Key Parameters in Determining Energy Generated by CPV Modules

We identify the key inputs and measurement data needed for accurate energy rating of concentrator photovoltaic (CPV) modules based on field observations of multiple CPV modules. Acceptance angle is shown to correlate with the observed module-level performance ratio (PR) for the modules studied. Using power ratings based on concentrator standard test conditions, PRs between 90% and 95% were observed during the summers with up to ~10% lower PRs during the winters. A module fabricated by Semprius showed 94% ±0.7% PR over almost 2 years with seasonal variation in PR of less than 1% showing how a module with relatively large acceptance angle may show very consistent average efficiency (calculated from the energy generated relative to the energy available), potentially simplifying energy ratings. The application of the results for translation of energy rating from one location to another is discussed, concluding that most of the translation differences may be correlated with temperature differences between sites with the largest variation happening when optical efficiency depends on temperature.