Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.
Since 2012, the Universities of KwaZulu-Natal and Reunion Island have collaborated on a joint programme of solar energy research. The initiative has two principle aims: the development of solar forecasting techniques and the expansion of solar monitoring capabilities from continental Africa into the southern Indian Ocean region. In this paper, we introduce the programme and review the progress made. A key activity is performance validation of a low-cost radiometric sensor, the Delta-T Devices SPN1, which has been operated at a UKZN ground station for comparison against reference sensors. The instrument potentially represents an opportunity to expand existing radiometric networks by reducing the cost of ground station facilities. A novel feature of the device is its use of seven thermopile sensors and a stationery shading mask which together enable the simultaneous measurement of global horizontal and diffuse horizontal irradiance. It is important that the instrument performance should first be assessed, however, so that its measurement uncertainty is known ahead of deployment. Data from the UKZN trial are included in the paper, along with a description of a meteorological classification system that may be used in solar forecasting systems. The system is based on the direct solar fraction, that is, the ratio of direct horizontal irradiance to global horizontal irradiance. A clustering methodology is described and sample data are provided to illustrate the ability of the method to segregate days into statistically significant bins.
