Basics Of Solar Radiation

By Author: Rockey
Total Articles: 139
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The sun and its radiation have a great impact on the entire earth. Most forms of fuel and energy have derived their power from the solar power originally. This solar energy is the beginning for the chemical and biological processes on our planet. When fossil fuels and biomass sources are used for energy one is simply trying to recoup the solar power contained within. The winds and ocean currents also pull some of their energy from the sun’s heat. Thus is makes sense to glean energy from this magnificent source directly.
To properly analyze potential of solar power, one must understand its trajectory across the earth’s sky. This path can be described with three variables: the azimuthal angle,zenith angle, and hour angle. The azimuthal angle is known as the angle (going clockwise) that the sun makes against the north line. The zenith is a vector forming a 90o angle (also known as an orthogonal vector) with a specific location on the globe. Thus the zenith angle is measured between the base of the zenith and the sun. The hour angle is a manner of calculating time. At solar noon, the hour angle is 0o, before noon, it ...
... is negative and after noon it is positive. In a 24 hour period, the hour angle changes by 360o. For most effective solar power collection, a two axis tracking system is required. One such system is in place on the SolarBeam Concentrator, produced by Solartron Energy Systems. The SolarBeam Concentrator uses a parabolic collector and a specially designed computer system with the power to calculate the position of the sun at any time of day, any time of year, anywhere on the globe.
While the path of the sun changes depending on one’s location, the effective radiated power remains more or less constant. The term for this is irradiance. This varies slightly depending on the distance from the sun, but mostly within the UV spectrum, therefore does not radiation available for solar thermal energy. Climate and thus cloud cover do have a large effect on solar radiation. Clouds reflect and scatter the solar radiation. Radiation intensity is lessened by atmospheric reflection, absorption by molecules in the atmosphere (such as O3, H2O, O2, CO2), Rayleigh scattering (scattering by the air molecules) and Mie scattering (scattering from pollution, dust particles and air contamination). Irradiance then varies according to weather and human influence.
Human society could potentially be fuelled entirely from the sun. There is enough irradiance across the globe to dwarf the energy used provided by coal, oil, natural gas and uranium. The issue now is harvesting this solar energy. Every country on earth could benefit from an efficient solar power collection and distribution system.