Dissertations / Theses on the topic 'Distributed Solar Power'

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010.<br>Committee Chair: Mayor, James Rhett; Committee Member: Garimella, Srinivas; Committee Member: Jeter, Sheldon. Part of the SMARTech Electronic Thesis and Dissertation Collection.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California<br>This student paper was produced as part of the team design competition in the University of Arizona course ECE 485, Radiowaves and Telemetry. It describes the design of a telemetry system for the University of Arizona’s Daedalus solar car. This is a distributed, low-power, telemetry-on-demand system that solves many of the problems typically encountered in this specialized telemetry application. The topology of the distributed microcontroller system is shown, as are optimal command and data packet structures. Also featured is a high-gain, low profile antenna system designed specifically for the solar car. Additionally, a customized chase car operator interface is illustrated.

The needs to the sustainable development of electricity, energy efficiency improvement, and environment pollution reduction have favored the development of distributed generation (DG). But the problems come with increasing DG penetration in distribution networks. This thesis presents the Solar Energy Grid Integration System (SEGIS) Stage III project done by Portland General Electric (PGE), Advanced Energy, Sandia National Lab on a PGE selected distribution feeder. The feeder has six monitored commercial solar PV systems connected. The total power output from the PV systems has the potential to reach 30% of the feeder load. The author analyzes the performance of the solar feeder on both generation and voltage effects. As a project report, it introduced a new islanding detection done by other team members to give an islanding solution of future high penetration distribution networks. At last, the author describes micro-grid and grid support concepts in a SEGIS concept paper with some examples.

As California continues to integrate more renewable energy into its electrical system, the state has experienced a corresponding rise in photovoltaic system installations. PV arrays are a unique source of power generation in that they are affected by the location of the sun, shading, and temperature changes. These characteristics make solar one of the most highly variable forms of renewable energy. In order to improve solar power’s consistency, PV systems require a supplemental source of power. The primary focus of this paper is to determine if distributed energy storage systems can be used to reduce the effect of solar intermittency. This paper examines the test data and system specifications of an experimental DESS. The benefits of using a DESS in a PV system are further studied using computer simulation modeling. This paper also shows through computer simulations how a maximum power point tracker can increase a PV array’s power output. The results of this thesis demonstrate that DESS’s are capable of smoothing out highly variable load profiles caused by intermittent solar power.

With an increasing interest for renewable power, photovoltaics (PV) have becomemore and more common in the distribution network. If a customer wants to install aPV system, or another type of distributed generation (DG), the distribution systemoperators (DSO) needs a good way to determine if it the grid can handle it or not. InSweden, a guideline to aid the DSO was published in 2011. However, this guidelineonly considers one connection without considering other DG units. This project isabout developing new guidelines for DG connections in grids with a large number ofDG units. Based on a literature study it has been concluded that one of the mostcritical issue is over-voltage, which is the main focus of this project. Two new methods have been developed; the first proposed method is based onneglecting reactance and losses in the grid, a simple linear relationship between thevoltage level, the resistance in the lines, and the installed power is obtained. Thisrelationship is then used to calculate the voltage level at critical points in the grid. Thesecond method is to find the weakest bus, with a connected DG unit. By assumingthat all power is installed at that point we get a very simple guideline; it is veryconservative but can be used before the first method. A simulation tool has been developed in order to analyze the voltage level in grids forvarious cases with connected DG units. The simulated results have proven that theproposed guidelines are, when considering voltage issues, very reliable and can beuseful. However, further work needs to be done to ensure that other problems donot occur.

Renewable energy is considered to be one of the most promising alternatives for the growing energy demand in response to depletion of fossil fuels and undesired global warming issue. With such perspective, Solar Cells and Fuel Cells are most viable, environmentally sound, and sustainable energy sources for power generation. Solar and Fuel cells have created great interests in modern applications including distributed energy generation to provide clean energy. The purpose of this thesis was to perform a detailed analysis and modeling of Solar and Fuel cells using Cadence SPICE, and to investigate dynamic interactions between the modules and power conversion circuits. Equivalent electronic static and dynamic models for Solar and Fuel Cells, their electrical characteristics, and typical power loss mechanisms associated with them are demonstrated with simulation results. Power conversion circuits for integration with the dynamic models of these renewable low voltage sources are specifically chosen to boost and regulate the input low dc voltage from the modules. The scope of this work was to analyze and model solar and fuel cells to study their terminal characteristics, power loss mechanisms, modules and their dynamics when interfaced with power converters, which would lead to better understanding of these renewable sources in power applications.<br>M.S.<br>School of Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Electrical Engineering MSEE

The yield from a solar photovoltaic (PV) source is dependent on factors such as light and temperature. A control system called a maximum power point tracker (MPPT) ensures that the yield from a solar PV source is maximized in spite of these factors. This thesis presents a novel implementation of a perturb and observe (PO) MPPT. The implementation uses a switched capacitor step down converter and a custom digital circuit implementation of the PO algorithm. Working in tandem, the switched capacitor step down converter and the custom digital circuit implementation were able to successfully track the maximum power point of a simulated solar PV source. This implementation is free of the overhead encountered with general purpose processor based MPPT implementations. This makes this MPPT system a valid candidate for applications where general purpose processors are undesirable. This document will begin by discussing the current state of MPPT research. Afterward, this thesis will present studies done to be able to use the chosen switched capacitor step down converter. Then the digital circuit PO implementation will be discussed in detail. Simulations of the architecture will be presented. Finally, experimental validation using a hardware prototype will be shown.

The following report is conducted as a feasibility study, aimed to objectively uncover the advantages and challenges of increasing the amount of small scale solar power in Sri Lanka. The demand for electricity in Sri Lanka has been steadily increasing the last few years and there is an urgent need to find new ways of generating electricity. To not further increase the already high dependency of foreign oil and to decrease the impact on the environment, a transition from traditional combustion of fossil fuel to new renewable energy is required. The report shows that there exists substantial potential for generating solar energy in Sri Lanka. Calculations show that an investment in a photovoltaic system can be economically favourable and that the investment often is paid back within a few years. Current regulations and electricity pricing increases the economic incitement for high electricity consumers to invest in small scale solar power. Furthermore, the report demonstrates that there are likely no technical obstacles of increasing small scale solar power at this period. In contrary, the report shows that small scale solar power in general decreases line losses, voltage drops, and the peak demand of electricity. At present, it is probably not the lack of economic incitement but rather socio-economic factors that limit the development of small scale solar power. Sri Lanka is still a relatively poor country and the long years of civil war have prevented development and wealth. Lack of funds and a high ratio of low-income earners are probably the main reason for the slow development

Among the many renewable energy sources, solar power is becoming one of the quickest to be adopted due to continuous technological progress and reductions in cost. Today's typical photovoltaic modules that are connected together in series and parallel to form strings and sub-arrays. Various distributed photovoltaic architectures are introduced in this thesis and DC-DC converters with maximum power point tracking are also introduced. Partial power processing is a technique to allow only a fraction of the power to be processed by the DC-DC converter, thereby reducing losses and improving efficiency. A new partial power isolated DC-DC converter is proposed in this thesis. The converter features maximum power point tracking and its controller selectively engages the buck portion or the boost portion or both in response to the maximum power point tracking input signal to achieve the desired output voltage and maximum power. With series connected DC-DC converters, each DC-DC converter carries an equal string current and adjusts its output voltage proportional to the available power of the connected photovoltaic module. The proposed topology allows each photovoltaic module to operate at its own maximum power point under varying or mismatched solar irradiance conditions, yet keep the total DC string voltage constant. The proposed circuit is verified using PLECS simulation software. In comparison to the existing circuit with partial power processing method, the proposed circuit overcomes the disadvantage that the output voltage can only be greater than the input voltage. With the two metal oxide semi-conductor field effect transistors added in series with the diodes in the secondary side of the transformer, the new circuit operates at a 100kHZ switching frequency and is able to perform both step up and step down modes with a properly designed control block. As a result, the circuit can convert a voltage from a PV panel that is higher or lower than the output to a regulated DC output voltage.<br>Applied Science, Faculty of<br>Engineering, School of (Okanagan)<br>Graduate

Grid-connected photovoltaic (PV) capacity is increasing worldwide, mainly due to extensive subsidy schemes for renewable electricity generation. A majority of newly installed systems are distributed small-scale systems located in distribution grids, often at residential customers. Recent developments suggest that such distributed PV generation (PV-DG) could gain more interest in Sweden in the near future. With prospects of decreasing system prices, an extensive integration does not seem impossible. In this PhD thesis the opportunities for utilisation of on-site PV generation and the consequences of a widespread introduction are studied. The specific aims are to improve modelling of residential electricity demand to provide a basis for simulations, to study load matching and grid interaction of on-site PV and to add to the understanding of power system impacts. Time-use data (TUD) provided a realistic basis for residential load modelling. Both a deterministic and a stochastic approach for generating different types of end-use profiles were developed. The models are capable of realistically reproducing important electric load properties such as diurnal and seasonal variations, short time-scale fluctuations and random load coincidence. The load matching capability of residential on-site PV was found to be low by default but possible to improve to some extent by different measures. Net metering reduces the economic effects of the mismatch and has a decisive impact on the production value and on the system sizes that are reasonable to install for a small-scale producer. Impacts of large-scale PV-DG on low-voltage (LV) grids and on the national power system were studied. Power flow studies showed that voltage rise in LV grids is not a limiting factor for integration of PV-DG. Variability and correlations with large-scale wind power were determined using a scenario for large-scale building-mounted PV. Profound impacts on the power system were found only for the most extreme scenarios.<br>Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 711

This thesis provides a tool to determine the maximum capacity, of a given power grid, when connecting distributed photovoltaic parks including the optimal allocation of the parks taking the power grid configuration into account. This tool is based on a computational model that evaluates the hosting capacity of the given grid through power flow simulations. The tool also integrates a geographic information system that links suitable land areas to nearby substations that can host photovoltaic parks. The mathematical model was tested on different cases in the municipality of Herrljunga, Sweden, where it was determined to be possible to connect 47 photovoltaic parks of 1MWp to the power grid as well as the most appropriate substations to allocate them to without the need for grid reinforcements. Additionally, the concept of grid cost allocation is presented and briefly discussed while analysing the results in relation to national energy targets.

Favorable price trends and increasing demand for renewable energy sources portend accelerating integration of solar photovoltaic (PV) generation into traditional electric power system networks. Managing the variable output of massive PV resources makes system frequency regulation more complex and expensive. ISOs must procure additional regulation and load following capacity, while power plants must supply more regulation work. In contrast to costly physical storage solutions, this thesis proposes to address the issue by reconfiguring the electricity market pricing structure to translate all power imbalances into real-time market price signals. More accurately determining the instantaneous value of energy, electric power markets could reward participants who can quickly respond to frequency fluctuations. By utilizing short term forward markets to monetize the risk associated with intermittency, the true cost of reliability is determined and could reduce wasteful capacity payments. This market redesign is an ideal open platform for disparate smart grid technologies which could encourage all suppliers, loads and generator, to offer supply or reduce consumption when it is needed most and could vastly improve frequency performance metrics.

More efficient technologies, state laws as well as environmental, social, and political pressures have all contributed to placing solar acquisition on the agenda for California’s public entities over the last half decade. But a key question for these frequently cash-strapped jurisdictions is how to utilize public dollars and lands, and how to leverage incentives to obtain solar PVs. As an alternative to outright purchase, a promising financing option made available to jurisdictions in recent years is ownership by a third party, usually the solar company, including various forms of Power Purchase Agreements (PPA’s) and leasing. Due in part to state and federal incentives available between 2007 and 2012, these third-party provider (TPP) options have been used with increasing frequency; TPP arrangements accounted for “virtually all” larger and mid-size non-residential installations in 2008 (Sherwood 2008). A number of California’s early adopters of third-party financing have installations that have now been operational for several years. Consequently, there is a new opportunity to evaluate third-party financing effectiveness. This thesis reviews solar acquisition practices in California over the last six years, comparing financing options through document analysis and feedback from jurisdiction staff. It finds that directly buying installations has provided a slight advantage in direct savings and overall satisfaction for jurisdictions on average, but success generally depends upon the jurisdiction having secured upfront capital, usually from successfully accessing very low-interest loans or large grants. TPP projects have provided a good alternative to direct purchase, resulting in significant savings and positive reviews from jurisdictions, allowing them to invest in larger installation sizes, and to meet local policy goals or mandates. Additionally, this thesis makes observations about the limitations for installation sizing, impacts of siting on savings, tips for selecting a solar installer, the benefits of cooperative procurement arrangements, and the relative importance of existing and expired monetary incentives available for solar from 2006 through 2020.

Orientador: Ennio Peres da Silva<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica<br>Made available in DSpace on 2018-08-27T02:08:03Z (GMT). No. of bitstreams: 1 Castro_RodolfoDamasiode_M.pdf: 3152478 bytes, checksum: a4e0e80e4ac1f8804a7b3aa8589139b4 (MD5) Previous issue date: 2015<br>Resumo: A busca por meios de geração de energia para atender às necessidades humanas com menores impactos sociais e ambientais é constante. A geração de energia elétrica por meio de fontes renováveis na forma distribuída, ou não centralizada, é um meio ou método de minimizar tais impactos. O objetivo da pesquisa foi analisar a viabilidade econômica, frente a tarifa de energia elétrica das concessionárias locais, da utilização de sistemas de geração solar em residências brasileiras situadas nas capitais dos estados, na capital federal, Brasília e na cidade de Campinas (SP). Diferentes situações de dimensionamento foram utilizadas para dois tipos de sistemas: um sistema fotovoltaico puro, para atender toda a necessidade energética da residência, incluindo o chuveiro elétrico, e um sistema solar híbrido, composto por aquecimento solar para atender a demanda por água quente no banho em conjunto com geração fotovoltaica para atender as necessidades em equipamentos elétricos. As situações de dimensionamento utilizadas foram três, onde em cada uma o sistema fotovoltaico foi projetado para uma determinada produção de energia. Os sistemas fotovoltaico e de aquecimento solar foram dimensionados com o auxílio dos softwares PVSyst e Dimensol, respectivamente. O custo total dos sistemas foi estimado a partir de pesquisa em lojas com endereço eletrônico na rede de computadores e de orçamentos fornecidos por empresas do ramo. Determinou-se o preço final da energia elétrica convencional para todas as cidades a partir da tarifa definida pela ANEEL, do valor médio do PIS efetivo cobrado pelas concessionárias e da alíquota de ICMS que os governos estaduais recolhem. Após realizados os cálculos, chegou-se ao resultado de que somente nas cidades de Macapá (AP) e Boa Vista (RR), devido principalmente ao baixo custo das tarifas de energia elétrica, o usuário não economizaria com a instalação dos sistemas. Porém, em cidades de elevada tarifa, como Belém (PA) e Belo Horizonte (MG), o usuário pagaria cerca de R$ 0,30 por quilowatt hora consumido a menos<br>Abstract: The search for power generation means to meet human needs with lower social and environmental impacts is constant. The distributed generation of electricity by renewable energies is a method to minimize those impacts. The research aimed to analyze the economic viability against local electricity tariff of the use of solar power generation systems in Brazilian households located in the capitals of the states, in the federal capital, Brasilia, and in the city of Campinas (SP) Different sizing situations were used for two types of systems: a pure PV system to meet all the energy needs of the residence, including electric shower, and a hybrid solar system, consisting of solar heating to meet the demand for hot water in the bath together with photovoltaic generation to meet the needs in electrical equipment. Sizing situations used were three, where in each one the PV system is designed for a certain production of energy. The photovoltaic systems and solar heating were sized with the help of the softwares PVSyst and Dimensol, respectively. The total cost of the systems was estimated by a research in webstores and budgets provided by companies in the field. Was determined the final price of conventional electricity to all cities from the tariff set by ANEEL, the average value of the effective PIS charged by concessionaires and ICMS aliquot that state governments collect. After performing the calculations, came to the result that only the cities of Macapa (AP) and Boa Vista (RR), mainly due to the low cost of electricity tariffs, the user does not save due to the installation of the systems. However, in cities of high tariff, as Belém (PA) and Belo Horizonte (MG), the user would save about R$ 0.30 per quilowatt-hour<br>Mestrado<br>Planejamento de Sistemas Energeticos<br>Mestre em Planejamento de Sistemas Energéticos

Orientadores: Ernesto Ruppert Filho, Marcelo Gradella Villalva<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação<br>Made available in DSpace on 2018-08-19T00:52:44Z (GMT). No. of bitstreams: 1 Gazoli_JonasRafael_M.pdf: 7156744 bytes, checksum: 8382e373834c6001d3a70cd31e6f291f (MD5) Previous issue date: 2011<br>Resumo: Este trabalho apresenta uma contribuição à pesquisa e ao desenvolvimento de microinversores monofásicos para sistemas fotovoltaicos de energia solar conectados à rede elétrica de baixa tensão. O objetivo principal da pesquisa é apresentar o projeto, a construção e os resultados experimentais de um microinversor eletrônico que processa a energia proveniente de um painel fotovoltaico e faz a conexão deste dispositivo com a rede El. São apresentados estudos teóricos e simulações sobre painéis fotovoltaicos, sobre a modelagem e o controle de conversores eletrônicos e sobre o algoritmo de rastreamento do ponto de máxima potência. São apresentados resultados experimentais obtidos com um microinversor experimental desenvolvido em laboratório, constituído de dois estágios de conversão (CC-CC e CC-CA)<br>Abstract: This thesis presents a contribution to research and development of single-phase micro-inverters for low voltage grid-connected photovoltaic systems. The main goal of this research is to present the project, the development and experimental results of an electronic micro-inverter that processes the energy from a photovoltaic panel and connects this device to the main grid. Theoretical studies and simulations on photovoltaic panels are shown, as the modeling and control of the electronic converters and the maximum power point tracking algorithm. Results with an experimental microinverter consisting of two stages (DC-DC and DC-AC) are also shown<br>Mestrado<br>Energia Eletrica<br>Mestre em Engenharia Elétrica

A Geração Distribuída no Brasil tem crescido ao longo dos anos, especialmente na fonte fotovoltaica e na categoria que a ANEEL denomina microgeração distribuída, que são centrais geradoras de energia elétrica com potência instalada menor ou igual a 75 kW e conectada na rede de distribuição por meio de instalações de unidades consumidoras. Apesar dos problemas tradicionais que podem ocorrer com a inserção em larga escala, como maiores perdas e desvios de tensão, as placas fotovoltaicas, conectadas à rede de distribuição por meio de um inversor, trazem a possibilidade de controlar a tensão no ponto de conexão, manipulando-se o fator de potência de saída do inversor, controlando a potência reativa. Neste contexto, considerando o uso dos inversores inteligentes com possibilidade de envio de sinal remotamente ao operador e a possibilidade de criação de Centros de Despacho de Geração Distribuída (CDGD), este trabalho tem por objetivo propor uma metodologia de regulação de tensão centralizada utilizando unidades de microgeração fotovoltaicas, em redes de distribuição com larga inserção. A metodologia proposta utiliza o conceito de despacho de potência reativa e fluxo de potência reativa ótimo, por meio de uma abordagem centralizada da rede, utilizando-se o software OpenDSS e MatLab, equipado com Algoritmo Genético (AG) para solucionar o problema de otimização. Para avaliar o desempenho do modelo, foram feitos estudos de caso no sistema IEEE 123 barras e em uma rede real em Alegrete. Os resultados obtidos validam a abordagem proposta, demonstra a aplicabilidade e limitações em casos reais.<br>The distributed generation in Brazil has increased in the past years, specially in photovoltaic power generation, at the category that Brazilian Electric Regulator ANEEL classifies as "distributed micro-generation", i.e., generation units in which the active power capacity is equal or bellow 75kW and conected on distribution network by the consumers. Despite the traditional problems that might occur due to high penetration of the units, e.g., higher losses and voltage sags and swells, they are conected to the network through an inverter that can be controlled in order to provide or consume reactive power, providing voltage regulation. In that context, considering the use of intelligent inverters that can be remotely operated by a centralized utility operator, this work aims to propose a centralized voltage regulation methodology using distributed micro-generation in distribution networks. The proposed methodology uses the concept of reactive power dispatch and optimal power flow, from a centralized view of the network, using the software MatLab and OpenDSS with Genetic Algorithm to solve the optimization problem. To evaluate the model, simulations were performed with the IEEE 123 bus system and with a real distribution network from the Alegrete city, in the Brazilian state of Rio Grande do Sul. The results show the proposed is valid, despite some limitations on real cases.

Solar PV-based distributed generation has increased significantly over the last few years, and the rapid growth is expected to continue in the foreseeable future. As the penetration levels of distributed generation increase, power systems will become increasingly decentralized with bi-directional flow of electricity between the transmission and distribution networks. To manage such decentralized power systems, planners and operators need models that accurately reflect the structure of, and interactions between the transmission and distribution networks. Moreover, algorithms that can simulate the steady state and dynamics of power systems using these models are also needed. In this context, integrated transmission and distribution system modeling and simulation has become an important research area in recent years, and the primary focus so far has been on studying the steady state response of power systems using integrated transmission and distribution system models. The primary objective of this dissertation is to develop an analysis approach and a program that can simulate the dynamics of three phase, integrated transmission and distribution system models, and use the program to demonstrate the advantages of evaluating the impact of solar PV-based distributed generation on power systems dynamics using such models. To realize this objective, a new dynamic simulation analysis approach is presented, the implementation of the approach in a program is discussed, and verification studies are presented to demonstrate the accuracy of the program. A new dynamic model for small solar PV-based distributed generation is also investigated. This model can interface with unbalanced networks and change its real power output according to the incident solar irradiation. Finally, application of the dynamic simulation program for evaluating the impact of solar PV units using an integrated transmission and distribution system model is discussed. The dissertation presents a new approach for studying the impact of solar PV-based distributed generation on power systems dynamics, and demonstrates that the solar PV impact studies performed using the program and integrated transmission and distribution system models provide insights about the dynamic response of power systems that cannot be obtained using traditional dynamic simulation approaches that rely on transmission only models.<br>Ph. D.

The global market for photovoltaics (PV) has increased rapidly: during 2014, 44 times more was installed than in 2004, partly due to a price reduction of 60-70% during the same time period. Economic support schemes that were needed to make PV competitive on the electricity market have gradually decreased and self-consumption of PV electricity is becoming more interesting internationally from an economic perspective. This licentiate thesis investigates self-consumption of residential PV electricity and how more PV power can be allowed in and injected into a distribution grid. A model was developed for PV panels in various orientations and showed a better relative load matching with east-west-oriented compared to south-oriented PV panels. However, the yearly electricity production for the east-west-system decreased, which resulted in less self-consumed electricity. Alternatives for self-consumption of PV electricity and reduced feed-in power in a community of detached houses were investigated. The self-consumption increased more with shared batteries than with individual batteries with identical total storage capacity. A 50% reduction in feed-in power leads to losses below 10% due to PV power curtailment. Methodologies for overvoltage prevention in a distribution grid with a high share of PV power production were developed. Simulations with a case with 42% of the yearly electricity demand from PV showed promising results for preventing overvoltage using centralized battery storage and PV power curtailment. These results show potential for increasing the self-consumption of residential PV electricity with storage and to reduce stress on a distribution grid with storage and power curtailment. Increased self-consumption with storage is however not profitable in Sweden today, and 42% of the electricity from PV is far more than the actual contribution of 0.06% to the total electricity production in Sweden in 2014.

This thesis has contributed to the design of suitable decision-making techniques for energy management in the smart grid with emphasis on energy efficiency and uncertainty analysis in two smart grid applications. First, an energy trading model among distributed microgrids (MG) is investigated, aiming to improve energy efficiency by forming coalitions to allow local power transfer within each coalition. Then, a more specific scenario is considered that is how to optimally schedule Electric Vehicles (EV) charging in a MG-like charging station, aiming to match as many as EV charging requirements with the uncertain solar energy generation. The solutions proposed in this thesis can give optimal coalition formation patterns for reduced power losses and achieve optimal performance for the charging station. First, several algorithms based on game theory are investigated for the coalition formation of distributed MGs to alleviate the power losses dissipated on the cables due to power transfer. The seller and buyer MGs can make distributed decisions whether to form a coalition with others for energy trading. The simulation results show that game theory based methods that enable cooperation yield a better performance in terms of lower power losses than a non-cooperative approach. This is because by forming local coalitions, power is transferred within a shorter distance and at a lower voltage. Thus, the power losses dissipated on the transmission lines and caused by power conversion at the transformer are both reduced. However, the merge-and-split based cooperative games have an inherent high computational complexity for a large number of players. Then, an efficient framework is established for the power loss minimization problem as a college admissions game that has a much lower computational complexity than the merge-and-split based cooperative games. The seller and buyer MGs take the role of colleges and students in turn and apply for a place in the opposite set following their preference lists and the college MGs’ energy quotas. The simulation results show that the proposed framework demonstrates a comparable power losses reduction to the merge-and-split based algorithms, but runs 700 and 18000 times faster for a network of 10 MGs and 20 MGs, respectively. Finally, the problem of EV charging using various energy sources is studied along with their impact on the charging station’s performance. A multiplier k is introduced to measure the effect of solar prediction uncertainty on the decision-making process of the station. A composite performance index (the Figure of Merit, FoM) is also developed to measure the charging station’s utility, EV users charging requirements and the penalties for turning away new arrivals and for missing charging deadlines. A two-stage admission and scheduling mechanism is further proposed to find the optimal trade-off between accepting EVs and missing charging deadlines by determining the best value of the parameter k under various energy supply scenarios. The numerical evaluations give the solution to the optimization problem and show that some of the key factors such as shorter and longer deadline urgencies of EVs charging requirements, stronger uncertainty of the prediction error, storage capacity and its initial state will not affect significantly the optimal value of the parameter k.

Home energy management systems (HEMS) technology can provide a smart and efficient way of optimising energy usage in residential buildings. One of the main goals of the Smart Grid is to achieve Demand Response (DR) by increasing end users’ participation in decision making and increasing the level of awareness that will lead them to manage their energy consumption in an efficient way. This research presents an intelligent HEMS algorithm that manages and controls a range of household appliances with different demand response (DR) limits in an automated way without requiring consumer intervention. In addition, a novel Multiple Users and Load Priority (MULP) scheme is proposed to organise and schedule the list of load priorities in advance for multiple users sharing a house and its appliances. This algorithm focuses on control strategies for controllable loads including air-conditioners, dishwashers, clothes dryers, water heaters, pool pumps and electrical vehicles. Moreover, to investigate the impact on efficiency and reliability of the proposed HEMS algorithm, small-scale renewable energy generation facilities and energy storage systems (ESSs), including batteries and electric vehicles have been incorporated. To achieve this goal, different mathematical optimisation approaches such as linear programming, heuristic methods and genetic algorithms have been applied for optimising the schedule of residential loads using different demand side management and demand response programs as well as optimising the size of a grid connected renewable energy system. Thorough incorporation of a single objective optimisation problem under different system constraints, the proposed algorithm not only reduces the residential energy usage and utility bills, but also determines an optimal scheduling for appliances to minimise any impacts on the level of consumer comfort. To verify the efficiency and robustness of the proposed algorithm a number of simulations were performed under different scenarios. The simulations for load scheduling were carried out over 24 hour periods based on real-time and day ahead electricity prices. The results obtained showed that the proposed MULP scheme resulted in a noticeable decrease in the electricity bill when compared to the other scenarios with no automated scheduling and when a renewable energy system and ESS are not incorporated. Additionally, further simulation results showed that widespread deployment of small scale fixed energy storage and electric vehicle battery storage alongside an intelligent HEMS could enable additional reductions in peak energy usage, and household energy cost. Furthermore, the results also showed that incorporating an optimally designed grid-connected renewable energy system into the proposed HEMS algorithm could significantly reduce household electricity bills, maintain comfort levels, and reduce the environmental footprint. The results of this research are considered to be of great significance as the proposed HEMS approach may help reduce the cost of integrating renewable energy resources into the national grid, which will be reflected in more users adopting these technologies. This in turn will lead to a reduction in the dependence on traditional energy resources that can have negative impacts on the environment. In particular, if a significant proportion of households in a region were to implement the proposed HEMS with the incorporation of small scale storage, then the overall peak demand could be significantly reduced providing great benefits to the grid operator as well as the households.

Мета роботи: підвищити ефективність управління мережею Microgrid за рахунок вдосконалення системи управління електроенергією сонячних батарей для роботи в режимі реального часу. В даній роботі наведено огляд розумних електромереж, їх роль та взаємодія з існуючими електромережами. Розглядаються різні методи та системи управління мережами MicroGrid, проводиться їх аналіз, характеристика та порівняння, надається характеристика основних рівнів керування мережею MicroGrid. Надається аналіз основних переваг управління сонячною енергією відносно інших джерел енергії в мережі MicroGrid. Досліджується алгоритм визначення положення сонця та враховується вплив погодних умов в реальному часі. Показано, що даний метод підвищує ефективність системи накопичення енергії порівняно з традиційними системами управління енергією.<br>Goal: improve the efficiency of Microgrid network management by improving the solar power management system for real time operation. This paper provides an overview of smart grids, their role and interaction with existing grids. It discusses the various methods and systems for managing the MicroGrid network, analyzes, characterizes, and compares them, and describes the main layers of MicroGrid network management. The main advantages of solar energy management over other sources of energy in the MicroGrid network are analyzed. The algorithm for determining the position of the sun is investigated and the influence of real-time weather conditions is taken into account. It is shown that this method increases the efficiency of the energy storage system in comparison with traditional energy management systems.

Orientador: Ernesto Ruppert Filho<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação<br>Made available in DSpace on 2018-08-17T05:47:06Z (GMT). No. of bitstreams: 1 Villalva_MarceloGradella_D.pdf: 10773240 bytes, checksum: aeccba84d675a257bed00100b3d011cb (MD5) Previous issue date: 2010<br>Resumo: Este trabalho é uma contribuição ao estudo de conversores eletrônicos para sistemas fotovoltaicos de geração distribuída de energia elétrica. O objetivo principal é apresentar o desenvolvimento e os resultados de um conversor eletrônico trifásico para a conexão de um conjunto de painéis solares fotovoltaicos à rede elétrica de baixa tensão. São apresentados resultados experimentais e estudos teóricos sobre a modelagem e a simulação de dispositivos fotovoltaicos, a regulação da tensão fotovoltaica, o rastreamento da máxima potência e a modelagem e o controle de um conversor eletrônico de dois estágios<br>Abstract: This work is a contribution to the study of power converters for photovoltaic distributed generation systems. The main objective is to present the development and results of a threephase power converter for a grid-connected photovoltaic plant. The work presents experimental results and theoretical studies on the modeling and simulation of photovoltaic devices, regulation of the photovoltaic voltage, maximum power point tracking, and the modeling and control of a two-stage grid-connected power converter<br>Doutorado<br>Energia Eletrica<br>Doutor em Engenharia Elétrica

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2017-12-21T17:39:10Z No. of bitstreams: 1 marianabrinatialtomar.pdf: 5565205 bytes, checksum: aed1136ebbc66049baea19e7b7da34fb (MD5)<br>Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-12-22T12:17:48Z (GMT) No. of bitstreams: 1 marianabrinatialtomar.pdf: 5565205 bytes, checksum: aed1136ebbc66049baea19e7b7da34fb (MD5)<br>Made available in DSpace on 2017-12-22T12:17:48Z (GMT). No. of bitstreams: 1 marianabrinatialtomar.pdf: 5565205 bytes, checksum: aed1136ebbc66049baea19e7b7da34fb (MD5) Previous issue date: 2017-09-01<br>A inserção de geração distribuída em sistemas de potência do mundo todo vem crescendo em ritmo acelerado nos últimos anos. Grandes investimentos em fontes limpas e renováveis, especialmente a eólica e solar, estão sendo feitos pelos países com o objetivo de minimizar os impactos ambientais causados pela geração de energia a partir de combustíveis fósseis. A conexão de uma geração distribuída utilizando fontes intermitentes pode trazer algumas vantagens para o funcionamento do sistema de distribuição, como melhora dos níveis de tensão, aumento da confiabilidade e redução de perdas elétricas. Porém, do ponto de vista do sistema de transmissão, a conexão desse tipo de geração em algumas áreas do sistema pode acabar tendo um impacto negativo em sua operação, causando variações de tensão que podem afetar alguns equipamentos da rede e aumentar a complexidade de sua operação. Além disso, deve ser avaliado seu impacto no controle de frequência de carga e controle de tensão entre outros aspectos. Desta forma, pode-se verificar que esse tipo de conexão deve ser estudado com um maior nível de profundidade. A partir deste contexto, neste trabalho serão analisados os impactos sistêmicos da conexão de uma geração solar em sistemas elétricos de potência, avaliando os níveis de perdas elétricas e variações nos níveis de tensão. Duas metodologias de solução do fluxo de potência na presença de incertezas são avaliadas. As incertezas consideradas estão nos dados de geração e também de carga do sistema. A primeira metodologia é baseada na solução do fluxo de carga determinístico sequencial ao longo da curva de carga. Para esta metodologia são consideradas curvas de carga e de geração, obtidas através do Sistema Teste de Confiabilidade IEEE24 barras e do Laboratório Solar da UFJF, respectivamente. São analisados os impactos nos níveis de perdas elétricas, assim como a variação dos níveis de tensão nas barras para diferentes situações de geração. A segunda metodologia avaliada é baseada na utilização de aritmética affine para determinação dos impactos destas incertezas. Os resultados de perdas obtidos serão tratados considerando-se o ponto médio dos intervalos para fins de comparação com outras metodologias. Os resultados das duas metodologias são comparados aos obtidos pelas Simulações de Monte Carlo, com o objetivo de serem validados.<br>The insertion of distributed generation into worldwide power systems has been increasing at a rapid pace in the last few years. Large investments in clean and renewable sources, especially wind and solar, are being made by countries to minimize the environmental impacts caused by fossil fuel power generation. Connecting a distributed generation using intermittent sources can bring some benefits for the operation of the distribution system, such as improved voltage levels, increased reliability and reduction of electrical losses. However, from the point of view of the transmission system, the connection of this type of generation in some areas of the system can end up having a negative impact on its operation, causing voltage variations which can affect network equipments and increase the operation complexity. In addition, impacts on the load frequency control and voltage control among other aspects must be evaluated. Thus, this type of connection must be studied with greater level of depth. In this context, the systemic impacts of the connection of a solar plant to electrical power systems, evaluating the levels of electrical losses and variations in voltage levels are analysed. Two methodologies for solving the power flow in the presence of uncertainties are evaluated. The uncertainties considered are the generation and system load data. The first methodology is based on sequential Newton power flow solutions along the load curve, in which load and generation curves obtained from the IEEE24 Bus Test System and from the UFJF Solar Laboratory, respectively. The impacts on the electrical losses are analyzed, as well as the variation on bus voltage levels in the bars for various generation conditions. The second methodology is based on the use of affine arithmetic to determine the impacts of these uncertainties. The results of losses obtained will be treated considering the average point of the intervals for comparisons with other methodologies. The results obtained from the two methods are compared with those obtained by the Monte Carlo Simulations, in order to validate them.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>The increased demand for energy, the possibility of reducing the supply of conventional fuels and growing concerns about the preservation of the environment have led to several researches and development of alternative energy sources which are clean, renewable and with minor environmental impact. Among the various alternative energy sources, PV solar has been considered an excellent option as it is free, abundant, clean and distributed through all places. Solar energy incident on Earth\'s surface is estimated at about ten thousand times the total energy consumed in the world. Even with all the advantages offered by the generation of energy through the use of photovoltaic panels, the initial cost of deployment is high and the efficiency of energy conversion is currently still low. Thus, it is essential to use techniques to extract the maximum power from these panels to increase the system operation efficiency. This work aims to present studies of a complete photovoltaic solar system, connected to low voltage power grid including the solar panel, a step-up voltage converter, its corresponding Maximum Power Point Tracking (MPPT) control, the voltage inverter with its control, the phase locked loop, and by means of an inductive coupling, the connection of the whole system to the grid. For modeling and simulations of the solar photovoltaic system, it was used the Alternative Transients Program - ATP. Initially it is presented simulation results with parts that comprises the PV array, and only at the end, it is performed a case study with the complete PV system developed in this work.<br>O aumento da demanda de energia, a possibilidade de redução do suprimento de combustíveis convencionais e a crescente preocupação com a preservação do meio ambiente têm levado a várias pesquisas e desenvolvimento de fontes alternativas de energia que sejam limpas, renováveis e com menor impacto ambiental. Dentre as diversas fontes alternativas de energia, a solar fotovoltaica tem sido considerada uma excelente opção já que é livre, abundante, limpa e distribuída. A energia solar incidente na superfície da Terra é estimada em cerca de dez mil vezes a energia total consumida no mundo. Mesmo com todas as vantagens apresentadas pela geração de energia por meio do uso de painéis fotovoltaicos, a eficiência da conversão de energia é atualmente ainda baixa e com custo inicial de implantação elevado. Assim, é imprescindível o uso de técnicas para extração da máxima potência destes painéis para aumentar a eficiência de operação do sistema. Este trabalho visa apresentar estudos de um sistema fotovoltaico completo conectado à rede elétrica de baixa tensão, compreendendo o painel solar, um conversor elevador de tensão, seu correspondente controle de rastreamento de máxima potência, o inversor de tensão com seu controle, a malha de captura de fase e, por meio de um indutor de acoplamento, a conexão de todo este sistema à rede elétrica. Para a modelagem e simulações do sistema solar fotovoltaico foi utilizado o Alternative Transients Program - ATP. Inicialmente são apresentados resultados de simulação de partes constituintes do arranjo fotovoltaico e somente ao final, é realizado um estudo de caso com o sistema completo desenvolvido neste trabalho.<br>Mestre em Ciências

Este trabalho objetiva contribuir com o planejamento da geração de energia elétrica por meio da utilização de geração fotovoltaica de forma distribuída, ou seja, instalada e em operação em paralelo junto com a rede de distribuição de energia elétrica. Utiliza-se uma abordagem hipotético-dedutiva, buscando hipóteses, na forma de questões orientadoras, que serão testadas por meio do tratamento dos dados coletados e sua posterior análise e interpretação. O método de procedimento é o estudo de caso, sendo escolhida a cidade de Curitiba e o restante dos municípios compreendendo sua Região Metropolitana. A partir da elaboração da revisão na literatura, visando constituir a fundamentação teórica desta pesquisa, é elaborado um breve inventário estatístico e do aspecto de geração de energia elétrica da cidade de Curitiba, no contexto do estado do Paraná. Os procedimentos metodológicos envolvem a simulação de cenários de inserção de geração fotovoltaica distribuída, considerando diferentes níveis de penetração, e seus efeitos sobre curvas de carga reais para a cidade de Curitiba. Foram selecionados 12 dias, considerados críticos, para a análise que contemplou a contribuição fotovoltaica em termos da redução do consumo de energia elétrica, redução de emissões de CO2 e, por fim, capacidade do sistema fotovoltaico em reduzir a demanda máxima do sistema elétrico. Constatou-se que o intervalo de capacidade instalada em energia solar fotovoltaica situa-se entre 40,80 MWp e 55,68 MWp, desconsiderando exceções, e remete a valores de máximo Fator Efetivo de Capacidade de Carga (FECC), para condição de irradiação máxima e irradiação típica, no inverno e verão. Dessa forma, este intervalo é considerado apropriado do ponto de vista do aumento da capacidade do sistema elétrico, devido à presença de geradores fotovoltaicos distribuídos. Além disso, o referido intervalo além de aumentar em mais de 50% a capacidade do sistema elétrico, acarreta em redução anual do consumo de energia elétrica entre 50,8 GWh e 69,4 GWh, além de evitar a emissão de 18.501 toneladas de CO2-eq a 25.251 toneladas de CO2-eq, sendo, portanto, um importante vetor para o aumento da oferta de energia elétrica, aumento da capacidade do sistema elétrico e, por fim, redução de emissões de Gases do Efeito Estufa, principalmente o CO2.<br>This study aims to deepen knowledge in the item electricity generation planning through the use of distributed generation using solar photovoltaic energy, which means that photovoltaic systems are able to operate in parallel with the electricity distribution network. A hypothetical-deductive approach was developed, seeking hypotheses in the form of guiding questions, which will be tested by treatment of the collected data and their analysis and interpretation. The method of procedure is the case study, being applied to the Metropolitan Region of Curitiba. The literature review aims to be the theoretical basis of this research, therefore it mainly consists of a brief statistical and electrical energy inventory of the city of Curitiba in Paraná state. The methodological procedures involve the simulation of different scenarios for distributed PV generators by varying their Penetration Level, so that the effects on actual load curves for the region analyzed were quantified. 12 critical days were selected to the analysis that included the photovoltaic contribution in terms of reducing electrical energy consumption, reducing CO2 emissions and, finally, the capacity of the photovoltaic systems to reduce the maximum demand of the electrical system of the city. It was concluded that the most appropriate PV Penetration Level, in terms of power, regards with 40,80 MWp up to 55,68 MWp, disconsidering exceptions. This result leads to maximum values of Effective Load Carrying Capacity (ELCC), for maximum and typical solar radiation, during the seasons of winter and summer. In result, this proposed interval represents the better peak shaving capability of PV, because of its higher ELCC parameter. Furthermore, in addition to increase more than 50% in the capacity of the electrical system, there is an annual amount of energy generated about 50.8 GWh and 69.4 GWh, which represents 18,501 to 25,251 tons of CO2-eq avoided. For this reason, solar PV energy is an extremely important and feasible strategy to enhance the electricity generation, the capacity of the electrical system and to reduce greenhouse gases emission, especially CO2.

Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2017-12-18T16:25:14Z No. of bitstreams: 2 Dissertação - Ciliana Karine Dias Lima - 2017.pdf: 23149224 bytes, checksum: c070892c298f576da2daf6724723a45b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)<br>Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-12-19T12:03:47Z (GMT) No. of bitstreams: 2 Dissertação - Ciliana Karine Dias Lima - 2017.pdf: 23149224 bytes, checksum: c070892c298f576da2daf6724723a45b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)<br>Made available in DSpace on 2017-12-19T12:03:47Z (GMT). No. of bitstreams: 2 Dissertação - Ciliana Karine Dias Lima - 2017.pdf: 23149224 bytes, checksum: c070892c298f576da2daf6724723a45b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-12-11<br>Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq<br>Sustainable development is a present issue in world society and it is also a strategic challenge for Cape Verde’s energy policy in coming years because the large fragilities in the electrical system in Cape Verde such as, dependence on imports of fuels, geographical dispersion, the high costs associated with managing energy systems and the great energy waste. The bet on photovoltaic systems may be one of the alternatives to reducing these fragilities. In this context, the present work highlights the great existent potential for use of renewable energy focused on solar energy. The text describes incentives for the production of electric energy based on renewable sources and presents analyses on the implementation of two grid-connected photovoltaic systems in the island of São Vicente. One of the systems is a photovoltaic rooftop 19.8 kWp plant installed in a public secondary school building and the other system is 3 MWp photovoltaic power plant connected to electrical utility grid in São Vicente Island. The study included design, operation simulation of São Vicente Island distribution network in the presence and absence of photovoltaic systems and financial analyses in order to determine payback time, actual present value, intern return rate of investment and financial sensibility analyses to assess the influence of Wp cost and interest rate on the financial figures. The results show that the implementation of photovoltaic systems is attractive in financial and technical terms, the microgeneration system causes a large reduction in energy acquired by the network, and the large power plant has not worsened the appropriate operating voltage levels and decreased the system's active losses.<br>O desenvolvimento sustentável é uma questão presente na sociedade mundial e é também um desafio para a política energética de Cabo Verde nos próximos anos, devido às grandes fragilidades do sistema elétrico do arquipélago, tais como a forte dependência da importação dos combustíveis fosseis, a dispersão geográfica, os elevados custos associados à gestão dos sistemas energéticos e o grande desperdício energético. A aposta em sistemas fotovoltaicos é uma das alternativas para a redução dessas fragilidades. Neste contexto, o presente trabalho destaca o grande potencial existente em Cabo Verde para utilização de energia renovável com o foco na fonte solar. O trabalho descreve os incentivos legais locais para a produção de energia elétrica com base em fontes de origem renovável e apresenta a análise da implantação de dois sistemas fotovoltaicos conectados à rede elétrica na ilha de São Vicente. Um deles é um sistema de microgeração fotovoltaica de 19,8 kWp instalado em um edifício público de ensino e o outro é uma usina fotovoltaica de grande porte de 3 MWp, ligada à rede elétrica e também localizada na ilha de São Vicente. O estudo inclui o dimensionamento, a simulação de operação da rede de distribuição da ilha de São Vicente na ausência e na presença de sistemas fotovoltaicos. São feitas análises financeiras a fim de determinar o tempo de retorno dos investimentos, o valor atual líquido e a taxa interna de retorno dos investimentos. Também é feito uma análise de sensibilidade financeira para avaliar a influência do custo do Wp instalado e da taxa de juros do financiamento sobre os parâmetros financeiros. Os resultados mostram que a implementação dos sistemas fotovoltaicos é atrativa em termos financeiros e técnicos. A instalação do sistema de microgeração provoca uma grande redução da energia adquirida junto à rede pela unidade consumidora. É mostrado também que a usina de grande porte notadamente não alterou os níveis de tensão de funcionamento da rede e proporcionou uma diminuição das perdas ativas do sistema.

Current power systems have remained qualitatively similar to how the were in the last century, especially with respect to the interaction with the end-users. Though present global challenges are putting pressure and questioning their architecture. The increasing demand for electricity - that has become an essential commodity, fundamental for all activities of today's lifestyle - coupled with the concerns about climate change and the need to improve the quality and reliability of the provision urge a modernization of the network. A modernization that needs: to be low carbon, to be reliability and security improving, and to develop new models of customer relationship. Indeed, the thesis deals with important issues that are today in the limelight, such as: i) the importance of the electricity sector in the implementation of climate change mitigation strategies, ii) the innovation of the electricity network as a strategy for reducing emissions, iii) the design of new policies of management of renewable energies and of the new services available, iv) the need to actively involve the users of the network into new styles of consumption / production of energy. All of this is evaluated in a context of evolving energy policies, where the relative long-term importance of the different power generating technologies is changing, especially after the recent events in Japan. The thesis aims at demonstrating the need to promote a qualitative transformation in the system architecture of the “grid” to make it suitable for managing the complexity of the economic scenarios and advanced services that characterize the emerging “knowledge society”, in compliance with the objectives of environmental sustainability and in response to concerns about global climate change. Indeed, because of these concerns and of social and political acceptability issues of nuclear power, as we know it today, the energy scenarios for the next few decades see the emergence of an increasingly important role for renewable energy sources. The general assumption of the thesis is that such a change in the sources of production is likely to cause a major qualitative leap in the power grid. This transformation may induce the evolution of the electricity grid from a classical architecture, top-down and hierarchical, to a more innovative architecture, that will configure the grid (more and more) as a “social ecosystem”, able to include the empowerment of all its stakeholders and to enhance, in particular, the more active role of all users of the new network services. To demonstrate and operationalize the complex nature of this change and the emerging trends, the thesis is organized into three integrated papers that develop and disentangle the system effects of the two technologies that today seem to be at the basis of the possible evolution: Super-Grids and Smart-Grids. The analysis will be conducted using a qualitative-quantitative methodological approach through simulations for both technologies and their integration. The first paper - New electricity generation networks and climate change: the economic potential of national and trans-national super-grids powered by Concentrated Solar Power - develops the analysis of Super-Grids. More in detail, it analyses the system effects and the technological and economic opportunities of transmitting large amounts of electricity over long distances, for the stabilization of anthropogenic emissions of greenhouse gases, with particular attention to the resulting geopolitical dynamics. The analysis is conducted using the simulation platform WITCH, an Integrated Assessment Model (IAM), able to compare this option with other mitigation opportunities, in a framework of intertemporal optimization of resources. In particular, the focus is on the production of electricity from concentrated solar power (CSP) in areas of high solar intensity in places located far from demand centres and, until now, not economically advantageous. The quantitative analysis focuses on the electricity supply made available by the Super-Grid - both domestically and for export/import - evaluating their economic, technological and CO2 mitigation potentials. We have analyzed, in particular, the EU-MENA trade case, though, the results can be expanded qualitatively to consider also the North-South European energy axis, extending the analysis of the geopolitical implications. The second paper - Smart-Grids and Climate Change. Consumer adoption of smart energy behaviour: a system dynamics approach to evaluate the mitigation potential - develops the analysis of Smart-Grids. More in detail, it analyses the system effects of engaging with consumers. More specifically, it looks at the impacts of allowing consumers to: (i) manage more actively and consciously their consumption patterns; (ii) participate to innovative contracting; (iii) generate electricity for own consumption and /or to inject into the grid. Particular interest is directed to the increase in variety of user behaviour (shift, demand response, home automation, generation), caused by the implementation of Smart-Grids, which allows: (i) to form new relationships among actors of the network, (ii) to trigger new processes of “micro production” for energy self-sufficiency to be integrated into the network; and to (iii) improve the management and optimization of the power network. In short, to transform the network into a “sensitive network” capable of opening new organizational spaces/times of action. The analysis is conducted by means of simulations of the adoption dynamics of “smart energy behaviours” by citizens, using the methodology of System Dynamics (J. Forrester) to address the complexity of the dynamics involved. The quantitative analysis focuses on the power supply made available by the change in consumption patterns and by domestic generation, in a “energy self-sufficiency” perspective and on the impacts in terms of demand, system costs and opportunities for mitigation. The qualitative analysis studies the organizational transformations, and the social and cultural evolutions induced by the new interactivity with the end-user The concept of Smart Grid connects the power system to the emerging qualitative transformations and scenarios of the “Knowledge Society” and its newly empowered “Smart Prosumer”. In the third paper - Super & Smart Grid integrated investment scenarios: Green Sustainable Energy Management Strategies & Scenarios - the complex effects of Super and Smart Grid are analysed together. The paper is divided in two parts: the first one where Super and Smart Grids are integrated in one simulation environment to conduct an in-depth economic analysis, and the second part where they are jointly evaluated and compared considering the effects of the innovation of the electricity grid on different levels: environmental, technological, economic, organizational, social and geopolitical, by means of the GEMS (Green Energy Management Strategies foe sustainable scenarios) multi-level evaluation function: GEMS = (Env, Tech, Ec, Org, Soc, GeoP). The proposal is to identify an approach for the analysis and management of the various strategies of green energy generation, that is able to grasp the complexities and interactions of the multiple effects induced by the different options. The quantitative analysis focuses on the integration of the power supply made available jointly by Super and Smart Grids. The qualitative analysis has investigated the new dynamics of empowerment among all the stakeholders involved and the possible impacts on various levels. The synergies of system integration, related to the potential mix of Super and Smart Grids, to manage the evolution of green electricity are also analysed. Concluding, the thesis started with a substantial economic and computational approach, and then was expanded to take into account qualitative aspects that govern the dynamics of the complex “social ecosystem” in play. In synthesis, we analyze the quali-quantitative system effects induced by the impact of the innovation processes in the power network, in an energy market that is not able, alone and in a classical economic perspective, to jointly optimize aspects concerning the environment, technology, organizational structures, economics, society and geopolitics, that are put into play by the introduction of these technological options. These tools are also needed to manage the inevitable conflicts of interest that will arise with the change. We propose an approach “beyond grid parity”, in the sense that we aim at analyzing a broader concept of “costs”, to: (i) identify the paths of evolution of the electrical system in the scenarios of the knowledge society, (ii) the nature and extent of the processes involved, and (iii) to assess the feasibility of accepting the challenge of a low-carbon economy based on renewable energy.

Distributed power generation through renewable sources of energy has the potential of meeting the challenge of providing electricity access to the off-grid population, estimated to be around 1.2 billion residing across the globe with 300 million in India, in a sustainable way. Technological solutions developed around these energy challenges often involve thermal systems that convert heat available from sources like solar, biomass, geothermal or unused industrial processes into electricity. Conventional steam based thermodynamic cycle at distributed scale (< 1 MWe) suffers from low efficiency driving scientific research to develop new, scalable, efficient and economically viable power cycles. This PhD work conducts one such study which provides a database of thermal power blocks optimized for the lowest initial investment cost to developers of distributed power plants. The work is divided in two steps; a) feasibility study of various thermodynamic cycles for distributed power generation covering different operating temperature regimes and b) perform their detailed thermo-economic modelling for the heat sources mentioned above. Thermodynamic cycles are classified into three temperature domains namely, low (< 450 K), medium (< 600 K) and high (< 1000 K) T cycles. Any fluid whose triple point temperature is below the typical ambient temperatures is a potential working fluid in the power cycle. Most of the organic and the inorganic fluids satisfy this criterion and can be perceived as potential power cycle fluids. The general notion is that organic fluids are more suited for low or medium temperature cycles whereas inorganic fluids for high temperature ones. Organic fluids can further be classified into hydrofluorocarbon and hydrocarbon. While the former has high global warming potential (GWP), the latter is flammable in nature. Their mixture in certain compositions is found to obviate both the demerits and perform equally well on thermodynamic scales for low T cycles. On the similar lines, mixture of HCs and inorganic fluids, such as propane+CO2 and isopentane+CO2 are found to be more appropriate for medium T applications if the issues like pinch temperature in the regenerator arising due to temperature glide are taken care of. In the high temperature domain, high efficiency Brayton cycle (supercritical CO2) and transcritical condensing cycles are studied with the latter being 2 % more efficient than the former. However, application of the condensing cycle is limited to low temperature ambient locations owing to low critical temperature of CO2 (304 K). In the same cycle configuration, mixture of CO2 and propane (52 and 48%) with a critical temperature of ~ 320 K is observed to retain the thermodynamic performance with the increased heat rejection temperature matched to the tropical ambient conditions. However, these cycles are plagued by the high operating pressures (~300 bar) calling for high temperature steel making the power block uneconomical. In this regard, the advanced CO2 cycles are developed wherein the optimum operating pressures are limited to 150 bar with an increased cycle efficiency of 6 % over the S-CO2 cycle. Feasibility study carried out on these cycles in the Indian context indicates the low and medium T cycles to be better suited for distributed power generation over the high T cycles. In the second part of work, a comprehensive study is performed to optimize the low and the medium T cycles on a thermo-economic basis for the minimum specific investment cost ($/We). Such a study involves development of component level models which are then integrated to form the system of interest, thus, following a bottom-up approach. A major emphasis is given on the development of scroll expander and low cost pebble bed thermal energy storage system that are the reported in the literature as the areas with high uncertainties while connecting them to the system. Subsequently, the key design parameters influencing the specific cost of power from an air-cooled ORC are identified and used to formulate a 7-dimensional space to search for the minimum costs for applications with a) geothermal/waste or biogas heat sources and b) solar ORCs. Corresponding maps of operating parameters are generated to facilitate distributed power engineers in the design of economic systems within constraints such as available heat source temperatures, maximum expander inlet pressures imposed, etc. Further, the effect of power scaling on these specific costs is evaluated for ORC capacities between 5 and 500 kWe.

Distributed power generation through renewable sources of energy has the potential of meeting the challenge of providing electricity access to the off-grid population, estimated to be around 1.2 billion residing across the globe with 300 million in India, in a sustainable way. Technological solutions developed around these energy challenges often involve thermal systems that convert heat available from sources like solar, biomass, geothermal or unused industrial processes into electricity. Conventional steam based thermodynamic cycle at distributed scale (< 1 MWe) suffers from low efficiency driving scientific research to develop new, scalable, efficient and economically viable power cycles. This PhD work conducts one such study which provides a database of thermal power blocks optimized for the lowest initial investment cost to developers of distributed power plants. The work is divided in two steps; a) feasibility study of various thermodynamic cycles for distributed power generation covering different operating temperature regimes and b) perform their detailed thermo-economic modelling for the heat sources mentioned above. Thermodynamic cycles are classified into three temperature domains namely, low (< 450 K), medium (< 600 K) and high (< 1000 K) T cycles. Any fluid whose triple point temperature is below the typical ambient temperatures is a potential working fluid in the power cycle. Most of the organic and the inorganic fluids satisfy this criterion and can be perceived as potential power cycle fluids. The general notion is that organic fluids are more suited for low or medium temperature cycles whereas inorganic fluids for high temperature ones. Organic fluids can further be classified into hydrofluorocarbon and hydrocarbon. While the former has high global warming potential (GWP), the latter is flammable in nature. Their mixture in certain compositions is found to obviate both the demerits and perform equally well on thermodynamic scales for low T cycles. On the similar lines, mixture of HCs and inorganic fluids, such as propane+CO2 and isopentane+CO2 are found to be more appropriate for medium T applications if the issues like pinch temperature in the regenerator arising due to temperature glide are taken care of. In the high temperature domain, high efficiency Brayton cycle (supercritical CO2) and transcritical condensing cycles are studied with the latter being 2 % more efficient than the former. However, application of the condensing cycle is limited to low temperature ambient locations owing to low critical temperature of CO2 (304 K). In the same cycle configuration, mixture of CO2 and propane (52 and 48%) with a critical temperature of ~ 320 K is observed to retain the thermodynamic performance with the increased heat rejection temperature matched to the tropical ambient conditions. However, these cycles are plagued by the high operating pressures (~300 bar) calling for high temperature steel making the power block uneconomical. In this regard, the advanced CO2 cycles are developed wherein the optimum operating pressures are limited to 150 bar with an increased cycle efficiency of 6 % over the S-CO2 cycle. Feasibility study carried out on these cycles in the Indian context indicates the low and medium T cycles to be better suited for distributed power generation over the high T cycles. In the second part of work, a comprehensive study is performed to optimize the low and the medium T cycles on a thermo-economic basis for the minimum specific investment cost ($/We). Such a study involves development of component level models which are then integrated to form the system of interest, thus, following a bottom-up approach. A major emphasis is given on the development of scroll expander and low cost pebble bed thermal energy storage system that are the reported in the literature as the areas with high uncertainties while connecting them to the system. Subsequently, the key design parameters influencing the specific cost of power from an air-cooled ORC are identified and used to formulate a 7-dimensional space to search for the minimum costs for applications with a) geothermal/waste or biogas heat sources and b) solar ORCs. Corresponding maps of operating parameters are generated to facilitate distributed power engineers in the design of economic systems within constraints such as available heat source temperatures, maximum expander inlet pressures imposed, etc. Further, the effect of power scaling on these specific costs is evaluated for ORC capacities between 5 and 500 kWe.

abstract: Photovoltaic (PV) systems are affected by converter losses, partial shading and other mismatches in the panels. This dissertation introduces a sub-panel maximum power point tracking (MPPT) architecture together with an integrated CMOS current sensor circuit on a chip to reduce the mismatch effects, losses and increase the efficiency of the PV system. The sub-panel MPPT increases the efficiency of the PV during the shading and replaces the bypass diodes in the panels with an integrated MPPT and DC-DC regulator. For the integrated MPPT and regulator, the research developed an integrated standard CMOS low power and high common mode range Current-to-Digital Converter (IDC) circuit and its application for DC-DC regulator and MPPT. The proposed charge based CMOS switched-capacitor circuit directly digitizes the output current of the DC-DC regulator without an analog-to-digital converter (ADC) and the need for high-voltage process technology. Compared to the resistor based current-sensing methods that requires current-to-voltage circuit, gain block and ADC, the proposed CMOS IDC is a low-power efficient integrated circuit that achieves high resolution, lower complexity, and lower power consumption. The IDC circuit is fabricated on a 0.7 um CMOS process, occupies 2mm x 2mm and consumes less than 27mW. The IDC circuit has been tested and used for boost DC-DC regulator and MPPT for photo-voltaic system. The DC-DC converter has an efficiency of 95%. The sub-module level power optimization improves the output power of a shaded panel by up to 20%, compared to panel MPPT with bypass diodes.<br>Dissertation/Thesis<br>Doctoral Dissertation Electrical Engineering 2014

碩士<br>國立臺北科技大學<br>電能轉換與控制產業碩士專班<br>101<br>This thesis focuses on distributed PV solar power systems. Common central power generation has worse efficiency when shading effect occurs. This motivates us on distributed PV solar systems. Distributed solar power connects a boost converter on every solar module to make every solar module with maximum power point tracking (MPPT) function. This can enhance overall output power even when shading effect exists. Microprocessor Arduino is applied in this study as a system controller. The maximum power point tracking applied at this study is a combination of the Perturbation and Observation method (P&O) and the moving average method, whereby MPPT can be achieved successfully. This method only needs one controller. Hence, the quantity and the cost of controllers can be reduced. Finally, we use Zigbee module to do wireless data transmission and save the data in computer as excel file. Moreover, an LCD panel is used to display the shading position of solar modules and many other functions. Finally, experimental results show that the developed distributed structure and the MPPT method can precisely enhance solar power generation efficiency.

碩士<br>國立臺南大學<br>綠色能源學科技學系碩士在職專班<br>105<br>The purpose of this study is to analyze the decentralized solar power generation in Taiwan peak power consumption can pay the proportion of power supply and distribution of different modules flexible use of the discussion. This study is based on the road and the National Bureau of Highway Road and the national road data, in accordance with the field and Google map simulation set up decentralized solar photovoltaic power generation device, simulation planning out of Taiwan will be able to set the capacity of decentralized solar power generation system, according to different settings, Estimated at 4797MW to 15795MW, and then compared to the Bureau of Meteorology and many previous studies to be calculated, that the actual power generation capacity can reach 80% of the set, if the relevant simulation software such as sun monitor to be estimated, the study of the default The amount of equipment will be easier to predict power generation. From the Taipower public network data comparison analysis that solar power generation system in the sunshine sunshine enough time to reach the optimal capacity of the device capacity. From the daily actual power generation curve, it can be learned that the decentralized solar power generation in this study has a great help to the increase in the peak load capacity of Taiwan. In the future, if the smart grid of Taipower will be successfully completed, the distributed solar power will be different Regional regulation of power supply or energy storage. Future related research and development can be active Taiwan local economic science and technology, follow-up research and construction in the electrical law to amend the opening, but also by the people to participate more fully.

碩士<br>國立高雄應用科技大學<br>電機工程系博碩士班<br>104<br>A distributed PV control architecture, which the DC-DC converter is moved from the inverter to solar panel array end, is not only can to improve the overall efficiency of power generation, but also can to simple the inverter design, to reduce electromagnetic interference EMI and implementation costs, to extend service life of many other benefits and so on. The main purpose of this thesis is to develop and to simulate boost converter as a voltage regulator which can mounted on the distributed PV systems. This proposed converter can maintain each loop in the same parallel bus voltage level during abnormal period, and then to improve the output efficiency of the PV system. The main approach is to use PSIM simulation software to build the distributed PV system and to simulate the models in two status. One status is that every circuit has regulator to control output voltage and the other status has no. On the other hand, to develop a 5kW high-power level boost converter which can be applied to the proposed PV system, in order to verify the actual circuit performance testing and the availability.

abstract: At present, almost 70% of the electric energy in the United States is produced utilizing fossil fuels. Combustion of fossil fuels contributes CO2 to the atmosphere, potentially exacerbating the impact on global warming. To make the electric power system (EPS) more sustainable for the future, there has been an emphasis on scaling up generation of electric energy from wind and solar resources. These resources are renewable in nature and have pollution free operation. Various states in the US have set up different goals for achieving certain amount of electrical energy to be produced from renewable resources. The Southwestern region of the United States receives significant solar radiation throughout the year. High solar radiation makes concentrated solar power and solar PV the most suitable means of renewable energy production in this region. However, the majority of the projects that are presently being developed are either residential or utility owned solar PV plants. This research explores the impact of significant PV penetration on the steady state voltage profile of the electric power transmission system. This study also identifies the impact of PV penetration on the dynamic response of the transmission system such as rotor angle stability, frequency response and voltage response after a contingency. The light load case of spring 2010 and the peak load case of summer 2018 have been considered for analyzing the impact of PV. If the impact is found to be detrimental to the normal operation of the EPS, mitigation measures have been devised and presented in the thesis. Commercially available software tools/packages such as PSLF, PSS/E, DSA Tools have been used to analyze the power network and validate the results.<br>Dissertation/Thesis<br>M.S. Electrical Engineering 2013

This thesis deals with quantifying the merits of Distributed Maximum Power Point Tracking (DMPPT), as well as providing solutions to achieve DMPPT in PV systems. A general method based on 3D modeling is developed to determine the energy yield of PV installations exploiting different levels of DMPPT granularity. Sub-string-level DMPPT is shown to have up to 30% more annual energy yield than panel-level DMPPT. A Multi-Input-Single-Output (MISO) dc-dc converter is proposed to achieve DMPPT in parallel-connected applications. A digital current-mode controller is used to operate the MISO converter in pseudo-CCM mode. For series-connected applications, the virtualparallel concept is introduced to utilize the robustness of the parallel connection. This concept is demonstrated on a three-phase boost converter. The topology offers reduced output voltage ripple under shading which increases the life-time of the output capacitor. The prototypes yield output power benefits of up to 46% and 20% for the tested shading conditions.

This study provides an evaluation of Concentrating Solar Power (CSP) technologies and investigates the feasibility of distributed power generation in urban areas of Johannesburg. The University of the Witwatersrand (Wits) is used as a case study with energy security and climate change mitigation being the main motivators. The objective of the study was to investigate the potential of CSP integration in urban areas, specifically investigating Johannesburg’s solar resource. This is done by assessing the performance and financial characteristics of a variety of technologies in order to identify certain systems that may have the potential for deployment. To aid the comparison of the technologies, CSP performance and cost data which were taken from multiple sources, were adjusted giving it local, present day assumptions. A technology screening process resulted in the conception of twelve alternative design configurations, each with a reference capacity of 120 kW(e). Hourly energy modelling was undertaken for Wits University’s West Campus for each of the twelve alternatives. Three configurations were further investigated and are listed below; each with a design capacity of 480 kW(e). 1. Compound Linear Fresnel Receiver (CLFR) field with an Organic Rankine Cycle (ORC). 2. Compound Linear Fresnel Receiver field with an Organic Rankine Cycle that integrates storage for timed dispatch. 3. Compound Linear Fresnel Receiver field with an Organic Rankine Cycle that integrates hybridisation with natural gas. Levelised electricity costs (LEC) of the systems were used as the basis for financial comparison. Real LECs, for the three configurations above, range between R4.31/kWh(e) (CLFR, ORC) and R3.18/kWh(e) (CLFR, ORC with hybridisation). v With the energy modelling of the hourly direct normal irradiation (DNI) input into the CSP systems, Wits University’s West Campus Electricity bill was recalculated. The addition of the solar energy input resulted in certain savings and a new LEC that is Wits-specific. These LECs ranged between R3.98/kWh(e) (CLFR, ORC) and R2.77/kWh(e) (CLFR, ORC with hybridisation). A third LEC was calculated that integrates a CSP feed-in tariff (REFIT) of R2.05/kWh. At the time of writing, a CSP REFIT of R2.10/kWh was released which favours the analysis. The analysis of the 480 kW(e) systems resulted in total plant areas of between 10350 m2 (CLFR, ORC,) and 15270 m2 (CLFR, ORC, with storage). With plant modulation, these plants can be placed on vacant land, above parking lots or on top of buildings which would also provide shading. The values obtained for the average yearly insolation was 1781 kWh/m2 based on TMY2 data. Johannesburg has a very intermittent source of DNI solar energy. The summer months in Johannesburg yield a higher peak DNI, whereas the winter months provide a more consistent average. This is due to the high amount of cloud cover experienced in summer. With this insolation, CSP electric generation is possible however, compared to the other locations, it is not ideal. Also, because of its intermittency is has been advised that certain applications such as HVAC and process heat and steam requirements be pursued. From the results, it can be concluded that power production costs through small scale CSP systems are still higher than with conventional fossil fuel options, however several options that may favour implementation were recognised. Through the analysis it was found that if the CSP generated electricity is valued at the market price ( CSP REFIT), the payback time of such systems can be decreased from 73 to 12 years (CLFR, ORC with storage). Further, due to the scale of the plants analysed, the exploitation of high efficiencies and economies-of-scale of plants with power levels above 50 MW(e), is not possible. With the introduction of these technologies vi at lower power levels, cost savings through the incorporation of other design options (such as waste heat utilisation) should be pursued. It was recognised that South Africa in general has one of the greatest solar resources in the world and should therefore be technology leaders and pioneers in CSP technology. With greater emphasis being placed on the need for renewable energy systems, it is imperative that South Africa develops its skills and a knowledge base that will work at making the implementation of renewable energy, and in particular CSP generation, a reality. Technologies identified that should be pursued for distributed generation include Linear Fresnel collectors that are easy to manufacture and don’t involve complicated receiver systems. There is also scope for developing thermal storage technologies in order to make generation more reliable.

碩士<br>國立臺灣科技大學<br>資訊工程系<br>107<br>As global warming and energy shortages are gradually deteriorating, the issue of renewable energy has become a worldwide hot topic. In Taiwan, because of the narrowness of the ground which is highly populated, the setting of the solar power plants are small-scale and distributed. Therefore, communication between the solar power generation plants and the central monitoring and data acquisition system plays an important role in the power system. In order to solve the problem of distributed small-scale solar power plant data collection without standard protocols, the implementation of international standards for small-scale solar power plants is too expensive. In this thesis, we invent a low-cost bidirectional controller which collects and aggregates data from solar power plants by various protocols such as HTTP POST, HTTPS API query and TCP socket. In addition, the bidirectional controller is able to receive the control command from IEC 61850 server and then control the solar power plant inverters directly by using Modbus RTU protocol. By using the proposed bidirectional controller, the control center can easily collect data in order to predict power generation and quickly dispatch power in the grid. The overall hardware cost of our proposed system for each solar power plant is less than 20,000 NT dollars. Based on our stress tests, the IEC 61850 server can be built to load the entire power grid without using high-end hardware or a large number of servers.

Tese de doutoramento em Engenharia Mecânica, no ramo de Sistemas de Energia Sustentável, apresentada ao Departamento de Engenharia Mecânica da Faculdade de Ciências e Tecnologia da Universidade de Coimbra<br>O setor da construção é responsável por uma grande parte do consumo de energia e emissões na União Europeia. A Geração Distribuída (GD) de energia, nomeadamente através de sistemas de cogeração e tecnologias solares, representa um papel importante no futuro energético deste setor. A otimização do funcionamento dos sistemas de cogeração é uma tarefa complexa, devido às diversas variáveis em jogo, designadamente: os diferentes tipos de necessidades energéticas (eletricidade, aquecimento e arrefecimento), os preços dinâmicos dos combustíveis (gás natural) e da eletricidade, e os custos fixos e variáveis dos diferentes sistemas de GD. Tal torna-se mais complexo considerando a natureza flutuante das tecnologias solares térmicas e fotovoltaicas. Ao mesmo tempo, a liberalização do mercado da eletricidade permite exportar para a rede, a electricidade gerada localmente. Adicionalmente, a operação estratégica de um sistema de GD deve atender aos quadros políticos nacionais, se tiver como objetivo beneficiar de tais regimes. Além disso, considerando os elevados impactes ambientais do setor da construção, qualquer avaliação energética de edifícios rigorosa deve também integrar aspetos ambientais, utilizando uma abordagem de Ciclo de Vida (CV). Uma avaliação de Ciclo de Vida (ACV) completa de um sistema de GD deve incluir as fases relativas à operação e construção do sistema, bem como os impactes associados à produção dos combustíveis. Foram analisadas as emissões da produção de GN, as quais variam de acordo com a origem, tipo (convencional ou não-convencional), e estado (na forma de GN Liquefeito (GNL) ou gás). Do mesmo modo, o impacte dos sistemas solares é afetado pela meteorologia e radiação solar, de acordo com a sua localização geográfica. Sendo assim, uma avaliação adequada dos sistemas de GD exige um modelo de ACV adequado à localização geográfica (Portugal), integrando também a produção de combustível (GN), tendo em conta as suas diferentes fontes de abastecimento. O principal objetivo desta tese de doutoramento foi desenvolver um modelo para otimizar o desenho e operação de sistemas de GD para o setor da construção de edifícios comerciais em Portugal, considerando os respetivos Impactes de Ciclo de Vida (IAVC) e Custos de Ciclo de Vida (CCV), de modo a satisfazer as necessidades energéticas do edifício. Três tipos de tecnologias de cogeração (Micro-Turbinas, Motores de combustão interna, e Células combustíveis de Óxido sólido), e dois tipos de tecnologias de energia solar, solar térmica e fotovoltaica, constituem os sistemas de GD que são acoplados aos sistemas convencionais. Foi desenvolvido um modelo de CV, tendo em conta todos os impactes relacionados com a construção e operação dos sistemas de energia, bem como os processos a montante relacionados com a produção do GN. Em particular, o mix de GN consumido em Portugal em 2011 foi identificado (60% da Nigéria, 40% da Argélia) e os impactes relativos a cada uma das vias de abastecimento foram avaliados separadamente para quatro categorias de impacte ambiental: Consumo de Energia Primária (CEP), Gases com Efeito de Estufa (GEE), acidificação, e eutrofização. Devido à importância das emissões de GEE na formulação de políticas, foi também realizada uma análise de incerteza às emissões de GEE do GN fornecido a Portugal. Foi desenvolvido um modelo matemático, em linguagem de Programação General Algebraic Modeling System (GAMS), que utiliza os resultados da ACV dos sistemas de energia e as suas implicações económicas para minimizar o CCV e IACV ao longo de um horizonte de planeamento definido pelo decisor. Foram derivadas fronteiras ótimas de Pareto, representando as relações entre o tipo de IACV (CEP, GEE, acidificação, eutrofização) e CCV decorrentes da satisfação das necessidades energéticas do edifício. Para aumentar a robustez do modelo, dada a incerteza dos preços dos combustíveis (GN e eletricidade), foi desenvolvido um modelo de custos robusto para os sistemas de GD, que é menos afetado por perturbações relativas aos custos de combustível. A aplicação do modelo proposto foi testada num caso de estudo real, um edifício comercial localizado na cidade de Coimbra, em Portugal.<br>Energy use in the building sector constitutes a major proportion of energy consumption and emissions in European Union. Distributed Generation (DG) sources, namely cogeneration and solar technologies, are expected to play an important role in future energy supply mix of building sector. However, the optimal design and operation of cogeneration is a complex task, due to the diversity of variables in play, namely different types of building energy demands (electrical, heating, cooling) and their variation, dynamic fuel (natural gas) and electricity prices, and fixed and variable costs of different types of DG. This becomes more complex by coupling fluctuating solar thermal and photovoltaic technologies. At the same time, the liberalization of electricity market allows exporting onsite produced electrical energy to the grid; moreover, the operational strategy of DG should meet the national policy frameworks, if the aim is to benefit from such schemes. Additionally, considering the high impacts of the building sector, any rigorous assessment of building energy systems should also incorporate environmental aspects, using Life-Cycle (LC) approaches. A complete LC Assessment (LCA) of DG should include stages related to their construction and operation, as well as the upstream emissions related to their fuel input, i.e. Natural Gas (NG). The upstream emissions of NG varies based on its source, type (conventional vs. unconventional) and state of delivery (in the form of Liquefied Natural Gas (LNG) or gas). Similarly, the impact of solar systems is affected by meteorology and solar radiation, which is determined by geographical location. Therefore, a proper assessment of DG calls for an LC framework properly modeled for the location (Portugal), which also incorporates the appropriate fuel input (NG) upstream emissions based on its sources of supply. The objective of this doctoral research is to present a modelling framework to optimize the design and operation of DG for the Portuguese commercial building sector, while considering the Life-Cycle Environmental Impacts (LCEI) and Life-cycle Costs (LCC) of meeting the building energy demand. Three types of cogeneration technologies (Micro-Turbines (MT), Internal Combustion Engines (ICE), Solid Oxide Fuel Cells (SOFC)), and two types of solar technologies [solar thermal (ST) and Photovoltaic (PV)] comprise the DG sources that are coupled with conventional sources. An LC model is built taking into account all the impacts related to construction and operation of energy systems, as well as the upstream processes related to their fuel input, i.e. NG. For the latter, the mix of NG consumed in Portugal in 2011 (60% from Nigeria, and 40% from Algeria) is identified and the upstream impacts of each route of NG to Portugal are separately assessed for four types of environmental impacts: Cumulative Energy Demand (CED), Greenhouse Gases (GHG), Acidification and Eutrophication. Due to effect of GHG emissions on policy design, an uncertainty analysis of upstream GHG emissions of NG supplied to Portugal is also performed. A mathematical model is developed in General Algebraic Modeling System (GAMS) that uses the results of LCA of energy systems and their economic implications to minimize the LCC and LCEI of meeting the building demand over a planning horizon. Pareto Optimal frontiers are derived, representing the trade-offs between a type of environmental impact (CED, GHG, Acidification, Eutrophication) and LCC arising from meeting the building energy demand. To increase the model robustness due to uncertainty in fuel prices (NG and electricity), a cost robust modeling framework for DG, one that gets least affected by the perturbation of input fuel costs, is also developed. The application of the proposed model is tested on a real-world case-study, a commercial building located in the city of Coimbra, Portugal.<br>EMSURE (CENTRO-07-0224-FEDER-002004)

This research focuses on developing strategies for the optimal control of large-scale Combined Cooling, Heating and Power (CCHP) systems to meet electricity, heating, and cooling demands, and evaluating the cost savings potential associated with it. Optimal control of CCHP systems involves the determination of the mode of operation and set points to satisfy the specific energy requirements for each time period. It is very complex to effectively design optimal control strategies because of the stochastic behavior of energy loads and fuel prices, varying component designs and operational limitations, startup and shutdown events and many more. Also, for large-scale systems, the problem involves a large number of decision variables, both discrete and continuous, and numerous constraints along with the nonlinear performance characteristic curves of equipment. In general, the CCHP energy dispatch problem is intrinsically difficult to solve because of the non-convex, non-differentiable, multimodal and discontinuous nature of the optimization problem along with strong coupling to multiple energy components. <div><br></div><div>This work presents a solution methodology for optimizing the operation of a campus CCHP system using a detailed network energy flow model solved by a hybrid approach combining mixed-integer linear programming (MILP) and nonlinear programming (NLP) optimization techniques. In the first step, MILP optimization is applied to a plant model that includes linear models for all components and a penalty for turning on or off the boilers and steam chillers. The MILP step determines which components need to be turned on and their respective load needed to meet the campus energy demand for the chosen time period (short, medium or long term) with one-hour resolution. Based on the solution from MILP solver as a starting point, the NLP optimization determines the actual hourly state of operation of selected components based on their nonlinear performance characteristics. The optimal energy dispatch algorithm provides operational signals associated with resource allocation ensuring that the systems meet campus electricity, heating, and cooling demands. The chief benefits of this formulation are its ability to determine the optimal mix of equipment with on/off capabilities and penalties for startup and shutdown, consideration of cost from all auxiliary equipment and its applicability to large-scale energy systems with multiple heating, cooling and power generation units resulting in improved performance. </div><div><br></div><div>The case-study considered in this research work is the Wade Power Plant and the Northwest Chiller Plant (NWCP) located at the main campus of Purdue University in West Lafayette, Indiana, USA. The electricity, steam, and chilled water are produced through a CCHP system to meet the campus electricity, heating and cooling demands. The hybrid approach is validated with the plant measurements and then used with the assumption of perfect load forecasts to evaluate the economic benefits of optimal control subjected to different operational conditions and fuel prices. Example cost optimizations were performed for a 24-hour period with known cooling, heating, and electricity demand of Purdue’s main campus, and based on actual real-time prices (RTP) for purchasing electricity from utility. Three optimization cases were considered for analysis: MILP [no on/off switch penalty (SP)]; MILP [including on/off switch penalty (SP)] and NLP optimization. Around 3.5% cost savings is achievable with both MILP optimization cases while almost 10.7% cost savings is achieved using the hybrid MILP-NLP approach compared to the current plant operation. For the selected components from MILP optimization, NLP balances the equipment performance to operate at the state point where its efficiency is maximum while still meeting the demand. Using this hybrid approach, a high-quality global solution is determined when the linear model is feasible while still taking into account the nonlinear nature of the problem. </div><div><br></div><div>Simulations were extended for different seasons to examine the sensitivity of the optimization results to differences in electric, heating and cooling demand. All the optimization results suggest there are opportunities for potential cost savings across all seasons compared to the current operation of the power plant. For a large CCHP plant, this could mean significant savings for a year. The impact of choosing different time range is studied for MILP optimization because any changes in MILP outputs impact the solutions of NLP optimization. Sensitivity analysis of the optimized results to the cost of purchased electricity and natural gas were performed to illustrate the operational switch between steam and electric driven components, generation and purchasing of electricity, and usage of coal and natural gas boilers that occurs for optimal operation. Finally, a modular, generalizable, easy-to-configure optimization framework for the cost-optimal control of large-scale combined cooling, heating and power systems is developed and evaluated.</div>

Grid reliability and power outages are key concerns today, due to the ever-increasing energy demand. Traditionally, Uninterruptible Power Supplies (UPS) with battery storage have been employed to contend with grid outages. For renewable power production, Solar-Photovoltaics (SPV) based Distributed Energy Resources (DERs) have been integrated with the grid using a power electronic Grid-Tied Inverter (GTI). A typical GTI by design, engages in power conversion only when the grid is present, and ceases operation during a power outage to avoid a local unintentional island formation. Thus, solar energy is left unutilized by the GTI during a power outage, where the UPS steps in, to power critical loads. Recently, hybrid-PV or dual-mode inverter systems, that combine the complementary functional properties of UPS and GTI, have been in the focus of research due to their ability of standalone system operation during an outage while accessing solar power. Such a hybrid approach, although meets the desired operational objectives, requires the design, sizing, and control of the entire system, that comprises of multiple power converters, battery-banks, and SPV, to be carried out in a unified manner. This work enhances the existing methods of solar energy access during a power outage, where the GTI is kept as an independent system from the UPS. A reconfigurable battery/grid tied inverter (RBGTI) scheme is proposed, that ties to the grid and functions as a regular DCAC GTI when grid is present. However, during a power outage, it reconnects to the batterybank of an existing UPS present in a facility, where it functions as a DC-DC converter to provide PV based energy support. However, such an operation of RBGTI requires several questions to be resolved in terms of hardware configuration, islanding behavior, battery management, and overall system control, which are addressed in this work. For the islanding behavior in grid-tied mode, a dynamic-phasor based GTI system model is proposed that captures the system dynamics accurately after unintentional islanding and allows systematic stability study based on eigenvalue analysis. In the battery-tied mode, a dynamic model of the PV fed battery charge-controller system is proposed which facilitates the systematic design of a maximum-power-point tracking (MPPT) controller and a load current tracking controller for the RBGTI, that achieves the effect of a virtual PV based batterybank in parallel with the physical UPS battery. A supervisory RBGTI control scheme is proposed that ensures stable system operation during dynamic conditions of load power and solar insolation changes while reducing discharge burden on the UPS battery. A discrete IGBT converter hardware platform is developed, where the proposed analytical models, controls and the RBGTI performance are verified on a 4.5 kW experimental setup

O acesso à eletricidade está associado à melhoria dos meios de subsistência, educação, saúde, crescimento económico e redução geral da pobreza. A grande maioria das pessoas que vivem sem, ou com acesso não fiável, a energia elétrica encontra-se na África subsaariana e sudeste asiático. Apesar de ser a maior economia de África, a Nigéria sofre de problemas graves de cortes frequentes de energia, obrigando muitos residentes a procurar opções de auto-geração, sobretudo geradores a diesel, com custos de investimento inicial relativamente baixo, mas que trazem riscos à saúde e ao meio ambiente. Uma alternativa viável são os sistemas fotovoltaicos; no entanto, o investimento inicial é muito maior em comparação com os geradores a diesel, criando uma barreira para muitos nigerianos. A primeira parte desta tese explora a opção de geração de eletricidade solar em ambiente urbano, mais limpa e mais acessível, aumentando o acesso fiável a eletricidade e reduzindo, ou eliminando, o uso de geradores a diesel. Propõe-se um caminho para a implementação em larga escala de sistemas fotovoltaicos domésticos em ambiente urbano, com o custo coberto pela poupança de combustível, possibilitado por uma política eficaz que melhora o acesso a opções de financiamento. Aproveitando dados reais de uma campanha de monitorização de consumo de eletricidade em Lagos, o centro comercial da Nigéria, os resultados mostram uma oportunidade para reduzir ou eliminar o uso de geradores a diesel aplicando a poupança de custos de combustível para financiar sistemas fotovoltaicos. A segunda parte desta tese trata do setor comercial, que tem sido significativamente prejudicado pela pouca disponibilidade de eletricidade confiável. Quase metade das empresas na Nigéria identificou a eletricidade como um grande obstáculo, com mais de um quarto delas apresentando a eletricidade como maior obstáculo. As perdas comerciais devido a interrupções elétricas são significativas, com perdas médias estimadas de cerca de 16% das vendas anuais. A falta de acesso a eletricidade confiável é um dos maiores desafios para o crescimento económico na Nigéria. É proposto um meio de fornecer energia ao setor comercial através de eletrificação solar por enxame (swarm). É descrita uma estrutura conceitual para o uso de uma rede distribuída composta de sistemas fotovoltaicos domésticos ligados à rede como uma opção viável para fornecer ao setor comercial um acesso mais confiável à eletricidade. Finalmente, são abordadas as implicações de política para o setor comercial com mais opções de eletrificação, implicações que incluem um forte impacto económico e a expansão e criação de novas indústrias.<br>Access to electricity has been linked to improved livelihood, education, health, economic growth, and overall poverty reduction. The vast majority of people living without electricity or unreliable electricity access are concentrated in sub-Saharan Africa and South Asia. Despite being the largest economy in Africa, Nigeria suffers from severe power outages, forcing many residents to seek self-generation options. By far, the most adopted option has been diesel generators that have a relatively low initial investment cost but carry health and environmental risks. A viable alternative is solar photovoltaic systems; however, the initial investment is much higher compared to diesel generators, creating a barrier for many Nigerians. Part one of this thesis addresses making cleaner electricity generation through solar PV systems more attainable, increasing access to more reliable electricity, and reducing or eliminating the use of diesel generators. It proposes a pathway for securing residential solar PV systems with the cost covered through fuel savings and enabled by an effective policy that improves access to financing options. Leveraging real data from a monitoring campaign in Lagos, the commercial hub of Nigeria, results show an opportunity to reduce or eliminate the use of diesel generators by applying fuel cost savings to finance solar PV systems. The second part of this thesis addresses Nigeria's commercial sector, which has been significantly hampered due to the poor availability of reliable electricity. Nearly half of the firms doing business in Nigeria have identified electricity as a major constraint, with over a quarter of them listing electricity as their biggest obstacle. The business losses due to electrical outages are significant, with losses averaging about 16% of annual sales. The lack of access to reliable electricity is one of the biggest challenges to economic growth in Nigeria. A means of powering the commercial sector in Nigeria using urban swarm electrification is proposed. This thesis outlines a conceptual framework for using a distributed network made up of grid-connected home solar PV systems as a viable option for providing the commercial sector with more reliable access to electricity. It further addresses the policy implications for the commercial sector with the enablement of more electrification options, implications that include strong economic impact, and the expansion and creation of new industries.

In the summer of 2007, a single neighbourhood in downtown Toronto contributed at least 13 percent of all residential grid???tie solar photovoltaic (PV) systems sold in the Canadian province of Ontario. On average, PV purchaser households produced 37 percent as much electricity as they consumed. This research investigates solar energy adoption in a community case study. Specifically, it investigates why some residents who sign up for a solar resource assessment through a community solar energy initiative (CSEI) decide to purchase, and others decide not to purchase in the short???term. Characteristics and perceptions of potential adopters are analyzed to better understand their motivations and barriers to adoption. Community energy projects became an official public policy goal in Ontario, with the passing of the Green Energy and Green Economy Act in 2009. Approximately 80 percent of Ontario???s anticipated generation capacity will need to be built, replaced or refurbished within 15 years. In this context, the Ontario Ministry of Energy, Ontario Power Authority, and Deloitte (one of Canada???s leading professional services firms), have partnered with a ???green benefit??? fund, the Community Power Fund, to help local community groups access resources to develop and establish renewable energy projects. Understanding solar energy adoption in a community context is therefore important to improve the effectiveness of such policies, including the disbursement of multi???million dollar grant funds. Differences between purchasers and non???purchasers in respect of adoption behaviour were found in this study to cluster around two general themes. The first theme concerns differences in compatibility of both the concept of solar energy systems, and their physical attributes, with characteristics of potential adopter households. Some compatibility issues are straightforward, e.g. availability of roof space with a southern orientation. Others are more complex, involving several interrelated perceptual and socio???demographic factors. For instance, while both purchasers and non???purchasers rated cost as a very important barrier, purchasers rated the motivation of solar energy systems to reduce climate change higher relative to the barrier of high financial costs than did non???purchasers. Purchasers were also more likely to possess a graduate degree, while non???purchasers were more likely to hold a professional degree. The second general theme relates to potential adopters??? trust and stake in the ability of the community???based initiative to reduce barriers in the adoption process. Since two types of solar energy systems are considered in the case study???PV and thermal (hot water)???differences are explored between each of three respondent groups: solar PV purchasers, solar hot water (SHW) purchasers, and non???purchasers. iv Surveys were used to gather data on adopter perceptions and characteristics. A participatory research design helped identify the research topic. Two main bodies of literature???community???based social marketing (CBSM) and diffusion of innovations theory???were drawn upon to conceptualize the adoption process and interpret the survey findings. These include five models of human behaviour that can be used to guide the design of CBSM campaigns. Diffusion theory was used as a basis for discussing ???perceived innovation attributes???. The study takes an integrated approach by considering both social and technical aspects of solar energy adoption, together with the issues of fuel substitution and household electricity demand.

Indiana University-Purdue University Indianapolis (IUPUI)<br>This thesis presents a converter topology for photovoltaic panels. This topology minimizes the number of switching devices used, thereby reducing power losses that arise from high frequency switching operations. The control strategy is implemented using a simple micro-controller that implements the proportional plus integral control. All the control loops are closed feedback loops hence minimizing error instantaneously and adjusting efficiently to system variations. The energy management between three components, namely, the photovoltaic panel, a battery and a DC link for a microgrid, is shown distributed over three modes. These modes are dependent on the irradiance from the sunlight. All three modes are simulated. The maximum power point tracking of the system plays a crucial role in this configuration, as it is one of the main challenges tackled by the control system. Various methods of MPPT are discussed, and the Perturb and Observe method is employed and is described in detail. Experimental results are shown for the maximum power point tracking of this system with a scaled down version of the panel's actual capability.

Research Doctorate - Doctor of Philosophy (PhD)<br>In recent years, a rapid and dramatic increase in electrical power generation from renewable energy sources has been observed in many countries. Rapid increases in grid-connected small-scale solar photovoltaics (PV) have been driven by government incentives and renewable energy rebates, including residential feed-in tariffs and the financial policy of net metering. However, new challenges arise in balancing the generation of electricity with variable demand at all times as traditional fossil fuel-fired generators are retired and replaced with intermittent renewable electricity sources. This thesis looks at ways to balance distributor and customer benefits of battery storage co-located with solar PV, with a view to facilitating continual increases in grid-connected solar PV. Two issues that arise when accommodating significant residential-scale PV generation are addressed: the first is reverse power flow that leads to considerable voltage rise; the second corresponds to peak loads that occur infrequently, but potentially lead to the need for costly network augmentation when PV generation is unavailable. The benefits associated with addressing these two distributor issues are balanced with the benefit of scheduling battery storage to improve operational savings that accrue to customers. Conventional approaches to managing peak loads and reverse power flows in distribution networks vary from country-to-country, since they are often driven by government policies and regulation. In the Australian context, the first part of the thesis introduces typical costs associated with the design and operation of electrical networks to assess the economic viability of large-scale energy storage. We also introduce a publicly available dataset consisting of load and rooftop PV generation for 300 de-identified Australian residential customers in a distribution network. All simulation-based results in the thesis incorporate data from this publicly available dataset. The second part of the thesis considers potential savings that accrue to residential customers that co-locate battery storage with solar PV. We address reverse power flow and peak-loads coincident with peak pricing periods where the residential customer designs battery charge and discharge schedules. This leads us to a constrained optimization-based problem that we formulate as a quadratic program. The third part of the thesis focuses on coordinated approaches to charge and discharge residential battery storage. Emphasis is given to the management of bi-directional power flows in a distribution grid, and the maintenance of supply voltages within prescribed limits. This has motivated a novel approach to Adaptive-Receding Horizon Optimization (A-RHO). We implement our A-RHO approach in a GridLAB-D model of an Australian distribution network to assess the distributor beneits.