• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 44
  • 9
  • 7
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 83
  • 83
  • 25
  • 21
  • 14
  • 13
  • 12
  • 12
  • 12
  • 11
  • 9
  • 9
  • 8
  • 8
  • 8
  • 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.
21

Determinants of Alternative Fuel Technology for Small Road Freight Transport Companies in Sweden

Arhall, Johanna, Reis, Manuel January 2023 (has links)
The transportation sector plays a significant role in global carbon emissions, emphasizing the need for transitioning to alternative fuel technologies. This thesis primarily aims to examine the factors that influence small road freight transport companies in Sweden when transitioning to alternative fuel technology. The focus is on identifying these determinants and their respective significance, utilizing a company internal Resource-Based view as the analytical framework. Semi-structured interviews were conducted among small road freight transport companies, with data analyzed using pattern and keyword matching analysis. The results reveal multiple determinants within financial, technological and organizational resources. Range, purchase cost, and customer demand emerged as the most influential determinants, with range limitations hindering adoption and high costs deterring investment. However, customer demand for eco-friendly transport presents an opportunity for companies to gain a competitive advantage. Company size, cargo type, and operational constraints also influence decision-making. In the data selection, micro companies exhibit a higher propensity for drop-in alternative fuels, while small-sized companies engaged in short-haul transportation are more open to alternative fuel adoption and riskier investments. Risk-averse followers tend to stick to established practices. Policymakers are recommended to invest in infrastructure, provide subsidies, and implement regulations to incentivize adoption, while vehicle producers should optimize designs and collaborate with fuel producers. Further research is advised to investigate the viability of different low-carbon fuel alternatives, explore challenges and motivations faced by different company types, and conduct comparative studies. Quantitative research methods can offer broader insights into this area of study.
22

An examination of the factors influencing the decision to adopt alternative fuel vehicles

Campbell, Amy R. January 2014 (has links)
Concerns over the environmental impacts of the transport sector have led to the United Kingdom (UK) Government establishing a legally binding commitment of an 80% reduction in greenhouse gas emissions by 2050 (relative to the 1990 baseline) through the Climate Change Act 2008. The decarbonisation of the transport sector by 2050 will substantially contribute towards achieving this target. Technological innovations, therefore, have an important role in supporting policy objectives. One innovation that is being developed for this purpose in the transport sector is an alternative fuel vehicle. While there are several alternative fuel vehicle technologies, the only two with zero tailpipe (exhaust) emissions are battery electric vehicles and hydrogen fuel cell vehicles. Both of these technologies are not yet at a stage in their development where they can successfully compete with conventional fuel vehicles (internal combustion engine vehicles). They face a variety of technological hurdles that include range, performance, cost, and infrastructure. Hydrogen fuel cell vehicles are not commercially available, although battery electric vehicles have been on the commercial market for several years. Uptake of alternative fuel vehicles is occurring at a slower pace than hoped by policy makers and manufacturers. The aim of this thesis is to examine the factors influencing the decision to adopt an alternative fuel vehicle, and is underpinned by Rogers (2003) Diffusion of Innovations theory. The Innovation-Decision Process from this theory posits that an individual must first know about an innovation before forming an attitude about it. Innovativeness is instrumental in determining the knowledge an individual has of an innovation and how early in the diffusion process they are likely to become an adopter. Perceptions of the innovation are influential in forming an attitude towards it. The focus of the research is on Birmingham, the UK s second largest city. The first stage of the research involves establishing the locations of individuals across the city that possess socio-demographic characteristics associated with early adopters of alternative fuel vehicles. This is achieved by applying cluster analysis to Birmingham census data, which enabled the identification of a strong spatial cluster of potential early adopters in the suburb of Sutton Coldfield. In the second stage of the research, a household questionnaire was undertaken with 413 respondents in Sutton Coldfield. The analysis of the questionnaire data firstly involves the verification of the early adopter characteristics from stage one by examining the relationship of these characteristics with innovativeness. Analysis is then undertaken of the level of knowledge and the perceptions that the respondents have of alternative fuel vehicles. The final step in the analysis is an evaluation of the characteristics of current models of electric vehicles and how well aligned they are with the driving needs and vehicle expectations of respondents. The results confirm that the knowledge of alternative fuel vehicles is limited and individual perceptions have led to the development of negative attitudes towards them. Socio-demographic characteristics were significant in influencing these factors. There were 5% (21) of respondents who have previously considered the adoption of an electric vehicle but have not yet done so. There is evidence from the survey of active rejection among a small number of respondents. The reasons largely relate to three problems: purchase price, limited range, and poor infrastructure availability. However, the majority of respondents have passively rejected alternative fuel vehicles, such that they have never given consideration to the adoption of one. This confirms that a concerted effort is required to inform the general public about alternative fuel vehicles. Opportunities for increasing adoption have been identified for policy and marketing, including education and awareness-raising campaigns.
23

Manufacturer [Sic] of Densified-Refuse Derived Fuel (d-RDF) Pellets and Methods for the Determination of d-RDF Pellet Densities

Attili, Bassam Saleem 12 1900 (has links)
There are 150 million tons of Municipal Solid Waste (MSW) annually produced in the United States, which is approximately equivalent to 150 million barrels of oil. MSW production is inexhaustible, and is increasing on an annual per capita basis of approximately three per cent. After controlling the moisture and adding a binder, the combustible portion of MSW was converted to pellets. The objects of this project were to 1) evaluate the binder, 2) prepare the pellets, and 3) evaluate the pellets with regard to density. The manufacture of pellets was conducted at the Naval Air Station, Jacksonville, Florida. The evaluation of the binders and the pellets was done at North Texas State University (NTSU). There were three procedures for measuring the density. The first, using water displacement, was from the American Society for Testing and Material (ASTM). The second, using wax coating, was also from ASTM. The third, using sharply-cut cylindrical pellets, was developed at NTSU.
24

Padrões de alocação de carbono estrutural e não estrutural em cinco espécies de lentilhas d´água (Lemnaceae) / Patterns of structural and non-structural carbon allocation in five species of duckweeds (Lemnaceae)

Pagliuso, Débora 13 August 2018 (has links)
Lentilhas d´água são as menores angiospermas aquáticas monocotiledôneas, as quais são classificadas em duas subfamílias (Lemnoideae e Wolffioideae) que contemplam trinta e sete espécies representando cinco gêneros: Spirodela, Landoltia, Lemna, Wolffiella e Wolffia (APPENROTH; BORISJUK; LAM, 2013; BORISJUK et al ., 2015; FAO, 1999; LANDOLT, 1992, LES et al ., 2002). Essas plantas apresentam rápida reprodução vegetativa o que implica no acúmulo acelerado de carboidratos e proteínas, que por sua vez, confere uma enorme aplicação industrial e biotecnológica, especialmente na bioenergia (APPENROTH; BORISJUK; LAM, 2013; FAO, 1999). O balanço de carbono no crescimento relaciona-se com à assimilação fotossintética, armazenamento e consumo desses compostos, que são influenciados pela intensidade de luz (SMITH; STITT, 2007; STITT; ZEEMAN, 2012). O maior dreno de carbono assimilado é para a síntese de parede celular e sacarose, portanto, conhecendo a composição dos polissacarídeos e suas interações junto com o conteúdo de carboidratos não estruturais impacta a produção de combustíveis alternativos. O presente trabalho visou quantificar e analisar os carboidratos estruturais (açúcares de parede celular apiose, arabinose, fucose, ramnose, glicose, xilose, galactose e manose) e não estruturais (açúcares solúveis e de armazenamento sacarose, frutose, rafinose, glicose e amido) de três espécies de Lemnoideae e duas Wolffioideae comparando com as taxas de crescimento dessas plantas. / Duckweeds are the smallest aquatic monocots classified in two subfamilies (Lemnoideae and Wolffioideae) that contemplates thirty-seven species representing five genera: Spirodela, Lemna, Landoltia, Wolffia and Wolffiella . These plants display fast vegetative reproduction, which implies a rapid accumulation of carbohydrates and protein, conferring them biotechnological and industrial applications, especially in bioenergy. Carbon balance among growth is related to photosynthetic assimilation, storage, and consume of compounds which are influenced by light intensity. The major sink of the carbon assimilated is to cell wall and sucrose synthesis, thereby knowing the polysaccharides composition and their interactions together with the non-structural carbohydrates content may impact the alternative fuels production. The present work aimed to quantify and comparative analyze structural (cell wall sugars apiose, arabinose, fucose, rhamnose, glucose, xylose, galactose, and mannose) and nonstructural (storage and soluble sugars starch, sucrose, glucose, raffinose, and fructose) carbohydrates of three Lemnoideae and two Wolffioideae species correlating to its growth rates.
25

Electrochemical generation of hydrogen

Syed Khurram, Raza January 2017 (has links)
Global warming and the energy crisis are two of the greatest challenges on which mankind is currently focused. This has forced governments and other organisations to think how to protect the environment and how to reduce fuel costs. A variety of new and exciting technologies are being investigated to address the energy problem. Alternative energy sources such as solar power, fuel cells, wind power and tidal waves are active areas of commercial and scientific pursuit. A major area of current research is moving towards the hydrogen economy and hydrogen based energy systems. Hydrogen can be produced in many ways, most commonly by steam reforming of hydrocarbon (70% to 85% thermal efficiency) but the downside is that it releases carbon mono oxide (CO)), compared with commercial PEM electrolysers where performance has been reported to be 56 -73% at normal temperature pressure(NTP) with zero carbon emission. Electrochemical production of hydrogen has several advantages: (i) It gives pure hydrogen. (ii) It allows portability (e.g. Solar energy could be used to power the electrochemical cell). (iii) It can be produced on demand. The generation of Hydrogen via electrolysis has been the subject of many studies over the last two hundred years. However, there is still room for further work to improve both the efficiency of the process and methods of storage of the gas. The cleanest method at present is to produce hydrogen by electrolysis, and the main focus of this research is to design and develop such a green energy fuel cell for on-demand application. The aim of the work presented in this thesis was to further investigate the electrolysis method for hydrogen production. An Electrochemical fuel cell contains a minimum of two electrodes: the positively charged electrode called the anode where oxygen bubble will form, and the second negatively charged electrode called the cathode, where hydrogen bubbles will form during a chemical reaction caused by applying electrical current between these electrode. The project was initiated with the objective of finding a low cost solution for on-demand hydrogen generation. To establish a starting point, the first cell (cell-1) design was based on the work of Stephen Barrie Chambers (see chapter 3) to check the performance levels. The fabrication of the cell-1 design resulted in a mixture of hydrogen and oxygen in the same chamber, which means the cell-1 design, has a possible fire and explosion hazard. The device also has the drawback of lower performance of hydrogen production; columbic efficiency is between 40% to 46% at 1 amp to 3 amp current in 30% KOH alkaline solution. However, the advantage of reproducing Stephen’s innovation is that it allowed a quick and deep understanding of hydrogen generation. This thesis presents recent work on the fabrication of low cost electrolysis cells containing continuous flow alkaline (KOH, up to 30%) electrolyte using low cost electrodes (stainless steel 316) and membranes based on ultrahigh molecular weight polyethylene (UHMW PE) to produce hydrogen without the hazard of fire and explosion. In this research an On-Demand Hydrogen Generation cell-3 achieved a 95% hydrogen generation coulombic efficiency, which is about 49% efficiency improvement as compared to the stainless steel electrode, and was 22% better than the nano structured electrode. The typical cell voltage is 2.5 V at current flow ranging from 30 to 120 mA cm-2 in 30% KOH electrolyte. The achievement here of such high efficiencies paves the way for more research in the areas of space management, electrode surface structure and flow control (based on the application requirement). This invention can be used for aeronautic, marine and automotive application as well as in many other areas.
26

An experimental study of ethanol-diesel dual-fuel combustion for high efficiency and clean heavy-duty engines

Bernardes Pedrozo, Vinícius January 2017 (has links)
Higher atmospheric concentration of greenhouse gases (GHG) such as carbon dioxide and methane has contributed to an increase in Earth's mean surface air temperature and caused climate changes. This largely reflects the increase in global energy consumption, which is heavily dependent on oil, natural gas, and coal. If not controlled, the combustion of these fossil fuels can also produce high levels of nitrogen oxides (NOx) and soot emissions, which adversely affect the air quality. New and extremely challenging fuel efficiency and exhaust emissions regulations are driving the development and optimisation of powertrain technologies as well as the use of low carbon fuels to cost-effectively meet stringent requirements and minimise the transport sector's GHG emissions. In this framework, the dual-fuel combustion has been shown as an effective means to maximise the utilisation of renewable liquid fuels such as ethanol in conventional diesel engines while reducing the levels of NOx and soot emissions. This research has developed strategies to optimise the use of ethanol as a substitute for diesel fuel and improve the effectiveness of dual-fuel combustion in terms of emissions, efficiency, and engine operational cost. Experimental investigations were performed on a single cylinder heavy-duty diesel engine equipped with a high pressure common rail injection system, cooled external exhaust gas recirculation, and a variable valve actuation system. A port fuel injection system was designed and installed, enabling dual-fuel operation with ethanol energy fractions up to 0.83. At low engine loads, in-cylinder control strategies such as the use of a higher residual gas fraction via an intake valve re-opening increased the combustion efficiency (from 87.7% to 95.9%) and the exhaust gas temperature (from 468 K to 531 K). A trade-off between operational cost and NOx reduction capability was assessed at medium loads, where the dual-fuel engine performance was less likely to be affected by combustion inefficiencies and in-cylinder pressure limitations. At high load conditions, a Miller cycle strategy via late intake valve closing decreased the in-cylinder gas temperature during the compression stroke, delaying the autoignition of the ethanol fuel and reducing the levels of in-cylinder pressure rise rate. This allowed for the use of high ethanol energy fractions of up to 0.79. Finally, the overall benefits and limitations of optimised ethanol-diesel dual-fuel combustion were compared against those of conventional diesel combustion. Higher net indicated efficiency (by up to 4.4%) combined with reductions in NOx (by up to 90%) and GHG (by up to 57%) emissions can help generate a viable business case of dual-fuel combustion as a technology for future high efficiency and clean heavy-duty engines.
27

Feasibility and Emissions of Compression Ignition Engines Fueled with Waste Vegetable Oil

Crawford, Morgan H 07 November 2003 (has links)
Research and experience has shown that vegetable oil can be processed, by transesterification, into a useable fuel for compression ignition engines. Earlier research examined using straight vegetable oil as a fuel, but found it to cause detrimental engine problems. Trial and error has shown that heating the vegetable oil prior to injection, is a viable option. A diesel vehicle engine was operated for over 188 hours or approximately 7,000 miles, using waste cooking oil as fuel. The longevity of the vehicle engine was limited by an undetermined engine failure. Using stationary testing, with no engine load and various power settings, engine emissions of several engines operating on waste cooking oil were compared to emissions from two other fuels, diesel and Biodiesel, and found to be very positive. Waste vegetable oil (WVO) had lower overall emissions than diesel and lower levels of nitrogen species than Biodiesel. Agricultural yield predictions estimate that currently only 5% and at most 20% of all diesel fuel needs can be met with vegetable oil. Currently WVO is a disposal problem. It is primarily used as a feedstock. WVO is not a commodity and has disposal fees associated with it. If WVO is used as a fuel, it would not only provide another source for disposal, but it may also increase the value of WVO making it a commodity instead of a disposal burden.
28

Comparison Of Engine Performance And Emissions For Conventional Petroleum Diesel Fuel And Diesel-ethanol Blends

Erkal, Gul 01 April 2010 (has links) (PDF)
Ethanol is an environmental friendly alternative diesel fuel that has received significant attention both as a possible renewable alternative fuel and as an additive to existing petroleum-based fuels. Beyond simply representing an additional fuel supply, ethanol exhibits several advantages when compared to existing petroleum fuel. The objective of this work is to investigate experimentally the effects of using different blends of specified percentages of ethanol on the engine performance and emissions and to compare it with that of conventional diesel fuel. Tests will be done on the &lsquo / &lsquo / Engine Test Laboratory&rsquo / &rsquo / of the Turkish Tractor Factory (TTF) using a fourcylinder, turbocharged and naturally aspirated, DI diesel engines. Engine performance parameters such as engine speed, torque, power, fuel consumption will be measured. At the same time, the engine emissions including particulate matter, unburned hydrocarbons, carbon monoxide, and NOX will also be recorded.
29

Helicopter Turboshaft Engine Ground Preformance With Alternative Fuels

Baslamisli, Ufuk 01 February 2012 (has links) (PDF)
In recent years, extensive studies on alternative fuels have been conducted to find environmentally friendly, economically feasible fuels due to finite petroleum sources, environmental and economical reasons. In this thesis, effects of alternative fuels on engine performance and exhaust emission are studied experimentally. Cold and reacting tests have been performed. Volumetric flow rate, discharge pressure are measured according to different pump speed. Droplet diameters, droplet distribution, spray cone angle and two dimensional velocity distribution from combustor fuel nozzle are determined by IPI and PIV technique. The comparative performance of alternative fuels and JET A-1 are investigated by atmospheric combustion tests and experimental turbojet tests in terms of exhaust gas temperatures, emissions, combustion chamber efficiency. Emissions, combustion chamber exit temperature profile, power turbine inlet and exhaust gas temperatures, effects of fuels on engine performance are observed and measured in detail at RR Allison 250 C-18 turbo-shaft engine.
30

The Initial Deployment of Electric Vehicle Service Equipment : Case study: Green Highway Region, E14 from Sundsvall in Sweden to Trondheim in Norway

Daniali, Iran January 2015 (has links)
Abstract Electric Vehicles (EVs) are considered a more sustainable alternative vehicle because of their efficient electric motor when compared to internal combustion engines (ICE), and thus help to mitigate environmental problems and reduce fossil fuel dependency. In or-der to support drivers of plug-in hybrid electrical vehicles (PEVs), the installation and adequate distribution of Electric Vehicle Service Equipment (EVSE) is a major factor. The availability of EVSE is a vital requirement in order to charge the vehicle’s battery pack through connection to the electricity grid. This thesis evaluates the likely distribu-tion of a sufficient number of charging stations, measured as the demand of EVSE, for initial deployment in the E14 highway. This highway is also known as the Green High-way region, where a plan has been outlined with the aim to create a fleet of 15% EVs in the area by 2020.In order to model EVSE distribution, the first step was to complete a survey in 2012 on the population density and location of cities, along with the location of already estab-lished charging station locations on the Green Highway. The survey was done with ge-ography information survey (GIS) software. The second step was to create a map of the region. Based on the map, the initial estimate of EVSE locations on the Green Highway project plan was analyzed, as the third step. This was used as an initial analysis. The forth step was to use the location of current gasoline stations to provide as alternative pattern for the EVSE sites.It was observed that the network of gasoline stations correlates positively with population density. Through using these stations, the optimal location of the EVSEs was proposed. However, the model results do not provide for sufficient placement of EVSE sites where the population density is very low. In order to assess the different potential options, it was necessary to create analytical models in Arc-GIS, in which buffer zones were created with a variable size of 10, 15, 20 and 31 miles. This permitted allocation of a geographical area to estimate the optimum sites for charging stations. The resultsiiishowed that for a buffer zone of 10 miles, 28 charging stations were calculated, using buffer zone of 15 miles gives 18 stations, and a buffer zone of 20 miles results in 13 charging station sites. Notably, the estimate of the 20-mile buffer zone gives the same results as for the 50 km (31 miles) buffer zone for residential areas along E14. Therefore, the results show that the optimal design is to deploy 14 fast charging stations with three-phase DC, or 14 fast charging stations with three-phase AC, installed adjacent to the E14 road.

Page generated in 0.0655 seconds