Browsing by Author "Lugujjo, Eriabu"

Now showing 1 - 5 of 5
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    Formation of silicon oxide over gold layers on silicon substrates
    (Journal of Applied Physics, 2003) Hiraki, Akio; Lugujjo, Eriabu; Mayer, J. W.
    When a single‐crystal substrate of silicon is covered with evaporated gold and heated at relatively low temperatures (100–300°C) in an oxidizing atmosphere, a silicon‐dioxide layer is readily formed over the gold layer. The mechanism and factors controlling this low‐temperature oxide formation have been investigated using backscattering of 2‐MeV He+ ions. The oxide layer is nonuniform in thickness and the initial growth of this layer is proportional to (time)1/2. Both oxidizing ambient and orientation of the substrate influence the growth rate, and the amount of gold determines the final thickness of oxide. A model is proposed to explain the oxide‐growth mechanism.
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    A Heuristic Model for Planning of Single Wire Earth Return Power Distribution Systems
    (Bakkabulindi, G., Hesamzadeh, M. R., Amelin, M., Da Silva, I. P., & Lugujjo, E. (2011)., 2011) Bakkabulindi, Geofrey; Hesamzadeh2, Mohammad R.; Amelin, Mikael; Silva, Izael P. Da; Lugujjo, Eriabu
    The planning of distribution networks with earth return is highly dependent on the ground’s electrical properties. This study incorporates a load flow algorithm for Single Wire Earth Return (SWER) networks into the planning of such systems. The earth’s variable conductive properties are modelled into the load flow algorithm and the model considers load growth over different time periods. It includes optimal conductor selection for the SWER system and can also be used to forecast when an initially selected conductor will need to be upgraded. The planning procedure is based on indices derived through an iterative heuristic process that aims to minimise losses and investment costs subject to load flow constraints. A case study in Uganda is used to test the model’s practical application.
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    Low-Temperature Migration of Silicon in Metal Films on Silicon Substrates Studied by Backscattering Techniques
    (Journal of Vacuum Science and Technology, 2000) Hiraki, Akio; Lugujjo, Eriabu
    The backscattering method using 2-MeV4He+ ions is employed to obtain microscopic information about solid-solid reaction of Si with thin layers (200∼4000 Å) of Au, Ag, and Al which are vacuum evaporated onto Si crystal substrates. The interesting observation is the migration of Si atoms into these metal films at temperatures (for example, 150°C in Au, 400°C in Ag) well below their eutectic points (375°C for Au and 850°C for Ag). This phenomenon also indicates that at these low temperatures the dislodgment of Si atoms from tightly bound Si crystal does occur. Our experiments clarify that the origin of this effect is the interaction of Si with metals at the interface.
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    Rural Electrification Practicalities of Using Single Wire Earth Return as a Low-Cost Method for Grid Extension: The Case of Ntenjeru, Uganda
    (Bakkabulindi, G., Da Silva, I. P., & Lugujjo, E. (2009, August), 2009) Bakkabulindi, Geofrey; Silva, Izael P. Da; Lugujjo, Eriabu; Söder, Lennart; Amelin, Mikael
    The fact that the vast majority of Uganda’s rural areas remain un-electrified makes it imperative that low cost distribution technologies be implemented in order to provide affordable electricity to rural households. Such low cost technologies include the Shield Wire System (SWS), Single Wire Earth Return (SWER) and appropriate engineering techniques. The SWER technology is presented in this paper as well as the implications of its proposed implementation for electrification of the village of Ntenjeru in Uganda. While SWER can reduce the costs of electrification by more than a third compared to conventional high tension transmission lines, there are stringent grounding and safety issues as well as load capacity constraints involved. Furthermore, with the earth used as a current return path, soil resistivity analysis is important in these systems. Since soil resistivity can vary sharply over varying terrain and in different weather conditions, robust SWER systems have to be carefully designed. An analysis of the financial and electrical load implications of this technology in Uganda’s local conditions will be presented and its viability as a sustainable method for electric energy distribution in the chosen case study area.
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    Technical, Economic And Sustainability Considerations Of A Solar Pv Mini Grid As A Tool For Rural Electrification In Uganda
    (Bakkabulindi, G., Sendegeya, A., Da Silva, I., & Lugujjo, E. (2010, July), 2010) Bakkabulindi, Geofrey; Sendegeya, Al-Mas; Silva, Izael Da; Lugujjo, Eriabu
    The challenges facing rural electrification in Uganda are diverse with less than 3% of the rural population having access to electricity. The establishment of mini-grids powered by renewable energy sources makes it possible to electrify remote areas at affordable rates. In this study, an assessment of a solar PV mini-grid system to provide electricity to forty households in rural Uganda was carried out. The considered system comprised six solar modules each rated 175 Wp, a controller, off-grid inverter and batteries with a capacity of 600 Ah. Manufactured by SMA, the Sunny Island inverter proposed for the mini-grid would ensure provision of grid-quality electricity. The study aimed to investigate the mini-grid’s technical design with focus on optimal distribution against constraints of voltage drops, electrical losses and increasing load. Customised load limiters shared between households using thermistors were included to reduce costs and limit consumption. The incomes of rural households are often seasonal and thus issues pertaining to affordability and sustainability were also considered. Results of the economic analysis showed a payback period of less than 5 years given an affordable fixed monthly tariff for the case study area.