Engineering Commons^™

Three-Dimensional Nanotube Arrays For Solar Energy Harvesting And Production Of Solar Fuels, Wipula P. R. Liyanage

Doctoral Dissertations

"Over the past decade extensive research has been carried out on photovoltaic semiconductors to provide a solution towards a renewable energy future. Fabricating high-efficiency photovoltaic devices largely rely on nanostructuring the photoabsorber layers due to the ability of improving photoabsorption, photocurrent generation and transport in nanometer scale. Vertically aligned, highly uniform nanorods and nanowire arrays for solar energy conversion have been explored as potential candidates for solar energy conversion and solar-fuel generation owing to their enhanced photoconversion efficiencies.

However, controlled fabrication of nanorod and especially nanotube arrays with uniform size and shape and a pre-determined distribution density is still a …

Advanced Topologies Of High-Voltage-Gain Dc-Dc Boost Converters For Renewable Energy Applications, Ahmad Alzahrani

Doctoral Dissertations

This dissertation proposes several advanced power electronic converters that are suitable for integrating low-voltage dc input sources, such as photovoltaic (PV) solar panels, to a high voltage dc bus in a 200 - 960 V dc distribution system. The proposed converters operate in the continuous conduction mode (CCM) and offer desirable features such as low-voltage stresses on components, continuous input currents, and the ability to integrate several independent dc input sources. First, a family of scalable interleaved boost converters with voltage multiplier cells (VMC) is introduced. Several possible combinations of Dickson and Cockcroft-Walton VMCs are demonstrated and compared in terms …

Fluorochlorozirconate Glass Ceramics For Photovoltaic And Computed Radiography Applications, Russell Lee Leonard

Doctoral Dissertations

Fluorochlorozirconate (FCZ) glass ceramics are versatile materials whose optical properties may be tuned through compositional or processing changes. For this work, FCZ glasses were synthesized, and then subsequently heat treated to create optically-active glass ceramics. The glasses and glass ceramics were characterized using a number of methods including differential scanning calorimetry, phosphorimetry, x-ray diffraction, and spectrophotometry. Samples were evaluated for applications in photovoltaics and computed radiography–especially those pertaining to intraoral dental radiography and portal imaging.

The ability of FCZ glass ceramics containing hexagonal barium chloride nanocrystals doped with the rare earth elements, holmium and europium, to downshift ultraviolet light to …

Cascaded Inverters For Grid-Connected Photovoltaic Systems, Bailu Xiao

Doctoral Dissertations

With the extraordinary market growth in grid-connected PV systems, there is increasing interests in grid-connected PV inverters. Focus has been placed on cheap, high-efficiency, and innovative inverter solutions, leading to a high diversity within the inverters and new system configurations. This dissertation chooses cascaded multilevel inverter topologies for grid-connected PV systems to reduce the cost and improve the efficiency.

First, a single-phase cascaded H-bridge multilevel PV inverter is discussed. To maximize the solar energy extraction of each PV string, an individual maximum power point tracking (MPPT) control scheme is applied, which allows independent control of each dc-link voltage. A generalized …