L’énergie thermique des mers (ETM) offre une alternative intéressante pour la réduction de l’utilisation des énergies fossiles. En utilisant le gradient de température présent entre l’eau de surface et l’eau en profondeur, il est possible de produire de l’électricité grâce à un cycle thermodynamique. Les expérimentations sont peu nombreuses à l’heure actuelle, en raison d’un coût relativement élevé. Une approche fondamentale est donc développée avec la création de modèles numériques en régime permanent et dynamique. Le modèle en régime statique a été développé à partir d’une description mathématique simplifiée des composants du cycle. Ce modèle permet une évaluation globale des performances du système, incluant le prélèvement et le rejet de l’eau de mer ainsi que le cycle thermodynamique. À partir de la modélisation statique, un modèle dynamique a été établi en appliquant la méthode des systèmes équivalents de Gibbs. Cet outil permet de décrire les phases de démarrage et d’arrêt, d’étudier la modulation de la puissance électrique délivrée au réseau et d’optimiser le cycle. Les résultats de simulations des différents modèles sont confrontés à la littérature et à des données expérimentales, afin d’avoir des éléments de validation. L’un des intérêts du modèle en régime dynamique est la possibilité d’effectuer une analyse de type « premier et second principe » du système. Une optimisation du fonctionnement du cycle est réalisée à partir de cette analyse. Des pistes d’améliorations sont proposées. L’optimisation est réalisée grâce au couplage du modèle dynamique avec l’outil Genopt. Les outils numériques développés permettront d’élaborer des stratégies de contrôle des installations. / Ocean Thermal Energy Conversion (OTEC) offers an interesting alternative for reducing the use of fossil fuels for energy generation. Using the temperature gradient present between the surface water and deep water, it is possible to produce electricity through a thermodynamic cycle. At present, the experiments are limited due to a relatively high cost. A fundamental approach is developed with the creation of numerical models in steady and dynamic state. The model in steady state has been developed from a simplified mathematical description of the components of the cycle. This model allows for an overall assessment of system performance including the withdrawal and discharge of the sea water, as well as the thermodynamic cycle. From the static model, a dynamic model was established using the method of the equivalent Gibbs systems. This tool is used to describe the start-up and shutdown, to study the modulation of the electrical power delivered to the network and to optimize the cycle. The simulation results of the different models are confronted with the literature and experimental data in order to have points of validation. One of the advantages of the model under dynamic conditions is the ability to perform an analysis of the "first and second principle" of the system. Optimization of the operation is carried out from this analysis. Possible improvements are proposed. An optimization of the cycle operation is carried out from this analysis. The optimization is done by coupling the dynamic model with the tool Genopt. The numerical tools developed will permit in addition to develop strategies to control of the power plants.

La croissance démographique, l'amélioration de la qualité de vie, et l'intensification des activités énergivores influent fortement sur la demande en énergie au travers de la consommation d'électricité sur un territoire. Le recours aux énergies fossiles constitue la solution la plus adoptée dans les milieux insulaires pour satisfaire cette demande. L'envers de cette méthode réside dans la quantité d'émissions de gaz à effet de serre générée au cours de la production d'énergie et la vulnérabilité de ces territoires. Les politiques actuelles ambitionnent l'atteinte de l'autonomie énergétique dans les milieux insulaires à moyen terme, et favorisent l'utilisation des énergies renouvelables pour restreindre les émissions de gaz à effet de serre. Ces travaux ont pour objet de quantifier les impacts environnementaux liés à la production d'électricité de La Réunion afin d'établir un diagnostic territorial. À partir de l'Analyse de cycle de vie et suivant les normes ISO 14044, les centrales de production d'électricité du territoire sont évaluées sous différents impacts environnementaux. La démarche adoptée a été de mettre en place un outil d'évaluation adapté à tout territoire, permettant d'identifier les étapes et les processus fortement contributeurs pour la production de 1 kWh électrique. Les résultats de ce diagnostic servent de points de repère pour élaborer les scénarios de production, établis dans une démarche de modélisation prospective. Huit scénarios proposés ont été développés pour répondre aux contraintes environnementales, techniques, sociales et économiques. / Population growth, the raising of the standard of living and quality of life, and energy-intensive activities are key parameters affecting the territory energy demand, through electricity consumption. To meet this demand, reliance on fossil fuels is the main adopted solution, particularly in insular context. The downside of this method is the large amount of greenhouse gas emissions (GHG) emitted, and vulnerability of the territories. Current policies are now in favor of the energy self-sufficiency as a medium-term objective, and put in place measures to support the use of sustainable energy sources to mitigate GHG emissions. This work aims to assess environmental impact of electricity production in Reunion island, to establish a territorial diagnosis. Based on a life cycle assessment approach, according to ISO 14044 standards, varying environmental impacts have been evaluated from existing power plants. An evaluating tool has been developed to identify the most emissive life cycle stage from 1 kWh electricity produced. The obtained results serve as a reference point to develop prospective scenarios. Eight scenarios have been presented and aim to satisfy environmental, technical, social and economic constraints.

In Uppsala CHP Plant, there are six pressure reducing valves to reduce the pressure from 15 to 3 bars, before six absorption heat pumps. During the process the energy is conserved but losses occur in form of exergy. The aim of this thesis is to reduce the losses of exergy. This can be done by letting turbines replace the pressure reducing valves. In this thesis an investigation has been done of the conditions today, the conditions after the change from pressure reducing valves to turbines and a comparison of three different types of turbine solutions. The three examined solutions are one turbine, several helical screw expanders and several small turbines in parallel with asynchronous generators. The six absorption heat pumps have been divided into two groups; one group of four and one group of two absorption heat pumps. An investigation of locations and space in nearby switchgears has been done for each group. Contacts with retailers of the examined turbine solutions have been taken to gather technical specifications. These technical specifications have been used to simulate the electricity production and the economical yield of each type of examined solution. The investigation shows that the best solution is the solution with several small turbines with asynchronous generators. It has lower investment cost (15 [MSEK]) and the best yield. The proposed solutions will have an installed capacity of 2.65 [MW] to a cost of 5 601 [SEK/kW]. The electric energy production will be 15.7 [GWh/year]. An investment is recommended to a future electric energy price around 400 [SEK/MWh]. Before an investment it is recommended to investigate how to optimize the regulation of the new system with absorptions heat pumps and turbines.

Operational performance of grid-connected microgrid with integrated solar photovoltaic (PV) electricity production and battery energy storage (BES) is investigated.  These distributed energy resources (DERs) have the potential to reduce conventionally produced electrical power and contribute to reduction of greenhouse gas emissions.  This investigation is based upon the DER’s techno-economic specifications and theoretical performance, consumer load data and electrical utility retail and distribution data.  Available literature provides the basis for DER specification and performance.  Actual consumer load profile data is available for residential and commercial consumer sector customers.  The electrical utility data is obtained from Mälarenergi, AB.  The aim is to investigate how to use simulations to specify a grid connected microgrid with DERs (PV production and a BES system) for two consumer sectors considering a range of objectives.  An open-source, MATLAB-based simulation tool called Opti-CE has successfully been utilized.  This package employs a genetic algorithm for multi-objective optimization.  To support attainment of one of the objectives, peak shaving of the consumer load, a battery operational strategy algorithm has been developed for the simulation.  With respect to balancing peak shaving and self-consumption one of the simulations supports specification of a commercial sector application with 117 kWp PV power rating paired with a lithium ion battery with 41.1 kWh capacity.  The simulation of this system predicts the possibility to shave the customer load profile peaks for the month of April by 20%.  The corresponding self-consumption ratio is 88%.  Differences in the relationship between the load profiles and the system performance have been qualitatively noted.  Furthermore, simulation results for lead-acid, lithium-ion and vanadium-redox flow battery systems are compared to reveal that lithium ion delivers the best balance between total annualized cost and peak shaving performance for both residential and commercial applications.

Orientador: Paulo de Barros Correia / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-17T16:25:54Z (GMT). No. of bitstreams: 1 Gomes_AlaiseGarcia_M.pdf: 1965182 bytes, checksum: a4a57857200e8e18940e105f851d2024 (MD5) Previous issue date: 2011 / Resumo: A repotenciação de usinas hidrelétricas visa aumentar a sua capacidade de geração, realizando melhorias na estrutura das usinas ou troca de equipamentos. É uma alternativa de custos baixos para aumentar a capacidade de geração quando comparada à construção de novos empreendimentos. A repotenciação, foco deste trabalho consiste em substituir as turbinas da usina. Com isto, aumenta-se o rendimento na geração de energia elétrica. No entanto, este rendimento não é constante ao longo da faixa de operação da máquina, podendo ser descrito por curvas, sendo que o formato delas dependente das características da turbina. Nesta dissertação, o objetivo é, dados vários perfis de possíveis curvas de eficiência de novas turbinas, determinar quais as melhores combinações de curvas que otimizariam a geração da usina de acordo com as características operativas da mesma. Para isto, um problema de otimização não linear inteiro misto foi formulado, e um modelo computacional utilizando um método de execução paralelo ao da Decomposição de Benders foi desenvolvido para a resolução do problema de otimização matemática. As simulações foram realizadas com dados fornecidos pela Companhia Hidro Elétrica do São Francisco (CHESF). Concluiu-se que o ideal para os patamares praticados seria uma repotenciação utilizando turbinas com perfis de curvas diferentes e não somente com um perfil / Abstract: The repowering of hydro power plants increases their generating capacity by improving the structure or changing equipment. It is a low cost alternative to improve the generation capacity comparing with the building of new plants. Repowering by changing the hydro-turbines is the focus of this work. By doing that, the efficiency of the energy generation process is improved but, the efficiency is not constant. It can be described by a curve. The curve shape depends on the turbine's characteristics. The aim of this work is, given some possible turbines curve shapes, determine the combination of curves that optimizes the power plant generation according to the plant operational characteristics. A mixed integer nonlinear programming was formulated and a parallel implementation of Bender's decomposition method was developed to solve the problem of mathematical optimization. Simulations were done with data given by the São Francisco's Hydroelectric Company (CHESF). It was concluded that the ideal would be charged to the levels using a repowering turbines with profiles of different curves and not only one profile / Mestrado / Mestre em Planejamento de Sistemas Energéticos

Orientadores: Sérgio Valdir Bajay, Moacyr Trindade de Oliveira Andrade / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-21T11:31:07Z (GMT). No. of bitstreams: 1 Dester_Mauricio_D.pdf: 5389676 bytes, checksum: 7c5e6ad30bbd780ddf1b9300f7cc4317 (MD5) Previous issue date: 2012 / Resumo: A eletricidade é bem de consumo e também insumo posicionado dentre aqueles considerados essenciais para a sociedade moderna. Neste contexto, o planejamento e a construção de uma matriz de energia elétrica é questão de importância capital não somente para o setor elétrico, como também para o desenvolvimento do Brasil. A constituição desta matriz deve ser pautada, sobretudo, pelo aspecto sustentabilidade. Neste sentido, sua concepção deve, imprescindivelmente, contemplar todas as perspectivas que permeiam o processo estratégico que a origina, a saber: técnica, econômica e sócio-ambiental. Somente balizado por estas óticas é possível proporcionar a expansão da oferta de energia elétrica de forma sustentável e com segurança no que concerne ao atendimento pleno da demanda, um requisito indispensável para que este serviço possa ser um sólido sustentáculo de um processo maior: o desenvolvimento socioeconômico da sociedade brasileira. A participação das fontes renováveis na matriz de energia elétrica é fator desejável e colabora, de forma meritória no que diz respeito aos impactos ambientais decorrentes da produção de eletricidade. Todavia, há algumas questões de ordem econômica e principalmente técnica as quais devem ser tratadas e lapidadas de forma a eliminar as lacunas existentes, permitindo que se possa estabelecer planos de expansão da oferta de eletricidade sustentáveis sob todos os pontos de vista. O objetivo principal deste trabalho é proporcionar e aprofundar o debate sobre estas questões e apresentar uma solução que propicie a integração das fontes renováveis na matriz de energia elétrica brasileira mantendo a confiabilidade no atendimento da carga. Outrossim, não somente os aspectos técnico e econômico foram contemplados na análise, mas, também o socioambiental, possibilitando assim oferecer subsídios para a evolução da oferta com orientação para a sustentabilidade. Para elaboração da proposta foi realizado um estudo abrangente sobre as principais fontes primárias a partir das quais é possível produzir eletricidade, além de uma revisão de todo o extenso e complexo caminho pelo qual passou o setor de planejamento da expansão desde seus primórdios até o modelo atual. São também apresentados vários pontos de vista sobre as dificuldades encontradas pelo planejador, desde os empecilhos de ordem regulatória, passando por aqueles oriundos de uma falta de coordenação dentre os setores do governo envolvidos no problema, até as questões de ordem ambiental. Por fim, no decorrer do trabalho e particularmente ao concluí-lo, propõe-se um conjunto de medidas estratégicas por intermédio das quais se pode construir uma matriz de energia elétrica segura e sustentável e lograr êxito, sob as perspectivas técnica, econômica e socioambiental, ao se realizar o planejamento da expansão da oferta, seja no horizonte de curto, médio ou longo prazos / Abstract: Electricity is not just a consumer good but also an input which commands a place amongst those goods considered essential to modern society. In this context, the planning and construction of an electricity matrix is a question of paramount importance, not just for the electricity sector but also for Brazil's development as a whole. The establishment of this matrix should, above all, be regulated with an emphasis on sustainability. In this regard, its conception must necessarily embrace all the perspectives that imbue the strategic process that gives rise to it: technical, economic and socio-environmental. Delimited by these viewpoints alone, it is possible to provide the sustainable expansion of an electric power supply that is also secure in terms of being able to fully meet demand. This is a fundamental prerequisite to this service becoming a solid base for a larger process, namely the socio-economic development of Brazilian society. The participation of renewable energy sources in the electric energy matrix is a desirable factor and contributes laudably to the mitigation of environmental impacts resulting from the electricity generation. Nevertheless, there are several issues of an economic and mainly technical nature which have to be dealt with and refined in order to close the existing gaps and enable plans to be established, that are sustainable from all points of view, for the expansion of an electric power supply. The main aim of this study is to prompt, and study in greater depth, the debate over these issues and present a solution that delivers the integration of renewable sources into Brazil's electricity matrix while maintaining reliability of load fulfillment. Similarly, not only were the technical and economic aspects covered in the analysis but also the socio-environmental aspects, thereby making it possible to provide support for the evolution of a sustainability-oriented supply. For the purposes of drafting this proposal, a wide-ranging study was conducted of the principal primary sources from which it is possible to generate electricity, as well as a review of the long and complex path which the expansion planning sector has taken, from its outset through to the current model. Various points of view are also put forward about the difficulties encountered by the planner, ranging from the regulatory obstacles to those arising from a lack of coordination between the government sectors involved in the problem and to issues of an environmental nature. Finally, throughout the study and in particular in its conclusion, a set of strategic measures is proposed through which a secure, sustainable electricity matrix can be constructed from a technical, economic and socio-environmental perspective, which is successful in carrying out supply expansion planning in the short, medium and long term / Doutorado / Planejamento de Sistemas Energeticos / Doutor em Planejamento de Sistemas Energéticos

Although energy transition is considered one of the main challenges of our time, little attention has traditionally been paid to the actors participating in this transition, such as the producers of renewable electricity. Previous energy policy literature and policy- makers have assumed that these producers are incumbent actors of the current energy system, that is to say, large utilities producing both renewable and fossil-fueled electricity. In reality, new types of producers are entering the renewable electricity production market, without much (if any) previous experience in that industry. This Licentiate thesis studies the new entrants of renewable electricity production in order to identify their motives, their responses to policies, and their ways of implementing their projects. This is conducted through the analysis of 37 cases of new entrants in Sweden. A theoretical background, a complete description of the methods, and an overall presentation of the findings are presented in the first part of the thesis, and in the second part of the thesis, four scientific papers studying the new entrants of renewable electricity production from complementary theoretical approaches are presented. Results show that the new entrant group is heterogeneous in several ways. They have different motives, they are affected by different drivers and pressures, and they are faced with different challenges during their entry processes. Despite that, their share of investments represents the majority of those currently being made in renewable electricity production in Sweden. Based on these results, policy implications are drawn and, in particular, the need for policy-makers and energy policy literature to acknowledge the particularities of the new entrants is highlighted.

Les émissions de gaz à effet de serre sont responsables du réchauffement climatique observé ces dernières décennies. Il est donc aujourd’hui indispensable de décarboner notre mode de vie, le secteur énergétique et notamment la production électrique. Les énergies renouvelables comme l’éolien et le photovoltaïque se sont fortement développées ces dernières années. Ces sources d’énergies présentent une contrainte majeure à leur développement : elles sont intermittentes et non pilotables pour équilibrer la demande. Plus la part de ces productions deviendra importante dans le mix électrique, plus les difficultés d’équilibrage de la demande deviendront problématiques.Dans ce travail doctoral, les productions éolienne terrestre et photovoltaïque ont été modélisées et corrigées suivant une distribution homogène à travers la France et l’Europe entre 1979 et 2015 d’après les réanalyses d’ERA-interim. Dans un second temps, un modèle simplifié d’équilibre entre l’offre renouvelable et la demande française (MSEOD) a été développé et appliqué sur la période des réanalyses ERA-interim de 1979 à 2015. Ce modèle vise à explorer le potentiel et les limites d’un foisonnement des énergies renouvelables suivant que le coût de l’électricité ou le volume d’énergie stocké est optimisé.Nous avons montré que la minimisation du coût de l’électricité (entre 186 et 194 e/MWh selon les scenarii) conduit à une faible surproduction (entre 10 à 20 %) avec d’importants moyens de stockage (puissance et volume d’énergie stockée - entre 20 et 81 heures de la consommation moyenne française), alors que le choix d’une minimisation du volume maximal d’énergie stockée conduit à une forte surproduction (entre 164 à 199 %) engendrant un coût de l’électricité environ deux fois supérieur (entre 373 et 488 e/MWh). Malgré une forte surproduction (proche de 200 % de la consommation moyenne), il est toujours nécessaire de disposer d’une puissance complémentaire (de déstockage et de production thermique) supérieure à la consommation moyenne pour permettre l’équilibrage de la demande lors de certains événements météorologiques dimensionnants le système. L’absence de contrainte du réseau sur les puissances importées permet de réduire d’un facteur 10 le volume maximal d’énergie stockée par rapport au cas d’une France en autarcie. La puissance complémentaire, nécessaire à l’équilibre de la demande française, n’est que marginalement réduite. Ce travail à montré que certains événements météorologiques conduisent à une très faible production renouvelable à l’échelle du contient européen. Le mix technologique optimal est fortement éolien, entre 68 à 100 % de la production renouvelable intermittente d’origine éolienne selon les scenarii et des LCOE testés. L’utilisation des coûts de production électrique plus faible (60 e/MWh pour le photovoltaïque et de 65 e/MWh pour l’éolien),conduit à un coût de l’électricité de l’ordre de 100 e/MWh pour une volume maximal du stockage correspondant à une journée de consommation moyenne. / Greenhouse gas emissions are responsible of the global warming observed in recent decades. It is therefore essential today to decarbonise our way of life, the energy sector and the production of electricity in particular. Renewable energies, such as wind and photovoltaic power, have developed strongly these last years. These sources of energy have a main constraint for their development : they are intermittent and non-controllable for balancing the demand. The share of these productions becomesimportant in the electricity mix, the larger the problems of balancing the demand will become.In this PhD study, terrestrial and photovoltaic wind generation were modeled and corrected according to an homogeneous distribution of capacities across France and Europe between 1979 and 2015 according to the ERA-interim reanalysis. In a second step, a simplified model of renewable supply and the French demand balancing (MSEOD) was developed and applied during the period of the ERAinterim reanalysis from 1979 to 2015. The aims of this model is to explore the potential and the limits of renewable energies balancing depending on the cost optimisation of electricity or the minimisation of volume of energy stored.During this PhD thesis, we have shown that the cost optimisation of electricity (between 186 and 194 euro / MWh according to the scenarii) leads to a low overproduction (between 10 to 20 %) with an important storage capacity (power and stored energy - between 20 and 81 hours of the average consumption), while the minimization of the maximum sizing of stored energy leads to a high overproduction (between 164 to 199 %) generating electricity costs about twice as large (between 373 and 488 euro / MWh). Despite a strong overproduction (close to 200 % of the average consumption), an additional power (destocking and thermal production) large than the average consumption is still necessary for balancing the demand during sizing meteorological events. The absence of constraint of imported powers on the network makes it possible to reduce the maximum size of stored energy by a factor of 10 as compared to the case of a self-sufficient French production. The additional power required for the balance of energy is little reduced. This work has shown that some meteorological sizing events lead to a very low renewable production at European scale. The optimal technological mix is highly wind-powered. Between 68 and 100 % of the intermittent production mix comes from wind production (depending of the scenarii and the LCOEs tested). The use of electricity production using smaller cost (60 e/MWh for photovoltaïque and 65 e/MWh for wind production), leads to an electricity cost around 100 e/MWh for a maximum storage volume corresponding to a day of the average consumption.

Increasing amounts of solar power connected to the low-voltage network will adversely affect the performance of the network. The two impacts that will most often set the limit are overvoltage with the customers and overloading the distribution transformer. In this work, alternative methods have been studied for determining when a transformer is overloaded, to allow more solar power to be connected to the low-voltage network, i.e., increasing the hosting capacity for solar power.A limit-based method on the highest temperature inside the transformer (the hotspot temperature) and a method based on the loss-of-life of the transformer insulation due to hotspot temperatures above the design temperature are those alternative methods in this study. These methods are known as "dynamic transformer rating", a technology proposed in the literature but with very little practical experience in distribution networks.Two models were developed and implemented in MATLAB: a thermal model of the transformer calculating the hotspot temperature for a given time series of loading and ambient temperature; and a model for the loss-of-life of the winding insulation for given time series of the hotspot temperature. These models have been applied to existing distribution networks: measured consumption patterns with high time resolution (10-minute time step) for nine different distribution transformers for 1.5 years (network operator); measured ambient temperature (SMHI); and solar-power production calculated from satellite measurements (Renewables Ninja).For these nine distribution transformers, the time series of the hotspot temperature and the loss-of-life over the 1.5 years have been calculated for different values of the solar power installed capacity on the low-voltage side of the distribution transformer. The resulting time series are used to estimate the hosting capacity for solar power of a 200 kVA transformer. Using the existing design methods, the hosting capacity is 200 kW. Once that value is reached, the further connection of solar power should be stopped until a larger transformer is available. According to IEC design methods, the hosting capacity is about 270 kW using a limit to the hotspot temperature. This value somewhat depends on the loading patterns of the transformer before the connection of solar power. Once that value is reached, the further connection should again be stopped. Even for installed capacity exceeding 270 kW, the loss of life of the transformer insulation is still small and acceptable. This allows for further connection of PV without the immediate need to replace the transformer. Even values up to 350 or 400 kW may be acceptable, but a limit based on loss-of-life will require a detailed risk analysis as the pre-solar loading of the transformer is shown to play an important role.This work has shown that dynamic transformer rating allows more solar power to be connected to a distribution network than using classical rating methods without unacceptable risk for transformer loss-of-life.

Master’s thesis focuses on renewable and alternative energy sources and their operation in the Czech Republic. First part of this work deals with legislative support of the renewable energy sources and with other related documents. Next chapters describe each kind of renewable energy sources and their contemporary energy market share. In this work there are also economic analyses of electricity and eventually heat productions which are produced on concrete plants by sources using renewable energy. There is a comparison between regular and renewable energy sources in the next chapter. Final evaluation of different energy sources and their possibilities of using are described in the final part of the thesis.