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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Produktion av el och värme med stirlingmotorer från deponigas : På Blåbergets avfallsanläggning

Salomonsson, Gustav January 2022 (has links)
Sundsvall Energi har ansvaret för den gamla deponin på Blåbergets avfallsanläggning strax västerut från Sundsvall. Mellan slutet av 1960-talet fram till och med 2008 har ca 2 miljoner ton avfall deponerats. Från denna deponi har det under en längre tid producerats stora mängder deponigas. Deponigasen har tidigare använts i en hetvattenpanna vid Nacksta och tillfört värme till fjärrvärmesystemet. På grund av ineffektiv drift och minskande metaninnehåll i deponigasen stoppades transporten av deponigas till Nacksta 2013. Därefter har deponigasen enbart använts för fackling vilket innebär att deponigasen förbränns i en gasfackla. Enligt bestämmelser måste deponigas behandlas och användas för exempelvis energiutvinning eftersom innehållet i deponigasen har en kraftig växthuseffekt då gasen består av ca 40–60 % metan och 30–50 % koldioxid. Metan har en 28 gånger högre potential för global uppvärmning jämfört med koldioxid över en 100-årsperiod. I detta examensarbete har syftet varit att undersöka vilka möjligheter som finns för att ta vara på deponigasens energiinnehåll och därmed föreslå ett tekniskt alternativ gentemot enbart fackling av deponigasen. Dessutom har arbetet som syfte att beskriva den miljömässiga- och ekonomiska nyttan. Arbetet har utförts genom att energiinnehållet har tagits fram genom formler och antaganden samt att värmebehovet och uppskattningen av investeringskostnaden tagits fram. Nuvärdesmetoden och PayOffmetoden använts i samband ekonomiberäkningen i arbetet. Värmebehovet på anläggningen fick styra över hur mycket effekt som värmekällan bör ha för att klara högsta årsbehovet. Examensarbetet resulterade i att det mest lämpliga teknikalternativet, nämligen Stirlingmotorn, användes i detta arbete. På grund av ogynnsamma förutsättningar för att täcka värmebehovet på anläggningen har antagandet gjorts att den producerade värmen i stället gör miljönytta genom att tillföra värme till en av lakvattendammarna. Den producerade elen beräknades ha en täckningsgrad på ca 19 % av totala energiförbrukningen på anläggningen. Lönsamhetskalkylerna visar att lönsamheten för en eventuell investering blir ogynnsam vid låga elpriser samt vid låga metanhalter. Dock blir lönsamheten lämpligare vid höga elpriser och lägre investeringskostnader. Dessutom kunde det konstateras att lönsamheten blir betydligt gynnsammare om värmeproduktionen skulle ha nyttiggjorts samtidigt som elproduktionen. / Sundsvall Energi is responsible for taking care of the old landfill at  Blåberget waste facility west of Sundsvall. Between the end of the 1960s to year 2008, about 2 million tons of waste were deposit at the landfill. Large amounts of landfill gas have been produced at this landfill over the years. The landfill gas has previously been burned in a boiler at Nacksta and therefore added some heat to the district heating system. Due to inefficiency and declining methane content in the landfill gas, the distribution of landfill gas to Nacksta ended in 2013. Since then, the landfill gas has only been torched at the landfill site. Since the landfill gas has a strong greenhouse effect and due to regulations, the landfill gas must be treated and used for, as an example, energy utilization. Methane has a 28 times higher contribution risk to global warming compared to carbon dioxide over a 100-year period. In this project, the purpose has been to investigate what opportunities there are to utilize the energy content in the landfill gas and by that suggest an alternative instead of just torching the landfill gas. Additionally, the further purpose with the project is to describe the  environmental and economic benefits of the solution. The work has been done by determine the energy content by using formulas and assumptions. In addition, the heat demand for the landfill site as well as the estimation of investment cost was determined. The NPV and the Pay-Off was used in the economic calculations. The heat demand of the landfill site was the deciding factor of how much power the technical alternative should have to meet the highest annual heat demand. The project resulted in the fact that the most suitable technical alternative, namely the Stirling engine, became the technical choice in this work. Due to unfavorable conditions for the heat production from the Stirling engines at the plant, the assumption was made that the produced heat instead got  to supply heat to one of the leachate ponds. The electricity produced was calculated to meet around 19% of the total energy consumption at the landfill site. The economical estimates showed that the profitability of an eventual investment becomes unfavorable at low electricity prices and at low methane contents. However, the investment becomes far more profitable at high electricity prices and at lower investment costs. In addition, the results showed that profitability would be far more favorable if the produced heat had been utilized for property heating simultaneously as the electricity got produced.
32

Hybridization with CSP in a Cuban sugar mill

Vesterberg, Iris, Westerlund, Sofia January 2018 (has links)
Kuba har i dagsläget ett högt beroende av importerad olja, för att tillgodose sin växande efterfrågan på elektricitet. Importen sker främst från Venezuela. Detta beroende gör Kuba känsligt för ändringar i oljepriser samt det politiska klimatet. Den nuvarande krisen i Venezuela har haft en betydande inverkan på Kubas elproduktion. Genom att utöka landets förnybara energikällor kan Kuba minska sitt beroende av andra länder och diversifiera sin energiförsörjning. Detta kommer även att leda till en positiv miljöpåverkan då landets CO 2-utsläpp minskar. Kubas geografiska läge har ideala förhållanden för förnyelsebar energigenerering, så som solkraft. Solkraft utvecklas konstant och innehåller en hög potential. Concentrating Solar Power (CSP) är en teknologi där speglar och/eller linser används för att koncentrera solljus till en liten yta som konverterar solljuset till värme. Denna värme kan sedan användas i termodynamiska cykler. Det finns två huvudsakliga problem med implementering av CSP på Kuba. För det första är CSP beroende av momentana väderförhållanden, vilket leder till en oregelbunden elproduktion. För det andra har CSP höga investeringskostnader. För att adressera dessa problem, är det möjligt att implementera CSP i ett redan existerande kraftverk med regelbunden energikälla, d.v.s. skapa ett hybridkraftverk. På så vis uppnås regelbunden elproduktion med signifikant lägre investeringskostnad. Ett sådant existerande kraftverk kan hittas hos många av Kubas sockerbruk. Den här studien undersöker möjligheten att implementera solkraft i sockerbruket Carlos Baliño, beläget i Villa Clara, Kuba. Fabriken är självförsörjande av elektricitet på årlig basis. De använder en Rankine-cykel för att generera el och processvärme som används i sockerframställningen. Bränslet som används är bagasse, en restprodukt efter att sockerjuicen pressats ut ur sockerrören. Fyra CSP-teknologier och tre implementeringslayouts undersöktes, vilket resulterade i att parabolic trough-teknologin och förvärmning av vatten ansågs vara de bästa alternativen för Kuba och Carlos Baliño. Vidare undersöktes två olika scenarier för CSP. Scenario 1 innefattar implementering av CSP i sockerbruket under rådande skick och Scenario 2 består av implementering av CSP efter en investering gjorts i en Condensing Extraction turbin (CEST). Resultatet visar att Carlos Baliño bör investera i CEST innan de implementerar CSP, det vill säga Scenario 2. Detta beror på att i scenario 1 är det inte möjligt att generera elektricitet utanför sockersäsongen, vilket leder till att en stor del av solpotentialen inte kan utnyttjas. Den maximala investeringskostnaden för scenario 1 är 3,7 MUSD, vilket inte är en realistisk kostnad. Den maximala investeringskostnaden för scenario 2 beror av tillgänglig bagasseimport och är 5,9 – 7,2 MUSD. Att investera i CSP rekommenderas ej om bagasseimporten är obegränsad. Givet att bagasseimporten är begränsad skulle CSP-implementeringen leda till en utökad elproduktion av 5,4 – 7,2 GWh/år, en årlig minskning av oljeanvändandet med 16 100 – 21 800 tunnor och minskade CO2-utsläpp med 12 00-16 00 ton årligen. Carlos Baliños ekonomiska resultat skulle öka med 0,5 MUSD/år och den kubanska statens med 0,7 – 0,9 MUSD/år. Framtida studier rekommenderas undersöka möjligheten till generering av el året runt vid Carlos Baliño utan en CEST, solkraftsefterfrågan på nationell nivå och potentiella utvecklingar av solkraft hos Carlos Baliño. / Cuba is currently highly dependent on imported oil, mainly from Venezuela, to meet their growing electricity demand. This dependence makes Cuba sensitive to changes in oil price as well as the political climate. The current crisis in Venezuela has a large impact on Cuba’s electricity generation. By expanding its renewable energy sources Cuba could decrease their dependence on other countries and diversify their energy supply. Moreover, it would have a positive climate impact by reducing the country’s CO2-emissions. Geographically, Cuba has ideal conditions for renewable energy utilization, such as solar power. Solar energy is constantly progressing and is considered a great source of energy. Concentrating Solar Power (CSP) is a technology which applies mirrors and/or lenses to concentrate the sunlight onto a small area which converts the sunlight into heat, possible to use in a thermodynamic cycle. There are mainly two problems with the implementation of CSP in Cuba. Firstly, CSP is a non-dispatchable power generating system since it is dependent on the instantaneous weather conditions. Secondly, it has high investment costs. One way of solving these problems is by implementation CSP in an already existing power plants with a dispatchable source of energy, making it a hybrid power plant. Accordingly, the hybrid power plant would be dispatchable and the investment costs would be significantly lower. Existing power plants can be found in Cuban sugar mills. This study investigates the possibility to implement solar power in the sugar mill Carlos Baliño, located in Villa Clara, Cuba. The factory is currently self-sufficient electricity wise on a yearly basis, using a co-generation Rankine cycle to generate electricity and process heat used in the sugar production. The fuel used is bagasse, a rest product obtained after the sugar juice has been pressed out of the sugar canes. Four CSP-technologies and three implementation layouts were examined, resulting in the parabolic trough-technology and feedwater heating being considered the optimal solution. Furthermore, two different scenarios for CSP was investigated; implementation of CSP in the mill at the current state (scenario 1) or after investing in a Condensing-Extraction Turbine (CEST) (scenario 2). The results show that Carlos Baliño should invest in a CEST before considering implementation of CSP. Off-season operation is not available for scenario 1, leading to a vast amount of solar potential being unexploited. The maximal investment allowed for scenario 1 is 3.7 MUSD, which is not a realistic number. The maximal investment allowed for in scenario 2 is 5.9 – 7.2 MUSD, depending on bagasse import availability. If bagasse import is unlimited, it is not recommended to invest in solar power. Implementation of CSP in scenario 2 regarding bagasse import limits would yearly lead to an additional electricity generation at Carlos Baliño of 5.4 – 7.3 GWh, decrease the oil usage with 16,100 – 21,800 barrels and the CO2-emissons with 1,200 – 1,600 tonnes. Carlos Baliño’s annual yield would increase with 0.5 – 0.6 MUSD/year and the Cuban states annual yield would increase with 0.7 – 0.9 MUSD/year. Future work is recommended to explore alternatives to all year-around electricity generation in Carlos Baliño without investing in a CEST, investigate solar power demand on a national level, and examine possible developments of the suggested solar field, for instance solar-only operation.
33

A model to evaluate CO2 emission reduction strategies in the US

Arar, Joseph I. 06 August 2007 (has links)
No description available.
34

Water scarcity and electricity generation in South Africa.

Wassung, Natalie 12 1900 (has links)
Thesis (MPhil (Public Management and Planning))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: South Africa has a mean annual precipitation far lower than the global average. This is a fundamental constraint to development, especially when the country has already run out of surplus water and dilution capacity. To add further pressure, southern Africa’s water resources are expected to decrease as a result of climate change. Despite the potential devastation, the country’s response to climate change has been limited. South Africa’s energy sector is dominated by coal power stations and is the country’s primary emitter of carbon dioxide. Given the significantly higher water usage of coal-fired power plants compared to that of most renewable energy power plants, the transition to a clean energy infrastructure might be more successfully motivated by water scarcity than by the promise of reduced carbon emissions. This article analyses more critically the impact of coal-fired electricity generation on South Africa’s water resources, by estimating a water-use figure that extends backwards from the power plant to include water used during extraction of the coal. This figure can then be compared to the water usage of alternative electricity generation options. It is then possible to estimate how much water could be saved by substituting these alternatives in place of additional coal-fired plants. / AFRIKAANSE OPSOMMING: Suid-Afrika se gemiddelde jaarlikse neerslag is baie laer as die wêreldwye gemiddelde. Dit plaas ’n wesenlike beperking op ontwikkeling, veral aangesien die land se surplus water- en verdunningskapasiteit reeds uitgeput is. Om die saak verder te vererger, word verwag dat Suidelike Afrika se waterbronne gaan kleiner word as gevolg van klimaatsverandering. Ten spyte van die potensiële ramp, was die land se reaksie op klimaatsverandering tot dusver baie beperk. Steenkoolkragstasies, wat Suid-Afrika se energiesektor oorheers, is die land se primêre bron van koolstofdioksieduitlating. Gegewe die beduidend hoër waterverbruik van steenkoolkragstasies teenoor dié van die meeste kragstasies wat met hernubare energie werk, kan die verandering na ’n skoonenergie-infrastruktuur meer suksesvol gemotiveer word deur waterskaarste as deur die belofte van verminderde koolstofuitlatings. Hierdie artikel analiseer die impak van steenkoolgedrewe elektrisiteitsopwekking op Suid-Afrika se waterbronne meer krities deur te beraam hoeveel water verbruik word van die kragstasie terug tot by die ontginning van die steenkool. Hierdie syfer kan dan vergelyk word met die waterverbruik van alternatiewe kragopwekkingsopsies. Dit is dan moontlik om te beraam hoeveel water gespaar kan word deur hierdie alternatiewe op te rig in plaas van bykomende steenkoolkragstasies.
35

[en] RISK ANALYSIS APPLIED TO SELECT PRIMARY ENERGY SOURCES FOR POWER GENERATION IN BRAZIL / [pt] COMPARAÇÃO DE FONTES PRIMÁRIAS PARA GERAÇÃO DE ENERGIA ELÉTRICA NO BRASIL BASEADA EM CONCEITO DE RISCO

JAIR ARONE MAUES 14 January 2009 (has links)
[pt] O trabalho compara sistemas de conversão de energia para geração de energia elétrica, com ênfase no caso brasileiro, levando-se em consideração todos os fatores relevantes envolvidos, em especial os riscos associados a cada um dos componentes do custo final da energia. Os modelos de custos usuais de engenharia tendem a favorecer a geração de energia tradicional em detrimento das renováveis alternativas, ao ignorar os riscos envolvidos, baseando-se apenas no menor preço do quilowatt-hora gerado. O modelo financeiro aplicado nesta comparação baseia-se na Teoria de Portfólios, desenvolvida por Harry Markowitz. Primeiramente são avaliados os resultados do binômio risco-retorno relacionados à matriz prevista pela EPE - Empresa de Pesquisa Energética no Plano Nacional de Energia - 2030, publicado em 2006. Posteriormente, as alternativas indicadas pelo modelo são comparadas. Os resultados mostraram que a matriz prevista pela EPE em 2030 não está otimizada do ponto de vista do binômio retorno-risco dos investimentos em geração elétrica. Os aumentos da participação das fontes renováveis não tradicionais à matriz, especificamente, resíduos das plantações de cana-de-açúcar e energia eólica, reduzem tanto o risco quanto o custo médio do quilowatt-hora gerado. Este resultado vale mesmo quando se variam os dados de entrada, notadamente os riscos associados aos custos de geração relacionados às diversas tecnologias consideradas, assim como os coeficientes de correlação entre elas. As participações dessas duas fontes renováveis na fronteira eficiente, tecnicamente viável, resultaram em portfólios bastante robustos, imunes às variações imputadas. / [en] The work compares current approaches for evaluating and planning Brazilian energy mixes for future power generation, based not only on energy cost components contribution to a portfolio, but on their contribution to portfolio risk, as well. Energy planners have traditionally used least-cost as a basis for generating capacity additions, understating the true value of non traditional renewable technologies for decreasing risk. This project applies widely accepted finance theory, Mean-Variance Portfolio Theory, developed by Harry Markowitz, to provide an economic basis for selecting alternative generating scenarios. First, Brazil`s expected future generating mix for 2030 as predicted by Empresa de Pesquisa Energética in its 2030 Brazilian Power Planning, published in 2006, is evaluated. This mix is referred to as the reference EPE scenario. The risk-return properties of Brazil`s expected EPE mix for the year 2030 is compared to other possible mixes on the projected efficient frontier. The model finds solutions that are superior to the EPE mix in that they reduce risk or cost or both, while including a greater share of wind and biomass from sugar cane in the mix. The basic findings of this analysis seem quite robust, and do not materially change the shape of the efficient frontier, where it is technically feasible, even when the risk parameter estimates and cost covariations are changed significantly in the sensitivity analysis.
36

"Geração Núcleo-Elétrica: retrospectiva, situação atual e perspectivas futuras" / NUCLEAR ENERGY FOR ELECTRICITY GENERATION: HISTORICAL ANALYSIS, NOWADAYS SITUATION AND FUTURE

Mongelli, Sara Tania 30 June 2006 (has links)
A primeira reação nuclear em cadeia autosustentada controlada foi obtida em 2 de dezembro de 1942. Daí em diante, o crescimento da energia nuclear, inicialmente estimulado por fins militares, foi rápido. Ás aplicações civis no setor da geração de eletricidade foram adquirindo, ao longo do tempo, um papel sempre mais importante nas matrizes energéticas de muitos paises. Em 1987, 418 reatores nucleares no mundo estavam produzindo eletricidade em escala comercial. Dois terços destes reatores eram localizados em 7 países: Estados Unidos, União Soviética, França, Reino Unido, Alemanha, Canadá e Japão. Nos anos 90, o setor nuclear experimentou um grande retardo, devido principalmente ao acidente de Chernobyl e a uma revisão otimista das perspectivas de esgotamento das reservas de petróleo e dos outros combustíveis fosseis. Em 2005 o número de reatores para geração de eletricidade em operação no mundo era de 441, não muito diferente do numero de reatores em operação em 1987. Neste panorama o primeiro objetivo deste trabalho é analisar o estado da arte da geração núcleo elétrica e do ciclo do combustível nos países acima mencionados, partindo de uma revisão histórica. O caso do Brasil é abordado também por ser o país onde este trabalho é desenvolvido. Uma vez concluído o quadro da geração núcleo elétrica a nível internacional, são analisadas as novas tecnologias no setor da geração núcleo elétrica e as tendências e as iniciativas para o futuro da utilização da energia nuclear. São também abordadas as principais questões que sempre acompanharam o debate sobre a energia nuclear: a segurança, o meio ambiente, a proliferação e o mais moderno conceito de desenvolvimento sustentável. É importante antecipar que o objetivo deste trabalho não é de julgar os acontecimentos e de influenciar a opinião do leitor a favor da energia nuclear, mas de selecionar materiais e dados para informar e assim fornecendo um texto que seja uma coleção de informações e sugestões de aprofundamentos e não uma fonte de polêmicas. / On December 2, 1942, man first initiated a self-sustaining nuclear chain reaction, and controlled it. Since then, nuclear energy development, firstly estimulated by military goals, was fast. But nuclear energy use for electricity production grew too, until becoming a very important energy source in the world energy mix. In 1987 there were in the world 418 nuclear reactors capable of producing commercially useful supplies of electricity. Over two thirds were in just seven countries: United States, Soviet Union, France, United Kingdom, Germany, Canada and Japan. In the 90s, nuclear energy development slowed down as a consequence of the Chernobyl accident and of the more optimistic evaluations of world oil resources. In 2005 the number of nuclear reactors commercially producing electricity amounted to 441, not much more than the 418 reactors operating in 1987. From this point of view, the primary scope of this work is to analyze the world pattern and the state of the art of nuclear power production focusing on the countries above mentioned. Brazil case is analyzed too, since this work has been developed there. Once this international outlook is concluded, the next step passes through the analyses of new technologies, tendencies and initiatives for the future development of nuclear energy. Since feelings run high in the debate about nuclear energy, some fundamental and fervent points are raised: security, environment, proliferation and sustainable development. Nevertheless, it is important to point out that effort has been made in this work not to take sides, but to be impartial in selecting materials and giving data. The scope is not to convert the reader to a pro-nuclear view but to inform and, in doing so, to provide a volume that is a textbook and not a piece of polemic.
37

Integration of electric vehicles in a flexible electricity demand side management framework

Wu, Rentao January 2018 (has links)
Recent years have seen a growing tendency that a large number of generators are connected to the electricity distribution networks, including renewables such as solar photovoltaics, wind turbines and biomass-fired power plants. Meanwhile, on the demand side, there are also some new types of electric loads being connected at increasing rates, with the most important of them being the electric vehicles (EVs). Uncertainties both from generation and consumption of electricity mentioned above are thereby being introduced, making the management of the system more challenging. With the proportion of electric vehicle ownership rapidly increasing, uncontrolled charging of large populations may bring about power system issues such as increased peak demand and voltage variations, while at the same time the cost of electricity generation, as well as the resulting Greenhouse Gases (GHG) emissions, will also rise. The work reported in this PhD Thesis aims to provide solutions to the three significant challenges related to EV integration, namely voltage regulation, generation cost minimisation and GHG emissions reduction. A novel, high-resolution, bottom-up probabilistic EV charging demand model was developed, that uses data from the UK Time Use Survey and the National Travel Survey to synthesise realistic EV charging time series based on user activity patterns. Coupled with manufacturers' data for representative EV models, the developed probabilistic model converts single user activity profiles into electrical demand, which can then be aggregated to simulate larger numbers at a neighbourhood, city or regional level. The EV charging demand model has been integrated into a domestic electrical demand model previously developed by researchers in our group at the University of Edinburgh. The integrated model is used to show how demand management can be used to assist voltage regulation in the distribution system. The node voltage sensitivity method is used to optimise the planning of EV charging based on the influence that every EV charger has on the network depending on their point of connection. The model and the charging strategy were tested on a realistic "highly urban" low voltage network and the results obtained show that voltage fluctuation due to the high percentage of EV ownership (and charging) can be significantly and maintained within the statutory range during a full 24-hour cycle of operation. The developed model is also used to assess the generation cost as well as the environmental impact, in terms of GHG emissions, as a result of EV charging, and an optimisation algorithm has been developed that in combination with domestic demand management, minimises the incurred costs and GHG emissions. The obtained results indicate that although the increased population of EVs in distribution networks will stress the system and have adverse economic and environmental effects, these may be minimised with careful off-line planning.
38

Supervised Learning for Sequential and Uncertain Decision Making Problems - Application to Short-Term Electric Power Generation Scheduling

Cornélusse, Bertrand 21 December 2010 (has links)
Our work is driven by a class of practical problems of sequential decision making in the context of electric power generation under uncertainties. These problems are usually treated as receding horizon deterministic optimization problems, and/or as scenario-based stochastic programs. Stochastic programming allows to compute a first stage decision that is hedged against the possible futures and -- if a possibility of recourse exists -- this decision can then be particularized to possible future scenarios thanks to the information gathered until the recourse opportunity. Although many decomposition techniques exist, stochastic programming is currently not tractable in the context of day-ahead electric power generation and furthermore does not provide an explicit recourse strategy. The latter observation also makes this approach cumbersome when one wants to evaluate its value on independent scenarios. We propose a supervised learning methodology to learn an explicit recourse strategy for a given generation schedule, from optimal adjustments of the system under simulated perturbed conditions. This methodology may thus be complementary to a stochastic programming based approach. With respect to a receding horizon optimization, it has the advantages of transferring the heavy computation offline, while providing the ability to quickly infer decisions during online exploitation of the generation system. Furthermore the learned strategy can be validated offline on an independent set of scenarios. On a realistic instance of the intra-day electricity generation rescheduling problem, we explain how to generate disturbance scenarios, how to compute adjusted schedules, how to formulate the supervised learning problem to obtain a recourse strategy, how to restore feasibility of the predicted adjustments and how to evaluate the recourse strategy on independent scenarios. We analyze different settings, namely either to predict the detailed adjustment of all the generation units, or to predict more qualitative variables that allow to speed up the adjustment computation procedure by facilitating the ``classical' optimization problem. Our approach is intrinsically scalable to large-scale generation management problems, and may in principle handle all kinds of uncertainties and practical constraints. Our results show the feasibility of the approach and are also promising in terms of economic efficiency of the resulting strategies. The solutions of the optimization problem of generation (re)scheduling must satisfy many constraints. However, a classical learning algorithm that is (by nature) unaware of the constraints the data is subject to may indeed successfully capture the sensitivity of the solution to the model parameters. This has nevertheless raised our attention on one particular aspect of the relation between machine learning algorithms and optimization algorithms. When we apply a supervised learning algorithm to search in a hypothesis space based on data that satisfies a known set of constraints, can we guarantee that the hypothesis that we select will make predictions that satisfy the constraints? Can we at least benefit from our knowledge of the constraints to eliminate some hypotheses while learning and thus hope that the selected hypothesis has a better generalization error? In the second part of this thesis, where we try to answer these questions, we propose a generic extension of tree-based ensemble methods that allows incorporating incomplete data but also prior knowledge about the problem. The framework is based on a convex optimization problem allowing to regularize a tree-based ensemble model by adjusting either (or both) the labels attached to the leaves of an ensemble of regression trees or the outputs of the observations of the training sample. It allows to incorporate weak additional information in the form of partial information about output labels (like in censored data or semi-supervised learning) or -- more generally -- to cope with observations of varying degree of precision, or strong priors in the form of structural knowledge about the sought model. In addition to enhancing the precision by exploiting information that cannot be used by classical supervised learning algorithms, the proposed approach may be used to produce models which naturally comply with feasibility constraints that must be satisfied in many practical decision making problems, especially in contexts where the output space is of high-dimension and/or structured by invariances, symmetries and other kinds of constraints.
39

A Decision Support System For Electricity Generation Investment

Alpagut, Merih Ayse 01 June 2010 (has links) (PDF)
In the recent years, ongoing debates in the mineral sector has shown that efficient use of natural resources is of vital importance as the use of minerals is essential for modern living. Especially, in the context of sustainable development, it is required that mineral resources should be exploited to maximize the contribution to the well being of current generation without depriving the potential for future generations to meet their own needs. The aim of this thesis is to develop a decision support system using system dynamics methodology where
40

Investigating The Co2 Emission Of Turkish Electricity Sector And Its Mitigation Potential

Ari, Izzet 01 February 2010 (has links) (PDF)
The rapid industrialization, population growth, urbanization and economic and social development cause many environmental problems, such as climate change which is the result of the increase in the emission of greenhouse gases (GHGs) especially CO2. Combustion of fossil fuels, particularly from electricity generation, has the major responsibility for CO2 emissions. Decreasing the amount of CO2 emission requires a significant shift from our present energy use pattern toward one of lesser reliance on fossil fuels. Using renewable energy sources is one of the ways to supply some of the electricity demand reducing the associated GHG emissions and thus decreasing the adverse effects of climate change. In this study, generated electricity associated CO2 emissions and the specific CO2 emission factors are calculated based on IPCC methodology for each fuel type and each thermal power plant for Turkey between 2001 and 2008. The electricity demand of Turkey is estimated to increase about 7% annually till to 2019. Based on the planned power plant data obtained from EMRA, it was found that the total electricity supply (planned + existing) will not be sufficient to provide the estimated demand between 2011 and 2019. To overcome supply deficiency problem, four different scenarios are developed and the mitigation potential of CO2 emission from electricity generation based on these scenarios are examined. The results from these scenarios show that there is a significant decrease in the amount of CO2 emission from electricity generation. Renewable Energy Scenario which is the best scenario in terms of mitigation of CO2 emissions, provides to mitigation of 192 millions of CO2 emissions between 2009 and 2019. with respect to BAU scenario

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