Spatiotemporal variations of global solar radiation: Case Study Egypt

The spatio-temporal characteristic of the available global solar radiation (GSR) variability is essential for effective grid integration of photovoltaic (PV) power systems, particularly in developing countries such as Egypt. Thus, the long-term spatio-temporal variability of GSR and its trend assessment, fluctuations, and abrupt change detection during the climate period 1985-2018 based on eight ground-based stations in Egypt were statistically analyzed. The missing records in the observed GSR data were completed using the SoDa (Solar radiation data) database after its validation at the selected eight stations, which produced high accuracy and slight bias compared to the available observations. The results showed that the northern coast, particularly the Nile Delta region, has lower GSR values than the southern region. At all stations, winter had the largest coefficient of variation (COV) values while summer had the lowest COV values. Furthermore, the trend analysis for GSR using Mann-Kendall (MK) rank statistical test revealed that autumn, followed by winter and spring has a positive trend across Egypt, while the annual and summer GSR have positive trends over middle and northern Egypt. The annual GSR long-term variability measured by Gaussian and Binomial low-path filters shows a positive trend at all stations except Arish, Asyut and Kharga. Moreover, the detected first abrupt change point for the annual GSR data occurred during the 1990s at all stations except for Matrouh in 2002. This first abrupt change point is positive (increasing GSR values) at all stations except a negative trend for Bahtim and Kharga. The second and third abrupt change points are positive at all stations except Arish during 2003-2009 in the second change point and returns to its positive trend in the third change point in 2010.