Modelling of hourly solar radiation collected on a tilted surface at Banket in Mashonaland West, Zimbabwe for optimum design of off-grid solar systems.

Abstract

Off-grid solar systems have become the most viable means of bringing electricity to sparsely populated rural communities of sub-Saharan Africa. This mostly because of the sharply falling prices of solar equipment and the maturity of the technology. The solar systems are also modular thus can be deployed at variety capacities for different applications. Zimbabwe has abundance solar resources ubiquitously spread country over. The design of the systems has however, been based on average country radiation which usually under-estimate or overestimate the insolation at a given site. This therefore affects the sizing of the systems and thus the cost. Also for off-grid systems it is not economical to carryout data collection of at least a year, which is another way to get accurate data. This study resorted to satellite data available on a freely accessible EU site as Typical Meteorological Year Data of 2009 downloaded using the Banket coordinates. The TMY data was used as the input to the model where, radiation data was input into the mathematical model of the tilted plane by Collares-Perreira and Rabl of 1996. Feeding the horizontal, beam and diffuse radiation data plus the ambient temperature into mathematical models resulted in the calculation of the solar radiation that can be received on a plane tilted at an angle equal to the latitude of the place. The data plotted for the whole year is a closer representative of the distribution of radiation received at the site for the whole year and thus reliable input to the design of off-grid solar systems as literature can confirm.