Dissertations / Theses on the topic 'Intermittent Renewable Energy'

The majority of electrical energy in the United States is produced by fossil fuels, which release harmful greenhouse gas emissions and are non-renewable resources. The U.S. Department of Energy has established goals for a smart electric power grid, which facilitates the incorporation of clean, renewable generation sources, such as wind. A major challenge in incorporating renewable energy sources onto the power grid is balancing their intermittent and often unpredictable nature. In addition, wind generation is typically higher at night, when consumer demand is low. Residential electric water heaters (EWHs), which currently account for 20% of the U.S. residential daily energy demand, are the largest contributors to the morning and evening peaks in residential power demand. The simulations in this thesis tested the hypothesis that controlling the thermostat setpoints of EWHs can shift EWH electrical energy demand from hours of higher demand to hours of lower demand, provide a large percentage of the balancing reserves necessary to integrate wind energy generation onto the electric power grid, and economically benefit the customer, while maintaining safe water temperatures and without significantly increasing average daily power demand or maximum power demand of the EWHs. In the experimental simulation, during on-peak hours for demand, when electricity prices are high, the thermostat setpoints of EWHs were set to the minimum, in order to consume minimal energy. The result was that the vast majority of EWH demand occurred during off-peak hours, a significant improvement over the base case (normal operation in which no setpoint control was implemented). During off-peak hours, the thermostat setpoints of EWHs were controlled by the utility in order to provide balancing reserves necessary to maintain power system stability when wind generation is included in the system. The EWHs were able to provide the balancing reserves desired by the utility a majority of the time. In this combined control method, the customer benefitted financially by saving in electrical energy costs when compared to the base case, the EWH water temperatures always remained within safe limits. There was only a small increase in the total energy consumption, but the peak power demand did not change.

Sweden’s municipalities are leading the green energy transition, in this study, a techno-economic evaluation was done for a number of carbon neutral scenarios for Växjö municipality’s future energy system, situated within Sweden’s projected energy demand development in 2030 and 2050. The municipality’s partially decentralized energy system relies heavily on interconnected electricity supply from the national grid, and fuels imports from other parts of Sweden. It was a matter of question: in which ways will future demand changes induce supply changes, and whether a future carbon neutral energy system will be less costly in a sustained-electricity supply condition? To answer this, a balanced energy reference system for the municipality was created from an actual energy balance, using an hour-by-hour dynamic energy analysis tool EnergyPlan. Afterward, a future energy demand projection for Växjö was stemmed from the Swedish Energy Agency (SEA) sustainable future scenarios for Sweden, based on an average inhabitant energy demand. Modelling results for Växjö carbon neutral scenarios showed that Växjö energy system will be sufficient to supply future heat demand but not electricity demand, nor transport and industrial fuels. While in the short-term being carbon neutral is more economically attainable without changes in electricity supply technologies, a projected electricity price and consumption increase, change the outcomes for a carbon neutral scenario based on Intermittent Renewable Energy (IRE) to be less costly in the long term.

Cette étude s’intéresse à la conception systémique intégrant simultanément les questions de dimensionnement et de gestion optimale de l'énergie. Le système étudié concerne un procédé de pompage intégrant un processus de dessalement d’eaux saumâtres alimenté par des sources de puissance hybrides renouvelable incluant un minimum de stockage électrochimique. Ce cas d’étude appartient à une classe typique de systèmes autonomes alimentés par des sources intermittentes dont profil de puissance a une forme "donnée" : « selon les conditions climatiques (ensoleillement, vent), avec un minimum de stockage d’électricité, la puissance offerte doit être convertie ou stockée hydrauliquement sous peine d’être gaspillée ». L'influence des conditions d'environnement et la robustesse du processus d’optimisation est enfin aussi discutée dans cette thèse. Deux types de modèles mathématiques, dynamiques et quasi-statiques, sont mis en œuvre pour décrire l'ensemble du dispositif. Le système est tout d’abord modélisé dynamiquement par Bond Graphs. Pour une simulation plus rapide, plus adaptée à l’optimisation globale du système, un modèle quasi-statique est créé pour être simulé dans l'environnement Matlab. Pour de tels dispositifs, étant donné une certaine puissance offerte au fil du vent et du soleil, trouver le point optimal de fonctionnement à chaque période consiste en un partage de puissance entre les sous systèmes de pompage et de traitement de l’eau : ce processus est plutôt complexe compte tenu des non linéarités (courbes rendement – puissance) et de la présence de nombreuses contraintes relatives aux limitations de puissance des pompes, aux conditions de niveau des réservoirs, ainsi qu’aux limitations de pression et de débit dans les processus hydrauliques (pompes osmoseur). Nous montrerons qu’il n’est pas si trivial de choisir une fonction objectif qui assure simultanément la performance et la robuste du système vis-à-vis des conditions d’environnement : une fonction objectif robuste quel que soit le profil de puissance des sources est ainsi proposée pour mettre en œuvre une gestion optimale de l’énergie. Le problème d’optimisation étant posé sous forme standard, consistant en la maximisation d’une fonction objectif sous contraintes, des approches d’optimisation efficaces par programmation non linéaire sont employées. La question du dimensionnement et son couplage à la gestion énergétique est finalement étudiée. En particulier, l’intérêt de la modularité des systèmes, considérant plusieurs pompes connectées en parallèle pour la même fonction, est investigué<br>This study focuses on systemic design, integrating simultaneously issues of sizing and optimal energy management. The system under study consists of a pumping process including a brackish water desalination system fed by hybrid renewable power sources with minimum electrochemical storage. Such a device belongs to the class of “autonomous systems” supplied by intermittent sources whose power profile has a “given” waveform: “with minimum electrical storage, power has to be converted, stored in water tanks, or wasted following climatic (sun, wind) conditions”. Influence of environment conditions and robustness of the optimization process is then also discussed in this thesis. Both dynamic and quasi static models are implemented for representing the whole system. The device is firstly modeled dynamically by Bond Graph methodology. For faster simulations, which are more suitable for system optimization, a quasi static model is created to be simulated in the Matlab environment. For such systems, given a certain source power, finding optimal operation point at each period consists of a power sharing between all pumping devices: it is a complex process with huge nonlinearities (efficiency vs power curves) and with many constraints as for the limitation of pump powers, tank level conditions, or pressure and flow limitations in hydraulic network and pumping devices. It is not so trivial to define an objective function which ensures system performance and robustness versus environment conditions: a convenient objective function, whatever the input power profile, is then proposed to implement the optimal management. The optimization problem being mathematically expressed, consisting of objective function maximization under constraints, efficient optimization methods by non linear programming are implemented. The issue of sizing and its coupling with system management efficiency is finally studied. In particular, the interest of modular operation with several pumps connected in parallel is also concerned in this research

Energy storage technologies have the potential to revolutionize the electric grid by allowing for the integration of renewable generation while increasing the utilization and efficiency of current grid assets. These technologies include pumped hydroelectric storage, compressed air energy storage (CAES), flywheels, batteries, thermal energy storage (TES), super capacitors, and superconducting magnetic energy storage (SMES). While energy storage has been implemented in some areas, its benefits are greatly undervalued by current regulatory frameworks leading to suboptimal outcomes for grid operators, utilities, and ratepayers. Large-scale adoption of storage technologies will require regulatory frameworks that recognize the benefits of grid-scale storage across generation, and transmission and distribution. This thesis discusses the need for storage, currently available and developing storage technologies, and the present regulatory environment.

A motivação para o desenvolvimento desse trabalho surge em um momento em que se verifica uma participação cada vez mais significativa das fontes energéticas renováveis não convencionais no País. Não obstante, o cenário de evolução evidencia que o arcabouço regulatório e as regras de mercado não acompanharam as especificidades inerentes à exploração dessas fontes. Assim, para que se mantenha adequado ritmo de inserção na matriz energética, devem ser buscadas opções para que fontes alternativas sejam cada vez mais competitivas na atual configuração do mercado energético. A contribuição dessa pesquisa, portanto, centra-se na análise dos riscos de mercado incorridos por esses geradores de fontes intermitentes de energia ao comercializarem energia no ambiente de contratação livre. Nessa perspectiva, a Dissertação foi desenvolvida abordando tipos de geração de energia e suas características técnicas e econômicas, legislação do setor elétrico, regras de comercialização, balanço energético do sistema, formação de preços no mercado de curto prazo e precificação de contratos no ACL, diferença de preços entre submercados, requisitos de flexibilidade e sazonalidade nos contratos de venda a consumidores livres e seu impacto na precificação de contratos, identificação de comportamento energético complementar para mitigação de riscos de mercado entre fontes renováveis e rebatimento na formulação de mecanismo de hedge, análise de portfólio de contratos e estratégia ótima de contratação de energia para agentes geradores atuando no ACL. Como resposta ao desafio de equacionar o impasse surgido na comercialização de fontes de produção sazonal, propõe-se um modelo para definir estratégias de contratação para agentes geradores e comercializadores a partir da complementação energética entre diferentes tipos de fontes, de forma a maximizar os ganhos de comercialização para um risco estabelecido. Busca-se a composição ideal dessas fontes na carteira de um comercializador para minimizar o risco de exposição à volatilidade dos preços do mercado de curto prazo. Isso é possível em virtude das compensações energéticas feitas entre as diferentes fontes em um portfólio combinado, mitigando a receita em risco decorrente das variações que existem nos preços de curto prazo e na produção energética. De forma complementar, estruturou-se um modelo de negócio no qual uma empresa detentora de ativos de geração hidrelétrica compra os direitos de produção de uma eólica e/ou biomassa para incorporar ao seu portfólio e vender como contrato por quantidade. Determinou-se o volume de energia a ser comprado de cada fonte, o preço, a estratégia mais indicada de contratação e a mitigação de fatores de risco contemplados nos contratos de venda, buscando maximizar os ganhos de comercialização condicionada a critérios de risco pré-fixados.<br>The motivation to write this thesis has arisen at a time when the participation of nonconventional renewable sources in the Brazilian electric energy matrix has become more significant. However, the scenario of the regulatory framework and market rules has not followed the specificity of the nature of these sources. In order to maintain a higher growth rate in the national electric matrix, non-conventional renewable sources must find alternatives to the current electric market. The contribution of this study focuses on the market risks analysis incurred by intermittent energy sources to commercialize energy in the free market. From this perspective, the study was developed addressing types of power generation and its technical and economic characteristics, legislation in the electricity sector, commercialization rules, system energy balance, spot market and long term contract pricing, difference prices between submarkets, flexibility requirements and seasonality in sales contracts to free consumers and their impact on contract pricing, identify complementary energy behavior for mitigating market risks from renewable sources and formulation of \"hedge\" mechanism, portfolio analysis and optimal strategy of energy contracting for generating agents acting in the ACL. In response to the challenge of solving the impasse in the commercialization of seasonal production sources, a model for contracting strategies was proposed for generation companies and retailer agents from the energy complementation between different types of sources in order to maximize the gains of marketing to an established risk. This allows revenues increase while mitigating risks in a scenario where spot prices and energy production vary greatly. An arrangement that provides the minimum risk was identified for retailer portfolio. This is possible due to differences amongst each source considered in the simulations, compensating the results in a diversified portfolio. As a complement, a business model was structured in which a generation company with hydro power assets purchases production rights of a wind and / or biomass to incorporate to its portfolio and sell as contract \"for quantity.\" It was determined the amount of energy to be purchased from each source, the price, the best contracting strategy and mitigation of risk factors included in sales contracts, seeking to maximize the revenue giving an acceptance of risk.

Arbetet Tillämpning av batterilager som energitjänsten lastutjämnare är en litteraturstudie och en kvantitativ studie. I studien har driftkarakteristiken år 2015 hos en matvarubutik legat till grunden. Arbetet har syftat i att besvara frågan kring ett batterilagers lämplighet som agerade för lastutjämning. För att ta reda på det har batterilagersegenskaper kartlagts och dimensionering gjorts utifrån två olika driftfall. En ekonomisk besparingspotential har även beräknats utifrån de bägge driftfallen. Driftfallen har valts att kallas teknisk dimensionering och ekonomisk dimensionering. De tekniska dimensionerade lagerna har en lager storlek om 617 kWh och 555kWh vilket motsvarar 7,1% respektive 5,8% av den dagliga energianvändningen. För de ekonomiskt dimensionerade lagerna har en lager storlek om 597 kWh och 233kWh vilket motsvarar 6,8% respektive 2,8% av den dagliga energianvändningen. Den ekonomiska besparingspotentialen blir som störst för en blandad körning av de bägge driftfallen. Trotts att besparingspotentialen är uppskattade under ideala förhållanden med varken förluster eller degraderad prestanda lönar det inte sig att investera i ett batterilager för att enbart utföra tjänsten effektutjämning idag. Investering i ett batterilager för effektutjämning har potential att bli lönsam först när den kan tillgodose fler energitjänster eller när alternativkostnaden är förhöjd.<br>This thesis, is a study of battery energy storage and its use as energy source and smoothening of power fluctuation. Studies have been made as a systematic review and a quantitative study. The study has consisted of analysing the power characteristic from a supermarket in the city of Varberg during year 2015. The object has been to evaluate the energy storage and the power smoothing qualities. Therefore the battery energy storages characteristics have been evaluated in this systematic review. For the quantitative study, calculations of the energy storage sizes were made for two separate operation modes. The two different operation modes were named technical dimensioning and economic dimensioning. The function of the technical dimensioning was to smooth the power outlet from the grid, while the function of the economic dimensioning was to enable the supermarket to buy more energy during low-price hours. Based on monthly power characteristics, each dimensioning gave as a result two energy storage possibilities, one in medium and one in small size. The technical dimensioning resulted in battery energy storage of the sizes 617 kWh and 555kWh which is comparable to 7,1% and 5,8% of the daily energy usage of the supermarket. The economic dimensioning resulted in battery energy storage of the sizes 597 kWh and 233kWh which is comparable to 6,8% and 2,8% of the daily energy usage of the supermarket. For optimizing the economic savings, a variation of technical and economic operation mode are needed, depending on calculated power usage through the day and elspot prices. The study shows that a battery storage is difficult to finance. The calculated economic savings were estimated during ideal conditions and without power loss or loss in performance. As a conclusion from this study a battery storage may have a good payback if there are several energy services to be filled.

A nivell mundial les energies renovables han crescut de forma considerable al llarg d'aquestes dues últimes dècades, havent substituït parcialment als combustibles fòssils en àmbits tals com la generació elèctrica. Una aposta tan àmplia per aquest tipus d'energies només s'explica des del punt de vista de les importants i creixents avantatges associats a aquest tipus de tecnologies en tres àmbits fonamentals: el medi ambient, la seguretat de subministrament energètic i el desenvolupament econòmic. No únicament contribueixen a la reducció d'emissions de gasos d'efecte hivernacle donat el seu caràcter renovable sinó que addicionalment milloren la seguretat de subministrament, prenent en consideració que es tracta de fonts energètiques autòctones. Així mateix, les energies renovables suposen un important motor de desenvolupament econòmic i social, fomentant la innovació i la generació de llocs de treball d'elevat valor afegit. No obstant això, aquesta ràpida penetració de les energies renovables planteja desafiaments al sistema elèctric en particular que ha d'adaptar-se a una creixent generació descentralitzada i de caràcter variable. Des de la perspectiva dels respectius sistemes elèctrics i la seva operació, el problema a solucionar és com integrar en el sistema un contingent considerable de generació d'origen renovable, la disponibilitat del qual és aleatòria, de localització lliure i que, davant situacions d'inestabilitat, es desconnecta del propi sistema elèctric, obligant a la resta de generació a incrementar la seva quota de participació en temps real amb la finalitat de garantir el permanent equilibri entre oferta i demanda que tot sistema elèctric exigeix per al seu correcte funcionament. La present Tesi aborda en profunditat del disseny actual del mercat elèctric i de l'impacte econòmic de les energies renovables en el preu final de l'electricitat que paguen els consumidors, prestant una especial atenció als mercats d'ajust, imprescindibles per al desenvolupament i implementació de les energies renovables.<br>A nivel mundial las energías renovables han crecido de forma considerable a lo largo de estas dos últimas décadas, habiendo sustituido parcialmente a los combustibles fósiles en ámbitos tales como la generación eléctrica. Una apuesta tan amplia por este tipo de energías sólo se explica desde el punto de vista de las importantes y crecientes ventajas asociadas a este tipo de tecnologías en tres ámbitos fundamentales: el medio ambiente, la seguridad de suministro energético y el desarrollo económico. No únicamente contribuyen a la reducción de emisiones de gases de efecto invernadero dado su carácter renovable sino que adicionalmente mejoran la seguridad de suministro, tomando en consideración que se trata de fuentes energéticas autóctonas. Asimismo, las energías renovables suponen un importante motor de desarrollo económico y social, fomentando la innovación y la generación de puestos de trabajo de elevado valor añadido. No obstante, esta rápida penetración de las energías renovables plantea desafíos al sistema eléctrico en particular que debe adaptarse a una creciente generación descentralizada y de carácter variable. Desde la perspectiva de los respectivos sistemas eléctricos y su operación, el problema a solucionar es cómo integrar en el sistema un contingente considerable de generación de origen renovable cuya disponibilidad es aleatoria, de localización libre y que, ante situaciones de inestabilidad, se desconecta del propio sistema eléctrico, obligando al resto de generación a incrementar su cuota de participación en tiempo real con el fin de garantizar el permanente equilibrio entre oferta y demanda que todo sistema eléctrico exige para su correcto funcionamiento. La presente Tesis aborda en profundidad del diseño actual del mercado eléctrico y del impacto económico de las energías renovables en el precio final de la electricidad que pagan los consumidores, prestando una especial atención a los mercados de ajuste, imprescindibles para el desarrollo e implementación de las energías renovables.<br>At a global scale, the use of renewable energy has grown considerably over the last two decades, having partially replaced fossil fuels in many areas such as electricity generation. Such a broad commitment to this kind of energy can only be explained by the significant and growing benefits associated with this type of technology in three key areas: environment, security of energy supply and economic development. These new energy sources not only contribute to reducing emissions of greenhouse gases - given its renewable nature - but also improve security of supply, as they use domestic energy sources. In addition, renewable energies are key to economic and social development, encouraging innovation and the creation of high added value jobs. Nevertheless, the rapid deployment of renewable energy already poses challenges for the electricity system in particular, which needs to adapt to increasingly decentralised and variable renewable generation. From the perspective of electrical systems and their operation, the problem to be solved is how to integrate generation from renewable sources into the system when availability is random, freely located and taken into account that when faced with unstable conditions disconnects itself from its own electrical system, forcing the rest of the generation to increase its share in real time to ensure the permanent balance between supply and demand called for by any electrical system for proper operation. This Thesis aims to take a close look at the current design of the electricity market and the economic impact of renewable energy on the final price of electricity paid by consumers, paying particular attention to adjustment markets, essential for the development and deployment of renewable energy.

A key problem with solar energy is intermittency: solar generators produce only when the sun is shining, adding to social costs and requiring electricity system operators to reoptimize key decisions. We develop a method to quantify the economic value of large-scale renewable energy. We estimate the model for southeastern Arizona. Not accounting for offset carbon dioxide, we find social costs of $138.40 per megawatt hour for 20 percent solar generation, of which unforecastable intermittency accounts for $6.10 and intermittency overall for $46.00. With solar installation costs of $1.52 per watt and carbon dioxide social costs of $39.00 per ton, 20 percent solar would be welfare neutral.

Introducing more intermittent renewable energy sources in the energy system makes the role of balancing power more important. Furthermore, an increased infeed from intermittent renewable energy sources also has the effect of creating lower and more volatile electricity prices. Hence, investing in balancing power is prone to high risks with respect to expected profits, which is why a good representation of electricity prices is vital in order to motivate future investments. We propose a stochastic multi-factor model to be used for simulating the long-run dynamics of electricity prices as input to investment valuation of power generation assets. In particular, the proposed model is used to assess the impact of electricity price dynamics on investment decisions with respect to balancing power generation, where a combined heat and power plant is studied in detail. Since the main goal of the framework is to create a long-term representation of electricity prices so that the distributional characteristics of electricity prices are maintained, commonly cited as seasonality, mean reversion and spikes, the model is evaluated in terms of yearly duration which describes the distribution of electricity prices over time. The core aspects of the framework are derived from the mean-reverting Pilipovic model of commodity prices, but where we extend the assumptions in a multi-factor framework by adding a functional link to the supply- and demand for power as well as outdoor temperature. On average, using the proposed model as a way to represent future prices yields a maximum 9 percent overand underprediction of duration respectively, a result far better than those obtained by simpler models such as a seasonal profile or mean estimates which do not incorporate the full characteristics of electricity prices. Using the different aspects of the model, we show that variations of electricity prices have a large impact on the investment decision with respect to balancing power. The realized value of the flexibility to produce electricity in a combined heat and power plant is calculated, which yields a valuation close to historical realized values. Compared with simpler models, this is a significant improvement. Finally, we show that by including characteristics such as non-constant volatility and spiky behavior in investment decisions, the expected value of balancing power generators, such as combined heat and power plants, increases.<br>I takt med att fler intermittenta förnyelsebara energikällor tillför el i dagens energisystem, blir också balanskraftens roll i dessa system allt viktigare. Vidare så har en ökning av andelen intermittenta förnyelsebara energikällor även effekten att de bidrar till lägre men också mer volatila elpriser. Därmed är även investeringar i balanskraft kopplade till stora risker med avseende på förväntade vinster, vilket gör att en god representation av elpriser är central vid investeringsbeslut. Vi föreslår en stokastisk flerfaktormodell för att simulera den långsiktiga dynamiken i elpriser som bas för värdering av generatortillgångar. Mer specifikt används modellen till att utvärdera effekten av elprisers dynamik på investeringsbeslut med avseende på balanskraft, där ett kraftvärmeverk studeras i detalj. Eftersom huvudmålet med ramverket är att skapa en långsiktig representation av elpriser så att deras fördelningsmässiga karakteristika bevaras, vilket i litteraturen citeras som regression mot medelvärde, säsongsvariationer, hög volatilitet och spikar, så utvärderas modellen i termer av årlig prisvaraktighet som beskriver fördelningen av elpriser över tid. Kärnan i ramverket utgår från Pilipovic-modellen av råvarupriser, men där vi utvecklar antaganden i ett flerfaktorramverk genom att lägga till en länkfunktion till tillgång- och efterfrågan på el samt utomhustemperatur. Vid användande av modellen som ett sätt att representera framtida priser, fås en maximal över- och underprediktion av prisvaraktighet om 9 procent, ett resultat som är bättre än det som ges av enklare modellering såsom säsongsprofiler eller enkla medelvärdesestimat som inte tar hänsyn till elprisernas fulla karakteristika. Till sist visar vi med modellens olika komponenter att variationer i elpriser, och därmed antaganden som används i långsiktig modellering, har stor betydelse med avseende på investeringsbeslut i balanskraft. Det realiserade värdet av flexibiliteten att producera el för ett kraftvärmeverk beräknas, vilket ger en värdering nära faktiska realiserade värden baserade på historiska priser och som enklare modeller inte kan konkurrera med. Slutligen visar detta också att inkluderandet av icke-konstant volatilitet och spikkarakteristika i investeringsbeslut ger ett högre förväntat värde av tillgångar som kan producera balanskraft, såsom kraftvärmeverk.

<p> Increased share of Renewable Energy Sources (RES) in the generation mix requires higher flexibility in power system resources. The intermittent nature of the RES calls for higher reserves in power systems to smooth out the unpredictable power fluctuations. Grid-tied energy storage systems are practical solutions to facilitate the massive integration of RES. The deployment of Battery Energy Storage Systems (BESS) on the power grids is experiencing a significant growth in recent years. Thanks to intensive research and development in battery chemistry and power conversion systems, BESS costs are reducing. However, much more advancements in battery manufacturing as well as additional incentives from the market side are still needed to make BESS a more cost-effective solution. Planning and operation of the BESS significantly influence its profitability. It is quite important to find optimal sizes of batteries and inverters. Sizing of the BESS for two different applications is addressed in this work. In the first application, the BESS is co-located with Pumped Storage Hydro (PSH) to meet the Day-Ahead (DA) schedule of wind generation. In the second application, a method for BESS sizing in the presence of PV-induced ramp rate limits is proposed. In this thesis, two methods based on Receding Horizon Control (RHC) for the optimal operation of the BESS are introduced. A co-located BESS and wind farm is considered in both methods. In one method, electricity market participation is not considered, and the goal is solely meeting the DA schedule utilizing the BESS. A novel predictive control method is proposed in this part and the efficiency of the method is evaluated through long-run simulations using actual historical wind power. </p><p> In the second scenario, market participation of the BESS is taken into account. The deviation from the DA schedule can be compensated through the BESS, or by purchasing power from the real-time electricity market. The optimization problem based on physical and operational constraints is developed. The problem is solved through an RHC scheme while using updated wind power and electricity price forecasts. In this thesis, a Ridge-regression forecast model for electricity price and an ARIMA forecast model for wind power are developed. Simulation results using actual historical data for wind power and electricity price demonstrate that the proposed algorithm increases the average daily profit. In order to evaluate the impact of the BESS lifetime and price on average daily profit, different scenarios are defined and simulated. Although they increase the complexity of the problem, much more realistic result might be obtained when all details and constraints are considered. </p><p>

The growing share of installed wind power in the Swedish electricity system has caused concerns whether the available regulating power will be sufficient. Several studies have examined the need of regulating power using both statistical and modelling approaches. However, there is a risk that some aspects of the short-term regulation of hydropower might have been missed. By using one of Vattenfall’s hydropower planning tools, the short-term operation of The Lule River has been simulated with an increasing penetration of wind power. The tool includes detailed models of reservoirs, generating units including efficiency curves and start/stop costs. By introducing a day-by-day simulation with a seven-day window price forecast, updated with a new wind forecast for each iteration, a 21-days scenario has been simulated. Transmission limits are disregarded and the thermal production is reduced with the average wind production. To quantify and compare the regulation capacity, the regulation factor is introduced. It reflects the ability to utilise high-price hours and considering that the need of regulating power for the short-term perspective is reflected in the price it will also reflect the regulation capacity. It is shown that the regulating factor is correlated to the discharge factor,whichis the relation between the maximum discharge to the average statistical discharge for a plant. A high discharge factor provides the flexibility to utilise the fluctuations in price. The discharge factor is adapted to the plants placement in the reach, accounting for both reservoirs located upstream and downstream, especially for The Lule River which has been designed to regulate for the fluctuations in the load. The flexibility required by the rest of the Nordic rivers is quantified for future studies. It is concluded that The Lule River is able to meet some of the fluctuations of wind power production due to the overcapacity ininstalled power. The production can, at the expense of decreased efficiency of the generating units, alter the production to suit a more fluctuating price.It is important to emphasise that The Lule River alone cannot balance a large penetration of wind power. To fully take into account the effects of a large penetration of wind power the study must be expanded to include more scenarios. The study should include different types of hydrological prerequisites and the seasonal variations in power production as well as additional rivers.

The widespread deployment of renewable energy in combination with smart grid technologies is creating the opportunity for energy storage to play a critical role in energy systems and be a more prevalent technology in the near future. This research adopts a bottom-up approach to model the in­teractions within the energy system, namely between renewable supply and storage technologies at the end-user level (e.g. in houses, buildings and com­munities). That is, the papers presented in this thesis investigate the value of energy storage in smart grids from an end-user perspective. Specifically, it focuses on the role of storage units in the regulation of the energy system’s supply-demand balance and the cost savings for the end-user. Hence, the contribution of this study lies in the perspective taken (end-user), as well as in the models developed for the valuation of energy storage. In this sense, it provides an understanding of different aspects associated with the valuation of storage technologies in smart grids. Particular attention is paid to the contribution of local wind energy supply as well as demand response (smart grids). Analytics data-driven optimization is central in this research. To analyze the interactions on complementing energy storage with decen­tralized energy system in smart grids, this thesis develops models for two real-life case studies: The first paper assess the value of batteries in domes­tic houses in sync with on-site renewable micro generation. A second paper extends the research, bottom-up, to a community dependent on its own hybrid decentralized generation coupled with energy storage units. As un­certainty of wind generation is not considered in these cases, a third paper investigates the storage valuation by a stochastic programming approach.

This work deals mainly with electrical energy. In the first part is focused on alternative energy sources, and describes structure of consumption and production of electricity over the past few years, during which is focuses on renewable energy sources. In this context, assesses the conditions for alternative energy sources in the Czech Republic from the perspective of the legislative, as well as current status and potential of alternative energy sources and tries to predict the development of these issues. The next section describes the Smart Grids as a means to achieve these goals. There are presented the basic features of this system, its goals and challenges, a description of the integration of Smart Grids with other sources of electricity and the benefits of using Smart Grids both from the perspective of user and from the perspective of system. Other parts are focused on distributed control systems in the energy sector, its development and principle. The last part is devoted to consideration of the role of alternative energy sources and distributed generation in Smart Grids.

Världens energibehov förväntas ökar samtidigt som miljökraven blir allt hårdare. För att komma till rätta med klimatförändringarna och utsläppen av växthusgaser måste användningen av fossila bränslen minska samtidigt som energieffektiviseringar och förnybara energikällor måste öka. En större andel intermittenta förnybara energikällor på elmarknaden medför utmaningar. Finns det inget elbehov då det exempelvis blåser eller när solen skiner går den producerade elen förlorad, detta leder till att produktion och konsumtion av elektricitet måste ske samtidigt. För att förnybar energi ska kunna expandera men också effektiviseras måste samhället utveckla smarta elnät. Det finns olika uppfattningar vad som krävs för att skapa smarta elnät men elektrisk energilagersystem återkommer ofta i litteraturen. Det finns forskare som anser att satsning på intermittenta förnybara energikällor inte är ett alternativ om inte energin går att lagra. Compressed air energy storage är ett energilager som använder komprimerad luft för att lagra energin tills det finns ett behov. Industrin i Sverige står för drygt en tredjedel av den totala energianvändningen. Över 90 % av tillverkningsindustrin använder tryckluft. Det finns stora och små förbrukare av tryckluft beroende på användningsområde.  I denna studie kommer en internationell nulägesbeskrivning ges i utvecklingen av smarta elnät med fokus på elektriska energilagersystem. Syftet är att studien ska vara ett diskussionsunderlag, en informationsbärare och idéskapare. Den internationella nulägesbeskrivningen baseras på studiebesök, litteratursammanställning samt intervjuer. Resultatet från den internationella nulägesbeskrivningen visar att intresset för elektriska energilagersystem ökar då det är en central del i utvecklingen av smarta elnät.  Mellan 2011-2013 ökade investeringarna i elektriska energilager med 521 %. En anledning till denna ökning är den internationella trenden med microgrids och mindre decentraliserade kraftverk. Med ökad efterfrågan på energilagringssystem kommer nya energilagringssystem skapas och befintliga system utvecklas. Syftet med studien är även att undersöka om energilager är en lösning till hållbar tryckluftsförsörjning inom industrin. Målet är att dimensionera ett luftningssystem bestående av vindkraftverk och energilager, med en viss volym och maxtryck, för en stor- och liten tryckluftsförbrukare. I studien kommer även kostnadsbesparingen för den stora förbrukaren optimeras genom arbitrage. Dimensioneringen görs utifrån simuleringar i Simulink och optimering görs i MATLAB. Dimensionerat luftningssystemet för den stora tryckluftsförbrukaren består av ett vindkraftverk, ett energilager på 200 m3 med maxtryck på 10 bar. Täckningsgraden, det vill säga andelen av luftbehovet som kan täckas med vindkraft tillsammans med ett energilager, är 26 % för det dimensionerade luftningssystemet. Resultatet ger då 48 % mindre energiförbrukning, cirka 1,2 miljoner kronor i kostnadsbesparing och en miljövinning motsvarande 532 ton CO2-ekvivalenter. Kostnadsbesparing, då el köps via arbitrage, för den stora förbrukaren optimeras till maximalt 1,2 miljoner kronor. Generatorn har då en verkningsgrad på 85 % och kompressorn 90 %. Dimensionerat luftningssystemet för den mindre tryckluftsförbrukaren består av en vindsnurra, ett energilager på 20 m3 med maxtryck på 30 bar. Täckningsgraden, det vill säga andelen av luftbehovet som kan täckas med vindsnurra tillsammans med ett energilager, är 61 % för det dimensionerade luftningssystemet. Resultatet ger då 93 % mindre energiförbrukning, cirka 26 tusen kronor i kostnadsbesparing och en miljövinningen motsvarande 10,7 ton CO2-ekvivalenter. Skillnaden mellan en vindsnurra och ett vindkraftverk är att vindsnurran inte producerar el utan använder rörelseenergin direkt. Ett system bestående av energilager som drivs av energi från vinden lämpar sig bättre för ett mindre tryckluftsbehov där det går att nå upp i högre täckningsgrad. Övergången till smarta elnät är nödvändigt för att tillgodose alla aspekter av hållbar utveckling. Det är ingen del av smarta elnät som är viktigare än någon annan. En hållbar tryckluftanvändning inom industrin är en del av smarta elnät och för att göra det möjligt har energilager en avgörande roll. Nulägesbeskrivningen visar att det i dagsläget finns ett ökat intresse för EES internationellt men att det inte finns ett EES som ensamt kommer lösa integrationen av förnybar energi. Tekniken för energilagring finns idag och växer imorgon.<br>The world’s energy demand is expected to increase and at the same time the environmental requirements are becoming stricter. To deal with the climate change and the greenhouse gas emissions, the use of fossil fuel need to decrease, while the energy efficiency and renewable energy production must increase. A greater share of intermittent renewable energy on the electricity market entails challenges. If there is no need for electricity when the wind is blowing or when the sun is shining the electricity is lost, this leads to production and consumption of electricity must occur simultaneously. To expand the renewable energy and make it more efficient, society must develop a smart grid. There are different opinions about what it takes to create smart grids, but electrical energy storage, EES, reappears frequently in the literature. There are even scientists who believe that investment in intermittent renewable energy sources is not an option unless energy can be stored. Compressed air energy storage is a technique that uses compressed air to store energy until there is a demand.   The Swedish industry accounts for over a third of total energy consumption in the country. Over 90 % of the all manufacturing industry uses compressed air. There are big and small users of compressed air depending on the industry.  In this study, an international status description is given in the development of smart grids with a focus on electrical energy storage systems. The aim of this study is to be an information carrier that creates discussion and new ideas. The international status description is based on field visits, literature surveys and interviews. The results from the international status description shows that interest in electric energy storage systems is increasing since it is a central part in the development of smart grids. Between 2011 and 2013 the investments increased in electrical energy storage with 521 %. One reason for this increase is the international trend of micro grids and small decentralized power plants. With the increased demand for energy storage, new energy storage systems are created and existing systems evolve. The purpose of the study is also to examine if energy storage is a solution for a sustainable supply of compressed air in the industry. The goal is to design a compressed air system consisting of wind turbines and energy storage with a certain volume and maximum pressure, for a large and a small compressed air consumer. The study will also determine the cost saving for the big users is an optimized through arbitrage. The design is based on simulations in Simulink and the optimization is done in MATLAB. The selected compressed air system for the large consumer is based on one wind turbine, energy storage of 200 m3 with a maximum pressure of 10 bar. The coverage ratio, i.e. the proportion of the air need that is covered by wind energy with energy storage, is 26 %. An investment in this system would give reduced energy consumption by 48 % leading to a cost reduction of about 1.2 million SEK and a reduced environmental impact equivalent to 532 tons of CO2-equivalents. The generator then has an efficiency of 85 %, and the compressor has 90 %. The selected compressed air system for the smaller consumer achieves a coverage rate of 61 % with the following dimensions; one windmill, energy storage of 20 m3 and maximum pressure of 30 bar. An investment in this system would give a reduced energy consumption by 93 %, leading to a cost reduction of about 26 000 SEK and a reduced environmental impact equivalent to 10.7 ton of CO2 equivalents. The difference between a windmill and a wind turbine is that the windmill does not produce electricity instead it uses kinetic energy directly. A system consisting of energy storage driven by energy from the wind is more suited for smaller air requirements where it is possible to achieve greater coverage. The transition to smart grids is necessary to be able to meet all aspects of sustainable development. There is no part of smart grids that is more important. Sustainable use of compressed air in industry is a part of smart grids and to make it possible energy storage is crucial. The international status description shows that there is a growing international interest in EES but there isn’t one EES alone that will solve the integration of renewable energy. The techniques for energy storage are existing today and are growing tomorrow.

La France affiche une volonté de développer massivement les énergies renouvelables intermittentes – éolien et photovoltaïque - tout en diminuant la part des sources pilotables, ici le nucléaire. Ce changement de paradigme implique de repenser la gestion des systèmes énergétiques. En effet, l’intermittence des renouvelables génère un besoin de flexibilité à différentes échelles de temps, de la journée à l’année. Ne pouvant plus se reposer sur la flexibilité des moyens pilotables, cette thèse questionne le potentiel d’autres moyens pour y répondre : stockage d’électricité, surdimensionnement de la production et réseaux de chaleur.Face à la nécessité d’une approche système, des modèles simples ont été développés pour affiner la compréhension des interdépendances entre production et stockages. Les indicateurs optimisés sont économiques (€) mais aussi environnementaux : énergie grise et émission de gaz à effet de serre sur l’ensemble du cycle de vie. Les performances des systèmes considérés sont celles d’aujourd’hui et leur développement est limité par les ressources et l’espace disponibles. Sans rentrer dans le détail précis du fonctionnement de chaque technologie, cette approche physique donne les domaines de fonctionnement optimaux des différentes technologies, et les cas difficiles pour lesquels les solutions manquent encore.Dans un premier temps, le besoin en flexibilité généré pourdifférents taux de pénétration de l’intermittence est quantifié pour plusieurs échelles de temps. Cela permet de comparer le potentiel de différentes technologies de stockage d’électricité à chacune de ces échelles pour mettre en phase production et consommation. Les résultats montrent que les temps longs –-- typiquement le stockage saisonnier –-- sont ceux qui demandent les plus gros investissements pour une faible rentabilité. Ensuite, les mécanismes de compétition entre plusieurs stockages et le surdimensionnement sont analysés pour montrer dans quel cas les optimums utilisent des solutions complémentaires. L’étude aborde alors le potentiel du couplage entre le réseau électrique et le réseau de chaleur comme moyen de flexibilité, notamment pour la gestion des besoins longs termes.Ce travail de thèse se focalise à l’échelle Française, bien que la méthodologie soit applicable ailleurs<br>France aims to massively develop intermittent renewable energies --- wind and photovoltaic --- while reducing the share of dispatchable sources, in this case, nuclear power. This paradigm shift implies rethinking the management of energy systems. Indeed, renewables' variable nature generates a need for flexibility on different time-scales, from day to year. As dispatchable means' flexibility can no longer be relied on, this thesis questions the potential of other means to meet this need: electricity storage, oversized production and heating networks.Faced with the need for a systemic approach, we developed simple models to enhance the understanding of the interdependencies between production and storage. The optimized indicators are economic (€), but also environmental: embodied energy and greenhouse gas emissions over the entire life cycle. The performances of the systems considered are those of today and their development is limited by resource and space availability. Without going into the precise details of how each technology works, this physical approach points out optimal operation areas for the different technologies and the difficult cases for which solutions are still lacking.First, the need for flexibility generated for different intermittency penetration rates is quantified for several time scales. It enables us to compare the potential of different electricity storage technologies --- at each of these scales --- to bring production and consumption in phase. The results show that long time-scales --- typically seasonal storage --- require the largest investments for low profitability. The competition mechanisms between several storages and oversizing are then analyzed. It shows how the optimum solutions use complementary flexibility means. The study then addresses the potential of coupling between the electrical grid and the heating grid as a means of flexibility, particularly for the management of long-term needs.This thesis work focuses on the French scale, although the methodology is applicable elsewhere

L'objectif de cette thèse est la gestion et le dimensionnement optimaux d'un Système de Stockage d'Énergie (SSE) couplé à une production d'électricité issue d'Énergies Renouvelables Intermittentes (EnRI). Dans un premier temps, un modèle technico-économique du système SSE-EnRI est développé, associé à trois scénarios types d'injection de puissance au réseau électrique : lissage horaire basé sur la prévision J-1 (S1), puissance garantie (S2) et combiné (S3). Ce modèle est traduit sous la forme d'un programme d'optimisation non linéaire de grande taille. Dans un deuxième temps, les stratégies heuristiques élaborées conduisent à une gestion optimisée - selon les critères de fiabilité, de productivité, d'efficacité et de profitabilité du système - de la production d'énergie avec stockage, appelée “charge adaptative” (CA). Comparée à un modèle linéaire mixte en nombres entiers (MILP), cette gestion optimisée, applicable en conditions opérationnelles, conduit rapidement à des résultats proches de l'optimum. Enfin, la charge adaptative est utilisée dans le dimensionnement optimisé du SSE - pour chacune des trois sources : éolien, houle, solaire (PV). La capacité minimale permettant de respecter le scénario avec un taux de défaillance et des tarifs de revente de l'énergie viables ainsi que les énergies conformes, perdues, manquantes correspondantes sont déterminées. Une analyse de sensibilité est menée montrant l'importance des rendements, de la qualité de prévision ainsi que la forte influence de l'hybridation des sources sur le dimensionnement technico-économique du SSE<br>This thesis aims at presenting an optimal management and sizing of an Energy Storage System (ESS) paired up with Intermittent Renewable Energy Sources (IReN). Firstly, wedeveloped a technico-economic model of the system which is associated with three typical scenarios of utility grid power supply: hourly smoothing based on a one-day-ahead forecast (S1), guaranteed power supply (S2) and combined scenarios (S3). This model takes the form of a large-scale non-linear optimization program. Secondly, four heuristic strategies are assessed and lead to an optimized management of the power output with storage according to the reliability, productivity, efficiency and profitability criteria. This ESS optimized management is called “Adaptive Storage Operation” (ASO). When compared to a mixed integer linear program (MILP), this optimized operation that is practicable under operational conditions gives rapidly near-optimal results. Finally, we use the ASO in ESS optimal sizing for each renewable energy: wind, wave and solar (PV). We determine the minimal sizing that complies with each scenario, by inferring the failure rate, the viable feed-in tariff of the energy, and the corresponding compliant, lost or missing energies. We also perform sensitivity analysis which highlights the importance of the ESS efficiency and of the forecasting accuracy and the strong influence of the hybridization of renewables on ESS technico-economic sizing

Le raccordement des énergies renouvelables (ENR) aux réseaux de distribution peuvent nécessiter des travaux de renforcement coûteux et long à mettre en œuvre. Différentes solutions alternatives peuvent dans certains cas limiter l'ampleur des travaux à réaliser et donc leur montant et/ou leur durée. L’utilisation de telles solutions nécessite au préalable de réviser les méthodes de planification du réseau pour qu’elles puissent analyser leurs impacts technico-économiques. Cette thèse a pour objet d’apporter un cadre adapté à l’étude des leviers d’intégration des ENR à l’aide de nouvelles méthodes pour la planification pluriannuelle des réseaux de distribution. Comparée à l’état de l’art, l’approche adoptée présente l’avantage d’estimer les performances de ces leviers à moyen/long terme en considérant : 1) le comportement du gestionnaire de réseau de distribution, modélisé sous la forme d’une stratégie de planification multi-variables, 2) les interactions entre les réseaux de moyenne et basse tension, et 3) les incertitudes sur l’arrivée des ENR. Ces trois axes d’amélioration ont pu être abordés grâce à des méthodes de maîtrise du temps de calcul appliquées à l’estimation pluriannuelle de l’état électrique du réseau. Le potentiel de l’approche proposée est illustré via l’analyse technico-économique de plusieurs stratégies de planification incluant des leviers traditionnels et/ou des leviers d’effacement de production. Les travaux se concluent sur une première contribution sur l’optimisation des stratégies de planification compte tenu des incertitudes sur l’arrivée des ENR<br>The integration of Renewable Energy Sources (RES) into the distribution networks may require network reinforcements that can be expensive and take time. Different alternative solutions can limit the amount of work to be carried out and thus reduce their cost and/or duration. The use of such solutions requires modifying the network planning methods so as to analyze their techno-economic impacts. This research aims to provide a suitable framework for the study of RES-integration solutions using novel methods for the multi-year planning of distribution networks. Compared to the state of the art, the proposed approach provides the advantage of assessing the performance of these solutions in the medium/long run by considering: 1) the behavior of the distribution system operator, which is modeled as a multi-variable planning strategy, 2) the interactions between medium- and low-voltage networks, and 3) the uncertainties on the arrival of new RES. These three points could have been addressed by applying methods of reducing computation time to the multi-year estimation of the electrical network state. The potential of the proposed approach is illustrated through the techno-economic analysis of several planning strategies including traditional solutions and/or generation curtailment. The research concludes with a first contribution to the planning strategy optimization by taking into account the uncertainties on the arrival of new RES

This thesis presents work on a holistic approach for improving the overall design of solar cooling systems driven by solar thermal collectors. Newly developed methods for thermodynamic optimization of hydraulics and control were used to redesign an existing pilot plant. Measurements taken from the newly developed system show an 81% increase of the Solar Cooling Efficiency (SCEth) factor compared to the original pilot system. In addition to the improvements in system design, new efficiency factors for benchmarking solar cooling systems are presented. The Solar Supply Efficiency (SSEth) factor provides a means of quantifying the quality of solar thermal charging systems relative to the usable heat to drive the sorption process. The product of the SSEth with the already established COPth of the chiller, leads to the SCEth factor which, for the first time, provides a clear and concise benchmarking method for the overall design of solar cooling systems. Furthermore, the definition of a coefficient of performance, including irreversibilities from energy conversion (COPcon), enables a direct comparison of compression and sorption chiller technology. This new performance metric is applicable to all low-temperature heat-supply machines for direct comparison of different types or technologies. The achieved findings of this work led to an optimized generic design for solar cooling systems, which was successfully transferred to the market.

L'intégration massive des énergies renouvelables variables (EnRV) provoque d'importants changements dans le système électrique. Auparavant développé de manière vertical et centralisé, le système était robuste et fiable. Cependant, la production des EnRV est intermittente et peu prévisible. Ainsi, le système doit être plus flexible grâce à de nouvelles options telles que la maîtrise de la demande, le stockage ou l'effacement de la production EnRV. Cependant, le potentiel des EnRV est réparti inégalement en Europe et avec d'importants taux de pénétration d'EnRV, les échanges d'électricité entre les régions vont augmenter provoquant des congestions dans le réseau. Ainsi, les options de flexibilité ne pourront peut-être pas réduire ces congestions. Pour analyser ces effets, le travail mené dans cette thèse utilise le modèle de prospective long terme POLES (Prospective Outlook on Long-term Energy Systems) couplé avec le nouveau module du secteur électrique EUTGRID (EUropean – Transmission Grid Investment and Dispatch). Ce module inclut une représentation détaillée du réseau de transport européen d'électricité avec un calcul des flux plus réaliste. De plus, les renforcements sont déterminés suivant les coûts de congestion de chaque ligne. Ce nouveau couplage permet d'avoir une évolution dynamique du réseau de transport. Le rôle du réseau de transport est ensuite analysé et comparé avec les autres options de flexibilité. Les investissements dans le réseau augmentent ainsi fortement avec d'importants taux de pénétration des EnRV alors que les options de flexibilité ne peuvent pas intégralement remplacer le réseau. Finalement, un travail exploratoire est mené avec l'introduction de réseaux de distribution génériques (urbain, semi-urbain and rural) dans EUTGRID. Les résultats montrent que les renforcements sont légèrement décalés avec une augmentation de l'utilisation des technologies de back-up (i.e. centrales à gaz) ce qui augmente les émissions totales<br>The power system is facing a major shift with the large-scale development of variable renewable energy sources (VRES). This vertical and centralized architecture helped the system to be robust and reliable. However, VRES production is intermittent and less predictable. As a result, the system needs to add more flexibility with new options such as Demand Side Management, storage technologies and VREs curtailment. But renewable energies potentials are unevenly distributed in Europe and, with high shares of VREs, power flows exchanges will increase between specific regions. As a result, the existing transmission grid would face congestions and these flexibility options might not be sufficient to alleviate these bottlenecks. To analyse these impacts, the work carried in this thesis uses the long-term energy model POLES (Prospective Outlook on Long-term Energy Systems) coupled with the new European power sector module EUTGRID (EUropean – Transmission Grid Investment and Dispatch). It includes a detailed transmission grid and more realistic power flows with a DC-OPF. A grid investment mechanism is also incorporated to determine the grid investments based on nodal prices. This new coupling permits to get a dynamic evolution of the transmission grid. The role of the transmission grid is being assessed and compared with other flexibility options. The grid investments increase largely with important development of VRES while other flexibility options cannot completely replace them. Finally, an exploratory work is being carried with the introduction of generic distribution grids (urban, semi-urban and urban) in EUTGRID. The results show that the reinforcements are slightly delayed with a greater use of back-up technologies which increases the total emissions

Electric power systems continue to increase in complexity because of the deployment of market mechanisms, the integration of renewable generation and distributed energy resources (DER) (e.g., wind and solar), the penetration of electric vehicles and other price sensitive loads. These revolutionary changes and the consequent increase in uncertainty and dynamicity call for significant modifications to power system operation models including unit commitment (UC), economic load dispatch (ELD) and optimal power flow (OPF). Planning and operation of these ???smart??? electric grids are expected to be impacted significantly, because of the intermittent nature of various supply and demand resources that have penetrated into the system with the recent advances. The main focus of this thesis is on the application of the Affine Arithmetic (AA) method to power system operational problems. The AA method is a very efficient and accurate tool to incorporate uncertainties, as it takes into account all the information amongst dependent variables, by considering their correlations, and hence provides less conservative bounds compared to the Interval Arithmetic (IA) method. Moreover, the AA method does not require assumptions to approximate the probability distribution function (pdf) of random variables. In order to take advantage of the AA method in power flow analysis problems, first a novel formulation of the power flow problem within an optimization framework that includes complementarity constraints is proposed. The power flow problem is formulated as a mixed complementarity problem (MCP), which can take advantage of robust and efficient state-of-the-art nonlinear programming (NLP) and complementarity problems solvers. Based on the proposed MCP formulation, it is formally demonstrated that the Newton-Raphson (NR) solution of the power flow problem is essentially a step of the traditional General Reduced Gradient (GRG) algorithm. The solution of the proposed MCP model is compared with the commonly used NR method using a variety of small-, medium-, and large-sized systems in order to examine the flexibility and robustness of this approach. The MCP-based approach is then used in a power flow problem under uncertainties, in order to obtain the operational ranges for the variables based on the AA method considering active and reactive power demand uncertainties. The proposed approach does not rely on the pdf of the uncertain variables and is therefore shown to be more efficient than the traditional solution methodologies, such as Monte Carlo Simulation (MCS). Also, because of the characteristics of the MCP-based method, the resulting bounds take into consideration the limits of real and reactive power generation. The thesis furthermore proposes a novel AA-based method to solve the OPF problem with uncertain generation sources and hence determine the operating margins of the thermal generators in systems under these conditions. In the AA-based OPF problem, all the state and control variables are treated in affine form, comprising a center value and the corresponding noise magnitudes, to represent forecast, model error, and other sources of uncertainty without the need to assume a pdf. The AA-based approach is benchmarked against the MCS-based intervals, and is shown to obtain bounds close to the ones obtained using the MCS method, although they are slightly more conservative. Furthermore, the proposed algorithm to solve the AA-based OPF problem is shown to be efficient as it does not need the pdf approximations of the random variables and does not rely on iterations to converge to a solution. The applicability of the suggested approach is tested on a large real European power system.

Different battery storage technologies are considered as important flexibility option in the face of increasing shares of renewables in the grid. A challenge is to support decision-making by providing a broader perspective on battery technology development, choice, and implementation. The tailored approach in the frame of Constructive Technology Assessment (CTA) in combination with system analysis allows it to explore actor visions and expectations about battery storage and to use this information to provide quantitative information about the consequences of these. Research results combine the perspectives of technology and non-technology related actors (enactors and selectors) to create new and broader knowledge to provide “better” technology. Major implications identified for battery storage are missing business models, uncertain regulations, and doubts about their techno-economic viability. A highlight is a proof that expectations about technology characteristics in orientation to sustainability criteria are settled within concentric perspectives by using the Analytic-Hierarchy-Process (AHP). Enactors focus on economic and technological criteria which reflect the concentric bias of this group. In contrast, selectors perceive environmental and social criteria as more important. The consensus among actors regarding criteria importance is not existent to moderate which indicates that more research is required here. System analysis is used to quantify actor preferences obtained through the AHP. Li-Ion-batteries (LIB), lead-acid-batteries (VRLA), high-temperature-batteries (NaNiCl and NaS), and Vanadium-redox-flowbatteries (VRFB) are evaluated through e.g. life cycle assessment and costing for four different application fields (decentralized storage, wind energy support, primary regulation and energy-time-shift (ETS-includes compressed-air-energy-storage (CAES) and pumped-hydro-storage (PHS)). Preliminary rankings indicate that most LIBs can be recommended for all application areas, wherein decentralized storage is considered to offer the highest potentials for battery storage. VRLA and NaS achieve rather low scores whereas ranking of VRFB is highly dependent on the considered use case. PHS and CAES dominate all assessed energy storage technologies in the ETS application case.

Dissertação de Mestrado Integrado em Engenharia Electrotécnica e de Computadores apresentada à Faculdade de Ciências e Tecnologia<br>A integração de fontes renováveis no sector elétrico é uma realidade na maioria dos países europeus. O tema assume uma grande importância no sentido em que permite o aproveitamento dos próprios recursos energéticos, diminuindo a necessidade de matérias primas importadas, cuja utilização é responsável por problemas ambientais. No entanto, a intermitência das fontes renováveis obriga a um planeamento da sua implementação, de forma a avaliar o seu potencial, mas também as alternativas para os períodos de geração mais reduzida. A presente dissertação de Mestrado Integrado em Engenharia Eletrotécnica e de Computadores, na área de especialização de Energia, tem como objetivo o estudo do planeamento de Sistemas de Energia Elétrica 100% renováveis. Para tal, foi realizada uma simulação fiel do Sistema Elétrico de Portugal Continental no ano de 2016. Tal serviu de base para a elaboração de cenários futuros, até ao ano de 2040, tendo em conta previsões relacionadas com o aumento da produção de origem renovável e da diminuição da produção proveniente de combustíveis fósseis. Os cenários elaborados tiveram em conta as características específicas do Sistema Elétrico Português, tanto no que diz respeito à aposta em tecnologias renováveis especificas e vistas com maior potencial de desenvolvimento, mas também às limitações impostas pelas condições geográficas do país e pela inviabilidade do investimento em outras tecnologias que já estão a atingir o seu potencial máximo aproveitável. A ferramenta utilizada durante o desenvolvimento deste trabalho foi o EnergyPLAN, um software de simulação de sistemas de energia que assegura a sua avaliação com base na distribuição do consumo e da disponibilidade das fontes renováveis intermitentes, permitindo avaliar com detalhe as evoluções dos sistemas simulados. O trabalho visa sobretudo uma análise técnica a longo prazo com base nos problemas que resultam da intermitência das fontes renováveis consideradas, que originam períodos de escassa geração e outros de geração em excesso, e na forma como o Sistema Elétrico será capaz de lidar com os mesmos para a garantir a sua fiabilidade. É avaliada a possibilidade da operação de um Sistema Elétrico 100% renovável recorrendo a soluções de armazenamento de energia, nomeadamente a baterias de iões de lítio, de forma a assegurar a fiabilidade do sistema. Concluiu-se que tal é tecnicamente possível, mas que não é economicamente viável.<br>The integration of renewable energy sources in the electricity sector is a reality in most European countries. The subject becomes very important since it allows the use of internal energy resources, reducing the need of imported fuels that are responsible for environmental problems. However, the intermittence of renewable energy sources requires the planning of its implementation in order to evaluate its potential, as well as alternatives for periods with low generation levels. This Master thesis in Electrical and Computer Engineering in the specialization of Energy aims to study the planning of 100% renewable energy systems. For this purpose, a simulation for the mainland Portuguese electricity system in 2016 was developed. Such simulation was used as starting point for the development of future scenarios, until 2040, considering forecasts related with the increase of renewable energy generation and decrease of fossil fuels based generation. The developed scenarios take into consideration the specific characteristics of the Portuguese Electric System, considering not only the focus on specific renewable technologies with larger potential for development, but also the limitations imposed by the geographical conditions of the country and the inviability of the investment in technologies already reaching its maximum usable potential. The tool used during the development of this work was EnergyPLAN, a software for the simulation of energy systems that ensures its assessment based on the distribution of the consumption and the availability of the intermittent renewable sources, allowing to observe in detail the evolutions of the simulated systems. The work mainly aims to present a long-term technical analysis based on the problems created by the intermittency of the considered renewable generation sources, that result in periods with lack or surplus generation, and in the way how the Electrical System will be able to deal with such problems to ensure its reliability. The possibility of operating a 100% Renewable Electric system is evaluated using energy storage solutions, in particular lithium ion batteries. It was concluded that such option is technically possible, but not cost-effective.

In this paper, overcapacity of wind energy is analyzed using panel data techniques for a set of 19 European countries for the span of time 1998-2009. We control for the effect of conventional energy sources, namely coal-based and gas-fired power plants. These energy sources are mainly used to backup electricity generation in windless periods and in peak-load times. The effect of other renewable energy sources is also assessed. Results suggest that wind power growth rate and population density raises overcapacity. We also test the total of energy measures taken in Europe under long term energy goals. We extend the debate of renewables intermittency, highlighting the overcapacity issue and suggesting possible solutions to smooth out this problem.<br>Neste estudo, o excesso de capacidade instalada de energia eólica é analisado através de técnicas de dados em painel para um conjunto de 19 países Europeus entre os anos 1998 e 2009. Controlamos para o efeito das fontes convencionais de produção de energia eléctrica, nomeadamente o carvão e gás que são utilizados para backup na produção de electricidade quando o vento não é suficiente e a procura tem de ser satisfeita. Controlamos também para o efeito das energias renováveis. Os resultados sugerem que o crescimento de instalação de energia eólica e a densidade populacional contribuem para o aumento do excesso de capacidade de energia eólica. Por outro lado é também medido o efeito do total de políticas energéticas tomadas a nível europeu no âmbito de objectivos energéticos a longo prazo. Contribuímos para o debate sobre a intermitência das renováveis, dando luz sobre este tema e sugerindo possíveis soluções para lidar com o consequente problema do excesso de capacidade.

Dissertação de Mestrado Integrado em Engenharia Electrotécnica e de Computadores apresentada à Faculdade de Ciências e Tecnologia<br>Renewable energies are the obvious option to ensure a sustainable future. The wide availability and diversity of natural energy resources allows the development of flexible generation technologies adapted to the needs of electric power systems. In Portugal, the potential of wind, solar and hydro power enable an energy future mainly based on renewable energy. However, changing from predictable and easily controllable fossil energy systems, to systems that use natural energy sources has a strong impact on the generated energy profile. Inconstant levels of generation, difficulties to match the consumption levels, and difficulty in ensuring a correct management of the systems are only some of the problems inherent to this type of renewable intermittent energy. Among the different solutions that reduce these problems, the use of an operating reserve by large-scale storage systems produce the best results. By storing excess energy and discharging when necessary, these grid-connected systems can smooth the load diagrams, reduce imported energy values, and avoid the use of environmentally harmful energy sources. Following an analysis of the technical specifications of the currently known systems, were chosen the 4 most suitable systems for use with intermittent power generation were selected. The systems selected were compress air energy storage (CAES), conventional lithium ion batteries (Li-ion), sodium-sulfur (NaS) batteries and Vanadium redox (VRB) flow batteries.In this dissertation, an algorithm was created in Matlab® able to simulate the impact caused by each of the storage system on the load diagrams of the preselected case studies. After obtaining the results using the algorithm, a technical and economic analysis of the energy exchanges and energy costs for each of the systems was done. At the end, an analysis of the systems that provide energy at a lower cost and with greater efficiency to solve problems related to intermittent power generation is done.<br>As energias renováveis são a melhor opção para garantir um futuro sustentável. A grande disponibilidade e diversidade de fontes de energias naturais levou ao desenvolvimento de tecnologias de geração flexíveis adaptadas às necessidades dos sistemas de energia elétrica. Em Portugal, o potencial da energia eólica, solar e hídrica permitem um futuro energético maioritariamente baseado em energias renováveis.No entanto, a mudança de sistemas de geração fóssil previsível e facilmente controlável para sistemas de geração dependentes de fontes de energia naturais variáveis tem um forte impacto no perfil da energia gerada. Níveis de geração inconstantes, incapacidade de garantir os níveis de energia consumida, e dificuldade em realizar uma correta gestão dos sistemas são apenas alguns dos problemas inerentes a este tipo de energia renovável intermitente. De entre as diferentes soluções existentes que permitem atenuar os problemas referidos, a utilização de reserva operacional baseada em sistemas de armazenamento de larga escala é a que apresenta melhores resultados. Armazenando energia em excesso e descarregando quando necessário, estes sistemas interligados com a rede elétrica permitem suavizar os diagramas de carga, reduzir os valores de energia importada e evitar a utilização de fontes de energia nocivas para o ambiente. Após uma análise das especificações técnicas dos sistemas atualmente conhecidos, foram selecionados os 4 sistemas mais adequados para a utilização com geração de energia intermitente, nomeadamente sistemas de armazenamento de comprimido, de baterias convencionais de iões de lítio, de baterias de sódio-enxofre e de baterias de fluxo de redox de vanádio.Para esta dissertação foi criado um algoritmo em Matlab® capaz de simular as variações causadas por cada um do sistema de armazenamento nos diagramas de carga de casos de estudo selecionados. Após obtenção dos resultados através do algoritmo, foi realizada uma análise técnica e económica das trocas de energia e dos custos de energia de cada um dos sistemas com a rede ao longo de um ano. No final foram apresentados quais os sistemas que fornecem energia a um custo mais reduzido e mais adequados para a resolução dos problemas relacionados com a geração de energia intermitência.

Dissertação de Mestrado Integrado em Engenharia Electrotécnica e de Computadores apresentada à Faculdade de Ciências e Tecnologia<br>Nos dias que correm o tema, energias renováveis, é um assunto cada vez mais abordado na comunidade científica devido a avanços tecnológicos e aos possíveis benefícios que a integração destas na rede acarretam para todo o mundo, principalmente para o ambiente. Estas surgem como uma possível solução para as fontes de energia não renováveis, de carácter finito à escala humana e extremamente poluentes, como é o caso das centrais a carvão. Neste enquadramento, e devido à elevada aposta de Portugal em energia eólica, surgiu como tema da dissertação estudar o impacto que a variabilidade do vento trás para as produções de energia, e ainda como é que a intermitência eólica pode ser combatida de forma a minimizar problemas para o Sistema Elétrico Nacional (SEN). Numa primeira fase foi abordado o estado das energias renováveis na Europa, mais especificamente da eólica, seu surgimento e evolução das tecnologias existentes, quais os problemas associados à sua integração e ainda métodos de compensação das curvas típicas de produção eólica. Numa segunda fase foi abordado o caso de estudo, isto é, a composição do SEN, qual o estado de integração de energia eólica em Portugal, inclusive a distribuição dos parques eólicos no continente e ilhas, e tarifas energéticas associadas. Por fim, recorrendo a dados de produção eólica fornecidos pela Redes Energéticas Nacionais foram desenvolvidos diversos indicadores de forma a facilitar uma melhor compreensão de como a variabilidade do vento afeta as produções eólicas a curto, médio e longo prazo, quais as suas implicações para as satisfações de carga e por último como estas variações podem ser combatidas recorrendo ao uso de energia solar como fonte complementar, bem como outros métodos de previsão.<br>Nowadays the theme, renewable energies, is a subject increasingly addressed in the scientific community due to technological advances and the possible benefits that the integration of these in the network bring for the world, mainly for the environment. These appear as a possible solution for non-renewable energy sources, which are finite on a human scale and extremely polluting, such as coal-fired power plants. In this context, and due to Portugal's high investment in wind energy, the theme of the dissertation was to study the impact that wind variability brings to energy production, and also how wind intermittency can be combated in order to minimize problems for the National Electrical System (SEN). In a first phase, was presented the state of renewable energies in Europe, more specifically of wind power, its emergence and evolution of existing technologies, which are the problems associated with its integration and also methods of compensating typical wind production curves. In a second phase, the study case was approached, that is, the composition of the SEN, the state of integration of wind energy in Portugal, including the distribution of wind farms in the continent and islands and associated energy fares. Finally, using wind production data provided by Redes Energéticas Nacionais, several indicators were developed in order to facilitate a better understanding of how wind variability affects wind production in the short, medium and long term, what are its implications for load demand response and finally how these variations can be combated by using solar energy as a complementary source, as well as better forecasting methods.

Dissertação de Mestrado Integrado em Engenharia Electrotécnica e de Computadores apresentada à Faculdade de Ciências e Tecnologia<br>A transição energética dos combustíveis fósseis para as energias renováveis é o grande desafio do século XXI e a energia solar fotovoltaica assume um papel fundamental para a garantir. Os avanços tecnológicos estão a permitir tornar cada vez mais rentável a energia solar fotovoltaica, pelo que é expectável um crescimento significativo da sua potencia instalada a nível mundial. Portugal é dos países com maior índice de radiação solar da União Europeia, e apesar da baixa capacidade instalada atual, prevê-se que o fotovoltaico será a fonte com maior crescimento nos próximos anos, podendo no futuro ser a principal fonte de energia do país. Posto isto, a avaliação dos impactos que a penetração da energia solar fotovoltaica em larga escala tem na gestão do sistema electroprodutor torna-se fundamental.A presente dissertação tem por objetivo compreender qual o impacto que o crescimento da energia solar fotovoltaica terá na gestão dos sistemas de energia elétrica e avaliar tecnologias capazes de mitigar a sua variabilidade, nomeadamente tecnologias de armazenamento de energia ou de gestão da procura. Os sistemas de armazenamento permitem assegurar reserva operacional, armazenando o excesso de energia das horas de maior produção e menor procura e descarregar nas horas de ponta dos diagramas de carga. A gestão da procura complementa esta tecnologia reduzindo a necessidade de investimento em baterias de maior capacidade. Analisaram-se cenários futuros com base nas previsões de crescimento da potência instalada do fotovoltaico em Portugal para 2021 (1,6 GW) e 2030 (6 GW), estudou-se os impactos e analisaram-se possíveis soluções. Para o dia referente à primavera o aumento da potência para 6 GW permitiu reduzir em 6,65 GWh a geração a gás natural e evitar a importação de 1,3 GWh. A introdução de uma bateria com capacidade de 1,866 GWh permitiu reduzir em 1317 MWh a importação e em 2952 MWh o excesso de renováveis face ao consumo, correspondendo a 14,78% do referido excesso.Em suma pode-se afirmar que o crescimento da energia solar fotovoltaica e a intermitência da mesma exigem um sistema electroprodutor flexível. Nesse contexto, os sistemas de armazenamento e a gestão da procura são fundamentais para garantir a flexibilidade, mantendo o sistema de energia elétrica em equilíbrio.<br>The energy transition from fossil fuels to renewable energies is the great challenge of the 21st century and solar photovoltaics plays a key role in it. The technological advances are making solar photovoltaics more profitable, therefore a significant increase in the worldwide installed power is expected. Portugal is one of the countries with the highest solar radiation index in the European Union, despite the current low installed capacity. However, photovoltaic is expected to be the fastest growing source in the coming years and can be the country's main source of energy in the future. Therefore, the assessment of the impacts of the large-scale penetration of photovoltaic power on power generation systems and its management becomes indispensable.The aim of this dissertation is to understand the impact of the growth of photovoltaic power in the management of electrical systems and to evaluate technologies capable of mitigating their variability, namely energy storage or demand-side management technologies. Storage systems can ensure operational reserve, storing the energy surplus in hours of higher generation and lower demand and discharge at periods of high demand. Demand-side management complements this technology by reducing the need for investment in batteries with large capacity.Future scenarios were analyzed based on forecasts for the growth of the installed photovoltaic power in Portugal for 2021 (1.6 GW) and 2030 (6 GW), being studied the impacts and analyzed possible solutions. For the spring day, the increase in power to 6 GW allowed to reduce natural gas generation by 6.65 GWh and to avoid the import of 1.3 GWh. The introduction of a battery with a capacity of 1,866 GWh enabled the reduction of imports by 1317 MWh and the renewable generation surplus of renewables relatively to the consumption by 2952 MWh, corresponding to 14.78% of such surplus.It can be concluded that the growth of photovoltaic power and its intermittence will require a flexible power generation system. In this context, storage systems and demand-side management are critical to ensuring flexibility by keeping the power system in balance.