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- PublicationAnalysis of induction generator controller techniques for Pico hydropower - a case study of a 3kW Pico hydropower scheme in Kasese, Western Uganda(2014) Izael Da Silva; Teddy Nalubega; Okou Richard; Mary Suzan Abbo; Da Silva, IzaelThis paper presents a comparative analysis of control techniques used on induction generators for stand-alone Pico hydropower schemes. The techniques were tested on a prototype Pico hydropower system modeled for the site developed in western Uganda by the Centre for Research in Energy and Energy Conservation. The case study scheme to date is manually operated, a process that requires constant attention due to variations in load. This demonstrated the need for an automatic load controller. The site specifications were considered when designing models using Matlab simulink employing the automatic load control techniques. These model designs are simple so that it is affordable for local practical application. The proposed designed control techniques presented in this paper are composed of logic gates, IGBT switch, uncontrolled diode rectifier, the PID controller and other semiconductor devices supplying an electrical load and a ballast load. In addition, the response of the case study site and the Matlab model to load variations is presented.
- PublicationComparative performane analysis of a solar box cooker and improved charcoal stoves in Mozambique(International Solar Energy Society, 2014-09) Da Silva, I. P.; Cuamba, B. C; Nhabetse, M. T.; Da Silva, IzaelWith exception of South Africa, where only 16% of the population depends on traditional biomass energy, almost 80% of the population in the sub-Saharan Africa depends on biomass resources for cooking and heating. The burning of traditional biomass in the so-called three stones stove puts pressure on biomass resources because of its inefficiency. Besides, fumes and soot are related to respiratory diseases that are the common cause for deaths among women and children in Africa. The shortage of fire wood makes women and girls to walk in search of fuel for cooking. Solar cooking is one of the possible solutions for this poignant problem. Yet another partial solution is the use of improved biomass stoves. This paper presents a comparative analysis of the performance of solar box cooker and improved charcoal stove in Mozambique, in its technical and economic aspects.
- PublicationInductive Voltage Transformers Calibration by the Parameters(WSEAS, 2010) Brandao, F.A; Da Silva, I. P.; Demetri, I.; De Silos, A. C.; Diaz, E. M; Da Silva, IzaelThe accuracy class of an IVT - Inductive Voltage Transformer - is typically assessed in laboratory installations either by comparing with another IVT presenting greater accuracy and traceable to a national laboratory or by using a capacitive divider. Calibration in the field using internal parameters is considered herein, using results obtained from typical open and short circuit tests and winding resistances, performed with common meters. A Möllinger & Gewecke graphic diagram is employed together with the results of an accuracy test previously carried out to determine the exact value of the winding turn relation and of the primary winding dispersion reactance. These values are used to calculate the phase and ratio errors, which must lie between definite limits, defined by the accuracy class of the instrument. Four commercial IVTs were tested to determine the validity of the procedure. The errors are compared with those obtained with the Schering-Alberti method (AC Bridge and comparison with standard IVT).
- PublicationEconomics of a Gasification Based Mini Grid - a case study of a 10 kW Unit in Uganda(2007-01) Da Silva, I. P.; Buchholz, T.; Volk, T; Tennigkeit, T; Da Silva, IzaelSmall-scale wood gasification systems have the potential to contribute to the rural electrification in Uganda. This paper presents an economic analysis of a 10 kW gasifier unit and its minigrid installed on a Ugandan farm. The bioenergy system has been running stable on a six hour daily base for seven months. When the gasifier is operated close to the rated capacity, the gasifier system is economically attractive compared to diesel generated electricity Results indicate that replicating successful wood gasification systems stipulates integration of sustainable fuelwood supply and viable business models.
- PublicationOn Site Calibration of Inductive Voltage Transformers(WSEAS, 2009) Da Silva, I. P.; Demetri, I.; De Silos, A. C.; Brandao, F. A (Jr); Da Silva, IzaelThe accuracy class of an IVT – Inductive Voltage Transformer – is typically assessed in laboratory installations either by comparing with another IVT presenting greater accuracy and traceable to a national laboratory or by using a capacitive divider. Calibration in the field is considered herein, using results obtained from typical open and short circuit tests and winding resistances, performed with common meters. A Möllinger & Gewecke graphic diagram is employed together with the results of an accuracy test previously carried out to determine the exact value of the winding turn relation and of the primary winding dispersion reactance. These values are used to calculate the phase and ratio errors, which must lie between definite limits, defined by the accuracy class of the instrument. Four commercial IVTs were tested to determine the validity of the procedure. The errors are compared with those obtained with the Schering-Alberti method (AC Bridge and comparison with standard IVT)