38 research outputs found
The value of hydrological information in multireservoir systems operation
La gestion optimale dâun systĂšme hydroĂ©lectrique composĂ© de plusieurs rĂ©servoirs est un problĂšme multi-Ă©tapes complexe de prise de dĂ©cision impliquant, entre autres, (i) un compromis entre les consĂ©quences immĂ©diates et futures dâune dĂ©cision, (ii) des risques et des incertitudes importantes, et (iii) de multiple objectifs et contraintes opĂ©rationnelles. Elle est souvent formulĂ©e comme un problĂšme dâoptimisation, mais il nâexiste pas, Ă ce jour, de technique de rĂ©fĂ©rence mĂȘme si la programmation dynamique (DP) a Ă©tĂ© souvent utilisĂ©e. La formulation stochastique de DP (SDP) permet la prise en compte explicite de lâincertitude entourant les apports hydrologiques futurs. DiffĂ©rentes approches ont Ă©tĂ© dĂ©veloppĂ©es pour incorporer des informations hydrologiques et climatiques autres que les apports. Ces Ă©tudes ont rĂ©vĂ©lĂ© un potentiel dâamĂ©lioration des politiques de gestion proposĂ©es par les formulations SDP. Cependant, ces formulations sont applicables aux systĂšmes de petites tailles en raison de la cĂ©lĂšbre « malĂ©diction de la dimensionnalitĂ© ». La programmation dynamique stochastique duale (SDDP) est une extension de SDP dĂ©veloppĂ©e dans les annĂ©es 90. Elle est lâune des rares solutions algorithmiques utilisĂ©es pour dĂ©terminer les politiques de gestion des systĂšmes hydroĂ©lectriques de grande taille. Dans SDDP, lâincertitude hydrologique est capturĂ©e Ă lâaide dâun modĂšle autorĂ©gressif avec corrĂ©lation spatiale des rĂ©sidus. Ce modĂšle analytique permet dâobtenir certains des paramĂštres nĂ©cessaires Ă lâimplĂ©mentation de la technique dâoptimisation. En pratique, les apports hydrologiques peuvent ĂȘtre influencĂ©s par dâautres variables observables, telles que lâĂ©quivalent de neige en eau et / ou la tempĂ©rature de la surface des ocĂ©ans. La prise en compte de ces variables, appelĂ©es variables exogĂšnes, permet de mieux dĂ©crire les processus hydrologiques et donc dâamĂ©liorer les politiques de gestion des rĂ©servoirs. Lâobjectif principal de ce doctorat est dâĂ©valuer la valeur Ă©conomique des politiques de gestion proposĂ©es par SDDP et ce pour diverses informations hydro-climatiques. En partant dâun modĂšle SDDP dans lequel la modĂ©lisation hydrologique est limitĂ©e aux processus Makoviens, la premiĂšre activitĂ© de recherche a consistĂ© Ă augmenter lâordre du modĂšle autorĂ©gressif et Ă adapter la formulation SDDP. La seconde activitĂ© fut dĂ©diĂ©e Ă lâincorporation de diffĂ©rentes variables hydrologiques exogĂšnes dans lâalgorithme SDDP. Le systĂšme hydroĂ©lectrique de Rio Tinto (RT) situĂ© dans le bassin du fleuve Saguenay-Lac-Saint-Jean fut utilisĂ© comme cas dâĂ©tude. Ătant donnĂ© que ce systĂšme nâest pas capable de produire la totalitĂ© de lâĂ©nergie demandĂ©e par les fonderies pour assurer pleinement la production dâaluminium, le modĂšle SDDP a Ă©tĂ© modifiĂ© de maniĂšre Ă considĂ©rer les dĂ©cisions de gestion des contrats avec Hydro QuĂ©bec. Le rĂ©sultat final est un systĂšme dâaide Ă la dĂ©cision pour la gestion dâun large portefeuille dâactifs physiques et financiers en utilisant diverses informations hydro-climatiques. Les rĂ©sultats globaux rĂ©vĂšlent les gains de production dâĂ©nergie auxquels les opĂ©rateurs peuvent sâattendre lorsque dâautres variables hydrologiques sont incluses dans le vecteur des variables dâĂ©tat de SDDP.The optimal operation of a multireservoir hydroelectric system is a complex, multistage, stochastic decision-making problem involving, among others, (i) a trade-off between immediate and future consequences of a decision, (ii) considerable risks and uncertainties, and (iii) multiple objectives and operational constraints. The reservoir operation problem is often formulated as an optimization problem but not a single optimization approach/algorithm exists. Dynamic programming (DP) has been the most popular optimization technique applied to solve the optimization problem. The stochastic formulation of DP (SDP) can be performed by explicitly considering streamflow uncertainty in the DP recursive equation. Different approaches to incorporate more hydrologic and climatic information have been developed and have revealed the potential to enhance SDP- derived policies. However, all these techniques are limited to small-scale systems due to the so-called curse of dimensionality. Stochastic Dual Dynamic Programming (SDDP), an extension of the traditional SDP developed in the 90ies, is one of the few algorithmic solutions used to determine the operating policies of large-scale hydropower systems. In SDDP the hydrologic uncertainty is captured through a multi-site periodic autoregressive model. This analytical linear model is required to derive some of the parameters needed to implement the optimization technique. In practice, reservoir inflows can be affected by other observable variables, such snow water equivalent and/or sea surface temperature. These variables, called exogenous variables, can better describe the hydrologic processes, and therefore enhance reservoir operating policies. The main objective of this PhD is to assess the economic value of SDDP-derived operating policies in large-scale water systems using various hydro-climatic information. The first task focuses on the incorporation of the multi-lag autocorrelation of the hydrologic variables in the SDDP algorithm. Afterwards, the second task is devoted to the incorporation of different exogenous hydrologic variables. The hydroelectric system of Rio Tinto (RT) located in the Saguenay-Lac-Saint-Jean River Basin is used as case study. Since, RTâs hydropower system is not able to produce the entire amount of energy demanded at the smelters to fully assure the aluminum production, a portfolio of energy contacts with Hydro-QuĂ©bec is available. Eventually, we end up with a decision support system for the management of a large portfolio of physical and financial assets using various hydro-climatic information. The overall results reveal the extent of the gains in energy production that the operators can expect as more hydrologic variables are included in the state-space vector
Um modelo de otimização estocåstica com representação individualizada das usinas hidrelétricas no planejamento de médio prazo da operação hidrotérmica
Tese (doutorado) - Universidade Federal de Santa Catarina, Centro TecnolĂłgico, Programa de PĂłs-Graduação em Engenharia ElĂ©trica, FlorianĂłpolis, 2016.O problema do Planejamento de MĂ©dio Prazo da Operação hidrotĂ©rmica (PMPO) possui papel fundamental na coordenação dos sistemas elĂ©tricos que dependem fortemente de eletricidade proveniente de fontes hĂdricas. O objetivo do PMPO Ă© definir uma polĂtica de operação Ăłtima que minimiza o custo de operação para o atendimento da demanda por energia em um horizonte de mĂ©dio prazo. Nesse contexto, o mĂ©todo da Programação DinĂąmica Dual EstocĂĄstica (PDDE) Ă© amplamente utilizado para o cĂĄlculo de polĂticas de operação na solução do problema do PMPO. AlĂ©m disso, destaca-se que para a incorporação das incertezas associadas Ă s afluĂȘncias, um modelo linear multiestĂĄgio estocĂĄstico Ă© atribuĂdo ao PMPO. No caso brasileiro, algumas simplificaçÔes sĂŁo adotadas na representação das decisĂ”es hidrelĂ©tricas com o objetivo de se reduzir o esforço computacional. A principal simplificação adotada Ă© a modelagem de ReservatĂłrios Equivalentes de Energia (REE) na representação de um conjunto de decisĂ”es hidrelĂ©tricas mensais. Neste trabalho, as decisĂ”es de cada hidrelĂ©trica do sistema sĂŁo modeladas individualmente, de modo que a abordagem por REEs Ă© completamente sobrepujada. Assim, o desempenho do cĂĄlculo da polĂtica de operação na PDDE Ă© diretamente afetado pela elevada dimensĂŁo do modelo individualizado do PMPO. Logo, o principal objetivo deste trabalho consiste em calcular polĂticas de operação de boa qualidade para o modelo individualizado estocĂĄstico do PMPO, em um tempo razoĂĄvel de execução da PDDE. Para que esse objetivo seja alcançado, algumas melhorias em termos da modelagem do PMPO e do algoritmo da PDDE sĂŁo propostas. Os resultados acerca das melhorias propostas sĂŁo apresentados, de modo que o sistema hidrotĂ©rmico brasileiro Ă© considerado nos experimentos computacionais. A partir dos resultados obtidos, podem-se observar vantagens considerĂĄveis na modelagem individual das decisĂ”es hidrelĂ©tricas no PMPO, em relação Ă utilização de REEs, para um tempo razoĂĄvel de execução da PDDE.Abstract : The Long-Term Hydrothermal Scheduling (LTHS) problem plays an important role in power systems that rely heavily on hydroelectricity. The purpose of the LTHS problem is to define an optimal operation policy that minimizes the operation costs to meet demand over a long horizon. A popular solution approach to this problem is called Stochastic Dual Dynamic Programming (SDDP). To incorporate the inflow uncertainties, the LTHS problem is modeled as a multi-stage linear stochastic problem. In the Brazilian LTHS problem, some simplifications are made in the hydro power plants representation in order to reduce the computational burden. The main simplification is the Equivalent Energy Reservoir (EER) modeling that replaces set of hydro plants monthly decisions. In this work, the EERs approach is overcame and individual decisions for each hydro plant in the hydrothermal system are modeled. As a result, the operation policy computation in SDDP is directly affected by the dimension of the LTHS stochastic framework with individual hydro plant decisions. Consequently, the goal of this work is to achieve reasonable operation polices for the individualized LTHS stochastic modeling in an acceptable and practicable computational time. To accomplish this objective, improvements in the LTHS modeling and SDDP algorithm design are proposed. The results regarding theses aspects are presented, which the Brazilian hydrothermal power system are considered. The results show advantages in individual hydro plant decisions modeling, in relation to EERs, for practical computational time assumptions in SDDP execution
Pathways to Water Sector Decarbonization, Carbon Capture and Utilization
The water sector is in the middle of a paradigm shift from focusing on treatment and meeting discharge permit limits to integrated operation that also enables a circular water economy via water reuse, resource recovery, and system level planning and operation. While the sector has gone through different stages of such revolution, from improving energy efficiency to recovering renewable energy and resources, when it comes to the next step of achieving carbon neutrality or negative emission, it falls behind other infrastructure sectors such as energy and transportation. The water sector carries tremendous potential to decarbonize, from technological advancements, to operational optimization, to policy and behavioural changes. This book aims to fill an important gap for different stakeholders to gain knowledge and skills in this area and equip the water community to further decarbonize the industry and build a carbon-free society and economy. The book goes beyond technology overviews, rather it aims to provide a system level blueprint for decarbonization. It can be a reference book and textbook for graduate students, researchers, practitioners, consultants and policy makers, and it will provide practical guidance for stakeholders to analyse and implement decarbonization measures in their professions
Pathways to Water Sector Decarbonization, Carbon Capture and Utilization
The water sector is in the middle of a paradigm shift from focusing on treatment and meeting discharge permit limits to integrated operation that also enables a circular water economy via water reuse, resource recovery, and system level planning and operation. While the sector has gone through different stages of such revolution, from improving energy efficiency to recovering renewable energy and resources, when it comes to the next step of achieving carbon neutrality or negative emission, it falls behind other infrastructure sectors such as energy and transportation. The water sector carries tremendous potential to decarbonize, from technological advancements, to operational optimization, to policy and behavioural changes.
This book aims to fill an important gap for different stakeholders to gain knowledge and skills in this area and equip the water community to further decarbonize the industry and build a carbon-free society and economy. The book goes beyond technology overviews, rather it aims to provide a system level blueprint for decarbonization. It can be a reference book and textbook for graduate students, researchers, practitioners, consultants and policy makers, and it will provide practical guidance for stakeholders to analyse and implement decarbonization measures in their professions
Integration of Renewables in Power Systems by Multi-Energy System Interaction
This book focuses on the interaction between different energy vectors, that is, between electrical, thermal, gas, and transportation systems, with the purpose of optimizing the planning and operation of future energy systems. More and more renewable energy is integrated into the electrical system, and to optimize its usage and ensure that its full production can be hosted and utilized, the power system has to be controlled in a more flexible manner. In order not to overload the electrical distribution grids, the new large loads have to be controlled using demand response, perchance through a hierarchical control set-up where some controls are dependent on price signals from the spot and balancing markets. In addition, by performing local real-time control and coordination based on local voltage or system frequency measurements, the grid hosting limits are not violated
Pathways to Water Sector Decarbonization, Carbon Capture and Utilization
The water sector is in the middle of a paradigm shift from focusing on treatment and meeting discharge permit limits to integrated operation that also enables a circular water economy via water reuse, resource recovery, and system level planning and operation. While the sector has gone through different stages of such revolution, from improving energy efficiency to recovering renewable energy and resources, when it comes to the next step of achieving carbon neutrality or negative emission, it falls behind other infrastructure sectors such as energy and transportation. The water sector carries tremendous potential to decarbonize, from technological advancements, to operational optimization, to policy and behavioural changes.
This book aims to fill an important gap for different stakeholders to gain knowledge and skills in this area and equip the water community to further decarbonize the industry and build a carbon-free society and economy. The book goes beyond technology overviews, rather it aims to provide a system level blueprint for decarbonization. It can be a reference book and textbook for graduate students, researchers, practitioners, consultants and policy makers, and it will provide practical guidance for stakeholders to analyse and implement decarbonization measures in their professions
Pathways to Water Sector Decarbonization, Carbon Capture and Utilization
The water sector is in the middle of a paradigm shift from focusing on treatment and meeting discharge permit limits to integrated operation that also enables a circular water economy via water reuse, resource recovery, and system level planning and operation. While the sector has gone through different stages of such revolution, from improving energy efficiency to recovering renewable energy and resources, when it comes to the next step of achieving carbon neutrality or negative emission, it falls behind other infrastructure sectors such as energy and transportation. The water sector carries tremendous potential to decarbonize, from technological advancements, to operational optimization, to policy and behavioural changes. This book aims to fill an important gap for different stakeholders to gain knowledge and skills in this area and equip the water community to further decarbonize the industry and build a carbon-free society and economy. The book goes beyond technology overviews, rather it aims to provide a system level blueprint for decarbonization. It can be a reference book and textbook for graduate students, researchers, practitioners, consultants and policy makers, and it will provide practical guidance for stakeholders to analyse and implement decarbonization measures in their professions
Green Technologies for Production Processes
This book focuses on original research works about Green Technologies for Production Processes, including discrete production processes and process production processes, from various aspects that tackle product, process, and system issues in production. The aim is to report the state-of-the-art on relevant research topics and highlight the barriers, challenges, and opportunities we are facing. This book includes 22 research papers and involves energy-saving and waste reduction in production processes, design and manufacturing of green products, low carbon manufacturing and remanufacturing, management and policy for sustainable production, technologies of mitigating CO2 emissions, and other green technologies
Volume variation in a thermochemical material- An experimental study
The research focuses on swelling and shrinkage during cycling of a thermochemical material. Potassium carbonate has been cycled and the change in size has been monitored over subsequent cycles with the help of in-situ measurement in the micro-climate chamber. The experiments have been performed for different operating conditions and the resultant images were processed to calculate the equivalent diameter of the salt grains. Micro -CT scans were performed for both the samples to compare the two-dimensional results from in-situ experiments to a complete three-dimensional analysis