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Quantifying the Impact of Climate Change on Water Availability and Water Quality in the Chesapeake Bay WatershedWagena, Moges Berbero 28 February 2018 (has links)
Climate change impacts hydrology, nutrient cycling, agricultural conservation practices, and greenhouse gas (GHG) emissions. The Chesapeake Bay and its watershed are subject to the largest and most expensive Total Maximum Daily Load (TMDL) ever developed. It is unclear if the TMDL can be met given climate change and variability (e.g., extreme weather events). The objective of this dissertation is to quantify the impact of climate change and climate on water resources, nutrient cycling and export in agroecosystems, and agricultural conservation practices in the Chesapeake Bay watershed. This is accomplished by developing and employing a suite of modelling tools.
GHG emissions from agroecosystems, particularly nitrous oxide (N2O), are an increasing concern. To quantify N2O emissions a routine was developed for the Soil and Water Assessment Tool (SWAT) model. The new routine predicts N2O and di-nitrogen (N2) emissions by coupling the C and N cycles with soil moisture, temperature, and pH in SWAT. The model uses reduction functions to predict total denitrification (N2 + N2O production) and partitions N2 from N2O using a ratio method. The SWAT nitrification routine was modified to predict N2O emissions using reduction functions. The new model was tested using GRACEnet data at University Park, Pennsylvania, and West Lafayette, Indiana. Results showed strong correlations between plot measurements of N2O flux and the model predictions for both test sites and suggest that N2O emissions are particularly sensitive to soil pH and soil N, and moderately sensitive to soil temperature/moisture and total soil C levels.
The new GHG model was then used to analyze the impact of climate change and extreme weather conditions on the denitrification rate, N2O emissions, and nutrient cycling/export in the 7.4 km2 WE38 watershed in Pennsylvania. Climate change impacts hydrology and nutrient cycling by changing soil moisture, stoichiometric nutrient ratios, and soil temperature, potentially complicating mitigation measures. To quantify the impact of climate change we forced the new GHG model with downscaled and bias-corrected regional climate model output and derived climate anomalies to assess their impact on hydrology, nitrate (NO3-), phosphorus (P), and sediment export, and on emissions of N2O and N2. Model-average (± standard deviation) results indicate that climate change, through an increase in precipitation, will result in moderate increases in winter/spring flow (2.7±10.6 %) and NO3- export (3.0±7.3 %), substantial increases in dissolved P (DP, 8.8±19.8 %), total P (TP, 4.5±11.7 %), and sediment (17.9±14.2 %) export, and greater N2O (63.3±50.8 %) and N2 (17.6±20.7 %) emissions. Conversely, decreases in summer flow (-12.4±26.7 %) and the export of P (-11.4±27.4 %), TP (-7.9±24.5 %), sediment (-4.1±21.4 %), and NO3- (-12.2±31.4 %) are driven by greater evapotranspiration from increasing summer temperatures. Increases in N2O (20.1±29.3 %) and decreases in N2 (-13.0±14.6 %) are also predicted in the summer and driven by increases in soil moisture and temperature.
In an effort to assess the impact of climate change at a regional level, the model was then scaled-up to the entire Susquehanna River basin and was used to evaluate if agricultural best management practices (BMPs) can offset the impact of climate change. Agricultural BMPs are increasingly and widely employed to reduce diffuse nutrient pollution. Climate change can complicate the development, implementation, and efficiency of BMPs by altering hydrology, nutrient cycling, and erosion. We select and evaluate four common BMPs (buffer strips, strip crop, no-till, and tile drainage) to test their response to climate change. We force the calibrated model with six downscaled global climate models (GCMs) for a historic period (1990-2014) and two future scenario periods (2041-2065) and (2075-2099) and quantify the impact of climate change on hydrology, NO3-, total N (TN), DP, TP, and sediment export with and without BMPs. We also tested prioritizing BMP installation on the 30% of agricultural lands that generate the most runoff (e.g., critical source areas-CSAs). Compared against the historical baseline and excluding the impact of BMPs, the ensemble model mean (± standard deviation?) predictions indicate that climate change results in annual increases in flow (4.5±7.3%), surface runoff (3.5±6.1%), sediment export (28.5±18.2%) and TN (9.5±5.1%), but decreases in NO3- (12±12.8%), DP (14±11.5%), and TP (2.5±7.4%) export. When agricultural BMPs are simulated most do not appreciably change the overall water balance; however, tile drainage and strip crop decrease surface runoff generation and the export of sediment, DP, and TP, while buffer strips reduced N export substantially. Installing BMPs on critical source areas (CSAs) results in nearly the same level of performance for most practices and most pollutants. These results suggest that climate change will influence the performance of BMPs and that targeting BMPs to CSAs can provide nearly the same level of water quality impact as more widespread adoption.
Finally, recognizing that all of these model applications have considerable uncertainty associated with their predictions, we develop and employ a Bayesian multi-model ensemble to evaluate structural model prediction uncertainty. The reliability of watershed models in a management context depends largely on associated uncertainties. Our Objective is to quantify structural uncertainty for predictions of flow, sediment, TN, and TP predictions using three models: the SWAT-Variable Source Area model (SWAT-VSA), the standard SWAT model (SWAT-ST), and the Chesapeake Bay watershed model (CBP-model). We initialize each of the models using weather, soil, and land use data and analyze outputs of flow, sediment, TN, and TP for the Susquehanna River basin at the Conowingo Dam in Conowingo, Maryland. Using these three models we fit Bayesian Generalized Non - Linear Multilevel Models (BGMM) for flow, sediment, TN, and TP and obtain estimated outputs with 95% confidence intervals. We compare the BGMM results against the individual model results and straight model averaging (SMA) results using a split time period analysis (training period and testing period) to assess the BGMM in a predictive fashion. The BGMM provided better predictions of flow, sediment, TN, and TP compared to individual models and the SMA during the training period. However, during the testing period the BGMM was not always the best predictor; in fact, there was no clear best model during the testing period. Perhaps more importantly, the BGMM provides estimates of prediction uncertainty, which can enhance decision making and improve watershed management by providing a risk-based assessment of outcomes. / Ph. D. / Climate change impacts hydrology, nutrient cycling, agricultural conservation practices, and greenhouse gas (GHG) emissions. The Chesapeake Bay and its watershed are subject to the largest and most expensive Total Maximum Daily Load (TMDL) ever developed. It is unclear if the TMDL can be met given climate change and variability. The objective of this dissertation is to quantify the impact of climate change and climate on water resources, nutrient cycling and export in agroecosystems, and agricultural conservation practices in the Chesapeake Bay watershed. This is accomplished by developing and employing different modeling tools.
First, GHG emissions model was developed to quantify nitrous oxide (N₂O) emissions from agroecosystems, which are an increasing concern. The new model was then tested using observed N₂O emissions data at University Park, Pennsylvania, and West Lafayette, Indiana. Results showed strong correlations between plot measurements of N₂O flux and the model predictions for both test sites.
Second, the new GHG model was then used to analyze the impact of climate change and extreme weather conditions on the N₂O emissions, and nutrient cycling/export in small and regional watershed scale. To quantify the impact of climate change we forced the new GHG model with downscaled and bias-corrected regional climate model date to assess their impact on hydrology, nitrate (NO₃-), phosphorus (P), and sediment export, and on emissions of N₂O and N₂. Finally, recognizing that all of these model applications have considerable uncertainty associated with their predictions, we developed and employed a Bayesian multi-model ensemble to evaluate structural model prediction uncertainty.
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Determination of Scope 1 Greenhouse Gas Emissions in High-Frequency Filter ProductionPaukner, Maximilian January 2024 (has links)
In the electronics industry, several greenhouse gases (GHGs) are used as process gases in manufacturing processes. The organization RF360 as a Qualcomm Inc. subsidiary is using GHGs as input gases in the manufacturing processes dry etching, Chemical Vapor Deposition (CVD) and trimming in the fabrication plant in Munich.The estimation of GHG emissions from the use of process gases under Scope 1 requires a global and comprehensive approach to determine emission sources. This work provides the basis for the GHG emission estimation from process gas use under consideration of the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Dry etching and CVD process GHG emissions arecalculated using the Tier 2c method with process specific default emission factors. The process GHG emissions from trimming are characterized under Tier 3a, by determination of site-specific process emission factors. These emission factors are obtained from FTIR measurements in the inline. The measurement results show the input gas NF3 is largely not converted or destroyed in the trimming process. The total GHG emissions resulting from process gas use in the considered processes are determined by emissions of NF3, CF4 and N2O. The implementation and improvement of the approach requires further measurements of site-specific emission factors in the processes and Destruction Removal Efficiencies of the abatement systems.
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The underlying differences in greenhouse gases (GHG) emissions control and renewable energy : three European countries approaches to policyWilson, Kweku N. 30 November 2004 (has links)
Graduation date: 2005 / Best scan available for tables and figures.
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The impact of carbon taxation on the triple bottom line of the South African motor vehicle manufacturing industry / Surendran Subryan PillayPillay, Surendran Subryan January 2014 (has links)
Climate change has become an important concern for most governments in the current
day. The impact of global warming on economic productivity, human welfare and
environmental sustainability is becoming increasingly apparent to most people on the
planet, resulting in a rapid evolution of policy instruments which are capable of
addressing the issue of climate change. The ultimate aim of these policy instruments is to
influence corporate activity to environmentally sustainable behaviour. The two most
common policy instruments to effect change to most environmentally sustainable
behaviour is carbon taxation and cap-and-trade schemes.
Linked to climate change and environmental sustainability is the concept of sustainable
development which encompasses environmental sustainability, economic sustainability
and social sustainability. These principles are formalized and made relevant for
companies in the form of the triple bottom line. In South Africa, National Treasury
implemented a carbon excise tax in 2010 for the motor vehicle manufacturing industry in
response to the problem of global warming, and published a discussion document in
support of their decision to implement carbon tax. The document highlighted reasons for
the choice of carbon tax over other policy instruments such as cap-and-trade schemes and
penalties. Even though the choice for carbon tax was assessed from an environmental
perspective, the concept of sustainable development encompasses environmental,
economic and social sustainability. The subject matter for the 1st article was to compare
the two most widely used climate change instruments, known as cap-and-trade schemes
and carbon tax, from the broader perspective of sustainable development. This included an analysis of the effects of both instruments on both greenhouse gases as well as
economic indicators such as gross domestic product (GDP) and fiscal revenue.
Linked to the implementation of any instrument designed to address carbon emissions is
the concept of the social cost of carbon (SCC). The SCC is an estimate of the associated
monetary cost of the damage cause by emitting one additional ton of carbon into the
atmosphere. In a perfect world the SCC would be equal to, or lower than, the carbon tax
price. National Treasury‟s carbon tax price has never been assessed from an economic
perspective and in particular whether the price equates to the SCC from a feasibility
viewpoint. The testing of the carbon tax price against the SCC from an economic
perspective was the subject of the 2nd article, which then also evaluated the impact of
carbon tax on motor vehicle manufacturer‟s production techniques and vehicle fuel
efficiency.
Under the assumption that the carbon tax price approximates the SCC it is arguable that
companies are effectively paying for the damage cost to the environment in the form of
the carbon excise tax implemented. If the argument holds true, then the corporate social
investment expenditure may well be adjusted since corporate responsibilities to the
environment have been partially addressed by the payment of carbon tax. The impact of
carbon tax on CSI expenditure by motor vehicle manufacturers in South Africa was the
subject of the 3rd article in the thesis.
Furthermore, also linked to the implementation of carbon taxation for the motor vehicle
industry is the financial and sustainability reporting of the motor vehicle manufacturers‟
tax in the sustainability report and financial statements. Since carbon tax was designed to
promote behaviour toward a lower carbon footprint, evidence that such behaviour is being
affected can be observed in a company‟s sustainability report, which specifies the
company‟s planned path to carbon reduction in accordance with the disclosure standards
set in the Global Reporting Initiative (GRI). In terms of financial accounting there is no
specific International Financial Reporting Standard (IFRS) statement dealing with carbon
tax, and the correct treatment thereof will have to be interpreted in accordance with
existing accounting standards on revenue (IAS 18) and provisions (IAS 37). The subject
matter of 4th article assessed motor vehicle manufacturers reporting compliance of carbon
tax transactions in accordance with IFRS and the GRI. In summary, the implementation of carbon tax in South Africa is seen as a significant
move in the fight against climate change. If the instrument is to be considered effective it
must prove to be sustainable from an environmental, economic and social perspective.
The effectiveness of the instrument can only be measured if it was accurately reported in
the financial statements and sustainability reports in accordance with IFRS and the GRI.
Furthermore, the instrument should not be seen as an opportunity by motor vehicle
manufacturers to forego corporate responsibility to environment and thus should not
impact CSI expenditure which is a significant part of the welfare contribution by South
African businesses to the people of South Africa. / PhD (Tax), North-West University, Potchefstroom Campus, 2014
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The impact of carbon taxation on the triple bottom line of the South African motor vehicle manufacturing industry / Surendran Subryan PillayPillay, Surendran Subryan January 2014 (has links)
Climate change has become an important concern for most governments in the current
day. The impact of global warming on economic productivity, human welfare and
environmental sustainability is becoming increasingly apparent to most people on the
planet, resulting in a rapid evolution of policy instruments which are capable of
addressing the issue of climate change. The ultimate aim of these policy instruments is to
influence corporate activity to environmentally sustainable behaviour. The two most
common policy instruments to effect change to most environmentally sustainable
behaviour is carbon taxation and cap-and-trade schemes.
Linked to climate change and environmental sustainability is the concept of sustainable
development which encompasses environmental sustainability, economic sustainability
and social sustainability. These principles are formalized and made relevant for
companies in the form of the triple bottom line. In South Africa, National Treasury
implemented a carbon excise tax in 2010 for the motor vehicle manufacturing industry in
response to the problem of global warming, and published a discussion document in
support of their decision to implement carbon tax. The document highlighted reasons for
the choice of carbon tax over other policy instruments such as cap-and-trade schemes and
penalties. Even though the choice for carbon tax was assessed from an environmental
perspective, the concept of sustainable development encompasses environmental,
economic and social sustainability. The subject matter for the 1st article was to compare
the two most widely used climate change instruments, known as cap-and-trade schemes
and carbon tax, from the broader perspective of sustainable development. This included an analysis of the effects of both instruments on both greenhouse gases as well as
economic indicators such as gross domestic product (GDP) and fiscal revenue.
Linked to the implementation of any instrument designed to address carbon emissions is
the concept of the social cost of carbon (SCC). The SCC is an estimate of the associated
monetary cost of the damage cause by emitting one additional ton of carbon into the
atmosphere. In a perfect world the SCC would be equal to, or lower than, the carbon tax
price. National Treasury‟s carbon tax price has never been assessed from an economic
perspective and in particular whether the price equates to the SCC from a feasibility
viewpoint. The testing of the carbon tax price against the SCC from an economic
perspective was the subject of the 2nd article, which then also evaluated the impact of
carbon tax on motor vehicle manufacturer‟s production techniques and vehicle fuel
efficiency.
Under the assumption that the carbon tax price approximates the SCC it is arguable that
companies are effectively paying for the damage cost to the environment in the form of
the carbon excise tax implemented. If the argument holds true, then the corporate social
investment expenditure may well be adjusted since corporate responsibilities to the
environment have been partially addressed by the payment of carbon tax. The impact of
carbon tax on CSI expenditure by motor vehicle manufacturers in South Africa was the
subject of the 3rd article in the thesis.
Furthermore, also linked to the implementation of carbon taxation for the motor vehicle
industry is the financial and sustainability reporting of the motor vehicle manufacturers‟
tax in the sustainability report and financial statements. Since carbon tax was designed to
promote behaviour toward a lower carbon footprint, evidence that such behaviour is being
affected can be observed in a company‟s sustainability report, which specifies the
company‟s planned path to carbon reduction in accordance with the disclosure standards
set in the Global Reporting Initiative (GRI). In terms of financial accounting there is no
specific International Financial Reporting Standard (IFRS) statement dealing with carbon
tax, and the correct treatment thereof will have to be interpreted in accordance with
existing accounting standards on revenue (IAS 18) and provisions (IAS 37). The subject
matter of 4th article assessed motor vehicle manufacturers reporting compliance of carbon
tax transactions in accordance with IFRS and the GRI. In summary, the implementation of carbon tax in South Africa is seen as a significant
move in the fight against climate change. If the instrument is to be considered effective it
must prove to be sustainable from an environmental, economic and social perspective.
The effectiveness of the instrument can only be measured if it was accurately reported in
the financial statements and sustainability reports in accordance with IFRS and the GRI.
Furthermore, the instrument should not be seen as an opportunity by motor vehicle
manufacturers to forego corporate responsibility to environment and thus should not
impact CSI expenditure which is a significant part of the welfare contribution by South
African businesses to the people of South Africa. / PhD (Tax), North-West University, Potchefstroom Campus, 2014
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Le Mali et les biocarburants : une analyse à partir d'un modèle d'équilibre général calculable dynamiqueYamba, Emmanuel Magloire January 2015 (has links)
Résumé : Les résultats alarmants du Groupe d’Experts Intergouvernemental sur l’Évolution du Climat (GIEC) et la tenue des sommets chaque année sur le réchauffement climatique poussent de nombreux pays à prendre la chose au sérieux (notre-planète.info, 2015). C’est ainsi que le Mali, pays enclavé et importateur net de produits pétroliers, cherche des moyens non seulement pour emboiter le pas à la communauté internationale sur la protection de l’environnement mais aussi à mieux gérer sa politique énergétique. Cette volonté repose sur le développement des biocarburants grâce au jatropha qui se cultive aussi bien sur des sols semi-arides que fertiles. Depuis plusieurs décennies les biocarburants font l’objet de recherches. Certaines études permettent de conclure que leur utilisation réduirait les émissions de GES tandis que d’autres vont plus loin au-delà du cadre écologique et trouvent que c’est une source de rentabilité économique. Pour mieux illustrer ses effets, nous avons utilisé un modèle d’équilibre général calculable dynamique (MEGCD) qui permet de voir les interactions des variables structurelles de l’économie malienne sur une durée de 4 ans. Les résultats montrent qu’une politique protectionniste du secteur des biocarburants jumelée à une politique d’exploitation accrue du jatropha à partir des terres non occupées au Mali, génèrent plus d’activité dans le pays et permet de réduire les importations de carburant. De même, la croissance dans le secteur de l’énergie permet d’augmenter la production en électricité dans le pays. / Abstract : The alarming results of the Intergovernmental Panel on Climate Change (IPCC) and the summits annually on global warming are pushing many countries to take it seriously (notre-planète.info, 2015). In this way Mali, landlocked and importing country of fuel, take measure to join in international community on protection of environment also to manage better his energetic policy. This determination is based on the development of biofuels through jatropha which both grown on semi-arid soils fertile. Many searchers are worked on the advantages and disadvantages to Jatropha compared to diesel and fund that his useful reduced greenhouse gas emission while others go further beyond the ecological environment and find it a source of economic profitability. We use a dynamic calculable general equilibrium model (DCGEM) to illustrate relations between all structural variables of economy Malian on four years. We find that a biofuel protectionist policy combined with an increased operating policy jatropha from idle land in Mali, generate more activity and reduces fuel imports. Similarly, growth in the energy sector can increase electricity production in the country.
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Process engineering and development of post-combustion CO2 separation from fuels using limestone in CaO-looping cycleKavosh, Masoud January 2011 (has links)
Global CO2 emissions produced by energy-related processes, mainly power plants, have increased rapidly in recent decades; and are widely accepted as the dominant contributor to the greenhouse gas (GHG) effect and consequent climate changes. Among countermeasures against the emissions, CO2 capture and storage (CCS) is receiving much attention. Capture of CO2 is the core step of CCS as it contributes around 75% of the overall cost, and may increase the production costs of electricity by over 50%. The reduction in capture costs is one of the most challenging issues in application of CCS to the energy industry. Using limestone in CaO-looping cycles is a promising capture technology to provide a cost-effective separation process to remove CO2 content from power plants operations. Limestone has the advantage of being relatively abundant and cheap, and that has already been widely used as a sorbent for sulphur capture. However, this technology suffers from a critical challenge caused by the decay in the sorbent capture capacity during cyclic carbonation/calcination, which results in the need for more sorbent make-up; hence a reduction in cost efficiency of the technology. The performance of sorbent influenced by several operating and reaction conditions. Therefore, much research involves investigation of influencing factors and different methods to reduce the sorbent deactivation. Cont/d.
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The effect of endwall contouring on the unsteady flow through a turbine rotorDunn, Dwain Iain 12 1900 (has links)
Thesis (PhD) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: With increasing environmental concerns and the drive for a greener economy comes an
increased desire to improve turbine engine fuel efficiency and reduce emissions. Unfortunately
weight reduction techniques used increase the blade loading, which in turn increases
the losses. Non-axisymmetric endwall contouring is one of several techniques being investigated
to reduce loss in a turbine. An investigation at Durham University produced a
non-axisymmetric endwall design for a linear cascade. An adaption of the most promising
endwall was investigated in an annular rotating test rig at the CSIR using steady state
instrumentation. The current investigation extends those investigations into the unsteady
time domain.
Previous investigations found that a generic rotor endwall contour improved efficiency
by controlling the endwall secondary flow vortex system in both a linear cascade and an
annular 1½ stage rotating test turbine. The current research was aimed at determining if
there were any unsteady effects introduced by the contoured endwall. The approach was
unique in that it investigated the unsteady effects of an endwall contour originally designed
for a linear cascade both experimentally and numerically at three incidence angles (positive,
zero and negative to represent increased load, design load and decreased load respectively),
the results of which are openly available.
Unsteady experimental hotfilm results showed that the endwall contour made the velocity
profile more radially uniform by reducing the strength of the endwall secondary flow
vortex system. The fluctuations in the velocity were also reduced producing a more temporally
uniform velocity profile. The FFT magnitude of the velocity at the blade passing
frequency below midspan was also reduced. It was found that the reduction in the endwall
secondary flow vortex system due to the contour increased with increasing loading.
Numerical results showed that the oscillations in the flow were small and did not penetrate
the boundary layer. The contoured rotor was forward and aft loaded when compared
to the annular rotor, resulting in a weaker cross passage pressure gradient which allowed
the endwall secondary flow vortex system to be less tightly wrapped. Numerical results did not show a significant difference in the oscillations observed in the annular and contoured
rotor.
A new objective function for use in the endwall optimisation process was proposed that
acts as a proxy for efficiency, but is less prone to uncertainty in the results. When used on
the current results it shows the same trend as efficiency. It remains to be used to design
an endwall for full validation. / AFRIKAANSE OPSOMMING: Met ’n toenemende omgewingsbesorgdheid en die strewe na ’n groener ekonomie kom ’n
toenemende behoefte om turbine enjin brandstofdoeltreffendheid te verbeter en vrystellings
te verlaag. Ongelukkig het gewigsbesparingstegnieke wat gebruik is die lemlading verhoog,
wat op sy beurt die verliese verhoog. Nie-assimmetriese endwandprofilering is een van
verskeie tegnieke wat ondersoek word om verliese in ’n turbine te verminder. ’n Ondersoek
by die Universiteit van Durham het ’n nie-assimmetriese endwandontwerp vir ’n lineêre
kaskade gelewer. ’n Aanpassing van die mees belowende endwand is in ’n annulêre roterende
toetsopstelling by die WNNR getoets, deur gebruik te maak van bestendige toestand
instrumentasie. Die huidige ondersoek brei daardie ondersoeke uit na die nie-bestendige
verwysingsraamwerk .
Vorige ondersoeke het bevind dat die generiese rotor endwandprofiel doeltreffendheid
verbeter as gevolg van die beheer van die endwand sekondêre vloei draaikolkstelsel in
beide ’n lineêre kaskade sowel as ’n annulêre 1½ stadium roterende toetsturbine. Die
huidige navorsing was daarop gemik om vas te stel of die endwandprofiel enige onbestendige
effekte tot gevolg gehad het. Die benadering was uniek in die sin dat dit die onbestendige
effekte ondersoek het van ’n endwandprofiel wat oorspronklik ontwerp is vir ’n lineêre
kaskade beide eksperimenteel en numeries op drie invalsshoeke (positief, nul en negatief
om onderskeidelik verhoogde lading, ontwerplading en verlaagde lading te verteenwoordig),
waarvan die resultate algemeen beskikbaar is.
Onbestendige eksperimentele warmfilm resultate het getoon dat die endwandprofiel die
snelheidsprofiel meer radiaal uniform gemaak het deur die vermindering van die sterkte
van die endwand sekondêre vloei werwelstelsel. Die skommelinge in die snelheid is ook
verminder wat ’n meer tyduniforme snelheidsprofiel gelewer het. Die FFT (Fast Fourier
Transform) grootte van die snelheid van die lem verbygaan frekwensie onder lem midbestek
het ook verminder. Daar was bevind dat die vermindering in die endwand sekondêre vloei
draaikolkstelsel as gevolg van die endwandprofiel toeneem met toenemende lading. Numeriese resultate het getoon dat die ossilasie in die vloei klein was en nie die grenslaag
binnegedring het nie. Die rotor met gevormde wand het ’n voor- en agterlading gehad in
vergelyking met die rotor met annulêre wand, wat tot ’n laer drukgradient dwarsop die
vloeirigting gelei het, die endwand sekondêre vloei draaikolkstelsel minder beperk het.
Numeriese resultate het nie ’n beduidende verskil in die ossilasies tussen die annulêre en
gevormde rotorwand getoon nie.
’n Nuwe doelwitfunksie vir gebruik in die endwand optimersproses is voorgestel wat
dien as ’n plaasvervanger vir doeltreffendheid, maar minder geneig is tot onsekerheid in
die resultate. Wanneer dit gebruik word op die huidige resultate toon dit dieselfde tendens
as doeltreffendheid. Dit moet nog gebruik word in die ontwerp van ’n endwand vir volledige
bevestiging.
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Adaptive water distribution system design under future uncertaintyBasupi, Innocent January 2013 (has links)
A water distribution system (WDS) design deals with achieving the desired network performance. WDS design can involve new and / or existing network redesigns in order to keep up with the required service performance. Very often, WDS design is expensive, which encourages cost effectiveness in the required investments. Moreover, WDS design is associated with adverse environmental implications such as greenhouse gas (GHG) emissions due to energy consumption. GHGs are associated with global warming and climate change. Climate change is generally understood to cause reduction in water available at the sources and increase water demand. Urbanization that takes into account factors such as demographics (population ageing, household occupancy rates, etc.) and other activities are associated with water demand changes. In addition to the aforementioned issues, the challenge of meeting the required hydraulic performance of WDSs is worsened by the uncertainties that are associated with WDS parameters (e.g., future water demand). With all the factors mentioned here, mitigation and adaptive measures are considered essential to improve WDS performance in the long-term planning horizon. In this thesis, different formulations of a WDS design methodologies aimed at mitigating or adapting the systems to the effects of future changes such as those of climate change and urbanization are explored. Cost effective WDS designs that mitigate climate change by reducing GHG emissions have been investigated. Also, water demand management (DM) intervention measures, i.e., domestic rainwater harvesting (RWH) systems and water saving appliance schemes (WSASs) have been incorporated in the design of WDSs in an attempt to mitigate, adapt to or counteract the likely effects of future climate change and urbanization. Furthermore, flexibility has been introduced in the long-term WDS design under future uncertainty. The flexible methodology is adaptable to uncertain WDS parameters (i.e., future water demand in this thesis) thereby improving the WDS economic cost and hydraulic performance (resilience). The methodology is also complimented by strategically incorporating DM measures to further enhance the WDS performance under water demand uncertainty. The new methodologies presented in this thesis were successfully tested on case studies. Finally, conclusions and recommendations for possible further research work are made. There are potential benefits (e.g., cost savings, additional resilience, and lower GHG emissions) of incorporating an environmental objective and DM interventions in WDS design. Flexibility and DM interventions add value in the design of WDSs under uncertainty.
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Tracking Emissions Reductions and Energy Efficiency in the Steel IndustryMorfeldt, Johannes January 2017 (has links)
The iron and steel industry has become increasingly globalised. Market conditions are also changing and de-carbonisation of production is challenging. The objective of this thesis is to assess how energy efficiency and greenhouse gas emissions reductions can be promoted and effectively monitored in the steel industry. The thesis contributes with analyses based on the Malmquist Productivity Index for a top-down analysis of the energy efficiency of EU Member States’ iron and steel production, and Partial Least Squares regression for bottom-up assessments of different monitoring tools. The thesis also contributes with a scrap availability assessment module to enhance the energy system model ETSAP-TIAM. The first phase of the research showed that future production needs to shift towards innovative low-CO2 technologies even when all available recycled material is fully used. Techniques using carbon capture and storage (CCS) as well as hydrogen-based technologies can be expected to become economically viable under tightened climate policies. The second phase of the research showed that current indicators are insufficient. System boundaries of energy use and emissions data do not align with production statistics. Indicators based on energy use or emissions in relation to production in physical terms may be useful to track specific processes. However, current indicators fail to reflect the companies’ product mix. Enhanced energy and climate indicators that adjust for the product mix provide better estimates while failing to reflect the increasing globalisation. Effective monitoring of industrial transformation will be increasingly important as pressure from climate policy via global CO2-pricing is unlikely in the short term. Current or enhanced indicators do not fully capture industrial transformation and are not recommended. Future research should focus on defining indicators to estimate energy use and emissions along industrial value chains in climate policy contexts. / Järn- och stålindustrin har blivit alltmer globaliserad. Marknadsvillkoren förändras samtidigt som utfasningen av fossila bränslen är utmanande. Målet med den här avhandlingen är att bedöma hur energieffektivitet och växthusgasutsläppsminskningar kan främjas och effektivt utvärderas inom stålindustrin. Avhandlingen bidrar med analyser baserade Malmquists produktivitetsindex för att analysera energieffektivitet av EU:s medlemsstaters järn- och stålproduktion, och partiell minsta- kvadrat-regression för att bedöma olika utvärderingsmått. Avhandlingen bidrar även med en modul som bedömer skrottillgång för att förbättra energisystemmodellen ETSAP-TIAM. I en första fas visade forskningen att framtida produktion behöver ställas om mot innovativa teknologier med låga CO2-utsläpp även när allt tillgängligt återvunnet material används fullt ut. Tekniker som använder koldioxidinfångning och -lagring (CCS) samt vätebaserade teknologier kan förväntas bli ekonomiskt försvarbara under åtstramade klimatpolitiska styrmedel. I en andra fas visade forskningen att nuvarande indikatorer är otillräckliga. Systemgränser för energianvändnings- och växthusgasutsläppsdata stämmer inte överens med produktionsstatistik. Indikatorer utifrån energianvändning eller utsläpp i relation till fysisk produktion kan vara användbara för att följa upp specifika processer. Nuvarande indikatorer lyckas dock inte spegla företagens produktmix. Förbättrade energi- och klimatindikatorer som justerar för produktmixen ger bättre uppskattningar, men speglar inte branschens ökande globalisering. Effektiv utvärdering av industriell transformation blir alltmer viktig då påtryckning från klimatpolitiska styrmedel via global CO2-prissättning är kortsiktigt osannolik. Nuvarande eller förbättrade indikatorer fångar inte industriell transformation fullt ut och rekommenderas inte. Framtida forskning bör fokusera på att definiera indikatorer som uppskattar energianvändning och växthusgasutsläpp längs industriella värdekedjor. / <p>QC 20170428</p>
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