Browsing by Author "Mubiru, J."

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    Assessing The Distribution Of Solar Irradiation In Mbarara, Uganda
    (Theoretical and Applied Climatology, 2007) Mubiru, J.; Banda, E. J. K. B.; Otiti, T.; D’Ujanga, F.; Karume, K.; Nyeinga, D.; Okello, D.; Katongole, D. N.
    Careful measurements of surface radiation balance components provide, in principle, an important contribution to the understanding of the global energy cycle. They can be used to further improve climatologies of radiative flux components or in the validation of parameterization procedures in weather forecast and climate models. Existing literature lacks information on the distribution of global solar radiation and its two components for locations close to the Equator. The objective of this study is to identity and assess the distributions of global solar irradiation and the ratio of diffuse to direct solar irradiation at a site in Mbarara, Uganda, located at 00°37′S latitude, 30°39′E longitude and at 1413 m altitude. Results have shown that there are bigger and more frequent variations in daily global irradiation at the beginning and towards to the end of the year. The dominance of diffuse over direct solar radiation during the same periods has been demonstrated. The results have been compared with those from a similar measurement site and have shown some similarities and some differences.
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    Correlation Between Sunshine Hours And Climatic Parameters At Four Locations In Uganda
    (Tanzania Journal of Science, 2007) Karum, K.; Banda, EJKB.; Mubiru, J.; Majaliwa, M.
    One of the most important factors in solar energy production is related to the predictability of sunshine hours. The objective of this study is to assess the correlation between sunshine hours and relative humidity, cloud cover, maximum and minimum temperature, for the purpose of identifying the most appropriate parameter(s) for the prediction of sunshine hours in Uganda. Climatic data for the meteorological stations of Entebbe, Mbarara, Tororo and Makerere, extending over a period of 15 years (1990-2005) was collected from the Department of Meteorology, Kampala. The data set included maximum temperature, minimum temperature, relative humidity at 6 am and at 12 noon, Cloud cover at 6 am and at 12 noon and Sunshine hours. A multiple regression technique was used to assess the correlation between sunshine hours and maximum and minimum temperatures, cloud cover at 6 am and at 12 noon and relative humidity at 6 am and at 12 noon. Results have shown that the availability of sunshine hours can be predicted by the use of maximum and minimum temperatures, relative humidity at 6 am and 12 noon and cloud cover at 6 am and at 12 noon in Uganda, but, principal components and factoraAnalysis have indicated that two parameters, especially relative humidity at noon or 6 am and Maximum temperature are enough to capture the variability of sunshine hours in Uganda.
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    Estimation Of Monthly Average Daily Global Solar Irradiation Using Artificial Neural Networks
    (Solar Energy, 2008) Mubiru, J.; Banda, E.J.K.B.
    This study explores the possibility of developing a prediction model using artificial neural networks (ANN), which could be used to estimate monthly average daily global solar irradiation on a horizontal surface for locations in Uganda based on weather station data: sunshine duration, maximum temperature, cloud cover and location parameters: latitude, longitude, altitude. Results have shown good agreement between the estimated and measured values of global solar irradiation. A correlation coefficient of 0.974 was obtained with mean bias error of 0.059 MJ/m2 and root mean square error of 0.385 MJ/m2. The comparison between the ANN and empirical method emphasized the superiority of the proposed ANN prediction model.
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    Monthly Average Daily Global Solar Irradiation Maps For Uganda: A Location In The Equatorial Region
    (Renewable Energy, 2012) Mubiru, J.; Banda, E.J.K.B.
    Proper sizing of solar energy systems is necessary in order to optimize their output. This requires a database of solar irradiation for locations for which the systems are being assessed. Solar irradiation data is also required in modeling a building’s thermal performance, as input into ecological and crop models and evaluation of long-term effects of climatological changes. Solar irradiation data can be provided through measurements. In Uganda, measurements of global solar irradiation have been carried out for a few locations because the measuring instruments are expensive to purchase and install. An alternative to obtaining solar irradiation data is to estimate it either by use of an appropriate solar irradiation model or interpolation of the few existing records. The present study attempted to draw global solar irradiation maps for Uganda. Global solar irradiation values were estimated for eight out of twelve stations using an artificial neural networks model proposed for Uganda. Measured values of monthly average daily global solar irradiation were used for the remaining four stations. The values for the twelve stations were then utilized for the interpolation using moving average method. The result is a set of twelve global solar irradiation maps for Uganda with relative errors in the range of 8%–16%.