The expansion of worldwide energy demands, coupled with the fragility of electricity distribution grids, has sparked interest in building-scale distributed solar energy production. To further research into the barriers and challenges of residential grid-intertied solar photovoltaic electrical production, the U.S. Department of Energy founded the U.S. DOE Solar Decathlon. Through the 2009 U.S. DOE Solar Decathlon, the challenges of solar PV design and system performance were explored for the affordable-housing market of Houston, TX. Energy demand and production modeling techniques were used to inform the design of the prototype, the Zero-Energy Row House (ZEROW), and techniques for cost reduction and simplification of power generation systems were employed in the pursuit of archiving grid-parity solar electrical production as the household level. Preliminary ZEROW system design, performance, and challenges are discussed, as well as directions for future research.

<p> This thesis presents a computational analysis of the performance of the model of a hydropower barge, consisting of 3 pairs of paddle wheels, in generating power from the flow of a river. The barge dimensions used in this research are one-thirtieth scale of the actual barge dimensions.</p><p> These new dimensions were used in the simulations to predict the power that can be generated, having carried out similitude between the scaled model and its full scale size. The dimensionless parameters employed in achieving similitude are Strouhal number, power coefficient, and pressure coefficient. The efficiency of the paddle wheel conforms to that obtained from most power turbines. The power generated was improved by the addition of bottom fin under the paddle wheel.</p><p> Computational Fluid Dynamics using ANSYS Fluent software was employed to simulate and generate the results. The simulation results generated will be compared to an experimental model that will be performed in the future based on the new scaled dimensions. This will help validate the viability of the paddle wheel, as proposed here, in the generation of power prior to designing the full scale sized barge.</p>

<p> The development of cost-effective materials for effective utilization of solar energy is a major challenge for solving the energy problems that face the world. This thesis work relates to the development of mesoporous materials for solar energy applications in the areas of photocatalytic water splitting and the generation of electricity. Mesoporous materials were employed throughout the studies because of their favorable physico-chemical properties such as high surface areas and large porosities. The first project was related to the use of a cubic periodic mesoporous material, MCM-48. The studies showed that chromium loading directly affected the phase of mesoporous silica formed. Furthermore, within the cubic MCM-48 structure, the loading of polychromate species determined the concentration of solar hydrogen produced. In an effort to determine the potential of mesoporous materials, titanium dioxide was prepared using the Evaporation-Induced Self-Assembly (EISA) synthetic method. The aging period directly determined the amount of various phases of titanium dioxide. This method was extended for the preparation of cobalt doped titanium dioxide for solar simulated hydrogen evolution. In another study, metal doped systems were synthesized using the EISA procedure and rhodamine B (RhB) dye sensitized and metal doped titania mesoporous materials were evaluated for visible light hydrogen evolution. The final study employed various mesoporous titanium dioxide materials for N719 dye sensitized solar cell (DSSC) materials for photovoltaic applications. The materials were extensively characterized using powder X-ray diffraction (XRD), nitrogen physisorption, diffuse reflectance spectroscopy (DRS), UV-Vis spectroscopy, Fourier-Transform-Infrared Spectroscopy (FT-IR), Raman spectroscopy, chemisorption, photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). In addition, photoelectrochemical measurements were completed using current-voltage (I-V) curves, external quantum efficiency (EQE) curves, electrochemical impedance spectroscopy (EIS), and transient spectroscopy. The thesis work presented provides a better understanding of the role of mesoporous materials for solar hydrogen and solar electricity production.</p>

<p> A CAT C6.6 turbocharged diesel engine was operated in dual-fuel diesel-hydrogen mode. Hydrogen was inducted into the intake and replaced a portion of the diesel fuel. Hydrogen was added across multiple engine speeds and loads until reaching the knock limit, identified by a threshold on the rate of in-cylinder pressure rise. In-cylinder pressure and emissions data were recorded and compared to diesel-only operation. Up to 74% H₂ substitution for diesel fuel was achieved. Hydrogen addition increased thermal efficiency up to 32.4%, increased peak in-cylinder pressure up to 40.0%, increased the maximum rate of pressure rise up to 281%, advanced injection timing up to 13.6&deg;, increased NO_x emissions up to 224%, and reduced CO₂ emissions up to 47.6%. CO and HC emissions were not significantly affected during dual-fuel operation. At 25% load an operating condition was observed with low NO_x and nearly 0 CO₂ emissions, which however exhibited unstable combustion.</p>

<p> This research develops a comprehensive methodology and model for accurate prediction of power losses caused by nonuniform electrical characteristics and operating conditions in grid-tied photovoltaic systems, as well as the potential for increased energy capture in systems which employ sub-array power optimizers (microconverters or microinverters). Investigation of these topics provides a framework for more accurate loss modeling and determination of power optimizers' value in a variety of scenarios, enabling future PV research and maximizing the value of PV systems in the built environment. </p><p> A custom multitracer, which records simultaneous module-level I-V curves, is designed and built to collect data on 27 PV installations in the Southwestern U.S. The resulting measured dataset, including over 500 modules of crystalline silicon and thin film technologies, indicates that commonly-used, single diode PV generator modeling methodologies often incorrectly predict PV performance at low and medium light levels. A new modeling methodology and parameters are proposed, demonstrating an improved way to incorporate low light data to increase prediction accuracy for crystalline silicon and thin film arrays. </p><p> A unique, detailed annual simulation environment for PV system modeling is developed, allowing user-input electrical characteristics and operating conditions at the PV cell level. It is designed specifically to model electrical mismatch and partial array shading, and use of power optimizers to mitigate related energy losses. The resulting simulations, combined with the module-level I-V curve dataset, are used to predict annual mismatch losses caused by module-to-module performance variation in each monitored array. The losses, representing energy that may be directly recovered using power optimizers, are moderately low for most of the tested arrays. </p><p> Annual simulations of realistic shading scenarios and PV array configurations show percent annual energy losses that are 2&ndash;3 times the annual percent incident light lost in partially shaded arrays. Sub-module or even module level simulations predict nearly the same shading losses as cell level simulations, demonstrating opportunities for model simplification. Arrays with power optimizers can recover 30&ndash;45% of the energy loss. In the example scenarios, power optimizers are most advantageous at the module or cell levels, adding little benefit at the string or bypass diode sub-module levels.</p>

<p> During the last several decades engineers and scientists put significant effort into developing reliable and efficient wind turbines. As a wind power production demands grow, the wind energy research and development need to be enhanced with high-precision methods and tools. These include time-dependent, full-scale, complex-geometry advanced computational simulations at large-scale. Those, computational analysis of wind turbines, including fluid-structure interaction simulations (FSI) at full scale is important for accurate and reliable modeling, as well as blade failure prediction and design optimization. </p><p> In current dissertation the FSI framework is applied to most challenging class of problems, such as large scale horizontal axis wind turbines and vertical axis wind turbines. The governing equations for aerodynamics and structural mechanics together with coupled formulation are explained in details. The simulations are performed for different wind turbine designs, operational conditions and validated against field-test and wind tunnel experimental data.</p>

<p> The <i>Cool Robot</i> is a solar powered autonomous robot designed to support summertime science campaigns in the Polar Regions. While the overall design was proven in a previous deployment to Summit Greenland, it lacked the robustness for longer campaigns, and the ergonomics of accessing the interior of the robot were arduous and time consuming. The objectives of this thesis were to 1) redesign the solar panel system for improved performance in wind and rough terrain and for easier assembly and access to inside of the robot chassis, 2) update the power system controls and electronics for reliable and robust operation, 3) update all electrical systems using common, off-the-shelf components, 4) establish a common code base and communication protocol used by other similarly designed robots, 5) provide permanent data logging capability to evaluate mobility and the power system performance, and 6) develop and implement a sensor-based framework for detecting and avoiding dangerous levels of tilt which could result in roll-over. All of these objectives aim to increase the performance reliability of the <i>Cool Robot</i>. The data logging capability allows for collecting data to evaluate performance of the new power system. The reliability of the <i>Cool Robot</i> will be tested during a summer mission to Summit Greenland.</p>

abstract: Photovoltaic (PV) modules appear to have three classifications of failure: Infant mortality, normal-life failure, and end-of-life failure. Little is known of the end-of-life failures experienced by PV modules due to their inherent longevity. Accelerated Life Testing (ALT) has been at the crux of this lifespan prediction; however, without naturally failing modules an accurate acceleration factor cannot be determined for use in ALT. By observing modules that have been aged in the field, a comparison can be made with modules undergoing accelerated testing. In this study an investigation on about 1900 aged (10-17 years) grid-tied PV modules installed in the desert climatic condition of Arizona was undertaken. The investigation was comprised of a check sheet that documented any visual defects and their severity, infrared (IR) scanning, and current-voltage (I-V) curve measurements. After data was collected on modules, an analysis was performed to classify the failure modes and to determine the annual performance degradation rates. / Dissertation/Thesis / M.S.Tech Electrical Engineering 2010

abstract: Building applied photovoltaics (BAPV) is a major application sector for photovoltaics (PV). Due to the negative temperature coefficient of power output, the performance of a PV module decreases as the temperature of the module increases. In hot climatic conditions, such as the summer in Arizona, the operating temperature of a BAPV module can reach as high as 90°C. Considering a typical 0.5%/°C power drop for crystalline silicon (c-Si) modules, a performance decrease of approximately 30% would be expected during peak summer temperatures due to the difference between rated temperature (25°C) and operating temperature (~90°C) of the modules. Also, in a worst-case scenario, such as partial shading of the PV cells of air gap-free BAPV modules, some of the components could attain temperatures that would be high enough to compromise the safety and functionality requirements of the module and its components. Based on the temperature and weather data collected over a year in Arizona, a mathematical thermal model has been developed and presented in this paper to predict module temperature for five different air gaps (0", 1", 2", 3", and 4"). For comparison, modules with a thermally-insulated (R30) back were evaluated to determine the worst-case scenario. This thesis also provides key technical details related to the specially-built, simulated rooftop structure; the mounting configuration of the PV modules on the rooftop structure; the LabVIEW program that was developed for data acquisition and the MATLAB program for developing the thermal models. In order to address the safety issue, temperature test results (obtained in accordance with IEC 61730-2 and UL 1703 safety standards) are presented and analyzed for nine different components of a PV module, i.e., the front glass, substrate/backsheet (polymer), PV cell, j-box ambient, j-box surface, positive terminal, backsheet inside j-box, field wiring, and diode. The temperature test results obtained for about 140 crystalline silicon modules from a large number of manufacturers who tested modules between 2006 and 2009 at ASU/TÜV-PTL were analyzed and presented in this paper under three test conditions, i.e., short-circuit, open-circuit, and short-circuit and shaded. Also, the nominal operating cell temperatures (NOCTs) of the BAPV modules and insulated-back PV modules are presented in this paper for use by BAPV module designers and installers. / Dissertation/Thesis / M.S.Tech Engineering 2010

abstract: While the implementation of both mild hybrid and start-stop technology is widespread as a factory option in newer vehicles, the adaptation of hybrid technology to older or unequipped vehicles has not been fully realized. As such, a straight forward hybrid conversion system that is easily adapted to different vehicles regardless of drivetrain configuration, has been developed and applied to a test vehicle for less than $2,000. System performance was recorded both before and after hybridization using real world drive cycle tracking charts. The vehicle established a fuel economy baseline of 22.93 mpg, and achieved 26.58 mpg after the conversion. This corresponds to a 15.92% increase in fuel economy. Accounting for initial system costs and annual fuel saving, this corresponds to a 6-year payback period. Based on these results, it can be concluded that an inexpensive aftermarket hybrid system is both feasible and effective at improving fuel economy. / Dissertation/Thesis / M.S.Tech Engineering 2012