Validation of Solar Extinction Model at Plataforma Solar de Almería

Abstract

Solar extinction should be one of the most important factors to select the best locations for solar tower plants. The optical path between the heliostats and the receiver (slant range, SR) very often exceed 1 km. This distance could involve many particles in the atmosphere, which absorb and scatter the reflected solar radiation. Therefore, it is necessary to know the radiative losses due to solar extinction at the location and to have models rigurously validated with experimental data. At PSA there is a database with more than 6 years of solar extinction measurements. These data have been obtained thanks to a solar extinction measurement system developed by The Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT). This database allowed the development of a Typical Solar Extinction Year (TSEY). This TSEY presented an average annual solar extinction value of 6 ± 2 % for a measurement distance of 741.63 m. With this amount of data a model  to estimate solar extinction has been validated at PSA. The input data used were the aerosol optical depth (AOD) and the SR. For this purpose, average daily extinction values were estimated with a model. From this new simulated database, a synthetic TSEY was developed in order to compare it with the experimental TSEY. In both cases, the average annual solar extinction values were in agreement with the value of 6 ± 2 % (741.63 m). By this way, the model has been validated and it could be used to estimate solar extinction worldwide.