Accuracy-enhanced solar resource maps of South Africa

Abstract

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.

SolarGIS is a global database of solar resource and meteorological parameters, developed and operated by GeoModel Solar. This database is updated daily by real-time satellite, atmospheric and meteorological data inputs. The aim of presented work was accuracy enhancement of solar resource data for South Africa, Lesotho and Swaziland. This was achieved by regional adaptation of SolarGIS solar model with data measured at fourteen high-standard solar measuring stations sourced by Eskom, GeoSUN Africa, SAURAN, STERG and Ripasso Energy. The accuracy-enhancement procedure is based on correlation of the ground measurements with the satellite-based SolarGIS model and determination of correction coefficients for model inputs. Use of these coefficients reduced systematic deviation of the input aerosol data, which is key factor determining the model accuracy in Southern Africa. The user uncertainty of the longterm estimate based on adapted data is in the range of ±5% to ±7.5% for DNI, and ±3% to ±4% for GHI. The model now delivers more accurate high-resolution solar resource time series, which helps reducing financial risk and improving engineering quality of the solar power plants. The presented maps show longterm yearly averages of Direct Normal Irradiation (DNI) and Global Horizontal Irradiation (GHI) with 1-km spatial resolution. They are calculated by aggregation of sub-hourly modeled time series, representing a period 1994 to 2013. The maps are accessible from http://www.sauran.net/. High resolution data can be accessed from http://solargis.info.