A presente dissertação descreve o experimento desenvolvido com a finalidade de avaliar um sistema de bombeamento de água acionado por dois painéis fotovoltaicos instalado nas dependências da Universidade Tecnológica Federal do Paraná – UTFPR, Câmpus Medianeira, estado do Paraná, Brasil. O município está localizado no oeste paranaense com 25º17’43” Latitude sul, 54º03’38” Longitude oeste e com altitude de 500,7 metros. O sistema trabalhou em situação real de funcionamento, bombeando água a uma altura de 20 metros. Foram coletados dados de fevereiro de 2005 a novembro de 2005; utilizou-se um coletor de dados computadorizado da marca Campbell Scientific INC., o que possibilitou adquirir e armazenar os valores de irradiância no plano do painel, tensão e corrente gerada, temperatura no painel, pressão e vazão. A leitura dos dados foi realizada com freqüência de 1 hertz e armazenada a cada 1 minuto. Através de cálculos obtiveram-se os valores de potência e eficiência do sistema e a potência hidráulica. O solstício de inverno apresentou eficiência de 9,58% com bombeamento diário de 2.056,44 litros, enquanto que o solstício de verão apresentou eficiência de 9,07% com bombeamento diário de 2.377,21 litros. A maior eficiência nos dias de inverno está atrelada às menores temperaturas nestes dias se comparado aos dias de verão e o fator que provocou uma maior vazão de água bombeada nos dias de verão está ligado ao tempo de insolação solar que é maior se comparado aos dias de inverno. O total de água bombeada durante o período do experimento foi de 435.042,20 litros. / The current dissertation describes an experiment to evaluate a water pumping system activated by two photovoltaic panels installed at The Federal Technological University of Paraná – UTFPR, Medianeira Campus, in the State of Paraná, Brazil. The city of Medianeira’s latitude and longitude are 25º17’43”south and 54º03’38”west respectively, with an altitude of 500.7 meters (1,642.72 feet). The system operated in a real working situation, pumping water to a 20 meters (65.62 feet) elevation. Data were collected, from February 2005 to November 2005, by means of a computerized data collector made by Campbell Scientific Inc that made possible collecting and applying irradiance values in the panel plane, generated current and tension, panel temperature, pressure and consume. Data readings were made at a 1-hertz frequency and stored every minute. Through calculi, the system efficiency and energy values and hydraulic strength were obtained. Winter solstice showed 9.58% efficiency with daily pumping of 2,056.44 liters (543.14 gallons) whereas summer solstice confirmed 9.07% efficiency with daily pumping of 2,377.21 liters (627.86 gallons). Winter day’s highest efficiency is associated to the lowest temperature in those days compared to summer days, and the factor that prompted larger pumped water consume, during summer days, was related to solar insulation time that is longer if compared to winter days. Total water pumped during the experiment period was 435,042.20 liters (114,900.99 Gallons)

D.Ing. / Low system efficiency is a critical problem in photovoltaic (PV) applications due to low efficiency of solar cells. Despite this shortcoming, stand-alone PV systems, have proven to be economical and reliable choices in some applications such as telecommunications, vaccine refrigeration and water pumping in remote locations. In this study, CAD algorithms for the design of PV water pumping systems have been developed with the objective of maximizing the conversion efficiency from the solar irradiation to the potential energy of water by taking into account the variations in the pumping head. The study starts by developing loss models of various sub-systems in the photovoltaic dc and ac motor drive water pumping systems. Using MathCad, these models are then used in the simulation of the system. The simulation results are verified experimentally using their equivalent circuit configurations. The efficiency of the array, the pump and the motor are found to be the most critical parameters for the performance of the systems. The efficiencies of other components, such as the inverter, have also been shown to have a significant effect. The study has shown that for operation at the maximum power point, the inclusion of a maximum power tracker is necessary in a dc motor drive system but may be eliminated in PWM inverter-fed induction motor drive systems through proper matching of the system components. The study has further shown that matching of the drive system and the load with the insolation is essential, since maximum system efficiency occurs at a specific head, which varies as the insolation changes. Prior investigation of site insolation variations is therefore a critical requirement.

Electricity is a perishable commodity; once it is generated it needs to be consumed or stored. Electric energy storage provides both power and energy capacity. Power capacity applications reduce the need for generation, while energy capacity allows for energy consumption to be decoupled from generation. Previous research was done to develop an algorithm for determining the power (MW) and energy (MWh) capacities of a battery energy storage system (BESS) to mitigate the adverse impacts of high levels of photovoltaic (PV) generation. The algorithm used a flat feeder profile, and its performance was demonstrated on the equinoxes and solstices. Managing feeder power leads to fewer voltage fluctuations along the length of the feeder, potentially mitigating load management issues caused by variability of renewable generation and load profile. These issues include lighting flicker, compressor seizing, equipment shut-off, loss of motor torque, frequent transformer tap changes and even voltage collapse due to loss of reactive power support. The research described in this thesis builds on this algorithm by incorporating a smoothed feeder profile and testing it over an entire year. Incorporating a smoothing function reduces the requisite BESS energy capacity necessary to provide firming and shaping to accommodate the stochastic nature of PV. Specifically, this method is used to conduct a year-long study on a per second basis, as well as a one-minute basis, for a distribution feeder. Statistical analytical methods were performed to develop recommendations for appropriately sizing the BESS. This method may be used to determine the amount of PV generation that could be installed on a distribution feeder with a minimal investment in the BESS power and energy capacities that would be required to manage the distribution feeder power. Results are presented for PV penetration levels of 10%-50% of the distribution feeder capacity and show that the use of a smooth feeder profile reduces the required energy capacity by a minimum factor of 10 when compared to a flat feeder profile. Results indicated that it is sufficient to have a one-minute sampling rate, as it provides the necessary granularity to model cloud-induced fluctuations. This method can be applied to any distribution feeder where a load profile and a PV profile are available.

A series of 28 square-planar dithiol(diimine)platinum(II) chromophoric complexes have been synthesized, characterized, and evaluated for potential efficacy in sensitization of solid state photovoltaic devices to the near-infrared regions of the electromagnetic spectrum. The effect of molecular stacking in the solid state and self-association in solution are shown to influence spectral, electronic, and magnetic properties of the chromophores. Such properties are investigated in the pure form and as partners in donor-acceptor charge transfer adducts. Finally, selected chromophores have been incorporated into single layer schottky diodes as neat films and as dopants in multi-layer organic photovoltaic devices. Evaluation of the devices internal quantum efficiency and voltage-current was measured as proof of concept.

Indiana University-Purdue University Indianapolis (IUPUI) / This thesis deals with three phase inverters and the different control strategies that can be associated with an inverter being used together. The first part of this thesis discusses the present research in the fields of PV panels, motor drive systems and three phase inverters along with their control. This control includes various strategies like MPPT, Volts-Hertz and modulation index compensation. Incorporating these techniques together is the goal of this thesis. A new topology for operating an open end motor drive system has also been discusses, where a boost converter and a flyback converter have been used in cascade to run a three phase motor. The main advantage of this is increasing the number of levels and improving the quality of the output voltage, not to mention a few other benefits of having the proposed circuit. A new algorithm has also been designed for starting and stopping the motor, which controls the current drawn from the power source during starting.

PV Inverters have the task of tracking the maximum power point (MPP), and regulating the solar energy generation to this optimal operation point. The second task is the conversion of direct current produced by the solar modules into alternating current compatible with the grid. A new inverter approach such as a single phase micro inverter is emerging aimed to overcome some of the challenges of centralized inverters. As a counterpart to the central inverter, a micro inverter is a small compact module attached directly to each solar panel. To provide for the constantly increasing demand for a small size, light weight and high efficiency micro inverter, soft switching power conversion technologies have been employed. The switching stress can be minimized by turning on/off each switch when the voltage across it or the current through it is zero at the switching transition. With the addition of auxiliary circuits such as auxiliary switches and LC resonant components the so called soft switching condition can be achieved for semiconductor devices. Four main purposes to investigate the soft switching technologies for singlephase micro-inverter are: (1) to improve overall efficiency by creating the favorable operating conditions for power devices using soft-switching techniques; iv (2) to shrink the reactive components by pushing the switching frequency to a higher range with decent efficiency. (3) to ensure soft switching does not exacerbate inverter performance, meaning all conventional PWM algorithms can be applied in order to meet IEEE standards. (4) to investigate which soft switching techniques offer the cheapest topology and control strategy as cost and simple control are crucial for low power inverter applications. An overview on the existing soft-switching inverter topologies for single phase inverter technology is summarized. A new quasi resonant DC link that allows for pulse- width- modulation (PWM) is presented in this thesis. The proposed quasi resonant DC link provides zero-voltage switching (ZVS) condition for the main devices by resonating the DC-link voltage to zero via three auxiliary switches and LC components. The operating principle and mode analysis are given. The simulation was carried out to verify the proposed soft switching technique. A 150W 120VAC single-phase prototype was built. The experimental results show that the soft switching for four main switches can be realized under different load conditions and the peak efficiency can reach 95.6%. The proposed quasi DC link can be applied to both single-phase and three-phase DC/AC micro inverter. In order to boost efficiency and increase power density it is important to evaluate the power loss mechanism in each stage of operation of the micro inverter. Using the datasheet parameters of the commercially available semiconductor switches, conduction and switching losses were estimated. This thesis presents a method to analyze power losses of the new resonant DC link inverter which alleviates topology v optimization and MOSFET selection. An analytical, yet simple model for calculating the conduction and switching losses was developed. With this model a rough calculation of efficiency can be done, which helps to speed up the design process and to increase efficiency.

Photovoltaic solar cells can generate electricity directly from sunlight without emitting harmful greenhouse gases. This makes them ideal candidates as large scale future energy producers for the global energy economy. Ideally, solar cells should be efficient and inexpensive to compete in the global energy market. Unfortunately, a number of fundamental limitations exist for the efficiency due to fundamental loss mechanisms of the semiconductor materials used to make solar cells. One of the dominant loss mechanisms from a conventional silicon solar cell is the transparency of sub-bandgap near-infrared photons. Up-conversion is an optical process involving the sequential absorption of lower energy photons followed by luminescence of a higher energy photon. This mechanism could be exploited to minimise photovoltaic sub-bandgap losses. Rare-earth doped materials have ideal up-conversion luminescent properties and have been utilised for many near-infrared to visible applications. This thesis investigates the near-infrared to near-infrared up-conversion processes required for the sub-bandgap photon utilisation within a silicon photovoltaic device. Various sodium yttrium fluoride phosphors doped with rare-earths were characterised theoretically and experimentally. Erbium doped phosphors were found to be ideal for single wavelength power dependent investigations for the non-linear up-conversion processes. The radiative and non-radiative rates of various erbium doped sodium yttrium fluoride phosphors have been approximated and compared with experimental photoluminescence results. These phosphors have been applied to the rear of a bi-facial silicon solar cell and an enhancement in the near-infrared region has been demonstrated. An external quantum efficiency close to 3.4% was measured at 1523nm under 6mW laser excitation. The non-linear dependence on incident pump power has been investigated along with the dominant up-conversion mechanisms involved. It can be concluded that up-conversion phosphors can enhance the near-infrared spectral response of a silicon device. These phosphors have high luminescent efficiencies once up-conversion occurs, but suffer from poor infrared absorption and low up-conversion efficiencies. The results from this study show that relatively high doping levels of selected rare-earths into low phonon energy crystals can improve the absorption and luminescent properties of the phosphor.

The Master's Thesis research focuses on analyzing the possibilities of using Direct Current distribution systems to distribute power to end users. Considering the shift in load types in the past few decades and also a growing demand of distributed generation, DC distribution can potentially offer higher efficiencies and cost savings to utilities. The incorporation of DC distribution offers the opportunity to eliminate multiple conversion stages for devices which are powered using DC electricity. The integration of power sources such as photovoltaics and fuel cells, which produce DC power, offer further incentives to consider the use of DC systems. Using DC systems can help eliminate the conversion losses associated with rectifiers and inverters which would be part of the infrastructure if AC distribution was used. In the literature, the study of DC distribution has been limited to customized systems. The objective of this research is to analyze DC distribution when applied to systems based on standard IEEE test feeder systems. The IEEE 13 node test feeder and the IEEE 37 node test feeder will be used as the basis for the analysis. Issues such as associated costs, protection and integration of appliances will also be addressed.

In the current global market, there are plenty solutions for the savings of energy in the different areas of consumption in buildings: Green roofs and walls, cool roofs, daylighting, motion sensors, and others but there are very few sources of renewable energy at the reach of a common person in residential (smaller) scale. Photovoltaic systems are the most well-know and reliable process of harvesting energy at this small scale. The relationship between energy demand and energy production when installing a photovoltaics system in a residence is one of the main drivers while making a decision at the time of purchasing a system. However, architectural decisions in early stages may influence, enhance or even decrease the possible energy generation and interior performance, thus influencing the possible return of investment. This study evaluates the possible architectural variations that may be beneficial or disadvantegous at a particular city and other circumstances. From, roof, angle, location, roof articulation, layout articulation , shading devices and others, this paper shows a spectrum of convenient and inconvenient projects due to current conditions like climate, solar radiation, typical construction, electricity rates and government incentives. As a conclusion a hierarchy of architectural elements when being used with photovoltaics is developed to demonstrate that a common user can strategically play with architectural features of his/her house to take the most out of the system.

Solar photovoltaic (PV) systems are distributed energy sources that are an environmentally friendly and renewable source of energy. However, solar PV power fluctuates due to variations in radiation and temperature levels. Furthermore, when the solar panel is directly connected to the load, the power that is delivered is not optimal. A maximum peak power point tracker is therefore necessary for maximum efficiency. A complete PV system equipped maximum power point tracking (MPPT) system includes a solar panel, MPPT algorithm, and a DC-DC converter topology. Each subsystem is modeled and simulated in a Matlab/Simulink environment; then the whole PV system is combined with the battery load to assess the overall performance when subjected to varying weather conditions. A PV panel model of moderate complexity based on the Shockley diode equation is used to predict the electrical characteristics of the cell with regard to changes in the atmospheric parameter of irradiance and temperature. In this dissertation, five MPPT algorithms are written in Matlab m-files and investigated via simulations. The standard Perturb and Observe (PO) algorithm along with its two improved versions and the conventional Incremental Conductance (IC) algorithm, also with its two-stage improved version, are assessed under different atmospheric operating conditions. An efficient two-mode MPPT algorithm combining the incremental conductance and the modified constant voltage methods is selected from the five ones as the best model, because it provides the highest tracking efficiencies in both sunny and cloudy weather conditions when compared to other MPPT algorithms. A DC-DC converter topology and interface study between the panel and the battery load is performed. This includes the steady state and dynamic analysis of buck and boost converters and allows the researcher to choose the appropriate chopper for the current PV system. Frequency responses using the state space averaged model are obtained for both converters. They are displayed with the help of Bode and root locus methods based on their respective transfer functions. Following the simulated results displayed in Matlab environment for both choppers, an appropriate converter is selected and implemented in the present PV system. The chosen chopper is then modeled using the Simulink Power Systems toolbox and validates the design specifications. The simulated results of the complete PV system show that the performances of the PV panel using the improved two-stage MPPT algorithm provides better steady state and fast transient characteristics when compared with the conventional incremental conductance method. It yields not only a reduction in convergence time to track the maximum power point MPP, but also a significant reduction in power fluctuations around the MPP when subjected to slow and rapid solar irradiance changes. / Thesis (M.Sc.Eng)-University of KwaZulu-Natal, Durban, 2011.