Parameterization models for solar radiation and solar technology applications Samy A. Khalil * National Research Institute of Astronomy and Geophysics, Solar and Space Department, Marsed Street, Helwan, 11421 Cairo, Egypt Received 30 May 2007; accepted 14 January 2008 Available online 21 March 2008 Abstract Solar radiation is very important for the evaluation and wide use of solar renewable energy systems. The development of calibration procedures for broadband solar radiation photometric instrumentation and the improvement of broadband solar radiation measurement accuracy have been done. An improved diffuse sky reference and photometric calibration and characterization software for outdoor pyr- anometer calibrations are outlined. Parameterizations for direct beam, total hemispherical and diffuse sky radiation and solar radiation technology are briefly reviewed. The uncertainties for various broadband solar radiations of solar energy and atmospheric effects are discussed. The varying responsivities of solar radiation with meteorological, statistical and climatological parameters and possibility atmospheric conditions was examined. Ó 2008 Elsevier Ltd. All rights reserved. Keywords: Solar radiation; Calibration; Total hemispherical; Renewable energy; Photovoltaic technology 1. Introduction Solar radiation is becoming increasingly appreciated because of its influence on living matter and the feasibility of its application for useful purposes. It is a perpetual source of natural energy that, along with other forms of renewable energy, has a great potential for a wide variety of applications because it is abundant and accessible. Solar radiation is rapidly gaining ground as a supplement to the non-renewable sources of energy, which have a finite sup- ply [1,2]. Solar radiation is partially depleted and attenuated as it traverses the atmospheric layers, preventing a substantial portion of it from reaching the earth’s surface. This phe- nomenon is due to absorption, scattering and reflection in the upper atmosphere (stratosphere), with its thin layer of ozone, and the lower atmosphere (troposphere), within which cloud formations occur (Table 1). The stratospheric ozone layer has a strong absorption affinity for solar UVR (ultra-violet radiation), depending on wavelength. Absorp- tion, being more effective for shorter wavelengths, tends to reach its peak at 250 nm and drops rapidly with an increase in wavelength, even beyond 350 nm. Thus, the biologically harmful radiations below 280 nm (vacuum UV and UV-C) are completely shielded by the ozone layer; only a fraction of the UV-B and UV-A wavelength bands reach ground level. Depletion of the protective ozone layer beyond the critical level by certain atmospheric pollutants (fluorocar- bons and nitrogen oxides) that interact photochemically with ozone will promote the transmission of highly injuri- ous UVR. The troposphere is an attenuating medium. The solar radiation is reflected and scattered, primarily by clouds (moisture and ice particles), particulate matter (dust, smoke, haze and smog) and various gases. The two major processes involved in tropospheric scattering are deter- mined by the size of the molecules and particles and are known as selective scattering and non-selective scattering. Selective scattering is caused by smoke, fumes, haze and 0196-8904/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.enconman.2008.01.023 * Tel.: +20 2 5560645; fax: +20 2 5548020. E-mail address: samynki@yahoo.com www.elsevier.com/locate/enconman Available online at www.sciencedirect.com Energy Conversion and Management 49 (2008) 2384–2391