Enter the total solar radiation on the surface during the period and the maximum theoretical radiation during the same period into the Calculator. The calculator will evaluate the Clearness Index. 

Clearness Index Formula

CI = TSR / MR

Variables:

  • CI is the Clearness Index ()
  • TSR is the total solar radiation on the surface during the period
  • MR is the maximum theoretical radiation during the same period

To calculate Clearness Index, divide the total solar radiation on the surface by the maximum theoretical radiation during the period.

How to Calculate Clearness Index?

The following steps outline how to calculate the Clearness Index.

  1. First, determine the total solar radiation on surface during period. 
  2. Next, determine the maximum theoretical radiation during the same period. 
  3. Next, gather the formula from above = CI = TSR / MR.
  4. Finally, calculate the Clearness Index.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

total solar radiation on surface during period = 1.7

maximum theoretical radiation during the same period = 2.8