (Complete abstract click electronic access below) / Doutor

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2015. / From the electric power generation perspective, the last three decades have been characterized by sustained growth in the amount of Distributed Power Generation (DPG) systems integrated into the electric grid. This trend is anticipated to continue, especially in light of the widespread acceptance of the many benefits envisaged in the increase of renewable-based power generation. The potential for grid-integrated DPG systems to significantly contribute to electric power supply reliability has consistently attracted extensive research in recent times, although concerns continue to be raised over their adverse impact on the normal grid operation at high penetration levels. These concerns largely stem from the limited controllability of most DPG systems, which tend to exhibit large output impedance variation, and non-deterministic power output characteristics. There has therefore also been a growing need to develop effective control strategies that can enhance the overall impact of the DPG systems on the grid operation, thus improving their synergistic properties, and probably also enabling an even higher penetration level into the utility grid. In line with this identified need, this thesis discusses the modeling and controller design for an inverter-based DPG system with the capability to effectively operate both in grid-connected and autonomous (i.e. independent of the utility grid) operational modes. The dual-mode operation of the DPG is made possible by incorporating into the inverter interface control scheme the means to ensure seamless transition of the DPG between the grid-connected and autonomous modes of operation. The intention is to have a grid-integrated inverter-based DPG system whose operation approximates that of an online Uninterruptible Power Supply (UPS) system, in that it is able to sustain power supply to the local load in the absence of the grid supply, which would be desirable for critical loads, for which the level of power supply reliability guaranteed by the grid often falls short of the requirements. The work developed in this thesis considers three of the aspects associated with grid-integrated DPG systems that are equipped with autonomous-mode operation capability.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology. / Distributed Generation systems based on renewable energy sources, such as wind or solar are mostly intermittent sources, due to their dependency on the weather, whereas those based on other primary energy sources are non-intermittent. All of them are specially designed to be integrated into distribution systems, in order to improve the power demand of consumers. In the last few decades of the twentieth century, several different factors have played a key role in increasing interest in systems. Distributed Generation (DG) is gaining more and more attention worldwide as an alternative to large-scale central generating stations. The aim of this research project is to investigate the contribution of distributed generation in fault current level in a power distribution system. The simulation results indicate that DG can have a positive or negative impact, on the fault current level in distribution network systems. The DG location and size affect the fault level. The second aim of this research was to suggest a model-based method for design, and implementation of a protection scheme for power distribution systems, by establish algorithms in a hardware environment. The overcurrent relay was chosen for the model development because it is considered a simple and popular protection scheme, and it is a common scheme in relaying applications. The proposed relay model was tested for fault conditions applied on a simple power system in different scenarios. The overcurrent relay model was implemented in MATLAB/Simulink, by using MATLAB programming languages and the SimPowerSystem (SPS) Tool. MATLAB/SIMULINK software is applicable to the modelling of generation, transmission, distribution and industrial grids, and the analysis of the interactions of these grids. This software provides a library of standard electrical components or models such as transformers, machines, and transmission lines. Therefore, the modelling and simulations are executed using MATLAB/Simulink version 2014b

Thesis (MTech (Electrical, Electronic and Computer Engineering))--Cape Peninsula University of Technology, 2015. / The growing interest in the use of solar energy to mitigate climate change, reduction in the cost of PV system and other favourable factors have increased the penetration of the PV(Photovoltaic) systems in the market and increase in the worldwide energy supply. The main component in a DG is a smart inverter connected in a grid-tied mode which serves as a direct interface between the grid and the RES (Renewable Energy System). This research work presents a three phase grid-tied inverter with active and reactive power control capabilities for renewable energy sources (RES) and distributed generators (DG). The type of the inverter to be designed is a Voltage Source Inverter (VSI). The VSI is capable of supplying energy to the utility grid with a well regulated DC link at its input. The solution this project proposes is an implementation of the designed filter to effectively reduce the harmonics injected into the grid to an acceptable value according to standards and also an approach to control the real and reactive power output of the inverters to help solve the problems of instability and power quality of the distribution system. The design, modelling and simulation of the smart inverter system is performed in MATLAB/SIMULINK software environment. A 10 kW three-phase voltage source inverter system connected to the utility grid was considered for this research. Series of simulations for the grid-connected inverter (GCI) model was carried out using different step changes in active and reactive power references which was used to obtain the tracking response of the set power references. The effectiveness of the control system which was designed to track the set references and supply improved power quality with reduced current ripples has been verified from the simulation results obtained.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2016. / South Africa has raised concerns regarding the development of renewable energy sources such as wind, hydro and solar energy. Integration of a combined photovoltaic and thermal system was considered to transform simultaneous energy into electricity and heat. This was done to challenge the low energy efficiency observed when the two solar energy conversion technologies are employed separately, in order to gain higher overall energy efficiency and ensure better utilization of the solar energy. Therefore, the notion of using a combined photovoltaic and thermal system was to optimize and to improve the overall PV panel efficiency by adding conversion to thermal energy for residential and commercial needs of hot water or space heating or space cooling using appropriate technology. The PV/T model constructed using water as fluid like the one used for the experimental work, presented a marginal increase in electrical efficiency but a considerable yield on the overall PV/T efficiency, because of the simultaneous operation by coupling a PV module with a thermal collectors.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2016. / The generation of municipal solid waste has increased significantly due to the exponential population growth and it has become a global issue. Gasification technology, an alternative method for waste treatment is a thermochemical process where carbon-based material are exposed to an environment deprived in oxygen, was used for this project. The aim of this thesis is to study the gasification of plastic waste which is a potential alternative energy source using infrared heaters. To achieve this goal, fundamental studies have been numerically and experimentally conducted for an infrared gasifier and subsequently establishing the temperature profile for gasification using a small scale reactor. A detailed study on low density polyethylene was conducted using Infrared Spectrometry and thermal decomposition techniques such as Thermogravimetry and Differential Scanning Calorimetry were performed to establish the temperature at which plastic pellets sample used for this research gasify. The gasification behaviour of pelletized low density polyethylene (plastic pellets) was tested and three case studies were done to evaluate the most suitable temperature profile for the reactor to gasify the low density polyethylene at high temperature for less amount of time. Subsequently, the reactor model was simulated and results validate the use of reactor at an optimum temperature of 800 °C for a gasification process with less residue content. The reactor designed for this research is fully functional and validates the temperature behaviour predicted during simulation. The experimental results show infrared heaters are suitable for gas production using this gasification process.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2017. / Fuel cell (FC) technology is one of the most sought-after renewable energy technology. However, the output voltage of FC stacks is inherently unstable; as such, it is of little or no use for most power supply applications. In addition to the unstable output voltage, FC stacks are susceptible to high current ripple, which can reduce the system’s life expectancy. The work carried out in order to stabilise the output voltage, and to reduce the current ripple of FC stacks involves a review of some existing converter topologies used for power conditioning units (PCUs), modelling, design, control and simulation of different converter topologies and the experiment of the prototype circuit for the interleaved boost voltage multiplier (IBVM) converter topology. In the process to stabilise the stack output voltage and to reduce the stack output current ripple, it is also required to improve the system response to load changes. This work presents results that show that system works, with the voltage stabilised, the stack output current ripple reduced and the response time reduced. A relative evaluation of the dynamic behaviour of four converter topologies in power conditioning units is carried out, and these are the isolated current-fed full-bridge (ICFFB) converter, the boost converter, the sepic converter and the IBVM converter. The simulation results of the four topologies show that the output voltage of a PEMFC stack was stabilised, and that the IBVM topology is a better topology compared to the others, especially when it comes to reducing the stack current ripple.