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Two basic types of photovoltaic (PV) array simulator have been designed and tested. The first involves the use of a pilot panel and variable light source. It is implemented with analogue circuits. A stability analysis based on Popov's method is presented for this simulator with resistance-inductance (R-L) loads. In the second, characteristic array curves are stored in the memory of a microprocessor-based simulator. The design of both simulators is based on the transfer function method. By using the computing facility available, a stability study for the Type I simulator and some dynamic simulations are carried out. Both simulators are capable of driving a special load, namely, an experimental solar pumping system. The experimental results for both types of' simulator are satisfactory in terms of steady state precision and dynamic behaviour when used with this load. Compared with previously-reported PV array simulator designs [6,7,8,9,18], the two simulators described here have the following distinctive features: 1. A new method of sample curve generation for the Type II simulator results in relatively short sampling period and small memory size. 2. The sample curves of the type II simulator are based directly on the real PV array to be simulated. They are more accurate than the sample curves in references [6,7,9]. 3. Different loads (R, R-L and an experimental solar pumping system) have been considered in the design and have been tested in laboratory. 4. A stability analysis and some dynamic simulations are presented for the type I simulator. An analysis of this type has not been reported in previous studies [6,7,8,9,18]. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Solar energy has come to the forefront as a scalable and largely underutilized renewable energy resource. The current cost of solar electricity, namely from photovoltaics, along with other logistics factors, has prevented the widespread adaptation of the technology. A key determinant of efficiency and cost for a solar cell is the current collector grid. This work presents the Collimated Aerosol Beam Direct Write (CAB-DW) system as a non-contact printing method that can achieve current collector grid finger widths of less than 10 μm which are amenable to decreasing both resistive and optical losses. The ability to produce high aspect ratio grid fingers, and deposit optimized grid structures on high efficiency SHJ solar cells using silver nanoparticle inks is also demonstrated. A decrease in shadowing and via profile modification of the grid fingers is presented, along with a study of aging and degradation of electrical properties within silver nanoparticle inks.

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

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published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

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