Solar Radiation in Mediterranean Climate: Measured Data Versus Correlation Models

Knowledge of solar radiation intensity is crucial for energy assessments in building thermophysics and for accurately evaluating the performance of both thermal and photovoltaic solar systems. To properly assess solar radiation intensity, one can refer to either experimental measurements or analytical models. The latter are based on correlations identified from experimental data measured over a long period. However, the results obtained through models may be inaccurate when applied to sites different from those for which they were calibrated. The solar radiation measuring station installed at the Laboratory of Energy and Environment of the Mediterranean University features multiple probes, enabling evaluation of solar and infrared radiation intensity in six mutually orthogonal directions, as well as measurements of direct and diffuse components of global radiation. To assess both the suitability and reliability of literature correlation models in the site’s climatic conditions typical of the Mediterranean coast, this study compared their outputs with experimentally measured data. The results show that the used correlation models seem to overestimate the diffuse component of solar radiation intensity, thereby underestimating the direct one. This issue may be particularly critical in scenarios where precise estimations of direct radiation are required, such as in the design of solar energy systems or energy-efficient building strategies. The discrepancies between the model outputs and the experimental data underscore the need for further refinement of these models, especially in regions with specific local climatic conditions like those found along the Mediterranean coast.