Evaluation of turbidity coefficient and instability factor for Indian climate conditions

Abstract

SYNOPSIS This paper presents a methodology for evaluation of Linke turbidity coefficient (TR) and instability factor (α) for different Indian climate conditions, namely Chennai, Jodhpur, Kolkata, Mumbai and New Delhi (Table 1). Linear regression analysis has been used to evaluate TR, α and diffuse radiation constants (K1 and K2) by using measured data, taken from Mani's Data Book (1980) [1]. It is observed that for 8 to 9 sunshine hours, on estimation of TR, α, K1 and K2, the results are validated within an accuracy of 2% to 13% for beam radiation and 2% to 15% for diffuse radiation. The accuracy is reduced by the consideration of early morning and late evening sunshine hours because of higher air mass during these hours. It is also observed that for a lesser number of sunshine hours around solar noon, the accuracy is greater—8% to 1% for beam radiation and 6% to 1% for diffuse radiation (Table 7). This is in accordance with the fact that during winter conditions for all the stations, more than 90% of total daily radiation is during 8 sunshine hours around solar noon while the same is true for 10 sunshine hours during summer conditions (Table 8).