Evaluation of Atmospheric Lucidity and Diffused Radiation

Abstract

Evaluation of Atmospheric Lucidity and Diffused RadiationBased on measurements of the diffused and direct solar radiation intensity, the authors investigate the atmospheric lucidity and its variations that are characteristic of the Latvian conditions. They also consider the dependence of diffused radiation on the nebulosity. In the work it was established that the atmospheric lucidity in Latvia is usually in the range of 0.77±0.05, with only minor changes, so in the calculations it was assumed constant. The diffused solar radiation intensity was found to increase under medium nebulosity and to decrease at high its level. Since this dependence is also influenced by the type of clouds, for more precise calculations further research is needed.

Theoretical and Experimental Investigations of Cylindrical Air-Heating Solar Collector

“…In general, direct radiation received from the sun on horizontal flat surface can be written as where R 0 is solar constant (1367±7 W/m 2 , from "ISO 9488:1999(E/F) 3.24,"), P is lucidity of the atmosphere, in our case taken as constant and equal to 0.78 (Pelece et al 2010), but m is atmosphere mass -a quantity characterising thickness of the atmosphere, which solar rays pass through in relative units compared with when the sun is at the zenith. It has been found (Young 1994) that the mass of the atmosphere with good accuracy (error 2 % percent at horizon, higher even less) can be expressed as where Θ is zenith angle of the sun, i.e.…”