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SolTRACE, a new optical modeling code developed by researchers at the National Renewable Energy Laboratory (NREL) is currently being used to model solar power optical systems and analyze their performance. Although originally intended for solar optical applications, the code can also be used to model and characterize general optical systems. The creation of the code evolved out of a need to model more complex optical systems than could be modeled with existing tools. In addition, previous codes were based on outdated operating systems that significantly limited data presentation and output capabilities. SolTRACE is written specifically for the Windows® 2000 operating environment. Ray tracing methods coupled with the memory capabilities and the speed of the Windows® 2000 operating environment provide for accurate and rapid results. Output data presentation allows scatter plots, flux maps and performance graphs to be rapidly displayed and saved. SolTRACE has enabled Department of Energy (DOE) SunLab researchers to model and predict the performance of new, complex solar optical designs that previously could not be modeled. This paper describes the code and presents a comparison of SolTRACE results with measured and earlier modeled data.

SolTrace is an optical simulation tool designed to model optical systems used in concentrating solar power (CSP) applications. The code was first written in early 2003, but has seen significant modifications and changes since its inception, including conversion from a Pascal-based software development platform to C++. SolTrace is unique in that it can model virtually any optical system utilizing the sun as the source. It has been made available for free and as such is in use worldwide by industry, universities, and research laboratories. The fundamental design of the code is discussed, including enhancements and improvements over the earlier version. Comparisons are made with other optical modeling tools, both non-commercial and commercial in nature. Finally, modeled results are shown for some typical CSP systems and, in one case, compared to measured optical data.

This paper describes a technique that uses an infrared (IR) camera to evaluate the in-situ thermal performance of parabolic trough receivers at operating solar power plants. The paper includes results to show how the glass temperature measured with the IR camera correlates with modeled thermal losses from the receiver. Finally, the paper presents results of a field survey that used this technique to quickly sample a large number of receivers to develop a better understanding of how both original and replacement receivers are performing after up to 17 years of operational service.

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