Aiming factor to flatten the flux distribution on cylindrical receivers

Abstract

High incident flux gradients and hot spots lead to extreme thermal stresses that may damage and reduce the lifetime of central receivers. An aiming strategy based on a single parameter, k, named aiming factor, is developed to generate symmetric flux maps about the receiver equator. By means of this k factor, ranging between 3 (generally equivalent to equatorial aiming) and 0 (alternatively aiming to top and bottom borders), the solar flux incident on the receiver and the spillage losses can be controlled. For each sector in a heliostat field, the aiming factor values causing the flattest symmetric flux maps, kflat, are deterministically found with a sweep and mesh shifting procedure. Results for Dunhuang solar power tower plant show that kflat is fairly constant throughout the year, except near sunrise and sunset in east and west sectors, respectively./