Representative Days for the Calculation of Annual Optical Efficiency of Solar Tower Systems

A solar tower system primarily consists of a collector field of heliostat mirrors and a heat collection unit called the receiver. The ability of the heliostat mirrors to concentrate the solar radiation on the receiver is termed the optical performance. It is necessary to predict the optical performance of an SPT system as accurately as possible. The optical performance of the SPT system depends on the position of the sun primarily, which varies with the time of day. Considering many time instants from each day, for multiple days of the year, the prediction of annual optical performance is computationally expensive. For this reason, a set of dates may be used to represent an entire year, and discrete time points at regular intervals can be chosen. Therefore, the accuracy of the predicted optical efficiency may depend on the choice of the dates selected to represent the entire year. In this study, multiple sets of dates and discrete time intervals have been considered. The annual optical efficiency predicted based on the calculation at each 1 min time interval for 365 days is considered to be the standard for comparison. It was observed that annual optical efficiency can be predicted with sufficient accuracy when only four days of the year are chosen as the representative days, thus reducing the computational burden.