Methods of generating renewable energy such as through solar photovoltaic (PV) cells and wind turbines offer great promise in terms of a reduced carbon footprint and overall impact on the environment. However, these methods also share the attribute of being highly stochastic, meaning they are variable in such a way that is difficult to forecast with sufficient accuracy. While solar power currently constitutes a small amount of generating potential in most regions, the cost of photovoltaics continues to decline and a trend has emerged to build larger PV plants than was once feasible. This has brought the matter of increased variability to the forefront of research in the industry. Energy storage has been proposed as a means of mitigating this increased variability -- and thus reducing the need to utilize traditional spinning reserves -- as well as offering auxiliary grid services such as peak-shifting and frequency control. This thesis addresses the feasibility of using electrochemical storage methods (i.e. batteries) to decrease the ramp rates of PV power plants. By building a simulation of a grid-connected PV array and a typical Battery Energy Storage System (BESS) in the NetLogo simulation environment, I have created a parameterized tool that can be tailored to describe almost any potential PV setup. This thesis describes the design and function of this model, and makes a case for the accuracy of its measurements by comparing its simulated output to that of well-documented real world sites. Finally, a set of recommendations for the design and operational parameters of such a system are then put forth based on the results of several experiments performed using this model.

A Metal-Insulator-Metal (MIM) diode is a high frequency device used for energy harvesting purpose in the RECTENNA. The main objective of this thesis work is to design, fabricate and characterize a thin-film MIM diode. A key issue associated in this research work is the development MIM diode with nanometer thin insulator region. The reason for the development of MIM diode is to rectify a wide spectrum of AC signal to usable DC power. In this thesis work, a planar MIM diode with Aluminum/Aluminum-Oxide/Gold has been fabricated. The thickness of the insulator region obtained was about 3nm. The Metal and insulator depositions were done by sputtering and plasma oxidation, respectively. I-V Characteristics of the diode was measured by making use of in-house set-up and 70% of the devices on a single wafer yielded with better result. Most of the I-V curves obtained were highly non-linear and asymmetric. Based on the I-V measurement, the logarithmic derivative of I vs. V was plotted and the tunneling behavior was also observed.

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.

<p>Spectrally selective solar absorber using composite Ni-NiO as coating materials was studied. Samples were prepared by dc magnetron sputtering unit named <i>Rulle</i>, which is a miniature copy of an industrial roll-coater unit. Using asymmetric location of the oxygen nozzele, it is possible to form the desired metallic concentration distribution along the sputtering zone under optimized conditions. This distribution can be transferred into a graded film profile by moving the substrate, obtaining good spectral selectivity. For specified mechanical settings (such as locations of gas sprays, target and pump positions etc.), the ratio of used oxygen flow to the corresponding critical oxygen flow, <b>RO</b>, is a dimensionless parameter to control the zone specification. The optimal value is around 0.80 for the <i>Rulle</i>. Optimized zone shows properties with two main parts: the metallic composite part of varied nickel volume fraction and the dielectric part. Two parts of the sputtering zone can form a graded absorbing layer with the right ratio of base and middle layer by the moving substrate technique. Distribution of normalized conductivity, <i>NC</i>, along the absorbing sputtering zone is a simple and good specification of zone property. Profile of graded film prepared by the moving substrate technique can be tailored according to <i>NC</i> distribution. XRD and XPS study confirms the <i>NC</i> results. Simulation reveals that absorption should mainly rely on the intrinsic, but less on the interference mechanism. Used metallic volume fraction of Ni-NiO is 0.3 for main absorbing layer. The front surface reflection loss due to high refractive index can be reduced by adding a layer with low refractive index on the top. Simulation shows that three-layer coatings are a good and simple coating structure. High solar absorptance of 0.97 has been achieved with low thermal emittance of 0.05 by theoretical simulation as well as experimentally prepared samples.</p>

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references.

Spectrally selective solar absorber using composite Ni-NiO as coating materials was studied. Samples were prepared by dc magnetron sputtering unit named Rulle, which is a miniature copy of an industrial roll-coater unit. Using asymmetric location of the oxygen nozzele, it is possible to form the desired metallic concentration distribution along the sputtering zone under optimized conditions. This distribution can be transferred into a graded film profile by moving the substrate, obtaining good spectral selectivity. For specified mechanical settings (such as locations of gas sprays, target and pump positions etc.), the ratio of used oxygen flow to the corresponding critical oxygen flow, <b>RO</b>, is a dimensionless parameter to control the zone specification. The optimal value is around 0.80 for the Rulle. Optimized zone shows properties with two main parts: the metallic composite part of varied nickel volume fraction and the dielectric part. Two parts of the sputtering zone can form a graded absorbing layer with the right ratio of base and middle layer by the moving substrate technique. Distribution of normalized conductivity, NC, along the absorbing sputtering zone is a simple and good specification of zone property. Profile of graded film prepared by the moving substrate technique can be tailored according to NC distribution. XRD and XPS study confirms the NC results. Simulation reveals that absorption should mainly rely on the intrinsic, but less on the interference mechanism. Used metallic volume fraction of Ni-NiO is 0.3 for main absorbing layer. The front surface reflection loss due to high refractive index can be reduced by adding a layer with low refractive index on the top. Simulation shows that three-layer coatings are a good and simple coating structure. High solar absorptance of 0.97 has been achieved with low thermal emittance of 0.05 by theoretical simulation as well as experimentally prepared samples.

This thesis is on the estimation models for the daily global solar irradiation on a horizontal surface at the surface of the Earth. New approaches are developed and applied to 15 locations of Turkey and Germany. The main idea in developing the new models is to link the surface data to satellite imagery. Totally three new modeling approaches are developed and tested. Surface data of daily bright sunshine hours (s) and cloud index (n) values derived from satellite images are the main input parameters. In the first approach, monthly coefficients of Angstr&ouml / m linear relation between daily solar irradiation and daily bright sunshine hours are used to replace the clear sky irradiance calculations of HELIOSAT model. In the second approach new correlations are obtained between daily bright sunshine hours (s) and cloud index (n). Last model that is developed uses a new correlation expression between daily solar irradiation and daily data of s and n and this expression is derived using a physical consideration. The performances of the proposed models are tested against conventional methods (mainly, satellite-based HELIOSAT and ground-based linear Angstr&ouml / m-Prescott type). The results show that the use of sunshine duration together with the cloud index is quite satisfactory in the estimations of daily global solar irradiation. The accuracy of estimations of the combined models is considerably higher than the conventional approaches. Therefore, we propose to use the new approaches to estimate daily global irradiation whenever the data of bright sunshine hours is available for the location of interest or a nearby station. In addition, for a point on the earth surface, depending on the data in hand, suitable and most accurate models of estimations are proposed for that point.

This study examines two of the reasons that prevent people from taking part in green electricity programs: trust concerns that these programs may raise, and lack of benefits that come with visibility of participants’ involvement. While the current literature takes notice of their influence, in this study it was decided to investigate both factors in more detail. In particular, with the help of a survey, the study focused on the reactions of electricity consumers to the proposition of participation in green electricity programs in a controlled setting, in which levels of trust concerns raised and benefits of visibility provided by the programs could be varied. The study was conducted in Oakville, an affluent southern Ontario (Canada) suburb. The results are based on 160 received responses to 500 questionnaires that were sent out by mail. While the results of this study point towards the conclusion that both factors have an influence on participation in green electricity programs, their relative strength cannot be estimated by these results. One can, however, claim that the combined influence of trust concerns and benefits of visibility is quite strong. This research shows that at a 95% confidence level, willingness to participate in a program that proposes paying premium for electricity from solar panels installed on a participant’s roof (low trust concerns, high benefits of visibility) is 30% + 19.3% higher than willingness to participate in a program that proposes paying premium for electricity from undisclosed solar farms (high trust concerns, low benefits of visibility). Additional data about trust concerns, appreciation of benefits of visibility, and concerns about installation of solar panels on one’s own roof, provided by the survey, are also presented in the text. In conclusion, it is recommended that future research should more clearly separate the strength of influence of trust concerns from the influence of benefits of visibility on green electricity program participation. It is also important to study which features of these programs make them more trustworthy and visible. An important implication of this study for policy makers and green electricity proponents is to concentrate on allaying trust concerns, and enhancing benefits of visibility when designing policies or drafting plans for green electricity programs. The creation of an independent green electricity program certification system and a greater accent on the local presence of such programs is suggested.

This dissertation presents dynamic reactive power control of isolated power systems. Isolated systems include MicroGrids in islanded mode, shipboard power systems operating offshore, or any other power system operating in islanded mode intentionally or due to a fault. Isolated power systems experience fast transients due to lack of an infinite bus capable of dictating the voltage and frequency reference. This dissertation only focuses on reactive control of islanded MicroGrids and AC/DC shipboard power systems. The problem is tackled using a Model Predictive Control (MPC) method, which uses a simplified model of the system to predict the voltage behavior of the system in future. The MPC method minimizes the voltage deviation of the predicted bus voltage; therefore, it is inherently robust and stable. In other words, this method can easily predict the behavior of the system and take necessary control actions to avoid instability. Further, this method is capable of reaching a smooth voltage profile and rejecting possible disturbances in the system. The studied MicroGrids in this dissertation integrate intermittent distributed energy resources such as wind and solar generators. These non-dispatchable sources add to the uncertainty of the system and make voltage and reactive control more challenging. The model predictive controller uses the capability of these sources and coordinates them dynamically to achieve the voltage goals of the controller. The MPC controller is implemented online in a closed control loop, which means it is self-correcting with the feedback it receives from the system.

Concentrating Photovoltaic systems are good candidates for low cost and clean electricity generation from solar energy. CPV means replacing much of the expensive semiconductor photovoltaic cells with the cheaper optics. Although the idea is simple, CPV systems have several problems inherent to their system design, such as module thickness, expensive PV cells and overheating. Light guide systems are good alternatives to classical CPV systems that can clear off most of the problems of those systems. In this thesis we explore a new light-guide based solar concentrator by optical design and simulations. It is shown that this solar concentrator can reach 1000x geometric concentration, 96.5% optical efficiency with a &plusmn / 1 degree acceptance angle. As a result of simulations, effectiveness of the horizontally staggered light guide solar concentrators is proved. A practical module study is carried on to improve the knowledge related to light guide CPV systems. The concentrator geometry is fabricated as a medium concentrator system with a geometric concentration of 45x and +-2 degrees acceptance angle. With the prototype level injection molding 74% optical efficiency is achieved and can be improved with a better mold manufacturing. A cost analyses is also performed with real manufacturing parameters and it is shown that grid parity can be achieved with this kind of light guide solar concentrators.