Prediction of clock time hourly global radiation from daily values over Bangladesh

(Abstract):  A need for predicting hourly global
radiation exists for many locations particularly in Bangladesh for which
measured values are not available and daily values have to be estimated
from sunshine data. The CPRG model has been used to predict values of
hourly Gh for Dhaka (23.770N, 90.380E), Chittagong (22.270N, 91.820E)
and Bogra (24.850N, 89.370E) for = ±7.50, ±22.50, ±37.50, ±52.50,
±67.50, ±82.50 and ±97.50 i.e., for ±1/2, ±3/2, ±5/2, ±7/2, ±9/2, ±11/2,
±13/2 hours before and after solar noon and the computed values for
different months are symmetrical about solar noon whereas for many
months experimental data show a clear asymmetry. To obtain improved
prediction, the hour angles corresponding to clock times have been used
in the model to take into account the difference between solar time and
clock time for each month for each station. Values of rG show the
morning-afternoon asymmetry and agree fairly well with experimental data
with standard deviation for different hours between 0.004 and 0.009.
The rms error is about 6% between 10:00 am and 2:00 pm.