COMPARISON OF METHODS FOR ESTIMATING DAILY AND HOURLY DIFFUSE SOLAR-RADIATION

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.