Renewable power generation from the controlled mixing of sea and fresh water is relatively unexplored when compared to the development for solar, wind, and other sustainable power alternatives. When global river discharge was taken into account, an estimated 2.6 TW of obtainable energy exists in untapped salinity gradients. Reverse electrodialysis is one proposed power-generating mechanism for harnessing energy from brackish environments and relies on the transport of aqueous salt ions through an apparatus of ion-exchange membranes. In this thesis, operational parameters, including flow direction, salinity composition, and membrane selectivity, are investigated. For optimal performance, I have employed counter-current flow mode with monovalent ion selective membranes and pure 0.5 M NaCl saline solution. The results show that a maximum open circuit voltage (OCV) level of 2.01 V is obtained with an active membrane area of 0.0756 m². The presence of multivalent ions in the feed solutions hinders OCV levels, but the effects are reduced with monovalent-selective membranes. Preliminary results are insightful; in order to increase the commercially viability of this technology, future work is needed to enhance the performance properties of the ion exchange membranes.

Crystalline silicon solar cells translate energy from the sun into electrical energy via the photoelectric effect. This technology has the potential to simultaneously reduce carbon emissions and our dependence on fossil fuels. The cost of photovoltaic energy, however, is still higher than the cost of electricity off of the grid which hampers this technologies adoption. Raising solar cell efficiency without significantly raising the cost is crucial to lowering the cost of photovoltaic produced energy. One technology which holds promise to increase solar cell efficiency is a selective emitter solar cell. In this work the benefit of selective emitter solar cells is quantified through numerical modeling. Further, the use of ultraviolet laser to create a laser doped selective emitter solar cell is explored. Through optimization of the laser doping process to minimize laser induced defects it is shown that this process can increase solar cell efficiency to over 19.1%. Additionally, 2D and 3D numerical modeling are performed to determine the limitations screen printed interdigitated back contact solar cells and the practical efficiency limit for crystalline Si solar cells.

Access to modern energy is central to addressing important global development challenges including poverty, inequality, climate change, food security, health and education. The understanding of the concept of energy poverty is critical when making any attempts to alleviate it. Lack of access to sustainable energy is also a major factor preventing social and economic development, both of which are linked to sustainable poverty reduction. However, worldwide access to energy has shown very slow progress because of the costs associated with electric grid extensions and decentralized systems by which power is offered. This study investigates the viability of implementing solar energy in poor communities in Inanda, which is located in Durban, South Africa. Inanda is known to be an area with high unemployment and high poverty levels. Most important to this study are high energy poverty levels in the area. It was found that these communities prioritised energy for cooking, lighting and heating. The results of this study also indicate that in most households, multiple sources of unsustainable energy sources were being used. These included electricity, fuelwood, gas, paraffin and candles. Illegal electrical connections are a growing problem in this community, and other traditional sources were found to have numerous effects on human and environmental health. Upon investigation of the potential for renewable energy implementation in these communities, it found that there was a high willingness to use it, specifically solar energy; however, more education is needed regarding solar energy and related benefits. It was also indicated that the provision of sustainable energy will allow more time for income-generating activities in the community. The biggest challenge with regard to provision of solar energy was cost. These communities cannot afford to pay high start-up and maintenance costs for the technology. It is for this reason that efforts should be made to subsidize these costs and integrate this plan into policy-making. This will not only provide poor communities with sustainable energy, but also help advance the renewable energy industry in South Africa. / M.A. University of KwaZulu-Natal, Durban 2013.

With the increase of world population and industrial growth of developing countries, demand for energy, in particular electric power, has gone up at an unprecedented rate over the last decades. To meet the demand, electric power generation by use of fossil fuel has increased enormously thereby producing increased quantity of greenhouse gases. This contributes more and more to atmospheric pollution, which climate scientists believe can adversly affect the global climate, as well as health and the welfare of the world population. In view of these issues, there is global awareness to look for alternate sources of energy such as natural gas, hydropower, wind, solar, geothermal and biomass. It is recognized that this requires replacement of existing infrastructure with new systems, which cannot be achieved overnight. Optimal control theory has been widely used in diverse areas of physical sciences, medicine, engineering and economics. The main motivation of this thesis is to use this theory to find the optimum strategy for integration of all currently available renewable energy sources with the existing electric power generating systems. The ultimate goal is to eliminate fossil fuels. Eight main energy sources namely, Coal, Petroleum, Natural Gas, Conventional Hydro, Wind, Solar, Geothermal and Biomass are considered in a dynamic model. The state of the dynamic model represents the level of energy generation from each of the sources. Different objective functions are proposed in this thesis. These range from meeting the desired target level of power generation from each of the available sources at the end of a given plan period, to reducing the implementation and investment costs; from minimizing the production from polluted energy sources to meeting the electricity demand during a whole plan period. Official released data from the U.S. Energy Information Administration have been used as a case study. Based on real life data and the mathematics of optimal control theory, we present an optimal policy for integration of renewable energy sources to the national power grid.

A new concept, extracting energy from sea waves by parametric pendulor, has been explored in this project. It is based on the conversion of vertical oscillations to rotational motion by means of a parametrically-excited pendulor, i.e. a pendulum operating in rotational mode. The main advantage of this concept lies in a direct conversion from vertical oscillations to rotations of the pendulum pivot. This thesis, firstly, reviewed a number of well established linear and nonlinear theories of sea waves and Airy’s sea wave model has been used in the modelling of the sea waves and a parametric pendulum excited by sea waves. The third or fifth order Stokes’s models can be potentially implemented in the future studies. The equation of motion obtained for a parametric pendulum excited by sea waves has the same form as for a simple parametrically-excited pendulum. Then, to deepen the fundamental understanding, an extensive theoretical analysis has been conducted on a parametrically-excited pendulum by using both numerical and analytical methods. The numerical investigations focused on the bifurcation scenarios and resonance structures, particularly, for the rotational motions. Analytical analysis of the system has been performed by applying the perturbation techniques. The approximate solutions, resonance boundary and existing boundary of rotations have been obtained with a good correspondence to numerical results. The experimental study has been carried out by exploring oscillations, rotations and chaotic motions of the pendulum.

Designing horizontal-axis wind turbine (HAWT) blades to achieve satisfactory levels of performance starts with knowledge of the aerodynamic forces acting on the blades. In this thesis, HAWT blade design is studied from the aspect of aerodynamic view and the basic principles of the aerodynamic behaviors of HAWTs are investigated. Blade-element momentum theory (BEM) known as also strip theory, which is the current mainstay of aerodynamic design and analysis of HAWT blades, is used for HAWT blade design in this thesis. Firstly, blade design procedure for an optimum rotor according to BEM theory is performed. Then designed blade shape is modified such that modified blade will be lightly loaded regarding the highly loaded of the designed blade and power prediction of modified blade is analyzed. When the designed blade shape is modified, it is seen that the power extracted from the wind is reduced about 10% and the length of modified blade is increased about 5% for the same required power. BLADESIGN which is a user-interface computer program for HAWT blade design is written. It gives blade geometry parameters (chord-length and twist distributions) and design conditions (design tip-speed ratio, design power coefficient and rotor diameter) for the following inputs / power required from a turbine, number of blades, design wind velocity and blade profile type (airfoil type). The program can be used by anyone who may not be intimately concerned with the concepts of blade design procedure and the results taken from the program can be used for further studies.

The present project has made a comprehensive assessment of the effect of Nb doping on various charge-transfer related properties of TiO2. Of particular focus, the electrical properties of Nb-doped TiO2 (0.65 at %) have been investigated using the simultaneous measurement of electrical conductivity and thermoelectric power. This investigation was undertaken at elevated temperatures (1073 K -- 1298 K) in equilibrium with a gas phase of controlled oxygen activity (10-10 Pa < p(O2) < 75 kPa). In addition, the effect of segregation on the surface versus bulk composition of Nb-doped TiO2 was also investigated at a function of temperature and oxygen activity. Specifically, the following determinations were undertaken: The effect of oxygen activity, p(O2) and temperature on both electrical conductivity and thermoelectric power The effect of Nb on the defect disorder and related electrical properties of TiO2 The determination of equilibration kinetics and the associated chemical diffusion data for Nb-doped TiO2 The determination of Nb bulk diffusion in TiO2 The effect of p(O2), temperature and dopant content on Nb segregation and the related surface composition of Nb-doped TiO2 The obtained electrical properties enable the determination of a defect disorder model for Nb-doped TiO2, which may be considered within the following p(O2) regimes: Strongly Reduced Regime. In this regime, the predominant ionic defect was anticipated to be oxygen vacancies compensated electronically by electrons. While the transition to this regime (from higher p(O2)) was clearly observed, the predominant defect disorder existing beyond this transition was not confirmed due to an inability to obtain sufficiently low oxygen activity. Metallic-type conductivity behaviour was observed within this transition region. Reduced Regime I. In this regime, the predominate defect disorder defined by the electronic compensation of incorporated Nb ions by electrons was clearly observed. Reduced Regime II. In this regime, the predominate defect disorder defined by the ionic compensation of incorporated Nb ions by quadruply-charged titanium vacancies, was clearly observed. The present project included the determination of diffusion data which included: Temperature dependence of 93Nb tracer diffusion in single crystal TiO2 over the temperature range 1073 K -- 1573 K Chemical diffusion coefficient over the temperature range 1073 K -- 1298 K and oxygen activity range, 10-10 Pa < p(O2) < 75 kPa These pioneering studies are significant as they enable the prediction of the processing conditions required to reliably 1) incorporate Nb into the TiO2 lattice, and 2) achieve equilibrium with the gas phase. Finally, the present project included investigations on the effect of Nb segregation on the surface composition of Nb-doped TiO2, with the following outcomes: Due to segregation, the surface can be significantly enriched in Nb compared to the bulk The extent of enrichment increases as the bulk Nb content or the oxygen activity is decreased Following enrichment, the surface Nb concentration could be sufficiently high to assume a unique surface phase The outcomes of the present project are significant as they can enable the processing of TiO2 with enhanced charge transport and controlled surface properties.

Thesis (M.E. (Elec.) (Hons.)) -- University of Western Sydney, 2002. / "Submitted for the Master degree of Electrical Engineering (Honours)" Includes bibliographical references (leaves 131-136).

Univ., Diss--Bochum, 1999.

Thesis (M. S.)--Building Construction, Georgia Institute of Technology, 2008. / Committee Chair: Dr. Linda Thomas-Mobley; Committee Member: Dr. Del Kiernan-Lewis; Committee Member: Professor Kathy Roper.