Solar Energy Potential on Surfaces with Various Inclination Modes in Saudi Arabia: Performance of an Isotropic and an Anisotropic Model

Featured Application The present work studies the difference when assessing the solar energy potential of Saudi Arabia by using the Liu-Jordan (isotropic) and Hay (anisotropic) models. The present work investigated the performance of an isotropic (Liu-Jordan, L-J) and an anisotropic (Hay) model in assessing the solar energy potential of Saudi Arabia. Three types of solar collectors were considered: with southward fixed-tilt (mode (i)), with fixed-tilt tracking the Sun (mode (ii)), and with varying-tilt tracking the Sun (mode (iii)). This was the first time such a study was conducted for Saudi Arabia. The average annual difference between anisotropic (Hay) and isotropic (L-J) estimates is least approximate to 38 kWhm(-2) year(-1) over Saudi Arabia for mode (i), and therefore, the L-J model can be used effectively. In modes (ii) and (iii), the difference is greater (approximate to 197 and approximate to 226 kWhm(-2) year(-1), respectively). It is, then, up to the solar energy engineer to decide which model is to be used, but it is recommended that the Hay model be utilised for mode-(iii) solar collectors. These results fill a research gap about the suitability of models in practice. An interesting feature for the ratio of the annual mean solar energy yield of Hay over L-J as function of the latitude, phi, and the ground albedo, rho(r), is the formation of a "well" for 29 degrees <= phi <= 31 degrees and 1.15 <= rho(r) <= 1.