Photovoltaic array performance model.

TLDR: In this paper, the authors summarized the equations and applications associated with the photovoltaic array performance model developed at Sandia National Laboratories over the last twelve years, including system design and sizing, "translation" of field performance measurements to standard reporting conditions, system performance optimization, and realtime comparison of measured versus expected system performance.

Abstract: This document summarizes the equations and applications associated with the photovoltaic array performance model developed at Sandia National Laboratories over the last twelve years. Electrical, thermal, and optical characteristics for photovoltaic modules are included in the model, and the model is designed to use hourly solar resource and meteorological data. The versatility and accuracy of the model has been validated for flat-plate modules (all technologies) and for concentrator modules, as well as for large arrays of modules. Applications include system design and sizing, 'translation' of field performance measurements to standard reporting conditions, system performance optimization, and real-time comparison of measured versus expected system performance.

Figures

Figure 14. Modeled maximum power from array at three operating temperatures as a function of effective irradiance. Field measurements translated to 50ºC are shown for comparison with model. The reference Pmp value at the ASTM Standard Reporting Condition is also shown.

Figure 13. Array voltages given by performance model after determination of required modeling coefficients. For comparison, the measured values were translated to a common temperature, 50°C, and also included on the chart. The modeled performance values at the ASTM Standard Reporting Condition are also shown.

Figure 20. Example data entry in the module database associated with the array performance model.

Figure 17. Photo of a wiring ‘combiner box’ housing the terminations for 17 high-voltage module-strings in a large array. In this case, each module string had twelve 150-Wp crystalline silicon modules connected in series.

Figure 2. Illustration of a module I-V curve showing the five points on the curve that are provided by the Sandia performance model.

Figure 6. Typical empirical relationship illustrating the influence of solar spectral variation on module short-circuit current, relative to the AMa=1.5 reference condition. Results were measured at Sandia National Laboratories for a variety of commercial modules.