Observation and Simulation of Available Solar Energy at N’Djamena, Chad

Abstract

The objective of this work is to evaluate the available solar potential at N’Djamena (12°08N, 15°04E) from 2017 to 2018. To achieve this goal, we used various datasets and model including: the in situ shortwave radiation (by pyranometer) measurement and sunshine duration (by Campbell-Stokes heliograph) obtained from N’Djamena station, observations from MODIS (aerosol optical depth (AOD) and precipitable water) satellite sensors, and simulations from Streamer radiative code. The results show the presence of a good available solar potential with an annual global potential of 4.71 kWh/m2/d. At the intra-seasonal time scale, there are two maximums for the global solar potential. The first maximum is registered in the month of March (spring) with value of 5.7 kWh/m2/d and the second in October (autumn) with value of 5.18 kWh/m2/d. However, the minimum of global potential is recorded in winter (from December to February) with values around 3.86 kWh/m2/d. Then, the measured global irradiation allowed validating the Streamer radiative transfer code with a score of more than 98%. Subsequently, this model was used to simulate direct normal and diffuse irradiation for several types of days (clear, dusty and cloudy days). An examination of the dust influence on solar radiation based on selected cases (AOD = 2.05) indicates a mean decrease of 3.33 and 3.17 kWh/m2/d, respectively, for the total and direct normal potential. This corresponds to an increase of the diffuse potential of 0.52 kWh/m2/d. Finally, an increase of 5.82 cm of precipitable water per day tends to decrease the overall potential of 0.73 kWh/m2/d and the direct normal potential of 1.74 kWh/m2/d. For this cloudy day, the potential has increased more than 0.89 kWh/m2/d.