Enhanced Insolation and Global Irradiance in Near-tropic Region
Abstract
Knowledge of peak solar irradiance levels and radiation is required to perform holistic photovoltaic system design for a particular location. In order to quantify solar energy input, c-Si reference cells were installed in three locations representing the North, middle-East and South of Mauritius. Global horizontal solar irradiance was measured at high frequency distribution intervals of 30-seconds since March 2012. The high resolution data was used in order to evaluate the enhanced irradiance levels and to compute average irradiance, radiation and the sky clearness. The latter were used to develop contour plots representing distribution of radiation and clearness for the whole year across the island. Enhanced irradiance levels of above solar constant (1367 W/m2) were recorded in the summer months. The frequency of occurrence of those values was from a few to as many as 70 times and they lasted for up to 2 minutes. Enhanced irradiance levels of above 1500 W/m2 were also recorded at least twice in all the three locations. Average daily global radiation was calculated to be 3.91 kWh/m2, 5.09 kWh/m2 and 3.97 kWh/m2 in the East, North and South respectively, but even 7.79 kWh/m2 was recorded. Low clearness values, between 0.3 – 0.61 were obtained. They reflect a higher level of cloud coverage over the island which subsequently increase Mie scattering and justify the enhanced irradiance levels that were measured. All solar data were compared to countries of the African continent with the same latitude as Mauritius.
Keywords
Enhanced irradiance, Enhanced global horizontal radiation, Near-tropic african region