Session: 18-05 HelioCon Modeling & Training

Paper Number: 142363

142363 - Modeling Receiver Flux of Commercial Power Tower Concentrating Solar Power Plants Using Ray Tracing: Benchmark Cases for Validation and Comparison of Ray-Trace Tools 

Abstract: 

Central Tower Concentrating Solar Power (CSP) is a type of renewable energy technology that uses mirrors to focus sunlight on a receiver so that it can be stored as thermal energy. Ray trace software tools are commonly used to simulate CSP collectors in models to predict and optimize plant performance across the industry and research community, but there exist no standards or guidance for validation of these tools. Ray tracing is the standard method used in comparing expected with actual plant performance to ensure power output goals are being met, so it is important that ray trace tools are reliable. In this work, benchmark cases were developed for validation and comparison of ray trace tools. The benchmark cases were validated through a round-robin comparison study of three different software packages for Monte Carlo ray tracing (MCRT) of central tower CSP:  (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. The benchmark cases are built on case studies from previous ray trace comparisons by modeling multi-facet heliostats and a commercial-scale solar field with zoned focal lengths and canting. The first phase of case studies includes single heliostats with a flat target modeled off of Crescent Dunes plant in Nevada to ensure agreement of the tools in modeling single facet and multi facet heliostats. The second phase of case studies include a commercial-scale field modeled off a planned plant in Port Augusta, Australia. The third phase of case studies include isolated heliostats within the commercial field modeled in phase II which isolate parameters such as heliostat blocking, aiming, and focusing/canting bands to help with troubleshooting discrepancies that may arise in different models. Factors compared in the benchmark cases include varying solar hour, heliostat locations, facet and canting focusing, and aimpoint strategies. Agreement was achieved across all three tools in this initial study, and the goal of the benchmark cases is to serve as a standard for the checking of future tools. Instructions for implementing the case studies have been documented in a paper including detailed instructions on each benchmark task and precise definitions for aimpoint strategies, slant range, and canting and focusing strategies needed to implement each case study. Results files for all case studies have been uploaded to a public online repository. Users of additional ray trace tools may use the documented instructions and online data files to participate in future iterations of the round robin study for validation and comparison.

Presenting Author: Rebecca Mitchell National Renewable Energy Laboratory

Presenting Author Biography: Dr. Rebecca Mitchell (PI) has been a researcher at NREL for five years, where she develops optical metrology tools for Concentrating Solar Power (CSP) collectors using algorithm development, theoretical modeling, and laboratory and field testing. She now serves as the team lead on the development on the Non-intrusive Optical (NIO) technology which surveys Concentrating Solar Power (CSP) solar fields using UAS imaging. She has led UAS data collection campaigns of heliostats at Sandia National Labs, Crescent Dunes plant, and Cerro Dominador plant. She has been involved in three publications and a recently issued patent for the NIO technology. Dr. Mitchell has mentored several graduate and Science Undergraduate Laboratory Internships (SULI) interns and now serves as the lead of the Resource, Training, and Education topic for the Heliostat Consortium project. Dr. Mitchell will oversee all aspects of the project and be responsible for all milestones.

Authors:

Rebecca Mitchell National Renewable Energy Laboratory
Ye Wang The Australian National University
Michel Izygon Tietronix Software, Inc.
John Pye The Australian National University
Guangdong Zhu National Renewable Energy Laboratory