The topic of voltage optimization has been of recent interest to many researchers and is being considered by many utilities for implementation in their Energy Control Centers. Much of the past research has utilized linear programming incremental models or strictly gradient techniques. This research combines both linear programming (LP) and generalized reduced gradient techniques (GRG) for voltage optimization. The result provides most of the advantages of both LP and gradient techniques. Further, the research incorporates important considerations for implementation in an Energy Control Center. / Ph. D.

Power dissipation has become a major concern for IC designers. Various low power design techniques have been developed for synchronous circuits. Asynchronous circuits, however. have gained more interests recently due to their benefits in lower noise, easy timing control, etc. But few publications on energy reduction techniques for asynchronous logic are available. Power awareness indicates the ability of the system power to scale with changing conditions and quality requirements. Scalability is an important figure-of-merit since it allows the end user to implement operational policy. just like the user of mobile multimedia equipment needs to select between better quality and longer battery operation time. This dissertation discusses power/energy optimization and performs analysis on both synchronous and asynchronous logic. The major contributions of this dissertation include: 1 ) A 2-Dimensional Pipeline Gating technique for synchronous pipelined circuits to improve their power awareness has been proposed. This technique gates the corresponding clock lines connected to registers in both vertical direction (the data flow direction) and horizontal direction (registers within each pipeline stage) based on current input precision. 2) Two energy reduction techniques, Signal Bypassing & Insertion and Zero Insertion. have been developed for NCL circuits. Both techniques use Nulls to replace redundant Data 0's based on current input precision in order to reduce the switching activity while Signal Bypassing & Insertion is for non-pipelined NCI, circuits and Zero Insertion is for pipelined counterparts. A dynamic active-bit detection scheme is also developed as an expansion. 3) Two energy estimation techniques, Equivalent Inverter Modeling based on Input Mapping in transistor-level and Switching Activity Modeling in gate-level, have been proposed. The former one is for CMOS gates with feedbacks and the latter one is for NCL circuits.

Computing system power consumption is a concern as it has financial and environmental implications. These concerns will increase in the future due to the current trends in data growth, information availability requirements, and increases in the cost of energy. Data growth is compounded daily because of the accessibility of portable devices, increased connectivity to the Internet, and a trend toward storing information electronically. These three factors also result in an increased demand for the data to be available for access at all times which results in more electronic devices requiring power. As more electricity is required the overall cost of energy increases due to demand and limited resource availability. The environment also suffers as most electricity is generated from fossil fuels which increase emission of carbon dioxide into the atmosphere. In order to reduce the amount of energy required while maintaining data availability researchers have focused on changing how data is accessed from hard drives. Hard drives have been found to consume 10 to 86 percent of a system's energy. Through changing the way data is accessed by implementing multi speed hard drives, algorithms that prefetch, cache, and batch data requests, or by implementing flash drive caches researchers have been able to reduce the energy required from hard drive operation. However, these approaches often result in reduced I/O performance or reduced data availability. This dissertation provides a new method of reducing hard drive energy consumption by implementing a prefetching technique that predicts a chain of future requests based upon previous request observations. The files to be prefetched are given to a caching system which uses a flash memory device for caching. This caching system implements energy sensitive algorithms to optimize the value of files stored in the flash memory device. Through prefetching files the hard drive on a system can be placed in a low power sleep state. This results in reduced power consumption while providing high I/O performance and data availability. Analysis of simulator results confirmed that this new method increased I/O performance and data availability over previous studies while also providing a higher level of energy savings. Out of 30 scenarios, the new method displayed better energy savings in 26 scenarios and better performance in all 30 scenarios over previous studies. The new method also displayed it could achieve results of 50.9 percent less time and 34.6 percent less energy for a workload over previous methodologies.

Orientador: Fernando Pinhabel Marafão / Co-orientador: Pedro Miguel Rebelo Resende / Banca: Roberto Wagner Lourenço / Banca: Diego Colon / Resumo: Esse trabalho apresenta um estudo sobre o cenário da utilização da energia elétrica no Brasil, considerando dados sobre a oferta e a demanda, bem como sobre as principais fontes envolvidas na matriz elétrica do país. Sabe-se que quase 70% da eletricidade consumida no país é proveniente de usinas hidrelétricas, porém com a falta de chuvas dentro da normalidade, que ocorre desde 2013, tem sido necessário comprovar a oferta com a produção termelétrica, fazendo aumentar o custo de geração que é repassado para o consumidor. Também são apresentados nesse trabalho, o potencial de geração das principais fontes de energia renováveis no país, com análise de custos de instalação, incentivos existentes para o crescimento dessas fontes e discussões sobre a necessidade da inserção afetiva das mesmas na matriz elétrica brasileira, visando atender a crescente demanda. De posse do potencial energético através de fontes renováveis e baseando-se em experiências internacionais, particularmente através do estudo de caso da China e da Alemanha, o trabalho surge ainda possíveis medidas para o crescimento da utilização de energia solar, eólica e outras, na geração de energia elétrica, fator considerado essencial para o crescimento econômico e sustentável do país / Abstract: The main goal of this work is to study and to map the electrical energy scenario in Brazil, considering the supply, demand and the different primary energy sources in the country. It is well skown that almost 70% of the electrical energy consumed in Brasil comes from hydroelectric plants, however, since 2013 and due to the lack of abundant rain for keeping the hydroelectric normal parameters, it has become necessary to apply thermoelectric plants, consequently increasing the energy costs. For this reason, different energy sources are studied in this work as alternatives for the current generation system in Brazil, considering the different aspects such as: installation costs, normative and financial incentives and future demand. Furthermore, to better understand the potential of renewable energy in Brazil, some comparisons using the German and Chinese scenarios have been done, allowing to suggest short and long term actions for increasing the sustainable energy market, pointing out solar and wind power sources as essential for the economic and environmental development / Mestre

Wireless Sensor Networks (WSNs) have enticed a strong attention in the research community due to the broad range of applications and services they support. WSNs are composed of intelligent sensor nodes that have the capabilities to monitor different types of environmental phenomena or critical activities. Sensor nodes operate under stringent requirements of scarce power resources, limited storage capacities, limited processing capabilities, and hostile environmental surroundings. However, conserving sensor nodes’ power resources is the top priority requirement in the design of a WSN as it has a direct impact on its lifetime. The IEEE 802.15.4 standard defines a set of specifications for both the PHY layer and the MAC sub-layer that abide by the distinguished requirements of WSNs. The standard’s MAC protocol employs an intelligent backoff algorithm, called the Binary Exponent Backoff (BEB), that minimizes the drainage of power in these networks. In this thesis we present an in-depth study of the IEEE 802.15.4 MAC protocol to highlight both its strong and weak aspects. We show that we have enticing opportunities to improve the performance of this protocol in the context of WSNs. We propose three new backoff algorithms, namely, the Standby-BEB (SB-BEB), the Adaptive Backoff Algorithm (ABA), and the Priority-Based BEB (PB-BEB), to replace the standard BEB. The main contribution of the thesis is that it develops a new design concept that drives the design of efficient backoff algorithms for the IEEE 802.15.4-based WSNs. The concept dictates that controlling the algorithms parameters probabilistically has a direct impact on enhancing the backoff algorithm’s performance. We provide detailed discrete-time Markov-based models (for AB-BEB and ABA) and extensive simulation studies (for the three algorithms) to prove the superiority of our new algorithms over the standard BEB.

Wireless data broadcast is an efficient way to disseminate digital information to clients equipped with mobile devices. It allows a huge number of the mobile clients simultaneously access data at anytime and anywhere in the wireless environments. Applications using wireless data broadcast to disseminate information include accessing stock activities and traffic conditions. Using index technologies on the broadcast file, i.e., selective tuning, can reduce a lot of energy consumption of the mobile devices without significantly increasing client waiting time. Most of the research work for selective tuning assumes that each data item broadcast on the wireless channel is fairly evenly accessed by mobile clients. In real-life applications, more popular data may be frequently accessed by clients than less popular ones, i.e., skewed access patterns. In this dissertation, to support efficiently selective tuning with skewed access patterns in the single-channel wireless environments, we first propose a skewed distributed index, SDI, on the uniform data broadcast, on which each data item is broadcast once in a broadcast cycle. Second, we propose a skewed index, SI, on the nonuniform data broadcast, on which a few popular data items are broadcast more frequently in a broadcast cycle than the others. The first proposed algorithm, SDI, considers the access probabilities of data items and the replication of index nodes. The proposed algorithm traverses a balanced tree to determine whether an index node should be replicated by considering the access probability of its child node. In our performance analysis and simulation results, we have shown that our proposed algorithm outperforms the variant-fanout tree index and the distributed index. The second proposed algorithm, SI, applies Acharya et al.'s Broadcast Disks to generate a broadcast program, in which the popular data items are broadcast more times than the others, in order to reduce client waiting time. Moreover, the proposed algorithm builds a skewed tree for these data items and allocates index nodes for the popular data items more times than those for the less popular ones in a broadcast cycle. From our performance analysis and simulation results, we have shown that our proposed SI outperforms the flexible index and the flexible distributed index.

Wireless Sensor Networks (WSNs) have enticed a strong attention in the research community due to the broad range of applications and services they support. WSNs are composed of intelligent sensor nodes that have the capabilities to monitor different types of environmental phenomena or critical activities. Sensor nodes operate under stringent requirements of scarce power resources, limited storage capacities, limited processing capabilities, and hostile environmental surroundings. However, conserving sensor nodes’ power resources is the top priority requirement in the design of a WSN as it has a direct impact on its lifetime. The IEEE 802.15.4 standard defines a set of specifications for both the PHY layer and the MAC sub-layer that abide by the distinguished requirements of WSNs. The standard’s MAC protocol employs an intelligent backoff algorithm, called the Binary Exponent Backoff (BEB), that minimizes the drainage of power in these networks. In this thesis we present an in-depth study of the IEEE 802.15.4 MAC protocol to highlight both its strong and weak aspects. We show that we have enticing opportunities to improve the performance of this protocol in the context of WSNs. We propose three new backoff algorithms, namely, the Standby-BEB (SB-BEB), the Adaptive Backoff Algorithm (ABA), and the Priority-Based BEB (PB-BEB), to replace the standard BEB. The main contribution of the thesis is that it develops a new design concept that drives the design of efficient backoff algorithms for the IEEE 802.15.4-based WSNs. The concept dictates that controlling the algorithms parameters probabilistically has a direct impact on enhancing the backoff algorithm’s performance. We provide detailed discrete-time Markov-based models (for AB-BEB and ABA) and extensive simulation studies (for the three algorithms) to prove the superiority of our new algorithms over the standard BEB.

Made available in DSpace on 2016-01-13T13:27:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-06-03. Added 1 bitstream(s) on 2016-01-13T13:32:54Z : No. of bitstreams: 1 000852309.pdf: 2355883 bytes, checksum: c45349f76ac1ed9a2794bd2e68f235d5 (MD5) / Esse trabalho apresenta um estudo sobre o cenário da utilização da energia elétrica no Brasil, considerando dados sobre a oferta e a demanda, bem como sobre as principais fontes envolvidas na matriz elétrica do país. Sabe-se que quase 70% da eletricidade consumida no país é proveniente de usinas hidrelétricas, porém com a falta de chuvas dentro da normalidade, que ocorre desde 2013, tem sido necessário comprovar a oferta com a produção termelétrica, fazendo aumentar o custo de geração que é repassado para o consumidor. Também são apresentados nesse trabalho, o potencial de geração das principais fontes de energia renováveis no país, com análise de custos de instalação, incentivos existentes para o crescimento dessas fontes e discussões sobre a necessidade da inserção afetiva das mesmas na matriz elétrica brasileira, visando atender a crescente demanda. De posse do potencial energético através de fontes renováveis e baseando-se em experiências internacionais, particularmente através do estudo de caso da China e da Alemanha, o trabalho surge ainda possíveis medidas para o crescimento da utilização de energia solar, eólica e outras, na geração de energia elétrica, fator considerado essencial para o crescimento econômico e sustentável do país / The main goal of this work is to study and to map the electrical energy scenario in Brazil, considering the supply, demand and the different primary energy sources in the country. It is well skown that almost 70% of the electrical energy consumed in Brasil comes from hydroelectric plants, however, since 2013 and due to the lack of abundant rain for keeping the hydroelectric normal parameters, it has become necessary to apply thermoelectric plants, consequently increasing the energy costs. For this reason, different energy sources are studied in this work as alternatives for the current generation system in Brazil, considering the different aspects such as: installation costs, normative and financial incentives and future demand. Furthermore, to better understand the potential of renewable energy in Brazil, some comparisons using the German and Chinese scenarios have been done, allowing to suggest short and long term actions for increasing the sustainable energy market, pointing out solar and wind power sources as essential for the economic and environmental development

CAPES, FINEP, SETI e Fundação Araucária. / Neste trabalho é abordado o aumento da eficiência no acionamento de motores de indução através de técnicas de controle que utilizam um modelo de perdas e uma estrutura adaptativa. Inicialmente é apresentada a revisão da literatura com os principais controladores de eficiência energética. Também são apresentados os modelos elétrico e mecânico do motor para simulação do controle por campo orientado indireto (IFOC – Indirect Field Oriented Control) composto por controlador de velocidade, fluxo e corrente. A identificação das fontes de perdas é utilizada como auxílio no desenvolvimento do controlador de eficiência em conjunto com controladores de velocidade e fluxo. Os métodos de aumento de eficiência energética do motor de indução utilizando por busca recursiva (SC– Search Control) e controle por modelo de perdas (LMC– Loss-Model-Based Control) são descritos, simulados e implementados. O SC é implementado com passo de busca adaptativo e o LMC através de uma curva padrão de fluxo ótimo baseado na corrente estatórica. O SC converge para a mínima potência de entrada, porém tem resposta lenta de 5s em transitórios. O LMC possui resposta rápida de 1s, mas também possui dependência a variação paramétrica. Através da combinação do SC com o LMC, um Controlador Híbrido Adaptativo de Eficiência (HAEC) é proposto. Este controlador possui rápida convergência de 1s em transitórios e baixa sensibilidade a variações paramétricas. Para verificação experimental dos controladores de eficiência, foi projetado uma plataforma de acionamento composta por conversor estático trifásico CA/CC/CA com modulação PWM Space Vector comandado por processador digital de sinais. Os resultados experimentais obtidos apresentaram redução no consumo de energia, quando comparados com o acionamento com fluxo constante, de 29,7% com SC, 39,9% com o LMC e 49,4% com o HAEC. Isso demonstra a viabilidade técnica do HAEC. / This work approached the increased efficiency of induction motor drives using control techniques through a loss model and an adaptive structure. The review is presented with mainly energy efficiency controllers. Also, it are presented the electrical and mechanical models for motor control simulation with indirect field oriented (IFOC - Indirect Field Oriented Control) composed for speed, current and flux controllers. The identification of losses sources is used to development of efficiency controller with speed and flow. The methods of increasing energy efficiency of induction motor using a recursive search (SCSearch Control) and Loss-Model-based Controller (LMC) are presented, simulated and implemented. The SC is implemented with adaptive search step and the LMC by an optimal flux standard curve based on stator current. The SC converges to minimum input power, but it has slow response of 5s in transients. The LMC has quick response of 1s, but also it has dependency on parametric variation. Through the combination of SC and LMC, a Hybrid Adaptive Efficiency Controller (HAEC) is proposed. This controller has fast convergence of 1s in transitory and low sensibility with parameter variations. To implement the efficiency controllers, it was developed a platform composed by three-phase AC / CC / AC static converter with Space Vector Pulse Width Modulation controlled by a digital signal processor. Experimental results present an energy consumption reduction compared with constant flux drive of 29.7% for SC, 39.9% for LMC and 49.4% with HAEC. These results had shown the viability for HAEC project.

Orientador: José Manoel Balthazar / Banca: Angelo Marcelo Tusset / Banca: Clivaldo de Oliveira / Banca: Max Mauro Dias Santos / Banca: Atila Madureira Bueno / Resumo: Recentemente, o interesse e a pesquisa de coleta de energia têm aumentado substancialmente no meio técnico-científico. Com a grande demanda mundial por energia elétrica, muitos pesquisadores, no Brasil e no Mundo, têm concentrado seus esforços na busca de novas fontes de energia. No processo de coleta de energia, a energia elétrica é obtida através da conversão de energia mecânica criada por uma fonte de vibração do meio ambiente através de um transdutor. Fontes de vibração do meio ambiente podem ser causadas em estruturas através do movimento de veículos, ondas do mar e até o deslocamento de pessoas. Com isso, este trabalho tem como objetivo estudar a coleta de energia utilizando um dispositivo MagLev não-linear excitado externamente em sua base por uma fonte não ideal. A metodologia empregada para a realização das análises deste trabalho foram: utilizar o método de múltiplas escalas para buscar as melhores configurações dos parâmetros e realização de simulações numéricas utilizando o método de Runge-Kutta de quarta e quinta ordem com passo variável buscando otimizar a coleta de energia através da variação de parâmetros, diagramas de bifurcação, expoente de lyapunov, históricos no tempo entre outros. Em geral serão feitas duas comparações entre o resultado numérico e o resultado obtido analiticamente pelo método das múltiplas escalas, bem como a melhor configuração de parâmetros para uma melhor coleta de energia / Abstract: Recently interest and energy harvesting research have increased substantially in the technical-scientific community. With the high global demand for electricity, many researchers in Brazil an the world, have concentrated their efforts in the search for new energy sources. Energy collection process, electrial energy is obtained by converting mechanical energy created by a vibration source of the environment through a transducer, environmental sources of vibration may be caused in structures by the movements of cars, train, sea waves, and even the movement of people. Thus, this work aims to study the collection of energy using and excited nonlinear MagLev device externally at its base by a non ideal source. The employed methodology for the carrying out the anlyzes of this study were to use the method of multiple scales to find the parameter setting and performing numerical simulations using the Runga-Kutta method of fourth and fifth order with variable step in order to optimize the collection energy by variation of parameters, bifurcation diagrams, exponent lyapunov, historical time among others. In general two comparison are made between the numerical result and the analytical result obtained by the method of multiple scales, and the best parameter setting for improved energy harvesting / Doutor