Calculation of solar irradiance profiles from hourly data to simulate energy systems behaviour

In various studies of solar energy systems (sizing, estimation of production), we need solar irradiation data collected with a smaller time interval than those often available in databases (often hourly irradiations). We compare three models (constant, linear and extraterrestrial) which simulate an hourly profile of solar irradiance and allow the determination, with a given reliability, of minute data of global solar irradiation from hourly measured irradiations. These models are compared from the point of view of various statistical tests using data collected on a Mediterranean site. The extraterrestrial model shows very satisfying results and improves greatly the accuracy compared with a constant model.