Portal de Periódicos da CAPES

Extraterrestrial Solar Radiation

2017; IGI Global; Linguagem: Inglês

10.4018/978-1-5225-2950-7.ch003

2326-9170

Photovoltaic System Optimization Techniques

Extraterrestrial solar radiation is the main source of terrestrial solar radiation components. Data on the spectrum of this radiation is available and a value of 1367 Wm-2 for the solar constant is accepted in solar literature. The knowledge of extraterrestrial solar radiation is essential for solar applications, within them is the Sun tracking. This radiation on horizontal surface is widely treated and a simple formula, for calculating it, is widely used. On Equator facing solar receivers, the appropriate equations for obtaining this radiation are also available, but the application of these equations by different authors was found to be not evident mainly on calculating the sunset hour angle on such surfaces. This question becomes problematic for some authors when treating surfaces of different orientations. The term of characteristic day is widely used in solar literature. The ambiguity of this term with regard to extraterrestrial solar radiation, declination angle and extraterrestrial solar radiation on a horizontal plane is described. In order to completely solve the above-mentioned problems, extraterrestrial solar radiation is calculated on surfaces of different orientations and the required relations are given for each case. The introduction of the energy gain on the basis of extraterrestrial solar radiation could be formulated mathematically very precisely. Therefore, this question is treated in details in this chapter. The difference between short term and long term Sun tracking is described also and the maximum possible energy gain of these two types of tracking is characterized.