Blossaim, a Deterministic Aiming Strategy for Circular Aperture Receivers

Small heliostats tend to produce a sharp peak flux on a receiver aperture if they are all aimed at a single point. Several receiver concepts have circular receiver apertures and polar heliostat fields. It is of interest to flatten the flux distribution on such receivers to achieve a more homogeneous receiver surface temperature for improved thermal absorption and reduced thermal stress. A new implementation of an existing aiming strategy methodology is presented in this paper for a circular receiver with a polar heliostat field. This implementation is investigated using a convolution projection flux modelling approach and compared with a baseline of single point aiming. The aiming strategy implementation reduces the peak flux magnitude from single point aiming by 66% and leads to a substantially uniform flux distribution on the aperture while incurring a 17.1% lower field optical efficiency on an aperture with a diameter of 1 m. The optical efficiency cost can be improved to a reduction (from single point aiming) of only 2% by slightly extending the aperture diameter for the same aiming points. The implementation deterministically arranges the aiming points of the heliostats to produce a flux distribution that is robust to a changing field optical efficiency distribution with solar time.