Doctor of Philosophy (PhD) / This thesis investigates ion energy distributions (IEDs) during plasma immersion ion implantation (PIII). PIII is a surface modification technique where an object is placed in a plasma and pulse biased with large negative voltages. The energy distribution of implanted ions is important in determining the extent of surface modifications. IED measurements were made during PIII using a pulse biased retarding field energy analyser (RFEA) in a capacitive RF plasma. Experimental results were compared with those obtained from a two dimensional numerical simulation to help explain the origins of features in the IEDs. Time resolved IED measurements were made during PIII of metal and insulator materials and investigated the effects of the use of a metal mesh over the surface and the effects of insulator surface charging. When the pulse was applied to the RFEA, the ion flux rapidly increased above the pulse-off value and then slowly decreased during the pulse. The ion density during the pulse decreased below values measured when no pulse was applied to the RFEA. This indicates that the depletion of ions by the pulsed RFEA is greater than the generation of ions in the plasma. IEDs measured during pulse biasing showed a peak close to the maximum sheath potential energy and a spread of ions with energies between zero and the maximum ion energy. Simulations showed that the peak is produced by ions from the sheath edge directly above the RFEA inlet and that the spread of ions is produced by ions which collide in the sheath and/or arrive at the RFEA with trajectories not perpendicular to the RFEA front surface. The RFEA discriminates ions based only on the component of their velocity perpendicular to the RFEA front surface. To minimise the effects of surface charging during PIII of an insulator, a metal mesh can be placed over the insulator and pulse biased together with the object. Measurements were made with metal mesh cylinders fixed to the metal RFEA front surface. The use of a mesh gave a larger ion flux compared to the use of no mesh. The larger ion flux is attributed to the larger plasma-sheath surface area around the mesh. The measured IEDs showed a low, medium and high energy peak. Simulation results show that the high energy peak is produced by ions from the sheath above the mesh top. The low energy peak is produced by ions trapped by the space charge potential hump which forms inside the mesh. The medium energy peak is produced by ions from the sheath above the mesh corners. Simulations showed that the IED is dependent on measurement position under the mesh. To investigate the effects of insulator surface charging during PIII, IED measurements were made through an orifice cut into a Mylar insulator on the RFEA front surface. With no mesh, during the pulse, an increasing number of lower energy ions were measured. Simulation results show that this is due to the increase in the curvature of the sheath over the orifice region as the insulator potential increases due to surface charging. The surface charging observed at the insulator would reduce the average energy of ions implanted into the insulator during the pulse. Compared to the case with no mesh, the use of a mesh increases the total ion flux and the ion flux during the early stages of the pulse but does not eliminate surface charging. During the pulse, compared to the no mesh case, a larger number of lower energy ions are measured. Simulation results show that this is caused by the potential in the mesh region which affects the trajectories of ions from the sheaths above the mesh top and corners and results in more ions being measured with trajectories less than ninety degrees to the RFEA front surface.

Thesis (M.S.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

[pt] A ANEEL efetua o cálculo do custo médio ponderado de capital do setor brasileiro de distribuição de energia elétrica (WACC Regulatório) e o insere nas tarifas, a partir de dados da economia norte-americana por entender que os dados da economia brasileira não apresentam séries consistentes. Com relação ao cálculo do custo do capital próprio, a ANEEL o define utilizando o modelo CAPM. Uma vez que os resultados obtidos a partir de dados da economia norte-americana, para refletirem a realidade brasileira, carecem de ajustes posteriores, além da limitação do uso do CAPM que apenas correlaciona o desempenho do setor com o mercado; a proposta apresentada neste trabalho é de calcular o custo médio ponderado de capital do setor através de dados da economia brasileira, e no caso do custo do capital próprio utilizar o modelo APT para sua estimação, correlacionando o desempenho do setor com as variáveis macroeconômicas que mais o impactam. Os resultados indicam que já é possível trabalhar com dados da economia brasileira e que o custo médio ponderado de capital estimado para o setor em estudo, feito pela ANEEL pode estar subestimado, uma vez que, por partir de dados da economia norte-americana pode acabar por não captar plenamente alguns riscos que o modelo APT capta partindo de dados da economia brasileira. / [en] ANEEL calculates the weighted average cost of capital of the Brazilian electric energy distribution sector (Regulatory WACC) based on American economic data, as it understands that the data from the Brazilian economy does not present consistent series. In the case of the cost of equity, ANEEL uses the CAPM model and inserts the results into the tariffs. Due to the fact that, the results obtained from the American economy in order to reflect the Brazilian reality need further adjustments, aside from the limitation of CAPM which correlates the performance of the sector exclusively with the market; we calculate the average cost of capital of the sector with Brazilian economic data. In the case of the cost of equity, we use the APT model to correlate the performance of the sector with the macroeconomics variables that have greatest impacts. The results indicate that it’s already possible to work with Brazilian economic data and that the average cost of capital of the sector as calculated by ANEEL might be underestimated, due to the use of American economic data that may not completely capture some risks that the APT model with Brazilian data captures.

Made available in DSpace on 2014-06-11T19:22:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-12-14Bitstream added on 2014-06-13T20:09:47Z : No. of bitstreams: 1 marinho_gsp_me_ilha.pdf: 1619719 bytes, checksum: 5c730f6b0eeb54a1540528e6af35faaa (MD5) / No mundo de hoje, conforme aumenta o interesse sobre fontes renováveis de energia, muitas pesquisas envolvem a busca de uma configuração eficiente para melhorar a distribuição desta energia e locá-las de uma maneira otimizada. A microrrede apresenta-se como uma alternativa para isto já que consiste em um sistema de energia de pequeno porte contendo vários consumidores e unidades geradoras distribuídas, possivelmente utilizando-se de diferentes fontes de energia, podendo ser considerada como um sistema independente operado através da interligação com o sistema principal de energia e que pode ser desconectada deste sistema sem maiores impactos, de acordo com a situação. Diante desta descrição as indústrias sucroalcooleiras também podem ser inseridas como um exemplo típico de microrrede permitindo assim uma diferente visão sobre como estas indústrias são afetadas pelo sistema principal de energia, mas, principalmente, como elas o afeta. Neste trabalho será visto alguns conceitos pertencentes à microrrede e alguns estudos que estão sendo realizados nesta área apresentando ferramentas que poderão comprovar que a indústria sucroalcooleira pode ser definida como uma microrrede / Nowadays, with the interest increasing about sources that use renewable energy, many researches involve the search for an efficient configuration to improve the distribution of this energy and locate them with an optimized way. The microgrid is small power system that consists of several consumer’s loads and small size distributed generation resources, possibly using different energy sources, and can be considered an independent system operated by interconnecting to the power distribution system and could be disconnected from this system without major impacts according to situation. In view of this description, the sugar-ethanol industries can also be inserted as a typical example of microgrid allowing a different view of how these industries are affected by the main system power, but especially how they affects it. In this study will be seen some concepts belonging to microgrid and some studies that are being done in this area, presenting tools that can demonstrate that the sugar-ethanol industry can be defined as a microgrid

Orientador: Dionizio Paschoareli Junior / Banca: Mariângela de Carvalho Bovolato / Banca: Félix Abrão Neto / Resumo: No mundo de hoje, conforme aumenta o interesse sobre fontes renováveis de energia, muitas pesquisas envolvem a busca de uma configuração eficiente para melhorar a distribuição desta energia e locá-las de uma maneira otimizada. A microrrede apresenta-se como uma alternativa para isto já que consiste em um sistema de energia de pequeno porte contendo vários consumidores e unidades geradoras distribuídas, possivelmente utilizando-se de diferentes fontes de energia, podendo ser considerada como um sistema independente operado através da interligação com o sistema principal de energia e que pode ser desconectada deste sistema sem maiores impactos, de acordo com a situação. Diante desta descrição as indústrias sucroalcooleiras também podem ser inseridas como um exemplo típico de microrrede permitindo assim uma diferente visão sobre como estas indústrias são afetadas pelo sistema principal de energia, mas, principalmente, como elas o afeta. Neste trabalho será visto alguns conceitos pertencentes à microrrede e alguns estudos que estão sendo realizados nesta área apresentando ferramentas que poderão comprovar que a indústria sucroalcooleira pode ser definida como uma microrrede / Abstract: Nowadays, with the interest increasing about sources that use renewable energy, many researches involve the search for an efficient configuration to improve the distribution of this energy and locate them with an optimized way. The microgrid is small power system that consists of several consumer's loads and small size distributed generation resources, possibly using different energy sources, and can be considered an independent system operated by interconnecting to the power distribution system and could be disconnected from this system without major impacts according to situation. In view of this description, the sugar-ethanol industries can also be inserted as a typical example of microgrid allowing a different view of how these industries are affected by the main system power, but especially how they affects it. In this study will be seen some concepts belonging to microgrid and some studies that are being done in this area, presenting tools that can demonstrate that the sugar-ethanol industry can be defined as a microgrid / Mestre

Orientadores: João Carlos Camargo, Ennio Peres da Silva / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências / Made available in DSpace on 2018-08-16T18:59:48Z (GMT). No. of bitstreams: 1 Donadon_AntonioRoberto_M.pdf: 1117953 bytes, checksum: 01a83592806648f889aea2c35b02b7c6 (MD5) Previous issue date: 2010 / Resumo: O objetivo do trabalho foi propor uma minuta de norma de conexão de geradores ou pequenos sistemas de geração distribuída em baixa tensão (GDBT) com potência menor ou igual a 75 kW monofásico ou trifásico com conversão estática em paralelo com a rede de distribuição secundária da concessionária local. Para atingir esse objetivo realizou-se um levantamento do estado da arte em matéria de normas de conexão em países onde esse assunto já se encontra em situação mais avançada bem como da incipiente legislação brasileira sobre o assunto. Baseado nisso e nos os dados obtidos dos testes de operação das fontes estudadas no projeto de pesquisa Implantação de Geração Distribuída Junto à Rede de Distribuição relacionados aos aspectos de qualidade de energia e segurança chegou-se a um elenco de tópicos relevantes para a construção de uma norma. O trabalho concluiu também que fontes de GDBT que possuam conversores estáticos que atendam aos requisitos de segurança e qualidade de energia da norma internacional IEEE 1547 poderiam ser conectadas à rede de distribuição da concessionária / Abstract: The objective was to propose a draft standard for connecting small single-phase or three phase generators with rated power lower than or equal to 75 kW with static converter in parallel with low voltage utility grid (GDBT). To reach this goal it was carried out a survey of the state of the art in connection standards in countries where this matter is already more advanced state as well as the incipient Brazilian legislation on this matter. Based on this survey and the data obtained from operation tests of power sources studied in the R&D project Implementation of Distributed Generation in the Utility Grid related to safety and power quality was possible to obtain a range of relevant topics to build a connection standard. The study also concluded that GDBT power sources equipped with static converters that meet the international standard IEEE 1547 safety and power quality requirements could be connected to the utility grid / Mestrado / Engenharia Mecanica / Mestre em Planejamento de Sistemas Energéticos

The performance of photovoltaic (PV) modules in terms of their ability to convert incident photon to electrical energy (efficiency) depends mostly on the spectral distribution of incident radiation from the sun. The incident spectrum finally perceived by the module depends strongly on the composition of the medium in which it has traveled. The composition of the earth’s atmosphere, which includes, amongst others, water vapour, gases such as carbon dioxide and oxygen, absorbs or scatters some of the sunlight. The incident solar spectrum is also modified by the diffuse aspect of radiation from the sky which strongly depends on aerosol concentration, cloudiness and local reflection of the earth’s surface. Although it is well known that the changes in outdoor spectrum affect device performance, little work has been conducted to support this theory. This is probably due to lack of spectral data or in certain instances where data is available, little knowledge of interpreting that data. The outdoor spectral data that one obtains in the field does not come clearly for just simple interpretation. Different analytical interpretation procedures have been proposed, all trying to explain and quantify the spectral influence on PV devices. In this study an assessment methodology for evaluating the effects of outdoor spectra on device performance parameters during the course of the day, seasons and or cloudy cover has been developed. The methodology consists of developing a device dependant concept, Weighted Useful Fraction (WUF) using the outdoor measured spectral data. For measuring PV module’s performance parameters, a current-voltage (I-V) tester was developed in order to monitor the performance of six different module technologies. The Gaussian distribution was used to interpret the data. For hot-spot analysis, different techniques were used, which include Infrared thermographic technique for identifying the hot-spots in the solar cells, SEM and EDX techniques. The AES technique was also used in order to identify other elements at hot-spots sites that could not be detected by the EDX technique. iii Results obtained indicate that multicrystalline modules performance is affected by the changes in the outdoor spectrum during summer or winter seasons. The modules prefer a spectrum characterized by WUF = 0.809 during summer season. This spectrum corresponds to AM 2.19 which is different from AM 1.5 used for device ratings. In winter, the mc-Si module’s WUF (0.7125) peaks at 13h00 at a value corresponding to AM 1.83. Although these devices have a wider wavelength range, they respond differently in real outdoor environment. Results for mono – Si module showed that the device performs best at WUF = 0.6457 which corresponds to AM 1.83 during summer season, while it operates optimally under a winter spectrum indicated by WUF of 0.5691 (AM2.58). The seasonal changes resulted in the shift in WUF during day time corresponding to the “preferred” spectrum. This shift indicates that these devices should be rated using AM values that correspond to the WUF values under which the device operates optimally. For poly-Si, it was also observed the WUF values are lower than the other two crystalline-Si counterparts. The pc-Si was observed to prefer a lower AM value indicated by WUF = 0.5813 during winter season while for summer it prefers a spectrum characterized by WUF = 0.5541 at AM 3.36. The performance of the single junction a-Si module degraded by 67 percent after an initial outdoor exposure of 16 kWh/m² while the HIT module did not exhibit the initial degradation regardless of their similarities in material composition. It was established that the WUF before degradation peaks at 15h00 at a value of 0.7130 corresponding to AM 4.50 while the WUF after degradation “prefers” the spectrum (WUF = 0.6578) experienced at 15h30 corresponding to AM value of 5.57. Comparing the before and after degradation scenarios of a-Si:H, it was observed that the device spends less time under the red spectrum which implies that the device “prefers” a full spectrum to operate optimally. The degradation of a-Si:H device revealed that the device spectral response was also shifted by a 7.7 percent after degradation. A higher percentage difference (61.8 percent) for spectral range for the HIT module is observed, but with no effects on device parameters. Seasonal changes (summer/winter) resulted in the outdoor spectrum of CuInSe2 to vary by WUF = 1.5 percent, which resulted in the decrease in Isc. This was ascertained by iv analyzing the percentage change in WUF and evaluating the corresponding change in Isc. The analysis showed that there was a large percentage difference of the module’s Isc as the outdoor spectrum changed during the course of the day. This confirmed that the 17 percent decrease in Isc was due to a WUF of 1.5 percent. In mc-Si solar cells used in this study, it was found that elemental composition across the entire solar cell was not homogenously distributed resulting in high concentration of transition metals which were detected at hot spot areas. The presence of transition metals causes hot-spot formation in crystalline solar cells. Although several transition elements exist at hot-spot regions, the presence of oxygen, carbon, iron and platinum was detected in high concentrations. From this study, it is highly recommended that transition elements and oxygen must be minimized so as to increase the life expectancy of these devices and improve overall systems reliability

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 74-76. / by Stephen W. Lang. / Ph.D.

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