Dissertations / Theses on the topic 'Energy balancing'
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Patharlapati, Sai Ram Charan. "Balancing of Network Energy using Observer Approach." Master's thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-209453.
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Efficient energy use is primarily for any sensor networks to function for a longer time period. There have been many efficient schemes with various progress levels proposed by many researchers. Yet, there still more improvements are needed. This thesis is an attempt to make wireless sensor networks with further efficient on energy usage in the network with respect to rate of delivery of the messages.
In sensor network architecture radio, sensing and actuators have influence over the power consumption in the entire network. While listening as well as transmitting, energy is consumed by the radio. However, if by reducing listening times or by reducing the number of messages transmitting would reduce the energy consumption. But, in real time scenario with critical information sensing network leads to information loss. To overcome this an adaptive routing technique should be considered. So, that it focuses on saving energy in a much more sophisticated way without reducing the performance of the sensing network transmitting and receiving functionalities.
This thesis tackles on parts of the energy efficiency problem in a wireless sensor network and improving delivery rate of messages. To achieve this a routing technique is proposed. In this method, switching between two routing paths are considered and the switching decision taken by the server based on messages delivered comparative previous time intervals. The goal is to get maximum network life time without degrading the number of messages at the server. In this work some conventional routing methods are considered for implementing an approach. This approach is by implementing a shortest path, Gradient based energy routing algorithm and an observer component to control switching between paths. Further, controlled switching done by observer compared to normal initial switch rule. Evaluations are done in a simulation environment and results show improvement in network lifetime in a much more balanced way.
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Sudhakar, Soumya. "Balancing actuation energy and computing energy in low-power motion planning." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127096.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 89-91).
Inspired by emerging low-power robotic vehicles, we identify a new class of motion planning problems in which the energy consumed by the computer while planning a path can be as large as the energy consumed by the actuators during the execution of the path. As a result, minimizing energy requires minimizing both actuation energy and computing energy since computing energy is no longer negligible. We propose the first algorithm to address this new class of motion planning problems, called Computing Energy Included Motion Planning (CEIMP). CEIMP operates similarly to other anytime planning algorithms, except it stops when it estimates that while further computing may save actuation energy by finding a shorter path, the additional computing energy spent to find that path will negate those savings. The algorithm formulates a stochastic shortest path problem based on Bayesian inference to estimate future actuation energy savings from homotopic class changes. We assess the trade-off between the computing energy required to continue sampling to potentially reduce the path length, the potential future actuation energy savings due to reduction in path length, and the overhead computing energy expenditure CEIMP introduces to decide when to stop computing. We evaluate CEIMP on realistic computational experiments involving 10 MIT building floor plans, and CEIMP outperforms the average baseline of using maximum computing resources. In one representative experiment on an embedded CPU (ARM Cortex A-15), for a simulated vehicle that uses one Watt to travel one meter per second, CEIMP saves 2.1-8.9x of the total energy on average across the 10 floor plans compared to the baseline, which translates to missions that can last equivalently longer on the same battery. As the the energy to move relative to the energy to compute decreases, the energy savings with CEIMP will increase, which highlights the advantage in spending computing energy to decide when to stop computing.
by Soumya Sudhakar.
S.M.
S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics
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Antoniadis, Antonios. "Scheduling algorithms for saving energy and balancing load." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2012. http://dx.doi.org/10.18452/16566.
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Diese Arbeit beschäftigt sich mit Scheduling von Tasks in Computersystemen. Wir untersuchen sowohl die in neueren Arbeiten betrachtete Zielfunktion zur Energieminimierung als auch die klassische Zielfunktion zur Lastbalancierung auf mehreren Prozessoren. Beim Speed-Scaling mit Sleep-State darf ein Prozessor, der zu jedem Zeitpunkt seine Geschwindigkeit anpassen kann, auch in einen Schlafmodus übergehen. Unser Ziel ist es, den Energieverbrauch zu minimieren. Wir zeigen die NP-Härte des Problems und klären somit den Komplexitätsstatus. Wir beweisen eine untere Schranke für die Approximationsgüte für eine spezielle natürliche Klasse von Schedules. Ferner entwickeln wir eine Familie von Algorithmen, die gute Approximationsfaktoren liefert, und zeigen, dass diese sogar Lösungen liefert, die optimal für die zuvor erwähnte Klasse von Schedules sind. Anschließend widmen wir unsere Aufmerksamkeit dem folgenden Termin-basierten Scheduling-Problem. Es seien mehrere Prozessoren gegeben, wobei jeder einzelne Prozessor zu jedem Zeitpunkt seine Geschwindigkeit anpassen kann. Ziel ist es wie zuvor, den Energieverbrauch des erzeugten Schedules zu minimieren. Für den Offline-Fall entwickeln wir einen optimalen Polynomialzeit-Algorithmus. Für das Online-Problem erweitern wir die zwei bekannten Ein-Prozessor-Algorithmen Optimal Available und Average Rate. Wir zeigen, dass diese den gleichen bzw. einen um die additive Konstante von eins vergrößerten kompetiven Faktor haben. Bei der Lastbalancierung auf mehreren Prozessoren betrachten wir Offline-Load-Balancing auf identischen Maschinen. Unser Ziel ist es, die Current-Load für temporäre Tasks mit identischem Gewicht zu minimieren. Wir zeigen, dass eine Lösung mit maximaler Imbalance von eins immer existiert und entwickeln einen effizienten Algorithmus, der solche Lösungen liefert. Zum Schluss beweisen wir die NP-Härte von zwei Verallgemeinerungen des Problems.This thesis studies problems of scheduling tasks in computing environments. We consider both the modern objective function of minimizing energy consumption, and the classical objective of balancing load across machines. We first investigate offline deadline-based scheduling in the setting of a single variable-speed processor that is equipped with a sleep state. The objective is that of minimizing the total energy consumption. Apart from settling the complexity of the problem by showing its NP-hardness, we provide a lower bound of 2 for general convex power functions, and a particular natural class of schedules. We also present an algorithmic framework for designing good approximation algorithms. Furthermore, we give tight bounds for the aforementioned particular class of schedules. We then focus on the multiprocessor setting where each processor has the ability to vary its speed. We first study the offline problem and show that optimal schedules can be computed efficiently in polynomial time. Regarding the online problem and a natural class of power functions, we extend the two well-known single-processor algorithms Optimal Available and Average Rate. We prove that Optimal Available has the same competitive ratio as in the single-processor case. For Average Rate we show a competitive factor that increases by an additive constant of one compared to the single-processor result. With respect to load balancing, we consider offline load balancing on identical machines, with the objective of minimizing the current load, for temporary unit-weight jobs. The problem can be seen as coloring n intervals with k colors, such that for each point on the line, the maximal difference between the number of intervals of any two colors is minimal. We prove that a coloring with maximal difference at most one is always possible, and develop a fast polynomial-time algorithm for generating such a coloring. Lastly, we prove that two generalizations of the problem are NP-hard.
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Padoin, Edson Luiz. "Energy-aware load balancing approaches to improve energy efficiency on HPC systems." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/140401.
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Os atuais sistemas de HPC tem realizado simulações mais complexas possíveis, produzindo benefícios para diversas áreas de pesquisa. Para atender à crescente demanda de processamento dessas simulações, novos equipamentos estão sendo projetados, visando à escala exaflops. Um grande desafio para a construção destes sistemas é a potência que eles vão demandar, onde perspectivas atuais alcançam GigaWatts. Para resolver este problema, esta tese apresenta uma abordagem para aumentar a eficiência energética usando recursos de HPC, objetivando reduzir os efeitos do desequilíbrio de carga e economizar energia. Nós desenvolvemos uma estratégia baseada no consumo de energia, chamada ENERGYLB, que considera características da plataforma, irregularidade e dinamicidade de carga das aplicações para melhorar a eficiência energética. Nossa estratégia leva em conta carga computacional atual e a frequência de clock dos cores, para decidir entre chamar uma estratégia de balanceamento de carga que reduz o desequilíbrio de carga migrando tarefas, ou usar técnicas de DVFS par ajustar as frequências de clock dos cores de acordo com suas cargas computacionais ponderadas. Como as diferentes arquiteturas de processador podem apresentam dois níveis de granularidade de DVFS, DVFS-por-chip ou DVFS-por-core, nós criamos dois diferentes algoritmos para a nossa estratégia. O primeiro, FG-ENERGYLB, permite um controle fino da frequência dos cores em sistemas que possuem algumas dezenas de cores e implementam DVFS-por-core. Por outro lado, CG-ENERGYLB é adequado para plataformas de HPC composto de vários processadores multicore que não permitem tal refinado controle, ou seja, que só executam DVFS-por-chip. Ambas as abordagens exploram desbalanceamentos residuais em aplicações interativas e combinam balanceamento de carga dinâmico com técnicas de DVFS. Assim, eles reduzem a frequência de clock dos cores com menor carga computacional os quais apresentam algum desequilíbrio residual mesmo após as tarefas serem remapeadas. Nós avaliamos a aplicabilidade das nossas abordagens utilizando o ambiente de programação paralela CHARM++ sobre benchmarks e aplicações reais. Resultados experimentais presentaram melhorias no consumo de energia e na demanda potência sobre algoritmos do estado-da-arte. A economia de energia com ENERGYLB usado sozinho foi de até 25% com nosso algoritmo FG-ENERGYLB, e de até 27% com nosso algoritmo CG-ENERGYLB. No entanto, os desequilíbrios residuais ainda estavam presentes após as serem tarefas remapeadas. Neste caso, quando as nossas abordagens foram empregadas em conjunto com outros balanceadores de carga, uma melhoria na economia de energia de até 56% é obtida com FG-ENERGYLB e de até 36% com CG-ENERGYLB. Estas economias foram obtidas através da exploração do desbalanceamento residual em aplicações interativas. Combinando balanceamento de carga dinâmico com DVFS nossa estratégia é capaz de reduzir a demanda de potência média dos sistemas paralelos, reduzir a migração de tarefas entre os recursos disponíveis, e manter o custo de balanceamento de carga baixo.Current HPC systems have made more complex simulations feasible, yielding benefits to several research areas. To meet the increasing processing demands of these simulations, new equipment is being designed, aiming at the exaflops scale. A major challenge for building these systems is the power that they will require, which current perspectives reach the GigaWatts. To address this problem, this thesis presents an approach to increase the energy efficiency using of HPC resources, aiming to reduce the effects of load imbalance to save energy. We developed an energy-aware strategy, called ENERGYLB, which considers platform characteristics, and the load irregularity and dynamicity of the applications to improve the energy efficiency. Our strategy takes into account the current computational load and clock frequency, to decide whether to call a load balancing strategy that reduces load imbalance by migrating tasks, or use Dynamic Voltage and Frequency Scaling (DVFS) technique to adjust the clock frequencies of the cores according to their weighted loads. As different processor architectures can feature two levels of DVFS granularity, per-chip DVFS or per-core DVFS, we created two different algorithms for our strategy. The first one, FG-ENERGYLB, allows a fine control of the clock frequency of cores in systems that have few tens of cores and feature per-core DVFS control. On the other hand, CGENERGYLB is suitable for HPC platforms composed of several multicore processors that do not allow such a fine-grained control, i.e., that only perform per-chip DVFS. Both approaches exploit residual imbalances on iterative applications and combine dynamic load balancing with DVFS techniques. Thus, they reduce the clock frequency of underloaded computing cores, which experience some residual imbalance even after tasks are remapped. We evaluate the applicability of our approaches using the CHARM++ parallel programming system over benchmarks and real world applications. Experimental results present improvements in energy consumption and power demand over state-of-the-art algorithms. The energy savings with ENERGYLB used alone were up to 25%with our FG-ENERGYLB algorithm, and up to 27%with our CG-ENERGYLB algorithm. Nevertheless, residual imbalances were still present after tasks were remapped. In this case, when our approaches were employed together with these load balancers, an improvement in energy savings of up to 56% is achieved with FG-ENERGYLB and up to 36% with CG-ENERGYLB. These savings were obtained by exploiting residual imbalances on iterative applications. By combining dynamic load balancing with the DVFS technique, our approach is able to reduce the average power demand of parallel systems, reduce the task migration among the available resources, and keep load balancing overheads low.
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Ooi, Chia Ai. "Balancing control for grid-scale battery energy storage systems." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/93020/.
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Grid-scale battery energy storage systems (BESSs) are becoming increasingly attractive as the connection of a BESS has been shown to improve the dynamic behaviours of the power grid. A key problem with BESSs is the potential for poor utilisation of mismatched cells and reliability issues resulting from the use of a large number of cells in series. This thesis proposes a technique for state-of-charge balancing of many thousands of cells individually (i.e. not in packs) using a tightly integrated power electronic circuit coupled with a new control system design. Cells are organised in a hierarchical structure consisting of modules, sub-banks, banks and phases. The control strategy includes five levels of balancing: balancing of cells within a module, balancing of modules within a sub-bank, sub-banks within a bank, banks in a phase and balancing between phases. The system seeks to maximise the accessible state-of-charge range of each individual cell, thereby enhancing the overall capacity of the system. The system is validated in simulation for a 380 kWh BESS using 2835 lithium-ion cells where charge balancing is demonstrated for mismatched cells. A ‘peak sharing’ concept is implemented to manage voltage constraints so that alternative modules assume a portion of the load when certain modules are not capable of meeting the demand. An experimental validation has been performed to demonstrate the effectiveness of the balancing control. This work is intended to address the challenges of eventual scaling towards a 100 MWh+ BESS, which may be composed of hundreds of thousands of individual cells.
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Gratwick, Katharine Nawaal. "Independent power projects in Africa : balancing development and investment outcomes." Doctoral thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/19641.
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Includes bibliographic references.In the early 1990s, a new model emerged for the provision of electricity generation across developing regions. The model involved private sector participation in the form of independent power projects (IPP). Driving this change in business was insufficient public finance from host country governments, a reduction in concessionary loans from multilateral and bilateral development institutions, and a push for improved efficiency in a state-owned utility sector that was considered to be underperforming. This dissertation reviews how IPPs developed across both North Africa and Sub-Saharan Africa. The analysis focuses on the extent to which positive development outcomes (viz. reliable and affordable power) and investment outcomes (viz. favourable investment returns and the opportunity to grow investments) were both achieved. The dissertation posits that balancing development and investment outcomes leads to greater sustainability for projects. It further explores a range of elements that contribute to the success of projects, namely: the investment climate; policy, regulatory and planning frameworks; competitive procurement practices; availability of competitively procured fuel; favourable debt and equity arrangements, including new trends in the nature of IPP firms and credit enhancement arrangements; and new risk management techniques. In-depth case studies of IPP experiences in Egypt, Kenya and Tanzania are used to explore the question of balancing outcomes and sustainability. Reviews of IPP experiences in Cote d'Ivoire, Ghana, Morocco, Nigeria and Tunisia also supplement the analysis together with an evaluation of the foreign direct investment context and related theory. Framing the whole discussion is an examination of how the new model for electric power provision evolved and how power sector reform models need to be adjusted to better reflect the reality in developing countries and emerging economies.
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Thiam, Cheikhou. "Anti load-balancing for energy-aware distributed scheduling of virtual machines." Toulouse 3, 2014. http://thesesups.ups-tlse.fr/2441/.
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La multiplication de l'informatique en nuage (Cloud) a abouti à la création de centres de données dans le monde entier. Le Cloud contient des milliers de nœuds de calcul. Cependant, les centres de données consomment d'énorme quantités d'énergie à travers le monde estimées à plus de 1,5 % de la consommation mondiale d'électricité et devrait continuer à croître. Une problématique habituellement étudiée dans les systèmes distribués est de répartir équitablement la charge. Mais lorsque l'objectif est de réduire la consommation électrique, ce type d'algorithmes peut mener à avoir des serveurs fortement sous chargés et donc à consommer de l'énergie inutilement. Cette thèse présente de nouvelles techniques, des algorithmes et des logiciels pour la consolidation dynamique et distribuée de machines virtuelles (VM) dans le Cloud. L'objectif principal de cette thèse est de proposer des stratégies d'ordonnancement tenant compte de l'énergie dans le Cloud pour les économies d'énergie. Pour atteindre cet objectif, nous utilisons des approches centralisées et décentralisées. Les contributions à ce niveau méthodologique sont présentées sur ces deux axes. L'objectif de notre démarche est de réduire la consommation de l'énergie totale du centre de données en contrôlant la consommation globale d'énergie des applications tout en assurant les contrats de service pour l'exécution des applications. La consommation d'énergie est réduite en désactivant et réactivant dynamiquement les nœuds physiques pour répondre à la demande des ressources. Les principales contributions sont les suivantes: - Ici on s'intéressera à la problématique contraire de l'équilibrage de charge. Il s'agit d'une technique appelée Anti Load-Balancing pour concentrer la charge sur un nombre minimal de nœuds. Le but est de pouvoir éteindre les nœuds libérés et donc de minimiser la consommation énergétique du système. - Ensuite une approche centralisée a été proposée et fonctionne en associant une valeur de crédit à chaque nœud. Le crédit d'un nœud dépend de son affinité pour ses tâches, sa charge de travail actuelle et sa façon d'effectuer ses communications. Les économies d'énergie sont atteintes par la consolidation continue des machines virtuelles en fonction de l'utilisation actuelle des ressources, les topologies de réseaux virtuels établis entre les machines virtuelles et l'état thermique de nœuds de calcul. Les résultats de l'expérience sur une extension de CloudSim (EnerSim) montrent que l'énergie consommée par les applications du Cloud et l'efficacité énergétique ont été améliorées. - Le troisième axe est consacré à l'examen d'une approche appelée "Cooperative scheduling Anti load-balancing Algorithm for cloud". Il s'agit d'une approche décentralisée permettant la coopération entre les différents sites. Pour valider cet algorithme, nous avons étendu le simulateur MaGateSim. Avec une large évaluation expérimentale d'un ensemble de données réelles, nous sommes arrivés à la conclusion que l'approche à la fois en utilisant des algorithmes centralisés et décentralisés peut réduire l'énergie consommée des centres de donnéesThe multiplication of Cloud computing has resulted in the establishment of largescale data centers around the world containing thousands of compute nodes. However, Cloud consume huge amounts of energy. Energy consumption of data centers worldwide is estimated at more than 1. 5% of the global electricity use and is expected to grow further. A problem usually studied in distributed systems is to evenly distribute the load. But when the goal is to reduce energy consumption, this type of algorithms can lead to have machines largely under-loaded and therefore consuming energy unnecessarily. This thesis presents novel techniques, algorithms, and software for distributed dynamic consolidation of Virtual Machines (VMs) in Cloud. The main objective of this thesis is to provide energy-aware scheduling strategies in cloud computing for energy saving. To achieve this goal, we use centralized and decentralized approaches. Contributions in this method are presented these two axes. The objective of our approach is to reduce data center's total energy consumed by controlling cloud applications' overall energy consumption while ensuring cloud applications' service level agreement. Energy consumption is reduced by dynamically deactivating and reactivating physical nodes to meet the current resource demand. The key contributions are: - First, we present an energy aware clouds scheduling using anti-load balancing algorithm : concentrate the load on a minimum number of severs. The goal is to turn off the machines released and therefore minimize the energy consumption of the system. - The second axis proposed an algorithm which works by associating a credit value with each node. The credit of a node depends on its affinity to its jobs, its current workload and its communication behavior. Energy savings are achieved by continuous consolidation of VMs according to current utilization of resources, virtual network topologies established between VMs, and thermal state of computing nodes. The experiment results, obtained with a simulator which extends CloudSim (EnerSim), show that the cloud application energy consumption and energy efficiency are being improved. - The third axis is dedicated to the consideration of a decentralized dynamic scheduling approach entitled Cooperative scheduling Anti-load balancing Algorithm for cloud. It is a decentralized approach that allows cooperation between different sites. To validate this algorithm, we have extended the simulator MaGateSim. With an extensive experimental evaluation with a real workload dataset, we got the conclusion that both the approach using centralized and decentralized algorithms can reduce energy consumed by data centers
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Gou, Changjiang. "Task Mapping and Load-balancing for Performance, Memory, Reliability and Energy." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEN047.
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Cette thèse se concentre sur les problèmes d'optimisation multi-objectifs survenant lors de l'exécution d'applications scientifiques sur des plates-formes de calcul haute performance et des applications de streaming sur des systèmes embarqués. Ces problèmes d'optimisation se sont tous avérés NP-complets, c'est pourquoi nos efforts portent principalement sur la conception d'heuristiques efficaces pour des cas généraux et sur la proposition de solutions optimales pour des cas particuliers.Certaines applications scientifiques sont généralement modélisées comme des arbres enracinés. En raison de la taille des données temporaires, le traitement d'une telle arborescence peut dépasser la capacité de la mémoire locale. Une solution pratique sur un système multiprocesseur consiste à partitionner l'arborescence en plusieurs sous-arbres, et à exécuter chacun d'eux sur un processeur, qui est équipé d'une mémoire locale. Nous avons étudié comment partitionner l'arbre en plusieurs sous-arbres de sorte que chaque sous-arbre tienne dans la mémoire locale et que le makespan soit minimisé, lorsque les coûts de communication entre les processeurs sont pris en compte. Ensuite, un travail pratique d'ordonnancement d'arbres apparaissant dans un solveur de matrice clairsemée parallèle est examiné. L'objectif est de minimiser le temps de factorisation en présentant une bonne localisation des données et un équilibrage de charge. La technique de cartographie proportionnelle est une approche largement utilisée pour résoudre ce problème d'allocation des ressources. Il réalise une bonne localisation des données en affectant les mêmes processeurs à de grandes parties de l'arborescence des tâches. Cependant, cela peut limiter l'équilibrage de charge dans certains cas. Basé sur une cartographie proportionnelle, un algorithme d'ordonnancement dynamique est proposé. Il assouplit le critère de localisation des données pour améliorer l'équilibrage de charge. La performance de notre approche a été validée par de nombreuses expériences avec le solveur direct à matrice clairsemée parallèle PaStiX. Les applications de streaming apparaissent souvent dans les domaines vidéo et audio. Ils se caractérisent par une série d'opérations sur le streaming de données et un débit élevé. Le système multiprocesseur sur puce (MPSoC) est un système embarqué multi / plusieurs cœurs qui intègre de nombreux cœurs spécifiques via une interconnexion haute vitesse sur une seule puce. De tels systèmes sont largement utilisés pour les applications multimédias. De nombreux MPSoC fonctionnent sur piles. Un budget énergétique aussi serré nécessite intrinsèquement un calendrier efficace pour répondre aux demandes de calcul intensives. La mise à l'échelle dynamique de la tension et de la fréquence (DVFS) peut économiser de l'énergie en diminuant la fréquence et la tension au prix d'une augmentation des taux de défaillance. Une autre technique pour réduire le coût énergétique et atteindre l'objectif de fiabilité consiste à exécuter plusieurs copies de tâches. Nous modélisons d'abord les applications sous forme de chaînes linéaires et étudions comment minimiser la consommation d'énergie sous des contraintes de débit et de fiabilité, en utilisant DVFS et la technique de duplication sur les plates-formes MPSoC.Ensuite, dans une étude suivante, avec le même objectif d'optimisation, nous modélisons les applications de streaming sous forme de graphes série-parallèle, plus complexes que de simples chaînes et plus réalistes. La plate-forme cible dispose d'un système de communication hiérarchique à deux niveaux, ce qui est courant dans les systèmes embarqués et les plates-formes informatiques hautes performances. La fiabilité est garantie par l'exécution des tâches à la vitesse maximale ou par la triplication des tâches. Plusieurs heuristiques efficaces sont proposées pour résoudre ce problème d'optimisation NP-completThis thesis focuses on multi-objective optimization problems arising when running scientific applications on high performance computing platforms and streaming applications on embedded systems. These optimization problems are all proven to be NP-complete, hence our efforts are mainly on designing efficient heuristics for general cases, and proposing optimal solutions for special cases.Some scientific applications are commonly modeled as rooted trees. Due to the size of temporary data, processing such a tree may exceed the local memory capacity. A practical solution on a multiprocessor system is to partition the tree into many subtrees, and run each on a processor, which is equipped with a local memory. We studied how to partition the tree into several subtrees such that each subtree fits in local memory and the makespan is minimized, when communication costs between processors are accounted for.Then, a practical work of tree scheduling arising in parallel sparse matrix solver is examined. The objective is to minimize the factorization time by exhibiting good data locality and load balancing. The proportional mapping technique is a widely used approach to solve this resource-allocation problem. It achieves good data locality by assigning the same processors to large parts of the task tree. However, it may limit load balancing in some cases. Based on proportional mapping, a dynamic scheduling algorithm is proposed. It relaxes the data locality criterion to improve load balancing. The performance of our approach has been validated by extensive experiments with the parallel sparse matrix direct solver PaStiX.Streaming applications often appear in video and audio domains. They are characterized by a series of operations on streaming data, and a high throughput. Multi-Processor System on Chip (MPSoC) is a multi/many-core embedded system that integrates many specific cores through a high speed interconnect on a single die. Such systems are widely used for multimedia applications. Lots of MPSoCs are batteries-operated. Such a tight energy budget intrinsically calls for an efficient schedule to meet the intensive computation demands. Dynamic Voltage and Frequency Scaling (DVFS) can save energy by decreasing the frequency and voltage at the price of increasing failure rates. Another technique to reduce the energy cost and meet the reliability target consists in running multiple copies of tasks. We first model applications as linear chains and study how to minimize the energy consumption under throughput and reliability constraints, using DVFS and duplication technique on MPSoC platforms.Then, in a following study, with the same optimization goal, we model streaming applications as series-parallel graphs, which are more complex than simple chains and more realistic. The target platform has a hierarchical communication system with two levels, which is common in embedded systems and high performance computing platforms. The reliability is guaranteed through either running tasks at the maximum speed or triplication of tasks. Several efficient heuristics are proposed to tackle this NP-complete optimization problem
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Portella, Rodrigo. "Balancing energy, security and circuit area in lightweight cryptographic hardware design." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEE036/document.
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Cette thèse aborde la conception et les contremesures permettant d'améliorer le calcul cryptographique matériel léger. Parce que la cryptographie (et la cryptanalyse) sont de nos jours de plus en plus omniprésentes dans notre vie quotidienne, il est crucial que les nouveaux systèmes développés soient suffisamment robustes pour faire face à la quantité croissante de données de traitement sans compromettre la sécurité globale. Ce travail aborde de nombreux sujets liés aux implémentations cryptographiques légères. Les principales contributions de cette thèse sont : - Un nouveau système d'accélération matérielle cryptographique appliqué aux codes BCH ; - Réduction de la consommation des systèmes embarqués et SoCs ; - Contre-mesures légères des attaques par canal auxiliaire applicables à l'algorithme de chiffrement reconfigurable AES ;- CSAC : Un pare-feu sécurisé sur la puce cryptographique ; - Attaques par analyse fréquentielle ; - Un nouveau protocole à divulgation nulle de connaissance appliquée aux réseaux de capteurs sans fil ; - OMD : Un nouveau schéma de chiffrement authentifiéThis thesis addresses lightweight hardware design and countermeasures to improve cryptographic computation. Because cryptography (and cryptanalysis) is nowadays becoming more and more ubiquitous in our daily lives, it is crucial that newly developed systems are robust enough to deal with the increasing amount of processing data without compromising the overall security. This work addresses many different topics related to lightweight cryptographic implementations. The main contributions of this thesis are: - A new cryptographic hardware acceleration scheme applied to BCH codes; - Hardware power minimization applied to SoCs and embedded devices; - Timing and DPA lightweight countermeasures applied to the reconfigurable AES block cipher; - CSAC: A cryptographically secure on-chip firewall; - Frequency analysis attack experiments; - A new zero-knowledge zero-knowledge protocol applied to wireless sensor networks; - OMD: A new authenticated encryption scheme
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Du, Plessis Louis Kemp. "Integrating non-dispatchable renewable energy into the South African grid : an energy balancing view / L.K. du Plessis." Thesis, North-West University, 2013. http://hdl.handle.net/10394/9648.
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The integration of dispatchable renewable energies like biomass, geothermal and reservoir hydro technologies into an electrical network present no greater challenge than the integration of conventional power technologies for which are well understood by Eskom engineers. However, renewable energies that are based on resources that fluctuate throughout the day and from season to season, like wind and solar, introduce a number of challenges that Eskom engineers have not dealt with before.
It is current practice for Eskom‟s generation to follow the load in order to balance the demand and supply. Through Eskom‟s load dispatching desk at National Control, generator outputs are adjusted on an hourly basis with balancing reserves making up only a small fraction of the total generation.
Through the Integrated Resource Plan for Electricity of 2010, the Department of Energy has set some targets towards integrating renewable energy, including wind and solar generation, into the South African electricity market consequently introducing variability on the supply side.
With demand that varies continually, maintaining a steady balance between supply and demand is already a challenging task. When the supply also becomes variable and less certain with the introduction of non-dispatchable renewable energy, the task becomes even more challenging.
The aim of this research study is to determine whether the resources that previously helped to balance the variability in demand will still be adequate to balance variability in both demand and supply. The study will only concentrate on variable or non-dispatchable renewable energies as will be added to the South African electrical network according to the first two rounds of the Department of Energy‟s Renewable Energy Independent Power Producer Procurement Programme.
This research study only looks into the balancing challenge and does not go into an analysis of voltage stability or network adequacy, both of which warrant in depth analysis.Thesis (MIng (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2013.
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Ruthberg, Richard, and Sebastian Wogenius. "Stochastic Modeling of Electricity Prices and the Impact on Balancing Power Investments." Thesis, KTH, Industriell ekonomi och organisation (Inst.), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192111.
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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.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.
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Issaeva, Natalia. "Quantifying the system balancing cost when wind energy is incorporated into electricity generation system." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3804.
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Incorporation of wind energy into the electricity generation system requires a detailed analysis of wind speed in order to minimize system balancing cost and avoid a significant mismatch between supply and demand. Power generation and consumption in the electricity networks have to be balanced every minute, therefore it is necessary to study wind speed on a one-minute time scale. In this thesis, we examine the statistical characteristics of one-minute average values of wind speed. One-minute wind speed is available from a single site in Great Britain while there are records of ten-minute wind speed available. We apply a modified Gibbs sampling algorithm to generate one-minute wind speed required for optimization modelling from the available ten-minute wind speed. System balancing costs are estimated through optimization modelling of the short-term electricity generation with wind energy contributing to the total supply. Two main drivers of additional system cost caused by wind energy are variability and unpredictability of one-minute wind speed. Further, a linear mathematical optimization model for a problem of short-term electricity generation is presented to calculate an additional balancing cost that appears as a result of wind energy variability. It is then shown that this additional balancing cost can be estimated using the statistical characteristics of wind energy present in the system. The unpredictable characteristic of wind speed is analysed with the techniques of stochastic programming. Uncertainty of the expected wind speed is represented through scenario trees and stochastic linear optimization models are used to calculate the extra cost due to uncertainty. Alternative optimization models are compared by calculating the additional balancing cost and the extent of imbalance between power generation and consumption in the system.
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Ibrahim, Rwan. "An energy-efficient and load-balancing cluster-based routing protocol for wireless sensor networks." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119428.
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Clustering is a popular routing technique in configuring Wireless Sensor Networks (WSNs). It can determine the communications between all nodes to collect data in an efficient manner. It handles the main challenge of energy-efficiency in WSNs, and can be used to re-configure the network according to changes in the nodes' conditions. This thesis contributes to the routing in WSNs by proposing an Energy-efficient and Load-balancing Cluster-based (ELC) routing algorithm for Carrier Sense Multiple Access (CSMA)-based WSNs. In particular, both distance and residual energy are taken into consideration in developing the cluster-head selection procedure while ensuring that the network has a desired number of cluster heads. In addition to distance, cluster size is also used in formulating the cost function for cluster forming in order to balance load and energy consumption among the nodes, and hence, enhancing the network lifetime. Besides, ELC employs multi-hop inter-cluster routing based on a lowest-cost path approach that considers both energy efficiency and load balancing. Illustrative simulation results show that ELC consumes less energy and offers longer network lifetime as compared to other existing cluster-based routing algorithms such as Low-Energy Adaptive Clustering Hierarchy-Centralized (LEACH-C) protocol and Central Base Station Controlled Density Aware Clustering Protocol (CBCDACP).Le clustering est une technique de routage populaire utilisée dans la configuration d'un réseau de capteurs sans fil. Cette technique peutétablir les paramètres de communication entre tous les nœuds du réseau pour une collecte de données plus efficace. Elle traite l'obstacle principal à la performance des réseaux de capteurs sans fil, l'efficacité énergétique, et peut être utilisée dans la reconfiguration du réseau selon le changement de conditions des nœuds. La contribution de cette thèse au domaine de routage dans les réseaux de capteurs sans fil consiste dans la présentation d'un nouvel algorithme de routage à base de clustering écoénergétique et d'équilibrage de charge (en anglais, Energy-efficient and Load-balancing Cluster-based routing algorithm ou ELC) pour les réseaux de capteurs sans fil à base de accès multiple avec écoute de porteuse. Particulièrement, les critères de distance et énergie résiduelle sont pris en considération dans la formulation de la procédure de sélection des Cluster Heads (CHs) tout en garantissant que le réseau est formé en tout temps par un nombre désirable de CHs. Outre que la distance, la taille du cluster est de même utilisée dans la formulation de la fonction du coût de la formation des clusters. Ceci vise à équilibrer la répartition de charges et l'énergie des nœuds du réseau, et par conséquence, à aboutir à une plus longue durée de vie du réseau. En outre, ELC emploie une technique de routage inter-cluster avec sauts multiples qui se base sur une approche au moindre coût qui prend en considération l'efficacité énergétique et l'équilibrage de charge dans le réseau. Les simulations démontrent que ELC consomme moins d'énergie et aboutit à une plus longue durée de vie du réseau par rapport à d'autres algorithmes de routage à base de clustering comme LEACH-C et CBCDACP.
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Bortot, Baptiste. "Gas for Balancing of Variable Power Generation : A Systemic Case Study." Thesis, KTH, Elektriska energisystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-144860.
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With the increasing share of variable renewable generation, balancing electric powersystems could become a major concern for system operators because of their variableand hardly predictable nature. However, gas technologies appear as a solutionto provide this flexibility, but the impacts on the gas power system have hardly beeninvestigated. In this thesis, consulting reports on the subject matter, regulator suggestions andgas-electricity interaction models in scientific literature are studied and four sourcesare identified to be used for balancing: linepack, storage facilities, liquefied natural gasand intraday gas supply from adjacent areas. Then, a gas-electricity model for flexibility supply is designed and three case studies are simulated in order to analyze bothgas and electric power systems’ behaviors. In these case studies, electricity generation,contribution of gas sources and costs are analysed. The study concludes that critical situations on gas market that can occur, e.g. incases of large variation in the net electricity demand and limited availability of linepackand storage facilities, the need of intraday modulation can exceed the possibilities toprovide for it. Then, gas cannot be supplied to power plants during peak periods, andmore gas than necessary is used during off-peak periods. The case studies also showthat day-ahead forecast errors in variable renewable generation can be handled mucheasier than variations by the gas system but leads to higher costs.
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Dupin, Nicolas. "Portfolio balancing strategy for the integration of renewable energy sources to the day ahead market." Thesis, KTH, Energiteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-246114.
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New methods of government support and marketing of renewable production push the renewable energy sources (RES) to be more integrated to the wholesale day-ahead market. In this way, predictive models of production for solar and wind power have been developed to manage the resulting balancing costs. They aim to forecast the production of a plant for the following day at hourly intervals, based on historical operational and meteorological data. They are backed by three machine learning algorithms, which are the Artificial Neural Networks (ANN), the Support Vector Regression (SVR) and the Random Forest (RF). These models are evaluated on 20 solar farms and 2 wind farms, through 3 criteria which are the RMSE, the RMSEN and the R-square. It gives significantly improved performances compared to ‘persistence method’ or other naive methods. In most cases, the best results were obtained with the random forest algorithm, with an average RMSEN of 15% and an average R-square of 0,8. Considering these models and ideal operational conditions, the balancing costs are evaluated for each solar farm, showing the lowest obtainable costs with these models. The average cost calculated ranges from 1 to 1,4 € per MWh produced depending on the power plant considered. However, thanks to the ‘portfolio benefit effect’, the combination of the forecasting errors of multiple sites can highly decrease this cost. Strategies of portfolio combination can be developed by increasing the installed capacity and the number of sites within the portfolio and/or diversifying the locations or the types of RES used. The savings go up to 45% of the initial simple balancing costs.Nya metoder för statligt stöd och marknadsföring av förnybar produktion driver förnybara energikällor (RES) för att vara mer integrerade på grossistmarknaden för framtida varor. På detta sätt har förutsägda produktionsmodeller för sol och vindkraft utvecklats för att hantera de resulterande balanseringskostnaderna. De syftar till att prognostisera produktion av en växt för följande dag med timmars intervall, baserat på historiska operativa och meteorologiska data. De stöds av tre maskininlärningsalgoritmer, som är Artificial Neural Networks (ANN), Support Vector Regression (SVR) och Random Forest (RF). Dessa modeller utvärderas på 20 solparker och 2 vindkraftverk, genom 3 kriterier som är RMSE, RMSEN och R-kvadraten. Det ger signifikant förbättrade prestanda jämfört med "persistensmetod" eller andra naiva metoder. I de flesta fall erhölls de bästa resultaten med Random Forest algoritm, med en genomsnittlig RMSEN på 15% och en genomsnittlig R-square på 0,8. Med tanke på dessa modeller och idealiska driftsförhållanden utvärderas balanseringskostnaderna för varje solkraftverk, vilket visar de lägsta tillgängliga kostnaderna med dessa modeller Den genomsnittliga kostnaden beräknas sträcka sig från 1 till 1,4 € per MWh producerad beroende på vilken kraftverk som övervägs. Tack vare "portföljförmånseffekten" kan kombinationen av prognostiseringsfel på flera webbplatser emellertid mycket minska denna kostnad. Strategier för portföljkombination kan utvecklas genom att öka den installerade kapaciteten och antalet platser inom portföljen och / eller diversifiera de platser eller typer av RES som används. Besparingarna går upp till 45% av de initiala enkla balanseringskostnaderna.
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Sakib, Kazi Muheymin-Us, and s3091580@rmit edu au. "Energy Balanced Sensor Node Organisation For Maximising Network Lifetime." RMIT University. Computer Science and Information Technology, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080805.135709.
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Recent advances in Micro-Electro-Mechanical Systems (MEMS) and low-power short-range radios have enabled rapid development of wireless sensor networks. Future sensor networks are anticipated to include hundreds or thousands of these devices in many applications, such as capturing multimedia content for surveillance, structural health monitoring, tracking of accidental chemical leaks, machine failures, earthquakes and intrusion detection. With the increase of sensor applications, a number of challenging problems related to the network protocol design has emerged - the most important ones relating to energy efficiency and lifetime maximisation. Techniques devised for sensor networks should deal with a large number of sensors distributed in the field. Wireless sensor nodes are deployed with limited energy reserves, so the networks should operate with minimum energy overhead. In fact, the network should take into account not only individual node's energy efficiency but also consider the global picture, because surviving nodes' energy reserves in a failed network are wasted energy. This thesis examines a node organisation technique to deal with the above challenges. The focus is on improving network lifetime via organising the nodes in a distributed and energy efficient manner. The main goal is lowering wasted energy via energy balancing and exploiting node redundancy in case of node failure. In particular, this thesis proposes Energy Balanced Clustering (EBC) method for node self-organisation where network tasks (such as data aggregation and data forwarding) are shifted to high-energy neighbours to reduce the energy consumption of low energy nodes. After showing how to extend network lifetime by energy balanced node organisation, the effect of redundant node deployments on network lifetime is addressed. Redundant nodes consume energy by performing unnecessary tasks so a method called Self-Calculated Redundancy Check (SCRC) is proposed to deactivate redundant nodes. A deactivated redundant node can be used as a replacement for a failed node. The Asynchronous Failed Sensor node Detection (AFSD) proposed in this thesis uses the data packets exchanged between neighbours to identify failed neighbours. To restore coverage for network holes caused by failed nodes, policies are given for re-activating redundant nodes. Detailed analytical analysis and simulation of the proposed methods demonstrate that by taking into account energy balancing, eliminating redundant tasks and replacing failed nodes sensor network lifetime can significantly be improved.
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Grant, Benedict M. B. "Finite Element Modelling of Inertia Friction Welding Advanced Nickel-Based Superalloys Using an Energy Balancing Approach." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505492.
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Scharff, Richard. "Design of Electricity Markets for Efficient Balancing of Wind Power Generation." Doctoral thesis, KTH, Elektriska energisystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171063.
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Deploying wind power to a larger extent is one solution to reduce negative environmental impacts of electric power supply. However, various challenges are connected with increasing wind power penetration levels. From the perspective of transmission system operators, this includes balancing of varying as well as - to some extent - uncertain generation levels. From the perspective of power generating companies, changes in the generation mix will affect the market's merit order and, hence, their profits. This thesis focuses on provision and use of flexibility in the Nordic electricity market. First, this thesis studies wind power variations and accuracy of wind power forecasts in Sweden using statistical methods. Even though today’s wind penetration levels are still low in Sweden, power systems and electricity markets have to cope with these characteristics of variations and forecast errors to a larger extent in future. Second, it investigates to which extent an increased exchange and use of flexibility that is available in the intraday time-frame could efficiently facilitate system balancing and whether this would also be profitable from the power generating companies' perspective. Here, a simulation model is developed that reflects important aspects of production planning and trading decisions in the intraday time-frame. In a first case study, it is shown that the benefits of internal rescheduling strongly depend on the costs to adjust production plans in the intraday time-frame as compared to real-time. In a second case study, it becomes evident that trading flexibility in the intraday time-frame can reduce the need for system balancing more efficiently than internal rescheduling within each balance responsible party. Motivated by the positive gains of intraday trading and the challenge of appropriately modelling continuous intraday markets, trading activity and price development on Elbas is investigated. The results provide insights into trading behaviour on a continuous intraday market and show that trading is not always in accordance to the power system's physical situation. To the extent to which better information and adaptations in the market design could improve the market participants' base for trading decisions, policy recommendations and further research questions areas suggested.Att använda vindkraft i en större utsträckning är en möjlighet att minska elproduktionens negativa miljöpåverkan. Det finns dock också olika utmaningar med stora mängder vindkraft. Från ett systemperspektiv gäller det till exempel att hålla balansen mellan tillförsel och konsumtion av el. Från elproducenternas perspektiv bör vindkraftens påverkan på elmarknaden nämnas eftersom det påverka aktörernas vinster. Avhandlingen titta närmare in i hur man kan få tillgång till mer flexibilitet på produktionssidan. Avhandlingen består av tre delar. För det första undersöks variationer och prognosfel av vindkraft i Sverige med hjälp av statistiska metoder. Även om andel vindkraft hittills är låg i Sverige, behöver elsystemet och elmarknader i framtiden hantera samma egenskaper av själva variationer och prognosfel som idag men i en större utsträckning. För det andra undersöks hur den flexibiliteten som finns i tidshorisonten några timmar innan leveranstimmen kan utnyttjas för att integrera vindkraften på ett sätt som är både fördelaktigt från systemets och från aktörernas perspektiv. Undersökningen sker med hjälp av en simuleringsmodell som omfattar viktiga delar i produktionsplanering och intradayhandel. I en fallstudie uppvisas att vinster av intern omplanering är i högsta grad beroende på kostnadsskillnaden mellan omplanering några timmar innan leveranstimmen och anpassning av körscheman under själva leveranstimmen. Resultat av ytterligare en fallstudie uppvisar att det är betydligt billigare och mer effektivt att använda intradayhandel istället för intern omplanering för att utnyttja den befintliga flexibiliteten och för att reducera obalanser som systemoperatörer annars behöver ta hand om under leveranstimmen. Detta är en anledning till att undersöka handelsmönster på Elbas som är en intradaymarknad med kontinuerlig handel. En annan anledning till den här tredje delen är utmaningarna i att modellera kontinuerlig intradayhandel. Studien beskriver handelsaktiviteten på Elbas och hur priserna utvecklas under handelstiden. Ett resultat är att handeln inte alltid återspeglar den fysiska situationen i elsystemet. I den utsträckningen som ett snabbare informationsflöde och förändringar i marknadsdesignen kunde förbättrar aktörernas underlag för intradayhandel, föreslås förbättringar och öppna forskningsfrågor.
QC 20150911
Elektra 36141: Korttidsplanering av vatten-värmekraftsystem vid stora mängder vindkraft: System-perspektivet
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Ptak, Thomas. "Understanding Hydropower in China: Balancing Energy Security, Development, and Environmental Sustainability in the Nu River Valley of Yunnan Province." Thesis, University of Oregon, 2016. http://hdl.handle.net/1794/20445.
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Research to date analyzing socioeconomic, social and environmental implications emanating from hydropower development in China has focused disproportionally on macro-scale projects, specifically large dams. The very size of these projects should not, but largely have, obscured other developments of significance; small hydropower operations. Small dams and diversion stations with an operating capacity of 50 Megawatts or less represent approximately a third of installed hydroelectric capacity in China. Recently, the proliferation of small hydropower has rapidly increased, particularly in Yunnan province. A belief that small hydropower operations are an environmentally sound alternative to burning coal, which contributes to China’s much publicized air quality issues and global climate challenges drives current development. However, despite the significance of small-scale projects, research to date has largely neglected their role. As a result of this ‘tunnel vision’, an integral component of China’s hydropower assemblage has received inadequate attention, remaining little known and less understood. This dissertation is the result of research that investigates small hydropower development in a rural and remote corner of China’s Nu river valley, located in the far northwest of Yunnan province. Objectives of the research were evaluating the effectiveness of small operations to promote socioeconomic development in rural and remote communities while contributing to China’s broader energy security demands. In addition, the research evaluated the ways hydropower development and the supply of electricity shaped the social circumstances in village communities of the upper Nu river valley. Finally, this research analyzed a range of environmental implications resulting from small operations that were both evident on local landscapes and in spaces far removed.10000-01-01
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Simon, Derek. "Static Balancing of the Cal Poly Wind Turbine Rotor." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/837.
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The balancing of a wind turbine rotor is a crucial step affecting the machine’s performance, reliability, and safety, as it directly impacts the dynamic loads on the entire structure.
A rotor can be balanced either statically or dynamically. A method of rotor balancing was developed that achieves both the simplicity of static balancing and the accuracy of dynamic balancing. This method is best suited, but not limited, to hollow composite blades of any size. The method starts by quantifying the mass and center of gravity of each blade. A dynamic calculation is performed to determine the theoretical shaking force on the rotor shaft at the design operating speed. This force is converted to a net counterbalance mass required for each blade. Despite the most careful methodology, there may still be large errors associated with these measurements and calculations. Therefore, this new method includes a physical verification of each blade’s individual balance against all other blades on the rotor, with the ability to quantify the discrepancy between blades, and make all balance adjustments in situ. The balance weights are aluminum plugs of varying lengths inserted into the root of each blade with a threaded steel rod running through the middle. The balance adjustment is thus not visible from outside. The weight of the plug and rod represent the coarse counterbalance of each blade, based on the dynamic calculations. The threaded steel rod acts as a fine adjustment on the blades’ mass moment when traveled along the plug. A dedicated blade-balance apparatus, designed and constructed in-house, is used to verify and fine-tune each individual blade and compare it to all other blades on the rotor. The resulting blade assembly is verified on a full rotor static balancing apparatus. The full rotor apparatus measures the steady state tilt of the rotor when balanced on a point. Next, the rotors' tilt is related to its overall level of imbalance with quantifiable error. Most error comes from the fact that the hub, comparable in mass to the blades, creates a false righting moment of the assembly not present in operation. The fully assembled rotor is tested, pre and post balance, in operation on the turbine at a series of predetermined speeds. This is accomplished with a 3-axis accelerometer mounted on the main turbine shaft bearing and a control system which regulates and records turbine speed at 100 Hz
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Antoniadis, Antonios [Verfasser], Susanne [Akademischer Betreuer] Albers, Christoph [Akademischer Betreuer] Dürr, and Andrzej [Akademischer Betreuer] Lingas. "Scheduling algorithms for saving energy and balancing load / Antonios Antoniadis. Gutachter: Susanne Albers ; Christoph Dürr ; Andrzej Lingas." Berlin : Humboldt Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2012. http://d-nb.info/1025291131/34.
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Anderson, Matthew John. "Economic and Environmental Analysis of Cool Thermal Energy Storage as an Alternative to Batteries for the Integration of Intermittent Renewable Energy Sources." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/51195.
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The balance of the supply of renewable energy sources with electricity demand will become increasingly difficult with further penetration of renewable energy sources. Traditionally, large stationary batteries have been used to store renewable energy in excess of electricity demand and dispatch the stored energy to meet future electricity demand. Cool thermal energy storage is a feasible renewable energy balancing solution that has economic and environmental advantages over utility scale stationary lead-acid batteries. Two technologies, ice harvesters and internal-melt ice-on-coil cool thermal energy storage, have the capability to store excess renewable energy and use the energy to displace electricity used for building cooling systems. When implemented by a utility, cool thermal energy storage can replace large utility scale batteries for renewable energy balancing in utility regions with high renewable energy penetration. The California Independent System Operator (CAISO) region and the Electric Reliability Council of Texas (ERCOT) are utility regions with large solar and wind resources, respectively, that can benefit from installation of cool thermal energy storage systems for renewable energy balancing. With proper scheduling of energy dispatched from cool thermal energy storage, these technologies can be effective in displacing peak power capacity for the region, in displacing traditional building cooling equipment, and in recovering renewable energy that would otherwise be curtailed.Master of Science
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Lyons, Selina. "A study of wind energy, power system balancing and its effects on carbon emissions in the Australian NEM." Thesis, Lyons, Selina (2014) A study of wind energy, power system balancing and its effects on carbon emissions in the Australian NEM. Masters by Coursework thesis, Murdoch University, 2014. https://researchrepository.murdoch.edu.au/id/eprint/25284/.
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With the increasing installation of wind power around the world the questions surrounding its benefits and issues are also growing at the same rate. This paper analyses the wind energy in the Australian National Electricity Market (NEM) using actual data from 2012 and 2013 and attempts to answer some of the pressing questions around how variable the wind output is, its impact on carbon emissions, and its influence on other generators especially those balancing the power system. Starting with a static study of generation half hour data, the report then looks in more detail at the 5-minute variability experienced across the NEM, and the corresponding impact on frequency and time error for large excursions. Notably the largest variations experienced in wind power are during wind storms in the wind power zones of South Australia and Victoria. Three of these storms are analysed in detail looking at the individual performance of the wind farms and their contribution to the variability. Lastly, the effect of the wind variations on the regulation or balancing generators is studied – in particular with large increases in wind power that causes fossil-fueled generators to decrease their output and hence efficiency. Using the Australian Energy Market Operator (AEMO) planning assumptions, the carbon emissions for each of the fossil-fueled generators providing balancing are estimated to show the trends in emissions, intensity and clearly show the effects directly caused by wind power.
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Gils, Hans Christian [Verfasser], and André [Akademischer Betreuer] Thess. "Balancing of intermittent renewable power generation by demand response and thermal energy storage / Hans Christian Gils. Betreuer: André Thess." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2016. http://d-nb.info/1081367563/34.
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Carpa, Radu. "Energy Efficient Traffic Engineering in Software Defined Networks." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEN065/document.
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Ce travail a pour but d'améliorer l'efficacité énergétique des réseaux de cœur en éteignant un sous-ensemble de liens par une approche SDN (Software Defined Network). Nous nous différencions des nombreux travaux de ce domaine par une réactivité accrue aux variations des conditions réseaux. Cela a été rendu possible grâce à une complexité calculatoire réduite et une attention particulière au surcoût induit par les échanges de données. Pour valider les solutions proposées, nous les avons testées sur une plateforme spécialement construite à cet effet.Dans la première partie de cette thèse, nous présentons l'architecture logicielle ``SegmenT Routing based Energy Efficient Traffic Engineering'' (STREETE). Le cœur de la solution repose sur un re-routage dynamique du trafic en fonction de la charge du réseau dans le but d'éteindre certains liens peu utilisés. Cette solution utilise des algorithmes de graphes dynamiques pour réduire la complexité calculatoire et atteindre des temps de calcul de l'ordre des millisecondes sur un réseau de 50 nœuds. Nos solutions ont aussi été validées sur une plateforme de test comprenant le contrôleur SDN ONOS et des commutateurs OpenFlow. Nous comparons nos algorithmes aux solutions optimales obtenues grâce à des techniques de programmation linéaires en nombres entiers et montrons que le nombre de liens allumés peut être efficacement réduit pour diminuer la consommation électrique tout en évitant de surcharger le réseau.Dans la deuxième partie de cette thèse, nous cherchons à améliorer la performance de STREETE dans le cas d’une forte charge, qui ne peut pas être écoulée par le réseau si des algorithmes de routages à plus courts chemins sont utilisés. Nous analysons des méthodes d'équilibrage de charge pour obtenir un placement presque optimal des flux dans le réseau.Dans la dernière partie, nous évaluons la combinaison des deux techniques proposées précédemment : STREETE avec équilibrage de charge. Ensuite, nous utilisons notre plateforme de test pour analyser l'impact de re-routages fréquents sur les flux TCP. Cela nous permet de donner des indications sur des améliorations à prendre en compte afin d'éviter des instabilités causées par des basculements incontrôlés des flux réseau entre des chemins alternatifs. Nous croyons à l'importance de fournir des résultats reproductibles à la communauté scientifique. Ainsi, une grande partie des résultats présentés dans cette thèse peuvent être facilement reproduits à l'aide des instructions et logiciels fournisThis work seeks to improve the energy efficiency of backbone networks by automatically managing the paths of network flows to reduce the over-provisioning. Compared to numerous works in this field, we stand out by focusing on low computational complexity and smooth deployment of the proposed solution in the context of Software Defined Networks (SDN). To ensure that we meet these requirements, we validate the proposed solutions on a network testbed built for this purpose. Moreover, we believe that it is indispensable for the research community in computer science to improve the reproducibility of experiments. Thus, one can reproduce most of the results presented in this thesis by following a couple of simple steps. In the first part of this thesis, we present a framework for putting links and line cards into sleep mode during off-peak periods and rapidly bringing them back on when more network capacity is needed. The solution, which we term ``SegmenT Routing based Energy Efficient Traffic Engineering'' (STREETE), was implemented using state-of-art dynamic graph algorithms. STREETE achieves execution times of tens of milliseconds on a 50-node network. The approach was also validated on a testbed using the ONOS SDN controller along with OpenFlow switches. We compared our algorithm against optimal solutions obtained via a Mixed Integer Linear Programming (MILP) model to demonstrate that it can effectively prevent network congestion, avoid turning-on unneeded links, and provide excellent energy-efficiency. The second part of this thesis studies solutions for maximizing the utilization of existing components to extend the STREETE framework to workloads that are not very well handled by its original form. This includes the high network loads that cannot be routed through the network without a fine-grained management of the flows. In this part, we diverge from the shortest path routing, which is traditionally used in computer networks, and perform a particular load balancing of the network flows. In the last part of this thesis, we combine STREETE with the proposed load balancing technique and evaluate the performance of this combination both regarding turned-off links and in its ability to keep the network out of congestion. After that, we use our network testbed to evaluate the impact of our solutions on the TCP flows and provide an intuition about the additional constraints that must be considered to avoid instabilities due to traffic oscillations between multiple paths
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Celanovic, Nikola. "Space Vector Modulation and Control of Multilevel Converters." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/29164.
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This dissertation is the result of research and development of a power conditioning system for Superconductive Magnetic Energy Storage System. The dominant challenge of this research was to develop the power conditioning system that can match slowly varying dc voltage and dc current on the super conductive magnet side with the ac voltages and ac currents on the utility side. At the same time the power conditioning system was required to provide a bi-directional power flow to the superconductive magnet.
The focus of this dissertation is a three-level diode clamped dc-ac converter which is a principle part of the power conditioning system. Accordingly, this dissertation deals with the space vector modulation of three-level converters and introduces a computationally very efficient three-level space vector modulation algorithm that is experimentally verified.
Furthermore, the proposed space vector modulation algorithm is successfully generalized to allow equally efficient, real time implementation of space vector modulation to dc-ac converters with virtually any number of levels. The most important advantage of the proposed concept is in the fact that the number of instructions required to implement the algorithm is almost independent from the number of levels in a multilevel converter.
More on the side of the control of multilevel converters, the particular attention in this dissertation is paid to the problem of charge balance in the split dc-link capacitors of three-level neutral-point-clamped converters. It is a known fact that although the charge balance in the neutral point can be maintained on a line cycle level, a significant third harmonic current flows into the neutral point for certain loading conditions, causing the neutral point voltage ripple. The logical consequence of that ripple is the deteriorated quality of the output voltage waveforms as well as the increased voltage stress on the switching devices.
This was the motivation to more carefully explore the loading conditions that cause the unbalance, as well as to study the fundamental limitations of dc-link capacitor charge balancing algorithms. As a part of that work, a new model of the neutral point current in the rotating coordinate frame is developed as a tool in investigation of theoretical limitations and in providing some intuitive insight into the problem. Additionally, the low frequency ripple is quantified and guidelines are offered that can help size the dc-link capacitors.
Because the study of the neutral point balance identified the loading conditions, that under some possible system constraints, cause an unavoidable neutral point voltage ripple, a feed forward type of control method is developed next. The proposed feed forward algorithm can effectively prevent the neutral point voltage ripple from creating distortions in the converter output voltage under all loading conditions and without causing additional disturbance in the neutral point voltage. The feed forward method is developed for a sine triangle as well as for the space vector type PWM algorithm.
The simulation results that include the full dynamic model of the converter and load system validate the feed forward approach and prove that the feed forward algorithm can effectively compensate the effect of the neutral point voltage ripple. The simulation results are than experimentally verified.Ph. D.
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Patrick, Stasha Noelle. "Control of aggregate electric water heaters for load shifting and balancing intermittent renewable energy generation in a smart grid environment." Thesis, Montana State University, 2011. http://etd.lib.montana.edu/etd/2011/patrick/PatrickS1211.pdf.
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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.
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Gustafsson, Dennis. "Comparing air quality in a training facility : What effects do air balancing have for carbon dioxide reduction?" Thesis, Högskolan i Gävle, Energisystem, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-24049.
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The link between a good indoor climate and environmental impacts e.g. global warming and different pollution in the air is something that are important today and will certainly become more important in the future with increased energy prices and new laws. Too keep the indoor air quality within limits is it important to have a good and competitive ventilationsystem. The ventilations function is mainly to supply fresh air and to remove polluted air from the room. It’s important that the ventilation system works as it should so that the indoor air quality is as good as possible. The lack of good ventilation can create several symptoms such as headaches, nausea, fatigue, poor concentration etc. In Sweden are ventilation control mandatory for every newly produced building and this control are repetitive usually every 3-6 years for some types of buildings. The foundation of this thesis is from a previous degree project performed by a master’s student in 2013 named Ander Barroeta with supervision of Magnus Mattsson and Taghi Karimipanah. The thesis was to improve and design a ventilation system in two rooms at a training facility named Friskis & Svettis in Gävle so that the CO2 level did not exceed 1000 ppm. In this thesis was the main goal to do similar measurements as the previous thesis and compare the results to see what difference air balancing has done to the ventilation system. Field measurements were performed at the training facility were the focus was on carbon dioxide but also on other parameters such as temperature, humidity and air velocity so that air exchange rate could be calculated. With these parameters can evaluations be made to see if air balancing of the ventilation system made any difference in indoor air quality. During measurements in one of the training rooms where spinning is exercised was carbon dioxide levels up to 3300 ppm measured which is above the recommended indoor limit at 1000 ppm. If that room should be design to not exceed 1000 ppm must the air exchange rate increase from 6.3 h-1 to 35.1 h-1.
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Курбатова, Тетяна Олександрівна, Татьяна Александровна Курбатова, Tetiana Oleksandrivna Kurbatova, Ярославна Сергіївна Романюк, Ярославна Сергеевна Романюк, Yaroslavna Serhiivna Romaniuk, and Г. С. Трипольська. "United Energy System of Ukraine: towards integration into ENTSO-E." Thesis, Sumy State University, 2021. https://essuir.sumdu.edu.ua/handle/123456789/86282.
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Розглянуто особливості функціонування загальноєвропейської та української енергетичних систем. Проаналізовано проблеми балансування української енергосистеми, обумовлені стрімким розвитком відновлюваної енергетики в країні. Окреслено процедуру та переваги синхронізації Об’єднаної енергетичної системи України з ENTSO-E.Peculiarities of functioning European and Ukrainian energy systems are considered. The problems of balancing the Ukrainian energy system due to the rapid development of renewable energy in the country are analyzed. The procedure and advantages of synchronization of the United Energy System of Ukraine with ENTSO-E are outlined.
The publication was prepared in the framework of the research project "Formation of economic mechanisms for sustainable development of renewable energy in the conditions of global and local threats to the energy security of Ukraine" (№ 0120U104806) funded by the National Research Foundation of Ukraine.
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Quiggin, Daniel. "Modelling the expected participation of future smart households in demand side management, within published energy scenarios." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/16220.
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The 2050 national energy scenarios as planned by the DECC, academia and industry specify a range of different decarbonised supply side technologies combined with the electrification of transportation and heating. Little attention is paid to the household demand side; indeed within many scenarios a high degree of domestic Demand Side Management (DSM) is implicit if the National Grid is to maintain supply-demand balance. A top-down, bottom-up hybrid model named Shed-able Household Energy Demand (SHED) has been developed and the results of which presented within this thesis. SHED models six published national energy scenarios, including three from the Department for Energy and Climate Change, in order to provide a broad coverage of the possible energy scenario landscape. The objective of which is to quantify the required changes in current household energy demand patterns via DSM, as are implicit under these highly electricity dominated scenarios, in order to maintain electrical supply-demand balance at the national level. The frequency and magnitude of these required household DSM responses is quantified. SHED performs this by modelling eleven years of supply-demand dynamics on the hourly time step, based on the assumptions of the published energy scenarios as well as weather data from around 150 weather stations around the UK and National Grid historic electricity demand data. The bottom-up component of SHED is populated by 1,000 households hourly gas and electricity demand data from a recently released dataset from a smart metering trial in Ireland. This aggregate pool of households enables national domestic DSM dynamics to be disaggregated to the aggregate household level. Using household classifications developed by the Office for National Statistics three typical ' households are identified within the aggregate pool and algorithms developed to investigate the possible required responses from these three households. SHED is the first model of its kind to connect national energy scenarios to the implications these scenarios may have on households consumption of energy at a high temporal resolution. The analysis of the top-down scenario modelling shows significant periods where electrical demand exceeds supply within all scenarios, within many scenarios instances exist where the deficit is unserviceable due to lack of sufficient spare capacity either side of the deficit period. Considering the level of participation required within the modelled scenarios in order to balance the electricity system and the current lack in understanding of smart metering and Time-Of-Use (TOU) tariffs within households, it would seem there is a disconnect between the electricity system being planned, the role this system expects of households and the role households are willing to play.
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Nazaritalooki, Vahid. "Reliable and energy efficient routing for ad hoc networks." Doctoral thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14008.
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Doutoramento em InformáticaIn Mobile Ad hoc NETworks (MANETs), where cooperative behaviour is mandatory, there is a high probability for some nodes to become overloaded with packet forwarding operations in order to support neighbor data exchange. This altruistic behaviour leads to an unbalanced load in the network in terms of traffic and energy consumption. In such scenarios, mobile nodes can benefit from the use of energy efficient and traffic fitting routing protocol that better suits the limited battery capacity and throughput limitation of the network. This PhD work focuses on proposing energy efficient and load balanced routing protocols for ad hoc networks. Where most of the existing routing protocols simply consider the path length metric when choosing the best route between a source and a destination node, in our proposed mechanism, nodes are able to find several routes for each pair of source and destination nodes and select the best route according to energy and traffic parameters, effectively extending the lifespan of the network. Our results show that by applying this novel mechanism, current flat ad hoc routing protocols can achieve higher energy efficiency and load balancing. Also, due to the broadcast nature of the wireless channels in ad hoc networks, other technique such as Network Coding (NC) looks promising for energy efficiency. NC can reduce the number of transmissions, number of re-transmissions, and increase the data transfer rate that directly translates to energy efficiency. However, due to the need to access foreign nodes for coding and forwarding packets, NC needs a mitigation technique against unauthorized accesses and packet corruption. Therefore, we proposed different mechanisms for handling these security attacks by, in particular by serially concatenating codes to support reliability in ad hoc network. As a solution to this problem, we explored a new security framework that proposes an additional degree of protection against eavesdropping attackers based on using concatenated encoding. Therefore, malicious intermediate nodes will find it computationally intractable to decode the transitive packets. We also adopted another code that uses Luby Transform (LT) as a pre-coding code for NC. Primarily being designed for security applications, this code enables the sink nodes to recover corrupted packets even in the presence of byzantine attacks.
Nas redes móveis ad hoc (MANETs), onde o comportamento cooperativo é obrigatório, existe uma elevada probabilidade de alguns nós ficarem sobrecarregados nas operações de encaminhamento de pacotes no apoio à troca de dados com nós vizinhos. Este comportamento altruísta leva a uma sobrecarga desequilibrada em termos de tráfego e de consumo de energia. Nestes cenários, os nós móveis poderão beneficiar do uso da eficiência energética e de protocolo de encaminhamento de tráfego que melhor se adapte à sua capacidade limitada da bateria e velocidade de processamento. Este trabalho de doutoramento centra-se em propor um uso eficiente da energia e protocolos de encaminhamento para balanceamento de carga nas redes ad hoc. Actualmente a maioria dos protocolos de encaminhamento existentes considera simplesmente a métrica da extensão do caminho, ou seja o número de nós, para a escolha da melhor rota entre fonte (S) e um nó de destino (D); no mecanismo aqui proposto os nós são capazes de encontrar várias rotas por cada par de nós de origem e destino e seleccionar o melhor caminho segundo a energia e parâmetros de tráfego, aumentando o tempo de vida útil da rede. Os nossos resultados mostram que pela aplicação deste novo mecanismo, os protocolos de encaminhamento ad hoc actuais podem alcançar uma maior eficiência energética e balanceamento de carga. Para além disso, devido à natureza de difusão dos canais sem fio em redes ad-hoc, outras técnicas, tais como a Codificação de Rede (NC), parecem ser também promissoras para a eficiência energética. NC pode reduzir o número de transmissões, e número de retransmissões e aumentar a taxa de transferência de dados traduzindo-se directamente na melhoria da eficiência energética. No entanto, devido ao acesso dos nós intermediários aos pacotes em trânsito e sua codificação, NC necessita de uma técnica que limite as acessos não autorizados e a corrupção dos pacotes. Explorou-se o mecanismo de forma a oferecer um novo método de segurança que propõe um grau adicional de protecção contra ataques e invasões. Por conseguinte, os nós intermediários mal-intencionados irão encontrar pacotes em trânsito computacionalmente intratáveis em termos de descodificação. Adoptou-se também outro código que usa Luby Transform (LT) como um código de précodificação no NC. Projectado inicialmente para aplicações de segurança, este código permite que os nós de destino recuperem pacotes corrompidos mesmo em presença de ataques bizantinos.
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Nilsson, Martin. "On Efficient Transmission Balancing Operation : Capturing the Normal State Frequency and Active Power Dynamics." Licentiate thesis, KTH, Elkraftteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-221221.
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In an electric power system, there will always be an electric balance. Nevertheless, System Operators (SOs) often uses the term imbalance. Here, the term imbalance refers to the difference between trades and real-time measurements. This thesis defines the term imbalance and develops a framework helping SOs in finding better decisions controlling these imbalances. Imbalances are controlled by many decisions made at various stages before real-time. A decision can be to increase the flexibility in production and consumption. However, this is not the only decision affecting real-time balancing operation. Other decisions are grid code requirements, such as ramp rates of HVDC and generation; balancing market structure, such as imbalance fees and trading period lengths; and the strategies used in the system-operational dispatch. The purpose of this thesis is to create a new possibility for SO to find decisions improving the balancing operation. In order to find and compare decisions, the thesis develops a framework that evaluates many different decisions made at various stages before real-time. The framework consists of the following. First, it develops an intra-hour model using multi-bidding zone data from a historical time-period; able to capture the normal state frequency and active power dynamics. The model creates high-resolution data from low-resolution measurements using several data-processing methods. The uncertainty from the historical time-period is re-created using many sub-models with different input data, time-scales and activation times of reserves. Secondly, the framework validates the model and identifies system parameters based on simulated frequencies and frequency measurements in the normal state operation. Finally; new decisions' are modelled, tested, and evaluated on their impact on selected targets supporting corporate missions of the SOs. The goal of the framework is that it should be able to find better decisions for balancing operation but also that it should be applicable for real and large power systems. To verify this, the framework is tested on a synchronous area containing 11 bidding zones in northern Europe. Results show that the framework can be validated and trusted. Three new decisions, made at various stages before real time, have been modelled, tested and evaluated. The modelled decisions were (i) lower ramp rates for generation, (ii) increased capacities for automatic reserves, and (iii) a new strategy for the system-operational dispatch. One implication of applying the balancing evaluation framework on data from July 2015 is that all tested decisions improve several selected targets supporting the corporate missions of the SOs. The conclusion is that the balancing framework is useful as a simulation tool in helping SOs in finding more efficient decisions for transmission system balancing operation.QC 20180116
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Mared, Oskar, and Victor Persson. "Balancing Supply and Demand in an Electricity System - the Case of Sweden." Thesis, KTH, Industriell ekonomi och organisation (Inst.), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-249499.
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In an electrical system there needs to be a constant balance between supply and demand ofelectricity and this is measured by the frequency in the grid. Due to the increasing awarenessof climate change, more renewable energy resources have been introduced in the Swedishelectricity system. This is, however, not solely positive since renewable energy sources areoften of intermittent character which entails more imbalances between supply and demand. Inaddition, statistics and data show that the deviation in the frequency in the Nordic system hasincreased during the latest years. Thus, in this thesis, the issues regarding the frequency havebeen addressed by examining the demand for frequency control in the Swedish electricitysystem and what balancing efforts that can be carried out on a local level to contribute to abetter balanced system. This thesis has been conducted at KTH Royal Institute of Technologywith collaboration with the commissioner Mälarenergi AB. A case study of the Swedish electricity system has been carried out to gather empiricalmaterial and this material has been analyzed using Geels theory on technical transitions, themulti-level perspective. The results indicates that it is likely the demand for frequency controlwill increase, and this is due to factors as more intermittent energy, current market design fortrading electricity, overseas transmission connections, decommissioning of nuclear powerand limited internal transmission capacity. Three other developments have been identified,which could have a large impact on the demand in the future, as an increasing use of electricvehicles, prosumers and the deployment of IoT in the energy sector. These developmentshave not been integrated to a large extent yet in the energy sector and thus have a moreuncertain impact. In terms of resources, the thesis has identified that it is likely that hydropower will continueto be the main resource for frequency regulation. Another source that could be used morefrequently than today and possibly compete with hydropower is combined heat and powerplants. Furthermore, the study has found that local actors can contribute by advertisingsmaller local resources on a market for trading regulating power called“reglerkraftmarknaden”, that balance providing companies collaborate, that the load iscontrolled in the local grids or that smaller local production facilities are operated in standalonemode during extreme situations.För att uppnå ett välfungerande elektrisk system så måste det vara en konstant balans mellan produktion och konsumtion av el i systemet. Den här balansen mäts genom att mäta frekvensen i elnätet. Eftersom allt fler har blivit mer medvetna om de klimatförändringar vår planet står inför har det successivt införts mer och mer förnybara energikällor i det svenska elsystemet. Den här utvecklingen har inte enbart varit positivt, eftersom förnybara energikällor ofta är av intermittent karaktär, vilket har medfört att balansen mellan produktion och konsumtion av el har försämrats. Flertalet undersökningar har påvisat att det förekommer mer frekvensavvikelser i det nordiska elsystemet idag än tidigare. Denna rapport har således undersökt dessa problem genom att analysera efterfrågan på frekvensreglering i det svenska elsystemet och vilka initiativ som kan tas på lokal nivå för att förbättra balansen i elsystemet. Rapporten har genomförts på Kungliga Tekniska Högskolan i samarbete med uppdragsgivaren Mälarenergi AB. Rapporten har genomfört en fallstudie av det svenska elsystemet för att samla in empiriskt material, och detta material har i sin tur analyserats genom Geels flernivåsansats. De resultat som har framkommit i undersökningen visar på att det är troligt att efterfrågan av frekvensreglering kommer att öka. Denna ökning beror på faktorer som att mer intermittent energi integreras i elnätet, hur marknaden för att handla elektricitet är utformad, fler utländska överföringsförbindelser, nedrustning av kärnkraft och begränsad överföringskapacitet inom det nationella elnätet. Tre andra utvecklingar har identifierats som möjligen kan ha en stor påverkan på behovet av frekvensreglering. Dessa är ett ökat antal elektriska fordon, prosumenter och att energisektorn integreras av IoT och smarta objekt i större utsträckning än idag. Dessa faktorer har inte integrerats i det svenska elsystemet nämnvärt ännu och deras påverkan är därmed mer osäker. Denna studie har också kommit fram till att vattenkraft troligtvis kommer fortsätta att vara den resurs som används mest för frekvensreglering, men även att kraftvärmeverk har potential att användas mer för reglering än idag. Vidare har rapporten även identifierat att lokala aktörer kan bidra till en bättre balans i systemet genom att antingen annonsera mindre lokala resurser på reglerkraftmarknaden, öka samarbetet mellan balansansvariga företag, kontrollera lasten i lokala elnät eller att mindre lokala produktionsanläggningar drivs i ö-drift under extrema situationer.
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Overmaat, Eduard. "Balancing Contributions in the Nordic Electricity System : Who bears the brunt of electricity production and consumption patterns?" Thesis, Uppsala universitet, Elektricitetslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-393570.
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The share of intermittent weather-based renewable electricity sources has risen and will keep on rising in the Nordic electricity system, which will increase the need of balancing power in the Nordics. The previously developed concept of balancing contributions is used to look at the historic contribution of different power sources to the balancing on the grid. Three different time scales are taken into account: Daily variations, (bi-)weekly variations, and seasonal/yearly variations. This will aid in the understanding of the synergy of different sources on the grid, which, together with a deeper knowledge of the electricity market, might make it possible in the future to quantify the potential for balancing of sources within the Nordic grid. As a method to analyse the balancing contributions, a previously set-up online visualisation tool was used as an example, and this existing tool was revamped with a new software back-end using a database and automatic data collection. This allows one to be able to use a larger dataset, and for more functionality in the future, such as real-time updates and easier implementation of additional visualisations. Production and consumption data was gathered from Entso-e and SvK: the former has issues with data quality and the latter publishes data with a three-week delay which can only be obtained manually. The results from the previous research have been replicated, and a bigger dataset has been used to do the calculations, encompassing the years 2015-2018. The overall results show great similarity to that of the previous work. For the first time it was possible to plot the intrayear balancing contributions as a time series, which showed especially that the contributions of hydro power and electricity trade have changed over the period 2015-2018. There is a difference in hydro power balancing contributions based on geographical location, where Finnish hydro power is mainly a daily and—to a lesser extent—weekly regulator, Swedish hydro and especially Norwegian hydro have larger contributions on a yearly basis as well. There are even differences within countries, as the balancing contribution of hydro in bidding area SE2 has changed much more over time than hydro in SE1, for example. Other examples of interesting situations on the grid have also been highlighted using the online visualisation tool.
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Chattopadhyay, Kabitri Verfasser], Hans-Georg [Akademischer Betreuer] Beyer, and Ulrike [Akademischer Betreuer] [Feudel. "Optimization of spatial balancing and storage needs for large-scale power system integration of fluctuating solar energy / Kabitri Chattopadhyay ; Hans-Georg Beyer, Ulrike Feudel." Oldenburg : BIS der Universität Oldenburg, 2017. http://d-nb.info/1137323051/34.
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Bourdette, Romain. "An Economical & Technical Study of the Participation of a Virtual Power Plant on the Swiss Balancing Market : WRITTEN IN COLLABORATION WITH SWISSELECTRICITY." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-187690.
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The current shift towards renewable energy resources creates volatility in the electricity production that must be compensated by nevi sources of balancing energy. To ensure a normal operation of the power system, the transmission system operators procure power reserves able to provide regulation energy through market processes. Virtual power plants are now likely to participate on the balancing markets. In this study, the technical and economic feasibility of having virtual power plants participate in the Swiss balancing market is assessed. The study begins with the evaluation and compa.rison of four European balancing market designs and continues with the clarification of the concept of virtual power plant. The focus is then set on the Swiss ancillary services market, recently open to virtual pmver plants. After a detailed market description, an economic model simulating the participation of a virtual power plant made of industrial resources on the secondary and tertiary control markets has been developed. This model \Vas evaluated on an actual market design: the Sv.riss ancillary servicel:l market. 5 cases were simulated, allowing to estimate the opportunity fom both the capacity and the energy market productl:l. The simulations indicated that an example company (based on an actual situation) could hope a decrease in its energy cost between :3 and 4% by participating in a control pool over a year. Other simulations demonstrated the greater profit expected from secondary reserves compared to tertiary rel:lerves, and the need to develop an automatized activation system. The encouraging economic study is followed by a technical overview of the envisioned system. A generic technical characterization of virtual power plant is presented, on v.rhich the Swiss use-case is later applied. The breakdown into functional requirements allowed to highlight specific issues. The design of the control strategy, particularly to deliver secondary control, as well as the hardware communication interface to use are tvw aspects that ,vill require further analysis. Additionally, on an economic level, the investment cost for remote communication modules are acceptable with respect to the economic potentials estimated in the first part, for mediumsized industrial energy resources. In conclusion, the study established the profitability of an aggregation project on the Swisl:l market but also demonstrated the need to pursue research for the project to be fully feasible on a technical level.
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Phadke, Swanand Shripad. "Distributed Control for Smart Lighting." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1274899902.
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Neugebauer, Reimund, Uwe Götze, and Welf-Guntram Drossel. "Methoden der energetisch-wirtschaftlichen Bilanzierung und Bewertung in der Produktionstechnik: Methodenworkshop der Querschnittsarbeitsgruppe 1 „Energetisch-wirtschaftliche Bilanzierung“ des Spitzentechnologieclusters eniPROD." Verlag Wissenschaftliche Scripten, 2011. https://monarch.qucosa.de/id/qucosa%3A19610.
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Mit dem Spitzentechnologiecluster „Energieeffiziente Produkt- und Prozessinnovationen in der Produktionstechnik“ (eniPROD®) werden die am Wissenschaftsstandort Chemnitz vorhandenen exzellenten Forschungsbereiche gebündelt, um einen national und international sichtbaren Beitrag zur Umsetzung der Vision einer nahezu emissionsfreien Produktion bei gleichzeitiger Erhöhung der Ressourceneffizienz zu leisten.
Um dieses Ziel erreichen zu können, sind Methoden erforderlich, mit denen Energieverbräuche unter Einbeziehung technischer, ökonomischer und ökologischer Kriterien erfasst und bewertet werden können.
Die im Rahmen von eniPROD® gebildete Querschnittsarbeitsgruppe 1 „Energetisch-wirtschaftliche Bilanzierung“ setzt sich intensiv mit solchen Bilanzierungs- und Bewertungsmethoden auseinander. Der vorliegende Band enthält die Beiträge eines von der Querschnittsarbeitsgruppe initiierten Workshops, in dem verschiedene Facetten des Themenkomplexes der energetisch-wirtschaftlichen Bilanzierung und Bewertung von Wissenschaftlern verschiedener Disziplinen aufgegriffen und diskutiert wurden.
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Westerberg, Jacob. "Active Phase Balancing and Battery Systems for Peak Power Reduction in Residential Real Estate : An Economic Feasibility Study." Thesis, KTH, Industriell Management, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-272974.
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Research has shown that three-phase balancing alone can improve the operation of secondary distribution networks and that the addition of energy storage to the phase balancing power electronics further helps to alleviate the negative effects of phase unbalances. However, less attention has been paid to the economic potential of said technologies and particularly for loadside implementation. It appears that the deployment of phase balancers, with or without energy storage, is indeed hampered by uncertainty related to its economic feasibility, despite both technologies being commercially available. This thesis therefore aims to assess and compare the economic feasibility of the two configurations for peak shaving purposes in the context of residential property loads in Sweden. The assessment was performed using a specially developed deterministic techno-economic model taking into consideration historical load data from three Swedish real estate, cost estimations for a range of alternatives used when sizing the systems, applicable tariffs and fees for electricity and its distribution as well as technical parameters such as the capacities and efficiencies of the involved components. A novel approach was taken by linearly extrapolating the three load profiles into three sets of 91 synthesized load profiles to enable a larger dataset for analysis. The net present values generated for each set were then graphed and analyzed per original real estate. The results showed that both configurations can be economically feasible, but only under certain conditions. A phase balancer alone was found to be feasible for real estate whose peak currents are distinctly unbalanced and exceed 50 A, with the best expected rate of return for profiles exceeding 63 A since they enable a tariff switch. The combined system was found to be even more contingent on the tariff switch and therefore only feasible for peaks above 63 A. A substantial difference in the initial investment further makes the single phase balancer the preferred choice, unless the discount rate is as low as 2 % or less. On this basis, potential investors need to assess the state of unbalance of their loads and perform their own calculation based their load profile, cost of capital and applicable tariffs.Tidigare forskning har visat att fasbalansering enskilt kan förbättra driften hos lokala distributionsnät och att ett batterisystem i tillägg till fasbalanserarens kraftelektronik ytterligare kan minska de negativa effekterna av fasobalanser. Däremot har mindre uppmärksamhet riktats mot den ekonomiska genomförbarheten hos dessa teknologier och i synnerhet för implementation på lastens sida av elmätaren. Det tycks vara så att spridningen av fasbalanserare, med eller utan energilagring, hindras av osäkerheten kring dess ekonomiska potential trots att båda teknologierna är kommersiellt tillgängliga. Detta arbete ämnar därför att värdera och jämföra den ekonomiska nyttan hos de två konfigurationerna vid toppreducering av fastighetselen i svenska bostadsfastigheter. Värderingen utfördes med hjälp av en särskilt utvecklad deterministisk tekno-ekonomisk modell som beaktade historiska lastdata från tre svenska fastigheter, kostnadsuppskattningar för en uppsättning av konfigurationer som användes vid dimensionering av systemen, applicerbara tariffer och avgifter för elektricitet och dess distribution samt tekniska parametrar såsom kapaciteter och verkningsgrader för de olika komponenterna. Ett annorlunda tillvägagångssätt tillämpades vidare för att utöka datamängden genom linjär extrapolation av lastprofilerna, vilket resulterade i tre uppsättningar av 91 syntetiserade lastprofiler. Nettonuvärdet beräknades följaktligen för varje profil och investeringsalternativ för att sedan plottas och analyseras per ursprunglig fastighet. Resultaten visade att båda konfigurationerna kan uppvisa lönsamhet, men endast under särskilda förutsättningar. Den enskilda fasbalanseraren bedömdes som lönsam för fastigheter vars strömtoppar är påtagligt obalanserade och som överstiger 50 A, med största möjliga lönsamhet för profiler som överstiger 63 A då dessa möjliggör ett tariffbyte. Det kombinerade systemets lönsamhet bedömdes vara ännu mer beroende av tariffbytet och därför endast lönsamt för strömtoppar över 63 A. En betydligt större grundinvestering för det kombinerade systemet gör vidare att den enskilda fasbalanseraren i regel är att föredra, såvida inte kalkylräntan är så låg som 2 % eller mindre. Baserat på detta uppmanas potentiella investerare att undersöka balanstillståndet hos deras laster och att utföra en egen kalkyl baserat på deras specifika last, kapitalkostnad och nätföretag.
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PORPORA, Francesco. "Design and Prototyping of Battery Management Systems for Lithium-ion Battery Packs." Doctoral thesis, Università degli studi di Cassino, 2021. http://hdl.handle.net/11580/83987.
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High-performance equalization circuits have to satisfy different requirements, including modularity, scalability, weight and volume, reliability, cost, hardware and software complexity. Currently, the design targets are mainly focused on minimizing the equalization time and the overall size of the circuit. This also implies the definition of a proper thermal management for dissipating the heat generated due to the high balancing currents that may be needed.
However, literature and industry standards do not address the problem of the optimal sizing of the equalization circuits, which is strongly affected by the operating conditions of the battery pack as well as the parameter variations of the components adopted. The original contribute proposed in this dissertation regards the definition of design methodologies for passive and active equalization circuits that take into account for relevant aspects of both battery pack and power electronics components. Firstly, the real operating conditions of both individual cells and the overall battery pack have been
considered in terms of cell technology, temperature, model calibration and voltage imbalances among the cells. Secondly, the real behavior of the components used for the specific equalization circuit and their parameter variations have be taken into account. In this way, a proper evaluation of the performance of the equalization circuits can be achieved by considering their functionalities in real operating conditions. In particular, design strategies have been proposed for four BMS architectures, one for each main equalization type, including passive, capacitor-based, inductor-based and transformed-based solutions. Moreover, a novel architecture for an active equalization circuit has been developed for the transformer-based equalizer, which allows for achieving a cells-to-cells energy transfer. Besides the development of design strategies for passive and active equalization circuits, real prototypes have been sized and implemented as well. In detail, a modular architecture for the passive equalizer of a 50HP electric kart and the novel active equalizer have been prototyped with the aim of validating their performance in real-world environments. These prototypes also allow for managing high-voltage battery packs or hybrid systems, which are composed by different technologies
of batteries (second life applications). Moreover, a detailed comparison between the prototypes developed has been carried out in order to highlight their main features in different operating conditions, including charging, discharging and idle state.
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Baranauskas, Audrius. "Elektrinių ir energijos kaupimo sistemų valdymo modelis vėjo elektrinių galiai balansuoti." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2015. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20150109_113032-87509.
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Daktaro disertacijoje tyrinėjamos vėjo elektrinių balansavimo galimybės panaudojant energijos kaupimo sistemas ir sprendžiamas balansavimo galių valdymo uždavinys. Darbo metu buvo ištirta vėjo elektrinių prognozavimo paklaidų įtaka balansavimo galioms, sudaryti balansavimo galių valdymo ir energijos kaupimo sistemų dinaminiai modeliai ir nustatyti tokių sistemų parametrai vėjo elektrinių galių subalansavimui atsižvelgiant į valdymo signalo kitimo greitį ir balansuojančių elektrinių galios keitimo spartą. Darbo išvados ir sukaupta informacija yra reikšminga integruojant energijos kaupimo sistemas į automatinio generavimo valdymo sistemos darbą. Pasiūlyti sprendimai leidžia tiksliau nustatyti reguliavimo rezervo apimtis bei pagerinti sistemos režimo parametrų valdymo kokybę.Wind power balancing using energy storage systems as well as balancing control strategies are investigated in the thesis. The wind power balancing options are expanded by proposed dynamic models according to control signal rate of change and power plants ramp rates. The influence of wind power forecasting errors to regulating power reserve was investigated. The required energy storage system parameters for wind power balancing were determined and the regulation intensity of conventional power plants was reduced. The results obtained in the thesis are useful for energy storage systems integration into the central automatic generation control system. The solutions proposed let to increase the determination accuracy of regulating active power reserves and improve the quality of the system control parameters.
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Mubenga, Ngalula Sandrine. "A Lithium-Ion Battery Management System with Bilevel Equalization." University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1513207337549147.
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Santo, Luca. "AA-CAES physical modelling: integration of a 1D TES code and plant performance analysis." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-360448.
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The focus of this thesis work was the development of an approachto couple a previosly existing Thermal Energy Storage (TES) modelwritten in C++ with a Simulink/Simscape plant model to simulate anAdvanced Adiabatic Compressed Air Energy Storage (AA-CAES) plant.After the creation and validation of such tool, the complete modelwas used to run simulations, with the aim of assessing the AA-CAESplant's performance under multiple patterns of charge anddischarge.Most of the works found in the literature only provide values ofstorage efficiency obtained from analytical approaches, whilethose that use simulation tools provide average values ofefficiencies when the plant is performing a series of identicalcycles of charge and discharge. During this thesis project,instead, simulations were performed for consecutive irregularcycles determined as the plant response to the electric grid powerrequest. The average efficiency values obtained provide thereforea better representation of how the plant would perform in realapplications.The results show that, under the assumptions made, the AA-CAESplant's overall storage efficiency is influenced very weakly byalterations of the charge-discharge patterns, and that goodperformances can be expected not only for identical chargedischargeconsucutive cycles, but for any pattern that observesthe cavern pressure limits, as long as the thermal energy storageis sized wisely.In addition, a sensitivity analysis was performed in order toassess the influence of turbomachinery efficiency on overallstorage efficiency, for a specified plant layout. The results showthat the turbine efficiency is the most affecting parameter to theplant's performance, while the impact of the main compressors'sinefficiency is mitigated by the thermal recovery that takes placein the TES.The present work confirms that AA-CAES is a promising technologyand that storage efficiencies above 70% can be achieved even inrealistic production scenarios.Finally, future steps for more accurate simulations of plants'performances and more detailed energy production scenarios areproposed.MSc ET 18007Examinator: Joakim WidénÄmnesgranskare: Ane HåkanssonHandledare:
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Kheriji, Sabrine. "Design of an Energy-Aware Unequal Clustering Protocol based on Fuzzy Logic for Wireless Sensor Networks." Universitätsverlag Chemnitz, 2020. https://monarch.qucosa.de/id/qucosa%3A73303.
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Energy consumption is a major concern in Wireless Sensor Networks (WSNs) resulting in a strong demand for energy-aware communication technologies. In this context, several unequal cluster-based routing protocols have been proposed. However, few of them adopt energetic analysis models for the calculation of the optimal cluster radius and several protocols can not realize an optimal workload balance between sensor nodes.
In this scope, the aim of the dissertation is to develop a cluster-based routing protocol for improving energy efficiency in WSN. We propose a Fuzzy-based Energy-Aware Unequal Clustering algorithm (FEAUC) with circular partitioning to balance the energy consumption between sensor nodes and solve the hotspot problem created by a multi-hop communication. The developed FEAUC involves mainly four phases: An off-line phase, a cluster formation phase, a cooperation phase and data collection phase. During the off-line phase, an energy analysis is performed to calculate the radius of each ring and the optimal cluster radius per ring. The cluster formation phase is based on a fuzzy logic approach for the cluster head (CH) selection. The cooperation phase aims to define an intermediate node as a router between different CHs. While, in the data collection phase, transmitting data packet from sensor nodes to their appropriate CHs is defined as an intra-cluster communication, and transmitting data from one CH to another until reaching the base station, is defined as an inter-cluster communication. The feasibility of the developed FEAUC is demonstrated by elaborating comparison with selected referred unequal clustering algorithms considering different parameters, mainly, the energy consumption, battery lifetime, time to first node shuts down (FND), time of half of nodes off-line (HND) and time to last node dies (LND).
Although, the developed FEAUC is intended to enhance the network lifetime by distributing the large load of CH tasks equally among the normal nodes, running the clustering process in each round is an additional burden, which can significantly drain the remaining energy. For this reason, the FEAUC based protocol has been further developed to become a fault tolerant algorithm (FEAUC-FT). It supports the fault tolerance by using backup CHs to avoid the re-clustering process in certain rounds or by building further routing paths in case of a link failure between different CHs.
The validation of the developed FEAUC in real scenarios has been performed. Some sensor nodes, powered with batteries, are deployed in a circular area forming clusters. Performance evaluations are carried out by realistic scenarios and tested for a real deployment using the low-power wireless sensor node panStamp. To complete previous works, as a step of proof of concept, a smart irrigation system is designed, called Air-IoT. Furthermore, a real-time IoT-based sensor node architecture to control the quantity of water in some deployed nodes is introduced. To this end, a cloud-connected wireless network to monitor the soil moisture and temperature is well-designed. Generally, this step is essential to validate and evaluate the proposed unequal cluster-based routing algorithm in a real demonstrator. The proposed prototype guarantees both real-time monitoring and reliable and cost-effective transmission between each node and the base station.:1 Introduction
2 Theoretical background
3 State of the art of unequal cluster-based routing protocols
4 FEAUC: Fuzzy-based Energy-Aware Unequal Clustering
5 Experimental validation of the developed unequal clustering protocol
6 Real application to specific uses cases
7 Conclusions and future research directionsDer Energieverbrauch ist ein Hauptanliegen in drahtlosen Sensornetzwerken (WSNs), was zu einer starken Nachfrage nach energiebewussten Kommunikationstechnologien führt. In diesem Zusammenhang wurden mehrere ungleiche clusterbasierte Routing-Protokolle vorgeschlagen. Allerdings verwenden nur die wenigsten energetische Analysemodelle für die Berechnung des optimalen Cluster-Radius, und mehrere Protokolle können keine optimale Auslastungsbalance zwischen Sensorknoten realisieren. In diesem Zusammenhang ist es das Ziel der Dissertation, ein clusterbasiertes Routing-Protokoll zur Verbesserung der Energieeffizienz im WSN zu entwickeln. Wir schlagen einen Fuzzy-basierten Energy-Aware Unequal Clustering-Algorithmus (FEAUC) mit zirkulärer Partitionierung vor, um den Energieverbrauch zwischen Sensorknoten auszugleichen und das durch eine Multi-Hop-Kommunikation entstehende Hotspot-Problem zu lösen. Der entwickelte FEAUC umfasst hauptsächlich vier Phasen: Eine Offline-Phase, eine Clusterbildungsphase, eine Kooperationsphase und eine Phase der Datensammlung. Während der Offline-Phase wird eine Energieanalyse durchgeführt, um den Radius jedes Ringes und den optimalen Cluster- Radius pro Ring zu berechnen. Die Clusterbildungsphase basiert auf einem Fuzzy-Logik-Ansatz für die Clusterkopf (CH)-Auswahl. Die Kooperationsphase zielt darauf ab, einen Zwischenknoten als einen Router zwischen verschiedenen CHs zu definieren. In der Datensammelphase wird die Übertragung von Datenpaketen von Sensorknoten zu ihren entsprechenden CHs als eine Intra-Cluster-Kommunikation definiert, während die Übertragung von Daten von einem CH zu einem anderen CH bis zum Erreichen der Basisstation als eine Inter-Cluster-Kommunikation definiert wird. Die Machbarkeit des entwickelten FEAUC wird durch die Ausarbeitung eines Vergleichs mit ausgewählten referenzierten ungleichen Clustering-Algorithmen unter Berücksichtigung verschiedener Parameter demonstriert, hauptsächlich des Energieverbrauchs, der Batterielebensdauer, der Zeit bis zum Abschalten des ersten Knotens (FND), der Zeit, in der die Hälfte der Knoten offline ist (HND) und der Zeit bis zum letzten Knoten stirbt (LND). Obwohl mit dem entwickelten FEAUC die Lebensdauer des Netzwerks erhöht warden soll, indem die große Last der CH-Aufgaben gleichmäßig auf die übrigen Knoten verteilt wird, stellt die Durchführung des Clustering-Prozesses in jeder Runde eine zusätzliche Belastung dar, die die verbleibende Energie erheblich entziehen kann. Aus diesem Grund wurde das auf FEAUC basierende Protokoll zu einem fehlerto-leranten Algorithmus (FEAUC-FT) weiterentwickelt. Er unterstützt die Fehlerto-leranz durch die Verwendung von Backup-CHs zur Vermeidung des Re-Clustering-Prozesses in bestimmten Runden oder durch den Aufbau weiterer Routing-Pfade im Falle eines Verbindungsausfalls zwischen verschiedenen CHs. Die Validierung des entwickelten FEAUC in realen Szenarien ist durchgeführt worden. Einige Sensorknoten, die mit Batterien betrieben werden, sind in einem kreisförmigen Bereich angeordnet und bilden Cluster. Leistungsbewertungen warden anhand realistischer Szenarien durchgeführt und für einen realen Einsatz unter Verwendung des drahtlosen Low-Power-Sensorknoten panStamp getestet. Zur Vervollständigung früherer Arbeiten wird als Schritt des Proof-of-Concept ein intelligentes Bewässerungssystem mit der Bezeichnung Air-IoT entworfen. Darüber hinaus wird eine IoT-basierte Echtzeit-Sensorknotenarchitektur zur Kontrolle derWassermenge in einigen eingesetzten Knoten eingeführt. Zu diesem Zweck wird ein mit der Cloud verbundenes drahtloses Netzwerk zur Überwachung der Bodenfeuchtigkeit und -temperatur gut konzipiert. Im Allgemeinen ist dieser Schritt unerlässlich, um den vorgeschlagenen ungleichen clusterbasierten Routing-Algorithmus in einem realen Demonstrator zu validieren und zu bewerten.Der vorgeschlagene Prototyp garantiert sowohl Echtzeit-Überwachung als auch zuverlässige und kostengünstige Übertragung zwischen jedem Knoten und der Basisstation.:1 Introduction 2 Theoretical background 3 State of the art of unequal cluster-based routing protocols 4 FEAUC: Fuzzy-based Energy-Aware Unequal Clustering 5 Experimental validation of the developed unequal clustering protocol 6 Real application to specific uses cases 7 Conclusions and future research directions
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Sghaier, Nouha. "Techniques de conservation de l'énergie dans les réseaux de capteurs mobiles : découverte de voisinage et routage." Thesis, Paris Est, 2013. http://www.theses.fr/2013PEST1194/document.
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Le challenge de la consommation d'énergie dans les réseaux de capteurs sans fil constitue un verrou technologique qui reste un problème ouvert encore aujourd'hui. Ces travaux de thèse s'inscrivent dans la problématique de la conservation de l'énergie dans les réseaux de capteurs et s'articulent autour de deux axes. Dans la première partie, nous abordons le dimensionnement des protocoles de découverte de voisinage. Nous proposons deux techniques de dimensionnement de ces protocoles qui visent à optimiser la consommation d'énergie des nœuds capteurs. La première technique, PPM-BM, consiste à dimensionner le protocole de découverte de voisins en fonction du niveau de batterie du nœud. La deuxième approche, ECoND, vise à ajuster la fréquence de découverte de voisins en fonction de la connectivité estimée à chaque instant. Cette technique tire profit des cycles temporels des modèles de mouvement des nœuds. La connectivité est estimée en se basant sur l'historique des rencontres. La découverte de voisins est ajustée en fonction du taux de connectivité estimé. Les résultats enregistrés mettent en évidence l'efficacité de ces deux techniques dans l'optimisation de la consommation d'énergie des nœuds sans affecter les performances de taux de livraison de messages et d'overhead. La deuxième partie de la thèse concerne l'optimisation des performances des réseaux de capteurs en termes de durée de vie. Nous reconsidérons dans cette partie certains protocoles de routage relevant du domaine des réseaux à connectivité intermittente et nous proposons le protocole EXLIOSE qui se base sur la capacité d'énergie résiduelle au niveau des nœuds pour assurer un équilibre énergétique, partager la charge et étendre à la fois la durée de vie des nœuds ainsi que celle du réseauThe challenge of energy consumption in wireless sensor networks is a key issue that remains an open problem. This thesis relates to the problem of energy conservation in sensor networks and is divided into two parts. In the first part, we discuss the design of neighbor discovery protocols. We propose two techniques for modulating these protocols in order to optimize the energy consumption of sensor nodes. The first technique, PPM-BM aims to modulate the neighbor discovery protocol based on the battery level of the node. The second approach ECoND aims to set up the frequency of neighbor discovery based on estimated connectivity. This technique takes advantage of the temporal cycles of nodes' movement patterns. Connectivity is estimated based on encounters' history. A neighbor discovery is set up based on the estimated rate of connectivity. The achieved results demonstrate the effectiveness of these techniques in optimizing the energy consumption of nodes while maintaining acceptable message delivery and overhead rates. In the second part of the thesis, we contribute to the optimization of the performance of sensor networks in terms of network lifetime. We review in this section some routing protocols for networks with intermittent connectivity and we propose EXLIOSE protocol which is based on residual energy to ensure energy-balancing, load sharing and network lifetime extending
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Fröberg, Niklas, and Elias Mehdipoor. "Hur kan installationen av smarta elnätstjänster i bostäder bidra till ökad efterfrågeflexibilitet?" Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-284333.
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I takt med nya innovationer och samhällets fortsatta utveckling och utbredning ökar även elektrifieringen. För att uppnå flera av de miljömål som satts upp av Sveriges riksdag krävs en övergång till ett elsystem byggt på el från förnybara källor. Den ökande elektrifieringen medför inte bara ökade krav på den mängd el som produceras, men även förmågan att transportera den. Den ökade belastningen på elnätet skapar flaskhalsar och kapacitetsbrist i större städer och regioner, vilket gör det svårt att till exempel etablera nya fabriker och bostadsområden vilket bromsar samhällets utveckling. För att lösa denna kapacitetsbrist behövs det svenska stamnätet byggas ut. Detta är dock en relativt långsam process vilket ställer krav på innovativa lösningar som kan avlasta elnätet på kort och lång sikt. En sådan lösning är en ökad efterfrågeflexibilitet, vilket innebär att vissa effektkrävande aktiviteter flyttas till tider på dygnet då elnätet är mindre belastat. Genom att använda sig av smart elnätsteknik kan konsumenter få information om elpriser i realtid och därmed anpassa sin elkonsumtion och dra nytta av lägre elpriser och större tillgång till grön el då topplasten på elnätet är lägre. Syftet med denna studie är att undersöka hur sådana smarta elnätstjänster kan resultera i en ökad efterfrågeflexibilitet i bostäder, och om denna efterfrågeflexibilitet kan hjälpa till att motverka kapacitetsbristen i det svenska elnätet. För att undersöka detta har en litteraturstudie med fokus på beteendeförändringar kopplade till hållbar utveckling samt fyra kvalitativa intervjuer av relevanta aktörer i elbranschen gjorts. Resultaten från litteraturstudien har analyserats i syfte att undersöka huruvida de är applicerbara på smarta elnätstjänster för att uppnå en ökad efterfrågeflexibilitet eller ej. De kvalitativa intervjuerna har summerats och analyserats för att undersöka vilka frågor det råder enighet samt oenighet i bland branschens aktörer. Efter analys samt diskussionen visar studien att smarta elnätstjänster kopplade till bostäders elkonsumtion har potential att uppnå en ökad efterfrågeflexibilitet samt att denna efterfrågeflexibilitet kan bidra till att minska kapacitetsbristen i elnätet. Detta ska dock inte ses som en universell lösning utan en av flera nödvändiga lösningar för att rå på problemet.As innovation and society continue their growth, electrification is increasing rapidly. To achieve several of the environmental goals set by the Swedish Parliament, a transition to an electricity system based on electricity from renewable sources is also required. The increasing electrification entails not only increased demands on the amount of electricity produced, but also the ability to transport it. Increased load on the electricity grid creates bottlenecks and capacity shortages in larger cities and regions, which makes it difficult to establish, among other things, new factories and residential areas, which slows down the development of society. To solve this capacity shortage, the Swedish electrical grid needs to be expanded. However, this is a relatively slow process, which places demands on innovative solutions that can relieve the electricity grid, both short term and long term. Such a solution is an increased demand flexibility, which means that certain power-demanding activities are moved to times of the day when the grid is less congested. By using smart grid technology, consumers can get information about electricity prices in real time and thereby adjust their electricity consumption and benefit from lower electricity prices and greater access to renewable energy when the top load on the electricity grid is lower. The purpose of this study is to investigate how such smart grid services can result in increased demand flexibility in homes, and whether this demand flexibility can help counteract the capacity shortage in the Swedish grid. To investigate this, a literature study focusing on behavioral changes linked to sustainable development, and four qualitative interviews with relevant actors in the energy industry, have been conducted. The results from the literature study have been analyzed to investigate whether or not they are applicable to smart grid services to achieve increased demand flexibility. The qualitative interviews have been summarized and analyzed to examine what issues there is agreement and disagreement in among the industry's players. After analysis and discussion, the study shows that smart grid services linked to residential electricity consumption have the potential to achieve increased demand flexibility and that this demand flexibility can contribute to reducing capacity shortage. However, this should not be seen as a universal solution but as one of several necessary solutions to tackle the problem.
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Eid, Cherrelle. "Towards the design of flexibility management in smart grids : A techno-institutional perspective." Doctoral thesis, KTH, Skolan för elektro- och systemteknik (EES), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214857.
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The European policy focus on smart grids implies their development as an indispensable part of the future power system. However, the definition of a smart grid is broad and vague, and the actual implementation of a smart grid can differ significantly, depending on the stakeholders involved.This work aims to inform policy makers, the electricity industry and researchers about stakeholder interests and the technical complexities involved by presenting smart grids via a techno-institutional framework. This framework takes account of the technical nature of the electricity transport and supply service as well as the institutional nature of electricity markets, stakeholder perspectives and sector regulation. In addition, this work presents potential revenues resulting from flexibility management in smart grids and proposes a way forward for smart grids and flexibility management in Europe.QC 20170925
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Larssen, Marit. "Balancing Costs for Wind Power." Thesis, Norwegian University of Science and Technology, Department of Electrical Power Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9572.
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Nordel is the organisation for the Nordel synchronous system, held by the Nordic Transmission System Operators. In their work to harmonise the Nordic electricity markets they have agreed upon harmonising the Nordic balance management. This will imply three large changes, firstly the settlement of the production balance will be done by a 2-price settlement, (instead of the 1-price settlement in Norway), and secondly there will be a new intraday market for settling the balances after 12- 36 hours and before operating time. Finally the Balance Responsible Parties will have to take their share of the costs for operating the reserves. Paying a penalty through paying more in the regulating market than in the spot market is meant as an incentive for the market to maintain their power balance. This will help the system operator reduce their need to contract and use reserve power and consequently reducing total costs. These new regulations will reduce the net income from producers of wind and other power plants that cannot control their production, like run of river hydro power plants. The market for electricity is currently divided into three consecutive markets. Nord Pool fixes the price the day ahead of operation, followed by the intra-day market Elbas (not in Norway), where power is traded up to one hour before operation, and lastly, the balancing market which helps maintain the balance in the operational hour and settles the costs afterwards. The costs of balancing wind power production in the balancing market (1- price and 2-price) are analysed. Wind series from three Norwegian wind parks have been nominated to the spot market and the deviation settled in the balancing market, by the 1-price settlement as reference and the 2-price settlement. The nominations have been done to three different years; 2004, 2005 and 2006 in Norway, and park A is nominated to 2006 in Sweden and Denmark. It is assumed that the wind power production and the spot and regulating prices are independent of each-other. The resulting change in income with deviation compared to making no prediction error for a 100 MW wind farm is presented. The highest loss compared to making no prediction error is when making a common bid for park A and B (11 677 000 in 2006), followed by the common bid for park A+B with wind series from the second year(8 555 000 in 2006) and park A (7 733 000 in 2006) in Denmark. One of the best ways to integrate large amounts of wind energy is to improve the forecasting methods. In that way the production planning will go easier, and deviations and corresponding costs are reduced. The savings achieved by introducing a prediction tool equals 3 523 000, 4 122 000, 4 921 000 compared to the base case of the corresponding MAEs equal to 39%,30% and 18%. The smoothing effect emerges when nominating geographically spread parks in a group(Holtinnen, 2005). Three parks, that are separated by several 100 km, are nominated by a single BRP. The resulting costs compared to separate nominations are reduced by 31,5 %. This result requires that the wind farms is in the same price area, which they in this case does not. The result is interesting nevertheless as Nordel continuously seek to to invest in transmission capacity in order to create an efficient Nordic market for electricity. The Elbas market is mainly a market to reduce risks. If a deviation should occur it is likely that the best way for balancing it, will be in the regulating market. This is due to the principle of the merit order, which implies that the cheapest regulating power offered is used first. By comparing the data there were quite a few hours were the middle Elbas price was higher than the regulating price. In this sense it might have been wise to wait, although the lower regulating price may also have been a result of more energy being settled in the Elbas market, reducing the volume needed to be settled in the regulating market, and accordingly reducing the price.
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Degrenne, Nicolas. "Gestion de l'énergie des piles à combustible microbiennes." Thesis, Ecully, Ecole centrale de Lyon, 2012. http://www.theses.fr/2012ECDL0032/document.
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Les Piles à Combustible Microbiennes (PCMs) mettent en œuvre le métabolisme de micro-organismes et utilisent de la matière organique pour générer de l’énergie électrique. Les applications potentielles incluent le traitement de l’eau autonome en énergie, les bio-batteries, et le grappillage d’énergie ambiante. Les PCMs sont des équipements basse-tension et basse-puissance dont le comportement est influencé par la vitesse à laquelle l’énergie électrique est récupérée. Dans cette thèse, on étudie des méthodes pour récupérer l’énergie électrique de façon efficace. La tension à laquelle l’énergie est récupérée des PCMs influence leur fonctionnement et leurs performances électriques. La puissance délivrée est maximum pour une tension spécifique (environ 1/3 de la tension en circuit-ouvert). Les PCMs peuvent être testées à ce point en utilisant une charge contrôlée automatiquement qui inclut un algorithme de recherche de puissance maximale. Un tel outil a été utilisé pour évaluer la puissance maximum, la vitesse de consommation du combustible, le rendement Coulombic et le rendement de conversion de 10 PCMs à chambre unique de 1.3 L construites de façon similaire. Bien que d’autres choix structurels et opératoires peuvent permettre d’améliorer ces performances, ces résultats ont étudié pour la première fois les performances des PCMs en condition de production d’énergie de point de puissance maximal et testé les PCMs avec des conditions de récupération d’énergie réalistes. Récupérer un maximum d’énergie des PCMs est la ligne directrice de ce rapport. C’est rendu possible par des circuits dédiés de gestion de l’énergie qui embarquent un contrôle contre-réactif pour réguler la tension des PCMs à une valeur de référence qui est égale à une fraction de leur tension en circuit ouvert. Deux scénarios typiques sont développés dans la suite. Une application critique des PCMs concerne le grappillage autonome de petites énergies, pour alimenter des équipements électroniques basse-puissance (e.g. capteurs sans fil). Dans ce cas, les contraintes basse-puissance et basse-tension imposées par les PCMs nécessitent des fonctionnalités de démarrage autonomes. L’oscillateur d’Armstrong, composé d’inductances couplées à fort rapport d’enroulement et d’un interrupteur normalement-fermé permet d’élever des tensions de façon autonome à partir de sources basse-tension continue comme les PCMs. Ce circuit a été associé à des convertisseurs d’électronique de puissance AC/DC et DC/DC pour réaliser respectivement un élévateur-de-tension et une unité de gestion de l’énergie (UGE) auto-démarrante basée sur une architecture flyback. La première est adaptée pour les puissances inférieures à 1mW, alors que la seconde peut être dimensionnée pour des niveaux de puissance de quelques mW et permet de mettre en œuvre une commande qui recherche le point de puissance maximale du générateur. Une seconde application d’intérêt concerne le cas où de l’énergie est récupérée depuis plusieurs PCMs. L’association série peut être utilisée pour élever la tension de sortie mais elle peut avoir des conséquences négatives en terme de performances à cause des non-uniformités entre cellules. Cet aspect peut être résolu avec des circuits d’équilibrage de tension. Trois de ces circuits ont été analysés et évalués. Le circuit “complete disconnection” déconnecte une cellule défectueuse de l’association pour s’assurer qu’elle ne diminue pas le rendement global. Le circuit “switched-capacitor” transfère de l’énergie depuis les MFCs fortes vers les faibles pour équilibrer les tensions de toutes les cellules de l’association. Le circuit “switched-MFCs” connecte les PCMs en parallèle et en série de façon alternée. Chacune des trois méthodes peut être mise en œuvre à bas prix et à haut rendement, la plus efficace étant la “switchedcapacitor”qui permet de récupérer plus de 85% de la puissance maximum idéale d’une association très largement non uniformeMicrobial fuel cells (MFCs) harness the metabolism of micro-organisms and utilize organic matter to generate electrical energy. They are interesting because they accept a wide range of organic matter as a fuel. Potential applications include autonomous wastewater treatment, bio-batteries, and ambient energy scavenging. MFCs are low-voltage, low-power devices that are influenced by the rate at which electrical energy is harvested at their output. In this thesis, we study methods to harvest electrical energy efficiently. The voltage at which energy is harvested from MFCs influences their operation and electrical performance. The output power is maximum for a certain voltage value (approx. 1/3rd the open-circuit voltage). This noteworthy operating point is favorable in some applications where MFCs are used as a power supply. MFCs can be tested at this point using an automatic load adjuster which includes a maximum power point tracking algorithm. Such a tool was used to evaluate the maximum power, the fuel consumption rate, the Coulombic efficiency and the energy conversion efficiency of ten similarly built 1.3 L single-chamber MFCs. Although structural and operating condition choices will lead to improved performance, these results investigate for the first time the performance of MFCs in continuous maximum power point condition and characterize MFCs in realistic energy harvesting conditions. Harvesting energy at maximum power point is the main thread of the manuscript. This is made possible with dedicated energy processing circuits embedding control feedback to regulate the MFC voltage to a fraction of its open-circuit voltage. Two typical scenarios are developed as outlined below. One critical application concerns autonomous low-power energy scavenging, to supply remote low-power electronic devices (e.g. wireless sensors). In this case, the low-power and low-voltage constraints imposed by MFCs require dedicated self start-up features. The Armstrong oscillator, composed of high turn-ratio coupled inductors and of a normally-on switch, permits to autonomously step-up voltages from a low DC source like MFCs. Although the circuit requires few components, its operation is not trivial because it partly relies on the parasitic elements of the inductors and the switch. Proper sizing of the inductors enables an optimized operation. This circuit can be associated with power electronic AC/DCand DC/DC converters to realize a voltage-lifter and a fly back-based self-starting Power Management Unit (PMU) respectively. The former is suitable for powering levels below 1mW, while the latter can be scaled for power levels of a few units of mW and facilitates implementation of maximum power point control. A second application of interest concerns the case where energy is harvested from several MFCs.Serial association can be used to step-up voltage but may lead to detrimental consequences in terms of performances because of hydraulic couplings between MFCs sharing the same electrolyte (e.g. if the MFCs are running in continuous flow) or because of electrical non-uniformities between cells. Whereas the former issue can be addressed with galvanically insulated PMUs, the latter can be solved with voltagebalancing circuits. Three of these latter circuits were analyzed and evaluated. The “complete disconnection” circuit isolates a faulty cell from the configuration to ensure it does not impede the overall efficiency. The “switched-capacitor” circuit transfers energy from the strong to the weak MFCs to equilibrate the voltages of the individual cells in the stack. The “switched-MFC” circuit alternatively connects MFCs in parallel and in series. Each of the three methods can be implemented at low-cost and at high efficiency, the most efficient one being the “switched-capacitor”, that permits to harvest more that 85% of the ideal maximum energy of a strongly-non-uniform MFC association
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Sapountzis, Nikolaos. "Optimisation au niveau réseau dans le cadre des réseaux hétérogènes nouvelle génération." Electronic Thesis or Diss., Paris, ENST, 2016. http://www.theses.fr/2016ENST0082.
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Depuis 2016, il est bien connu que les réseaux mobiles dominent nos vies. Nous utilisons nos téléphones cellulaires pour presque tout: du réseautage social au streaming, à la recherche de logement ou pour les transactions bancaires. Néanmoins, il semble que les opérateurs ne comprennent pas cette domination, puisque leurs réseaux sont constitués de nœuds qui: (i) subissent d'énormes fluctuations de charge, (ii) gaspillent leurs ressources, et (iii) sont accusés d'être tueurs d'énergie majeurs. Ces inconvénients nuisent à load-balancing, efficacité spectrale et énergétique, respectivement. L'objectif de cette dissertation est d'étudier attentivement ces gains d'efficacité et d'établir un bon “trade off” entre eux pour les futurs réseaux hétérogènes 5G mobiles. Dans cette direction, nous nous concentrons tout d'abord sur (i) l'utilisateur et la différenciation du trafic, émergeant des applications de type MTC et IoT, et (ii) du RAN. Plus précisément, nous réalisons une modélisation, une analyse de performance et une optimisation appropriées pour une famille d'objectifs, en utilisant des outils provenant principalement de l'optimisation (non) convexe, de la probabilité et de la théorie des files d'attente. Après, nous soulignons que l'optimisation des fonctionnalités RAN, suivie d'un formidable « capacity crunch », posent de sérieuses contraintes dans le réseau de backhaul en le faisant apparaître comme un goulet d'étranglement de performance. Ainsi, nous incluons (iii) dans notre cadre: des contraintes de capacité de liaison de backhaul dans des topologies génériques. Enfin, nous considérons le problème de l'allocation TDD dans les réseaux d'accès et de backhaulBy 2016, it is well-known that mobile networking has dominated our lives. We use our mobile cell phones for almost everything: from social networking to streaming, finding accommodation or banking. Nevertheless, it seems that operators have not understood yet this domination, since their networks consist of nodes that: (i) suffer from enormous load fluctuations, (ii) waste their resources, and (iii) are blamed to be a major energy-killer worldwide. Such shortcomings hurt: load-balancing, spectral and energy efficiency, respectively. The goal of this dissertation is to carefully study these efficiencies and achieve a good trade-off between them for future mobile 5G heterogeneous networks (HetNets). Towards this direction, we firstly focus on (i) the user and traffic differentiation, emerging from the MTC and IoT applications, and (ii) the RAN. Specifically, we perform appropriate modeling, performance analysis and optimization for a family of objectives, using tools mostly coming from (non) convex optimization, probability and queueing theory. Our initial consideration is on network-layer optimizations (e.g. studying the user association problem). Then, we analytically show that cross-layer optimization is key for the success of future HetNets, as one needs to jointly study other problems coming from the layers below (e.g. the TDD allocation problem from the MAC, or the cross-interference management from the PHY) to avoid performance degradation. Finally, we add the backhaul network into our framework, and consider additional constraints related to the backhaul capacity, backhaul topology, as well as the problem of backhaul TDD allocation