• Energy Research

Las fuentes de energía renovables se han expandido considerablemente en los últimos años para abordar el creciente déficit de energía en los sistemas de energía modernos. La integración de estas fuentes plantea importantes preocupaciones para la gestión del sistema de energía, y las limitaciones transitorias de estabilidad de las redes son uno de los problemas crecientes para los ingenieros e investigadores. En este documento, se analiza el impacto de la integración de los Generadores de Inducción Doblemente Alimentados para examinar la estabilidad transitoria en dos modelos de prueba. Se explora un Índice de Fuerza de Acoplamiento formulado a partir de la Teoría de Características Estructurales de la Red para detectar la línea de transmisión más débil. Este método identifica la línea 7 a 8 y 5 a 6 como la línea más débil con un índice de resistencia de acoplamiento de 0.02739 y 0.105158 para el sistema de bus IEEE 9 y 39, respectivamente. Luego se investiga la estabilidad transitoria del sistema con y sin los Generadores de Inducción Doblemente Alimentados, considerando una falla de cortocircuito trifásico aplicada en el medio de la línea identificada. Se investigaron varias características asociadas con el sistema, como la velocidad del generador, el ángulo del rotor y la energía eléctrica. La simulación se llevó a cabo utilizando DIgSILENT Power Factory y los resultados indican que los sistemas se ven afectados negativamente por la integración de los generadores de inducción de doble alimentación. Les sources d'énergie renouvelables se sont considérablement développées ces dernières années pour remédier au déficit énergétique croissant des systèmes électriques modernes. L'intégration de ces sources soulève des préoccupations importantes pour la gestion du système d'alimentation, les contraintes de stabilité transitoire des réseaux étant l'un des problèmes croissants pour les ingénieurs et les chercheurs. Dans cet article, l'impact de l'intégration des générateurs à induction à double alimentation est analysé pour examiner la stabilité transitoire sur deux modèles de test. Un indice de force de couplage formulé à partir de la théorie des caractéristiques structurelles du réseau est exploré pour détecter la ligne de transmission la plus faible. Cette méthode identifie les lignes 7 à 8 et 5 à 6 comme la ligne la plus faible avec un indice de force de couplage de 0,02739 et 0,105158 pour les systèmes de bus IEEE 9 et 39, respectivement. La stabilité transitoire du système est ensuite étudiée avec et sans les générateurs à induction à alimentation double, en tenant compte d'un défaut de court-circuit triphasé appliqué au milieu de la ligne identifiée. Plusieurs caractéristiques associées au système, telles que la vitesse du générateur, l'angle du rotor et la puissance électrique, ont été étudiées. La simulation a été réalisée à l'aide de DIgSILENT Power Factory et les résultats indiquent que les systèmes sont impactés négativement par l'intégration de générateurs à induction à double alimentation. Renewable Energy Sources have considerably expanded in recent years to address the widening energy deficit in modern power systems. Integrating these sources raises significant concerns for power system management, with transient stability constraints of networks being one of the growing issues for engineers and researchers. In this paper, the impact of Doubly Fed Induction Generators integration is analyzed to examine the transient stability on two test models. A Coupling Strength Index formulated from Network Structural Characteristics Theory is explored to detect the weakest transmission line. This method identifies line 7 to 8 and 5 to 6 as the weakest line with coupling strength index of 0.02739 and 0.105158 for IEEE 9 and 39 bus system, respectively. The system's transient stability is then investigated with and without the Doubly Fed Induction Generators, considering a three-phase short-circuit fault applied at the middle of the identified line. Several characteristics associated with the system such as generator speed, rotor angle, and electric power were investigated. The simulation was carried out using DIgSILENT Power Factory and the results indicate that the systems are negatively impacted by the integration of Doubly Fed Induction Generators. توسعت مصادر الطاقة المتجددة بشكل كبير في السنوات الأخيرة لمعالجة العجز المتزايد في الطاقة في أنظمة الطاقة الحديثة. يثير دمج هذه المصادر مخاوف كبيرة لإدارة نظام الطاقة، حيث تعد قيود الاستقرار المؤقتة للشبكات واحدة من القضايا المتزايدة للمهندسين والباحثين. في هذه الورقة، يتم تحليل تأثير تكامل المولدات الحثية ذات التغذية المزدوجة لفحص الاستقرار العابر على نموذجي اختبار. يتم استكشاف مؤشر قوة الاقتران المصاغ من نظرية الخصائص الهيكلية للشبكة للكشف عن أضعف خط نقل. تحدد هذه الطريقة الخطوط من 7 إلى 8 ومن 5 إلى 6 على أنها أضعف خط مع مؤشر قوة اقتران 0.02739 و 0.105158 لنظام ناقل IEEE 9 و 39، على التوالي. ثم يتم التحقق من الاستقرار العابر للنظام مع وبدون المولدات الحثية ذات التغذية المزدوجة، مع الأخذ في الاعتبار وجود عطل في دائرة قصر ثلاثية الأطوار مطبقة في منتصف الخط المحدد. تم فحص العديد من الخصائص المرتبطة بالنظام مثل سرعة المولد وزاوية الدوار والطاقة الكهربائية. تم إجراء المحاكاة باستخدام مصنع ديجسيلنت للطاقة وتشير النتائج إلى أن الأنظمة تتأثر سلبًا بتكامل المولدات الحثية ذات التغذية المزدوجة.

Resolving imbalances on phases is performed using conventional trial and error approach which involves service interruption. Phase current and voltage may improve however the resultant effect does not last for too long. To improve the performance of the secondary distribution system there is a need for an on-line and automating technology. The aim of this paper is to pioneer a method and technology for resolving imbalances in a secondary distribution system as a result of the uneven distribution of single phase load across a three phase power system. The technology developed involves monitoring, acquisition/display of collected data and self changing switching actions electronically for rearrangement or transfer of consumer loads. The proposed switching technology is based on opentransition switch that enables transfer or rearrangement of consumer loads in a three-phase system within milliseconds with supervisory control system. Validation of the proposed technology was carried out using these methodologies: Matlab (Simulink), Virtual Instrumentation-Lab VIEW and Hardware implementation.

Abstract Occupant dynamic presence and characteristics associated with lighting loads/usage in residential buildings are not replicated in most practices currently adopted in modelling lighting profile. This study involves the use of adaptive neural fuzzy inference system (ANFIS) for lighting load profile prediction. Natural light, occupancy (active) and income level are the characterization (variables) factors considered in this investigation. The accuracy of the developed prediction models in relation to various income earners groups were analyzed using statistical measures; correlation output of the ANFIS approach and the impact of the characteristics on the lighting profile development in relation to trend analysis were also employed. Results obtained after validation of the developed models using investigative data, metering data and regression model showed a better correlation and root mean square error (RMSE) in comparison with actual values. The intelligence approach showed a better correlation of fit and good learning predictive accuracy in terms of behavioural and environmental variableness; and presents its output according to the complex nature of lighting usage in relation to the variables. The efficacy of the method was also validated.

Most polymer materials are thermal and electrical insulators, which have wide potential in advanced energy-power applications including energy conversion. However, polymers get softened when in contact with heat, which causes their molecular chains to flow as the temperature increases. Although polymer dielectrics exhibit high power density, they face challenges of low energy density which is due to the low dielectric permittivity associated with them. Therefore, this study tried to address the poor thermal energy management and low energy density of poly (vinylidene fluoride) (PVDF) while maintaining its flexible property using low content of hybrid carbon nanotubes (CNTs–0.05wt%, 0.1wt%) and boron nitride (BN–5wt%, 10wt%) nano-reinforcements. The nanocomposites were developed through solvent mixing and hot compression processes. The dielectric constant increased from 9.1 for the pure PVDF to 42.8 with a low loss of about 0.1 at 100 Hz for PVDF-0.1wt%CNTs-10wt%BN. The thermal stability of the nanocomposites was enhanced by 55°C compared to the pure PVDF. The nanocomposites also showed improved melting and crystallization temperatures. The developed PVDF-CNTs-BN nanocomposites showed significant enhancements in thermal energy management, stability, and dielectric properties. The significantly improved properties are credited to the synergetic effects between CNTs and BN in the PVDF matrix in promoting homogeneous dispersion, thermal barrier, interfacial polarization/bonding, insulative and conductive properties. Therefore, the developed nanomaterials in this study can find advanced applications in the energy-power sector owing to their enhanced performances.

Dye-sensitized solar cells (DSSCs) are characterized by several special attributes such as low cost, ease of fabrication, all year availability of sunlight, and capacity to operate under diffuse lighting conditions. However, their universal adoption is still restricted by a low efficiency photovoltaic output. Thus, this research seeks to explore avenues of present photon mitigation which could be corrected in future DSSC technology in order to improve on existing efficiency records. A preliminary phytochemical screening of Prunus dulcis (P. dulcis) leaf extract revealed a variety of chromophores which renders high possibility for charge transport. UV/VIS spectroscopy showed P. dulcis with peak absorbance wavelength within the visible region of the electromagnetic spectrum of light. Fourier transform infrared spectroscopy specifically highlighted the fingerprint of the chromophores present in this organic extract. Photovoltaic parameters such as short circuit current (Isc), open circuit voltage (Voc), maximum power (Pmax), fill factor (ff) and efficiency (ƞ) were the factors taken into consideration for the determination of the photovoltaic outcome. In P. dulcis DSSCs, KBr electrolyte recorded the best ƞ of 10.18%. However, P. dulcis DSSC with electrolyte KI indicated the best Isc, Voc and Pmax of 0.135 mA, 280 mV and 34.2 mW respectively. The similarity of this photovoltaic result with previous DSSC results necessitated further analysis. Consequently, scanning electron micrograph (SEM) of P. dulcis was modelled first with Gwyddion software and this output was analyzed with Excel and Origin programs. The outcome is a scientific discovery of electron tunneling in the P. dulcis shells, effect of dopant ions boosting the electrolytic Fermi level and a high probability of influencing the future efficiency outcome in P. dulcis DSSCs. Using mathematical algorithms from the Origin and Excel software applications, a direct function of the impact of doping, relative speed of electrolyte molecules as they percolate P. dulcis framework was obtained. Thus, the significance of this work lies in the relationship of behavioral dynamics of dopants to photovoltaic performance of P. dulcis. This indicates that a vital optical tunable characteristic of DSSCs lies in electrodynamics of dopant ions, which presents a viable prospect for application in DSSC technology research.

Load balancing on phases is performed using a conventional trial and error approach. With this approach, service interruption is unavoidable; hence rearrangement of consumers load distribution points on phases cannot be performed frequently. Also phase voltage and current imbalances might improve using this approach but the change does last for too long. To get the secondary distribution to operate at its optimal performance, a technique in the form of remote and automated technology is needed. This paper contributes such a technology at the low voltage side of the distribution network. The proposed static transfer switching technology is based on the open-transition switch that enables transfer or arrangement of consumer loads in a three-phase system within milliseconds and supervisory control system for effective co-ordination, computational and control of other intelligent units.

This paper focuses on the impact of Solar Water Heaters (SWH) at a higher institution of learning. An energy audit was conducted for the evaluation of the energy conservation measure: energy conoduction Energy is a key element in the development of any country or institution; as a result any shortage in energy will have a serious effect on the economy and social aspect of such country or institution. South Africa has, in recent years, experienced high economic growth as well as a rapid expansion in the elsumption analysis, correlation of consumption with weather; financial criteria, payback period and needed solar heater system (SWH) to determine the energy that may be termed as wastage or can be saved. The method of investigation includes assessment of the hot water usage within the institution campus and residencies, analysis of bills, metering and development of a software model for the analysis of energy use, system needed and environmental variables. This renewable measure (SWH) showed a high potential of energy and financial savings for higher education institutions especially those with residences.

National electricity supply utility in South Africa (Eskom) has been facing challenges to meet load demands in the country. The lack of generation equipment maintenance, increasing load demand and lack of new generation stations has left the country with a shortage of electricity supply that leads to load shedding. As a result, alternative renewable energy is required to supplement the national grid. Photovoltaic (PV) solar generation and wind farms are leading in this regard. Sunlight fluctuates throughout the day, thereby causing irradiation which in turn causes the output of the PV plant to become unstable and unreliable. As a result, storage facilities are required to mitigate challenges that come with the integration of PV into the grid or the use of PV independently, off the grid. The same storage system can also be used to supplement the power supply at night time when there is no sunlight and/or during peak hours when the demand is high. Although storage facilities are already in existence, it is important to research their range, applications, highlight new technologies and identify the best economical solution based on present and future plans. The study investigated an improved economic and technical storage system for generation of clean energy systems using solar/PV plants as the base to supplement the grid. In addition, the research aims to provide utilities with the information required for making storage facilities available with an emphasis on capital cost, implementation, operation and maintenance costs. The study solution is expected to be economical and technically proficient in terms of PV output stabilization and provision of extra capacity during peak times. The research technology’s focus includes different storage batteries, pumped storage and other forms of storage such as supercapacitors. The analysis or simulations were carried out using current analytic methods and software, such as HOMER Pro®. The end results provide the power utility in South Africa and abroad with options for energy storage facilities that could stabilise output demand, increase generation capacity and provide backup power. Consumers would have access to power most of the time, thereby reducing generation constraints and eventually the monthly cost of electricity due to renewable energies’ accessibility. Increased access to electricity will contribute to socio-economic development in the country. The proposed solution is environmentally friendly and would alleviate the present crisis of load shedding due to the imbalance of high demand to lower generations.