Evaluating a model to estimate GHI, DNI, & DHI from POA irradiance

We evaluate the GTI-DIRINT model for estimating direct normal irradiance (DNI), diffuse horizontal irradiance (DHI), and global horizontal irradiance (GHI) from measured plane-of-array (POA) irradiance. Our motivation is to explore the potential for limiting ground-based irradiance measurements to POA to reduce instrumentation costs. We test the GTI-DIRINT model using meteorological data collected at seven First Solar PV power plants, comparing the GTI-DIRINT model which uses POA as input to the DIRINT model which uses GHI as input.