Orientador: Ernesto Ruppert Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-15T03:55:20Z (GMT). No. of bitstreams: 1 PeqquenaSuni_JuanCarlos_M.pdf: 1533933 bytes, checksum: dbd348c759114d83f69069e35635591c (MD5) Previous issue date: 2009 / Resumo: Os parâmetros do modelo matemático dinâmico dos geradores síncronos como a resistência elétrica dos enrolamentos de estator por fase, a resistência elétrica do enrolamento de campo, as resistências elétricas dos enrolamentos amortecedores de eixo direto e de eixo em quadratura, as reatâncias de dispersão dos enrolamentos de estator por fase, do enrolamento de campo e dos enrolamentos amortecedores, bem como as reatâncias de magnetização de eixo direto e de eixo em quadratura do gerador são possíveis de serem determinadas, com razoável aproximação, através de ensaios específicos como o ensaio para determinação da reatância de Potier, o ensaio de curto-circuito trifásico brusco e os ensaios de rejeição de carga. Neste trabalho discute-se o problema da determinação de parâmetros do gerador síncrono auxiliado pela realização de simulações dinâmicas usando o software Matlab/Simulink e a sua biblioteca SimPowerSystems para determinação de parâmetros de um gerador de pólos lisos e de um gerador de pólos salientes através de ensaios de medição da reatância síncrona de eixo direto, ensaio de Potier, ensaio de curto-circuito brusco e ensaio de rejeição de carga. Diversos resultados e conclusões são apresentados usando os parâmetros padronizados mostrados explicitamente por Krause em seu importante livro publicado em 1986. Trata-se de um trabalho que tem finalidades didática e tecnológica de discutir essa questão / Abstract: The synchronous generator dynamic mathematical model parameters like the per phase stator winding electrical resistance, the field winding resistance, the direct and quadrature damping winding resistances, the field winding leakage reactance, the per phase stator winding leakage reactance, the damping winding leakage reactances, and direct and quadrature magnetizing reactances are possible to be determined with some accuracy through specific tests like the Potier reactance determination, the sudden short-circuit test and the load rejection tests. This work is addressed to the problem of salient poles and cylincrical rotor synchronous generator parameters determination aided by the use of dynamic simulations implemented with the Matlab/Simulink package using its SimPowerSystems library. Some results and conclusions about the parameters determination are presented using the standardized and fundamental parameters as shown in the Krause book published in 1986. This paper has both didactic and technological subjects and it is addressed to discuss several aspects on the real parameters determination activities / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

Transitioning from an energy system based on fossil fuels to an energy system based on renewables is necessary to limit global warming and comes with both opportunities and challenges. National policies in Cuba look toward the domestic sugar industry for synergies in this transition, and bagasse is projected to play a key role in the future electricity system. Since bagasse only is available during the sugarcane harvesting season, it must be supplemented with other feedstock for power production year-round. Biomass can have important interactions with CLEWs and therefore a nexus approach is important to ensure policy coherence across sectors. This study investigates different pathways for the Cuban energy transition from a CLEWs perspective through a scenario analysis and uses OSeMOSYS as a tool. This study shows that national policies for increased food security, regrowth of the sugar industry, use of energy crops and increased electricity consumption to develop the country compete for land and water resources. While there are currently plenty of resources, compromises will be needed in the medium- to long-term in order to stay within natural boundaries. This is especially true for the water sector since precipitation is expected to decrease in the future due to climate change and since sea level rise will contaminate groundwater. Another effect of climate change is soil degradation which would decrease yields. Increased energy and water inputs to the agricultural sector is known to increase yields in developing countries such as Cuba, which is why an adaptation strategy to maintain yields could be to increase these inputs. However, this would further amplify the pressure on water resources. Exceeding the exploitable internal renewable freshwater resources would then require water inputs from desalination plants which is an energy intensive process, which - if powered by an electricity system with a high share of biopower - could create a vicious cycle. / Omställningen från ett fossilbaserat energisystem till ett förnybart system är nödvändigt för att begränsa den globala uppvärmningen och innebär både möjligheter och utmaningar. Nationella policys i Kuba ser till landets sockerindustri för synergier i denna omställning, och bagass väntas spela en nyckelroll i det framtida elsystemet. Eftersom bagass endast är tillgängligt under sockerrörens skördesäsong måste den kompletteras med andra bränslen för att el ska kunna produceras året om. Biomassa kan ha betydande påverkan på CLEWs varför det är viktigt med en nexusanalys för att säkerställa samstämmighet av policys för olika sektorer. Denna studie undersöker olika tillvägagångssätt för den kubanska energiomställningen ur ett CLEWs-perspektiv genom en scenarioanalys i vilken OSeMOSYS används som modelleringsverktyg. Denna studie fann att nationella policys för ökad trygghet av matförsörjning, återuppbyggnad av sockerindustrin och ökad elkonsumtion för att utveckla landet konkurrerar om land- och vattenresurser. Det finns för närvarande gott om resurser, men på medel och lång sikt kommer kompromisser behövas för att stanna inom naturens gränser. Detta gäller särskilt för vattensektorn eftersom nederbörd väntas minska i framtiden till följd av klimatförändringar och eftersom höjningar av havsvattennivån kommer kontaminera grundvatten. Ytterligare påverkan från klimatförändringarna är markförstöring vilket minskar skörden. Ökad energi- och vattenanvändning i jordbrukssektorn ger vanligtvis högre skörd i utvecklingsländer såsom Kuba, vilket innebär att en anpassningsstrategi för att behålla skördenivån skulle kunna vara att öka dessa. Detta kan dock ytterligare förstärka belastningen på vattenresurserna. Att överskrida de utnyttjbara förnybara färskvattenresurserna skulle kräva avsaltning av vatten vilket är en energikrävande process, vilket - om energiförsörjningen kommer från ett system med mycket biomassa - skulle kunna skapa en ond cirkel.

Thesis (MBA)--Stellenbosch University, 2011. / Gaia Power is a South African start-up in the renewable energy industry. Among other products, they developed a wave energy converter, which is a device used to extract energy from ocean waves. This research deals with the economic feasibility study of the wave energy converter. Wave energy is a young field of research, especially in the South African context. Therefore sources for multiple angles of the project had to be found, analysed and brought into the Gaia Power context. Understanding the cost drivers of a wave energy plant was the foundation of the research itself. The Gaia Power specific levelised cost of electricity generation was calculated based on actual supplier quotes, reference costs found in the literature as well as assumptions. Still, such a calculation is actually more an estimation due to a high uncertainty level in all cost components. Especially the construction cost as well as the discount rate used have therefore been tested for sensitivity. Gaia Power‟s target production cost was R0.54 kWh, which equalled the Eskom tariff at the time of this research. Taking into account a R0.10/kWh fee payable to Eskom, the target cost sank to R0.44, which is about 25 percent lower than the minimum value for electricity generation cost found in the literature. This target was therefore expected to be and proved to be difficult to reach. The calculated levelised electricity cost was R0.99/kWh, with a possible range of R0.54/kWh to R1.60/kWh observed in the sensitivity analysis. These results show that the Gaia Power wave energy converter in the given specifications was not economically feasible. It was therefore recommended to rethink the specifications in order to reduce construction cost, which proved to be the largest cost driver. Besides the quantitative findings, this research also has a strong qualitative side. During the whole research it became obvious that there was an overall high risk level in the project due to the lack of experience with wave energy in general and in South Africa specifically, as well as the high impact of weather on the construction. Those risks were identified, analysed and recommended mitigation actions were derived.

Thesis (MDF)--Stellenbosch University, 2012. / The provision of infrastructure in developing countries is traditionally a preserve of government discharged through state-owned monopolies. This arrangement enables the government to charge tariffs below cost recovery as a way of protecting consumers. Unfortunately, the state utilities are generally run inefficiently, relying on the public budget for both capital and operational expenditure. Private sector players have gradually started to engage in the provision of infrastructure in recent years. Working alone or in co-operation with government, these players have offered a viable alternative for securing financial resources by using well-structured project finance structures and expertise for efficient delivery of services, such as roads, water, electricity and hospitals. The private sector participation has resulted in fiscal relief as funding sources are broadened to include domestic and offshore capital markets. It has also been accompanied by necessary sector reforms, such as legislative amendments to protect private property, allowing private players to invest in the respective infrastructure domains. Consumers‟ perceptions have been mixed, largely due to resultant higher costs of services. In Tanzania, the Tanzania Electricity Supply Company (TANESCO), a vertically-integrated state monopoly, is responsible for generation, transmission, distribution and retailing of electricity. As sole provider, TANESCO has woefully failed to serve the estimated demand of about 1 200MW. Lack of adequate funding for new capital investment and maintenance of the existing network has seriously curtailed output to just over 500MW – less than half of installed capacity. This situation has been compounded by drought on the predominantly hydro-based generation. Transmission losses have also worsened electricity delivery. The result is that only 14 percent of the urban and about two percent of the rural population had electricity access as at 2010. Sector reforms introduced in the 1990s allowed independent power producers (IPPs) to set up fuel and gas-fired generation facilities and selling output to TANESCO under Power Purchase Agreements. Worsening electricity shortages have forced the Ministry of Energy and Minerals to engage more IPPs on an emergency basis at very exorbitant feed-in tariffs. Other smaller-scale private generators have also entered the deregulated generation sector using the regulatory framework set up by the Energy and Water Utilities Regulatory Authority (EWURA). Various generation technologies are used and off-grid installations have enabled potential consumers beyond the national grid to have access. This study presents perceptions on challenges faced by private sector investors and financiers in participating in electricity generation. The findings highlight the apparent lack of appetite by financiers to underwrite long-term infrastructure projects. Furthermore, the capital markets are not developed sufficiently to meet the capital needs of private investors who see opportunity in the largely unserved electricity market. The results of the study help to show that the challenges of providing sufficient and affordable electricity in Tanzania cannot be addressed within the context of current macro-environmental circumstances. Specific policy guidelines are required to enhance the level of development of the financial market, facilitate private sector access to the required debt capital, and improve the tariff structure to attract investments in the electricity generation segment.

Thesis (MBA)--Stellenbosch University, 2014. / Census 2011 put the rate of electrification in South Africa at 84 percent. Even though this is a positive outcome to the previously recorded 34 percent, it has served as a clear indication that the target for Universal Access to Electricity by 2014 as set by President Jacob Zuma is unlikely to be achieved. In June 2013, cabinet approved the implementation of the new household electrification strategy and in support of this decision the Department of Energy was tasked to develop a new electrification roadmap or implementation plan. The intention of this research study has been to contribute to the development of this strategic plan by analysing the status of electrification in KwaZulu-Natal, as extracted from the provincial Geographical Information System, in order to identify the optimal electrification roll out plan and to develop guiding principles for the electrification of the province. The research outcomes provide a view of the current state of electrification within the province, identify the major technical constraints which hinder the progress, and provide recommendations for implementation roll out for KwaZulu-Natal province. The finding of this research is that of the 497 799 thousand un-electrified houses, 169 506 HH are not electrifiable as there is not sufficient capacity on the existing networks to cater for these households. Of those, 132 007 households are dependent on the establishment and construction of new bulk infrastructure such as substations and lines, while 37 499 are dependent on the upgrade or refurbishment of the existing infrastructure. The research has identified and categorised the ‘critical’ bulk infrastructure that will benefit 5 000 households or more as well as the high impact infrastructure projects that cater for 3 000 households or more. The research has also identified municipalities that are above the average of 84 percent electrification and categorised these as quick win areas to help in the progression toward universal access. As the research has also identified the dark havens, named as such due to being less than 50 percent electrified and plagued by technical constraints which makes any electrification of these areas not possible in the next five to ten years. Recommendations for responding to all four categories of findings are put forward.

Thesis (MDF)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Coal export mines in the Mpumalanga Highveld region of South Africa generate growing volumes of discard coal estimated to be in excess of a billion tonnes. It presents a significant pollution hazard. Discard coal has a usable carbon content that can be used in the generation of power through the application of fluidized bed combustion technology. The objective of this study was to evaluate its potential as an economically viable fuel source for generation of electricity at the Witbank coalfields. This study was motivated by advances in fluidized combustion technology and significant changes in the South African electricity market in recent years. A holistic approach was adopted considering regulatory policy, market, technical, environmental and economic factors in the use of discard coal as an alternative fuel source. The policy and regulatory environment was assessed from the perspective of the private sector as project developer and the most likely source of funding, given government’s funding constraints. An evaluation of the future pricing structure of electricity, energy resource mix, demand growth, future development of the coal market, production of discard coal and the cost of coal was conducted. Levelised cost of electricity methodology was used to conduct the economic feasibility for comparison with the cost of Eskom’s pulverised coal technology for its new power stations. The study found that generating electricity from discard coal presents a significant commercial opportunity as its levelised cost of electricity was found to be lower than Eskom’s levelised cost of electricity for its new power stations. Plant sizes of 125 MW to 1 000 MW were considered. For plant capacities of about 500 MW and larger, the cost of electricity was found to be competitive with the current average electricity price taking into account the cost of transmission/distribution and interest charges. This is on condition that the electricity is sold to Eskom or wheeled through Eskom’s grid and sold to third parties. Otherwise, plant capacity will be limited to the maximum demand from large local users, which is expected to be considerably less than 500 MW. Currently there is no regulatory certainty on wheeling mechanisms and charges and it is an area where major policy development is required. The development of a project could be hampered by policy uncertainty and because of Eskom’s monopoly position as single buyer. The favourable results and findings of the economic evaluation conducted during this study warrant further detailed feasibility studies.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The design, development and evaluation of a novel wave energy converter (WEC) device, called the ShoreSWEC, in a South African port development is presented. Based on the device requirements, site selection criteria were specified and applied to identify a suitable deployment location. A wave modeling procedure was developed to determine the operational wave conditions and available wave power resource at the selected location. The site was found to have a low mean annual average resource of approximately 2.3 kilowatt per meter wave crest (kW/m) due to its relatively sheltered location. The wave model was further used to determine design storm conditions and a structural stability analysis of the device was conducted. Experimental tests were performed to evaluate the hydrodynamic conversion efficiency of a single chamber of the device at its most conservative orientation, under a variety of wave energy conditions. The effect of a floor incline and an additional chamber on the performance of the system was investigated. The incline improved efficiency for low wave heights, making it ideal for the low wave power resource conditions of the site, whilst the multi-chamber system experienced increased performance at high wave periods. A comparison between the ShoreSWEC and a conventional oscillating water column (OWC) WEC showed that the OWC extracted 72% more energy, highlighting the sensitivity of performance on device orientation. A three-dimensional (3D) numerical model of the experimental setup was developed. The numerical model provided comparable water surface elevations inside the flume and chamber, yet predicted significantly higher internal chamber pressures and overall efficiency. The electricity generation potential of a 10 chamber ShoreSWEC at the specified location, approximated from the experimental results and 11 years of hindcast wave data, was found to be 6 kW on average for a 15 kW capacity system. Results of this study highlighted the need for greater understanding of the hydrodynamic characteristics of a full length device. Experimental tests in a 3D wave basin on a scaled full length ShoreSWEC model are therefore recommended. Once conducted, South Africa will be one step closer to the deployment of the full scale SWEC device. / AFRIKAANSE OPSOMMING: Die ontwerp, ontwikkeling en evaluasie van ‘n unieke golfenergieomsetter (GEO), genaamd die ShoreSWEC, in ‘n Suid-Afrikaanse haweontwikkeling word aangebied. Terrein evaluasie kriteria, gebaseer op die omsettervereistes, is ontwikkel en toegepas om die mees belowende terrein te identifiseer. ‘n Golfmodeleringsprosedure is ontwikkel om die operasionele golfkondisies en beskikbare golfdrywinghulpbron te bepaal. Daar is gevind dat die terrein ‘n lae gemiddelde golfdrywing van bykans 2.3 kilowat per meter golfkruin het as gevolg van die beskutte ligging. Die golfmodel is verder gebruik om ontwerpstormkondisies te bepaal en ‘n stabiliteitsanalise was op die toestel struktuur uitgevoer. Eksperimentele toetse van verskeie golfenergie kondisies is gedoen om die hidrodinamiese omsettingseffektiwiteit van ‘n enkel kamer van die toestel te bepaal teen sy konserwatiefste orientasie. Die effek van ‘n vloerhelling en ‘n addisionele kamer op die uitsette van die sisteem is ondersoek. Die helling het effektiwiteit verbeter vir lae golfhoogtes wat dit ideaal maak vir die lae hulpbron by die terrein, terwyl die veelvoudige-kamer-sisteem beter gevaar het by hoë golfperiodes. ‘n Vergelyking tussen die ShoreSWEC en ‘n konvensionele ossilerende waterkolom (OWK) GEO het gewys dat die OWK 72% meer energie onttrek. Dit beklemtoon die sisteem se sensitiwiteit vir die inkomende golfrigting. ‘n Drie-dimensionele (3D) numeriese model van die eksperimentele opstelling is ontwikkel. Die numeriese model het aansienlik hoër drukke binne die kamer, en gevolglik algehele effektiwiteit, voorspel as die eksperimentele toetse. Die elektriese opwekkingskapasiteit van ‘n 10 kamer ShoreSWEC by die terrein, gebaseer op die eksperimentele resultate en 11 jaar se golfdata, is bereken as 6 kW gemiddeld vir ‘n 15 kW kapasiteit stelsel. Die bevindinge van hierdie studie het die behoefte aan ‘n beter begrip van die hidrodinamiese eienskappe van ‘n vollengte sisteem beklemtoon. Eksperimentele toetse in ‘n 3D golfbak op ‘n geskaleerde vollengte ShoreSWEC model word dus aanbeveel. Sodra dit voltooi is, sal Suid-Afrika een stap nader wees aan die ontplooiing van ‘n volskaalse SWEC toestel.

Abstract not available

Increasingly intensive efforts are being made to enhance energy systems via augmented introduction of renewable energy along with improved energy efficiency. Resource constraints and sustained high fossil fuel prices have created a new phenomenon in the world market. Enhanced energy security and renewable energy development are currently high on public agenda worldwide for achieving a high standard of welfare for future generations. Biomass and municipal solid waste (MSW) have widely been accepted as important locally-available renewable energy sources offering low carbon dioxide (CO2) emissions. Concerning solid waste management, it has become a critical issue in Southeast Asia since the most popular form for waste disposal still employs open dumping and landfilling. While the need for a complete sustainable energy solution is apparent, solid waste management is also an essential objective, so it makes sense to explore ways in which the two can be joined. Electricity production in combination with energy recovery from flue gases in thermal treatment plants is an integral part of MSW management for many industrialized nations. In Sweden, MSW is considered as an important fuel resource for partially meeting EU environmental targets within cogeneration. However it is normally difficult to justify traditional cogeneration in tropical locations since there is little need for the heat produced. Similarly, MSW-fired cogeneration usually operates with low capacity during non-heating season in Sweden. Therefore, it is very important to find new alternatives for energy applications from waste, such as the implementation of thermally driven cooling processes via absorption cooling in addition to electricity production. The work presented herein concentrates first on an investigation of electricity generation from MSW power plants and various energy applications from waste in tropical urban areas. The potential for various types of absorption chillers driven by MSW power plants for providing both electricity and cooling is of particular interest. Additionally a demonstration and analysis of decentralized thermally driven cooling in district heating network supplied by low temperature heat from a cogeneration of MSW have been conducted. This study aims at developing the best system configuration as well as finding improved system design and control for a combination of district heating and distributed thermally driven cooling. Results show that MSW incineration has the ability to lessen environmental impacts associated with waste disposal, and it can contribute positively towards expanding biomass-based energy production in Southeast Asia. For electricity production, the proposed hybrid dual-fuel (MSW/natural gas) cycles feature attractive electrical efficiency improvements, leading to greenhouse gas emissions reduction. Cogeneration coupled with thermally driven cooling is a solution that holds promise for uniting enhanced sustainability with economic advantages. The system offers great opportunity for primary energy saving, increasing electrical yield and can significantly reduce CO2 emissions per unit of cooling as compared to compression chiller. The demonstration and simulation have also revealed that there is a potential with some modifications and improvements to employ decentralized thermally driven cooling in district heating networks even in temperate regions like Sweden. Thus, expanding cogeneration towards trigeneration can augment the energy supply for summer months in Europe and for year-round cooling in tropical locations. / QC 20110408

Supercapacitors are important electrochemical energy storage devices for microelectronic and telecommunication systems, electric cars, and smart grids. However, the energy densities of existing supercapacitors are still inadequate for many applications. Vanadium oxides have been studied as viable supercapacitor alternatives, with varying results. Methods are often complicated or time-consuming, and electrode fabrication often includes carbon powder and binder. The objective of this work was to study the effect of processing conditions on specific capacitance of supercapacitors based on vanadium oxides coated on carbon fiber papers. This study was conducted to form easily-fabricated compounds of vanadium oxides which could offer promise as pseudocapacitor material, and to nucleate these compounds directly onto inexpensive carbon fiber without binder. The incipient wetness impregnation technique was used to fabricate the electrodes. Electrochemical performance of the resulting electrodes was tested in a Swagelok-type electrochemical two-electrode cell, and the electrodes were characterized by XRD and SEM. Interesting nanofeatures were formed and the vanadium oxides exhibited pseudocapacitance at a respectable level.