Résumé
Nowadays, energy supply is a major challenge for developing countries. In Sub-Saharan Africa, about only one-third of the population is connected to the electrical network and the use of classical energy resources presents economical and environmental problems. As many other African countries, the Djiboutian government looks for installing power systems using renewable energies, including solar systems, in order to overcome power supply difficulties in their energetic strategy.
Therefore, the aim of this study is the creation of the first solar atlas in Djibouti, including assessment and improvement, for helping to establish an energy planning. To realize this atlas, a satellite-based irradiance model is used (EUMETSAT O&SI SAF). To validate this model over Djibouti, we installed 2 pyranometric weather stations during the year 2010 and we compared hourly, daily and monthly irradiation estimates against ground measurements. Results showed a good agreement between measurements and estimates, with, for the whole hourly sets, an RRMSE equal to 10.88% and 15.29%, and a bias of 0.61% and -2.17%.
Then, to improve accuracy of irradiation estimates, we disaggregated irradiation maps with a 3 arc second (similar to 90 m at the equator) Digital Elevation Model (DEM), in order to take into consideration topography and elevation effects. As current software does not allow downscaling of pre-processed maps, we performed this work by computing our own global model, combination of horizon, elevation correction and irradiance splitting models. By comparing horizon estimates against measured horizons, we observed that error probability on irradiation increased over high mountainous areas, mainly due to the original DEM error.
Finally, according to the final computed atlas, during the year 2010, mean irradiation all over the country was around 2100 kWh/m(2) and about 82% of the country received over 2000 kWh/m(2). Furthermore, the solar radiation reaching Djibouti corresponded to 20,000 times the total yearly energy consumption of the country in 2005.
With the first solar atlas of Djibouti, this study shows how reliable the solar potential in the country is and presents an accurate decision-making tool for sizing future solar systems across the country. (C) 2013 Elsevier Ltd. All rights reserved.