Concentrator solar cells operate under the conditions of non-uniform illumination and varying spectral content of incident sunlight. To predict the performance of such cells, an analytical model must account for varying carrier photogeneration rates within the cell. Further, the back surface junction fabricated to reduce recombination at the back contact must be included in the analysis.Most models of n+-p-p+ cells assume uniform generation rates within individual layers. In this study, a one-dimensional n+-p-p+ concentrator solar cell is modeled for all levels of illumination of incident sunlight. The photocarrier generation rate is considered as non-uniform in each layer of the cell. An absorption model is incorporated to permit the application for various spectral mixes of incident sunlight. The model also includes the effects of finite surface recombination velocities at the surfaces. Carrier transport equations for the three layers of the cell are developed and solved for the excess carrier concentrations under the assumptions of the model. Junction current density-voltage relationships for the two junctions of the cell are derived. The use of the current density equations in the evaluation of cell performance is discussed. / Department of Physics and Astronomy

A study has been made of a variety of factors influencing the efficiency and operational stability of front-wall CdS-Cu2S solar cells. In the course of this work -1 cm2 cells were fabricated with conversion efficiency of up to 8% without attempting to reduce reflection losses.The CdS films were produced by vacuum evaporation and the electrical and structural characteristics of these films were studied as a function of the rate and temperature of the deposition. Previously there had been some controversy concerning the nature of the CdS source material required for fabricating high performance CdS-based solar cells, but this work has shown that a variety of CdS sources can be employed successfully provided that the film deposition parameters are suitably chosen.A conventional chemical exchange technique was employed to convert the CdS film surface to Cu2SI with the thickness and stoichiometry of the resultant Cu2S layer being examined by means of electrochemical analysis.Changes in the electrical properties of the CdS-Cu2S cells due to post- fabrication anealing under a variety of different conditions were studied and correlated with structural changes monitored by means of Auger electron spectroscopy with the aid of argon ion etching. Depth profiles of the constituent element concentrations indicate that, for samples annealed in air, a deep penetration of copper into the CdS layer occurs together with a significant out-diffusion of cadmium from the CdS after only a few minutes at 1000C. In contrast, the copper penetration which results from vacuum or hydrogen annealing treatment is substantially less and no significant out-diffusion of cadmium is observed for annealing temperatures up to 4000C. Two different diffusion processes, one in the grain boundaries and one in the mid-grain regions, have been identified and their relative importance has been studied for annealing cycles performed under the same three different ambient atmospheres (air, vacuum or hydrogen). The normally rapid and undesirable grain boundary diffusion of copper was found to be significantly inhibited by the use of flowing hydrogen during annealing. A further technologically important observation concerns the effect of the deposition of a film of copper over the copper sulphide layer of a cell and subsequent annealing of it in air. The improved electrical stability which this treatment yields has been shown to be directly associated with reduced interdiffusion at the CdS-Cu2S interface. This interfacial diffusion has also been shown to be influenced by the CdS stoichiometry in the vicinity of the junction.Finally, a brief investigation was made into the use of the ion implantation technique as a means of doping the upper layer of the OdS film with copper without annealing the completed cell. The results have demonstrated the feasibility of this technique, with the best results being obtained using a copper ion fluence of 5.1014 ions cm-2 at 50 keV ion energy.

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Photovoltaic (solar electric) technology has shown significant potential as a source of practical and sustainable energy; this study focuses on increasing the performance of photovoltaic systems through the use of improved control and power interfaces. The main objective is to find an effective control algorithm and topology that are optimally suited to extracting the maximum power possible from photovoltaic modules. The thesis consists of the following primary subjects: photovoltaic modelling, the topological study of photovoltaic interfaces, the regulation of photovoltaic voltage, and maximum power tracking. In photovoltaic power systems both photovoltaic modules and switching mode converters present non-linear and time-variant characteristics, resulting in a difficult control problem. This study applies in-depth modelling and analysis to quantify these inherent characteristics,s pecifically using successive linearization to create a simplified linear problem. Additionally, Youla Parameterisation is employed to design a stable control system for regulating the photovoltaic voltage. Finally, the thesis focuses on two critical aspects to improve the performance of maximum power point tracking. One improvement is to accurately locate the position of the maximum power point by using centred differentiation. The second is to reduce the oscillation around the steady-state maximum power point by controlling active perturbations. Adopting the method of steepest descent for maximum power point tracking, which delivers faster dynamic response and a smoother steady-state than the hill climbing method, enables these improvements. Comprehensive experimental evaluations have successfully illustrated the effectiveness of the proposed algorithms. Experimental evaluations show that the proposed control algorithm harvests about 1% more energy than the traditional method under the same evaluation platform and weather conditions without increasing the complexity of the hardware.

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.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Also available in print.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: photovoltaic; solar satellite; optimize; dc-dc. Includes bibliographical references (leaves 51).

Thesis (M.E.E.)--University of Delaware, 2008. / Principal faculty advisor: Allen Barnett, Dept. of Electrical & Computer Engineering. Includes bibliographical references.

Dissertation (Ph.D.)--University of Toledo, 2008. / Typescript. "Submitted as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Physics." Bibliography: leaves 97-100.