Ray Tracing Verification Round Robin Data

In this work, three different software packages for Monte Carlo ray tracing (MCRT) of central tower concentrating solar power (CSP) systems were compared, in a multi-stage cross-validation process. The three packages are (1) SolTrace, an open-source code from the National Renewable Energy Laboratory (NREL), (2) Solstice, an open-source code originally by CNRS-PROMES and Méso-Star with additions by the Australian National University, and (3) TieSOL, a commercial code developed by Tietronix. This investigation builds on previous ray trace comparisons by modeling multi-facet heliostats and a commercial-scale solar field with zoned focal lengths and canting. The agreement of receiver flux distributions across the tools are assessed in single-heliostat, isolated blocking, and full-field case studies. Simpler case studies were devised to identify and resolve where differences might arise in the models as parameters are introduced. Factors examined in the analysis include varying solar hour, heliostat locations, facet and canting focusing, and aimpoint strategies. The comparison aims at improving accuracy and reliability of the above tools and providing benchmark cases for the checking of future tools.