• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 87
  • 39
  • 10
  • 9
  • 6
  • 3
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 178
  • 178
  • 62
  • 32
  • 28
  • 17
  • 17
  • 16
  • 16
  • 15
  • 15
  • 15
  • 14
  • 14
  • 14
  • 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.
91

Maximizing Environmental Sustainability and Public Benefits of Highway Construction Programs

Limsawasd, Charinee 24 March 2016 (has links)
Transportation agencies face a challenging task to repair damaged roads in an aging transportation network with limited funding. In addition, the funding gap is forecasted to continue widening, which has direct impacts on the performance of surface transportation networks and the nation’s economy in the long run. Recently, transportation agencies were required by a newly enacted law to include national performance-based goals, such as environmental sustainability, in their programming and planning efforts for highway repair and rehabilitation. Therefore, the current practice in the area of highway rehabilitation planning is inadequate to handle this task and new practices are needed to improve the performance of transportation networks while maintain the national goal of maximizing environmental sustainability. Accordingly, this dissertation presents an innovative environmental-based decision-support model for planning highway construction programs. The model is developed in three main parts that are designed to: (1) model total vehicle fuel consumption and public benefits/costs of traveling on transportation networks; (2) evaluate the economic and environmental impacts of highway rehabilitation efforts; and (3) develop a multi-objective optimization model to identify and evaluate highway rehabilitation program(s) that are capable of simultaneously minimizing environmental impact and maximizing public benefits of rehabilitation decisions. First, mathematical models were developed to facilitate estimating the total vehicle fuel consumption and public benefits/cost for road users at the network-level. These models are deigned to estimate vehicle fuel consumption rate, tire depreciation cost, and vehicle repair and maintenance cost rate, in terms of major vehicle–road interaction factors, such as vehicle type, speed, and pavement conditions. The developed and statistically validated models are then used to estimate total vehicle fuel consumption and public benefits/costs at the network-level. Second, a new model was developed for evaluating the impact of decision making in highway rehabilitation efforts on greenhouse gas emissions and public travel costs. The model has the capabilities of: (1) identifying candidate rehabilitation treatment alternatives for damaged or aging pavement; (2) evaluating the impact of these treatments on pavement performance; (3) estimating network fuel consumption due to highway rehabilitation decisions; (4) estimating additional public costs as a result of travel-delay during road construction operations; and (5) evaluating the impact of rehabilitation efforts on public benefits expressed as expected savings in road user costs. Third, a multi-objective optimization model was developed to search for and identify highway rehabilitation programs that are capable of minimizing environmental impact in terms of CO2 emissions while maximizing public benefits under budget constraints. This newly developed model enables planners and decision makers to design and implement highway rehabilitation programs that are cost-effective and environmentally-conscious.
92

Omezování emisí CO2 v letecké dopravě / Reducing CO2 Emission in Air Transport

Fričová, Barbora January 2014 (has links)
Reducing CO2 emission in air transport is the main theme of this master´s thesis. As the public interest in aviation and climate change is world´s growing it could be consider as a hot topic. As a response to public interest was the creation of contracts, standards and limits of carbon dioxide emissions. The master´s thesis is divided into several parts. The first is mapping of global air traffic and carbon dioxide emissions. The second part deals with European approach to solving problems of reducing CO2 emissions follows by description of ICAO Aeroplane CO2 emissions standard. The part of the thesis is the overview of the use of biofuels in aviation and their price. The conclusion summarizes all knowledge learned while working on this thesis.
93

Gestaltung eines alltagstauglichen Hocheffizienz-Konzeptfahrzeugs

Eiletz, Richard, Block, Enno, Warkotsch, Christoph, Post, Klaus January 2016 (has links)
Die anspruchsvollen Zielsetzungen zum CO2-Ausstoß von Kraftfahrzeugen verlangen immer stärker nach hocheffizienten Fahrzeugkonzepten und werden zukünftig zu deutlich höheren Elektrifizierungsanteilen der Antriebe führen. Die große Herausforderung liegt dabei in der Lösung des Zielkonfliktes zwischen voll elektrischem Fahren und erstfahrzeugtauglicher Reichweite. Im Rahmen eines Forschungsprojektes zur Konzeption von Hybridfahrzeugen hat die BMW Forschung ein Konzeptfahrzeug entwickelt, das im urbanen Bereich emissionsfrei betrieben werden kann und dennoch alltagstauglich für spontane längere Fahrten nutzbar ist (Abbildung 1). Die für dieses Projekt abgeleiteten Ziele waren ein Verbrauch von < 2,5 l im Ladungserhaltungsbetrieb, eine E-Reichweite von 100 km, eine BMW-adäquate Beschleunigung von < 8 sec von 0 auf 100 km/h, eine erstfahrzeugtaugliche Höchstgeschwindigkeit von 180 km/h, ein Raumangebot auf Niveau heutiger viersitziger Coupés im Kompaktsegment und eine Gesamtreichweite von 1.000 km (Eiletz 2015a). Im Rahmen des Beitrags werden sowohl Prozess und Vorgehensweise bei der Gestaltung des Hocheffizienz-Konzeptfahrzeugs als auch die Ergebnisse des Forschungsprojektes dargelegt.
94

Impact on heat rate and subsequent emissions due to varying operation of coal fired power plants

Akpan, Patrick Udeme-Obong 21 April 2020 (has links)
Energy mix modellers often use a constant emissions factor model, which more or less implies a constant heat rate, when trying to show the emissions reduction benefits of integrating renewable power generation system on the grid. This approach does not consider the fact that there is a deterioration in the heat rate with load for the Coal Fired Power Plants that need to accommodate the additional renewable supply. If varying heat rate were to be included in a study, it is often limited to plant specific cases. This PhD presents a novel Variable Turbine Cycle Heat Rate (V-TCHR) model for predicting the part load Turbine cycle heat rate (TCHR) response of various Coal Fired Power Plant (CFPP) architectures, without detail knowledge of the entire steam cycle parameters. A total of 192 process models of representative CFPP architectures were developed using a Virtual Plant software. The models had different combinations of the degree of reheat; the throttle temperature; throttle pressure; and condenser cooling technology. The part load response of all the models were simulated using the software.
95

CO2 Emissions from Freight Transport and the Impact of Supply Chain Management : A case study at Atlas Copco Industrial Technique

Jofred, Petter, Öster, Peder January 2011 (has links)
Freight transport is a large contributor to emissions of CO2 and to mitigate its environmental impact is essential in strive for a sustainable future. Existing reports usually discuss the issues from a national or global perspective, but rarely provide any concrete or practical information on an organizational level. This report aims to describe the key driving factors of CO2 emissions caused by freight transport and recommend suitable measures for organizations to mitigate their environmental impact. To do this, a case study at Atlas Copco’s business area Industrial Technique (ITBA) is performed, four different business scenarios are created and the emissions from the scenarios are simulated. ITBA is a decentralized organization with most of the production sites and sub suppliers in Europe. Over 90% of the finished goods are sent to a distribution center in Belgium and then delivered to the customers. Today, most customers are located in Europe and this market accounts for nearly 80% of the distributed weight. However, ITBA believe in a strong growth in the North American and Asian markets and that the customer base will look much different in 2020. More customers at longer distances from the distribution center will lead to a heavily increased use of air freight, resulting in higher emission levels. This study shows a clear correlation between the total CO2 emissions and the share of air freight. In order for ITBA to expand their business and at the same time lower their emissions, actions are required. This report shows that a lower share of air freight and the use of several decentralized distribution centers can reduce the emissions significantly. Other means to lower the emissions include relocation of production sites, education to increase the awareness within the organization and including environmental performance when evaluating third party logistics.
96

Thermal rehabilitation of Romanian housing: a low cost assessment tool

Cobirzan, N., Oltean-Dumbrava, Crina, Brumaru, M. January 2012 (has links)
The numerous buildings that currently require thermal rehabilitation in Romania means that substantial resources and a large number of competent people are required to carry out surveys and energy audits. However, commercial energy balance software is mostly unaffordable for those organisations involved in this process. This paper describes an energy balance programme – ENEFControl – developed to be a rapid, low cost, local tool able to assist in the choice of energy efficient solutions for buildings. To test the software, thermal and energy analyses were carried out on a 1970s built apartment block in Transylvania. Based on these analyses, three constructive scenarios were proposed for thermal rehabilitation. Compared to the performance of the analysed building, the thermal and energy performance of the retrofitted building in all three scenarios significantly improved. Since European Union accession in 2007, rapidly rising energy costs have affected the Romanian population. ENEFControl offers Romanian engineers and architects an opportunity to speed up the rehabilitation programme of buildings without the need for more expensive expertise and tools.
97

Minskat CO2 avtryck i råstål genom en ökad andel skrot i konvertern / Reduced carbon footprint in crude steel by increased scrap ratio in converter

Karlström, Elin January 2023 (has links)
Stålindustrin är kraftigt energi och utsläppsintensiv och står för upp till cirka 7% av de globala 𝐶𝑂2-utsläppen. Den huvudsakliga utsläppskällan utgörs av masugnsprocessen där järnmalm reduceras till råjärn med hjälp av fossilt kol i den malmbaserade processvägen. Flera tidigare studier har visat att den mest effektiva metoden för att minska industrins utsläpp av 𝐶𝑂2 och därmed bidrag till klimatförändringar är att öka andelen skrot i kolfärskningsprocessen för att på så sätt minska behovet av råjärn.  Syftet med studien var att undersöka möjligheterna att minska stålindustrins utsläpp av 𝐶𝑂2 genom en ökad andel skrot i kolfärskningsprocessen. Rapporten delades upp i två delar, inledningsvis en litteraturstudie som ge en bild över vilka metoder som finns tillgängliga samt vilken potentiell effekt dessa har. Den andra delen baserades på analyser av produktionsdata från SSAB Oxelösund. Tillsammans med resultatet från litteraturstudien användes analyserna för att ta reda på hur mycket råstålets 𝐶𝑂2-avtryck skulle kunna minskas med användning av metoder relevanta för det specifika stålverkets förutsättningar, förbättringsområden och framtida planer.  Parametrarna som undersöktes utgjordes av effekt på skrotinsmältning samt övriga utmaningar och fördelar kopplat till industrins klimatpåverkan. Resultatet från litteraturstudien visade att det fanns ett flertal effektiva metoder för att öka skrotinsmältningskapaciteten i kolfärskningsprocessen och att dessa vid kombinerad användning har en addidativ effekt och har potential att höja skrotinsmältningen avsevärt. Effekten av dessa är dock till stor del beroende på utgångspunkt och produktionsspecifika förutsättningar och måste undersökas vidare genom exempelvis industriförsök.  Eftersom stålverket ställer om produktionen till 2026 kan inte några större investeringar för att minska utsläppen från den äldre produktionen anses vara motiverbar både gällande utsläpp av 𝐶𝑂2 och investeringskostnad. Analyserna av produktionsdata tillsammans med resultatet från litteraturstudierna visade att det fanns flera förbättringsområden och rimliga metoder för stålverket att öka sin skrotinsmältning med syfte att minska utsläppen av 𝐶𝑂2. Genom implementering av dessa metoder som skulle skrotinsmältningen kunna ökas med 2,3 % vilket skulle resultera i en relativ minskning av råstålets 𝐶𝑂2-avtryck med 2,8%.
98

Greenhouse gas emissions and energy efficiency of various renewable energy pathways in the truck industry : An LCA and energy efficiency analysis on fuel production for and manufacturing of 40 tonne heavy trucks in Sweden

Axell, Jacob January 2023 (has links)
This study focuses on assessing the greenhouse gas emissions and energy efficiency of 40-tonne haulage trucks in fuel production and manufacturing in a Swedish context. The aim was to provide accurate greenhouse gas accounting and evaluate the contribution to mitigating climate change. Four scenarios were analysed: hydrogen from steam reforming, hydrogen from electrolysis, biomethane from biogas, and electricity in battery-electric vehicles. A comprehensive methodology involving literature review, data collection, and CO2 emissions calculations was employed. The manufacturing stage had higher CO2 emissions than fuel production for all scenarios. Hydrogen from steam reforming had the lowest emissions during manufacturing, while LBM from organic waste had the lowest emissions during fuel production. Sensitivity analysis highlighted the importance of lifespan, fuel consumption, and electricity generation in emissions. This research provides insights into renewable technologies and underscores the need for optimization to achieve climate goals. The study supports EU and Swedish climate laws and emphasizes the significance of considering the full life cycle of fuels to accurately assess their environmental impact.
99

Modelling and Optimization of Simultaneous Froward- and Reverse Logistics as Capacitated Vehicle Routing Problem : An optimization simulation model problem

Islam, Md Kamrul January 2022 (has links)
Environmental issues are a vital concern in today’s world. The Swedish government and local businesses are developing a sustainable business and eco-friendly environment for city inhabitants. Last-mile pickup and delivery services are a key concern, which significantly impacts the environment and society. The Norwegian/Swedish parcel delivery company Bring, the reusable waste management company Ragn-Sells, the city of Stockholm, the research institute Sustainable Innovation, and the KTH Royal Institute of Technology are jointly working together in the Intercitylog2 project with a vision to handle better last-mile pickups or deliveries that are jointly serviced by small electric vehicles from an urban micro terminal. This thesis addresses the optimizations of simultaneous pickup and delivery operations using homogeneous vehicles and considering vehicle capacity, time windows and environmental constraints. A mathematical model is developed to address the problem using an exact commercial solver. The quality of the solutions has been evaluated with real pickup and deliveries of the participating company. The primary objective function is formulated to minimize the travel cost by finding the shortest path, and the results are compared with current routing operation data. KPIs are developed and evaluated based on the facts and figures from the obtained results of the experiments. The two scenarios, big vehicles and small vehicles are also developed and evaluated to find the best route optimization opportunity for the companies. The results show that the optimized operation could decrease delivery distance by 36.72% and 37.13% and delivery time by 43.65% and 47.08% for big and small vehicles operations, respectively, compared to the current routing operations. A round trip can complete within a defined time frame to avoid the battery running out during a route. Energy constraints demonstrate that using electric vehicles considerably reduce significant amounts of CO2 emission from the environment. / Miljöfrågor är en viktig fråga i dagens värld. Den svenska regeringen och lokala företag arbetar tillsammans för att utveckla ett hållbart företagande och miljövänlig miljö för stadens invånare. Last-mile hämtning och leveranstjänster är en viktig fråga, som avsevärt påverkar miljön och samhället.Det norsk/svenska paketleveransföretaget Bring, återanvändbara avfallshanteringsföretaget Ragn- Sells, Stockholms stad, forskningsinstitutet Sustainable Innovation och Kungliga Tekniska Högskolan arbetar tillsammans i Intercitylog2-projektet för en vision för att bättre hantera last-mile pickuper eller leveranser som gemensamt betjänas av små elfordon från en urban mikroterminal. Detta examensarbete behandlar optimering av samtidiga hämtnings- och leveransoperationer med homogena fordon och med hänsyn till fordonskapacitet, tidsfönster och miljömässiga begränsningar. En matematisk modell utvecklas för att ta itu med problemet med en exakt kommersiell lösare och kvaliteten på lösningarna har utvärderats med verklig upphämtning och leveranser från det deltagande företaget. Den primära målfunktionen är formulerad för att minimera reskostnaden genom att hitta den kortaste vägen, och resultaten jämförs med aktuella ruttoperationsdata. KPI:er utvecklas och utvärderas utifrån fakta och siffror från de erhållna resultaten av experimenten. De två scenarierna, stora fordon och små fordon, är också utvecklade och utvärderade för att hitta den bästa ruttoptimeringsmöjligheten för företagen. Resultaten visar att den optimerade driften kan minska leveransavståndet med 36,72% och 37,13% och leveranstiden med 43,65% och 47,08% för stora och små fordonsoperationer, jämfört med nuvarande ruttoperationer. En tur och retur kan genomföras inom en definierad tidsram för att undvika att batteriet tar slut under en rutt. Energibegränsningar visar att användning av elfordon avsevärt minskar betydande mängder CO2-utsläpp från miljön.
100

Yield and Carbon Exchange of Sorghum Grown as Advanced Biofuel Feedstock onAbandoned Agricultural Land in Southeastern Ohio

Grennell, Jonathan L. 24 September 2014 (has links)
No description available.

Page generated in 0.0975 seconds