Direct beam solar irradiance and illuminance

Abstract

In solving many practical problems, related to building etc correct assessment of direct beam Solar Irrandance and/or illumance is a necessary prerequisite. For this purpose computational methods' are usually adopted. Since 1940, When Parry Moon first collected and compared the necessary information and put them in usable from for, engineering applications, several studies on different aspects o f the subject have been made leading to new information. In the present paper more recent and reliable information on extra  terrestrial solar molecular and aerosol scattering of spectral energy, and the absorption of ozone, water vapour and carbon di oxide etc present in the terrestrial atmosphere, have been used to comput the spectra transmissivites and solar irradiance and illuminance normal to sun rays. The results presented in the form simple usuable curves, have been compared with other available data and some measured  values at Roorkee . It is believed that these will be useful from practical application point of view.