The main objective of this study was to investigate the performance of grid integrated PV systems. A data acquisition (DAQ) system was developed to monitor the performance of an existing grid integrated PV system with battery storage. This system is referred to as a grid assisted PV system. A data logger was used together with the inverters built in data logger to monitor environmental and electrical data on a grid tie PV system which was deployed during this study. To investigate the performance of these grid integrated PV systems PV and BOS device characterization was performed. This was achieved by using current voltage curve tracers and the DAQ system developed. Energy yield estimations were calculated referring to the literature review and a meteorological reference for comparison with measured energy yields from the grid tie PV system.

In order to investigate the influence of parasitic resistances, saturation current and diode ideality factor on the performance of photovoltaic devices, parameter extraction routines employing the standard iteration (SI) method and the particle swarm optimization (PSO) method were developed to extract the series resistance, shunt resistance, saturation current and ideality factor from the I-V characteristics of solar cells and PV modules. The well-known one- and two-diode models were used to describe the behavior of the I-V curve and the parameters of the models were determined by approximation and iteration techniques. The SI and the PSO extraction programmes were used to assess the suitability of the one- and the two-diode solar cell models in describing the I-V characteristics of mono- and multicrystalline silicon solar cells, CISS- and CIGSS-based solar cells. This exercise revealed that the two-diode model provides more information regarding the different processes involved in solar cell operation. Between the two methods developed, the PSO method is faster, yielded fitted curves with lower standard deviation of residuals and, therefore, was the preferred extraction method. The PSO method was then used to extract the device parameters of CISS-based solar cells with the CISS layer selenized under different selenization process conditions and CIGSS-based solar cells with varying i-ZnO layer thickness. For the CISS-based solar cells, the detrimental effect of parasitic resistances on device performance increased when the temperature and duration of the selenization process was increased. For the CIGSS-based devices, photogeneration improved with increasing i-ZnO layer thickness. At high forward bias, bulk recombination and/or tunneling-assisted recombination were the dominant processes affecting the I-V characteristics of the devices. v Lastly, device and performance parameters of mono-, multicrystalline silicon and CIS modules derived from I-V characteristics obtained under dark and illuminated conditions were analyzed considering the effects of temperature on the performance of the devices. Results showed that the effects of parasitic resistances are greater under illumination and, under outdoor conditions, the values further declined due to increasing temperature. The saturation current and ideality factor also increased under outdoor conditions which suggest increased recombination and, coupled with the adverse effects of parasitic resistances, these factors result in lower FF and lower maximum power point. Analysis performed on crystalline silicon and thin film devices utilized in this study revealed that parameter extraction from I-V characteristics of photovoltaic devices and, in particular, the implementation of PSO in solar cell device parameter extraction developed in this work is a useful characterization technique.

The objective of this study is to characterize and analyse defects in solar cell devices. Materials used to fabricate solar cells are not defects free and therefore, there is a need to investigate defects in cells. To investigate this, a topographical technique was developed and employed which uses a non-destructive methodology to analyse solar cells. A system was built which uses a technique based on a laser beam induced current (LBIC). LBIC technique involves focusing light on to a surface of a solar cell device in order to create a photo-generated current that can be measured in the external circuit for analyses. The advantage of this technique is that it allows parameter extraction. Parameters that can be extracted include short-circuit current, carrier lifetime and also the external and internal quantum efficiency of a solar cell. In this thesis, LBIC measurements in the form of picture maps are used to indicate the distribution of the localized beam induced current within solar cells. Areas with low minority carrier lifetime in solar cells are made visible by LBIC mapping. Surface reflection intensity measurements of cells can also be mapped using the LBIC system developed in this study. The system is also capable of mapping photo-generated current of a cell below and above room temperature. This thesis also presents an assessment procedure capable of assessing the device and performance parameters with reference to I-V measurements. The dark and illuminated I-V characteristics of solar cells were investigated. The illuminated I-V characteristics of solar cells were obtained using a defocused laser beam. Dark I-V measurements were performed by applying voltage across the cell in the dark and measuring a current through it. The device parameters which describe the behaviour of I-V characteristic were extracted from the I-V data using Particle Swarm Optimization (PSO) method based on a one-and two-diode solar cell models. Solar cells of different technologies were analysed, namely, single-crystalline (c-Si) and multicrystalline (mc-Si) silicon, Edge-defined Film-fed Growth Si (EFG-Si) and Cu(In,Ga)(Se,S)2 (CIGSS) thin film based cells. The LBIC results illustrated the effect of surface reflection features and material defects in the solar cell investigated. IQE at a wavelength of 660 nm were measured on these cells and the results in general emphasised the importance of correcting optical losses, i.e. reflection loss, when characterizing different types of defects. The agreement between the IQE measurements and I-V characteristics of a cell showed that the differences in crystal grains influence the performance of a mc-Si cell. The temperature-dependence of I-V characteristics of a CIGSS solar cell was investigated. The results showed that, for this material, the photo response is reduced at elevated temperatures. In addition to LBIC using a laser beam, solar spectral radiation was employed to obtained device performance parameters. The results emphasised the effect of grain boundaries as a recombination centres for photo-generated hole-pairs. Lastly, mesa diode characterizations of solar cells were investigated. Mesa diodes are achieved by etching down a solar cell so that the plateau regions are formed. Mesa diodes expose the p-n junction, and therefore mesa diode analysis provides a better way of determining and revealing the fundamental current conduction mechanism at the junction. Mesa diodes avoid possible edge effects. This study showed that mesa diodes can be used to characterize spatial non-uniformities in solar cells. The results obtained in this study indicate that LBIC is a useful tool for defect characterization in solar cells. Also LBIC complements other characterization techniques such as I-V characterization.

In order for photovoltaic systems to gain acceptance as viable energy sources, they must have a sufficient life span and must be optimized to provide maximum power. In order to achieve these goals, several maximum power point tracking (MPPT) algorithms have been developed to ensure the photovoltaic (PV) system operates at maximum efficiency despite changes in temperature, shading, and age of the solar cells. However, the connection of multiple PV systems in parallel cannot be achieved using a single MPPT control due to the characteristic differences in each solar array's orientation, illumination, temperature, composition, and age. The mismatch of the individual PV systems can limit the power output and reliability of the systems, as well as reduce the expected lifetime. Multi-channel PV systems require MPPT controls for each channel, as well as communication between channels so that power extraction is shared among channels. Therefore, an algorithm is presented which includes MPPT and promotes equal power sharing between the sources and the load in order to make multichannel PV systems more robust, reliable, and efficient. The algorithm is implemented using a digital signal processor (DSP), and the validity of the algorithm will be proven using modeling techniques and through the construction of a prototype two-channel PV system. Once the viability of the two channel system has been proven, the expansion of the system to an n-channel system will be discussed.

At starting, electrical motors require large power and current. This may not be a problem in a large electrical system but it may be very severe for a limited power source like a solar array. If a direct approach is taken the array rating must be 5-6 times the motor rating in order to start the motor and its high inertia high friction load. Batteries have been used to store energy and supply that energy for starting. Batteries need maintenance and their low efficiency is a problem too. In this study a new type of controller has been suggested and developed for the use with D.C. motors. Computer simulation showed promising results. The controller uses the array power, which is equal to the rated power of the motor, for starting and for running condition. Experimental results showed that the theoretical results are applicable.

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 ...

A thesis submitted to the Faculty of Science, University of the Witwatersrand in partial fulfilment of the requirement for the degree Doctor of Philosophy (PhD) in Chemistry. Johannesburg, June 2017. / Due to a high global demand for energy, research groups have been focusing a lot of energy into finding alternative and cleaner energy sources. Solar power has all the attributes to be the energy of the future. Solar power is abundantly available and is a cleaner form of energy as compared to the market-leading fossil fuels. In this thesis, we consider new materials that can be used in hybrid solar cells. These new materials combine the properties of inorganic nanomaterials and polymers. The nanomaterials possess unique properties that can be exploited and the polymers allow for the thin films to potentially be light weight and flexible. Copper selenide was synthesized and characterized to produce particles with different sizes as a function of time. These size variations are shown to emit a spectrum of different colours. In addition the particles synthesized at various temperatures are reported. Temperature had an effect on the size of the particles with bigger sizes obtained as the temperature was increased. Also shown in the results is that Cu2Se nanocrystals were quite resistant to changes with the sizes marginally increasing with increasing time and temperature. A hybrid material using a conductive polymer polyvinylcarbazole (PVK) and copper selenide was synthesized and used as the active layer via a spin coating technique to fabricate a solar cell. Varying amounts (10% - 50%) of Cu2Se nanocrystals were used in the polymer nanocomposites. The 10% weight loading resulted in the highest efficiency of 0.74% whilst successive addition of the nanocrystals affected the polymeric structure of PVK thus resulting in solar cells with even lower efficiencies. Niobium selenide was synthesized via the colloidal method using TOP/HDA combination for the first time. The effect of time on the particles synthesized using a 1:1 mole ratio of Nb:Se was negligible with particles showing similar properties. The XRD of the samples revealed that they were amorphous thus making it difficult to conclusively say that niobium selenide was synthesized successfully. The samples were then annealed however only small improvements were observed. The concentration of the selenium was then increased in order to form the more common NbSe2 and NbSe3. The XRD showed the formation of NbSe2 and NbSe3 for 1:2 and 1:3 Nb:Se ratios respectively. In addition, the particles resembled 2D nanostructures readily observed in layered materials such as NbSe2 and NbSe3. However, some impurities in the form of oxides were still observed. Hybrid solar cells prepared from the amorphous 1:1, 1:2 and 1:3 Nb:Se samples were fabricated. The NbSe3 composite had the best performing solar cell with the power conversion efficiency of 3.234% with the amorphous particles generating no current. / LG2017

A dissertation submitted to the Faculty of Science, School of Physics, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2016. / Organic Photovoltaic (OPV) is an environmental friendly technology that promises e cient and e ective harvesting of solar energy. The organic polymers used in the fabrication of OPVs are characterized by low weight, tunable electrical and optical properties. However, the low photo-conversion e ciency (PCE) and instability in air remains a major drawback that limits their commercialization. The project seeks to increase the PCE of a cheap photovoltaic device using plasmonic e ects and rare earth doped waveguides to modify the optical response in the active layer. Incorporating regularly shaped silver (Ag) nanoparticles (NPs) in OPVs through the surface plasmon resonance will enhance tunable absorption and scattering of light. These NPs are prepared by reducing AgNO3 with N,N-dimethylformamide (DMF) and using 2,2- Poly(vinylpyrrolidone) (PVP) as a stabiliser at di erent reaction times. The Ag NPs have shown di erent shapes such as spherical and prism shapes of 14, 15 and 16 nm visualised by TEM. / MT2017

University of Macau / Faculty of Science and Technology. / Department of Electromechanical Engineering

Since the 1980s, approximately 10 MWp photovoltaic (PV) power has been installed in off-grid areas in Indonesia for powering lighting, water pumping, communications, health clinics, etc. However, PV energy systems (PVES) have yet to prove their sustainability and remain inaccessible to many remote Indonesian communities. The objective of this interdisciplinary thesis is to draw on social and engineering perspectives to address sustainability issues related to off-grid PVES delivery in Indonesia. By employing the Brundtland definition of sustainability, off-grid PVES delivery is analysed with respect to its institutional, financial, technical, social and ecological sustainability. In parallel, the thesis also investigates PVES Accessibility, Availability and Acceptability (3A), referring to the three energy goals proposed by the World Energy Council. The concepts of Sustainable Development, Social Capital, and Diffusion of Innovation are employed to examine the potential for off-grid PVES to contribute to improving the sustainability of remote Indonesian communities. The I3A (Implementation, 3A) Sustainable PVES Delivery framework is proposed to investigate PVES sustainability and the extent to which local communities can continue to socially innovate to meet their evolving needs beyond initial project completion. Sound project management (PM) is essential as off-grid PVES projects can only access limited resources (time, funds, and scope) and project failure can undermine a community???s capacity to innovate. The research methodologies include literature research, qualitative field research in villages where PVES has been installed and interviews with a wide range of PVES stakeholders in Indonesia. The I3A framework is tested against three off-grid PVES case studies from Lampung, West Java and NTT Provinces and is also proposed as a design tool. A key conclusion is that, to be sustainable and equitable, off-grid PVES projects should be implemented in an institutional framework that provides sound project management and addresses PVES accessibility (financial, institutional and technological), availability (technical quality and continuity) and acceptability (social and ecological). The overall objectives are to acknowledge the interests of all stakeholders, maximise equity, assure PVES continuity, and institutionalize PVES by utilizing and enhancing preexisting community resources to leave the community with the capacity to socially innovate. While this might be regarded as idealistic, enhanced local autonomy and capability will be essential in the context of the energy security and climate change challenges that humanity now faces.