• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 30
  • 6
  • 5
  • 1
  • Tagged with
  • 45
  • 45
  • 45
  • 22
  • 22
  • 20
  • 18
  • 16
  • 15
  • 11
  • 10
  • 10
  • 9
  • 9
  • 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.
1

LIFE CYCLE ASSESSMENT OF HYDROGEN PRODUCTION FROM CANADIAN BIOMASS USING FORMIC ACID AS AN ENERGY CARRIER FOR TRANS-ATLANTIC ENERGY EXPORT

Tabari, Amir January 2024 (has links)
The importance of Hydrogen (H2) in current global energy systems is undeniable. Moving from the energy systems depending on fossil fuel to energy systems that are carbon-free is a necessity, thus solutions such as hydrogen economy is required. Especially after recent geopolitical challenges in Europe which could make the energy acquisition a crucial problem. Liquid organic hydrogen carriers (LOHC) are applicable pathways for transitioning H2 into energy and to avoid the storage and transportation limitations of gaseous and liquid H2. Formic acid (FA) is an attractive alternative for such purposes due to its minimal level of toxicity and its significant volumetric storage capacity for H2. In this study, a Life cycle assessment (LCA) of the supply chain involving the Trans-Atlantic export of energy from Canada to Germany is conducted using formic acid as a LOHC and OxFA process to convert biomass to formic acid. The environmental impacts of all units and processes involved in this supply chain are examined, and the results are compared against other traditional systems for hydrogen production. A sensitivity analysis was also performed to recognize the crucial contributors and assess the processes and units that impose considerable influence on the overall environmental impact. / Thesis / Master of Applied Science (MASc) / Hydrogen (H2) plays a crucial role in transitioning from fossil fuel-based to carbon-free energy systems, a shift highlighted by recent geopolitical challenges in Europe. Liquid organic hydrogen carriers (LOHC) offer a solution for hydrogen storage and transport issues associated with its gaseous and liquid states. Formic acid (FA) is particularly promising as a LOHC due to its low toxicity and high hydrogen storage capacity. This study conducts a Life Cycle Assessment (LCA) of a supply chain that uses formic acid to export energy from Canada to Germany, involving the OxFA process for converting biomass to formic acid. The environmental impacts of all processes in this supply chain are evaluated and compared with traditional hydrogen production methods. Additionally, a sensitivity analysis identifies key contributors and assesses their impact on the overall environmental footprint.
2

Kinetics and Atmospheric Chemistry Studies of Halogenated Species

Sapkota, Ramesh 12 1900 (has links)
Quantitative information about halogenated hydrocarbons is important for understanding their impact on atmospheric ozone chemistry and climate change, their regulation, and the devising of improved substitutes. The Montreal Protocol aimed to regulate the utilization and manufacturing of hydrochlorofluorocarbon compounds (HCFCs), contributing to ozone layer depletion. The 2016 Kigali Amendment to the Montreal Protocol agreement, Annex C listed 274 HCFCs. Only 16 of them have been measured experimentally. The rest were set to zero by default. These reported global warming potentials (GWPs) play a crucial role in formulating policies for gradually reducing the usage and production of HCFCs to prevent atmospheric impact. Here we are studying 1-chloro-1-fluoro-ethane (CH3CHFCl) as a test of past theory. There are no prior experimental measurements of the reactivity of CH3CHFCl with hydroxyl (OH) radicals, which primarily determines its atmospheric lifetime, nor of its infrared (IR) spectrum. Saturated hydrofluorocarbons (HFCs) are non-ozone depleting substitutes for chlorofluorocarbons deprecated under the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer, but they exhibit high global warming potentials (GWPs) and the Kigali Amendment adopted in 2016 outlines their phase down. Unsaturated HFCs offer more reactive alternatives, whose likely short atmospheric lifetimes would imply small GWPs. Because their GWPs are smaller than those for saturated HFCs by several orders of magnitude, and especially for fully fluorinated examples, several halogenated olefins are under consideration for practical application. We studied HCF2CF2CF=CF2, cis-HCF=HCF, trans HCF=HCF, CF2=CH2 unsaturated HFCs.
3

Livscykelanalys: Förbränning av hushållsavfall kontra biogas : miljömässiga och ekonomiska perspektiv med utgångspunkt i Oskarshamns kommun

Gunnarsson, Helene January 2013 (has links)
Är det möjligt att reducera utsläppen av växthusgaser och samtidigt nå en hållbar utveckling? Regionförbundet i Kalmar län antog utmaningen 2006 och är därmed en föregångsregion i arbetet med detta. Till år 2030 är målet att Kalmar län ska bli en fossilbränslefri region. Den största potentialen anses finnas inom nya alternativ till fordonsbränsle. Hushållens sopor innehåller organiskt matavfall som skulle kunna bli fordonsgas. Allt fler biogasmackar öppnas och gasen har vunnit framgång i takt med att kollektivtrafiken gjort satsningar. I Oskarshamns kommun sker i dagsläget ingen utsortering av organiskt matavfall. Hushållsavfallet skickas tillsammans med det organiska matavfallet till förbränning med energiutvinning i Linköping. Syftet med min studie är att göra en utvärdering av miljöpåverkan utifrån två scenarier; förbränning av allt hushållavfall jämfört med att producera biogas av matavfallet och förbränna resterande. Detta sett utifrån potentialen för området i Oskarshamns kommun. Syftet är även att titta på ekonomiska aspekter. Detta är en livscykelanalys där två metoder har använts, Global Warming Potential med ett 100 års perspektiv samt ReCiPe Endpoint. Den funktionella enheten är 1 ton hushållsavfall. Genom att röta det organiska hushållsavfallet och förbränna det övriga kan man minska miljöpåverkan till 74,6 % jämfört med att förbränna allt tillsammans. Växthusgaserna minskar då med 780 kg koldioxidekvivalenter per ton hushållsavfall. Den främsta miljövinsten blir i form av minskande klimatförändringar men att det fordrar ganska omfattande ekonomiska investeringar. / Is it possible to reduce greenhouse gas emissions while achieving sustainable development? The Regional Council in Kalmar County accepted the challenge in 2006 and is thus a leading region in this work. By 2030, the goal is that Kalmar shall become a fossil fuel free region. The greatest potential is considered to be the new alternative to vehicle fuel. Household waste includes organic waste that could become fuel for vehicles. An increasing number of biogas stations have opened and the gas has been successful as the public transports have made investments. In Oskarshamn is there no current sorting of organic waste. Household waste is sent along with the organic food waste to incineration with energy recovery in Linköping. The purpose of my study is to evaluate the environmental impact based on two scenarios: the burning of all household waste compared to producing biogas from food waste and burn the remaining. This is seen by the potential of the area in Oskarshamn. Also examining the economic perspective there is. This is a LCA where two methods were used, the Global Warming Potential with a 100-year perspective and ReCiPe Endpoint. The functional unit is 1 ton of waste. By digesting the organic waste and burning the rest, one can reduce the environmental impact to 74, 6 % compared to burning it all. The greenhouse gases then will decrease by 780 kg carbon dioxide equivalent per ton household waste. The main environmental benefits are in terms of reducing climate change, but it requires quite a significant financial investment
4

An energy efficient mass transportation model for Gauteng / Kadri Middlekoop Nassiep

Nassiep, Kadri Middlekoop January 2011 (has links)
The demand for forensic social work as a specialist field is increasing rapidly, due to the increasing moral decline of the community and consequent higher demands set to generic social workers. Amendments to existing acts as well as the development of new legislation, lead to more opportunity for the prosecution of the perpetrator, and therefore a higher utilization of the forensic social worker. A need was experienced to do research regarding the gaps experienced by social workers or any other workers who are currently executing forensic assessments with the sexually traumatised child. The aim of the investigation was to determine which gaps social workers experience in the field when assessing a child forensically. A recording procedure was used to obtain qualitative as well as quantitative data. A purposive sampling was used were interviews were held with five participants to obtain the data. A selfdeveloped questionnaire was used as measuring instrument. It is clear from the findings that there are definite gaps within the field of forensic social work and the need of further research within the field of forensic social work in South Africa is highlighted. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2012.
5

An energy efficient mass transportation model for Gauteng / Kadri Middlekoop Nassiep

Nassiep, Kadri Middlekoop January 2011 (has links)
The demand for forensic social work as a specialist field is increasing rapidly, due to the increasing moral decline of the community and consequent higher demands set to generic social workers. Amendments to existing acts as well as the development of new legislation, lead to more opportunity for the prosecution of the perpetrator, and therefore a higher utilization of the forensic social worker. A need was experienced to do research regarding the gaps experienced by social workers or any other workers who are currently executing forensic assessments with the sexually traumatised child. The aim of the investigation was to determine which gaps social workers experience in the field when assessing a child forensically. A recording procedure was used to obtain qualitative as well as quantitative data. A purposive sampling was used were interviews were held with five participants to obtain the data. A selfdeveloped questionnaire was used as measuring instrument. It is clear from the findings that there are definite gaps within the field of forensic social work and the need of further research within the field of forensic social work in South Africa is highlighted. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2012.
6

Environmental and health impacts when replacing kerosene lamps with solar lanterns : A study on global warming potential and household air pollution

Stenemo, Erik, Olsson, Emma January 2018 (has links)
In regions with low energy access kerosene lamps are commonly used, and these emit carbon dioxide (CO2) as well as household air pollutants (HAP). This bachelor thesis examines the possible reduction of carbon dioxide equivalents (CO2eq) emissions and HAP from kerosene lamps by replacing them with off-grid solar powered lanterns. Life cycle assessment, or LCA, is used as a method to assess CO2eq emissions from the solar lanterns. Data on emissions from the different stages in the solar lantern lifecycle, as well as for the kerosene lamps, is gathered through literature studies. Furthermore, possible improvements of health and social aspects as result of replacing kerosene lamps are studied and discussed. The results show that CO2eq emissions could be significantly lower if solar lanterns were used. During a lifetime of 30 years, a simple kerosene lamp emits a total of 15 500 kg CO2eq, a hurricane lantern 7 900 kg CO2eq, whereas a solar lantern emits 66.1 kg CO2eq. However, it is found that the possible harmful effects of HAP are much larger than those of CO2. Finally, possibilities and challenges regarding implementation and usage of off-grid solar powered lanterns are identified and discussed.
7

Design of a low carbon building : Case study of an architectural competition

Uzan, Sacha January 2019 (has links)
Greenhouse gases (GHGs) emissions due to human activities have considerably increased in the past decades which are the main contributors of global warming. In order to limit the consequences of the global climate change happening, all sectors must reduce their carbon emissions and especially the building industry which represents 19% of the carbon footprint of human activities. This paper is giving methods to help reduce the carbon footprint of a building when designing it such as life cycle assessment which allow project teams to compare the global warming potential of all building materials. Those methods are used and challenged in a case study of an architectural competition project named quai d’Issy in Paris, France. Using biobased materials help reduce the carbon footprint of a building, a structure made of timber and concrete elements can emit less than 21% of GHGs than a classic concrete structure. By sourcing reused and recycled building materials, by using geothermal heat pump as heating and cooling systems for example, we have been able to reach for the quai d’Issy project a carbon footprint of 930kgC02eq/m2 of floor area, which is less than level needed for the highest French environmental certification. However, these results can be obtained only if the building materials companies continue their work to develop low-carbon materials and promote recycled and reused materials. This study emphasises the need to spread knowledge of the tools to design low-carbon building to all the actors of the building industry in order to promote behaviours that will limit the consequences of climate change.
8

Leisure, well-being, and sustainable lifestyles : A study to explore relationships between leisure activities and global warming potential in Sweden.

Högberg, Anna, Guardini, Beatrice January 2023 (has links)
Studies show that leisure activities can contribute significantly to people’s well-being. Still, theycan also impact the environment in several ways as they contribute to greenhouse gas emissionsrelated to different factors. When modifying lifestyles towards more sustainable behaviors, peoplecan sometimes expect reductions in their well-being, but this relationship is not much exploredfor what concerns the activities that people engage in within their free time. By further exploringthis literature gap, this study research leisure activities - namely those activities when theindividuals have the most control over their chances of action - as a potential pathway forimplementing more sustainable behaviors in an individual lifestyle that can also improve one’sown well-being. By employing questionnaires and a life cycle assessment approach – the aim is todescribe i) what leisure activities people in Sweden engage with to promote their well-being, ii)what are the most important ones and the main benefits obtained from them, and iii) what impact,in terms of greenhouse gas emissions, these activities have on the climate. The results show thatsome common leisure activity types are important for Swedes to maintain their well-being. Thesecan have different environmental impacts in terms of greenhouse gas emissions depending onactivity-related factors such as location, frequency, and equipment and material resources utilizedduring the activity. We conclude that leisure activities that people consider more important fortheir well-being are also those that could potentially have the lowest impact in terms of greenhousegas emissions and that more quantitative studies could explore this relation further.
9

Potential of local producing bioenergy/biogas from waste in the municipality of Ragunda

Hayes, Tomás January 2023 (has links)
Population growth, climate change and increased global energy demand has led to the search for environment friendly energy sources. Ragunda Municipality’s major producers of Greenhouse Gas (GHG) emissions are transport, agriculture, and work machines. This research is motivated by a goal set by Ragunda Municipality to produce 15% of their own energy consumption and wider regional goal of reducing GHG emissions by 10% year on year to towards 2030. The study explores the potential for using bioenergy/biogas and climatic effects of its local production in Ragunda from agriculture, forestry, food, municipal, and sewage waste for one year. The method calculated tonne of waste, energy production in MWh, biogas volumes in Nm3 and climate impact of the bioenergy as carbon dioxide equivalents (CO2-eq). The study showed total local bioenergy production from waste materials for Ragunda of 58 092 MWh/year, total biogas production from waste materials for Ragunda of 427 079 Nm3/year. The study also concluded that best use of biogas from a climate impact perspective was to upgrade it to vehicle fuels to offset fossil fuel in the transport sector. The potential for local production of bioenergy/biogas in Ragunda was shown to be financially feasible provided investment aid and subsidies are granted in the case of biogas production. / <p>2023-06-02</p>
10

Flow boiling of ammonia and propane in mini channels

Maqbool, Muhammad Hamayun January 2012 (has links)
The environmental concerns in recent times have grown especially after signing Montreal protocol. In the last ten years, researchers have focussed mainly on understanding the boiling and condensation phenomena of HFC refrigerants in minichannels. As global warming concerns are growing day by day, due to high global warming potential, HFCs are not the ultimate option. In the near future, HFCs will probably be replaced by environmentally friendly refrigerants. Therefore, to find the potential replacements of HFCs and also to get a deeper understanding of the boiling phenomena in minichannels, more and more fluids having low GWP (Global Warming Potential) and ODP (Ozone Depletion Potential) should be tested. Recent efforts to protect the environment have led to a growing interest for natural refrigerants. However in the literature, flow boiling data of natural refrigerants in minichannels are scarce. To meet the environmental concerns and to understand the behaviour of natural refrigerants in minichannels and the performance compared to HFCs, flow boiling experiments in single circular vertical minichannels of internal diameters of 1.70 and 1.224 mm were performed using ammonia and propane as working fluids. Flow boiling heat transfer results of ammonia and propane with 1.70 mm channel showed that the heat transfer coefficient was a function of heat flux and the effect of mass flux was insignificant. The heat transfer coefficient of ammonia in 1.224 mm was dependent on heat flux at low vapour qualities then a clear dependence of the heat transfer coefficient on the mass flux was observed at higher vapour qualities. The heat transfer results of ammonia and propane were compared with well known correlations and among them Cooper (1989) correlation in case of ammonia and Liu and Winterton (1991) and Cooper (1984) pool boiling correlations in case of propane best predicted the experimental heat transfer data. Results of the two phase pressure drop studies of ammonia and propane showed that the two phase pressure drop increased with the increase of mass flux, with the increase of heat flux and with the decrease of saturation temperature. The comparison of the two phase pressure drop experimental data with well known predicting models showed that none of the correlations predicted the ammonia data well and that Müller Steinhagen and Heck (1986) was well in agreement with the propane data. Dryout of propane in 1.70 mm and 1.224 mm internal diameter channels was also investigated. Dryout heat flux was observed to increase with the increase of mass flux, with the decrease of vapour quality and with the increase of internal diameter. The effect of saturation temperature on the dryout heat flux was insignificant. The experimental dryout data were compared with macro and micro scale correlations and among them Bowring (1972) and Callizo et al. (2010a) gave best predictions. The heat transfer and pressure drop results of ammonia and propane and dryout results of propane were compared with R134a data taken on the same test rig by Owhaib (2007) and Ali (2010). The comparison of heat transfer showed that the heat transfer coefficient was a function of heat flux and the effect of mass flux was insignificant in all tested conditions except ammonia in 1.224 mm tube where the heat transfer coefficient was dependent on heat flux at lower vapour qualities and a clear dependence of mass flux was observed at higher vapour qualities. The heat transfer data of ammonia, propane and R134a were compared with correlations and among them Cooper (1989) correlation gave best predictions. The comparison of pressure drop results showed that the two phase pressure drop of all fluids was increased with the increase of mass flux, with the increase of heat flux and with the decrease of saturation temperature. At equal heat flux and mass flux, the two phase pressure drop of ammonia was increased with the decrease of internal diameter but the diametric effects of R134a were unclear. Müller Steinhagen and Heck (1986) and Zhang and Webb (2001) best predicted the experimental data of two phase pressure drop of ammonia, propane and R134a among the correlations considered for comparison. The dryout data of propane were also compared with dryout data of R134a and it was observed that the dryout heat flux of propane and R134a increased with the increase of mass flux, with the decrease of vapour quality and with the increase of internal diameter. The effect of saturation temperature on the dryout heat flux of propane and R134a was insignificant. The correlation of Bowring (1972) for conventional channels and the microscale correlation of Callizo et al. (2010a) were among the correlations which gave best predictions of experimental data of dryout. / QC 20120210

Page generated in 0.1238 seconds