Pratt, Lawrence EBasappa Ayanna, ManjunathMkasi, Hlaluku W2025-02-122025-02-122024-11http://hdl.handle.net/10204/13988This paper compares forecasted global horizontal irradiance (GHI) data from SolCast to GHI recorded at the CSIR meteorological station in Tshwane, South Africa. The study compares the SolCast forecast to the CSIR measured values and computes accuracy metrics for +1-hour, solar noon, +1-day, and +7-day ahead forecasts. The +1-hour ahead and solar noon forecasts are based on the average value for a single hour, while the +1-day and +7-day ahead are based on the insolation over 24 hours. Based on the limited data collected for this study, the normalised root mean squared deviation (nRMSD) is 28.9% for the +1-hour ahead forecast at the CSIR for forecasts made in the morning. This forecast error from the morning forecasts is nearly double the nRMSD reported in a study conducted by the SolCast team on forecasts across 33 sites worldwide for forecasts made at all hours of the day (16.6%). The high forecast error is likely due to the relatively low irradiance value forecasted and measured in the morning hours of the winter season captured in the study dataset. By contrast, the nRMSD for forecasts made for solar noon of the same day was 11.3%, which falls within the range of values reported by the SolCast team. The normalised mean bias deviations (nMBD) for the daily insolation for +1-day and the +7-day ahead forecasts were both 5.2% at the CSIR.FulltextenSolar resourceGlobal horizontal irradianceGHIForecastingSolCastConference Presentationn/a