Daily and hourly diffuse radiations measured using a pyranometer and s
hading ring have been compared with the values calculated using severa
l correlations. For the daily diffuse radiation, the correlation of Du
ffie & Beckman (Solar Engineering of Thermal Processes, John Wiley, 19
80), Liu & Jordan (Solar Energy, 4(3) (1960) 1-19), Erbs et al., (Sola
r Energy, 28 (1982) 293) and Bruno (Solar Energy, 20(1) (1978) 97-100)
have been used while the hourly diffuse radiation was calculated usin
g the correlations of Hottel, Orgill & Holland (Solar Energy, 19 (1977
) 357) & Liu Jordan. It has been uniformly observed that Liu and Jorda
n's method may be considered a suitable method for the estimation of d
aily and hourly diffuse radiations in clear-sky conditions in the plai
n areas of northern India.