Comparative assessment of plane-of-array irradiance models

Abstract

A comparative assessment of four mathematical models, used for predicting plane-of-array irradiance, is performed. These models are due to Liu-Jordan, Duffie-Beckman, Klucher, and Perez. Out of these four, the Liu-Jordan and the Duffie-Beckman models represent isotropic sky conditions and the other two model the anisotropic sky. The plane-of-array irradiance predicted by these models are compared against observed field data in Florida, North Caroline, and California. The time periods of interest are hourly, daily, and monthly. It is observed that the isotropic sky model can accurately predict only the monthly average of daily plane-of-array irradiance during the summer. Prediction on the daily or hourly time frame are either not possible or are predicted inaccurately by the isotropic sky model. Between the two anisotropic sky models, the Perez model performed the best, while the Klucher model constantly overestimated for the California location. Results found are consistent with those reported in previous studies.