1.1. General remarks
«Previous Next» Back to reportSolar rays received at the surface of the Earth are separated into two distinct kinds: direct and scattered, or diffuse. Direct sunlight consists of radiation that reaches Earth as it is generated straight from the sun. The intensity of direct solar radiation is dependent on how clean the atmosphere is (clarity of the sky), how high the Sun is over the horizon (subject to the geographical latitude and time of day), and on the position of the surface with regard to the Sun.
Diffuse solar radiation comes from the upper layers of the atmosphere and is contingent on how the direct solar rays are reflected off the Earth and its atmospheric constituents. Because of the recurrent process of reflection of the sunlight between the snow-covered Earth and the lower side of the clouds, diffuse solar irradiance can fluctuate to high levels.
Sunbeams carry with them an inexhaustible source of energy. They consistently supply the Earth with more energy than we require today. The rate of solar radiation in space – or irradiance – is approximately 1.4 kW/m2. Of that, around 30% is reflected back into space without ever reaching the Earth’s surface. At the surface, solar irradiance reaches around 1 kWt/m2. When solar energy arrives at the surface of the Earth it transports heat, evaporates water, creates wind, moves water in the Earth’s seas and oceans, and gives life to its flora.
Those amounts of solar energy that are not immediately absorbed by the Earth are scattered back into space. The Earth remains in a constant heat balance with the surrounding environment. If that were not the case, the Earth’s temperature would have increased exponentially and any life on the planet would have been impossible as a result.
Solar energy resources are extensive – if not unlimited. The problem, however, is that the peak of solar energy exposure takes place in the summer, at the time when consumers’ need for it is lowest. In the winter, when energy demand is high, sunshine is only available for a short interval during daytime, and at a low angle at that. Only one solution presents itself: Solar energy needs to be accumulated in the summer and used in the winter.«Previous Next» Back to report
