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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.
451

Fostering the delivery of wind power : an evaluation of the performance of policy instruments in three European Union member states

Otitoju, Afolabi January 2010 (has links)
Worldwide energy policies are built on three pillars: ‘cost competitiveness’, ‘security of energy supply’, and ‘environmental responsibility.’ This has brought about the integration of renewable energy sources into national systems with the deployment of policy instruments to make renewable energy sources electricity (RES-E) capable of nearly competing on a commercial basis with traditional forms of electricity generation. At the national level within the EU, there has been much experimentation with different policy instruments with varying levels of success. Nevertheless the EU as a whole will not meet its stipulated renewable energy target. This study challenges the theoretical and abstract evaluation presented in the literature about EU wind power delivery systems and has developed an integrative evaluation framework. This evaluation framework is used in this study to present the views of key stakeholders on their experiences with the performance of key policy instruments (feed-in tariff, and renewables obligation) implemented in three EU Member States namely: Germany, The Netherlands, and United Kingdom. It also challenges the EU-wide harmonised renewable energy policy agenda as proposed in Directive 2001/77/EC. The concept of path dependency of the historical institutional approach was adopted in order to explore the diversity of the wind power industry across the three country cases. An indepth semi-structured interview with fifty-five senior wind power policy makers and experts was conducted to explore the historical emergence, the architect, and the outcome of the support and implementation of the policy instruments. Findings showed that the approach to wind power deployment in the three country cases differs significantly and this has affected the pattern of each country’s wind power policy instrument. Also, the role and contribution of the stakeholder groups to the success of the wind power policy instruments differ significantly in each of the country cases. This helps to explain the performance of the different policy instruments adopted. Concerning the harmonisation of EU renewable energy policy instruments which have received much attention in recent times, this study found that harmonisation based on a single policy instrument is not feasible and may ultimately inhibit the growth of the European wind power market. A harmonised system may cause uncertainties amongst willing investors, thereby causing a withdrawal of further investment in the wind power market. If this happens, Europe may also lose its position as the world leader in the wind power market. Furthermore, national histories demonstrates that Member States have different culture, stakeholder groups, political, and business practices that will influence policy instruments and the likelihood of any policy succeeding. Thus, rather than promoting harmonisation and political market for wind power, it is important that Member States adopt and implement, stable, flexible, and transparent policy instruments that enable wind power and other renewable energy sources to emerge, develop, and go through the R&D stage to a point of maturity where they can compete with other energy sources with limited financial support.
452

Ecological and anthropogenic constraints on waterbirds of the Forth Estuary : population and behavioural responses to disturbance

Dwyer, Ross Gordon January 2010 (has links)
Disturbance from engineering works is an increasing problem in terrestrial and marine ecosystems throughout the world. Many reported declines in population size, breeding success and body condition have been diagnosed as the result of anthropogenic disturbance, however little is known about the effect of long-term disturbance from large-scale engineering works. Understanding the mechanisms by which animals respond to anthropogenic activities is fundamental to explaining interactions, and resolving potential conflicts between humans and wildlife. This thesis focuses on the factors affecting the habitat use and foraging decisions in wintering shorebirds and wildfowl. The first half of this thesis considers the direct and indirect impacts on waterbirds of a major engineering project in central Scotland; construction of the new Clackmannanshire Bridge at Kincardine-on-Forth. For individual bird species in close proximity to the bridge site, round-the-clock construction work had consequences ranging from neutral to considerably negative. Cormorant Phalacrocorax carbo declined in the area, probably as a result of the disturbance of an important low tide roost. Redshank Tringa totanus, previously abundant in the prey-rich areas adjacent to the construction site, were displaced into poorer areas for most of the construction period; where they may also have suffered from increased interference competition and elevated risk from raptorial predators. Some positive effects of industrial development were also revealed; radio-transmitters combined with tilt-switch posture sensors indicate that Redshank were able to capitalise on the improved nocturnal visibility in areas around Grangemouth docks to assist with foraging and predator detection. Evidence is presented that birds switched foraging strategy (from sight to touch feeding) depending on ambient light levels; whereby artificial light was used in a similar manner to moonlight to assist with prey detection. Redshank also avoided riverine areas at night that were used frequently by day, probably in response to an elevated threat from nocturnal predators. As the predator landscape changes from day into night, birds adopt different strategies to minimise the risk from nocturnal predators. It is clearly important, therefore, that information on nocturnal distributions is available to inform decisions on site management, especially where anthropogenic activity continues throughout the diel cycle. Behavioural decisions were shown to vary widely within a species depending on individual state, metabolic demands and previous exposure to human disturbance. Prey resources were shown to change dramatically over the course of a winter. In response to this decline, the home range of Redshank contracted over a winter season. Similarly, animals responded less and took greater risks in response to experimental disturbance events later in the winter than earlier in the winter, and on days when the temperature was lower. This effect was strongest for individuals occupying heavily disturbed areas, which were possibly already compensating for lost feeding time and a negative energy balance. The results were consistent with the hypothesis that those individuals that respond most obviously to human disturbance were those least likely to suffer fitness consequences. This is the opposite from what is commonly assumed when behaviour is used as an index of disturbance impacts, most notably in the use of flush distance in the design of wildlife buffer zones. In conclusion, this study demonstrated various negative impacts of disturbance, including local displacement, due to construction activity on overwintering waterbirds. It also revealed two key, but poorly understood, phenomena relating to mechanisms for coping with anthropogenic disturbance: routine utilisation of artificial light to extend night-time feeding opportunities amongst Redshank and an adaptive flexibility in escape responses across a range of species under varying conditions of risk.
453

Grid Optimization Of Wind-Solar Hybrid Power Plants : Case Study Of Internal Grid Connections

Storgärd, Per January 2016 (has links)
Hybrid renewable energy systems (HRES) have proven to be a more stable and feasible source of energy than heir single source counterparts. The benefit of HRES is their ability to balance the stochastic behavior of wind and solar production. As result of this, they have been used as stand-alone systems with great success. Optimization studies in the field have shown optimum sizing of the components in the system to be a key element in order to increase feasibility. This paper focuses on the HRES impact on internal grid design and cost. The goal of the thesis is to create a mathematical function and graph on the internal grid design/cost relation for a virtual site with varying wind speed and solar irradiation. A secondary goal is to analyze how much Photovoltaics (PV) in Megawatt (MW) that can be connected to the internal grid post realization of the wind farm and to performed this analyze on the two specific case projects, Site A (17.25 MW) in Sweden and Site B (51.75 MW) in Italy. By utilizing a case study methodology, a mathematical model was created based on two case projects, both with potential to be a combined Wind-PV hybrid plants provided by the wind developer OX2. Identifiers for the two cases studied in this thesis where removed with respect to OX2’s ongoing projects. Hybrid renewable energy systems is a method of increasing the utilization of a regions RES, the system has an increase in overall power output compared to the single RES alternative. However, the internal grid cost was shown to be 3.85 % more expensive Site A and 5.3 % in Site B. This stood in direct correlation to the HRES in Site A using 8.6 % more cable for its internal grid and 29.7 % more in Site B, this is highly depending (depending on the location of the PV array). Furthermore, the case projects showed that the maximum PV to be connected post realization of the farm without major curtailment would be 11.5% of the wind farms rated power in the case of site A and 67.6 % in the case of Site B. Variations in wind speed and solar irradiation were shown to have some impact on grid cost. However, the results pointed out that grid cost in HRES is to a higher degree affected by total cable length in the internal grid than fluctuation in available energy sources. The extent of increase in cable length, the total grid investment cost rises up to 53.4 % for the two case projects.
454

Constructal Design of Energy Systems

Alalaimi, Mohammad Ali January 2016 (has links)
<p>This dissertation shows the use of Constructal law to find the relation between the morphing of the system configuration and the improvements in the global performance of the complex flow system. It shows that the better features of both flow and heat transfer architecture can be found and predicted by using the constructal law in energy systems. Chapter 2 shows the effect of flow configuration on the heat transfer performance of a spiral shaped pipe embedded in a cylindrical conducting volume. Several configurations were considered. The optimal spacings between the spiral turns and spire planes exist, such that the volumetric heat transfer rate is maximal. The optimized features of the heat transfer architecture are robust. Chapter 3 shows the heat transfer performance of a helically shaped pipe embedded in a cylindrical conducting volume. It shows that the optimized features of the heat transfer architecture are robust with respect to changes in several physical parameters. Chapter 4 reports analytically the formulas for effective permeability in several configurations of fissured systems, using the closed-form description of tree networks designed to provide flow access. The permeability formulas do not vary much from one tree design to the next, suggesting that similar formulas may apply to naturally fissured porous media with unknown precise details, which occur in natural reservoirs. Chapter 5 illustrates a counterflow heat exchanger consists of two plenums with a core. The results show that the overall flow and thermal resistance are lowest when the core is absent. Overall, the constructal design governs the evolution of flow configuration in nature and energy systems.</p> / Dissertation
455

Dynamic Life Cycle Assessment Modeling Approaches for Transboundary Energy Feedstocks

Morrison, Brandon January 2016 (has links)
<p>The rise of the twenty-first century has seen the further increase in the industrialization of Earth’s resources, as society aims to meet the needs of a growing population while still protecting our environmental and natural resources. The advent of the industrial bioeconomy – which encompasses the production of renewable biological resources and their conversion into food, feed, and bio-based products – is seen as an important step in transition towards sustainable development and away from fossil fuels. One sector of the industrial bioeconomy which is rapidly being expanded is the use of biobased feedstocks in electricity production as an alternative to coal, especially in the European Union.</p><p>As bioeconomy policies and objectives increasingly appear on political agendas, there is a growing need to quantify the impacts of transitioning from fossil fuel-based feedstocks to renewable biological feedstocks. Specifically, there is a growing need to conduct a systems analysis and potential risks of increasing the industrial bioeconomy, given that the flows within it are inextricably linked. Furthermore, greater analysis is needed into the consequences of shifting from fossil fuels to renewable feedstocks, in part through the use of life cycle assessment modeling to analyze impacts along the entire value chain.</p><p>To assess the emerging nature of the industrial bioeconomy, three objectives are addressed: (1) quantify the global industrial bioeconomy, linking the use of primary resources with the ultimate end product; (2) quantify the impacts of the expaning wood pellet energy export market of the Southeastern United States; (3) conduct a comparative life cycle assessment, incorporating the use of dynamic life cycle assessment, of replacing coal-fired electricity generation in the United Kingdom with wood pellets that are produced in the Southeastern United States.</p><p>To quantify the emergent industrial bioeconomy, an empirical analysis was undertaken. Existing databases from multiple domestic and international agencies was aggregated and analyzed in Microsoft Excel to produce a harmonized dataset of the bioeconomy. First-person interviews, existing academic literature, and industry reports were then utilized to delineate the various intermediate and end use flows within the bioeconomy. The results indicate that within a decade, the industrial use of agriculture has risen ten percent, given increases in the production of bioenergy and bioproducts. The underlying resources supporting the emergent bioeconomy (i.e., land, water, and fertilizer use) were also quantified and included in the database.</p><p>Following the quantification of the existing bioeconomy, an in-depth analysis of the bioenergy sector was conducted. Specifically, the focus was on quantifying the impacts of the emergent wood pellet export sector that has rapidly developed in recent years in the Southeastern United States. A cradle-to-gate life cycle assessment was conducted in order to quantify supply chain impacts from two wood pellet production scenarios: roundwood and sawmill residues. For reach of the nine impact categories assessed, wood pellet production from sawmill residues resulted in higher values, ranging from 10-31% higher.</p><p>The analysis of the wood pellet sector was then expanded to include the full life cycle (i.e., cradle-to-grave). In doing to, the combustion of biogenic carbon and the subsequent timing of emissions were assessed by incorporating dynamic life cycle assessment modeling. Assuming immediate carbon neutrality of the biomass, the results indicated an 86% reduction in global warming potential when utilizing wood pellets as compared to coal for electricity production in the United Kingdom. When incorporating the timing of emissions, wood pellets equated to a 75% or 96% reduction in carbon dioxide emissions, depending upon whether the forestry feedstock was considered to be harvested or planted in year one, respectively.</p><p>Finally, a policy analysis of renewable energy in the United States was conducted. Existing coal-fired power plants in the Southeastern United States were assessed in terms of incorporating the co-firing of wood pellets. Co-firing wood pellets with coal in existing Southeastern United States power stations would result in a nine percent reduction in global warming potential.</p> / Dissertation
456

Water oxidation : From Molecular Systems to Functional Devices

Daniel, Quentin January 2017 (has links)
The production of hydrogen gas, through the process of water splitting,is one of the most promising concepts for the production of clean andrenewable fuel.The introduction of this thesis provides a brief overview of fossil fuelsand the need for an energy transition towards clean and renewable energy.Hydrogen gas is presented as a possible candidate fuel with its productionthrough artificial photosynthesis, being described. However, the highlykinetically demanding key reaction of the process – the water oxidationreaction – requires the use of a catalyst. Hence, a short presentation of differentmolecular water oxidation catalysts previously synthesized is also provided.The second part of the thesis focuses on ruthenium-based molecularcatalysis for water oxidation. Firstly, the design and the catalytic performancefor a new series of catalysts are presented. Secondly, a further study onelectron paramagnetic resonance of a catalyst shows the coordination of awater molecule to a ruthenium centre to generate a 7-coordinated complex atRuIII state. Finally, in an electrochemical study, coupled with nuclear magneticresonance analysis, mass spectrometry and X-ray diffraction spectroscopy, wedemonstrate the ability of a complex to perform an in situ dimerization of twounits in order to generate an active catalyst.The final part of this thesis focuses on immobilisation of first rowtransition metal catalysts on the surface of electrodes for electrochemical wateroxidation. Initially, a copper complex was designed and anchored on a goldsurface electrode. Water oxidation performance was studied byelectrochemistry, while deactivation of the electrode was investigated throughX-ray photoelectron spectroscopy, revealing the loss of the copper complexfrom the electrode during the reaction. Finally, we re-investigated cobaltporphyrin complexes on the surface of the electrode. Against the backgroundof previous report, we show that the decomposition of cobalt porphyrin intocobalt oxide adsorbed on the surface is responsible for the catalytic activity.This result is discussed with regard to the detection limit of various spectroscopic methods. / <p>QC 20170529</p>
457

Primena multi-kriterijumske analize u dizajniranju energetskih politika orijentisanih ka podršci razvoja obnovljivih izvora energije / Application of multi-criteria analysis in the design of energy policy oriented towards supporting the development of renewable energy sources

Vasić Goran 07 April 2016 (has links)
<p>Razvojem i testiranjem autentičnog modela dokazano je da se primenom multikriterijumske analize uz primenu PROMETHEE metode može kreirati funkcionalan, operativan i primenljiv alat za dizajniranje energetskih politika orijentisanih ka podršci razvoja obnovljivih izvora energije. Model je testiran na energetskom profilu Grada Novog Sada. Pretpostavljeno je da lokalne vlasti Grada Novog Sada imaju nameru da dizajniraju razvojnu politiku/meru sa ciljem da podstaknu korišćenje obnovljivih izvora energije za grejanje stambenih objekata (porodičnih kuća) i pripremu tople sanitarne vode.</p> / <p>Development and testing of an authentic model has proven that the application of multi-criteria analysis by applying the PROMETHEE method can create a functional, operational and applicable tool for designing energy policy oriented towards supporting the development of renewable energy sources. It is assumed that local authorities in Novi Sad have the intetion to design development policies / actions in order to promote the use of renewable source for heating residental buldings (family houses) and hot water.</p>
458

Biodiversity Protection in an Aspiring Carbon-Neutral Society : A Legal Study on the Relationship between Renewable Energy and Biodiversity in a European Union Context

Malafry, Melina January 2016 (has links)
There is a vision in the EU for a transition to a low carbon society, including a carbon-neutral energy system, containing a high share of renewable energy. However, this vision is not isolated from other political goals, such as halting the loss of biodiversity by 2020. Both of these goals are accompanied by EU legislation promoting their respective aims. One of the central challenges, in light of this transition, is the very nature of the legal system – that it is rather fragmented – both regarding the substantive law applicable to renewable energy activities and the legal processes that renewable energy activities face. The aim is therefore to discuss certain challenges arising from the fragmented legal system applicable to renewable energy activities. The dissertation is based on EU and Swedish law. First, I investigate the EU’s competence in the field of renewable energy and address how such policy may better reflect the protection of biodiversity. Thereafter, in a Swedish context, I analyse the relationship between protection of biodiversity and promotion of renewable energy. Finally, I address the problems arising from the fragmented legal procedures of renewable energy activities, with the main example of wind power installations and new transmission lines. In general, this study suggests that the current system lacks consistency between renewable energy and nature protection legislation and there is a coordination problem with regards to the permit processes of the development of renewable energy activities. These conclusions point towards a need for a broader perspective on the development of renewable energy activities, which could include: a more integrated planning system for renewable energy activities; exploring the use of derogation rules from the Water Framework Directive; and a more integrated EU renewable energy policy with specific sustainability criteria.
459

A numerical investigation into the effects of positioning and rotation on the performance of two vertical-axis hydrokinetic turbines

Soviak, Jody 14 September 2016 (has links)
Numerical simulation allows investigation into the influence of separation distance and rotation on the performance of two vertical-axis hydrokinetic turbines. Compu- tational fluid dynamics is applied to calulate the lift and drag coefficients acting upon interacting NACA 0021 turbine blades for a Reynolds number of Red = 10, 000. To understand the effect of separation distance, large-eddy simulation of the flow around side-by-side and staggered cylinders, ReD = 3,000, and airfoils, Rec = 3,000, are also performed. Based upon the simulations, a drag reduction of 11.3% and 19.8% is determined for the downstream cylinder and airfoil, respectively. A reduction in Reynolds stresses is also observed for the staggered configuration compared to the side-by-side configuration. Due to computational resources of large-eddy simulation, the Reynolds averaged Navier-Stokes method is also applied to investigate the influence of separation distance and rotation on two vertical axis hydrokinetic turbines. The numerical simulations show that a drag reduction of 15.5% occurs when the non-dimensional spanwise and streamwise separation distances, based on turbine diameter, reach 1 and 2, respectively. / October 2016
460

Enhancing performance of building integrated concentrating photovoltaic systems

Baig, Hasan January 2015 (has links)
Buildings both commercial and residential are the largest consumers of electricity. Integrating Photovoltaic technology in building architecture or Building Integrated Photovoltaics (BIPV) provides an effective means for meeting this huge energy demands and provides an energy hub at the place of its immediate requirement. However, this technology is challenged with problems like low efficiency and high cost. An effective way of improving the solar cell efficiency and reducing the cost of photovoltaic systems is either by reducing solar cell manufacturing cost or illuminating the solar cells with a higher light intensity than is naturally available by the use of optical concentrators which is also known as Concentrating Photovoltaic (CPV) technology. Integrating this technology in the architecture is referred as Building integrated Concentrating Photovoltaics (BICPV). This thesis presents a detailed performance analysis of different designs used as BICPV systems and proposes further advancements necessary for improving the system design and minimizing losses. The systems under study include a Dielectric Asymmetric Compound Parabolic Concentrator (DiACPC) designed for 2.8×, a three-dimensional Cross compound parabolic concentrator (3DCCPC) designed for 3.6× and a Square Elliptical Hyperbolic (SEH) concentrator designed for 6×. A detailed analysis procedure is presented showcasing the optical, electrical, thermal and overall analysis of these systems. A particular issue for CPV technology is the non-uniformity of the incident flux which tends to cause hot spots, current mismatch and reduce the overall efficiency of the system. Emphasis is placed on modelling the effects of non-uniformity while evaluating the performance of these systems. The optical analysis of the concentrators is carried out using ray tracing and finite element methods are employed to determine electrical and thermal performance of the system. Based on the optical analysis, the outgoing flux from the concentrators is predicted for different incident angles for each of the concentrators. A finite element model for the solar cell was developed to evaluate its electrical performance using the outputs obtained from the optical analysis. The model can also be applied for the optimization of the front grid pattern of Si Solar cells. The model is further coupled within the thermal analysis of the system, where the temperature of the solar cell is predicted under operating conditions and used to evaluate the overall performance under steady state conditions. During the analysis of the DiACPC it was found that the maximum cell temperature reached was 349.5 K under an incident solar radiation of 1000 W/m2. Results from the study carried on the 3DCCPC showed that a maximum cell temperature of 332 K is reached under normal incidence, this tends to bring down the overall power production by 14.6%. In the case of the SEH based system a maximum temperature of 319 K was observed on the solar cell surface under normal incidence. An average drop of 11.7% was found making the effective power ratio of the system 3.4. The non-uniformity introduced due to the concentrator profile causes hotspots in the BICPV system. The non-uniformity was found to reduce the efficiency of the solar cell in the range of 0.5-1 % in all the three studies. The overall performance can be improved by addressing losses occurring within different components of the system. It was found that optical losses occurred at the interface region formed due to the encapsulant spillage along the edges of the concentrator. Using a reflective film along the edge of the concentrating element was found to improve the optical efficiency of the system. Case studies highlighting the improvement are presented. A reflective film was attached along the interface region of the concentrator and the encapsulant. In the case of a DiACPC, an increase of 6% could be seen in the overall power production. Similar case study was performed for a 3DCCPC and a maximum of 6.7% was seen in the power output. To further improve the system performance a new design incorporating conjugate reflective-refractive device was evaluated. The device benefits from high optical efficiency due to the reflection and greater acceptance angle due to refraction. Finally, recommendations are made for development of a new generation of designs to be used in BiCPV applications. Efforts are made towards improving the overall performance and reducing the non-uniformity of the concentrated illumination.

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