ABSTRACT
A basic knowledge of certain key solar radiation concepts is essential to proper building design. Solar radiation contributes greatly to peak summer building loads and also to annual energy consumption. The radiation received by a surface depends on the solar incidence angle and also on local climatic parameters. Accordingly, we begin by presenting solar geometric relationships. This is followed by a discussion of extraterrestrial insolation, which is the basis of most insolation models. Subsequently, we treat terrestrial solar radiation, including the separation of direct and diffuse components needed to calculate the insolation on tilted surfaces. We then describe the most recent American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) clear-sky model adopted by the building energy profession (meant for peak-day calculations) along with the isotropic and the ASHRAE anisotropic sky models for computing insolation on tilted surfaces. Finally, we present various statistical correlations between different long-term average solar insolation quantities.
