Analysis of irradiance ramps in desert conditions

Large fluctuations in solar irradiance over very short periods of time, called ramps, result in important changes in power generation, with immediate effect in the case of photovoltaic systems, an effect that can be lost when using data aggregated at longer intervals. In solar forecasting applications, for instance, prediction of ramps can add not only more accurate information, but can be useful in management and balancing of the generation system. A study is presented here of solar irradiance ramps found, using 5-minute windows, through 2 years in 8 locations across Qatar, a desertic region with relatively low cloudiness, where ramps could be expected to be rare. With the used method, ramps were found in under 5% of the available windows, with some differences between north-to-south sites, and before-or-after noon are found.