Analysis of Raindrop Diameters for Rainfall Attenuation in Southern Africa

The influence of critical raindrop diameters on the specific rainfall attenuation in Durban (29o52'S, 30o58'E), South Africa using various rainfall regimes is analyzed in this paper. Different rain rate values representing drizzle, widespread, shower and thunderstorm are selected for the purpose of analysis over the measured raindrop size distribution. The three-parameter lognormal and gamma DSD models with shape parameter of 2 are used to estimate the parameters required to investigate the drop sizes which produce a major contribution to the total specific rainfall attenuation for the selected rain rate values. The computed total specific attenuation increases with increasing frequencies and rain rates. The highest and prevailing contribution to the specific attenuation occurs at  for the stratiform (drizzle or widespread) and convective (shower or thunderstorm) rain types for the models considered.  The total percentage fraction formed by drops in the diameter range 0.5 mm ≤ D ≤ 2.5 mm and 1.0 mm ≤ D ≤ 3.0 mm are found to be most critical for the specific rain attenuation for the stratiform (drizzle and widespread)  and convective (shower and thunderstorm) rainfall types especially at higher frequencies

Feasibility and optimal design of a hybrid power system for rural electrification for a small village

A hybrid renewable energy system is at present accepted globally, as the best option for rural electrification particularly in areas where grid extension is infeasible. However, the need for hybrid design to be optimal in terms of operation and component selection serves as a challenge in obtaining reliable electricity at a minimum cost. In this work, the feasibility of installing a small hydropower into an existing water supply dam and the development of an optimal sizing optimization model for a small village-Itapaji, Nigeria were carried out. The developed hybrid power system (HPS) model consists of solar photovoltaic, small hydropower, battery and diesel generator. The optimal sizing of the system’s components for optimum configuration was carried out using Genetic Algorithm. The hybrid model’s results were compared with hybrid optimization model for electric renewable (HOMER) using correlation coefficient (r) and root mean square error (RMSE) to verify its validity. The results of the simulation obtained from the developed model showed better correlation coefficient (r) of 0.88 and root mean square error (RMSE) of 0.001 when compared to that of HOMER. This will serve as a guide for the power system engineers in the feasibility assessment and optimal design of HPS for rural electrification