The way heliostats in a field are aimed at the receiver plays a critical role in plant operation. The multiaiming strategy relies on a single parameter, named k aiming factor. The computation of a heliostat aimpoint follows a two-step process: (1) estimation of the beam radius a function of k, and (2) determination of the target point so that the selected beam is tangent to a receiver edge.
Heliostats in successive rows of a field can be alternatively aimed at the top and the bottom of the receiver. This strategy leads to flux maps symmetric with respect to the receiver midplane.
For specific receivers and heat transfer fluids, their stress and corrosion constraints can be translated into allowable flux densities (AFD). From AFD datasets, the aiming strategy is customized to meet the limitations; for instance, in molten-salt receivers (figure below).
Aiming strategy model based on allowable flux densities salt central receivers
A. Sánchez-González, M.r. Rodríguez-Sánchez, D. Santana
Allowable solar flux densities for molten-salt receivers: Input to the aiming strategy
A. Sánchez-González, M.R. Rodríguez-Sánchez, D. Santana