Direct radiation estimates from horizontal global irradiance values

One of the main factors determining the economic feasibility of a solar thermal power plant is the availability of direct radiation at the plant site. During last years, two Central Receiver Power Plants (Solgas and Colon Solar) have been proposed in the South West of Spain (Huelva). For this area only global solar radiation data are available in a historical representative database. Based on an 11 years radiation database gathered at a nearby location, distance less than 100 km, 12 correlations, (one per month), between Mt and Md have been obtained. Solar global radiation data from the power plant site and generated correlations have allowed the "construction" of a Direct Radiation Design year that has been used both to design the solar plant heliostat field and receiver and to estimate annual energy produced by the solar plant.