Comparative approach for global solar estimation in four typical Senegalese climatic zones

This work constitutes an approach for the estimation of global solar radiation on 4 climatic zones of Senegal. These are the sites at Dakar, Saint Louis, Tambacounda and Ziguinchor. For this study, data from the Helioclim-3 database of the Meteosat-2 satellite are used as model inputs. For the validation process estimated data and meteorological observations were incorporated into the hourly values. The Clear Sky models of Bird & Hulstrom, Lacis & Hansen and Davies & Hay are simulated. They are based on the determination of the transmission coefficients of the various atmospheric constituents. These coefficients require the availability of current meteorological parameters (relative humidity, ambient temperature, atmospheric pressure) and geographical parameters of the site (latitude, longitude and altitude) and also of the solar position. A comparative study of the results obtained by simulation of the three models showed that the Bird & Hulstrom model gives a better estimate of the global component of solar irradiation. The errors between the values of the meteorological observations and those calculated are small for all 4 sites. The mean square errors are small between 10% and 20% and mean relative errors between 0.1% and 12%. The Bird & Hulstrom model was therefore finally chosen for the establishment of global hourly solar radiation over all four zones. The algorithm structure was built using R software.