• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 261
  • 100
  • 57
  • 35
  • 33
  • 27
  • 9
  • 6
  • 6
  • 6
  • 6
  • 6
  • 5
  • 5
  • 4
  • Tagged with
  • 644
  • 644
  • 644
  • 194
  • 95
  • 94
  • 85
  • 84
  • 82
  • 81
  • 71
  • 68
  • 63
  • 62
  • 62
  • 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.
131

Právní úprava obnovitelných zdrojů energie a jejich využívání / Legal regulation of the renewable energy resources and their use

Makovec, Václav January 2013 (has links)
Title: Legislation of renewable energy sources and their use Abstract The presented thesis deals with issues of legal regulation of renewable energy sources with target on legal regulation of system of support in the Czech Republic. The thesis contains the overview of documents and instruments from international enviroment. As a result of the Czech Republic membership in the European Union the thesis presents instruments of union legislation which due to integration of EU member states legislation and due to marking out obligatory goals aims to opened unified and liberal energy market. The thesis describes historical development of this phenomenon from partial legislation to complex and sophisticated legislation and artificially formed systems of support including and puts them into context with social economic aspects of pursued period of time. Due to comparative method the thesis brings not only comparation of legislation in the course of time in Czech and European background but also evaluate them and try to estimate progress and find possible solution. One of the thesis targets is to provide the comprehensive view on legislation of renewable energy sources from businessmen points of view and put this relationship into context with institute of environment protection.
132

Právní úprava využívání alternativních zdrojů energie / Legal regulation of the use of alternative energy resources

Výmola, Lukáš January 2013 (has links)
Thesis title: Legal regulation of the use of alternative energy resources The goal of the paper is to analyze the legal regulation of the use of alternative energy sources and to provide a summary and logical overview of this matter that is closely related to environment and climate protection. The greenhouse effect is frequent topic of current debates regarding the climate changes that lead the international communities to decision on limitation of greenhouse gases emissions by using among others renewable energy sources. The reason for my research is a long-term interest in renewable energy sources. The thesis is composed of seven chapters, each of them dealing with different aspects of promotion of the use of alternative energy sources. Chapter One is introductory and provides the overview of the research topic. Chapter Two explains the term alternative energy sources and its relation to renewable energy sources. Chapter Three is divided into two subchapters dealing with international and European aspects of the climate protection and related law. History of the Czech legal regulation of promotion of renewable energy sources is provided in Chapter Four and the main issues are outlined. Chapter Five deals with current Czech legal regulation on promotion of renewable energy sources and provides...
133

Právní úprava využívání alternativních zdrojů energie / Legal regulation of the use of alternative energy resources

Malimánková, Barbora January 2013 (has links)
This thesis is focused on the legislation on the renewable energy sources, especially on the mechanisms of promotion granted to the producers of the electricity and heat from the renewable sources of energy. The thesis describes the contemporary regulation in the Czech republic and compares it to the relevant German regulation.
134

Solar energy technology road map developing a local supply chain in South Africa for concentrated solar power plant

16 September 2015 (has links)
M.Ing. / The necessity for deployment of Concentrated Solar Power (CSP) technology in the South African energy sector is examined in this dissertation. A background is given on the different technologies that exist in the solar power sector with specific reference to Concentrated Solar Thermal Power (CSTP). The economic, social and environmental benefits that this technology embodies in the near-, medium-, and long-term is discussed in detail. It highlights the local market potential for the establishment and large-scale roll out of CSP technology in a South African context and the economic value-chain that could subsequently be created...
135

Vliv schválení srážkové daně na fotovoltaický projekty v ČR / The impact of additional taxation on photovoltaic projects in the Czech Republic

Zejval, Tomáš January 2011 (has links)
The master thesis is concerned with the problems of the impact of additional taxation on economy and effectiveness of photovoltaic projects in the Czech Republic. Additional taxation applies to revenues coming from selling the electricity made by photovoltaic power plants between 2011 and 2013. The first part describes the theoretical factors influencing the methods of assessing the effectiveness of the investment project. At the beginning of the second part, the legislative background of renewable energy projects in the Czech Republic is described. All the factors influencing the effectiveness of the photovoltaic projects are reviewed; followed by the discussion of methods for assessing the effectiveness of the photovoltaic projects. At the end of the thesis the impact of additional taxation on the effectiveness of photovoltaic projects is assessed and compared between different sizes of projects.
136

Projektové financovanie v oblasti obnovitelných zdrojov energie / Project finance renewable energy sources

Minarič, Matúš January 2010 (has links)
Definition of project financing on real project of renewable energy source.
137

Projekt výstavby fotovoltaickej elektrárne / Project of the construction photovoltaic power plant

Mačugová, Radana January 2010 (has links)
The objective of this thesis is to analyze and evaluate the profitability of photovoltaic power plant construction project. The introductory part deals with general characteristics of solar energy and its utilization, with the Slovakian and the European legislation in connection with use of renewable energy resources. The practical part deals with solar energy from the perspective of private firm. One particular company is considering about the implementation of photovoltaic power plant. This section begins with the presentation of the private company and evaluation of its preconditions for this planned construction. The thesis also describes planned implementation of the project, namely its preparation, possibilities of obtaining funds, necessary communication with the public agencies, selection of technology and the construction itself. At the end is project evaluated from the point of profitability by selected indicators.
138

Investigating the feasibility & impact of a solar array for Wits West Campus by using historical solar and power data

Singh, Ajeshni January 2016 (has links)
Master of Science in Engineering (Electrical) University of the Witwatersrand July, 2016 / This dissertation uses historical electrical consumption/load and actual solar radiation data to design a solar array for the University of the Witwatersrand’s West Campus. The array must meet the campus’s minimum demand as selling excess generated power back to the utility is not possible at this stage. The financial and spatial impact of adjusting the size of the array, design losses and cloud cover are also investigated. In addition to this, the influence on the payback period of financial variables such as taxes, electricity and start-up costs are also explored. The solar array system design process starts by determining the amount of power that the array must produce or supplement. Thereafter, load estimates and electrical consumption figures that are provided by utility bills or measured with load monitoring equipment are analysed. Furthermore, system losses are factored in which ultimately increases the size of the array. Once all the input variables are analysed, the amount of available solar radiation in the area where the array will be installed is required to determine the amount of energy that the array can produce. Several free databases with this information are available but it is found that this data over predicts the availability of solar radiation. The University has been monitoring the electrical consumption of West Campus since 2012 and solar radiation data is also available for this site. Comparing the satellite derived and measured datasets found that the ground monitored data is 25 % more accurate and therefore better suited for designing a solar array. Individually adjusting the design and financial variables changes the payback period between 3 – 17 %. Combining all the variables can reduce the payback of option 1 from 9.6 years to 6.1 years. Clear legislation needs to be developed for the uptake of renewable energy resources and supported by better rebates for renewable users and harsher taxes for non-renewable users. Should legislation change and if additional capital is available, a larger array will benefit the University more and should be installed as the difference between payback periods is not significant. This is mainly due to decreased costs associated with a higher yield. The financial benefits of a larger array will also be more lucrative if better rebates are enforced. / MT2017
139

Investigation into the steady-state load sharing of weak sources in a low voltage three-phase islanded microgrid

Wu, Meng-Chun Merelda January 2016 (has links)
A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in ful lment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2016 / This research investigates the power sharing between distributed energy resources with voltage and frequency droop control. A case study based on voltage sources in an islanded microgrid is set up in the laboratory, referred to as: The Example Microgrid. The Example Microgrid consists of two synchronous generators, active and reactive power loads. A simulation model is constructed based on the laboratory set-up, where componentwise and system-wise testing are completed. The simulation results are validated with the experimental set-up, and it is concluded that the model accurately represents the physical system under steady-state conditions. Further simulation studies on conventional droop controllers are conducted based on the Example Microgrid model. The results indicate that the use of conventional droop control is inappropriate for small, low-voltage islanded microgrids. As a possible application of this work, three variations of adapted droop controllers are simulated and their performance evaluated. It is found that with the adapted droop controllers, the power sharing error can be minimised / M T 2016
140

Transesterification of animal fat to biodiesel over solid hydroxy sodalite catalyst in a batch reactor

Makgaba, Chabisha Precious January 2017 (has links)
A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering September 2017 / Owing to the ongoing advancement in technology, escalating population sizes and urbanization rate, fossil fuels (coal, petroleum oil and natural gas) remain attractive as an energy source to run most of the daily operations. Consequent to heavy consumption of fossil fuels, the world faces detrimental challenges such as future energy security and environmental concerns. Combustion of fossil fuels results in emission of greenhouse gases such as CO2 and SO2 thereby contributing to global warming and acid rain problems. These alarming challenges drive the need for exploration of alternative energy sources to reduce dependence on fossil fuels. Presented in this dissertation is a study of biodiesel, a biodegradable, non-toxic and environmentally benign energy source as an alternative to petroleum-based fuels. Chemically known as fatty acid alkyl ester (FAAE), biodiesel is commonly produced from vegetable oils or animal fats in addition to methanol by a catalysed transesterification reaction. Currently, biodiesel is more expensive than petroleum diesel due to high operation costs incurred during the production process. Despite the high prices, biodiesel production continues to grow on an industrial scale across the world as supported by policy measures and biofuel targets. Researchers have identified two main factors that contribute to high costs of biodiesel production; 1) type of feedstock and 2) type of catalyst used in the production process. Conventional methods of production use edible oils as feedstock. This becomes unjustified due to the potential price hikes in the food market owing to the prospective competition between fuel and food industries. As a result, numerous researchers reported on the use of cheap and non- edible feedstock oils such as waste cooking oil and animal fat. However, the challenge with the use of non-edible oils is their high content of free fatty acids (FFA) which is unattractive for a smooth transesterification process, more especially when homogeneous base catalysts are used. Homogeneous base catalysts are widely used in current industrial biodiesel production methods because they yield faster transesterification processes due to increased reaction rates. However, these types of catalysts are much sensitive to FFA, so when high FFA content feedstock is used, a saponification reaction occurs which consequently reduces the yield of biodiesel. An additional process unit is required to reduce the FFA content via esterification process prior to the main transesterification reaction. Furthermore, since the reaction mixture is homogeneously combined with the product, an additional process unit for product separation is required to recover the resulting biodiesel from the mixture, translating into additional production costs. Researchers are currently exploring the use of heterogeneous catalysts, which tend to avoid the saponification reaction and reduce the need for an esterification reaction used as oil pre-treatment step to reduce FFA content. This dissertation is therefore dedicated to attaining a economic and environmentally attractive process for biodiesel production using cheap non-edible beef tallow oil (BTO) and a heterogeneous hydroxy sodalite (H-SOD) catalyst. Some industrial operations such as zeolite manufacturing processes produce a low grade H-SOD as by products, which is in turn disposed as chemical waste and therefore induces ground water contamination concerns. Exploration on the use of H-SOD as catalyst can largely contribute to the environmental protective measures as a waste management process among other benefits. The use of H-SOD is extensively reported in current research development on membrane separation; limited research reports on the use of H-SOD material to catalyse chemical processes are present in literature. For the first time in open literature, H-SOD is reported as the solid catalyst for biodiesel production in this dissertation. The investigative study commenced with a preliminary study to gauge the feasibility of using H-SOD as a catalyst where a batch transesterification of waste cooking oil (WCO) was studied. The reaction was conducted at 60 ᵒC for 12 h at a methanol-to-WCO ratio of 7.5:1 using 3 wt. % H-SOD catalyst with a particle size of just below 300 Å, the stirring intensity was kept at 1000 rpm to ensure uniform mixing throughout the reaction. The product obtained after the reaction was analysed using a pre-calibrated Chromatography-Mass Spectrometer (GC-MS) described in Chapter 5, and the results demonstrated the possibility of catalysing a transesterification reaction using solid H-SOD. Under the same reaction conditions, the study was then extended to an investigation on the use of H-SOD to catalyze transesterification of BTO (4.53 % FFA) to FAME. The results showed that FAME was produced, at a yield of 39.6% and a conversion of 68.4%. Seeing that the yield and conversion obtained is relatively small compared to literature findings, the effect of some process conditions on the conversion and biodiesel yield were studied. The transesterification reaction was conducted with variations in the mixing intensity (700 – 1250 rpm), catalyst particle size (200 – 300 Å), reaction time (6 – 24 h) and reaction temperature (40-60 °C). The maximum performance of H-SOD catalyst for a transesterification of BTO was achieved with a conversion of 78.3% and biodiesel yield of 62.9% obtained at optimum conditions: a stirrer speed of 1000 rpm, with the smallest catalyst particle size of 200 Å at maximum temperature of 60 °C and 24 h reaction time. The values of activation energy, reaction constants and frequency factor obtained from the kinetic study were 0.0011 min-1, 5.52 x108 min-1 and 79.20 kJ/mol, respectively, and are within the range of the results reported in literature. As a result, solid H-SOD is recommended as a catalyst for the batch transesterification of BTO in a biodiesel production process. / MT2018

Page generated in 0.0311 seconds