Energy

Distribution of solar radiations

The sun will illuminate and heat the Earth until its hydrogen reserves are depleted, i.e. in approximately 5 billion years. The sun’s radiation reaches the earth in a non-homogeneous way because of its interaction with the atmosphere and the angle of incidence of sunrays. The angle of incidence varies according to two factors: the earth’s rotation around its axis, which is very important for the alternation of day and night, and the inclination of the earth’s axis as compared to the plane of its orbit, leading to a seasonal variation of the maximum height of the sun on the horizon. When the sun is perpendicular to the earth’s surface, the maximum concentration of sunrays on the ground is obtained. On the other hand, if the sunrays reach the earth’s surface with a certain inclination, the same amount of energy is dispersed over a larger surface. Therefore solar energy can be highly exploited only within a belt included between 45° latitude south and north.