The topic of the thesis is biogas stations - renewable energy sources. This thesis focuses on energy from biomass which is generated inside stations, and on appropriate use of energy. It deals with thermal energy that is produced as a waste product inside the biogas stations. The main objective is to evaluate the effectiveness of the biogas stations as a source of heat for the municipalities in southern Bohemian and create evaluation criteria of suitability of using heat from biogas stations in specific communities.

Made available in DSpace on 2016-08-17T14:53:21Z (GMT). No. of bitstreams: 1 Sergio Augusto.pdf: 2350058 bytes, checksum: 7c3c67925b0b27a77105c3cb0799c4e6 (MD5) Previous issue date: 2012-05-04 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / This work provides a framework to obtain the optimal bidding strategy for a GENCO in long-term electricity auction. The tool is based on intelligent techniques for optimizing the proposed Utility Function. The goal is to find the optimal strategy that maximizes the expected payoff of GENCO and simultaneously minimize the risks. The risks are modeled by two classical metrics: the Variance (Portfolio Theory) and Value at Risk (VaR). The proposed methodology is applied to auctions for long-term forward contracts, such that used in the Brazilian power system for buying and selling energy in the regulated market. The Bidding Strategy is formed through a Supply Curve which relates the optimal amount of energy to different offer prices. Thus, it allows the GENCO define the best bid (offer) for a given offer price. The proposed approach is validated for three test cases: First, concerning the variation of generation and price of energy scenarios for evaluation of the bidding strategy and the GENCOS risk perception; The second, consider a cascade hydro-term system for evaluation of MRE; and The third, considers the northeastern Brazilian subsystem where the supply curve is formed for the CHESF company's power plants portfolio. The results show how the offer may be changed according the variation of the spot prices and physical generation and demonstrate the efficacy of meta-heuristics proposed to optimize the supply model. / Este trabalho apresenta uma ferramenta de auxílio e suporte à tomada de decisões na formação de estratégias de oferta para agentes geradores (GENCOS) participantes de leilões de eletricidade de longo-prazo. A ferramenta é baseada em técnicas inteligentes para a otimização da Função de Utilidade proposta média-risco . O objetivo é encontrar a Estratégia Ótima que maximize o retorno esperado da GENCO e, simultaneamente, minimize os riscos relacionados às incertezas no montante de energia produzida e no preço spot, modelados por duas métricas clássicas de risco: a Variância (teoria dos portfólios) e o Valor em Risco (VaR). A abordagem proposta é aplicada ao mercado brasileiro de eletricidade, especificamente, ao ambiente de Leilões de Energia Existente na categoria Quantidade de Energia, tais quais os leilões aplicados pelo órgão regulador brasileiro para compra e venda de energia no mercado regulado. Sugere-se aqui a formação de uma Curva de Oferta que relacione a quantidade de energia ótima para diferentes preços de oferta. E, deste modo, permita a GENCO definir qual o melhor lance (oferta) para dado preço de oferta durante o processo do leilão. Para a avaliação da abordagem foram utilizados três casos testes: O primeiro considera cenários de geração física e preço de energia a fim de avaliar a estratégia de oferta e a percepção ao risco de contratação da GENCO quanto à variação de tais cenários; o segundo, considera um sistema em cascata onde é possível observar o efeito do Mecanismo de Realocação de Energia (MRE) sobre a oferta das GENCOS; e o terceiro considera o subsistema nordeste brasileiro onde a curva de oferta é formada para o portfólio de usinas pertencentes à empresa CHESF. Os resultados demonstram como a oferta de energia pode ser alterada de acordo com cenários de oferta gerados e comprovam a eficiência da meta-heurística proposta para otimização do modelo de oferta.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-04-06T14:20:59Z No. of bitstreams: 1 israelfilipelopes.pdf: 3821077 bytes, checksum: 03973b1d4356ce4b46316762af40ac71 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-04-24T03:51:36Z (GMT) No. of bitstreams: 1 israelfilipelopes.pdf: 3821077 bytes, checksum: 03973b1d4356ce4b46316762af40ac71 (MD5) / Made available in DSpace on 2016-04-24T03:51:36Z (GMT). No. of bitstreams: 1 israelfilipelopes.pdf: 3821077 bytes, checksum: 03973b1d4356ce4b46316762af40ac71 (MD5) Previous issue date: 2013-02-26 / Este trabalho apresenta um estudo sobre transferência de energia elétrica sem contato para carregamento de baterias de veículos autônomos subaquáticos (AUV - Autonomous Underwater Vehicles) utilizando transformadores de núcleo separado (TNS). Inicialmente, é feito um projeto para construção de um transformador de núcleo separado. Posteriormente, são desenvolvidas as equações que modelam o funcionamento do transformador, com base em seu circuito elétrico equivalente. Em seguida, o trabalho propõe uma alternativa para estimar os parâmetros do circuito equivalente do transformador operando com valores de entreferro diferentes, validando seu modelo matemático aproximado com simulações realizadas no software PSIM, versão 9.0. Com o modelo matemático do TNS, é feita uma avaliação da sua capacidade de transferência de energia, mostrando que, em virtude do entreferro, o transformador apresenta baixa eficiência e baixos valores de tensão de saída. Nesse sentido, metodologias para compensar os efeitos de queda de tensão na impedância de dispersão, bem como aumentar a eficiência do transformador, são investigadas introduzindo-se capacitâncias no circuito elétrico equivalente e variando-se a frequência de operação. Aplicando os resultados dessa metodologia de otimização, é mostrado, por meio de experimentos em laboratório, que o TNS é capaz de transmitir energia através de um entreferro de 10 mm, atendendo às condições de tensão e potência da carga, com eficiência relativamente elevada. Em seguida, é feito um experimento com água do mar a fim de verificar a aplicabilidade do TNS em veículos subaquáticos. Por fim, é apresentada uma simulação digital realizada no software PSIM, versão 9.0, com um conversor c.c./c.c. controlador de carga para o sistema de carregamento de bateria. Os resultados obtidos demonstram o funcionamento do sistema, verificando a metodologia para estimativa do modelo e a metodologia de otimização do TNS. / This work presents a study on contactless electrical energy power transfer for charging batteries of autonomous underwater vehicles (AUV - Autonomous Underwater Vehicles) using transformers with separated core (TNS). Initially, a project is made for building a transformer with separated core. After, the equations that model the operation of the transformer, based on its electrical equivalent circuit, are developed. Then, the work proposes an alternative to estimate the parameters of the equivalent circuit of the transformer operating with different gap values, validating its mathematical model with simulations in PSIM software, version 9.0. With the mathematical model of TNS, an evaluation of its ability to transfer power is made, showing that, because of the air gap, the transformer has a low efficiency and low output voltage. Therefore, methodologies to compensate for the effects of voltage drop in the leakage impedance and increase the efficiency of the transformer are investigated by introducing capacitances in the equivalent circuit and varying the of operating frequency. Applying the results of optimization methodology is shown, through laboratory experiments, that the TNS is capable of transmitting power through an air gap of 10 mm, given the voltage and load power conditions, with relatively high efficiency. Then, an experiment is done with seawater in order to verify the applicability of TNS for underwater vehicles. Finally, the work presents a simulation in PSIM with a d.c./d.c. charge controller for battery. The results demonstrate the operation of the system, verifying the methodology for estimation of the model and optimization methodology of TNS.

This master thesis deals with analysis of battery mass using x-ray spectral microanalysis. For the measurement two scanning electron microscopes equipped with energy dispersive x-ray spectroscopes were used. Appropriate examples were prepaired by standard method. Then elemental analysis was performed with changing conditions of measurement. Two programs were used for spectrums evaluation and in the end the size of errors was observed for every conditions.

The goal of this project is to test the possibility to connect the Cogenerational generation of power 138 MW (still in the development stage) to the control room 110 kV in Prostejov production. This merge would product the electrical energy as well as the heat energy for all local area. In this dissertation we will be considering the solution of the steady state (stationary state) of system with the voltage level of 110kV, as well as the influence of the generation of power on this system, there by the suggesting a connection. The Congenerational production indicates higher effectiveness in the transformation of energy during primary production process due to the production of heat energy as well as the electrical energy from the primary power sources. In our country, as well as around the world, commonly used fuels are fossil fuels- coal, crude oil, and gas. As the demand for energy grows, those supplies are slowly running out. Not to mention that those fuels have a negative environmental impact. They are a source of carbon, which causes damage to the atmosphere and leads to global warming. Power plants which do not produce carbon are much safer for the environment, and much more productive. However, the residue of this energy is challenging to dispose of. Nuclear energy has common attributes with renewing the sources of energies that are extremely friendly to our environment. Nuclear power plants also produce enough energy and with the usage of Fourth generation reactors, they will be able to recycle the nuclear fuels. Today, more importance is put on renewing sources which are more gentle for the environment. In the near future, CEZ Company, the largest producer of electric energy is planning to use water energy. Water energy comes from water plants or dams. Other ecological forms of energy include geothermal and solar energies. These two types of energy are not as applicable for our geographical position. Geothermal energy is commonly used on islands where there is an abundance of natural hot springs. The most discussed source of energy is bioenergy. It uses natural wood sources, recycled wood products, and applies bioenergy as a main source for thermal power plants.

Photovoltaic in the Czech Republic has gone through significant development during last few years. The thesis describes physical principle of converting solar energy into electrical energy using photovoltaic cells. Photovoltaic power plant is a set of technologic components connected together to utilize solar energy and convert it into electric energy that could be distributed to electric power network. Review of the photovoltaic development in the Czech Republic and the list of the biggest operational photovoltaic power plants present important data for assessment of the current status of photovoltaic technology in the Czech Republic. Chapter operations and maintenance of photovoltaic power plants summarizes the most common causes of failures and presents diagnostic tools for service requests. Due to legislative changes, hybrid photovoltaic power plants construction has been prioritized as it is economically more efficient now. Construction of new hybrid photovoltaic power plant was assessed analytically using SWOT analysis that evaluates strong and weak sides of the projects in comparison with opportunities and threats of construction. After evaluation of obtained data the next steps of the hybrid photovoltaic power plant’s construction plan are proposed. The first part of hybrid photovoltaic power plant design contains PVGIS program's data evaluation, which provides sunlight intensity information for specified area. Obtained data were used in the second part of the design to determine proper components selection for family house hybrid photovoltaic power plant. Finally the economic view of the design and return of investments were assessed.

<p>  </p> <p>Organic-inorganic halide perovskites are at the brink of commercialization as the next generation of light-absorbing materials for solar energy harvesting devices. Perovskites have large absorption coefficients, long charge-carrier lifetimes and diffusion lengths, and a tunable absorption spectrum. Furthermore, these materials can be low-temperature solution-processed, which transfers to low-cost manufacturing and cost-competitive products. The remarkable material properties of perovskites enable a broad product-market fit, encompassing traditional and new applications for solar technology. Perovskites can be deposited on flexible substrates for flexible solar cells, applied in thermochromic windows for power generation and building cooling, or tuned for tandem solar cell application to include in high-performance solar panels. However, perovskites are intrinsically unstable, which has so far prevented their commercialization. Despite large research efforts, including over two thousand publications per year, perovskite solar cells degrade in under one year of operation. In a saturated research field, new ideas are needed to inspire alternative approaches to solve the perovskite stability problem. In this dissertation, we detail research efforts surrounding the concept of a self-healing perovskite solar cell.</p> <p>     A self-healing perovskite solar cell can be classified with two distinctions: mechanically healing and molecularly healing. First, mechanically self-healing involves the material’s ability to recover its intrinsic properties after mechanical damage such as tares, lacerations, or cracking. This type of healing was unique to the organic polymer community and ultra-rare in semiconducting materials. By combining a self-healing polymer with perovskite material, we developed a self-healing semiconducting perovskite composite material which can heal using synergistic grain growth and solid-state diffusion processes at slightly elevated temperatures. The material is demonstrated in flexible solar cells with improved bending durability and a power conversion efficiency reaching 10%. The addition of fluidic polymer enables macroscopic perovskite material movement, which is otherwise brittle and rigid. The results inspire the use of polymer scaffolds for mechanically self-healing solar cells.</p> <p>     The second type of healing, molecular healing, involves healing defects within the rigid crystal domains resulting from ion migration. The same phenomenon which leads to device degradation, also assists the recovery of the device performance after resting the device in the dark. During device operation, perovskite ions diffuse in the perovskite lattice and accumulate at the device interfaces where they undergo chemical reactions or leave the perovskite layer, ultimately consuming the perovskite precursors. The photovoltaic performance can be recovered if irreversible degradation is limited. Ideally, degradation and recovery can match day and night cycling to dramatically extend the lifetime of perovskite solar cells. In this dissertation, we introduce the application of chalcogenide chemistry in the fabrication of perovskite solar cells to control the thin film crystallization process, ultimately to reduce defects in the perovskite bulk and introduce surface functionality which extends the device stability. This new strategy will help improve molecularly self-healing perovskite solar cell by reducing irreversible degradation. Lastly, we present a few other new ideas to inspire future research in perovskite solar cells and assist in the commercialization of the next generation of photovoltaics.</p>

<p>This work focuses on the collection and analysis of Lithium-ion battery operational and temperature data during nail penetration testing through two different experimental approaches. Raman spectroscopy, machine learning, and internal temperature sensors are used to collect and analyze data to further investigate the effects on cell operation during and after nail penetrations, and the feasibility of using this data to predict future performance.</p> <p><br></p> <p>The first section of this work analyzes the effects on continued operation of a small Lithium-ion prismatic cell after nail penetration. Raman spectroscopy is used to examine the effects on the anode and cathode materials of cells that are cycled for different amounts of time after a nail puncture. Incremental capacity analysis is then used to corroborate the findings from the Raman analysis. The study finds that the operational capacity and lifetime of cells is greatly reduced due to the accelerated degradation caused by loss of material, uneven current distribution, and exposure to atmosphere. This leads into the study of using the magnitude and corresponding voltage of incremental capacity peaks after nail puncture to forecast the operation of damaged cells. A Gaussian process regression is used to predict discharge capacity of different cells that experience the same type of nail puncture. The results from this study show that the method is capable of making accurate predictions of cell discharge capacity even with the higher rate of variance in operation after nail puncture, showing the method of prediction has the potential to be implemented in devices such as battery management systems.</p> <p><br></p> <p>The second section of this work proposes a method of inserting temperature sensors into commercially-available cylindrical cells to directly obtain internal temperature readings. Characterization tests are used to determine the effect on the operability of the modified cells after the sensors are inserted, and lifetime cycle testing is implemented to determine the long-term effects on cell performance. The results show the sensor insertion causes a small reduction in operational performance, and lifetime cycle testing shows the cells can operate near their optimal output for approximately 100-150 cycles. Modified cells are then used to monitor internal temperatures during nail penetration tests and how the amount of aging affects the temperature response. The results show that more aging in a cell causes higher temperatures during nail puncture, as well as a larger difference between internal and external temperatures, due mostly to the larger contribution of Joule heating caused by increased internal resistance.</p>

<h4>A generalized physics-based modeling framework is presented to analyze: (a) the effects of temperature on identified degradation mechanisms, (b) interfacial debonding processes, including deterministic and stochastic mechanisms, and (c) establishing model performance benchmarks of electrochemical porous electrode theory models, as a necessary stepping stone to perform valid battery degradation analyses and designs. Specifically, the effects of temperature were incorporated into a physics-based, reduced-order model and extended for a LiCoO₂ -graphite 18650 cell. Three dimensionless driving forces were identified, controlling the temperature-dependent reversible charge capacity. The identified temperature-dependent irreversible mechanisms include homogeneous SEI, at moderate to high temperatures, and the chemomechanical degradation of the cathode at low temperatures. Also, debonding of a statistically representative electrochemically active particle from the surrounding binder-electrolyte matrix in a porous electrode was modeled analytically, for the first time. The proposed framework enables to determine the space of C-Rates and electrode particle radii that suppresses or enhances debonding and is graphically summarized into performance–microstructure maps where four debonding mechanisms were identified, and condensed into power-law relations with respect to the particle radius. Finally, in order to incorporate existing or emerging degradation models into porous electrode theory (PET) implementations, a set of benchmarks were proposed to establish a common basis to assess their physical reaches, limitations, and accuracy. Three open source models: dualfoil, MPET, and LIONSIMBA were compared, exhibiting significant qualitative differences, despite showing the same macroscopic voltage response, leading the user to different conclusions regarding the battery performance and possible degradation mechanisms of the analyzed system.</h4>

The thesis discuses an integration of photovoltaic power stations to electric network. The first part describes connecting conditions of small sources to distribution system, including administrative requirements, feasibility study, and requirements to the energy meters, measuring, control devices, switching devices and protection. The second part is aimed to describe problems of the photovoltaic system. Solar radiation generating and reducing of its intensity incident upon the earth surface are described in this part. The quantum of produced electric power depends on climatic conditions in the fixed area, seasons, etc. This work also discusses the types of photovoltaic cells and their actual efficiency. Inverters are further important components of the photovoltaic system. The parameters of the inverters have a great influence on the total actual efficiency of the photovoltaic system. Different methods of the photovoltaic panels’ connection with the inverters and their advantages and disadvantages are also mentioned. The supporting structure of the photovoltaic panels and eventually transformer are further important components of photovoltaic system. The work also analyze the methods of connection of the photovoltaic power station to distributive low voltage and medium voltage network, electric energy accumulation and possibilities of the sale of produced electric energy. The large number of the connected photovoltaic power stations has negative influences to electric network. The third part contains the design of a photovoltaic power plant with a capacity of 516,24 kWp on the scoped area in southern Bohemia. The project documentation for the location where the power plant is designed is also made. It contains the design of photovoltaic panels, the design of the inverters to get an optimal power load. This part also contains a calculation of the photovoltaic system losses and the design of transformer and the cable junction calculation of the distributive system. The feasibility study of the power plant connected to distributive system is also conducted. Its delivery rate will be connected to the distribution point Řípov (110/22 kV). The calculation results show us that this photovoltaic power plant can be linked to the distribution system. The final part of this paper contains an economic estimate of the photovoltaic power plant operating and the calculation of the return. An Economic return is influenced by the wide range of values that affect the total return rate. The calculation of an operating economy is made for several variants. The return rate in refer to contemporary redemption price for 2010 with no consideration for a bank loan is 7 years. If we consider the bank loan it would be 12 years. The penetrative reduction of the redemption price is expected for 2011. Calculation works with the decline of 30 %. It would extend the rate of return to 11 years without a bank loan or to 22 years with the bank loan. The bank loan is considered to cover 80 % of the investment.