THE RELATIONSHIP BETWEEN DIFFUSE AND TOTAL SOLAR RADIATION IN COMPUTER SIMULATION OF SOLAR ENERGY SYSTEMS

ABSTRACT The diffuse to total radiation correlation developed by Liu and Jordan [1] was tested for three Italian locations. An acceptable agreement was found between the regression lines in [1] and the ones found for two of the three locations. Using measured hourly values of total solar radiation on a horizontal surface, the corresponding hourly values of total solar radiation on an inclined surface at 45° facing south were computed with both the Liu and Jordan and the Loudon [6] method for estimating the diffuse radiation. Results show that approximately the same degree of accuracy in the prediction is achievable with both methods and that the difference between the measured total monthly…