Engineering Commons^™

Modular Supply Network Optimization Of Renewable Ammonia And Methanol Co-Production, Benjamin Akoh

Graduate Theses, Dissertations, and Problem Reports

To reduce the use of fossil fuels and other carbonaceous fuels, renewable energy sources such as solar, wind, geothermal energy have been suggested to be promising alternative energy that guarantee sustainable and clean environment. However, the availability of renewable energy has been limited due to its dependence on weather and geographical location. This challenge is intended to be solved by the utilization of the renewable energy in the production of chemical energy carriers. Hydrogen has been proposed as a potential renewable energy carrier, however, its chemical instability and high liquefaction energy makes researchers seek for other alternative energy carriers. Ammonia …

Group Iv Environmentally Benign, Inexpensive Semiconductor Nanomaterials For Solar Cells, Lisa Je

ENGS 86 Independent Projects (AB Students)

Modern solar cells are composed of silicon, cadmium tellurium, and copper indium gallium diselenide. While these materials are efficient, elements such as cadmium and indium are rare and expensive. To make this renewable energy source more inexpensive and sustainable, the Liu Optics lab is substituting expensive rare earth metals for more commonly found transition state metals. Work has been done to replace the solar cell layers composed of cadmium and gallium to replace them with glass, silicon, and/or thin films. Common metals such as germanium and tin are investigated and characterized to provide a platform for solar cell components.

Hydrogen Generation From Eosin Y-Sensitized Pt/Zno Under Solar Light Irradiation, Tianfang Tian

Electronic Thesis and Dissertation Repository

Hydrogen is a promising alternative energy carrier. Generating hydrogen via photocatalysts is clean and energy saving comparing to the current technology for hydrogen generation. ZnO has been proved to have photocatalytic activities for wastewater treatment by multiple studies. However, there are not enough studies to investigate its potential to generate hydrogen as the photocatalyst under light irradiation. Therefore, we will investigate the photocatalytic ability of Pt/ZnO to generate hydrogen. Triethanolamine (TEOA) was used as sacrificial reagent while Eosin Y was used as sensitizer. Pt/ZnO was characterized and tested for its activity for hydrogen generation in different conditions, which are platinum …

Numerical Characterization Of The Flow Field And Heat Transfer Inside The Receiver Of A Parabolic Trough Solar Collector Carrying Supercritical Co2, Samad Gharehdaghimollahajloo

UNLV Theses, Dissertations, Professional Papers, and Capstones

The aim of this research is to provide a detailed numerical analysis of flow field and heat transfer inside the heat collecting element of a parabolic trough collector. The parabolic trough collector is used as the boiler in a direct Super Critical Carbon Dioxide (S-CO2) Brayton cycle.

A single collector is modeled and analyzed with different inlet conditions. The working fluid is supercritical since its pressure is increased to above critical pressure in the compressor while its temperature reaches 300 °C after passing through the recuperators and before entering the solar field. For the first time, this research considers both …

Novel Synthesis Of Cigs Nanoparticles For Scalable, Benign Inks For Solution Processed Solar Cells, Jacob Fields, Ryan Ellis, Rakesh Agrawal

The Summer Undergraduate Research Fellowship (SURF) Symposium

One potential production route to high efficiency, low cost, photovoltaics (PVs) which was explored is Copper Indium Gallium Sulfide (CIGS) nanocrystal inks for solution processed PVs. A common CIGS nanocrystal ink synthesis utilizes ligands—molecules attached to the particle surface—for colloidal stability, size control, and shape control. It is desirable to devise a novel synthesis which will incorporate a ligand that allows suspensions in more benign solvents than current methods—a desirable characteristic for large scale production. In order to develop the aforementioned synthesis of CIGS nanoparticles, an optimization study of synthesis parameters was performed. Selection of an appropriate solvent, and sulfur …

Fluid Analysis In Solar Heat Pipes, Ben Krumholz, Michael Agavo, William Dundon

Mechanical Engineering

Evacuated tube solar collectors are efficient systems that use heat pipes to facilitate heat transfer. They use incoming solar radiation to heat water. Professor Mason Medizade tasked the team with choosing a component of the system to research and test its influence on system performance. The team investigated the working fluid that runs through the heat pipes. Distilled water, acetone, and ethanol at a range of fill volumes form 1 mL to 11 mL were tested. The team's goal was to find a volume for each fluid to maximize performance of the system. Performance was defined as average temperature rise …

Hybrid Sulfur Process For Solar Production Of Hydrogen, John Jacob Isenhower, Katherine Cross Henderson, Nicholas Joseph Eigenbrot

Senior Theses

Lowering dependence on fossil-based fuels has become a major area of focus in research, especially in transportation fuels. One particularly interesting field is that of hydrogen production. Hydrogen is promising because it has the potential to emit no greenhouse gases when used as fuel and is an excellent vessel for energy storage. Because traditional methods for its generation are inefficient and require nonrenewable fuel use, researchers have begun to focus on thermochemical cycles.

Thermochemical cycles are systems that require heat transfer intrinsically and do not consume fossil fuels nor emit greenhouse gases if renewable energy is used for heating. The …

Integrated Solar Technologies With Outdoor Pedestrian Bridge Superstructure Decking, Richard K. Racz

Masters Theses

Solar technology has been a major topic in sustainable design for many years. In the last five years, however, the solar technology industry has seen a rapid growth in installations and technological advances in cell design. Combined with a rapidly declining overall system cost, the idea of introducing solar technology into a wider range of applications is becoming a focus for engineers and scientists around the world. So many variables which alter solar energy production, such as the sun and surrounding environment, determine whether a solar design is beneficial. This thesis presents a bridge deck surface integrated with solar cells …

Enhanced Solar Photocatalytic Hydrogen Generation And Water Treatment Using Hetero-Structure Photocatalysts, Ghodsieh Malekshoar

Electronic Thesis and Dissertation Repository

Among different approaches to overcome current environmental concerns, heterogeneous photocatalysis is recognized as a promising one. While there are various applications of photocatalysis including water splitting and water treatment, the overall efficiency of this process is still fairly low due to the two dominant drawbacks of current semiconductors, namely wide band gap and fast recombination of photo-generated charges, which restrict the photocatalytic reactions. Designing a hybrid photocatalyst composed of semiconductor hetero-junctions is a viable approach to address these challenges.

The objective of this research project is developing efficient photocatalysts via simple and practical synthesis methods in order to enhance the …

Minimizing Sheet Resistance Of Organic Photovoltaic Cell Top Contact Electrode Layer: Silver Nanowire Concentration Vs. Conductive Polymer Doping Concentration, Caitlyn Cook

Materials Engineering

The top contact electrode layers of nine organic photovoltaic cells were prepared with two varying factors: three Silver nanowire (AgNW) densities deposited on a conductive polymer doped with three concentrations. Silver’s low sheet resistance of 20-Ω/sq is hypothesized to lower the sheet resistance of the anode layer and thus enhance the overall efficiency of the cell. Four-point probe measurements indicated that increasing AgNW density in the top contact electrode layer of an organic photovoltaic cell significantly reduces sheet resistance from 52.2k-Ω/sq to 18.0 Ω/sq. Although an increase in doping concentration of the conductive polymer reduced sheet resistance in low AgNW …

Solar And Visible Light Driven Photocatalysis For Sacrificial Hydrogen Generation And Water Detoxification With Chemically Modified Ti02, Pankaj Chowdhury

PC

Photocatalysis is a recognized approach where light energy is employed to excite the semiconductor material producing electron/hole pair which eventually involves in the detoxification of pollutants and/or water splitting producing hydrogen. Existing photocatalysts suffer from poor activity or no activity in visible light irradiation which restricts them from solar light utilization. This work is focused on two key applications of photocatalysis (i) sacrificial hydrogen generation, and (ii) phenol degradation in visible and/or solar light. Platinum was loaded on TiO2 photocatalyst by solar photo-deposition method. Eosin Y dye was used as a sensitizer for sensitization of platinum loaded TiO2 photocatalyst. The …

A Comprehensive Study Of Cd(Ii) Removal From Aqueous Solution Via Adsorption And Solar Photocatalysis, Samindika Athapaththu

Electronic Thesis and Dissertation Repository

As the increase in industrial technology continue to progress, it results in the increase in heavy metal pollution, creating harmful effects on humans, plants, and animals. Since toxic metals do not degrade easily, they accumulate over time, posing greater danger to living organisms. Removal of these heavy metals is therefore, of great importance. Though many research studies successfully utilized UV photocatalysis with TiO₂ catalyst for the removal of Cd²⁺, none have performed the photoreduction of Cd²⁺ under visible light using eosin-y dye-sensitized TiO₂. The objective of the present research is to study the photocatalytic …

Database For Solar Energy Group, Lei Zhong, Rakesh Agrawal

The Summer Undergraduate Research Fellowship (SURF) Symposium

Copper zinc tin sulfide (CZTS) is the abundant quaternary semiconducting compound which could be used to make solar thin film. Even though its efficiency is lower than the silicon based film, the cost of CZTS solar film will be lower compared to the current silicon based film. Therefore it is really worth to do research and make improvement on its efficiency. So far, the solar energy group already collected a great bunch of data, which could be employed to guide the future experiment. Hence, it is really necessary to build a database to arrange the information we got. Our project …

Photolithography In Fabrication Of Thin-Film Solar Cells, Yusheng Zhu, Rakesh Agrawal

The Summer Undergraduate Research Fellowship (SURF) Symposium

Solar energy has steadily increased its efficiency and cost-effectiveness throughout the past three decades and seems poised to compete with current primary energy (natural gas, oil, coal) as the need for alternative energy sources rises. One type of solar cell, thin-film cells, often relies on use of permanent photomasks in order to imprint a pattern onto the front metal contact. However, these machined metal masks are rigid and do not allow for different designs to be explored as current masks encounter difficulties in machining grids thin enough for optimization. Photolithography, traditionally used in the microfabrication field, provides a method in …

Solar And Visible Light Driven Photocatalysis For Sacrificial Hydrogen Generation And Water Detoxification With Chemically Modified Ti02, Pankaj Chowdhury

P

Photocatalysis is a recognized approach where light energy is employed to excite the semiconductor material producing electron/hole pair which eventually involves in the detoxification of pollutants and/or water splitting producing hydrogen. Existing photocatalysts suffer from poor activity or no activity in visible light irradiation which restricts them from solar light utilization. This work is focused on two key applications of photocatalysis (i) sacrificial hydrogen generation, and (ii) phenol degradation in visible and/or solar light. Platinum was loaded on TiO2 photocatalyst by solar photo-deposition method. Eosin Y dye was used as a sensitizer for sensitization of platinum loaded TiO2 photocatalyst. The …

Solar And Visible Light Driven Photocatalysis For Sacrificial Hydrogen Generation And Water Detoxification With Chemically Modified Ti02, Pankaj Chowdhury

Electronic Thesis and Dissertation Repository

Photocatalysis is a recognized approach where light energy is employed to excite the semiconductor material producing electron/hole pair which eventually involves in the detoxification of pollutants and/or water splitting producing hydrogen. Existing photocatalysts suffer from poor activity or no activity in visible light irradiation which restricts them from solar light utilization. This work is focused on two key applications of photocatalysis (i) sacrificial hydrogen generation, and (ii) phenol degradation in visible and/or solar light. Platinum was loaded on TiO₂ photocatalyst by solar photo-deposition method. Eosin Y dye was used as a sensitizer for sensitization of platinum loaded TiO_{2 …}

Supercritical Fluid Deposition Of Thin Metal Films: Kinetics, Mechanics And Applications, Christos Fotios Karanikas

Doctoral Dissertations 1896 - February 2014

In order to meet the demands of the continuous scaling of electronic devices, new technologies have been developed over the years. As we approach the newest levels of miniaturization, current technologies, such as physical vapor deposition and chemical vapor deposition, are reaching a limitation in their ability to successfully fabricate nano sized electronic devices.

Supercritical fluid deposition (SFD) is a demonstrated technology that provides excellent step coverage for the deposition of metals and metal oxides within narrow, high aspect ratio features. This technique shows the potential to satisfy the demands of integrated circuit miniaturization while maintaining a cost effective process …

Using Computational Fluid Dynamics Modeling To Improve The Performance Of A Solar Co2 Converter, Thomas H. Fletcher, Ralph J. Price, Reed J. Jensen

Faculty Publications

A solar collector to convert CO2 to CO at high temperature was previously developed, achieving a product with 4-6 mol % CO from pure CO2. Modeling results showed that reactions occurred in the thermal boundary layer of the heated zirconia rod at temperatures greater than 2300 K. This paper describes results of computer modeling of advanced designs meant to increase the conversion of CO from CO2. Several design modifications were tested using the model, including changing the cool-down region configuration, increasing the zirconia rod diameter, and changing the zirconia rod shape. Several operational adjustments were also modeled, including reducing the …

Modeling The Direct Solar Conversion Of Co2 To Co And O2, Thomas H. Fletcher

Faculty Publications

At high temperatures (greater than 2300 K), CO₂ is known to dissociate to CO and O. A prototype solar collector was previously demonstrated to achieve such high temperatures, achieving 4-6 mol % CO in the product stream from an inlet stream of pure CO₂. This paper describes the results of computer modeling performed to determine the flow, temperature, and reactions occurring in the prototype device. Of particular interest are the heat-transfer and reaction mechanisms involved and how much photolysis occurs in the prototype. Predictions were performed with two different computational fluid dynamic codes (Fluent and PCGC-3). The …