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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The potential of fuel cells to reduce energy demands and pollution from the UK transport sector

Adams, Victor W. January 1998 (has links)
Atmospheric carbon dioxide and pollution due to the burning of fossil fuels is increasing. Many scientists attribute global warming to the rising levels of carbon dioxide and other pollutants, some of which also pose risks to health. These can be reduced by the more efficient use of conventional fuels and the development of non-polluting energy resources. Fuel cells offer a highly efficient and low polluting method of generating electricity, and are under development for both the power generation and transport sectors. There is a need to assess (a) emissions from fuel cells using various fuels and (b) ways of introducing such technology to transportation in the near future. Fuel consumption, energy and emissions from the production and use of fuels (hydrogen, methane, propane, petrol, diesel, alcohols and rape methyl ester) are calculated per kilowatt hour of fuel cell output over a range of efficiency. These are compared with those for internal combustion engines with advanced exhaust control and for the recharging of battery driven vehicles. The results, which are applicable to both transport and power generation, enable the best low pollution fuels to be selected and are used to calculate through life emissions for public transport buses. Fuel cells are an ideal solution to reduce pollution from transport, but their commercial development in this field is further away than that for stationary applications. Thus, a transition stage is recommended where fuel cell electrical power stations, based on existing demonstrators, are used to recharge fleets of battery driven vehicles during the development of mobile fuel cell systems. These fleets include public transport and commercial vehicles. Also, fuel cell power stations could provide energy for electric trains. A combined system is proposed where electric trains recharge battery driven commercial vehicles during long journeys. The above proposals would enhance fuel cell development, introducing them alongside current transport systems, possibly using the same fuel.
2

An enviro-economic assessment of waste vegetable oil to biodiesel conversion : an analysis of cost and GHG emissions for the University of Texas at Austin

Ernst, Kendall Robert 03 October 2014 (has links)
With its multiple dining halls, close proximity to restaurants, and diesel vehicle fleet, the University of Texas at Austin (UT) has both the supply of raw materials to implement a waste vegetable oil to biodiesel recycling program and the capacity to use it. At face value, implementing a large-scale recycling program provides a source of cheap, low emissions fuel. However, the feasibility of such a program is contingent on its economic cost and environmental impact relative to alternative fuel sources. Thus, this research estimated the greenhouse gas (GHG) inventories and the unit cost associated with 1 megajoule worth of recycled biodiesel derived from three production processes –Alkali Catalyzed, Acid Catalyzed, and Supercritical Methanol–using environmental life cycle assessment and life cycle costing. These GHG inventories and unit costs were then compared to the conventional diesel and oilseed biodiesel sources that make up UT’s current fuel portfolio. This analysis suggested that implementing a recycling program using a Supercritical Methanol biodiesel conversion process would have the lowest combined GHG impact and unit cost, although as an emerging technology, it poses a high investment risk. In general, these findings are encouraging to the success and impact of a large-scale recycling program. / text
3

ANALYSIS OF FACTORS AFFECTING FARMERS’ WILLINGNESS TO ADOPT SWITCHGRASS PRODUCTION IN THE SOUTHERN UNITED STATES AND AN EXCEL SPREADSHEET-BASED DECISION TOOL FOR POTIENTIAL SWITCHGRASS PRODUCERS

Qualls, Donald Joshua 01 May 2011 (has links)
The increased need for and scarcity of hydrocarbon energy pushes the search and extraction of reserves toward more technically difficult deposits and less efficient forms of hydrocarbon energy. The increased use of hydrocarbons also predicates the increased emission of detrimental chemicals in our surrounding environment. For these reasons, there is a need to find feasible sources of renewable energy that could prove to be more environmentally friendly. One possible source that meets these criteria is biomass, which in the United States is the largest source of renewable energy as it accounts for over 3 percent of the energy consumed domestically and is currently the only source for liquid renewable transportation fuels. Continued development of biomass as a renewable energy source is being driven in large part by the Energy Independence and Security Act of 2007 that mandates that by 2022 at least 36 billion gallons of fuel ethanol be produced, with at least 16 billion gallons being derived from cellulose, hemi-cellulose, or lignin. However, the production of biomass has drawbacks. The market for cellulosic bio-fuel feedstock is still under development, and being an innovative technique, there is a lack of production knowledge on the side of the producer. Some studies have been conducted that determine farmers’ willingness to produce switchgrass, however, they have been limited in geographic scope and additional research is warranted considering a broader area. Also, there have been production decision tools aimed at bio-mass, but these have either not been aimed at switchgrass specifically or have been missing key costs such as those incurred in storage. The overall objectives of this study are: 1.) to analyze the willingness of producers in the southeastern United States to plant switchgrass as a biofuel feedstock, 2.) to estimate the area of switchgrass they would be willing to plant at different switchgrass prices, 3.) to evaluate the factors that influence a producer’s decision to convert acreage to switchgrass, and 4.) to present a spreadsheet-based decision tool for potential switchgrass producers.
4

Alternativa drivmedel : Vilket alternativt drivmedel uppfyller bäst Försvarsmaktens behov? / Alternative fuels : Which alternative fuel meets the Swedish Armed forces requirements?

Djuvfeldt, David January 2009 (has links)
<p>This essay is written within my education for Technical Officer in the Swedish armed forces. The essay describes the alternative fuels that the Swedish armed forces can make use of if the supply of fossil fuels is insecure. The alternative fuels that are described and compared are; Synthetic diesel, Organic diesel, Methanol and Ethanol. The essay describes the process of producing the alternatives, the need for modification and the economics for each alternative. The alternatives are compared and assessed for their ability to secure the supply of fuel to the Swedish Armed Forces. The result of the study is that, while synthetic diesel has the best chemical constitution but is not produced in Sweden, the best alternative fuel for the Swedish armed forces at this moment is organic diesel.</p>
5

Thermal aspects of using alternative nuclear fuels in supercritical water-cooled reactors

Grande, Lisa Christine 01 November 2010 (has links)
A SuperCritical Water-cooled Nuclear Reactor (SCWR) is a Generation IV concept currently being developed worldwide. Unique to this reactor type is the use of light-water coolant above its critical point. The current research presents a thermal-hydraulic analysis of a single fuel channel within a Pressure Tube (PT) - type SCWR with a single-reheat cycle. Since this reactor is in its early design phase many fuel-channel components are being investigated in various combinations. Analysis inputs are: steam cycle, Axial Heat Flux Profile (AHFP), fuel-bundle geometry, and thermophysical properties of reactor coolant, fuel sheath and fuel. Uniform and non-uniform AHFPs for average channel power were applied to a variety of alternative fuels (mixed oxide, thorium dioxide, uranium dicarbide, uranium nitride and uranium carbide) enclosed in an Inconel-600 43-element bundle. The results depict bulk-fluid, outer-sheath and fuel-centreline temperature profiles together with the Heat Transfer Coefficient (HTC) profiles along the heated length of fuel channel. The objective is to identify the best options in terms of fuel, sheath material and AHFPS in which the outer-sheath and fuel-centreline temperatures will be below the accepted temperature limits of 850°C and 1850°C respectively. The 43-element Inconel-600 fuel bundle is suitable for SCWR use as the sheath-temperature design limit of 850°C was maintained for all analyzed cases at average channel power. Thoria, UC2, UN and UC fuels for all AHFPs are acceptable since the maximum fuel-centreline temperature does not exceed the industry accepted limit of 1850°C. Conversely, the fuel-centreline temperature limit was exceeded for MOX at all AHFPs, and UO2 for both cosine and downstream-skewed cosine AHFPs. Therefore, fuel-bundle modifications are required for UO2 and MOX to be feasible nuclear fuels for SCWRs. / UOIT
6

Alternativa drivmedel : Vilket alternativt drivmedel uppfyller bäst Försvarsmaktens behov? / Alternative fuels : Which alternative fuel meets the Swedish Armed forces requirements?

Djuvfeldt, David January 2009 (has links)
This essay is written within my education for Technical Officer in the Swedish armed forces. The essay describes the alternative fuels that the Swedish armed forces can make use of if the supply of fossil fuels is insecure. The alternative fuels that are described and compared are; Synthetic diesel, Organic diesel, Methanol and Ethanol. The essay describes the process of producing the alternatives, the need for modification and the economics for each alternative. The alternatives are compared and assessed for their ability to secure the supply of fuel to the Swedish Armed Forces. The result of the study is that, while synthetic diesel has the best chemical constitution but is not produced in Sweden, the best alternative fuel for the Swedish armed forces at this moment is organic diesel.
7

Analysis of a Potential Hydrogen Refuelling Network Using Geographic Information Systems: A Case Study of the Kitchener Census Metropolitan Area

England, Ashley January 2012 (has links)
This thesis provides macro-, meso- and micro-level analyses of a potential hydrogen refuelling network with a case study for the Kitchener census metropolitan area in Canada. It provides recommendations on the appropriate number of stations required to meet estimated demand for hydrogen refuelling. Furthermore, scenarios are produced using geographic information systems (GIS) to show possible networks. Micro-level analysis brings in the planning aspect of hydrogen specific zoning codes and the possible impacts of citizen and stakeholder resistances to hydrogen.
8

Analysis of a Potential Hydrogen Refuelling Network Using Geographic Information Systems: A Case Study of the Kitchener Census Metropolitan Area

England, Ashley January 2012 (has links)
This thesis provides macro-, meso- and micro-level analyses of a potential hydrogen refuelling network with a case study for the Kitchener census metropolitan area in Canada. It provides recommendations on the appropriate number of stations required to meet estimated demand for hydrogen refuelling. Furthermore, scenarios are produced using geographic information systems (GIS) to show possible networks. Micro-level analysis brings in the planning aspect of hydrogen specific zoning codes and the possible impacts of citizen and stakeholder resistances to hydrogen.
9

Methanogenic Generation of Biogas from Synthesis-Gas Fermentation Wastewaters

Taconi, Katherine Ann 07 August 2004 (has links)
As societies around the world become increasingly more dependent on fossil based fuels, the need to investigate alternative fuel sources becomes more pressing. Renewable, biomass-based carbon sources obtained from the biosphere can be gasified to produce synthesis gas, which can in turn be fermented to produce fuel-grade ethanol. A byproduct of ethanol production via fermentation is acetic acid. An optimized ethanol fermentation process should produce a wastewater stream containing less than 2 g/L of acetic acid. This is not enough acid to justify recovery of the acid; however it is a high enough concentration that treatment of the stream is required before it can be discharged. The purpose of this research was to convert the acetic acid into biogas, producing a twoold result: removal of the acid from the wastewater stream and the production of methane, which is a valuable source of energy. Microorganisms known as methanogens will consume acetic acid to produce methane and carbon dioxide under anaerobic conditions. The goal of this research was to optimize methane production from the wastewater stream discharged from an ethanol to syngas facility. Sludge containing methanogenic organisms was obtained from the anaerobic digester of a wastewater treatment facility and used as inoculum in batch reactors containing a synthetic acetic acid solution. Variables such as the type and amount of supplied nutrients, acid concentration, pH, cell acclimation, oxygen exposure, headspace gas composition, and agitation rate were examined. The effects of these parameters on the amount of biogas produced and acetic acid degraded were used to evaluate and optimize reactor performance. Additional experimentation further evaluating methanogenesis at low pH was also conducted using a laboratory scale semi-continuous fermentor. Finally, advanced analytical techniques were used to evaluate changes in organism population with respect to changes in reactor operational parameters. The results of this research were used to estimate kinetic parameters, develop different full-scale reactor design models, and estimate the both the cost of wastewater treatment as well as the value of the methane produced.
10

Syngas From Biomass Gasification As Fuel For Generator

Shah, Ajay 02 May 2009 (has links)
The emergence of biomass based energy warrants the evaluation of syngas from biomass gasification as a fuel for personal power systems. The objectives of this study were to determine the performance and exhaust emissions of a commercial 5.5 kW generator modified for operation with 100% syngas at different syngas flows and to compare the results with those obtained for gasoline operation at same electrical power. Maximum power output for gasoline operation was 2451 W and maximum power output for syngas operation was 1392 W. Overall efficiencies of the generator were same at maximum electrical power outputs for operation with both the fuels. At four different electrical power output categories, the exhaust concentrations of carbon monoxide and oxides of nitrogen were significantly lower while the carbon dioxide emissions were significantly higher for the syngas operation. The unit cost of electricity generation was $6.38/kWh for syngas operation and $0.56/kWh for gasoline operation.

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