Abstract The main emphasis in modern RF power amplifier (PA) research is on improving linearity while at the same time maintaining reasonably good efficiency, for which purpose external linearization in the form of feedforward or predistortion is often used. Linearity and linearization can be considered from both a fundamental signal (amplitude and phase conversions, AM-AM & AM-PM) and an intermodulation distortion (IMD) regeneration point of view, and since a study of intermodulation gives more information on the behaviour of an amplifier, linearity is studied in this thesis by analysing the amplitude and phase of IM components under varying signal conditions, i.e. as functions of temperature, modulation bandwidth and amplitude. To study the behaviour of IM components analytically, a Volterra model including electro-thermal distortion mechanisms is developed and a simulation technique is introduced to determine how easily the amplifier can be linearized. An S-parameter characterization method for extracting the Volterra model and the simulation model is developed, and the amplitude and phase dependences of the IM components are shown by means of measurements performed by a novel technique developed here. The results show that the behaviour of IM components is more complicated than had commonly been expected. Three techniques are developed for eliminating the frequency dependence of IM components, impedance optimization, envelope filtering and envelope injection. In the envelope injection technique, a low frequency envelope signal is added to the input of the amplifier in order to improve both the bandwidth and amplitude range of the memoryless predistortion. The functionality of envelope injection is demonstrated by Volterra calculations, simulations and measurements, and the technique is applied to 1W, 1.8 GHz common-emitter BJT and common-source MESFET amplifiers. IM cancellation better than 20 dB is achieved over a wide range of bandwidths and amplitudes. It is concluded that an inherently linear amplifier is not necessarily easy to linearize any further using external techniques, but that the part of the distortion that varies with bandwidth and amplitude can be cancelled out using envelope injection and the remaining memoryless distortion by means of a simple polynomial RF predistorter. This results in good cancellation of distortion, and since both envelope injection and RF predistortion consume little power, both good efficiency and linearity can be achieved.

>Magister Scientiae - MSc / Fly ash is the major waste material produced by power plants in the combustion of coal to generate electricity. The main constituents of fly ash are Si, Al, Fe and Ca with smaller amount of S, Mn, Na, K, and traces of many other elements such as Co, Cd, As, Se, Zn, Mo, Pb, B, Cu and Ni. Fly ash is usually disposed either by dry or wet disposal methods. These disposal methods have raised major environmental concerns due to the potential leaching of chemical species from the ash heap by ingress of rainfall and brine used to transport the fly ash to the dam. This study focuses on the changes in chemical composition, morphology and mineral phases due to weathering, of coal fly ash co-disposed with brine over 20 years at Sasol Secunda ash dump in Mpumalanga Province, South Africa. The design and operation of the Secunda ash dump presupposes that the ash dump may act as a sink for the salts which originated from chemicals used for normal operation in the plants. The majority of these salts come from the brines generated during desalination and raw water regeneration. The aim of this study is to ascertain if the ash dump could serve as a sustainable salt sink.Samples were drawn along the depth of two drilled cores (S1 and S3) from the weathered Secunda ash dump and analysed in conjunction with the fresh (unweathered) Secunda fly ash taken from the fly ash hoppers for comparative analysis. Scanning electron microscopy (SEM), X-ray diffractive (XRD) and X-ray fluorescence (XRF) spectrometry were employed to obtain a detailed morphological, mineralogical and bulk chemical composition of all the samples. Pore water analysis was used to determine the pH, EC and moisture content of fly ash samples. A five step sequential chemical extraction procedure was used to establish the geochemical association of particular elements with various mineral phases. The total acid digestion test was also used to determine the total elemental compositions of the Secunda fly ash samples. The SEM results showed that the fly ashes consist of irregular and numerous spherically shaped particles. Changes (encrustations, etchings and corrosion) in the morphologies of the weathered ash particles were also observed. The XRD results revealed quartz, mullite, lime and calcite as the major mineral phases. Other minerals identified in very minor quantities in the drilled Secunda ash core that were dried prior to analysis were halite, kaolinite, nitratine, bassanite, microline. and hydrophitte. These phases may have formed during sample handling. XRF investigation revealed that the major oxides present in the dumped ash samples were SiO₂, A₂2O₃, CaO, Fe₂O₃, MgO, Na₂O, TiO₂ and the minor elements present were K₂O, P₂O₅, SO₃ and MnO. The sum of the mean values of the % composition of SiO₂, Al₂O₃, and Fe₂O₃ was 70.19 %, and 72.94 % for the two drilled ash core samples (S1 and S3) respectively, and 78.67 % for the fresh ash which shows the significant alteration of the Si, Al and Fe content in the ash matrix over time. The fly ash is classified as Class F using the ASTM C 618 standards. The loss on ignition (LOI) which is an indication of unburned carbon or organic content was 4.78 %, 13.45 % and 8.32 % for the fresh ash, drilled ash cores S1 and S3 respectively. The high LOI values for the drilled ash cores could indicate high hydrocarbon content in the ash dump because of co-disposal practises where hydrocarbon waste are included in the brine stream for disposal on the ash. While the ash samples from the surface appeared dry, moisture content (MC) analysis showed that there is considerable water entrained in the fly ash dump. The fresh ash MC was 1.8 % while core S1 ranged from 41.4 – 73.2 %; core S3 ranged from 21.7 – 76.4 %. The variations in the MC values can be attributed to uneven flow paths due to inconsistent placement conditions or variations in ambient weather conditions during placement. The fresh fly ash (n=3) had a pH of 12.38±0.15, EC value of 4.98±0.03 mS/cm and TDS value of 2.68±0.03 g/L, the pH of the drilled ash core S1 (n=35) was 10.04 ±0.50, the EC value was 1.08±0.14 mS/cm and the TDS value was 0.64 ±0.08 g/L. Core S3 (n=66) had pH of 11.04±0.09; EC was 0.99 ±0.03 and TDS was 0.57 ± 0.01. The changes in pH values can be attributed to the dissolution and flushing out from the dump basic alkaline oxides like CaO and MgO These variations in pH values shows that the fly ash is acidifying over time and metal mobility can be expected under these conditions. The large decrease of EC in the drilled ash cores S1 and S3 compared to the fresh ash indicated a major loss of ionic species over time in the ash dump. The sequential extraction scheme revealed that the elements Al, Si, Ca, Mg, Ba, Sr, Fe, Mn, Na, K, As, Pb, Cr, Mo, Cu, Ni and Zn are present in Secunda fresh and weathered fly ash and are partitioned between the water soluble, exchangeable, carbonate, iron and manganese, and residual fractions of the coal fly ash. It also showed that the trace elements As, Pb, Cr, Mo, Cu, Ni and Zn do not show permanent association with particular mineral phases as a continuous partitioning between different mineral phases was observed in the weathered drilled core. Generally, all the elements had the highest concentration in the residual fraction. But it was evident that the labile phase (water soluble, exchangeable and carbonate fractions) had fairly high concentrations of Si (± 6.5 %), Al (± 6.5 %), Ca (±10 %), Mg (± 5.5 %), Ba (± 7.5 %),Sr (± 7.5 %), Na (± 12 %) and K (± 12 %) for the Secunda drilled ash core (S1 and S3) and fresh fly ash samples. This indicates that these species can leach easily upon water ingress and could pose a danger to the environment. Na and K had the highest concentrations leached out in the labile phase in all the ash samples. The amount of Na leached out of the drilled Secunda ash core in the labile phase was 13.21 % of 18584.26 mg/kg in the five geochemical phases of core S1; and 9.59 % of 11600.17 mg/kg in the five geochemical phases of core S3 while the fresh Secunda fly ash leached out 11.28 % of 16306.30 mg/kg of Na in the five geochemical phases. This study provided significant insight into the pore water chemistry, morphology, mineralogy and chemical composition and the elemental distribution pattern of the major and trace elements in the Secunda fly ash and weathered drilled Secunda ashm core S1 and S3. Though results from XRF analysis and the sequential extraction scheme shows that Na, K, S, Ca and Mg were slightly captured from the co-disposed brine by the Secunda fly ash, these species were however released in the labile phase. Hence there was no significant retention of these species in the ash dump. The amount of these species retained in the weathered ash were (0.26 % and 0.55 %) for Na, (0.02 % and 0.34 %) for K, (0.08 % and 0.06 %) for S, (0.94 % and 0.01 %) for Ca and (0.37 % and 0.96 %) for Mg in drilled ash cores S1 and S3 respectively. This poor retention of Na K, S, Ca and Mg which are major components of Sasol Secunda brine in the drilled ash cores S1 and S3 clearly shows the unsustainability of the Secunda fly ash dump as a salt sink.

abstract: Climate change is affecting power generation globally. Increase in the ambient air temperature due to the emission of greenhouse gases, caused mainly by burning of fossil fuels, is the most prominent reason for this effect. This increase in the temperature along with the changing precipitation levels has led to the melting of the snow packs and increase in the evaporation levels, thus affecting hydropower. The hydropower in the United States might increase by 8%-60% due to Representative Concentration Pathway (RCP) 4.5 and RCP 8.5 scenarios respectively by 2050. Wind power generation is mainly affected by the change in the wind speed and solar power generation is mainly affected by the increase in the ambient air temperature, changes in precipitation and solar radiation. Solar power output reduces by approximately a total of 2.5 billion kilowatt- hour (kWh) by 2050 for an increase in ambient air temperature of 1 degree Celsius. Increase in the ambient air and water temperature mainly affect the thermal power generation. An increase in the temperature as per the RCP 4.5 and RCP 8.5 climate change scenarios could decrease the total thermal power generation in the United States by an average of 26 billion kWh and a possible income loss of around 1.5 billion dollars. This thesis discusses the various effects of climate change on each of these four power plant types. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2020

Ingenieros Ejecutores (IE) es una empresa que busca diversificar y hacer sostenible su cartera de negocios con la incursión y sostenibilidad en el sector construcción de Obras Civiles para obras energéticas. Para este importante objetivo es necesario que los contratos ya ganados apliquen las mejores y más modernas prácticas de la industria, que reducirán los riesgos sobre los compromisos asumidos ante su Cliente. En este contexto, en el presente proyecto de investigación, se desarrolla el Plan para la dirección del proyecto “Construcción de las Obras Civiles Central Térmica Recka II” aplicando las buenas prácticas de la Guía del PMBOK ® sexta edición, en Chiclayo para las fases de iniciación y planificación del proyecto. El Plan para la dirección del proyecto se ha desarrollado en base a los planes subsidiarios que son: Plan para la Gestión del Alcance, Plan para la Gestión del Cronograma, Plan para la Gestión del Costo, Plan para la Gestión de los Recursos, Plan para la Gestión de las Comunicaciones, Plan para la Gestión de los Riesgos, Plan para la Gestión de los Interesados, así como otras herramientas como EDT / WBS, Cronograma y Presupuesto como parte de la aplicación de los procesos y herramientas. La aplicación de estos planes se espera que brinde como consecuencia el éxito del presente proyecto, el cual permitirá a IE acercarse a sus objetivos, alcanzando los beneficios esperados para los interesados. / Ingenieros Ejecutores (IE) is a company that seeks to diversify and make its business portfolio sustainable with the incursion and sustainability in the Civil Works construction sector for energy works. For this important objective it is necessary that the contracts already won apply the best and most modern practices of the industry, which will reduce the risks on the commitments assumed before your Client. In this context, in the present research project, the Plan for the direction of the “Construction of Civil Works Thermal Power Plant Recka II” project is developed, applying the good practices of the Guide of the PMBOK ® sixth edition, on Chiclayo, for the phases of initiation and Project planning. The Project Management Plan has been developed based on the subsidiary plans that are: Integration Management Plan, Scope Management Plan, Schedule Management Plan, Cost Management Plan, Plan for Resource Management, Communications Management Plan, Risk Management Plan, Stakeholder Management Plan, as well as other tools such as EDT / WBS, Schedule and Budget as part of the process application and tools The implementation of these plans is expected to result in the success of this project, which will allow IE to approach its objectives, achieving the expected benefits for those interested. / Trabajo de investigación

In Mozambique, almost 80% of the population uses firewood for their energy needs,  however this use is not exclusive only to rural areas, observing the same in urban areas who not only use the wood and also charcoal stoves. Because of this situation, there is a huge devastation of the forest, which has caused the depletion of flora, thus missing native species without its due spare.  In Maputo, most households, the use of fire wood was replaced by charcoal because of high energetic intensity and also transportation and storing promptness. In 2011, three millions of sacs of charcoal have been in consumption, managing a market of $70 million in 2010 and 2012, the price rise a lot from 250 to 650 Meticais (200% more). In this context came the need, to evaluate the energy efficiency of charcoal stoves and their respective access by the population in Maputo in order to contribute to the reduction of excessive consumption of biomass. For it was made evaluation of energetic efficiency in ten stoves most used in the city of Maputo, We tested the quality of charcoal and found to demand access to its coal. The results showed that the charcoal tested is not the good quality because the values are outside the acceptable levels According to the literature. Energy efficiency evaluation noted that the most efficient stoves have been improved in spite of the water boiling test of the traditional stoves have been boil faster. There was also, that consumers prefer to buy products from day to day in establishments near to their residence and do not spend more money than 100.00 MTn (2 USD) every time moving to sales points. / I Mocambique använder nästan 80% av befolkningen ved för sina energibehov, men denna användning är inte exklusiv bara för landsbygdsområden, där man observerar samma i stadsområden som inte bara använder veden utan även koksugnar. På grund av den här situationen orsakas en enorm förödelse av skogen, vilket har orsakat utarmning av flora och inhemska arters fortplantning påverkas negativt. I de flesta hushåll i Maputo ersattes användningen av ved med träkol på grund av hög energiintensitet och snabbare transport och lagring. Under 2011 har tre miljoner säckar träkol konsumerats, vilket motsvarar en marknad på 70 miljoner dollar 2010 och 2012. Priset steg från 250 till 650 Meticais (mer än 200%) under denna period. I det här sammanhanget uppstod behovet att utvärdera energieffektiviteten hos ugnar för träkol och tillgången av sådana ugnar i Maputo för att bidra till minskningen av överdriven konsumtion av biomassa. För det gjordes utvärdering av energeffektiviteten i tio ugnar som mest används i staden Maputo. Kvaliteten på träkol testades och tillgången på träkol utvärderades. Resultaten visade att träkolet inte är av god kvalitet eftersom värdena ligger utanför acceptabla nivåer enligt litteraturen. Energieffektivitetsutvärderingen noterade att de mest effektiva ugnarna har förbättrats. Testen av de traditionella ugnarna visade att kokningstiden för vatten har kortats ner. Det visade sig också att konsumenter föredrar att köpa produkter från dag till dag i företag nära deras hemvist, och de spenderar inte mer än 100,00 MTn (2 USD) varje gång de flyttar till försäljningsställen.

Usinas Termelétricas (UTEs), compostas por ciclo simples a vapor e ciclo combinado, são instalações industriais que consomem elevadas quantidades de água, sobretudo por conta de suas operações de resfriamento e de geração de vapor. Paralelamente, tem-se observado a redução de oferta deste recurso em muitas regiões onde se encontram instaladas unidades termelétricas, fato que suscita a preocupação, o debate e a pesquisa acerca do desenvolvimento de tecnologias e estratégias direcionadas à mitigação do consumo e reaproveitamento de água em UTEs. Em contrapartida, do mesmo modo que UTEs são intensivas no consumo de água, esta é também produzida na forma de vapor em escalas significativas como resultado do processo de combustão. Contudo, a parcela de água produzida é lançada para a atmosfera juntamente com os demais gases produzidos (CO2, N2, O2, SO2). Frente a esse contexto, este trabalho se divide em duas etapas distintas. A primeira voltada à estimativa da quantidade de água e demais componentes presentes nos gases de combustão de trinta e seis UTEs brasileiras, dentre as quais vinte e duas são movidas a gás natural (ciclos simples e combinados) e quatorze a carvão mineral (ciclos simples). Tais estimativas levam em conta as condições ambientais do local de operação, a eficiência típica do ciclo e a composição do combustível empregado. A segunda etapa trata da modelagem e da simulação, sob diferentes condições operacionais (pressão, temperatura de resfriamento e porcentagem de vapor de água nos gases), de um condensador duplo tubo vertical operando sob regime de convecção natural no lado do resfriamento, a partir do qual se estuda o processo de condensação do vapor de água na presença dos demais gases produzidos, estes conhecidos como gases não condensáveis (GNC). Tais simulações tem o propósito de avaliar as taxas de recuperação de água capazes de serem obtidas por meio do condensador/processo idealizado. / Single and combined steam cycle thermoelectric plants are power plants that consume high amounts of water, mainly from the cooling and steam generation operations. At the same time, there have been a reduction in the supply of this resource in many regions where thermoelectric units are installed. This fact increases the concern, discussion, and research on the development of technologies and new strategies directed to the mitigation of the consumption and reutilization of water. On the other hand, likewise UTEs are intensive in water consumption, they also produce it at significant amounts of steam from the combustion process, and that amount of water produced is released to the atmosphere together with gases produced (CO2, N2, O2, SO2). In this sense, this work is divided into two distinct parts. The first one is aimed at estimating the amount of water and other components present in the flue gases of thirty Brazilian thermal power plants, of which twenty-two are powered by natural gas (single and combined cycles) and eight moved by coal (single cycles). Such estimates consider environmental conditions of the operation site, typical cycle efficiency, and fuel composition employed. The second part deals with a numerical modeling and simulation, at different operating conditions (pressure, cooling temperature, and water vapor content in the gases), of a double vertical tube condenser operating by natural convection on the cooling side, from which the condensation process of the water vapor is studied in the presence of the other gases produced (known as non-condensable gases, NCG). These simulations have the fundamental purpose of evaluating the rates of condensate that can be recovered by means of the condenser/idealized process.

Os procedimentos de licenciamento ambiental (LA) têm sido criticados pelos agentes econômicos, notadamente por aqueles ligados ao setor energético, por entenderem que a agilidade na análise dos processos de viabilidade ambiental de empreendimentos encontra-se aquém ao esperado. Com o objetivo de analisar a interferência de alguns fatores ligados aos procedimentos de LA sobre o tempo total de tramitação dos processos, foi realizada revisão documental de processos que tramitaram no estado de São Paulo, entre 1998 e 2007, para a instalação de usinas termelétricas a gás natural, com potência superior a 10 MW, e que obtiveram a licença ambiental prévia (LP). Foram obtidos dados quantitativos e informações qualitativas que permitiram verificar que os fatores número de solicitações de informações complementares feitas pelos órgãos ambientais ao empreendedor, número de impactos ambientais identificados no estudo de impacto ambiental (EIA) e número de condicionantes constantes na LP expedida não apresentam uma relação com o tempo de tramitação dos processos. Outros fatores como deficiências no estudo ambiental e a inadequação do local proposto à instalação dos empreendimentos, dadas as restrições ambientais, aparentemente apresentam maior interferência sobre os tempos de tramitação. Diante disto, destaca-se a necessidade de, previamente ao licenciamento, serem elaborados estudos específicos voltados à apresentação de alternativas locacionais que considerem critérios ambientais e critérios econômicos com o mesmo nível de importância para a tomada de decisão. Tais estudos, servindo como base de referência para a escolha da melhor localização para instalação de empreendimentos, tendem a reduzir o tempo total de tramitação dos processos de licenciamento. / The procedures for environmental licensing (LA) have been criticized by economic agents, especially by those connected to the energy sector, because they believe that agility on analysis of the processes of enterprises environmental viability is less than what was expected. In order to analyze the interference of some factors related to LA proceedings on proceeding period, the processes documentary review was held and transited in São Paulo State between 1998 and 2007 for the installation of natural gas thermal power plants with emitted preliminary environmental permit (LP) and output exceeding 10 MW. Quantitative data and qualitative information were obtained which allowed the confirmation that the factors number of requests for additional information made by environmental agencies to the enterprise, number of environmental impacts identified in the environmental impact statement (EIA) and number of constraints in the LP emitted have no relation to the proceeding period. Other factors such as shortcomings in the environmental study and inadequate the proposed site for the installation of enterprises, given the environmental restrictions, apparently show greater interference on the proceeding period. So, there is a necessity, prior to licensing, of being drawn up specific studies focused on the presentation of located alternatives to consider environmental and economic issues with the same level of importance for the decision. Such studies, serving as point of reference for choosing the best location for setting up of enterprises tend to reduce the proceeding period of the licensing processes.

O planejamento da operação energética em sistemas hidrotérmicos de potência com um único reservatório tem como objetivo determinar a participação de usinas hidrelétricas e térmicas de forma a garantir o suprimento de energia demandada ao menor custo operacional possível, dentro de restrições físicas e técnicas do modelo. Alguns fatores tornam a solução deste problema bastante complexa destacando a não linearidade e a não separabilidade temporal aditiva. O objetivo deste trabalho é apresentar uma nova abordagem com tratamento agregado das afluências, descrevendo uma nova caracterização das distribuições de probabilidades e um novo modelo para a programação dinâmica estocástica markoviana. Nesse novo modelo da programação dinâmica estocástica markoviana, agregações plurimensais de vazões são utilizadas como entrada em um modelo de programação dinâmica estocástica markoviana modificado para discretizações temporais plurimensais. A nova abordagem proposta foi simulada em diferentes usinas hidrelétricas brasileiras localizadas em diferentes regiões geográficas e sob diferentes regimes hidrológicos. Os resultados das simulações feitas com a utilização deste novo modelo são apresentados e comparados ao modelo de programação dinâmica estocástica markoviana mensal, atualmente utilizado no setor elétrico brasileiro, com economia de custos relativas superiores a 10% em alguns casos. / The energetic operation planning on hydrothermal power systems with a single reservoir aims to determine the participation of hydroelectric power plants and thermal power plants to guaranty supply of energy demanded with the smallest possible cost, under physical and technical model boundaries. Some points became the solution of this problem complex, highlighting the non linearity and the additive non time separability. The objective of this paper is show the new approach with aggregated inflows, describing a new probability distributions featuring and a new model for the markovian stochastic dynamic programming. On this new model of markovian stochastic dynamic programming, multi monthly inflow aggregations are used as input in a model of markovian stochastic dynamic programming modified for multi months discretizations. The new approach proposed was simulated on differents Brazilian hydroelectric power plants located on different regions and under different hydrologic regime. The results of simulations using this new model are presented and compared to the model of monthly markovian dynamic programming, nowadays used on the Brazilian electrical sector, with relatives economic savings up to 10% in some cases.

O planejamento da operação energética em sistemas hidrotérmicos de potência com um único reservatório tem como objetivo determinar a participação de usinas hidrelétricas e térmicas de forma a garantir o suprimento de energia demandada ao menor custo operacional possível, dentro de restrições físicas e técnicas do modelo. Alguns fatores tornam a solução deste problema bastante complexa destacando a não linearidade e a não separabilidade temporal aditiva. O objetivo deste trabalho é apresentar uma nova abordagem com tratamento agregado das afluências, descrevendo uma nova caracterização das distribuições de probabilidades e um novo modelo para a programação dinâmica estocástica markoviana. Nesse novo modelo da programação dinâmica estocástica markoviana, agregações plurimensais de vazões são utilizadas como entrada em um modelo de programação dinâmica estocástica markoviana modificado para discretizações temporais plurimensais. A nova abordagem proposta foi simulada em diferentes usinas hidrelétricas brasileiras localizadas em diferentes regiões geográficas e sob diferentes regimes hidrológicos. Os resultados das simulações feitas com a utilização deste novo modelo são apresentados e comparados ao modelo de programação dinâmica estocástica markoviana mensal, atualmente utilizado no setor elétrico brasileiro, com economia de custos relativas superiores a 10% em alguns casos. / The energetic operation planning on hydrothermal power systems with a single reservoir aims to determine the participation of hydroelectric power plants and thermal power plants to guaranty supply of energy demanded with the smallest possible cost, under physical and technical model boundaries. Some points became the solution of this problem complex, highlighting the non linearity and the additive non time separability. The objective of this paper is show the new approach with aggregated inflows, describing a new probability distributions featuring and a new model for the markovian stochastic dynamic programming. On this new model of markovian stochastic dynamic programming, multi monthly inflow aggregations are used as input in a model of markovian stochastic dynamic programming modified for multi months discretizations. The new approach proposed was simulated on differents Brazilian hydroelectric power plants located on different regions and under different hydrologic regime. The results of simulations using this new model are presented and compared to the model of monthly markovian dynamic programming, nowadays used on the Brazilian electrical sector, with relatives economic savings up to 10% in some cases.

Made available in DSpace on 2014-10-09T12:41:24Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:39Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP