Models for daily global solar radiation for the Caribbean island of Trinidad

In this study, calibration and validation data sets from 2001 to 2005 and 2006 to 2010, respectively, were used to develop various Angstrom-Prescott models.  The models created were: (i) A five-year model and (ii) five-year dry and wet seasonal models, to calculate monthly average daily global horizontal irradiation;  (iii) twelve monthly models to estimate average daily global horizontal irradiation; and (iv) ten yearly models for each year in the period 2001–2010.   All models were evaluated using common statistical indicators and good agreement was found between the measured and calculated values and hence these models proved to be suitable for use in Trinidad. Notably, the five-year model was found to be adequate in modelling the dry and wet seasons, and so specific dry and wet season models are not necessary.

The twelve monthly models yielded a linear relationship between the regression coefficients, b and a, over a one-year time scale. Similarly, the ten yearly models also yielded a linear relationship between b and a over a ten-year time scale.

Using the full data set, 2001–2010, the average daily global solar radiation, average total global solar radiation, average daily number of sunshine hours, and average total number of sunshine hours were determined.