diff --git a/src/thermophysicalModels/radiation/submodels/solarCalculator/solarCalculator.H b/src/thermophysicalModels/radiation/submodels/solarCalculator/solarCalculator.H
index ca7c7a3746884eb139595de076f93ed912b63669..ecc67329d4d16e3219a6090e7b6cb00fbd226e43 100644
--- a/src/thermophysicalModels/radiation/submodels/solarCalculator/solarCalculator.H
+++ b/src/thermophysicalModels/radiation/submodels/solarCalculator/solarCalculator.H
@@ -62,7 +62,8 @@ Description
 
             In this model the flux is calculated as:
 
-                directSolarRad = skyCloudCoverFraction*A/exp(B/sin(beta));
+                directSolarRad =
+                    (1 - skyCloudCoverFraction^3)*A/exp(B/sin(beta));
 
     3) SunLoadTheoreticalMaximum: The entries are:
             Setrn