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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

Life cycle assessment of composites and aluminium use in aircraft systems

Liu, Ziqian 10 1900 (has links)
As a consequence of the gradually expanding aviation network, civil aircrafts are occupying an increasingly high proportion of the transport industry. Air transport now dominates the intercity rapid transit, long-distance passenger transport, international passenger and freight transport, and specific regional transport, advantaged as it is by fast, convenient, comfortable and safe options. Nevertheless, the potential adverse impact on the environment of air transport, specifically, in the case of this research, the pollutants generated during aircraft production remain a concern. Using the A319 as the main research object, this thesis will conduct a life cycle assessment research about its environmental impact. Moreover, it will focus on the impact brought by the application of composite materials to the entire life cycle environmental influence of the aircraft, particularly the material production and disposal process. At the same time, a contrast with the B737-800 aircraft will be made due to their different composite material use rate. Firstly, the inventory list is formed by collecting data about the weight and material of every component in the aircraft, the input and output information of the composite material manufacturing process, the disposal situation of the aircraft and the treatment of composite material. Secondly, the impact assessment of the aircraft is conducted to examine their environmental influence. During the assessment, each life stage and the whole life cycle of the aircrafts is assessed, and a comparison between these two aircraft types is made. Finally, according to the impact assessment result, the environment load increase brought by the manufacturing of composite material and the decrease of the environment impact due to the weight reduction character of composite material is calculated and compared. From this research, the conclusion that the use of composite material has a positive effect on decreasing the environmental impact of the whole life cycle of the aircraft is obtained. This will enable aircraft manufacturers to target these reas for improvement, to produce more comfortable, environment friendly and market competitive aircraft.
2

Life cycle assessment of hybrid systems for rural electrification in Bolivia / Livscykelanalys av hybridsystem för elektrifiering av landsbygden i Bolivi

Seres, Sandu January 2021 (has links)
Bolivia is a developing country in South America. Many rural communities still lack access to electricity. The extension of the National Grid System to all rural communities is not feasible due to economic and topographic challenges as well as the environmental problems that may arise. To tackle these problems, Off-grid solutions are implemented. Photovoltaic (PV) panels combined with batteries are a viable option for areas located close to the equator and high altitudes such as Bolivia. Almost always a controlled source of energy such as Diesel generators must complement the PV system due to the stochastic nature of solar energy. The use of fossil fuel can be detrimental to the environment and more environmentally friendly solutions are being investigated. The use of wood pellets in Stirling engines is a viable replacement for Diesel generators.  The purpose of this study is to investigate and compare the environmental impacts caused by two Off-grid hybrid systems. The first one is composed of a Diesel generator, PV panels, and batteries. The second one is composed of a Stirling engine, PV panels, and batteries. The study area chosen for this work is the community El Carmen, Pando, in Bolivia. A Life Cycle Assessment (LCA) model is carried out for the systems according to the 4 phases of the LCA methodology. First, individual LCA models for all midpoint impact categories are generated. Secondly, a comparative LCA between the two systems, both at midpoint and endpoint, is created. Finally, a sensitivity analysis is conducted to determine the robustness of the models.  The individual midpoint analysis of both systems showed that the controlled part of the electricity production (i.e., the Diesel generator and the Stirling engine) generated the greatest impact in the categories Global warming, Stratospheric ozone depletion, Ionizing radiation, Ozone formation, Fine particulate matter formation, Terrestrial acidification, Human carcinogenic toxicity, Land use, Fossil fuel scarcity, and Water consumption. All the processes related to the PV panels generated a greater impact in all Ecotoxicity categories (terrestrial, marine, and freshwater), Eutrophication (freshwater and marine), and Human non-carcinogenic toxicity.  The midpoint results of the comparative LCA are inconclusive. Each system received higher scores in certain categories and lower scores in others. No firm conclusion could be drawn regarding the identification of the more environmentally friendly alternative. The Diesel/PV/Batteries system dominated the Global warming, Tropospheric ozone formation, Fine particulate matter formation, Terrestrial acidification, and Fossil resource scarcity categories. The Stirling/PV/Batteries system showed a greater impact on Stratospheric ozone depletion, Ecotoxicity, Eutrophication, Human carcinogenic toxicity, Human non- carcinogenic toxicity, and Mineral resource scarcity.  The endpoint damage assessment showed that the emissions and midpoint categories described had a greater impact on Human health and Resource scarcity in the case of the Diesel/PV/Batteries system. On the other hand, the Stirling/PV/Batteries system caused greater damage to the Ecosystem category.  The sensitivity analysis was conducted in two scenarios for each system. In the first scenario, alteration of fuel transport distance, no significant changes were detected in all endpoint categories. In the second scenario, alteration of Diesel/Stirling Contribution, the model showed an increasing trend (~30% for the first system and ~25% for the second one) in all categories when the contribution of the controlled part of the electricity production was increased. / Bolivia är ett utvecklingsland i Sydamerika där många landsbygdssamhällen fortfarande saknar tillgång till elektricitet. En anslutning till det nationella kraftsystemet är inte genomförbar på grund av de ekonomiska och topografiska svårigheterna samt miljöproblemen som kan uppstå. För att ta itu med problemet måste decentraliserade lösningar hittas. Solcellspaneler i kombination med batterier utgör ett möjligt alternativ för avlägsna områden som befinner sig nära ekvatorn och vid höga höjder. Ett sådant system behöver dock ytterligare en kontrollerad energikälla för att tillgodose efterfrågan på grund av den ojämna tillgången på solenergi. Det vanligaste alternativet är dieselgeneratorer. Men förbränning av fossila bränslen påverkar klimatet och mer miljövänliga lösningar undersöks. Stirlingmotorer som använder träpellets skulle kunna ersätta dieselgeneratorn i kampen för en bättre miljö.  Syftet med denna studie är att undersöka och jämföra miljöpåverkan av två hybridsystem. Det ena systemet består av en dieselgenerator, PV-paneler och batterier medan det andra systemet består av en Stirlingmotor, PV-paneler och batterier. Det utvalda studieområdet är samhället El Carmen, Pando, i Bolivia. En livscykelanalys (LCA) utförs för de två systemen enligt LCA-metodiken. Först, utförs individuella LCA för vardera system för alla påverkanskategorier vid midpoint. Sedan utförs en jämförande LCA mellan de två systemen för alla påverkanskategorier både vid midpoint och endpoint. Slutligen, utförs en känslighetsanalys för att testa systemens robusthet.  Den individuella analysen vid midpoint för båda systemen påvisade att den kontrollerade delen av elproduktion, det vill säga dieselgeneratorn och Stirlingmotorn, genererade den största miljöpåverkan i kategorierna Global uppvärmning, Uttunning av ozonskiktet, Joniserande strålning, Bildning av marknära ozon, Bildning av partiklar, Försurning, Cancerframkallande humantoxicitet, Landanvändning, Brist på fossila resurser och Vattenförbrukning. Alla processerna kopplade till PV-elproduktionen genererade en större miljöpåverkan i kategorierna Ecotoxicitet (mark, söt- och havsvatten), Övergödning (såväl söt- som havsvatten) och Icke cancerframkallande humantoxicitet.  Resultaten vid midpoint för den jämförande LCA är inte övertygande. Vardera system fick högre poäng i vissa kategorier men lägre poäng i andra. Ingen tydlig slutsats kunde dras angående identifieringen av det mer miljövänliga alternativet. Diesel/PV/Batteri-systemet dominerar kategorierna Global uppvärmning, Bildning av marknära ozon, Bildning av partiklar, Försurning och Brist på fossila bränslen medan Stirling/PV/Batteri-systemet påvisade större miljöpåverkan i kategorierna Uttunning av ozonskiktet, Ekotoxicitet, Övergödning, Cancerframkallande humantoxicitet och Brist på mineraltillgångar.  Skadebedömningen vid endpoint påvisade att de redovisade utsläppen och midpoint- katergorierna har en större påverkan på människors hälsa och resursbrist i Diesel/PV/Batteris fall. Däremot påvisade det Stirling/PV/Batteri-systemet en större påverkan på ekosystemet.  Känslighetsanalysen utfördes i två scenarier. I det första scenariot ändrades avståndet för bränsletransport. Ingen signifikant skillnad påvisades i någon av de tre endpoint- kategorierna. I det andra scenariot, Diesel/Stirling insats, påvisades en ökande trend (~30% för första systemet och ~25% för det andra) i alla endpoint-kategorier med ökandet av insatsen från den kontrollade delen av elproduktion.
3

Hodnocení přírodních a recyklovaných surovin a materiálů v budovách / Assessment of natural and recycled materials in buildings

Stránská, Zuzana January 2018 (has links)
Life-Cycle Assessment (LCA) is an analytic method for evaluation of environmental impacts of products, services and technologies. It is associated with all the stages of a product's life. The environmental impacts are evaluated on the basis of material and energetic flows, which are in influence with the environment. These impacts are always determined in the relation with the function of the product or the service and so it is possible to compare them with the other alternatives. One of the most important reasons why I have chosen this dissertation thesis subject was the growing public interest in impacts of the building constructions on the environment and human organism. Only a few experts and scientific research centres deal with the problem of environmental impacts of the buildings in the Czech Republic so the main goal of this thesis is to help with a spreading a knowledge about it. There are four main problems to solve in the thesis: determination of environmental impacts of selected materials which are missing in available databases, creation of life cycle models of evaluated buildings, determining the most appropriate functional unit and determining the contents of the recommended LCA protocol for building analysis. In the first phase of the thesis there was built a detailed life cycle model of the reference building on the basis of available documents and databases. This "cradle to cradle" LCA model was then optimized for a large number of life cycle scenarios to determine the significance of the impact of individual variables on the overall environmental impact of the building. The knowledge gained from this analysis was applied to the lifecycle models of other buildings and then there was assembled the recommended form of the LCA protocol. In the final stage, the results of the environmental impacts were quantified on the different functional units which were used for determining the appropriate form.

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