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A comparison of 50Hz and high frequency integrated technologies for application in photo-voltaic driven inverters

  • Authors: Claassens, Jonathan Anton
  • Date: 2008-05-22T07:36:03Z
  • Subjects: Electric inverters , Photovoltaic power generation
  • Type: Thesis
  • Identifier: uj:2113 , http://hdl.handle.net/10210/446
  • Description: The purpose of this investigation is to compare high frequency to low frequency (50Hz) technologies. To accomplish this, two highly optimized candidate converters are built to champion each of the inverter classes. Both candidates are constrained to produce the same quasi-sinusoidal output waveforms in identical operating conditions. The low frequency inverter is designed with optimization of its output power quality and accurate loss characterization taken in mind. A new iron core design procedure is proposed that may predict core losses when using non-sinusoidal excitation. Experimental results indicate that it has a promising degree of accuracy. The high frequency candidate is designed using planar integration technology. A topology selection determines that a critical-conduction mode flyback is the most suitable option. Components are added the topology to allow resonant switching for reduced switching losses. Common-mode current arising from good capacitive coupling between windings in the planar coupled inductor is reduced using charge balancing technology. The novelty of the converter lies is in the fact that all passive components, barring the bulk of the input capacitance and the output capacitance, are incorporated into the single planar structure. Finally, a comparison of the inverters is made in the categories of power quality, regulation, efficiency, robustness and applicability to the application. The high frequency inverter is found to promise substantial advantages over the low frequency variety in most of these elements. , Dr. I.W. Hofsajer
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A novel 9-level multilevel inverter based on 3-level NPC/H-bridge topology for photovoltaic applications

An experimental and computational investigation of swirl generators in a solar thermal cell

An investigation into the thermo-fluid design and technical feasibility of a practical solar absorption refrigeration cycle

  • Authors: Santos, Nelson de Sousa Pedro dos
  • Date: 2010-03-15T06:30:41Z
  • Subjects: Solar energy , Photovoltaic power generation , Solar cells
  • Type: Thesis
  • Identifier: uj:6672 , http://hdl.handle.net/10210/3077
  • Description: M.Eng. , The need and problem was originated from the trends of the earths dwindling energy resource. As time progresses humans are becoming more aware of need to use so called “alternative energy sources” to alleviate the main energy converters i.e. power stations. The student was tasked with investigating the thermal performance of a solar powered refrigeration cycle (prototype) that could: produce enough refrigeration effect that it replaces the standard home vapour compression unit, used for cooling or freezing of foods, heats up a geyser sufficiently to have hot water for a common house hold, has excess energy to heat or cool liquid or air based environments and has the potential to lower the electrical bill of a house. The introductory step was to obtain the thermo fluid properties of aqua ammonia solutions. A setback came about when determining the aqua ammonia properties. There were too many conflicting properties being yielded by six different authors. In an attempt to gain confidence in only one author a comparison table was prepared. The table compared the six authors to each other. By looking at all the values compared it brought great clarity to the problem. When continuing the research into the fundamental law approach of solving for the cycle new findings were made. Initially very little comprehensive studies were done which explained in fundamental laws to solve for the absorption cycle. After extensive reviewing of a detailed study on how to solve for absorption refrigeration cycles, then it was able to begin improving on the thermo – fluid design of the cycle. As cycle and component design began to progress the train of thought began to steer in a direction. Each component needed to be detail designed. The advantage of having each component specifically catered for in the cycle design was that it would increase the cycle efficiency. In this way it would ensure that during the concept generation phase the functioning of each component was clear, thereby enabling a clear understanding of how components would compliment each other in a cycle. A mode of solving for the cycle was to endeavour that all parameters could be calculated unambiguously, with the aid of computerisation. Testing was carried out on a real life commercial thermal siphoning machine in order to realistically understand how absorption refrigeration works and gain experience. At the end of the study the most important result is that the dissertation research shows strong evidence that it will be possible to create a device which can fulfil the four tasks listed above. Another result is a program which is a refined cycle design of the pump absorption type refrigeration. The program solves for points along the cycle. Lastly it was found that even though EES was the simpler program to use for aqua ammonia solution properties it was the only program which catered for sub cooling and super heating.
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Calculating the optimum solar panel orientation for Gauteng Province

  • Authors: Nethwadzi, Lutendo Christopher
  • Date: 2019
  • Subjects: Solar power plants , Solar thermal energy , Photovoltaic power generation , Solar system
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/403573 , uj:33825
  • Description: Abstract : This thesis presents the calculation of optimum solar panel orientation for Gauteng Province by adapting known sky transparency models to actual irradiance data. Solar irradiance losses in the atmosphere are traditionally quantified by the Linke turbidity factor. This study analyses the global irradiance measured in Gauteng and attempts to reproduce the data in terms of irradiance models, such as Aras et al (2006) model, Tsubo et al (2003) model, Scharmer and Greif (2000) model and the Slob Algorithm (2006) model. Some of these models were adapted for local atmospheric conditions, except for the Aras et al (2006) model and the Scharmer and Greif (2000) model. The irradiance energy yields of a solar panel were mod- elled taking into account orientation, season, time of day, and atmospheric losses. The analysis models the irradiance using the Linke turbidity factor. This considers the estimation of the direct component and the diffuse component, which are then summed with an effort to match the measured irradiance and modelled irradiance yield. The Linke turbidities determined in this manner are then compared with corresponding values given in an online solar irradiance calculation tool called PVGIS... , M.Sc. (Physics)
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Comparative study of different photovoltaic MPPT techniques under various weather conditions

  • Authors: Farayola, Adedayo Mojeed
  • Date: 2017
  • Subjects: Photovoltaic power systems , Photovoltaic power generation
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/262879 , uj:27785
  • Description: M.Ing. (Electrical Engineering) , Abstract: Photovoltaic (PV) energy has become the most growing renewable energy source that serves as an alternative to fossil energy as it is considered cheap, less polluted, etc. Photovoltaic system works under both uniform irradiance and partial shaded weather conditions and exhibits both local peak power and global peak power during partial shaded conditions. Maximum power point tracking (MPPT) techniques are being used in PV systems to track the local power peak. However, MPPT systems may fail to track the global peak power. Online MPPT techniques such as Perturb&Observe (P&O) and incremental conductance (IC) are considered economical and easy to implement. However, these online methods underachieve due to some flaws such as oscillating power near maximum power point (MPP) and poor response owing to the sudden change in irradiance with P&O and IC. MPPT techniques are algorithms used in photovoltaic (PV) system to extract maximum power from the PV panel. Offline techniques such as the curve fitting polynomial (CFP) technique use prediction and fitting method in order to track the MPP. However, lower order CFP does not extract maximum power from the panel due to inaccurate fitting of the real P-V curve. The use of supervised machine learning techniques which include artificial neural network (ANN) and artificial neuro-fuzzy inference system (ANFIS) have improved the maximum power point tracking (MPPT) process which increased the PV systems efficiency. This first contribution of this dissertation presents a reconfiguration approach that uses series-connected distributive MPPT (DMPPT). DMPPT is used to track the global peak in order to extract maximum power from the PV array system under uniform irradiance and partial shaded weather conditions. The second contribution is the implementation of improved models of online Perturb&Observe and modified incremental conductance MPPT techniques that work well under sudden change in irradiance, temperature, and with minimal oscillating power near MPP. The third contribution is the state of the art of the sixth-order curve fitting polynomial MPPT technique that can extract maximum power from a PV panel under varied weather conditions. The fourth contribution is to introduce the use of SVM classifier for optimization and MPPT purpose in a PV system...
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Computer aided design of systems for solar powered water pumping by photovoltaics

  • Authors: Lujara, Nelson Kakuru
  • Date: 2012-08-23
  • Subjects: Photovoltaic power systems , Photovoltaic power generation , Solar energy , Computer-aided design
  • Type: Thesis
  • Identifier: uj:3116 , http://hdl.handle.net/10210/6537
  • Description: 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.
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Harvesting solar radiation in hybrid transparent photovoltaic façade’s in Southern Africa

  • Authors: Gevers, Richard Heinrich
  • Date: 2015
  • Subjects: Photovoltaic power generation , Solar thermal enery , Solar radiation
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/213262 , uj:21126
  • Description: Abstract: Renewable energy is the buzzword in the world today, from the drive to reduce electricity costs to combating climate change by reducing harmful Green House Gas (GHG) emissions. Innovative technologies are shaping the future. One such technology is the transparent hybrid solar façade (window), developed by TropiGlas Technologies [1]. This transparent hybrid solar façade not only harvests solar energy using the Photovoltaic (PV) effect, but also shields against harmful solar radiation and improves thermal efficiencies by limiting selected electromagnetic wavelengths that heat buildings and homes. This study objectively quantifies the merits of using a transparent hybrid solar façade for solar harvesting. Best practices and evaluation criteria for a transparent hybrid solar façades are quantified, through use of experimental and recorded field data. The potential is to use a transparent hybrid solar façade for energy harvesting where circumstances require energy from non-grid sources. The potential to overcome environmental constraints such as building floor ratio, zero carbon buildings, and green standards can be achieved utilising this innovative concept. This dissertation considers and further investigates power generation, utilising this novel approach to hybrid transparent solar façades, in Southern Africa. Providing an evaluation framework for technologies that provide energy generation included in the building envelope. A spectral irradiation model specific to Southern Africa is also presented and discussed. Investigations performed during a two-year period at a commercial pilot site and isolated control tests helped to evaluate the feasibility of such a product against the impacts of location, design, geographical and meteorological conditions relevant to Southern Africa. Results obtained from the sample panel provided, varied when compared to theoretical simulations and laboratory experiments. It was found that when the panel was placed vertically as to match the pilot site, that as expected the north facing panel produced the highest energy output. However, a horizontal and “optimal” angle placement achieved much better results than the vertically installed panel. Overall this meant that a lower than expected annual output was recorded. , M.Ing. (Electrical and Electronic Engineering)
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Impact of photovoltaic plants on voltage sags

Modeling and simulation of nanostructured copper oxides solar cells for photovoltaic application

  • Authors: Enebe, George Chukwuebuka
  • Date: 2019
  • Subjects: Photovoltaic power generation , Nanostructured materials
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/424718 , uj:36333
  • Description: Abstract: The increasing global population and demand for clean and sustainable energy has led to increased research on affordable and efficient energy materials. Solar energy materials are one of those promising options. There is increased research on nanostructured metal oxide solar cell as an option for inexpensive, clean and efficient solar cells material. Copper oxide based solar cells are among those attracting interest although the efficiency is still low. This study investigates the numerical modeling and simulation of nanostructured copper oxide (cuprous and cupric oxide) heterojunction solar cells for photovoltaic applications. This is with a view to providing an optimized cell efficiency to aid experimentation and the development of high-efficiency metal oxide solar cells. The inspiration for this investigation is to give premise for experimental design for affordable, non-harmful and efficient alternative material for silicon-based solar cells. This was performed using Solar cells capacitance simulator (SCAPS). The optimization was performed by varying the effect of film thickness and by varying the effect of annealing temperature on properties of the copper oxide solar cells using SCAPS for the numerical analysis. The simulation and optimization was modeled firstly by varying the thickness of both the absorber layer and the buffer layers of Cu2O/TiO2 and CuO/TiO2 pn nanostructured heterojunction solar cells. The input parameter for SCAPS, obtained from literatures includes; temperature of 300K for the film thickness, input power of 1000W/m2 using illumination of AM1.5 lamp, under varying thickness of 0.5 μm to 10.0 μm for the absorber layers (Cu2O and CuO) and 0.05 μm to 6.0 μm for the buffer layer (TiO2) respectively. The simulated solar cell displayed a short-circuit current (Jsc) of 24.0764 A and 26.0516 A, open-circuit voltage (Voc) of 1.0486 V and 0.0435 V, fill factor (FF) of 63.20 % and 71 % with an efficiency (η) of 1.6 % and 8.05 % respectively, at an absorber layer thickness of 500 nm and buffer layer thickness of 50nm. Furthermore, the defect density was obtained for each solar cell. Secondly, the Cu2O/TiO2 and CuO/TiO2 pn nanostructured heterojunction solar cells was numerically analysed under varied annealing condition. Three annealing conditions were considered i.e. the as-deposited (300K), air and nitrogen annealed (423.15 K). Other working conditions include; an illumination of AM 1.5G with a 500 W Xenon lamp representing the sunlight. For this simulation, silver was used as the electrode/contact. The absorber layer thickness was 2000 nm and buffer layer thickness was 200 nm. The simulation report showed that nitrogen... , M.Ing. (Mechanical Engineering Science)
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Monitoring and control of the performance for a photo-voltaic system DC-DC converter using frequency shift keying

  • Authors: Ali, Ahmed Abdi Yusuf
  • Date: 2015-09-14
  • Subjects: Photovoltaic power generation , Frequency changers
  • Type: Thesis
  • Identifier: uj:14092 , http://hdl.handle.net/10210/14524
  • Description: M.Ing. , Photovoltaic (PV) systems are considered as renewable resources of energy that are utilized in the conversion of direct and diffuse solar radiation to electric power. These systems are considered as environmentally friendly energy resources as they reduce pollution. These systems’ produced power depends on the radiation of the sun as well as the temperature, the impedance of the load, and the unfitted parameters in PV systems. In this field, the PV systems and DC-DC converters will be explored in both configuration (the open loop and closed loop systems), whilst their implementation will be designed as a closed loop system. The success of the system depends on the algorithm of the maximum power point tracking that catches the maximum sunshine radiation amount to generate the maximum electrical power. This system simulation and hardware implementation will be done through the Proteus program and real components integration ...
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Solar irradiance calculations for solar power generating devices operating in South African conditions

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