It is well known that the efficiency of a photovoltaic (PV) module is strongly impacted by its temperature such that higher temperatures lead to lower energy conversion efficiencies. An accurate measurement of the temperature de-rating effect, therefore, is vital to the correct interpretation of PV module performance under varied environmental conditions. The current work investigates and compares methods for performing measurements of module temperature both in the lab and in field-test environments. A comparison of several temperature measurement devices was made in order to establish the ideal sensor configuration for quantifying module operating temperature. Sensors were also placed in various locations along a string of up to eight photovoltaic modules to examine the variance in operating temperature with position in the string and within a larger array of strings.

Renewable energy-hydrogen systems for remote area power supply (RAPS) constitute an early niche market for sustainable hydrogen energy. The primary objective of this research has been to investigate the possibility of direct coupling of a PV array to a proton exchange membrane (PEM) electrolyser by appropriate matching of the current-voltage characteristics of both the components. The degree to which optimal matching can be achieved by direct coupling has been studied both theoretically and experimentally. A procedure for matching the maximum power point output of a PV array with the PEM electrolyser load to maximise the energy transfer between them has been presented. The key element of the matching strategy proposed is to vary the series-parallel stacking of individual cells in both the PV array and the PEM electrolyser so that the characteristic current (I) -voltage (V) curves of both the components align as closely as possible. This procedure is applied to a case study of direct coupling a PV array comprising 75 W panels (BP275) to a PEM electrolyser bank assembled from 50 W PEM electrolyser stacks (h-tec StaXX7). It was estimated theoretically that the optimal PV-electrolyser combination would yield an energy transfer of over 94% of the theoretical maximum on annual basis. This combination also gave the lowest hydrogen production cost on a lifecycle basis. An experimental test of this theoretical result for direct coupling was conducted over a period of 728 hours, with an effective direct-coupling operational time of about 467 hours (omitting the hours of zero solar radiation). Close agreement between the theoretically predicted and actual energy transfer from the PV array to the electrolyser bank in this trial was found. The difference between theoretical and experimental hydrogen production was less then 1.2%. The overall solar-to-hydrogen energy conversion efficiency was found to be 7.8%. The electrolysers were characterised before and after the direct coupling experiment, and showed a small decline in Faraday efficiency and energy efficiency. But this decline was less than the uncertainties in the measured values, so that no firm conclusions about electrolyser degradation can be drawn at this stage. Another direct-coupling experiment, using a larger scale PV-electrolyser system, that is, a 2.4 kW PV array at RMIT connected to the 'Oreion Alpha 1' stand-alone 2 kW PEM electrolyser developed by the CSIRO Energy Technology, was also successfully conducted for a period of 1519 hours (with 941 hours of effective operational time of the electrolyser). Energy-efficient direct coupling of a PV array and electrolyser as examined in this thesis promises to improve the economic viability of solar-hydrogen systems for remote power supply since the costs of an electronic coupling system employing a maximum power point tracker (MPPT) and dc-to-dc converter (around US$ 700/ kW) are avoided.

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abstract: Utility scale solar energy is generated by photovoltaic (PV) cell arrays, which are often deployed in remote areas. A PV array monitoring system is considered where smart sensors are attached to the PV modules and transmit data to a monitoring station through wireless links. These smart monitoring devices may be used for fault detection and management of connection topologies. In this thesis, a compact hardware simulator of the smart PV array monitoring system is described. The voltage, current, irradiance, and temperature of each PV module are monitored and the status of each panel along with all data is transmitted to a mobile device. LabVIEW and Arduino board programs have been developed to display and visualize the monitoring data from all sensors. All data is saved on servers and mobile devices and desktops can easily access analytics from anywhere. Various PV array conditions including shading, faults, and loading are simulated and demonstrated. Additionally, Electrical mismatch between modules in a PV array due to partial shading causes energy losses beyond the shaded module, as unshaded modules are forced to operate away from their maximum power point in order to compensate for the shading. An irradiance estimation algorithm is presented for use in a mismatch mitigation system. Irradiance is estimated using measurements of module voltage, current, and back surface temperature. These estimates may be used to optimize an array’s electrical configuration and reduce the mismatch losses caused by partial shading. Propagation of error in the estimation is examined; it is found that accuracy is sufficient for use in the proposed mismatch mitigation application. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2016

Renewable energy source plays an important role in the energy cogeneration and distribution. Traditional solar-based inverter system is two stages in cascaded, which has a simpler controller but low efficiency. A new solar-based single-stage grid-connected inverter system can achieve higher efficiency by reducing the power semiconductor switching loss and output stable and synchronized sinusoid current into the utility grid. Controlled by the digital signal processor, the inverter can also draw maximum power from the solar array, thereby maximizing the utilization of the solar array. In Chapter 1, a comparison between the traditional two-stage inverter and the single-stage inverter is made. To increase the ability of power processing and enhance the efficiency further, a full-bridge topology is chosen, which applies the phase-shift technique to achieve zero-voltage transition. In Chapter 2, average-mode and switch-mode Pspice simulations are applied. All the features of the inverter system are verified, such as stability, zero voltage transition and feed-forward compensation, etc. All these simulation results provide useful design tips for prototyping. In Chapter 3, a phase-shift controller is designed based on UCC3895. Also, a detailed design procedure is given, including key components selection, transformer and inductor design and driver circuits design. In Chapter 4, experimental results of a prototype DC/DC converter are presented and analyzed. By optimization of the circuit, the problems of the prototype are solved and the prototype is working stably. The thesis' conclusion is given in Chapter 5.

abstract: The object of this study was a 26 year old residential Photovoltaic (PV) monocrystalline silicon (c-Si) power plant, called Solar One, built by developer John F. Long in Phoenix, Arizona (a hot-dry field condition). The task for Arizona State University Photovoltaic Reliability Laboratory (ASU-PRL) graduate students was to evaluate the power plant through visual inspection, electrical performance, and infrared thermography. The purpose of this evaluation was to measure and understand the extent of degradation to the system along with the identification of the failure modes in this hot-dry climatic condition. This 4000 module bipolar system was originally installed with a 200 kW DC output of PV array (17 degree fixed tilt) and an AC output of 175 kVA. The system was shown to degrade approximately at a rate of 2.3% per year with no apparent potential induced degradation (PID) effect. The power plant is made of two arrays, the north array and the south array. Due to a limited time frame to execute this large project, this work was performed by two masters students (Jonathan Belmont and Kolapo Olakonu) and the test results are presented in two masters theses. This thesis presents the results obtained on the north array and the other thesis presents the results obtained on the south array. The resulting study showed that PV module design, array configuration, vandalism, installation methods and Arizona environmental conditions have had an effect on this system's longevity and reliability. Ultimately, encapsulation browning, higher series resistance (potentially due to solder bond fatigue) and non-cell interconnect ribbon breakages outside the modules were determined to be the primary causes for the power loss. / Dissertation/Thesis / M.S.Tech Electrical Engineering 2013

M. Tech. (Department of Electronic Engineering, Faculty of Engineering and Technology) --Vaal University of Technology| / Global warming is of increasing concern due to several greenhouse gases. The combustion of fossil fuels is the major contributor to the greenhouse effect. To minimalise this effect, alternative energy sources have to be considered. Alternative energy sources should not only be environmentally friendly, but also renewable and/or sustainable. Two such alternative energy sources are hydrogen and solar energy. The regenerative fuel cell, commonly known as a hydrogen generator, is used to produce hydrogen. The current solar/hydrogen system at the Vaal University of Technology’s Telkom Centre of Excellence makes use of PV array to supply power to an inverter and the inverter is connected to the hydrogen generator. The inverter provides the hydrogen generator with 220VAC. The hydrogen generator has its own power supply unit to convert the AC power back to DC power. This reduces the efficiency of the system because there will be power loss when converting DC power to AC power and back to DC power. The hydrogen generator, however, could be powered directly from a PV array. However, the hydrogen generator needs specific input parameters in order to operate. Three different input voltages with their own current rating are required by the hydrogen generator to operate properly. Thus, a DC-DC power supply unit needs to be designed to be able to output these parameters to the hydrogen generator. It is also important to note that current PV panel efficiency is very low; therefore, the DC-DC power supply unit also needs to extract the maximum available power from the PV array. In order for the DC-DC power supply unit to be able to extract this maximum power, a maximum power point tracking algorithm needs to be implemented into the design. The DC-DC power supply is designed as a switch mode power supply unit. The reason for this is that the efficiency of a switch mode power supply is higher than that of a linear power supply. To reach the objective the following methodology was followed. The first part of the research provided an introduction to PV energy, charge controllers and hydrogen generators. The problem statement is included as well as the purpose of this research and how this research was to be carried out. The second part is the literature review. This includes the background study of algorithms implemented in MPPT’s; it also explains in detail how to design the MPPT DC-DC SMPS. The third part was divided into two sections. The first section is the design, programming and manufacturing of the MPPT DC-DC SMPS. The second section is the simulation of the system as a whole which is the simulation of the PV array connected to the MPPT DC-DC SMPS and the hydrogen generator. The fourth part in the research compared the results obtained in the simulation and practical setup. The last part of the research provided a conclusion along with recommendation made for further research. The simulation results showed that the system works with an efficiency of 40,84%. This is lower than expected but the design can be optimised to increase efficiency. The practical results showed the efficiency to be 38%. The reason for the lower efficiency is the simulation used ideal components and parameters, whereas the practical design has power losses due to the components not being ideal. The design of the DC-DC switch mode power supply, however, indicated that the hydrogen generator could be powered from a PV array without using an inverter, with great success.

Grid connected inverter requires accurate and appropriate sizing which depends on the temperature, inverter operating efficiency, performance ratio, annual system yield and solar radiation characteristics. The aim of this study was to design and size for optimum sizing factor for grid connected inverter. The main component to be considered in any photovoltaic grid connected system is the inverter since the output depends on the inverter sizing ratio, therefore optimal sizing factor was designed by considering factors that affects inverter sizing such as temperature, irradiance and the location. Large and small systems of 50 kW and 5 kW respectively were considered to determine grid connected inverter sizing factors for different climates in Kenya, Sweden, and India using PVsyst simulation. Two different inverter brands of SMA and ABB with 20 kW and 25 kW rating for large system and 4.6 kW, 4 kW inverters for small system. PVsyst simulation result showed that different locations with different orientation angles, the optimum sizing varies hence affects the annual performance of the system. Photovoltaic system inverters are sized based on the rated power of the installed system and this can be achieved when the inverter size is either almost matching or not. In this case the study presents the optimal sizing factor for grid connected inverter for Mandera in Kenya, Norrköping in Sweden and Kerala in India. The determination was done through the use of designing, assessing and analyzing of the relationship between the sizing factor with performance ratio, operational efficiency and annual hourly energy yield. The unique weather profile in Kerala and in Mandera favors the adoption of solar energy technology in the location. Solar radiation for one year was used as a baseline input and the result reveals that Mandera receives yearly radiation of 2.1 MWh/m² while Kerala and Norrköping receives 2 MWh/m² and 1.1 MWh/m² respectively. Design simulation using PVsyst tool made it possible for the determination of the optimal sizing factor for the grid connected system. Considerations such as the losses and the variations within the specific location was done and a graph showing the relationship between the sizing factor in relation to the operational inverter efficiency as well as energy yield and performance ratio was later on compared to see the behavior of the sizing factor. The study concludes that operational efficiency, performance ratio and energy yield affects the array optimum sizing ratio. For the three locations, inverters (SMA and ABB) shows different variations because optimal sizing ratio depends on the location and irradiation. The results reveal that Mandera has an optimal grid connected inverter sizing of the range from 1.1 to 1.4 while in Kerala it has from 1.2 to 1.4 and Norrköping has the range from 1.1 to 1.3. Optimal sizing of grid connected inverters depends on the energy yield and the location therefore the inverter mismatch voltage and its rating values have to be considered while determining the optimal sizing factor. The 25 kW inverters in all the locations had better efficiency and sizing factor and this proves that sizing the photovoltaic inverter will give better performance and efficiency.