The effect of the surrounding topography on incoming solar radiation

The scope of this postgraduate thesis is the study of the effect of surrounding topography on receipt of solar radiation, by using Geographic Information Systems (GIS). Within the framework of this study, a model of calculating direct solar radiation has been developed, which has been applied to the Digital Terrain Model (DTM) of Greece. The simple modeling of direct solar radiation requires the knowledge of the incoming radiation and its application at every point of the surface. The Geographic Information Systems (GIS) was used for the calculation of potential solar radiation at every pixel of Greece, for every hour of an average year. The altitude and the azimuth of the sun, the slope and the aspect of every pixel and the shadow effects due to topography were taken into account for the calculations. The hourly estimation were summed in daily, monthly and annual basis, in order to facilitate their comparison. Two indexes were calculated, in order to compare the estimated with the theoretically expected values. The first is the fraction of the estimated to the theoretically incoming potential solar radiation for flat surface, as it is calculated in the bibliography. The second index is the fraction of the estimated to the theoretically incoming potential solar radiation to the equator, latitude 0o, for a flat surface that is not shadowed.