Matching Items (6)
Filtering by
- Genre: Masters Thesis
Description
Proton exchange membrane fuel cells have attracted immense research activities from the inception of the technology due to its high stability and performance capabilities. The major obstacle from commercialization is the cost of the catalyst material in manufacturing the fuel cell. In the present study, the major focus in PEMFCs has been in reduction of the cost of the catalyst material using graphene, thin film coated and Organometallic Molecular catalysts. The present research is focused on improving the durability and active surface area of the catalyst materials with low platinum loading using nanomaterials to reduce the effective cost of the fuel cells. Performance, Electrochemical impedance spectroscopy, oxygen reduction and surface morphology studies were performed on each manufactured material.
Alkaline fuel cells with anion exchange membrane get immense attention due to very attractive opportunity of using non-noble metal catalyst materials. In the present study, cathodes with various organometallic cathode materials were prepared and investigated for alkaline membrane fuel cells for oxygen reduction and performance studies. Co and Fe Phthalocyanine catalyst materials were deposited on multi-walled carbon nanotubes (MWCNTs) support materials. Membrane Electrode Assemblies (MEAs) were fabricated using Tokuyama Membrane (#A901) with cathodes containing Co and Fe Phthalocyanine/MWCNTs and Pt/C anodes. Fuel cell performance of the MEAs was examined.
Alkaline fuel cells with anion exchange membrane get immense attention due to very attractive opportunity of using non-noble metal catalyst materials. In the present study, cathodes with various organometallic cathode materials were prepared and investigated for alkaline membrane fuel cells for oxygen reduction and performance studies. Co and Fe Phthalocyanine catalyst materials were deposited on multi-walled carbon nanotubes (MWCNTs) support materials. Membrane Electrode Assemblies (MEAs) were fabricated using Tokuyama Membrane (#A901) with cathodes containing Co and Fe Phthalocyanine/MWCNTs and Pt/C anodes. Fuel cell performance of the MEAs was examined.
ContributorsKolli, Sri Harsha (Author) / Madakannan, Arunachalanadar (Thesis advisor) / Nam, Changho (Committee member) / Peng, Xihong (Committee member) / Arizona State University (Publisher)
Created2014
Description
Low temperature fuel cells are very attractive energy conversion technology for automotive applications due to their qualities of being clean, quiet, efficient and good peak power densities. However, due to high cost and limited durability and reliability, commercialization of this technology has not been possible as yet. The high fuel cell cost is mostly due to the expensive noble catalyst Pt. Alkaline fuel cell (AFC) systems, have potential to make use of non-noble catalysts and thus, provides with a solution of overall lower cost. Therefore, this issue has been addressed in this thesis work. Hydrogen-oxygen fuel cells using an alkaline anion exchange membrane were prepared and evaluated. Various non-platinum catalyst materials were investigated by fabricating membrane-electrode assemblies (MEAs) using Tokuyama membrane (# A201) and compared with commercial noble metal catalysts. Co and Fe phthalocyanine catalyst materials were synthesized using multi-walled carbon nanotubes (MWCNTs) as support materials. X-ray photoelectron spectroscopic study was conducted in order to examine the surface composition. The electroreduction of oxygen has been investigated on Fe phthalocyanine/MWCNT, Co phthalocyanine/MWCNT and commercial Pt/C catalysts. The oxygen reduction reaction kinetics on these catalyst materials were evaluated using rotating disk electrodes in 0.1 M KOH solution and the current density values were consistently higher for Co phthalocyanine based electrodes compared to Fe phthalocyanine. The fuel cell performance of the MEAs with Co and Fe phthalocyanines and Tanaka Kikinzoku Kogyo Pt/C cathode catalysts were 100, 60 and 120 mW cm-2 using H22 and O2 gases. This thesis also includes work on synthesizing nitrogen doped MWCNTs using post-doping and In-Situ methods. Post-doped N-MWNCTs were prepared through heat treatment with NH4OH as nitrogen source. Characterization was done through fuel cell testing, which gave peak power density ~40mW.cm-2. For In-Situ N-MWCT, pyridine was used as nitrogen source. The sample characterization was done using Raman spectroscopy and RBS, which showed the presence ~3 at.% of nitrogen on the carbon surface.
ContributorsShah, QuratulAin Jawed (Author) / Madakannan, Arunachalanadar (Thesis advisor) / Tamizhmani, Govindasamy (Committee member) / Macia, Narciso (Committee member) / Arizona State University (Publisher)
Created2012
Description
Hydrogen fuel cells have been previously investigated as a viable replacement to traditional gas turbine auxiliary power unit onboard fixed wing commercial jets. However, so far no study has attempted to extend their applicability to rotary wing aircrafts. To aid in the advancement of such innovative technologies, a holistic technical approach is required to ensure risk reduction and cost effectiveness throughout the product lifecycle. This paper will evaluate the feasibility of replacing a gas turbine auxiliary power unit on a helicopter with a direct hydrogen, air breathing, proton exchange membrane fuel cell, all while emphasizing a system engineering approach that utilize a specialized set of tools and artifacts.
ContributorsNesheiwat, Rod (Author) / Kannan, Arunachala M (Thesis advisor) / Nam, Changho (Committee member) / Mayyas, Abdel Ra'Ouf (Committee member) / Arizona State University (Publisher)
Created2016
Description
As electric powered unmanned aerial vehicles enter a new age of commercial viability, market opportunities in the small UAV sector are expanding. Extending UAV flight time through a combination of fuel cell and battery technologies enhance the scope of potential applications. A brief survey of UAV history provides context and examples of modern day UAVs powered by fuel cells are given. Conventional hybrid power system management employs DC-to-DC converters to control the power split between battery and fuel cell. In this study, a transistor replaces the DC-to-DC converter which lowers weight and cost. Simulation models of a lithium ion battery and a proton exchange membrane fuel cell are developed and integrated into a UAV power system model. Flight simulations demonstrate the operation of the transistor-based power management scheme and quantify the amount of hydrogen consumed by a 5.5 kg fixed wing UAV during a six hour flight. Battery power assists the fuel cell during high throttle periods but may also augment fuel cell power during cruise flight. Simulations demonstrate a 60 liter reduction in hydrogen consumption when battery power assists the fuel cell during cruise flight. Over the full duration of the flight, averaged efficiency of the power system exceeds 98%. For scenarios where inflight battery recharge is desirable, a constant current battery charger is integrated into the UAV power system. Simulation of inflight battery recharge is performed. Design of UAV hybrid power systems must consider power system weight against potential flight time. Data from the flight simulations are used to identify a simple formula that predicts flight time as a function of energy stored onboard the modeled UAV. A small selection of commercially available batteries, fuel cells, and compressed air storage tanks are listed to characterize the weight of possible systems. The formula is then used in conjunction with the weight data to generate a graph of power system weight versus potential flight times. Combinations of the listed batteries, fuel cells, and storage tanks are plotted on the graph to evaluate various hybrid power system configurations.
ContributorsStrele, Thomas (Author) / Nam, Changho (Thesis advisor) / Kannan, Arunachalanadar M (Committee member) / Pollat, Scott L (Committee member) / Arizona State University (Publisher)
Created2016
Description
The greenhouse gases in the atmosphere have reached a highest level due to high number of vehicles. A Fuel Cell Hybrid Electric Vehicle (FCHEV) has zero greenhouse gas emissions compared to conventional ICE vehicles or Hybrid Electric Vehicles and hence is a better alternative. All Electric Vehicle (AEVs) have longer charging time which is unfavorable. A fully charged battery gives less range compared to a FCHEV with a full hydrogen tank. So FCHEV has an advantage of a quick fuel up and more mileage than AEVs. A Proton Electron Membrane Fuel Cell (PEMFC) is the commonly used kind of fuel cell vehicles but it possesses slow current dynamics and hence not suitable to be the sole power source in a vehicle. Therefore, improving the transient power capabilities of fuel cell to satisfy the road load demand is critical.
This research studies integration of Ultra-Capacitor (UC) to FCHEV. The objective is to analyze the effect of integrating UCs on the transient response of FCHEV powertrain. UCs has higher power density which can overcome slow dynamics of fuel cell. A power management strategy utilizing peak power shaving strategy is implemented. The goal is to decrease power load on batteries and operate fuel cell stack in it’s most efficient region. Complete model to simulate the physical behavior of UC-Integrated FCHEV (UC-FCHEV) is developed using Matlab/SIMULINK. The fuel cell polarization curve is utilized to devise operating points of the fuel cell to maintain its operation at most efficient region. Results show reduction of hydrogen consumption in aggressive US06 drive cycle from 0.29 kg per drive cycle to 0.12 kg. The maximum charge/discharge battery current was reduced from 286 amperes to 110 amperes in US06 drive cycle. Results for the FUDS drive cycle show a reduction in fuel consumption from 0.18 kg to 0.05 kg in one drive cycle. This reduction in current increases the life of the battery since its protected from overcurrent. The SOC profile of the battery also shows that the battery is not discharged to its minimum threshold which increasing the health of the battery based on number of charge/discharge cycles.
This research studies integration of Ultra-Capacitor (UC) to FCHEV. The objective is to analyze the effect of integrating UCs on the transient response of FCHEV powertrain. UCs has higher power density which can overcome slow dynamics of fuel cell. A power management strategy utilizing peak power shaving strategy is implemented. The goal is to decrease power load on batteries and operate fuel cell stack in it’s most efficient region. Complete model to simulate the physical behavior of UC-Integrated FCHEV (UC-FCHEV) is developed using Matlab/SIMULINK. The fuel cell polarization curve is utilized to devise operating points of the fuel cell to maintain its operation at most efficient region. Results show reduction of hydrogen consumption in aggressive US06 drive cycle from 0.29 kg per drive cycle to 0.12 kg. The maximum charge/discharge battery current was reduced from 286 amperes to 110 amperes in US06 drive cycle. Results for the FUDS drive cycle show a reduction in fuel consumption from 0.18 kg to 0.05 kg in one drive cycle. This reduction in current increases the life of the battery since its protected from overcurrent. The SOC profile of the battery also shows that the battery is not discharged to its minimum threshold which increasing the health of the battery based on number of charge/discharge cycles.
ContributorsJethani, Puneet V. (Author) / Mayyas, Abdel (Thesis advisor) / Berman, Spring (Committee member) / Ren, Yi (Committee member) / Arizona State University (Publisher)
Created2017
Description
Proton exchange membrane fuel cells (PEMFCs) run on pure hydrogen and oxygen (or air), producing electricity, water, and some heat. This makes PEMFC an attractive option for clean power generation. PEMFCs also operate at low temperature which makes them quick to start up and easy to handle. PEMFCs have several important limitations which must be overcome before commercial viability can be achieved. Active areas of research into making them commercially viable include reducing the cost, size and weight of fuel cells while also increasing their durability and performance. A growing and important part of this research involves the computer modeling of fuel cells. High quality computer modeling and simulation of fuel cells can help speed up the discovery of optimized fuel cell components. Computer modeling can also help improve fundamental understanding of the mechanisms and reactions that take place within the fuel cell. The work presented in this thesis describes a procedure for utilizing computer modeling to create high quality fuel cell simulations using Ansys Fluent 12.1. Methods for creating computer aided design (CAD) models of fuel cells are discussed. Detailed simulation parameters are described and emphasis is placed on establishing convergence criteria which are essential for producing consistent results. A mesh sensitivity study of the catalyst and membrane layers is presented showing the importance of adhering to strictly defined convergence criteria. A study of iteration sensitivity of the simulation at low and high current densities is performed which demonstrates the variance in the rate of convergence and the absolute difference between solution values derived at low numbers of iterations and high numbers of iterations.
ContributorsArvay, Adam (Author) / Madakannan, Arunachalanadar (Thesis advisor) / Peng, Xihong (Committee member) / Liang, Yong (Committee member) / Subach, James (Committee member) / Arizona State University (Publisher)
Created2011