1,720,982 research outputs found
Automated hybrid solar and mains system for peak time power demand.
Get PDFMaster of Science in Electrical Engineering.The power demand during peak period causes large power fluctuations in the commercial grid. The reduction in using grid supply during peak time benefits the supplier and consumer. There are many methods such as monitoring the usage of grid supply, load shedding, using local generators and disconnecting unwanted loads during peak time used to reduce grid dependency during peak time. These methods reduce power demand from grid by either supplying interrupted power to the load or by establishing additional power source. In South Africa, solar energy is abundantly available and it can be utilized to solve the power demand during peak time. In this research, solar and grid power are chosen as two power sources and automatic switching system to select the power source to supply uninterrupted power to the load is designed. The important aspect of using solar system is estimating the system output. The maximum power point tracking system using perturb and observe algorithm is designed. The boost converter and inverter circuits are designed to supply power to the coffee shop loads at Howard College Campus. Battery charger circuit is designed to charge the battery from solar or grid and supply power to the load whenever required. The switching algorithm connects the load to solar or battery during peak time and connects it to grid during off peak time. The switching algorithm is designed to supply uninterrupted power to the load by connecting it to available source when any one of the source failure occurs. The power output from the panel is maximized by automatic panel cleaning system. The panel cleaning starts at the pre-programmed schedule and provision for manual override option to reschedule panel cleaning operation is also provided. The designed system is tested in MATLAB and Proteus simulation software. The results of each section are discussed. It can be seen that designed automatic selection of power sources for supplying 1kW of power during peak time to the selected coffee shop considerably reduces the cost and power demand from the grid during peak time. The designed system is economically feasible and efficient in supplying uninterrupted power to the load
Smart induction cooking system using solar energy.
Get PDFMasters Degree. University of KwaZulu-Natal, Durban.Solar energy presents a good, clean and a reliable source of energy for the future. The focus includes the department of energy strategy (DoE) to allow solar renewables appliances to grow and contribute to the country’s economy and global environment. This study uses the recent advantage of induction cooking methods in the market to apply more efficient and economical techniques that go in line with the future wishes in the energy sector. Induction cooker is proven to transfer at least 80 % of the power generated to the pot, while electric stove and gas burners generate more to compensate for the power that is transferred to the atmosphere in the form of heat (i.e. about 55 % efficient). The induction cooker is currently presenting best cooking technology thus far. Though all including induction cooker are completely dependent on the grid power. The research comes with the idea of solar energy to fill the big existing gap of completely depending on non-renewable resources. The advantage comes with the idea of making the product a completely standalone, reducing electricity bills, simple and reliable, no fuel costs and spills, flexible in power sources, sustainable development etc. The proposed cooking technology is improved version and it gives more in the customer needs with regard to clean system, ease to use, conservation and price. Though initial system installation price is high but after five years, the user will be saving a large amount of money. The research will improve the annual savings by 45 % as per the DoE analysis in the comparison of cooking technologies. The thesis focuses on the solar as a primary source of energy to promote savings. The grid power is still used as a backup power source as we are not yet 100 % green but gradually adjusting. The design uses the power auto switching method to treat solar power as a primary source of supply and mains to be the system backup. The cooker battery storage is charged by the solar using efficient MPPT technology and supply the stove at the same time. The mains only take over when the solar is completely not available for some time and it will supply the cooker directly via AC to DC power supply unit and also charges the battery storage via AC to DC battery charger. All the above switching is programmed and happens automatically via remote programmable relay. System design includes theoretical background in the form of circuit analysis, power flow and mathematical calculations.
The simulation and practical results present eight different power levels that are displayed in the liquid crystal display (LCD) in the form of switching frequency and power consumed by the load. The power mathematical calculations, Simulations and practical results analysis show a similar trend. The pot material is kept constant while changing switching frequency to achieve desired outputs. Theoretical and simulations are in line while practical differ slightly due to many factors like component internal resistances, conductors used and component internal circuit topology. The other adjustments in practical includes a smaller scale of power (600 watts maximum) compared to simulations due to safety reasons on my capacity to implement a prototype and proving the working of the study at a smaller scale which can be extended if required. The general and specific objectives of the study are achieved in simulations and practical though some adjustments were made during practical in order to me general and specific objectives. The study proves the theory of energy savings, being standalone product in the practical results analysis and thus presents many advantages in the commercial sector for the future
Small signal stability analysis of a voltage source converter (VSC) based high voltage direct current system with onshore wind power generation.
Get PDFMasters Degree. University of KwaZulu-Natal, Pietermaritzburg.Advances in power electronics over several decades has led to high voltage direct current (HVDC) transmission emerging as a good option for electricity transmission in many circumstances, and it is able to integrate with, and augment, conventional high voltage alternating current (HVAC) transmission. This is because HVDC provides enhanced system operation and improved support in the development of onshore and offshore transmission networks. Because of its speed and flexibility, HVDC technology can provide transmission systems with several advantages such as transfer capacity enhancement, better power flow control, transient stability improvement, damping of power oscillations, enhanced voltage stability and control, rejection of cascading disturbances, and the absence of reactive power generation or absorption by the cable or line.
In Africa, there are three HVDC systems. The Caprivi Link Interconnector between Zambia and Namibia is the first and only one on the continent employing voltage source converters (VSC), as opposed to conventional line commutated converters (LCC). HVDC VSCs use insulated gate bipolar transistors (IGBTs) technology as switches. IGBTs provide more controllability and flexibility than the thyristors used in LCC technology. These features make them suitable for implementation in multi-terminal HVDC networks; which are envisaged to form HVDC grids in future. The Caprivi Link interconnector is therefore a pioneering project in the development of electricity transmission in Africa. The southern African power pool (SAPP) currently has inadequate electricity generation capacity. Investing in more renewable energy options, such as wind generation, coupled with the use of HVDC transmission, could be possible remedies for this.
The aim of this research was to investigate small signal stability issues that can be present in VSC-HVDC systems. The Caprivi Link Interconnector is used as the contextualization of the investigated system. Different conditions such as AC system strength, controller parameter and wind power generation levels are investigated for their influence on the small signal stability of the system. Small signal stability analysis is also investigated for different HVDC configurations. It is found that the systems experience both electromagnetic as well as sub-synchronous oscillations. The sub-synchronous oscillations are generally well damped and only affect the DC impedances. Power System Stabilizers (PSS) as well as Thyristor Controlled Series Compensators (TCSC) are implemented as mitigation for the electromagnetic modes
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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