<p> This thesis presents a novel approach towards solving one of the nation&rsquo;s electric and energy sustainability problems and will have a major impact on California&rsquo;s energy policy in meeting its targets, regarding renewable energy and minimizing carbon footprint. The study focuses on examining the technical and economic feasibility of smart micro-grid with distributed generation (DG) system with renewable energy on a coastal city. It presents a method to increase power reliability, redundancy, efficiency and to decrease the greenhouse gases (GHG) emissions contributing to climate change and ensure environmental sustainability. This innovative idea of aggregating multiple micro-grids that encompasses renewable energy from solar and wind, and uses battery storage and natural gas turbine generation for grid stability is unprecedented, which has been demonstrated as part of the results of this study. The proposed system produces enough power to sustain a small city while selling its excess power to adjacent cities. Moreover, this system could adopt other energy sources, not constrained to solar and wind, to exploit an area&rsquo;s particular renewable energy niche (micro-hydro, geothermal, tidal wave, etc.). It is important to note that this system is economically, socially and environmental friendly (pillars of sustainability), through energy resource diversification, while harnessing free and abundant energy. The results of this study can used in designing and implementing a smart micro-grid in any city to meet its renewable energy and sustainability goal.</p><p>

abstract: Over the past decade, proton exchange membrane fuel cells have gained much momentum due to their environmental advantages and commutability over internal combustion engines. To carefully study the dynamic behavior of the fuel cells, a dynamic test stand to validate their performance is necessary. Much attention has been given to HiL (Hardware-in-loop) testing of the fuel cells, where the simulated FC model is replaced by a real hardware. This thesis presents an economical approach for closed loop HiL testing of PEM fuel cell. After evaluating the performance of the standalone fuel cell system, a fuel cell hybrid electric vehicle model was developed by incorporating a battery system. The FCHEV was tested with two different control strategies, viz. load following and thermostatic. The study was done to determine the dynamic behavior of the FC when exposed to real-world drive cycles. Different parameters associated with the efficiency of the fuel cell were monitored. An electronic DC load was used to draw current from the FC. The DC load was controlled in real time with a NI PXIe-1071 controller chassis incorporated with NI PXI-6722 and NI PXIe-6341 controllers. The closed loop feedback was obtained with the temperatures from two surface mount thermocouples on the FC. The temperature of these thermocouples follows the curve of the FC core temperature, which is measured with a thermocouple located inside the fuel cell system. This indicates successful implementation of the closed loop feedback. The results show that the FC was able to satisfy the required power when continuous shifting load was present, but there was a discrepancy between the power requirements at times of peak acceleration and also at constant loads when ran for a longer time. It has also been found that further research is required to fully understand the transient behavior of the fuel cell temperature distribution in relation to their use in automotive industry. In the experimental runs involving the FCHEV model with different control strategies, it was noticed that the fuel cell response to transient loads improved and the hydrogen consumption of the fuel cell drastically decreased. / Dissertation/Thesis / Masters Thesis Engineering 2014

abstract: Performance of photovoltaic (PV) modules decrease as the operating temperatures increase. In hot climatic conditions, the operating temperature can reach as high as 85°C for the rooftop modules. Considering a typical power drop of 0.5%/°C for crystalline silicon modules, a performance decrease of approximately 30% could be expected during peak summer seasons due to the difference between module rated temperature of 25°C and operating temperature of 85°C. Therefore, it is critical to accurately predict the temperature of the modules so the performance can be accurately predicted. The module operating temperature is based not only on the ambient and irradiance conditions but is also based on the thermal properties of module packaging materials. One of the key packaging materials that would influence the module operating temperature is the substrate, polymer backsheet or glass. In this study, the thermal influence of three different polymer backsheet substrates and one glass substrate has been investigated through five tasks: 1. Determination and modeling of substrate or module temperature of coupons using four different substrates (three backsheet materials and one glass material). 2. Determination and modeling of cell temperature of coupons using four different substrates (three backsheet materials and one glass material) 3. Determination of temperature difference between cell and individual substrates for coupons of all four substrates 4. Determination of NOCT (nominal operating cell temperature) of coupons using all four substrate materials 5. Comparison of operating temperature difference between backsheet substrate coupons. All these five tasks have been executed using the specially constructed one-cell coupons with identical cells but with four different substrates. For redundancy, two coupons per substrate were constructed and investigated. This study has attempted to model the effect of thermal conductivity of backsheet material on the cell and backsheet temperatures. / Dissertation/Thesis / Masters Thesis Engineering 2017

Microalgae are gaining considerable attention as a feedstock for biodiesel production. They can be grown away from the croplands and hence do not compromise food crop supplies. The ability of microalgae to capture solar energy and fix CO2 is a promising process for sustainable production of biomass. Chlorella vulgaris may be suitable for biodiesel production due to its faster growth and easier cultivation compared to other strains. The effect of media composition and process conditions on biomass productivity of C. vulgaris are investigated in a laboratory scale photobioreactor. The results show excellent growth of C. vulgaris on 2X Tris-Acetate-Phosphate culture medium, reaching biomass concentrations around 7.7 g/L. The combination of process parameters that result in highest biomass for our system are: agitation at 600 rpm, temperature of 29&deg;C, average light irradiance of 900 muE/ (m2 s), and 4% CO2 in air. The statistical analysis of biomass from fractional factorial experiments confirms that C. vulgaris growth in presence of the aforementioned process parameters can give highest biomass for our system from the process parameters that were studied. However, statistical analysis also reveals that increase in irradiance from 450 muE/ (m 2 s) to 900 muE/ (m2 s) in our system did not have significant effect on biomass concentration.

<p> This thesis focused on the modeling and simulation of a 50 kW Concentrating Solar Power (CSP) plant, which is located in Crowley, Louisiana. The model was developed using System Advisor Model (SAM), which is software created by the National Renewable Energy Laboratory (NREL) for modeling and analyzing different renewable energy systems. The objective of this thesis is to develop a predictive model (using SAM) that will characterize the performance of the power plant and, thus, aid the analysis and evaluation of the plant&rsquo;s performance. The power plant is a research facility of the Solar Thermal Applied Research and Testing (START) Lab. This facility is focused on the development and deployment of renewable energy systems, exploring solar power options in Louisiana, and providing insight into solar power development across different locations. The power plant uses water as its Heat Transfer Fluid (HTF). Part of the design constraint for the model is the low temperature requirement for the power cycle (88 &deg;C&ndash;116 &deg;C). Because the basic ORC model of SAM does not support this low temperature range, a custom power cycle was modeled using the user-defined power cycle option of SAM. Other characteristics and controls of the plant were also properly defined. The model was validated by comparing its predictions with the actual plant data. This comparison showed a good correlation between the predicted results and the actual plant data. The validated model was then used to perform parametric analyses across different locations. The analyses showed that by operating the power plant at the optimal combination of solar multiple and hours of storage, we can achieve about 70% reduction in the cost of electrical energy, which is, indeed, a significant cost reduction.</p><p>

<p> Heat transfer analysis was performed on a novel auger reactor for biomass fast pyrolysis. As part of this analysis, correlations for specific heat capacity and heat transfer coefficients for biomass (sawdust) and sand (used as heat transfer medium) were developed. For sand, the heat transfer coefficient followed a power law distribution with reactor fill level and temperature. For raw biomass, the heat transfer coefficient also showed similar dependence on fill level, but was independent of temperature up to 300&deg;C. These correlations were used in a one dimensional heat transfer model developed to calculate the heating time and heating rate of biomass in the presence of a heat transfer medium (HTM). A heating time of 3 seconds was obtained to raise the temperature of biomass from 298 K to 753 K. Instantaneous heating rates up to 530 K/s were obtained, thus ensuring fast pyrolysis. Further, to study the effect of heating rates on liquid product yields, a previously validated torrefaction-pyrolysis model was used to calculate the liquid yields for torrefied pine forest residues at various heating rates. A threshold heating rate value of 12 K/s was obtained from the model, above which the final product distribution was not affected. The model predicted liquid yield was 54%, in comparison to the experimental yield of 53%, for torrefied pine forest residues without HTM. The steady state experimental heating rate of 36 K/s was observed, which was above the 12 K/s threshold value thus ensuring fast pyrolysis. The results obtained in this paper will be used as a basis for scaling up the reactor configuration to carry out fast pyrolysis without HTM.</p>

Abstract not available.

Biodiesel is a renewable source of energy typically produced in a chemical process known as transesterification. The process involves the reaction of an alcohol with vegetable oil or animal fat in the presence of a catalyst to yield mono-alkyl esters (biodiesel) and glycerol as a by-product. The biodiesel market is amongst the fastest growing renewable energy markets and there is a genuine interest in its development from industry and academia. However, there are some challenges that are facing biodiesel and hindering its commercialization. The major ones are production cost and quality. The process must be cost-effective whilst producing biodiesel that meets international standards (ASTM D6751 and EN 14214). The main objectives of this project were to investigate the use of a continuous membrane reactor for the production of biodiesel from waste vegetable oil feedstock with high free fatty acid (FFA) content and to investigate the effect of membrane pore size on the separation of soap and triglycerides in the reactor. This was achieved through the construction and operation of a lab scale continuous membrane reactor. The membrane reactor integrates many procedures such as combining the chemical reaction and the membrane-based separation in the same unit. The biodiesel was produced by base-catalyzed transesterification. Two levels of FFA in the waste vegetable oil feedstock were studied, 4.8 and 10 mass%. Ceramic membranes were used, with membrane pore sizes ranging from 1 to 800 nm. It was found that the free glycerol and total glycerol content in the fatty acid methyl ester (FAME or biodiesel) produced were significantly below the maximum limit of the ASTM D6751 standard. There was no trend associating changes in membrane pore size with glycerol concentration. Additionally, it was found that the water content in the FAME produced met the ASTM D6751 standard. Furthermore, the results of the soap analysis indicated that the soap dissolved in the alcohol and passed through the membrane. Thus, soap was not completely retained in the reactor. Therefore, the soap produced as a result of using high FFA feedstock in a base-catalyzed transesterification did not affect the FAME production process and the passage of mono-, di-, and triglycerides through the membrane. The quality of the biodiesel produced in this project met the requirements for the ASTM D6751 standard.

Helical tip vortices in the wake of a wind turbine, dynamics of a rising and oscillating bubble and trajectories of cards falling under gravity have been investigated here. The near wake flow field of the wind turbine in the Reynolds number range 103 ≤ Re ≤ 5 × 103 has been explored using qualitative dye flow visualization and quantitative digital particle image velocimetry (DPIV) techniques. Flow visualization studies showed the dye getting trapped in the shape of spirals surrounding the helical vortex cores. It was found that the helical vortex core size was increasing with downstream distance. It was also found that the normalized stream-wise component of the wake velocity decreased with increasing tip-speed ratios. The pitch of the tip vortex monotonically decreased with increasing tip-speed ratios. The evolution of the global wake vorticity field with time has been studied in detail, for the first time. The results indicated that vorticity peaks at the center of the core, as one would expect. The vorticity at the center of the core was also found to decay as the vortex moved downstream, implying that the viscous dissipation was active even at length scales of few diameters. Power spectrum of the stream-wise velocity field at a point showed a distinctive peak at a frequency of 0.5 Hz. In another study, numerical simulations on dynamic motions of bubbles undergoing radial oscillations and rising against to gravity in an ambient quiescent viscous fluid were performed. Bubbles of two different geometric shapes, a spherical cap bubble and a perfectly spherical bubble were considered. Numerical simulations of the nonlinear differential equations showed that radial oscillations of the bubble dramatically modified the rising motion of the bubble. It was found that the rise velocity of an oscillating bubble was much larger than that of a non-oscillating bubble and was strongly oscillatory, with a maximum value attained when the bubble was at its minimum radius. Moreover, the elevation of the oscillating bubble changed suddenly and very steeply, and was much larger than that of a non-oscillating bubble. Finally, aerodynamics of freely falling cards of various geometries was investigated. In this investigation, parallelogram-shape cards were released in still air with their long axis horizontal and acute axis vertical. In the past studies, tumbling and fluttering motions have been observed. Here we observed a new structural instability in which the card moved vertically downwards in the shape of a helix while at the same time undergoing tumbling motions along long axis. In addition, the card was inclined with the vertical and was sinusoidally varying about a mean angle.

There is a growing need to develop the processes to produce renewable fuels and chemicals due to the economical, political, and environmental concerns associated with the fossil fuels. One of the most promising methods for a small scale conversion of biomass into liquid fuels is fast pyrolysis. The liquid product obtained from the fast pyrolysis of biomass is called pyrolysis oil or bio-oil. It is a complex mixture of more than 300 compounds resulting from the depolymerization of biomass building blocks, cellulose; hemi-cellulose; and lignin. Bio-oils have low heating value, high moisture content, are acidic, contain solid char particles, are incompatible with existing petroleum based fuels, are thermally unstable, and degrade with time. They cannot be used directly in a diesel or a gasoline internal combustion engine. One of the challenges with the bio-oil is that it is unstable and can phase separate when stored for long. Its viscosity and molecular weight increases with time. It is important to identify the factors responsible for the bio-oil instability and to stabilize the bio-oil. The stability analysis of the bio-oil showed that the high molecular weight lignin oligomers in the bio-oil are mainly responsible for the instability of bio-oil. The viscosity increase in the bio-oil was due to two reasons: increase in the average molecular weight and increase in the concentration of high molecular weight oligomers. Char can be removed from the bio-oil by microfiltration using ceramic membranes with pore sizes less than 1 µm. Removal of char does not affect the bio-oil stability but is desired as char can cause difficulty in further processing of the bio-oil. Nanofiltration and low temperature hydrogenation were found to be the promising techniques to stabilize the bio-oil. Bio-oil must be catalytically converted into fuels and chemicals if it is to be used as a feedstock to make renewable fuels and chemicals. The water soluble fraction of bio-oil (WSBO) was found to contain C2 to C6 oxygenated hydrocarbons with various functionalities. In this study we showed that both hydrogen and alkanes can be produced with high yields from WSBO using aqueous phase processing. Hydrogen was produced by aqueous phase reforming over Pt/Al2O3 catalyst. Alkanes were produced by hydrodeoxygenation over Pt/SiO2-Al2O3. Both of these processes were preceded by a low temperature hydrogenation step over Ru/C catalyst. This step was critical to achieve high yields of hydrogen and alkanes. WSBO was also converted to gasoline-range alcohols and C2 to C6 diols with up to 46% carbon yield by a two-stage hydrogenation process over Ru/C catalyst (125 °C) followed by over Pt/C (250 °C) catalyst. Temperature and pressure can be used to tune the product selectivity. The hydroprocessing of bio-oil was followed by zeolite upgrading to produce C6 to C8 aromatic hydrocarbons and C2 to C4 olefins. Up to 70% carbon yield to aromatics and olefins was achieved from the hydrogenated aqueous fraction of bio-oil. The hydroprocessing steps prior to the zeolite upgrading increases the thermal stability of bio-oil as well as the intrinsic hydrogen content. Increasing the thermal stability of bio-oil results in reduced coke yields in zeolite upgrading, whereas, increasing the intrinsic hydrogen content results in more oxygen being removed from bio-oil as H2O than CO and CO 2. This results in higher carbon yields to aromatic hydrocarbon and olefins. Integrating hydroprocessing with zeolite upgrading produces a narrow product spectrum and reduces the hydrogen requirement of the process as compared to processes solely based on hydrotreating. Increasing the yield of petrochemical products from biomass therefore requires hydrogen, thus cost of hydrogen dictates the maximum economic potential of the process.