1,721,015 research outputs found
A load management system for fixed appliances in a safe DC RDP house
No full textThesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2017.This dissertation represents the design and development of a load management system for fixed appliances in a safe direct current (DC) Reconstruction and Development Programme (RDP) house. A combination of valley filling, load shifting and peak clipping load management techniques were employed to assist in reducing the peaks observed in the RDP house load profile during peak hours.
A DC RDP house laboratory model was developed. The study is based on the assumption that the normally 220 V alternative current (AC) grid is replaced by a 350 V DC grid. The assumption is thus that 350 V DC is available at the distribution box in the RDP house laboratory model. All theoretical work was based on a 350 V DC system, but due to the lack of a laboratory 350 V DC supply, all physical tests were conducted by making use of a 300 V DC supply which was available. Consequently all calculations were thus based on 300 V DC as well.
The geyser was the main fixed appliance focused on since it contributes to a significant portion of the power used. An AC geyser was successfully modified in order to be used in the DC network. Safety of the system was considered in order to interrupt the power in case of overcurrent or to isolate the power. Electronic switches were also developed and implemented to ensure that the DC power could be safely switched on and off and that the low power DC was isolated from the high power DC.
LabVIEW allowed all other appliances in the DC RDP house to be virtually represented so that a holistic view of the power use of the house could be represented. This also allowed the system to be successfully simulated before any physical work was conducted.
The load management system was successfully implemented by making use of power line communication. This proved to be a cost effective means to apply the load management algorithm. The algorithm consisted mainly of power on / off instructions that were executed during peak and off-peak times. It follows the normal use of timers used in the AC system to help reduce demand.
It was found that the load management system successfully reduced the demand during peak hours without compromising the basic needs of the user. The power line communication modem proved to be very reliable in implementing the load management algorithm
Low cost, energy efficient, robust and multi-functional smart meter
No full textThesis (Master of Engineering (Electrical Engineering))--Cape Peninsula University of Technology, 2019The problem of assigning human operators to collect energy measurements from the conventional meters in the communities has become a great concern over the past decades. . Most times, the lives of these workers are in danger due to criminal activities within the communities, especially in this part of the world. During the collection process, data collected were inadequate due to factors such as bad weather, constant attacks on operators, inability to correct faults, and other factors that rendered the system highly inadequate. However, the rapid growth in population and industrial development has increased the demand for more human operators and longer working hours. The problem of disconnecting and reconnecting supply by utilities due to unpaid bills is considered problematic. In addition, the technology of metering has improved as research increases in the area of modifying old power grid into smart grid. Due to recent developments, old power grid is transformed into micro-grid, which makes all generating sources into one cluster cell. However, this cannot be achieved if there is no better way of metering; thus, the need for a smart meter becomes necessary. The smart meter is more reliable and efficient. It is an improved automatic meter reading (AMR) system. This research demonstrated that a simple low cost, energy efficient, robust, and multifunctional smart meter can be achieved. The smart meter system has added features that enabled the utilities to recover the meter energy measurement data remotely such as Zig-bee, Wi-Max, and Wi-Fi, (GSM) based to mention a few. The system allows monitoring and transmission of energy consumed in real-time. It calculates the amount of energy consumed through the multiplication of voltage and current signals. This system considers the use of ATmega358 on Arduino Uno board as the controlling unit for the execution of control and monitoring of activities. A standard electrical measurement such as current, voltage, power and energy consumption will be displayed via liquid crystal display (LCD). The external communication device is required in the actualization of this project, in-conjunction with the control unit based on the existing mobile technology called "GSM". This enhances accessibility of all sundries through effective measurement and collection of electric energy data generated with ATmega358 on Arduino Uno board. Therefore, GSM stands as intermediary between the nearby available utility station and consumers or end-users. In conclusion, LCD displays real-time based data for the end user to visualise. This proposed system consists of the energy meter called ATmega358 on Arduino Uno board programmed with "Arduino 1.8.7" as the program complier. The usage data billing is done within the interval of 30 seconds, stored and trans-received the process for data collection, storing and billing generation
Reconfigurable photovoltaic modules for robust nanosatellite power systems
No full textThesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2018.Until recently, the focus of most solar technology development for space was towards more efficient, more radiation-resistant and increasingly powerful arrays. During a space mission, solar cells are not only exposed to irradiation by electrons, but also to a range of other particles, like protons. Thus, solar cells on robust nanosatellites are extremely exposed to an environment, which includes the high-energy electrons and protons of the earth’s radiation belts, which leads towards the degradation process of the individual solar cell. Solar cell radiation shielding design ensures the protection of the solar cells from the particular radiation environment found in space. While the design principles of a solar photovoltaic automatic switching fault tolerant system which can detect and bypass faulty photovoltaic cells will be presented through this research work. The ability of such a system to be reconfigured using implemented switching matrix system makes it efficient under various environments and faulty conditions.National Research Foundation (NRF
Useful energy utilisation of integrated solar PV and thermal module with storage device
No full textThesis (PhD (Electrical Engineering))--Cape Peninsula University of Technology, 2019Lack of electrical energy has always been an issue for human society development. Several studies point out the expansion and integration of renewable energies into the society to solve the energy crisis. Renewable energies promote sustainable energy development, environmental, social, and economic sustainability throughout their life cycle. The integration of renewable energies, especially in the area of the photovoltaic technology becomes important, as it demotes the rates of consumption of non-renewable resources, therefore, decreasing the fossil fuels dependencies. A photovoltaic system has a low output conversion rate. Integrating photovoltaic and thermal (PV/T) system can improve the photovoltaic conversion efficiency. However, the overall efficiency of the PV/T is always compromised as one of the sub-system performance might overtake the other. This research work is developed to enhance the knowledge of the thermal performance of photovoltaic models and also offered alternatives to improve and co-generate thermal and electrical energy. The purpose of the proposed PV/T model is to analyse the cooling method and the possibility of partially converting photovoltaic electrical energy into useful heat source (for hot water). The working fluid plays the role of cooling the PV cells, therefore, boosting the PV cell performance. The working fluid would collect the useful heat energy through the pipes in a closed loop attached at the back of the PV panel. The study also is aimed at proposing automated intelligent solutions for energy management to adjust the useful heat transfer capacity to working fluid based on energy demand and weather conditions to balance the thermal and electrical energy. The overall research method was based on a theoretical analysis, the review of essential articles, the design of the most appropriate concepts, mathematical modelling and analysis of the proposed PV/T system. Also, an adequate control strategy based on the energy management algorithm to provide multi-functional energy performance was established to prioritise the energy balance according to demand. The simulation model of the PV/T system was developed with MATLAB/Simulink software to predict system performance with reasonable accuracy and to analyse the main phenomena related to thermal behaviour. The simulation result of the proposed PV/T model under different operational conditions evaluated the cooling the PV cells and heating the working fluid. The outcomes turned out to be productive and cost-effective. Also, the PV modules can yield better electrical energy performance due to the cooling effect of the PV cells. The results revealed that the proposed system met cooling and heating based on the demands
Impacts of Electricity Rates on the Economics of Rooftop PV System
Get PDFThe huge negative environmental impacts of usingfossil fuel-based electricity generation systems is widely visible interms of air pollutions, greenhouse gas emissions induced climatechange, and skyrocketing of electricity prices while the resourceis continuously being depleted. Using renewable energy sourcesuch as solar energy will surely reduce the negative impacts ofconventional fuels used for electricity generation.Mitigating the negative impact of the traditional energysources usage for the production of electricity needs a concertedeffort of all inhabitants of the planet Earth. Renewable energysources such as wind and solar have recently been seen assaviours. While the technical possibility and their readiness areseen as non-barriers to their deployment, one major barrier thatrecently has been showing up is the economical comparison oftheir economics with grid electricity where and when it isavailable. The premium is still acceptable for having a standalonePV system where grid electricity is not reachable. The economicsanalysis of such standalone system can easily been computed asthere are less dynamics involved. The case is a bit complicatedwhere the PV system is grid-tied and bidirectional energyexchange with the grid is allowable. Dynamics such as feed-intariffs, time of use tariffs, block tariffs et cetera makes theeconomics analysis of grid-tied energy systems complicated tomodel, analyse, and optimise. Net present cost as an economicindicator of technical feasible grid-tied energy system is used toassess the economic viability using HOMER software. Differentscenarios are evaluated with fixed electricity rate but withdifferent sellback prices
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
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