Dissertations / Theses on the topic 'Power and Energy'

Tesis para optar al grado de Magíster en Administración
Eduardo Andres Erices Muñoz [Parte I Análisis estratégico y de mercado], Cristian Patricio Torres Rojas [Parte II Análisis organizativo-financiero]
Autores no autorizan el acceso a texto completo de su documento
La necesidad de aumentar la capacidad instalada de la matriz energética del país es un tema que en la última década se ha instalado en la agenda nacional, dado que el crecimiento económico de Chile implica un mayor consumo eléctrico. A su vez, la estrechez energética se ve representada con mayor profundidad en la industria de la minería, especialmente en el norte grande de Chile. El sector minero, además de ser el principal consumidor de energía eléctrica del país, ha experimentado desde el año 2000 una caída sostenida en su productividad, entre otros factores, por los mayores consumos y costos de la energía eléctrica, enfrentando actualmente uno de los precios más altos de América Latina1. Dado lo anterior, el Gobierno está asumiendo un rol más activo, definiendo una Agenda de Energía que incluye como uno de sus ejes el compromiso que un 45% de la capacidad eléctrica que se instalará en el país hasta el año 2025 sean energías renovables no convencionales (ERNC) y, de esta forma, cumplir con la meta de la Ley 20/25 de ingresar a la matriz energética un 20% de ERNC para dicho año. En este sentido, la energía fotovoltaica es una alternativa técnicamente viable para cubrir el consumo eléctrico, principalmente en el norte grande del país, dado que posee un importantísimo potencial solar. El propósito del presente plan de negocios es evaluar la factibilidad económica y financiera de ingresar al negocio de las energías renovables no convencionales, de una manera no convencional. Más allá de este juego de palabras, dado que la mayoría de los proyectos de generación de energía limpia se basan en el modelo de negocios tradicional, o sea generando e inyectando energía al sistema y transando los precios en el mercado spot, la oportunidad de negocio se visualiza en vender directamente la energía a la industria minera, sin intermediarios ni costos de transmisión relevantes. La industria eléctrica nacional está dividida en tres segmentos: generación, transmisión y distribución de energía eléctrica. Las actividades de transmisión y distribución tienen el carácter de monopolio natural. El sector de generación opera en condiciones de competencia, no obstante se caracteriza por ser un mercado altamente concentrado. Asimismo, existen cuatro sistemas eléctricos siendo los dos más importantes el SING (Sistema Interconectado del Norte Grande) y el SIC (Sistema Interconectado Central). La matriz energética del SING se alimenta en un 95% de fuentes térmicas (carbón, diésel, gas natural). En cuanto al desarrollo de proyectos ERNC, a pesar que el país posee condiciones naturales favorables para las energías solar y eólica, recién en el año 2014 se observó un “despegue” de las ERNC en Chile, materializándose proyectos con una capacidad instalada de casi 1.000 MW. Además, a nivel mundial la curva de aprendizaje en el costo de fabricación y operación de la tecnología solar fotovoltaica, ha permitido alcanzar precios competitivos respecto a las fuentes convencionales de energía. El mercado objetivo se concentra en el segmento de generación, a través del suministro eléctrico en base a energías renovables no convencionales, específicamente solar tipo fotovoltaica, para las empresas mineras (cobre) ubicadas en las regiones de Tarapacá y Antofagasta, ya que reúnen las condiciones de vida útil de la faena minera y disponibilidad de terrenos, de acuerdo a la propuesta de valor del proyecto. El modelo de negocios consiste en satisfacer parte de la demanda de energía eléctrica de las empresas mineras señaladas en el párrafo anterior, por medio de una planta solar fotovoltaica de 3 MW de potencia instalada y a través de un contrato de suministro tipo PPA (Power Purchase Agreement) a 20 años. La ventaja competitiva consiste en ofrecer una tarifa estable durante el período del contrato más baja que su tarifa actual en base a generación convencional, lo cual permitirá al cliente capturar y proyectar el ahorro en sus costos operativos. Además, la propuesta tiene la característica que la planta se construirá in-situ, aprovechando la superficie disponible en la faena minera, generando valor compartido en la economía de escala por el costo del terreno y línea de transmisión y conexión eléctrica. La operación y mantenimiento de la planta fotovoltaica estará a cargo de nuestra empresa. Para el desarrollo del negocio, dado que implica montos de inversión relevantes (USD 5,6 millones para cada planta) y se requiere de un respaldo tecnológico y logístico para realizar ese tipo de proyectos, se creará una Unidad Estratégica de Negocio (UEN) denominada “SUN POWER ENERGY” (SPE), bajo la estructura organizacional de E.CL S.A., una de las empresas principales que operan en el SING. Finalmente, en la evaluación financiera se contempla la ejecución de tres plantas solares dentro de los primeros seis años, con un total de aporte de capital requerido de USD 10 millones. Se ha considerado el apalancamiento financiero del proyecto, mediante la obtención de préstamos bancarios por USD 7,8 millones. Como resultado, través del valor actual de los flujos de caja libres descontados a una tasa del 7,5%, se obtiene un valor de la empresa sin deuda de USD 52.382, con una TIR del 7,5% y un periodo de recuperación de la inversión (payback) de 12 años. La TIR del inversionista alcanza al 7,9% con un VAN ajustado de USD 576.161.

The topic of renewable energy is an evergreen subject, especially, in a world dominated by fossil fuels. Renewable energy is widely discussed in the contemporary world because it is unlimited, which means it’s sustainable and does not emit greenhouse gasses that are harmful to the environment and human life. A classic example of renewable energy is wave energy.

La creixent demanda energètica, l’esgotament dels combustibles fòssils i l’augment de l’escalfament global a causa de l’emissió de carboni ha donat lloc a la necessitat d’un sistema energètic alternatiu, global i respectuós amb el medi ambient. L’energia solar es considera una de les formes d’energia més inesgotables d’aquest univers, però té el problema de la baixa eficiència a causa de les diferents condicions ambientals. El panell solar presenta un comportament no lineal en condicions climàtiques reals i la potència de sortida fluctua amb la variació de la irradiació solar i la temperatura. El canvi de les condicions meteorològiques i el comportament no lineal dels sistemes fotovoltaics suposen un repte en el seguiment de diferents PowerPoint màxims. Per tant, per extreure i lliurar contínuament la màxima potència possible del sistema fotovoltaic, en determinades condicions ambientals, s’ha de formular l’estratègia de control de seguiment del punt de potència màxima (MPPT) que funcioni contínuament el sistema fotovoltaic al seu MPP. Es necessita un controlador no lineal robust per garantir el MPPT mitjançant la manipulació de les línies no lineals d’un sistema i el fa robust contra les condicions ambientals canviants. El control de mode lliscant (SMC) s’utilitza àmpliament en sistemes de control no lineals i s’ha implementat en sistemes fotovoltaics (PVC) per rastrejar MPP. SMC és robust contra les pertorbacions, les incerteses del model i les variacions paramètriques. Representa fenòmens indesitjables com el xerramec, inherent al fet que provoca pèrdues d’energia i calor. En aquesta tesi, en primer lloc, es formula un controlador SMC d’ordre sencer per extreure la màxima potència d’un sistema solar fotovoltaic en condicions climàtiques variables que utilitzen l’esquema MPPT de pertorbació i observació (P \ & O) del sistema fotovoltaic autònom proposat. El sistema proposat consta de dos esquemes de bucles, a saber, el bucle de cerca i el bucle de seguiment. P&O MPPT s’utilitza al bucle de cerca per generar el senyal de referència i un controlador SMC de seguiment s’utilitza a l’altre bucle per extreure la màxima potència fotovoltaica. El sistema fotovoltaic es connecta amb la càrrega mitjançant el convertidor d’alimentació electrònic DC-DC de potència. Primer es deriva un model matemàtic del convertidor d’augment i, basat en el model derivat, es formula un SMC per controlar els impulsos de la porta del commutador del convertidor d’augment. L’estabilitat del sistema de bucle tancat es verifica mitjançant el teorema d’estabilitat de Lyapunov. L’esquema de control proposat es prova amb diferents nivells d’irradiació i els resultats de la simulació es comparen amb el controlador de derivades integrals proporcionals clàssiques (PID). El SMC clàssic representa fenòmens indesitjables com el xerramec, inherent al fet que provoca pèrdues d’energia i calor. A la següent part d’aquesta tesi, es discuteix el disseny del controlador de mode lliscant adaptatiu (ASMC) per al sistema fotovoltaic proposat. El control adoptat s’executa mitjançant un ASMC i la millora s’actualitza mitjançant un algorisme d’optimització MPPT de mètode de cerca de patrons millorats (IPSM). S’utilitza un MPPT IPSM per generar la tensió de referència per tal de comandar el controlador ASMC subjacent. S’ha dut a terme una comparació amb altres dos algoritmes d’optimització, a saber, Perturb \ & Observe (P&O) i Particle Swarm Optimization (PSO) amb IPSM per MPPT. Com a estratègia no lineal, l’estabilitat del controlador adaptatiu es garanteix mitjançant la realització d’una anàlisi de Lyapunov. El rendiment de les arquitectures de control proposades es valida comparant les propostes amb la del conegut i àmpliament utilitzat controlador PID.
La creciente demanda de energía, el agotamiento de los combustibles fósiles y el aumento del calentamiento global debido a la emisión de carbono han hecho surgir la necesidad de un sistema energético alternativo, de eficiencia general y respetuoso con el medio ambiente. La energía solar se considera una de las formas de energía más inagotables de este universo, pero tiene el problema de la baja eficiencia debido a las diferentes condiciones ambientales. El panel solar exhibe un comportamiento no lineal en condiciones climáticas reales y la potencia de salida fluctúa con la variación de la irradiancia solar y la temperatura. Las condiciones climáticas cambiantes y el comportamiento no lineal de los sistemas fotovoltaicos plantean un desafío en el seguimiento de la variación máxima de PowerPoint. Por lo tanto, para extraer y entregar continuamente la máxima potencia posible del sistema fotovoltaico, en determinadas condiciones ambientales, se debe formular la estrategia de control de seguimiento del punto de máxima potencia (MPPT) que opere continuamente el sistema fotovoltaico en su MPP. Se requiere un controlador no lineal robusto para asegurar MPPT manejando las no linealidades de un sistema y haciéndolo robusto frente a condiciones ambientales cambiantes. El control de modo deslizante (SMC) se usa ampliamente en sistemas de control no lineales y se ha implementado en sistemas fotovoltaicos (PVC) para rastrear MPP. SMC es robusto contra perturbaciones, incertidumbres del modelo y variaciones paramétricas. Representa fenómenos indeseables como el parloteo, inherentes a él, que provocan pérdidas de energía y calor. En esta tesis, en primer lugar, se formula un controlador SMC de orden entero para extraer la máxima potencia de un sistema fotovoltaico solar en condiciones climáticas variables empleando el esquema MPPT de perturbar y observar (P&O) para el sistema fotovoltaico autónomo propuesto. El sistema propuesto consta de dos esquemas de bucles, a saber, el bucle de búsqueda y el bucle de seguimiento. P&O MPPT se utiliza en el bucle de búsqueda para generar la señal de referencia y se utiliza un controlador SMC de seguimiento en el otro bucle para extraer la máxima potencia fotovoltaica. El sistema fotovoltaico está conectado con la carga a través del convertidor elevador DC-DC electrónico de potencia. Primero se deriva un modelo matemático del convertidor elevador y, en base al modelo derivado, se formula un SMC para controlar los pulsos de puerta del interruptor del convertidor elevador. La estabilidad del sistema de circuito cerrado se verifica mediante el teorema de estabilidad de Lyapunov. El esquema de control propuesto se prueba bajo diferentes niveles de irradiancia y los resultados de la simulación se comparan con el controlador clásico proporcional integral derivado (PID). El SMC clásico describe fenómenos indeseables como el parloteo, inherente a él, que causa pérdidas de energía y calor. En la siguiente parte de esta tesis, se analiza el diseño del controlador de modo deslizante adaptativo (ASMC) para el sistema fotovoltaico propuesto. El control adoptado se ejecuta utilizando un ASMC y la mejora se actualiza utilizando un algoritmo de optimización MPPT del Método de búsqueda de patrón mejorado (IPSM). Se utiliza un IPSM MPPT para generar el voltaje de referencia para controlar el controlador ASMC subyacente. Se ha realizado una comparación con otros dos algoritmos de optimización, a saber, Perturb \ Observe (P&O) y Particle Swarm Optimization (PSO) con IPSM para MPPT. Como estrategia no lineal, la estabilidad del controlador adaptativo está garantizada mediante la realización de un análisis de Lyapunov.
The increasing energy demands, depleting fossil fuels, and increasing global warming due to carbon emission has arisen the need for an alternate, overall efficiency, and environment-friendly energy system. Solar energy is considered to be one of the most inexhaustible forms of energy in this universe, but it has the problem of low efficiency due to varying environmental conditions. Solar panel exhibits nonlinear behavior under real climatic conditions and output power fluctuates with the variation in solar irradiance and temperature. Changing weather conditions and nonlinear behavior of PV systems pose a challenge in the tracking of varying maximum PowerPoint. Hence, to continuously extract and deliver the maximum possible power from the PV system, under given environmental conditions, the maximum power point tracking (MPPT) control strategy needs to be formulated that continuously operates the PV system at its MPP. A robust nonlinear controller is required to ensure MPPT by handling nonlinearities of a system and making it robust against changing environmental conditions. Sliding mode control (SMC) is extensively used in non-linear control systems and has been implemented in photovoltaic systems (PV) to track MPP. SMC is robust against disturbances, model uncertainties, and parametric variations. It depicts undesirable phenomena like chattering, inherent in it causing power and heat losses. In this thesis, first, an integer order SMC controller is formulated for extracting maximum power from a solar PV system under variable climatic conditions employing the perturb and observe (P&O) MPPT scheme for the proposed stand-alone PV system. The proposed system consists of two loops schemes, namely the searching loop and the tracking loop. P&O MPPT is utilized in the searching loop to generate the reference signal and a tracking SMC controller is utilized in the other loop to extract the maximum PV power. PV system is connected with load through the power electronic DC-DC boost converter. A mathematical model of the boost converter is derived first, and based on the derived model, an SMC is formulated to control the gate pulses of the boost converter switch. The closed-loop system stability is verified through the Lyapunov stability theorem. The proposed control scheme is tested under varying irradiance levels and the simulation results are compared with the classical proportional integral derivative (PID) controller. Classical SMC depicts undesirable phenomena like chattering, inherent in it causing power and heat losses. In the next part of this thesis, the design of the adaptive sliding mode controller (ASMC) is discussed for the proposed PV system. The adopted control is executed utilizing an ASMC and the enhancement is actualized utilizing an Improved Pattern Search Method (IPSM) MPPT optimization algorithm. An IPSM MPPT is used to generate the reference voltage in order to command the underlying ASMC controller. Comparison with two other optimization algorithms, namely, a Perturb & Observe (P&O) and Particle Swarm Optimization (PSO) with IPSM for MPPT has been conducted. As a non-linear strategy, the stability of the adaptive controller is guaranteed by conducting a Lyapunov analysis. The performance of the proposed control architectures is validated by comparing the proposals with that of the well-known and widely used PID controller. The simulation results validate that the proposed controller effectively improves the voltage tracking, system power with reduced chattering effect, and steady-state error. A tabular comparison is provided at the end of each optimization algorithm category as a resume quantitative comparison. It is anticipated that this work will serve as a reference and provides important insight into MPPT control of the PV systems.

With the increased loading and exploitation of the power transmission system and also due to improved optimised operation, the problem of voltage stability and voltage collapse attracts more and more attention . A voltage collapse can take place in systems or subsystems and can appear quite abruptly. Continuous monitoring of the system state is therefore required. The cause of the 1977 New York black out has been proved to be the reactive power problem. The 1987 Tokyo black out was believed to be due to reactive power shortage and to a voltage collapse at summer peak load. These facts have strongly indicated that reactive power planning and dispatching play an important role in the security of modern power systems. A proper compensation of system voltage profiles will enhance the system securities in the operation and will reduce system losses. In this thesis, some aspects of reactive power dispatch and voltage control problem have been investigated. The research has focused on the following three issues: Firstly, the steady-state stability problem has been tackled where, a voltage collapse proximity indicator based on the optimal impedance solution of a two bus system has been generalised to an actual system and the performance of this indicator has been investigated over the whole range (stable and unstable region) to see how useful this indicator can be for an operator at any operating point. Then we went further to implement a linear reactive power dispatch algorithm in which this indicator was used for the first time to attempt to prevent a voltage collapse in the system. Secondly, a new efficient technique for N-1 security has been incorporated aiming at either maximising the reactive power reserve margin for the generators or minimising active power losses during normal as well as outage conditions (single line outage) .The reactive power redistribution after an outage is based on the S-E graph adopted by Phadke and Spong[72].Thirdly, the dispatch (N-1 security excluded) has been incorporated on line in the O.C.E.P.S. control package to improve the quality of the service and system security by optimally controlling the generator voltages (potentially the reactive control system is able to control transformers, switchable capacitors and reactors). A new function called load voltage control (similar to the load frequency control function) has been introduced to allow smooth variation of the reactive control signals towards their targets.

This paper briefly presents the results of a study of various utility rate schedules from across the United States and describes a video produced to explain some major features of these rate structures. In particular, the demand, energy and power factor sections of each rate schedule are explored to understand the impacts of selected features on utility costs and on evaluation of energy conservation projects. The accompanying video was produced for the Energy Systems Laboratory's Industrial Assessment Center (IAC) at Texas A&M University. This video will be used during industrial audits to explain typical demand, energy and power factor structures and savings potentials that can be realized by implementation of energy conservation retrofit projects, known as energy conservation opportunities (ECO's), that may be presented through the energy audit process.

The topic of this thesis is the study of energy storage systems operating with wind power plants. The motivation for applying energy storage in this context is that wind power generation is intermittent and generally difficult to predict, and that good wind energy resources are often found in areas with limited grid capacity. Moreover, energy storage in the form of hydrogen makes it possible to provide clean fuel for transportation. The aim of this work has been to evaluate how local energy storage systems should be designed and operated in order to increase the penetration and value of wind power in the power system. Optimization models and sequential and probabilistic simulation models have been developed for this purpose.

Chapter 3 presents a sequential simulation model of a general windhydrogen energy system. Electrolytic hydrogen is used either as a fuel for transportation or for power generation in a stationary fuel cell. The model is useful for evaluating how hydrogen storage can increase the penetration of wind power in areas with limited or no transmission capacity to the main grid. The simulation model is combined with a cost model in order to study how component sizing and choice of operation strategy influence the performance and economics of the wind-hydrogen system. If the stored hydrogen is not used as a separate product, but merely as electrical energy storage, it should be evaluated against other and more energy efficient storage options such as pumped hydro and redox flow cells. A probabilistic model of a grid-connected wind power plant with a general energy storage unit is presented in chapter 4. The energy storage unit is applied for smoothing wind power fluctuations by providing a firm power output to the grid over a specific period. The method described in the chapter is based on the statistical properties of the wind speed and a general representation of the wind energy conversion system and the energy storage unit. This method allows us to compare different storage solutions.

In chapter 5, energy storage is evaluated as an alternative for increasing the value of wind power in a market-based power system. A method for optimal short-term scheduling of wind power with energy storage has been developed. The basic model employs a dynamic programming algorithm for the scheduling problem. Moreover, different variants of the scheduling problem based on linear programming are presented. During on-line operation, the energy storage is operated to minimize the deviation between the generation schedule and the actual power output of the wind-storage system. It is shown how stochastic dynamic programming can be applied for the on-line operation problem by explicitly taking into account wind forecast uncertainty. The model presented in chapter 6 extends and improves the linear programming model described in chapter 5. An operation strategy based on model predictive control is developed for effective management of uncertainties. The method is applied in a simulation model of a wind-hydrogen system that supplies the local demand for electricity and hydrogen. Utilization of fuel cell heat and electrolytic oxygen as by-products is also considered. Computer simulations show that the developed operation method is beneficial for grid-connected as well as for isolated systems. For isolated systems, the method makes it possible to minimize the usage of backup power and to ensure a secure supply of hydrogen fuel. For grid-connected wind-hydrogen systems, the method could be applied for maximizing the profit from operating in an electricity market.

Comprehensive simulation studies of different example systems have been carried out to obtain knowledge about the benefits and limitations of using energy storage in conjunction with wind power. In order to exploit the opportunities for energy storage in electricity markets, it is crucial that the electrical efficiency of the storage is as high as possible. Energy storage combined with wind power prediction tools makes it possible to take advantage of varying electricity prices as well as reduce imbalance costs. Simulation results show that the imbalance costs of wind power and the electricity price variations must be relatively high to justify the installation of a costly energy storage system. Energy storage is beneficial for wind power integration in power systems with high-cost regulating units, as well as in areas with weak grid connection.

Hydrogen can become an economically viable energy carrier and storage medium for wind energy if hydrogen is introduced into the transportation sector. It is emphasized that seasonal wind speed variations lead to high storage costs if compressed hydrogen tanks are used for long-term storage. Simulation results indicate that reductions in hydrogen storage costs are more important than obtaining low-cost and high-efficient fuel cells and electrolyzers. Furthermore, it will be important to make use of the flexibility that the hydrogen alternative offers regarding sizing, operation and possibly the utilization of oxygen and heat as by-products.

The main scientific contributions from this thesis are the development of

- a simulation model for estimating the cost and energy efficiency of wind-hydrogen systems,

- a probabilistic model for predicting the performance of a gridconnected wind power plant with energy storage,

- optimization models for increasing the value of wind power in electricity markets by the use of hydrogen storage and other energy storage solutions and the system knowledge about wind energy and energy storage that has been obtained by the use of these models.

Paper 1 is reprinted with kind permission of ACTA Press. Paper 2 is reprinted with kind permission of Elsevier/ Science Direct. http://www.elsevier.com, http://www.sciencedirect.com Paper 3 is reprinted with kind permission of IEEE.

This thesis presents an optimal method of designing and controlling an oscillating energy harvesting system. Many new and emerging energy harvesting systems, such as the energy harvesting backpack and ocean wave energy harvesting, capture energy normally expelled through mechanical interactions. Often the nature of the system indicates slow system time constants and unsteady AC voltages. This paper reveals a method for achieving maximum energy harvesting from such sources with fast determination of the optimal operating condition. An energy harvesting backpack, which captures energy from the interaction between the user and the spring decoupled load, is presented in this paper. The new control strategy, maximum energy harvesting control (MEHC), is developed and applied to the energy harvesting backpack system to evaluate the improvement of the MEHC over the basic maximum power point tracking algorithm.
M.S.E.E.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering MSEE

The objective of the proposed research is to analyze automated residential energy management technology using primary energy source utilization. A residential energy management system (REMS) is an amalgamation of hardware and software that performs residential energy usage monitoring, planning, and control. Primary energy source utilization quantifies power system levels impacts on power generation cost, fuel utilization, and environmental air pollution; based on power system generating constraints and electric load. Automated residential energy management technology performance is quantified through a physically-based REMS simulation. This simulation includes individual appliance operation and accounts for consumer behavior by stochastically varying appliance usage and repeating multiple simulation iterations for each simulated scenario. The effect of the automated REMS under varying levels of control will be considered. Aggregate REMS power system impacts are quantified using primary energy source utilization. This analysis uses a probabilistic economic dispatch algorithm. The economic dispatch algorithm quantifies: fuel usage and subsequent environmental air pollution (EAP) generated; based on power system generating constraints and electric load (no transmission constraints are considered). The analysis will comprehensively explore multiple residential energy management options to achieve demand response. The physically-based REMS simulation will consider the following control options: programmable thermostat, direct load control, smart appliance scheduling, and smart appliance scheduling with a stationary battery. The ability to compare multiple automated residential energy management technology options on an equal basis will guide utility technology investment strategies.

Approved for public release; distribution is unlimited
As the United States Navy makes leaps forward in technology that is being deployed onboard ships, there is a growing need for research to predict what will be needed to integrate new weapon systems with old. Directed energy weapons are being deployed onboard naval platforms starting in 2014, and this paper seeks to answer the question of what energy storage, if any, must be used in conjunction with high-power lasers in order to integrate them with current ships in the fleet. Four energy storage methods are being researched. These storage medias will allow a ship to fire multiple shots from a high-powered laser without taxing the ship’s electrical system. Lead acid batteries, lithium ion batteries, supercapacitors, and flywheels each have their benefits and drawbacks, and those will be discussed. A computer simulation has been developed and used to represent a DDG-51 Arleigh Burke class destroyer and each of the four energy storage methods. This simulation was run repeatedly with different powered high-powered lasers in order to produce a recommendation for what types of energy storage would be necessary to operate these devices onboard ships.

The possibility to use wind power directly in a house to replace part of the used electricity is examined here theoretically. Measured climate data from Finland, Vanda airport at 10 meters height, are used for outdoor temperature and wind data. This data is simulated for 8 different wind turbine power output and a case study residence building is used for the energy demand. The energy demand consists of heating, hot water and electrical equipment. If wind production is higher than energy demand then the remaining energy is stored in one electrical battery or the buildings hot water boiler. Additional excess energy is delivered free to the network and does not taken into account into the energy balance of the building. The 8 different small scale wind turbine options and the energy demand of the house are compared and the profitability of each system is assessed. Based on the available data, excel is used to calculate the energy production and demand over a year based on hourly temperature and wind speed measurements. Some suggestions for further research are given at the end.

Practical vibration energy harvesting tends to be employed where the frequency of the vibration does not vary with time. This is a result of energy harvesting devices resonating at a specific frequency. If the frequency of the vibration changes even slightly from the harvester's natural resonant frequency, then the power generated drops off significantly. Various methods have been proposed to apply kinetic energy harvesting over wider frequency bands, for example by active mechanical tuning of the structure to the vibration, or by adjusting the electrical load. This thesis explores electronic methods of optimally controlling the power electronics that extracts power from the harvester and charges a storage capacitor. The focus is on power levels below lmW, where the power budget for control circuitry is limited to lOs of microwatts or lower. Low-power techniques are investigated that maximise power by optimal resistive loading of the harvester, over a given excitation frequency bandwidth. This includes an experimental investigation of switching-converter control strategies. A low-power power sensing method is presented, which adapts to the available power level to maintain high sensitivity over a wide power range. A discrete component implementation of the method consumes 7.5 /!W and is demonstrated to be effective over a power range of 390 /!W to 750 /!W. A frequency detection method is presented which shows lower power consumption compared to the typically used method. To address the problem of variable frequency excitation, a feed-forward maximum power point tracking control strategy is presented, which demonstrates fast response to changes in the excitation frequency and significant improvement of the performance over the standard maximum power point tracking control. The method relies on an analytical model of the system and the measurement of the excitation frequency. These low-power techniques are implemented in hardware, as a complete self-contained and self-starting energy harvesting system. Depending on the amount of stored energy available, the system moves automatically between passive and active conversion modes, and a mode with optimised feed -forward maximum power point tracking. A minimum operating power of 26 /! W for the active conversion mode has been demonstrated.

Las tendencias en la tecnología actual permiten la reducción tanto en tamaño como en potencia consumida de los sistemas digitales complejos. Esta disminución en el tamaño y el consumo da lugar al concepto de dispositivos portátiles que se integren en la vida pertenencias personales y cotidianas como ropa, relojes, gafas, etc. La fuente de alimentación es un factor limitante en la movilidad de los dispositivos portátiles que se ve reducida por la duración de la batería. Además, debido a los costos y difícil accesibilidad, la sustitución o recarga de las baterías a menudo no es viable para los dispositivos portátiles integrados en ropa inteligente. Los dispositivos vestibles están distribuidos en las pertenencias personales y, por tanto, la recolección de energía del usuario es una alternativa para su alimentación. Dispositivos vestibles pueden crear, al igual que los sensores de una red de sensores inalámbricos (WSN), una red de área corporal. El principal objetivo de esta tesis es el estudio de generadores piezoeléctricos, inductivos y termoeléctricos que recolectan energía del cuerpo humano de forma pasiva. El principio físico de un transductor es el mismo independientemente de si la fuente proviene del entorno o del cuerpo humano. Sin embargo, las limitaciones relacionadas con la baja tensión, corriente y niveles de frecuencia conllevan nuevos requerimientos que no están presentes en el caso de la utilización de las fuentes que ofrece el entorno y que suponen el principal desafío de esta tesis. El tipo de energía entrada y transductor a utilizar forman un tándem donde la elección de uno impone el otro. Es importante que las mediciones se realicen diferentes partes del cuerpo humano, mientras se realizan diferentes actividades físicas para localizar las posiciones y las actividades que producen más energía. El acoplamiento mecánico entre transductor y cuerpo humano depende de la ubicación del transductor y la actividad que se realiza. Un diseño específico, teniendo esto en cuenta puede aumentar más de un 200% la eficiencia del transductor como se ha demostrado con láminas piezoeléctricas situadas en plantillas de zapatos. Se han realizado mediciones de aceleraciones en diferentes partes del cuerpo y diferentes actividades para cuantificar la cantidad de energía disponible en actividades cotidianas. Se ha realizado una simulación a nivel de sistema, modelando los elementos de un sistema de energía autoalimentado. El transductor se ha modelado usando las ecuaciones físicas que lo describen con el objetivo de incluir la parte mecánica del sistema. Se han utilizado modelos eléctricos y de comportamiento para el resto de los componentes. De esta manera, el proceso de diseño de la aplicación en su conjunto (incluyendo la carga y un elemento de almacenamiento de energía cuando es necesario) se simplifica a la hora de lograr los requisitos planteados. Obviamente, la carga debe ser un dispositivo de bajo consumo como por ejemplo un transmisor RF. En este caso, es preferible alimentar la carga de forma discontinua, sin una batería, como se deduce de los resultados obtenidos mediante simulación. Sin embargo, la evolución de los transmisores RF de baja potencia puede cambiar esta conclusión en función sobre todo de la evolución del consumo de energía en stand-by y el tiempo de configuración para la operación de transmisión. Se ha deducido a partir del análisis de los generadores inductivos que el análisis en el dominio temporal permite calcular algunas magnitudes que no están disponibles en el dominio frecuencial. Por ejemplo, la potencia máxima se puede calcular en el dominio frecuencial, pero para aplicaciones de recolección de energía es más interesante saber el valor de la energía recuperada durante un cierto tiempo o la potencia media ya que la potencia generada por las actividades humanas pueden ser muy discontinua. Se ha demostrado que los transductores recolectores de energía son capaces de suministrar alimentación a dispositivos electrónicos de baja potencia, como quedó demostrado con un transmisor RF alimentado por una termogenerador que emplea el gradiente de temperatura existente entre el cuerpo humano y el entorno (3-5 K) y que es capaz de realizar medidas y transmitirlas una vez cada segundo
The trends in technology allow the decrease in both size and power consumption of complex digital systems. This decrease in size and power gives rise to the concept of wearable devices which are integrated in everyday personal belongings like clothes, watch, glasses, et cetera. Power supply is a limiting factor in the mobility of the wearable device which gets restricted to the lifetime of the battery. Furthermore, due to the costs and inaccessible locations, the replacement or recharging of batteries is often not feasible for wearable devices integrated in smart clothes. Wearable devices are devices distributed in personal belongings and thus, an alternative for powering them is to harvest energy from the user. Therefore, the energy can be harvested, distributed and supplied over the human body. Wearable devices can create, like the sensors of a Wireless Sensor Network (WSN), a Body Area Network. A study of piezoelectric, inductive and thermoelectric generators that harvest passive human power is the main objective of this thesis. The physical principle of an energy harvesting generator is obviously the same no matter whether it is employed with an environmental or human body source. Nevertheless, the limitations related to low voltage, current and frequency levels obtained from human body sources bring new requirements to the energy harvesting topic that were not present in the case of the environment sources. This analysis is the motivation for this thesis. The type of input energy and transducer form a tandem since the election of one imposes the other. It is important that measurements are done in different parts of the human body while doing different physical activities to locate which positions and activities produce more energy. The mechanical coupling between the transducer and the human body depends on the location of the transducer and the activity that is done. A specific design taking this into account can increase more than a 200% the efficiency of the transducer as has been demonstrated with piezoelectric films located in the insoles of shoes. Acceleration measurements have been performed in different body locations and different physical activities, in order to quantify the amount of available energy associated with usual human movements. A system-level simulation has been implemented modeling the elements of an energy self-powered system. Physical equations have been used for the transducer in order to include the mechanical part of the system and electrical and behavioral models for the rest of the components. In this way, the process of the design of the complete application (including the load and an energy storage element when it is necessary) is simplified to achieve the expected requirements. Obviously, the load must be a low power consumption device as for example a RF transmitter. In this case, it is preferable to operate it in a discontinuous way without a battery as it is deduced from simulation results obtained. However, the evolution in low power transmission modules can change this conclusion depending mostly on the evolution of the power consumption in stand-by mode and the configuration time in transmission operation. It has been deduced from the analysis of inductive generators that time-domain analysis allows to calculate some magnitudes that are not available in frequency domain. For example, the maximum power can be calculated in frequency domain, but for energy harvesting applications it is more interesting to know the value of the recovered energy during a certain time, or the average power since the power generated by human activities can be highly discontinuous. It has been demonstrated that energy harvesting transducers are able to supply power to present-day low power electronic devices as was demonstrated with a RF transmitter powered by a thermogenerator that employs the temperature gradient between human body and the environment (3-5 K) and that it is able to sense and transmit data once every second.

Piezoelectric energy harvesting has been around for almost a decade to generate power from the ambient vibrations. Although the generated power is very small, but there are several ways to increase and enhance the generated power. This project presents different methods of optimizing the output power by changing the structural configuration of the energy harvesters, selection of piezoelectric material and circuit interface of these harvesters. To understand the different steps of the enhancement, the process of energy conversion by piezoelectric material has been first looked at. Different groups of piezoelectric material were studied to see what kind of materials have the ability of increasing the generated power. As mechanical configuration of the energy harvesters has a significant effect on the output voltage, their configuration such as Cantilever beam type, Cymbal type and Circular diaphragms has been described and compared. After the power generated in the piezoelectric crystal , the current is sent to through an interface circuit to get rectified and regulated. This circuit can be modified to increase the power as well. There are several types of circuits that can increase the output voltage significantly. Synchronized Switch Harvesting (SSH) techniques, Synchronous Electric Charge Extraction technique and voltage doubler are such examples. These techniques have been also studied and compared. Because of the outgrowing industry of piezoelectric energy harvesting in Medical field, their function and their progress has also been reviewed.

Along with increased oil prices and rising environmental issues, a demand for alternatives to combustion engine driven hydraulic applications has risen. In the field of mobile hydraulics, the hydraulic applications have traditionally been driven by the combustion engine of the vehicle on which they are mounted. By instead using a battery driven power pack the hydraulic application is able to operate without the engine running, saving fuel costs and reducing sound levels. In this thesis, the concept of using an electric-hydraulic power pack with a variable-speed electric motor and a fixed-displacement hydraulic pump to provide power to a truck-mounted loader crane is investigated. This concept is compared to an electric-hydraulic system imitating the conventional combustion engine system by using a fixed-speed electric motor connected to a variable-displacement pump. The use of a variable speed motor where the speed can be controlled electrically by a control unit creates possibilities of using different control strategies to improve the efficiency and responsiveness of the application. The efficiencies of the two electric-hydraulic systems are compared by constructing a physical test rig and performing measurements in a test lab. The tests have shown an increased efficiency of about 20 \% when using the variable speed configuration. Three different control strategies are also investigated and tested on a simulated model. The simulations show that very good responsiveness and robustness can be achieved by using a hydraulic flow feed forward controller with a complementary pressure feedback controller. Furthermore, by controlling the hydraulic flow to the heaviest of the crane loads entirely with the flow from the hydraulic pump, the hydraulic pressure can be reduced and energy efficiency increased.

Global demand for renewable energy has provided impetus for increased research into photovoltaic (PV) technology. Photovoltaic modules have intrinsically low efficiency and therefore, to maximise generated electricity, advances must be made in the efficient extraction of energy to maintain viability of their use. In this thesis, efficiency is maximised using novel power electronics. To facilitate advanced design, novel methods for generating accurate models of PV generators are presented. Conventional methods rely on the characterisation of PVs under continuous illumination. These methods cause heating of the module which can degrade the performance below that which would be seen during normal operation. To counter this problem, the use of flashed illumination is presented as a method for unobtrusively generating a PV electrical characteristic which can be used for accurate model-parameter extraction. To develop optimised-switch mode power converters for PVs, the reasons for suboptimal operation in existing converters is analysed and validated experimentally. Whereas existing research has considered the effect of current perturbation at mains frequency, this thesis extends the analysis to 500 kHz, which represents typical switchmode operation. A typical boost converter cannot meet the requirements for optimal power extraction from the PV module and therefore a novel circuit topology based on a SEPIC converter which can achieve optimal conditions is developed and presented. Since the methods for power transfer optimisation presented in this thesis require that the additional hardware is implemented in order to take full advantage of the PV generator, a method is presented whereby the resulting increased cost is significantly reduced. This reduction is achieved through the adaptation of redundant computer power supplies for PV battery charging applications, a method which can be used to produce a PV battery charger with minimal material or design investment.

Thesis (Master of Engineering in Electrical Engineering))--Cape Peninsula University of Technology, 2018.
Industry, which forms the lifeblood of South Africa’s economy, is under threat as a result of increased electricity pricing and unstable supply. Wheeling of energy, which is a method to transport electricity generated from an Independent Power Producer (IPP) to an industrial consumer via the utility’s network, could potentially address this problem. Unlike South Africa’s electricity landscape, which is highly regulated and monopolized by Eskom, most developed countries have deregulated their electricity market, which has led to greater competition for electricity supply. This thesis, presents an evaluation of the economic viability and technical concerns arising from third party transportation of energy between an IPP and an industrial consumer. IPP’s are able to generate electricity from various renewable distributed generation (DG) sources, which are often physically removed from the load. In practice, electricity could be generated by an IPP and connected to a nearby Main Transmission Substation (MTS) in a region with high solar, wind or hydropower resources and sold to off-takers a few hundred kilometres away. Using two software simulation packages, technical and economic analysis have been conducted based on load data from two industrial sites, to determine the viability of wheeling energy between an IPP and off-taker. The viability will be evaluated based on levelized cost of electricity (LCOE); net present cost (NPC); DG technology; distance from the load; available renewable resources; impact on voltage profile, fault contribution, thermal loading of the equipment and power loss. The results from both case studies show that the impact of DG on the voltage profile is negligible. The greatest impact on voltage profile was found to be at the site closest to the load. Asynchronous and synchronous generators have a greater fault contribution than inverter-based DG. The fault contribution is proportional to the distance from the load. Overall, thermal loading of lines increased marginally, but decreased based on distances from the load. Power loss on short lines is negligible but there is a significant loss on the line between the load and DG based on the distance from the load. Electricity generated from wind power is the most viable based on LCOE and NPC. For larger wind systems, as illustrated by the second case study, grid parity has already been reached. Wheeling of wind energy has already proven to be an economically viable option. According to future cost projection, large scale solar energy will become viable by 2019. The concept of wheeling energy between an IPP and off-taker has technical and economic merit. Wheeling charges are perceived to be high, but this is not the case as wheeling tariffs consist of standard network charges. In the future, renewable energy will continue to mature based on technology and cost. Solar energy, including lithium-ion battery back-up technology, looks promising based on future cost projections. Deregulation of the electricity market holds the key to the successful implementation of energy wheeling as it will open the market up for greater competition.

The increasing focus on large scale integration of new renewable energy sources like wind power and wave power introduces the need for energy storage. Superconducting Magnetic Energy Storage (SMES) is a promising alternative for active power compensation. Having high efficiency, very fast response time and high power capability it is ideal for levelling fast fluctuations. This thesis investigates the feasibility of a current source converter as a power conditioning system for SMES applications. The current source converter is compared with the voltage source converter solution from the project thesis. A control system is developed for the converter. The modulation technique is also investigated. The SMES is connected in shunt with an induction generator, and is facing a stiff network. The objective of the SMES is to compensate for power fluctuations from the induction generator due to variations in wind speed. The converter is controlled by a PI-regulator and a current compensation technique deduced from abc-theory. Simulations on the system are carried out using the software PSIM. The simulations have proved that the SMES works as both an active and reactive power compensator and smoothes power delivery to the grid. The converter does however not seem like an optimum solution at the moment. High harmonic distortion of the output currents is the main reason for this. However this system might be interesting for low power applications like wave power. I

Climate change is real. Global human population is growing as never before. Natural resources are limited. These factors have taken different countries to embrace new pathways in order to fulfill the energy needs of their population, understanding that energy is a fundamental instrument for achieving sustainable development. Since each economy decides, according to its needs, possibilities and interests, its own shift of energy production and consumption, this tendency has received the name of energy transitions. Energy transitions, through digitalization, decentralization and decarbonization of the energy system, have placed the power sector as the center of modern infrastructures, making it imperative to procure its security in the long-term. This thesis is focused on the security of electrical systems, for which, after performing a thorough review on energy policies of different economies, it presents a multi-dimensional index as a tool for policy makers aimed to assess long-term security of power systems. The composed index is subsequently applied to different nations from two different approaches: the tracking of a country’s development and the evaluation, comparison and ranking of different economies in a specific time frame. The designed tool represents a comprehensive framework for assessing -and improving- energy security in power systems, being this precisely the main contribution of the present thesis: the development and proposal of an instrument that contributes, through the betterment of energy systems by making them more secure, to achieve sustainable development.
El cambio climático es real. La población humana global está creciendo como nunca antes. Los recursos naturales son limitados. Estos factores han llevado a los distintos países a adoptar distintas rutas encaminadas a satisfacer las necesidades energéticas de su población, entendiendo a la energía como un instrumento fundamental para alcanzar el desarrollo sostenible. Debido a que cada economía decide, de acuerdo a sus necesidades, posibilidades e intereses, su propio cambio en producción y consumo de energía, esta tendencia ha recibido el nombre de transiciones energéticas. Estas, a través de la digitalización, descentralización y descarbonización del sistema energético, han colocado al sistema eléctrico como el centro de las infraestructuras modernas, haciendo imperativo el procurar su seguridad en el largo plazo. La presente tesis está enfocada en la seguridad de los sistemas eléctricos, para lo que, luego de una exhaustiva revisión de políticas energéticas de distintas economías, se presenta un índice multidimensional como herramienta para los encargados de la elaboración de políticas orientadas a procurar la seguridad de los sistemas eléctricos. El índice compuesto es posteriormente aplicado a diferentes naciones desde dos perspectivas distintas: el seguimiento temporal del desarrollo de un país y la evaluación, comparación y jerarquización de diferentes economías en un tiempo específico. La herramienta diseñada representa un marco integral para la evaluación y mejoramiento de la seguridad energética de los sistemas eléctricos, siento precisamente esta la mayor contribución de la presente tesis: el desarrollo y propuesta de un instrumento que contribuya, a través del mejoramiento de los sistemas energéticos, haciéndolos más seguros, a alcanzar el desarrollo sostenible.
Enginyeria elèctrica

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, May, 2020
Cataloged 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

Kiljanov G.M. Energy storage in autonomous power plants using renewable energy sources, 2017 - p.104, 11 tables, 40 pic. Head Bessel V.V., Professor, Ph.D. Department of Thermodynamics and Thermal Engines. An analysis of existing energy storage devices in the world is carried out. The scientific and technical basis of energy storage. The device and the operating principle of an autonomous combined power plant with an energy storage device are considered. On the basis of the technological calculation, an optimal combination of a wind generator, a system of solar panels and a reservoir, which can provide reliable and uninterrupted power generation, was chosen. The economic efficiency of the project on the use of combined medium power plants at gas production facilities in remote areas was estimated. Conclusions are drawn about the advisability of introducing energy systems based on renewable sources with energy storage devices at the country's enterprises.
Kilyanov G.M. Energilagring i autonoma kraftverk som använder förnybara energikällor, 2017 - s.105, 11 tabeller, 40 bild. Chef Bessel V.V., professor, Ph.D. Institutionen för termodynamik och termiska motorer. En analys av befintliga energilagringsenheter i världen utförs. Den vetenskapliga och tekniska grunden för energilagring. Enheten och driftsprincipen för ett autonomt kombinerat kraftverk med en energilagringsanordning beaktas. Baserat på den tekniska beräkningen valdes en optimal kombination av en vindgenerator, ett system av solpaneler och en reservoar, som kan ge pålitlig och oavbruten elproduktion. Projektets ekonomiska effektivitet på användningen av kombinerade medelkraftverk vid gasproduktionsanläggningar i avlägsna områden uppskattades. Slutsatser dras om att det är lämpligt att införa energisystem baserade på förnyelsebara källor med energilagringsenheter hos landets företag.

Energy is a critical resource in the design of wireless networks since wireless devices are usually powered by batteries. Battery capacity is finite and the progress of battery technology is very slow, with capacity expected to make little improvement in the near future. Under these conditions, many techniques for conserving power have been proposed to increase battery life. In this dissertation we consider two approaches to conserving the energy consumed by a wireless network interface. One technique is to use power saving mode, which allows a node to power off its wireless network interface (or enter a doze state) to reduce energy consumption. The other is to use a technique that suitably varies transmission power to reduce energy consumption. These two techniques are closely related to theMAC (Medium Access Control) layer. With respect to power saving mode, we study IEEE 802.11 PSM (Power Saving Mechanism) and propose a scheme that improves its energy efficiency. We also investigate the interaction between power saving mode and TCP (Transport Control Protocol). As a second approach to conserving energy, we investigate a simple power control protocol, called BASIC, which uses the maximum transmission power for RTS-CTS and the minimum necessary power for DATA-ACK. We identify the deficiency of BASIC, which increases collisions and degrades network throughput, and propose a power control protocol that addresses these problems and achieves energy savings. Since energy conservation is not an issue limited to one layer of the protocol stack, we study a cross layer design that combines power control at the MAC layer and power aware routing at the network layer. One poweraware routing metric is minimizing the aggregate transmission power on a path from source to destination. This metric has been used along with BASIC-like power control under the assumption that it can save energy, which we show to be false. Also, we show that the power aware routing metric leads to a lower throughput. We show that using the shortest number of hops in conjunction with BASIC-like power control conserves more energy than power aware routing with BASIC-like power control.

The present day digital computing resources are overburdened by the amount of calculation necessary for power system dynamic simulation. Although the hardware has improved significantly, the expansion of the interconnected systems, and the requirement for more detailed models with frequent solutions have increased the need for simulating these systems in real time. To achieve this, more effort has been devoted to developing and improving the application of numerical methods and computational techniques such as sparsity-directed approaches and network decomposition to power system dynamic studies. This project is a modest contribution towards solving this problem. It consists of applying a very efficient sparsity technique to the power system dynamic simulator under a wide range of events. The method used was first developed by Zollenkopf (^117) Following the structure of the linear equations related to power system dynamic simulator models, the original algorithm which was conceived for scalar calculation has been modified to use sets of 2 * 2 sub-matrices for both the dynamic and algebraic equations. The realisation of real-time simulators also requires the simplification of the power system models and the adoption of a few assumptions such as neglecting short time constants. Most of the network components are simulated. The generating units include synchronous generators and their local controllers, and the simulated network is composed of transmission lines and transformers with tap-changing and phase-shifting, non-linear static loads, shunt compensators and simplified protection. The simulator is capable of handling some of the severe events which occur in power systems such as islanding, island re-synchronisation and generator start-up and shut-down. To avoid the stiffness problem and ensure the numerical stability of the system at long time steps at a reasonable accuracy, the implicit trapezoidal rule is used for discretising the dynamic equations. The algebraisation of differential equations requires an iterative process. Also the non-linear network models are generally better solved by the Newton-Raphson iterative method which has an efficient quadratic rate of convergence. This has favoured the adoption of the simultaneous technique over the classical partitioned method. In this case the algebraised differential equations and the non-linear static equations are solved as one set of algebraic equations. Another way of speeding-up centralised simulators is the adoption of distributed techniques. In this case the simulated networks are subdivided into areas which are computed by a multi-task machine (Perkin Elmer PE3230). A coordinating subprogram is necessary to synchronise and control the computation of the different areas, and perform the overall solution of the system. In addition to this decomposed algorithm the developed technique is also implemented in the parallel simulator running on the Array Processor FPS 5205 attached to a Perkin Elmer PE 3230 minicomputer, and a centralised version run on the host computer. Testing these simulators on three networks under a range of events would allow for the assessment of the algorithm and the selection of the best candidate hardware structure to be used as a dedicated machine to support the dynamic simulator. The results obtained from this dynamic simulator are very impressive. Great speed-up is realised, stable solutions under very severe events are obtained showing the robustness of the system, and accurate long-term results are obtained. Therefore, the present simulator provides a realistic test bed to the Energy Management System. It can also be used for other purposes such as operator training.

En aquesta tesi doctoral es presenta un mètode sistemàtic per a la síntesi de giradors de potència. A partir d'aquest mètode s'han generat i classificat diverses estructures giradores. Cadascun d'aquests giradors, que poden tenir característiques diferents, pot ser útil en diferents aplicacions.
Des d'un punt de vista circuital, es tracta d'una estructura de dos ports que es caracteritza per algun d'aquests dos grups d'equacions: 1) I1=gV2, I2=gV1 , 2) V1=rI2, V2=rI1, on I1, V1, i I2, V2 són els valors en contínua corresponents als valors de tensió i corrent als ports d'entrada i sortida respectivament, essent g (r) la conductància (resistència) del girador.
En aquesta tesi, les estructures giradores de potència s'han classificat en funció de com transformen una font d'excitació al port d'entrada en la seva representació dual al port de sortida. Segons aquesta classificació es poden distingir tres tipus de giradors: 1) girador de potència de tipus G, 2) girador de potència de tipus G amb corrent d'entrada controlada i 3) giradors de potència de tipus R. Les categories 1 i 2 són les dues possibles solucions de síntesi de les equacions (1), mentre que la categoria 3 correspon a la solució de síntesi de les equacions (2).
A més a més, no existeixen estudis sistemàtics on basant-se en les equacions de definició s'arribi finalment a una verificació experimental. En aquesta tesi es presenta el disseny i anàlisi dels giradors que s'han presentat. L'anàlisi cobreix exhaustivament l'estudi tant del comportament dinàmic com estàtic dels giradors presentats. Aquests giradors es poden considerar com estructures canòniques per al processat de potència.
A més a més, es presenten algunes funcions bàsiques del processat de potència realitzades amb giradors de potència. Com per exemple: conversió tensió-corrent, corrent-tensió, adaptació d'impedàncies i regulació de tensió.
Les característiques de cada girador depenen no només de la topologia convertidora sinó també del funcionament del control del convertidor. S'han investigat dos tècniques de control: el control en mode lliscant i el control no lineal basat en dinàmica zero. Per tant, les estructures giradores proposades poden treballar tant a freqüència constant com a freqüència variable.
Finalment s'han verificat les previsions teòriques mitjançant simulació i verificació experimental.
In this thesis, a systematic approach to the synthesis of power gyrators is presented. Based on this approach, several gyrator structures can be generated and classified. Each of these gyrators has its own features and is suitable of different applications.
From a circuit standpoint, a power gyrator is a two-port structure characterized by any of the following two set of equations: 1) I1=gV2, I2=gV1 , 2) V1=rI2, V2=rI1, where I1, V1, and I2, V2 are DC values of current and voltage at input and output ports respectively and g ( r ) is the gyrator conductance ( resistance ).
In this thesis, power gyrator structures are classified by the manner they transform an excitation source at the input port into its dual representation at the output port. Based on this classification, there exist three types of power gyrators: 1) power gyrators of type G, 2) power gyrators of type G with controlled input current and 3) power gyrators of type R. Categories 1 and 2 are the two possible synthesis solutions to the set of equations ( 1 ) while category 3 corresponds to the synthesis solution of ( 2 ).
Thus far, no systematic works have been done starting at the definition equations and ending at the experimental verification. In this thesis, the analysis and design for the disclosed power gyrators are presented. The analysis covers exhaustingly the study of both static and dynamic behavior of the reported power gyrators. These power gyrators presented can be considered as canonical structures for power processing.
Thus, some basic power processing functions done by the presented power gyrators are reported. Namely, voltage to current conversion, current to voltage conversion, impedance matching and voltage regulation.
The performance characteristics of a power gyrator depend not only on the circuit topology but also depend on the converter control operation.
Hence, two main control schemes are investigated, namely, sliding-mode control schemes and zero-dynamics-based PWM nonlinear control. Therefore, the proposed gyrator structures can operate indistinctly at constant or at variable switching frequency.
In addition, experimental and computer simulation results of the power gyrators presented are given in order to verify the theoretical predictions.

Motion-driven energy harvesters can replace batteries in low power wireless sensors, however selection of the optimal type of transducer for a given situation is difficult as the performance of the complete system must be taken into account in the optimisation. In this thesis, a complete piezoelectric energy harvester system model including a piezoelectric transducer, a power conditioning circuit, and a battery, is presented allowing for the first time a complete optimisation of such a system to be performed. Combined with previous work on modelling an electrostatic energy harvesting system, a comparison of the two transduction methods was performed. The results at 100 Hz indicate that for small MEMS devices at low accelerations, electrostatic harvesting systems outperform piezoelectric but the opposite is true as the size and acceleration increases. Thus the transducer type which achieves the best power density in an energy harvesting system for a given size, acceleration and operating frequency can be chosen. For resonant vibrational energy harvesting, piezoelectric transducers have received a lot of attention due to their MEMS manufacturing compatibility with research focused on the transduction method but less attention has been paid to the output power electronics. Detailed design considerations for a piezoelectric harvester interface circuit, known as single-supply pre-biasing (SSPB), are developed which experimentally demonstrate the circuit outperforming the next best known interface's theoretical limit. A new mode of operation for the SSPB circuit is developed which improves the power generation performance when the piezoelectric material properties have degraded. A solution for tracking the maximum power point as the excitation changes is also presented.

Purpose/aim The aim is to explore which price policy of the Chinese wind power is the most suitable for the market. Design/methodology/approach Data has been collected through questionnaires. The analysis includes the statistical test in form of chi-square. Additionally the whole thesis followed the onion process put forward by Saunders. Findings The analysis showed that the price policy which is based on the local price of coal is more suitable for the market than the price policy decided by concession projects. Originality/value An original idea is given the relationship between ages, education levels and two policies. Further, the empirical data is collected from a comprehensive online-forum, so that the samples are randomly selected. The data shows that the businesses which want to enter the Chinese wind power market should choose the price policy which is based on the local price of coal. This choice should be useful in the real life.

Energy storage is currently gaining considerable attention due to the current energy crisis and severe air pollution. The development of new and clean forms of energy and related storing devices is in high demanded. Dielectric capacitors, exhibiting high power density, long life and cycling life, are potential candidates for portable devices, transport vehicles and stationary energy resources applications. However, the energy density of dielectric capacitors is relatively low compared to that of traditional batteries, which inhibits their future development. In the current work, three types of dielectrics, namely antiferroelectric samarium-doped BiFeO3 (Bi1-xSmxFeO3), linear dielectric (potential antiferroelectric) BiNbO4 and incipient ferroelectric TiO2, have been investigated to develop their potential as energy storage capacitors. For the samarium-doped BiFeO3 (Bi1-xSmxFeO3) system, the effect of samarium content in the A-site (x=0.15, 0.16, 0.165 and 0.18) on the structural phase transitions and electrical properties across the Morphotropic Phase Boundary (MPB) were studied. A complex coexistence of rhombohedral R3c, orthorhombic Pbam and orthorhombic Pnma was found in the selected compositions. The R3c phase is the structure of pure BiFeO3, the Pbam phase has a PbZrO3-like antiferroelectric structure and the Pnma phase has a SmFeO3-like paraelectric structure. The presence of the PbZrO3-like antiferroelectric structure was confirmed by the observation of the 14{110}, 14{001}, 12{011} and 12{111} superlattice reflections in the transmission electron microscopy diffraction patterns. The weight fractions of the three phases varied with different calcination conditions and Sm substitution level. By increasing the calcination temperature, the weight fractions of the Pbam increased, while that of the R3c decreased. The fraction of the Pnma phase is mainly derived by the Sm concentration and is barely affected by the calcination temperature. The increase of Sm concentration, determined an increase of the weight fraction of the Pnma phase and a decrease of the Pbam and the R3c phases. Temperature dependent dielectric measurements and high temperature XRD of Bi0.85Sm0.15FeO3 revealed several phase transitions. The drastic weight fraction change between the Pbam and the Pnma phase around 200 °C is assumed as the Curie transition of the antiferroelectric Pbam phase. The transition at 575 °C is related to the diminishing of the R3c phase and is suggested as the Curie transition of the ferroelectric R3c phase. The Curie point of the antiferroelectric Pbam phase and the ferroelectric R3c phase in the Bi1-xSmxFeO3 ceramics shifted towards lower temperature with an increase of the Sm concentration. Current peaks were obtained in current-electric field loops in Bi0.85Sm0.15FeO3, which are correlated to domain switching in the R3c phase. The ferroelectric behavior was suppressed in Bi1-xSmxFeO3 (x=0.16, 0.165, 0.18), which is due to the gradually diminished contribution from the R3c phase. The system Bi0.82Sm0.18FeO3 showed the highest energy density of 0.64 J cm-3 (error bar ±0.02). For the BiNbO4 system, single phase α-BiNbO4 (space group Pnna) and β-BiNbO4 (space group P-1) powder and ceramics were produced. The longstanding issue related to the sequence of the temperature-induced phase transitions has been clarified. It is demonstrated that the β phase powder could be converted back to the  phase when annealed in the temperature range 800 °C -1000 °C with certain incubation time. The β to  phase transition is a slow kinetic process because sufficient temperature and time are required for the transition. In bulk ceramics with β phase, this transformation is impeded by inner stress, while it is favored by graphite-induced reducing atmosphere. A high temperature  phase has been revealed and the structure has been resolved. The structure of the  phase is monoclinic with a space group of P21/c. The lattice parameters are: a = 7.7951(1) Å, b = 5.64993(9) Å, c = 7.9048(1) Å,  = 104.691(2) Z=4. The volume is 336.76 (2) Å3. The calculated density is 7.217 g cm-3. The phase relationships among ,  and  phases have been clarified. It was found that the  phase (for both powder and ceramic) transforms into the  phase at 1040 °C on heating, and that the  phase always transforms into the  phase at 1000 °C on cooling. Meanwhile, a reversible first-order  to  phase transition is observed at ca. 1000 °C for both powder and ceramic if no incubation is processed on heating. The electric properties of both α- and - BiNbO4 have been investigated. The breakdown field of both ceramics were too low to observe any possible field-induced transition. As a result, linear P-E loops were obtained in each phase. The energy densities of α- and - BiNbO4 ceramics are 0.03 and 0.04 J cm-3 (error bar ±0.001), respectively. For the TiO2 system, ceramics were produced by conventional sintering and spark plasma sintering (SPS). Compared to conventional sintering, SPS technique produced dense ceramics without using sintering aids and avoided abnormal grain growth. Relaxation behavior related to the oxygen hopping among vacant sites is observed in the temperature range of 200 to 600 °C. TiO2 exhibits ultra-low loss at terahertz frequencies due to the reduced contribution of oxygen vacancies relaxation. TiO2 has a high breakdown field, but still has low polarization. The highest energy density obtained inTiO2 ceramics is 0.3 J cm-3 (error bar ±0.01).

Energy harvesting is one of the key technologies for the realization of autonomous sensing. The aim of this thesis is to develop low-frequency broadband rotational energy harvesting solutions for self-powered sensing. As an example of rotational energy harvesting, an airflow energy harvester using a miniaturized turbine and piezoelectric transduction was first introduced. Rotation was converted from airflow by the turbine, and a piezoelectric beam was actuated by the turbine rotor using magnetic plucking. Issues, including high cut-in speed and low output power at high rotational frequencies, were discovered. In order to decrease the cut-in speed, a self-regulating mechanism was proposed and integrated. The magnetic plucking strength can be passively adjusted according to the rotational speed. This self-regulating harvester exhibited a lower cut-in speed. In order to understand the limited performance at high rotational frequencies and to optimize the design, a theoretical model was built. Different arrangements were investigated, showing that this harvester is ideal to operate at low excitation frequency far below the piezoelectric beam's resonant frequency. Bistable behaviour was also employed and studied to enhance the energy harvesting capability over a wide bandwidth at low frequency. Then, a complete self-powered condition monitoring system, including a bistable frequency up-converting harvester, a power management circuit and a wireless sensor node, was studied and developed to implement the concept of self-powered sensing. Finally, a fundamental study was conducted for three types of rotational energy harvesters, including electromagnetic, piezoelectric resonant, and piezoelectric non-resonant harvesters. Scaling laws for each type were established to study harvesters' performance for different operating frequencies and device dimensions. This study provides a guideline for selection and design of rotational energy harvesters with specific requirements of device dimension and operating frequency.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 199-205).
Portable electronics have fueled the rich emergence of new applications including multi-media handsets, ubiquitous smart sensors and actuators, and wearable or implantable biomedical devices. New ultra-low power circuit techniques are constantly being proposed to further improve the energy efficiency of electronic circuits. A critical part of these energy conscious systems are the energy processing and power delivery circuits that interface with the energy sources and provide conditioned voltage and current levels to the load circuits. These energy processing circuits must maintain high efficiency and reduce component count for the final solution to be attractive from an energy, size and cost perspective. The first part of this work focuses on the development of on-chip voltage scalable switched capacitor DC-DC converters in digital CMOS processes. The converters are designed to deliver regulated scalable load voltages from 0.3V up to the battery voltage of 1.2V for ultra-dynamic voltage scaled systems. The efficiency limiting mechanisms of these on-chip DC-DC converters are analyzed and digital circuit techniques are proposed to tackle these losses. Measurement results from 3 test-chips implemented in 0.18pm and 65nm CMOS processes will be provided. The converters are able to maintain >75% efficiency over a wide range of load voltage and power levels while delivering load currents up to 8mA. An embedded switched capacitor DC-DC converter that acts as the power delivery unit in a 65nm subthreshold microcontroller system will be described. The remainder of the thesis deals with energy management circuits for battery-less systems. Harvesting ambient vibrational, light or thermal energy holds much promise in realizing the goal of a self-powered system. The second part of the thesis identifies problems with commonly used interface circuits for piezoelectric vibration energy harvesters and proposes a rectifier design that gives more than 4X improvement in output power extracted from the piezoelectric energy harvester. The rectifier designs are demonstrated with the help of a test-chip built in a 0.35pm CMOS process. The inductor used within the rectifier is shared efficiently with a multitude of DC-DC converters in the energy harvesting chip leading to a compact, cost-efficient solution. The DC-DC converters designed as part of a complete power management solution achieve efficiencies of greater than 85% even in the micro-watt power levels output by the harvester. The final part of the thesis deals with thermal energy harvesters to extract electrical power from body heat. Thermal harvesters in body-worn applications output ultra-low voltages of the order of 10's of milli-volts. This presents extreme challenges to CMOS circuits that are powered by the harvester. The final part of the thesis presents a new startup technique that allows CMOS circuits to interface directly with and extract power out of thermoelectric generators without the need for an external battery, clock or reference generators. The mechanically assisted startup circuit is demonstrated with the help of a test-chip built in a 0.35pm CMOS process and can work from as low as 35mV. This enables load circuits like processors and radios to operate directly of the thermoelectric generator without the aid of a battery. A complete power management solution is provided that can extract electrical power efficiently from the harvester independent of the input voltage conditions. With the help of closed-loop control techniques, the energy processing circuit is able to maintain efficiency over a wide range of load voltage and process variations.
by Yogesh Kumar Ramadass.
Ph.D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 111-113).
Constant power loads (CPLs) are a class of loads steadily increasing in use. They are present whenever a load is regulated to maintain constant output power, such as with LED drivers in high quality lighting that is impervious to input fluctuations. Because CPLs exhibit a negative incremental input impedance, they pose stability concerns in DC and AC systems. This thesis presents a power converter for a constant power LED bulb that presents a favorable input impedance to the grid. The use of an energy buffer allows the converter to draw variable power in order to resemble a resistive load, while the output consumes constant power. A switched-mode power supply consisting of a cascaded boost and buck converter accomplishes this by storing energy in the boost stage output capacitor. Experimental results demonstrate that the converter exhibits a resistive input impedance at frequencies over 0.5 Hz while maintaining constant power to the LED load.
by Manuel Gutierrez.
S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Political Science, 2007.
Includes bibliographical references.
Russia has organized its energy industry similarly to a vertically integrated energy corporation. Not only does Russia possess vast oil and gas reserves, it also has capabilities at every step in the production chain. The execution of Russian energy strategy is incredibly intricate and flows from all points including the state, firms, suppliers, degrees of ownership and transit locales. This work reviews five important aspects of Russia's vertical integration strategy. Firstly, Russia is brining the domestic industry under state control. Secondly, it has pushed out particular types of foreign investment in order to gain control of domestic reserves, their monetization and the development of important projects. Thirdly, Russia seeks to keep resource rich states in its near abroad in its sphere of influence in order to keep their supply within its grasp. Fourthly, it manages relations with neighboring states in possession of transit infrastructure to keep supply routes open to markets. Lastly, it invests abroad in order to increase market presence, cut out middlemen, and further build production chains. Russia expects to strengthen its international position, both economically and geopolitically by undertaking this strategy of vertical integration.
by Nina J. Fahy.
S.M.

The energy harvesting research field has grown considerably in the last decade due to increasing interests in energy autonomous sensing systems, which require smart and efficient interfaces for extracting power from energy source and power management (PM) circuits. This thesis investigates the design trade-offs for minimizing the intrinsic power of PM circuits, in order to allow operation with very weak energy sources. For validation purposes, three different integrated power converter and PM circuits for energy harvesting applications are presented. They have been designed for nano-power operations and single-source converters can operate with input power lower than 1 μW. The first IC is a buck-boost converter for piezoelectric transducers (PZ) implementing Synchronous Electrical Charge Extraction (SECE), a non-linear energy extraction technique. Moreover, Residual Charge Inversion technique is exploited for extracting energy from PZ with weak and irregular excitations (i.e. lower voltage), and the implemented PM policy, named Two-Way Energy Storage, considerably reduces the start-up time of the converter, improving the overall conversion efficiency. The second proposed IC is a general-purpose buck-boost converter for low-voltage DC energy sources, up to 2.5 V. An ultra-low-power MPPT circuit has been designed in order to track variations of source power. Furthermore, a capacitive boost circuit has been included, allowing the converter start-up from a source voltage VDC0 = 223 mV. A nano-power programmable linear regulator is also included in order to provide a stable voltage to the load. The third IC implements an heterogeneous multisource buck-boost converter. It provides up to 9 independent input channels, of which 5 are specific for PZ (with SECE) and 4 for DC energy sources with MPPT. The inductor is shared among channels and an arbiter, designed with asynchronous logic to reduce the energy consumption, avoids simultaneous access to the buck-boost core, with a dynamic schedule based on source priority.

In this thesis integration of high temperature superconductor technology in the future advanced power system will be investigated. In particular, superconducting magnetic energy storage system (SMES) for power quality of distribution grid and customer protection will be discussed. The complete design method, including the magnet and power electronic interface design will be discussed in more details. The method will be applied to the design of an industrial scale SMES system. Commercially available high temperature superconductor (HTS) material (YBCO) and magnesium diboride (MgB2) tapes will be considered for the design of the magnet. A multifunctional control algorithm for compensating voltage sag and improving power quality will be implemented, and the advantages of the SMES system and utilized control algorithm for this application will be illustrated. As a second part of the thesis, high temperature superconducting DC (HTS-DC) cables for transmission and distribution will be introduced. A method for both electromagnetic and thermo fluid-dynamic design of power cable will be developed. As a first case study superconducting DC collector grid for offshore wind-park will be technically and economically evaluated and the cost and loss model of the system will be discussed. Also, the transient behavior of the high temperature superconducting DC cable in high voltage DC (HVDC) system, which is crucial for stability, will be evaluated. Both line commutated converters (LCC) and voltage source converters (VSC) will be considered.

Master of Science
Department of Mechanical and Nuclear Engineering
Hitesh Bindra
Storing excess thermal energy in a storage media that can later be extracted during peak-load times is one of the better economical options for nuclear power in future. Thermal energy storage integration with light water-cooled and advanced nuclear power plants is analyzed to assess technical feasibility of different storage media options. Various choices are considered in this study; molten salts, synthetic heat transfer fluids, and packed beds of solid rocks or ceramics. In-depth quantitative assessment of these integration possibilities are then analyzed using exergy analysis and energy density models. The exergy efficiency of thermal energy storage systems is quantified based on second law thermodynamics. The packed bed of solid rocks is identified as one of the only options which can be integrated with upcoming small modular reactors. Directly storing thermal energy from saturated steam into packed bed of rocks is a very complex physical process due to phase transformation, two phase flow in irregular geometries and percolating irregular condensate flow. In order to examine the integrated physical aspects of this process, the energy transport during direct steam injection and condensation in the dry cold randomly packed bed of spherical alumina particles was experimentally and theoretically studied. This experimental setup ensures controlled condensation process without introducing significant changes in the thermal state or material characteristics of heat sink. Steam fronts at different flow rates were introduced in a cylindrical packed bed and thermal response of the media was observed. The governing heat transfer modes in the media are completely dependent upon the rate of steam injection into the system. A distinct differentiation between the effects of heat conduction and advection in the bed were observed with slower steam injection rates. A phenomenological semi-analytical model is developed for predicting quantitative thermal behavior of the packed bed and understanding physics. The semi-analytical model results are compared with the experimental data for the validation purposes. The steam condensation process in packed beds is very stable under all circumstances and there is no effect of flow fluctuations on thermal stratification in packed beds. With these experimental and analytical studies, it can be concluded that packed beds have potential for thermal storage applications with steam as heat transfer fluid. The stable stratification and condensation process in packed beds led to design of a novel passive safety heat removal system for advanced boiling water reactors.

Tato práce se zabývá vývojem nezávislého elektrického zdroje pro moderní nízkopříkonové elektrické aplikace. Protože tradiční řešení napájení drobných spotřebičů s využitím baterií či akumulátorů snižuje uživatelský komfort kvůli potřebě pravidelné údržby, navrhovaný zdroj využívá principu energy harvesting. Tento princip spočívá v získávání energie přímo z okolního prostředí napájené aplikace a její přeměně na energii elektrickou, která je dále využita pro na-pájení moderních MEMS (mikroelektromechanických) zařízení. Potenciální aplikací vyvíjeného zdroje je především moderní nositelná elektronika a biomedicínské senzory. Tato oblast využití ovšem klade zvýšené nároky na parametry generátoru, který musí zajistit dostatečný generovaný výkon z energie, dostupné v okolí lidského těla, a to při zachování prakticky využitelné velikosti a hmotnosti. Po stanovení předběžných požadavků a provedení analýz vhodnosti dostupných zdrojů energie ke konverzi byla k využití vybrána kinetická energie lidských aktivit. Byla provedena série měření zrychlení na lidském těle, především v místě předpokládaného umístění generátoru, aby bylo možno analyzovat a generalizovat hodnoty energie dostupné ke konverzi v daném umístění. V návaznosti na tato měření a analýzy byl vyvinut inovativní kinetický energy harvester, který byl následně vyroben jako funkční vzorek. Tento vzorek byl pak testován v reálných podmínkách pro verifikaci simulačního modelu a vyhodnocení reálné použitelnosti takového zařízení. Kromě samotného vývoje generátoru je v práci popsán i originální způsob zvýšení generovaného výkonu pro kinetické energy harvestery a jsou prezentována statistická data a modely pro predikci využitelnosti kinetických harvesterů pro získávání energie z lidské aktivity.

This dissertation contributes to the problem description of managing power and energy of multiple energy sources for electric vehicle power system architectures. The area of power and energy management in the application domain of electric vehicles is relatively new and encompasses several different disciplines. Primarily, the challenges in electric vehicles having multiple energy storage systems lies in managing the energy expenditure, determining the proportional power splits and establishing methods to interface between the energy systems so as to meet the demands of the vehicle propulsion and auxiliary load requirements. In this work, an attempt has been made to provide a new perspective to the problem description of electric vehicle power and energy management. The overall approach to the problem borrows from the basic principles found in conventional management methodology. The analogy between well-known hierarchical management concepts and power and energy management under timing constraints in a general task-graph is exploited to form a well-defined modular power and energy management implementation structure. The proposed methodology permits this multidisciplinary problem to be approached systematically. The thesis introduces a modular power and energy management system (MPEMS). Operation of the M-PEMS is structured as tri-level hierarchical process shells. An Energy Management Shell (EMS) handles the long-term decisions of energy usage in relation to the longitudinal dynamics of the vehicle while processes within a Power Management Shell (PMS) handles the fast decisions to determine power split ratios between multiple energy sources. Finally, a Power Electronics Shell (PES) encompasses the essential power interfacing circuitry as well as the generation of low-level switching functions. This novel framework is demonstrated with the implementation of a power and energy management system for a dual-source electric vehicle powered by lead acid batteries and ultracapacitors. A series of macro simulations of the energy systems validated against practical tests were performed to establish salient operating parameters. These parameters were then applied to the M-PEMS design of a demonstrator vehicle to determine both the general effectiveness of a power and energy management scheme and to support the validity of the new framework. Implementation of the modular blocks that composes the entire system architecture is described with emphasis given to the power electronics shell infrastructure design. The modular structure approach is design-implementation oriented, with the objective of contributing towards a more unified description of the electric vehicle power and energy management problem.

The energy and power used at various areas like households and industries is increasing gradually due to many reasons and there is a need to sustain it. This project introduces a method to reduce the energy used in a household by considering the energy sources and the amount of energy used by the appliances concurrently. Modules are used to measure and check the energy utilized by the appliances using ZigBee. Energy is generated on a conventional basis using three sources: solar panel, wind mill and conventional power. An inverter and a battery are used to connect these sources to a grid. When a device is connected, the units of power consumed are computed and shown on the LCD using LPC2148 microcontroller. The output of the battery is connected to the controller, which shows the voltage of the battery and also selects the best source to be used. Modules use a 5V supply and the controller uses 3.3V power supply. Voltage is controlled with the help of a 7805 voltage regulator and the output of transformer is revised by a rectifier.

This dissertation contributes to the problem description of managing power and energy of multiple energy sources for electric vehicle power system architectures. The area of power and energy management in the application domain of electric vehicles is relatively new and encompasses several different disciplines. Primarily, the challenges in electric vehicles having multiple energy storage systems lies in managing the energy expenditure, determining the proportional power splits and establishing methods to interface between the energy systems so as to meet the demands of the vehicle propulsion and auxiliary load requirements. In this work, an attempt has been made to provide a new perspective to the problem description of electric vehicle power and energy management. The overall approach to the problem borrows from the basic principles found in conventional management methodology. The analogy between well-known hierarchical management concepts and power and energy management under timing constraints in a general task-graph is exploited to form a well-defined modular power and energy management implementation structure. The proposed methodology permits this multidisciplinary problem to be approached systematically. The thesis introduces a modular power and energy management system (MPEMS). Operation of the M-PEMS is structured as tri-level hierarchical process shells. An Energy Management Shell (EMS) handles the long-term decisions of energy usage in relation to the longitudinal dynamics of the vehicle while processes within a Power Management Shell (PMS) handles the fast decisions to determine power split ratios between multiple energy sources. Finally, a Power Electronics Shell (PES) encompasses the essential power interfacing circuitry as well as the generation of low-level switching functions. This novel framework is demonstrated with the implementation of a power and energy management system for a dual-source electric vehicle powered by lead acid batteries and ultracapacitors. A series of macro simulations of the energy systems validated against practical tests were performed to establish salient operating parameters. These parameters were then applied to the M-PEMS design of a demonstrator vehicle to determine both the general effectiveness of a power and energy management scheme and to support the validity of the new framework. Implementation of the modular blocks that composes the entire system architecture is described with emphasis given to the power electronics shell infrastructure design. The modular structure approach is design-implementation oriented, with the objective of contributing towards a more unified description of the electric vehicle power and energy management problem.

A novel probabilistic method has been developed for modelling the operation of energy storage in electricity systems with significant amounts of wind and solar powered generation. This method is based on a spectral analysis of the variations of wind speed and solar irradiance together with profiles of electrical demand. The method has been embodied in two Matlab computer programs: Wind power only: This program models wind power on any time scale from seconds to years, with limited modelling of demand profiles. This program is only capable of modelling stand-alone systems, or systems in which the electrical demand is replaced by a weak grid connection with limited export capacity. 24-hours: This program models wind power, solar PV power and electrical demand, including seasonal and diurnal effects of each. However, this program only models store cycle times (variations within a time scale) of 24 hours. This program is capable of modelling local electrical demand at the same time as a grid connection with import or export capacity and a backup generator. Each of these programs has been validated by comparing its results with those from a time step program, making four Matlab programs in total. All four programs calculate the power flows to and from the store, satisfied demand, unsatisfied demand and curtailed power. The programs also predict the fractions of time that the store spends full, empty, filling or emptying. The results obtained are promising. Probabilistic program results agree well with time step results over a wide range of input data and time scales. The probabilistic method needs further refinement, but can be used to perform initial modelling and feasibility studies for renewable energy systems. The probabilistic method has the advantage that the required input data is less, and the computer run time is reduced, compared to the time step method.

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2006.
Thesis Advisor(s): Sherif Michaels. "June 2006." Includes bibliographical references (p. 119-124). Also available in print.