Development of diffuse solar radiation models using measured data

ABSTRACT

The proper designing and monitoring of solar application require accurate estimation of solar diffuse radiations. In this study, new empirical models are developed from for four selected cities: Karachi, Multan, Quetta, and Peshawar, representing four provinces of Pakistan with the help of recently measured data under Energy Sector Management Assistance Program (ESMAP) of World Bank. Sky-clearness index is selected as an input parameter because of close correlation with the diffuse fraction. Models are developed from six different groups available in the literature for daily radiations. Nine statistical indicators are analyzed to select the best-suited model. Results show that the best-suited model for Karachi, Multan, Quetta, and Peshawar is cubic, exponential, cubic, and quadratic, respectively. In general, polynomial models show better estimate, whereas logarithmic models show the worst results for every case. This study would be helpful for proper design, evaluation, and parametric studies of solar applications throughout the country as well as useful for locations with similar climatic conditions.

KEYWORDS:

• Diffuse fraction
• ESMAP
• Pakistan
• sky-clearness index
• statistical analysis

Acknowledgments

We would like to thank the Energy Sector Management Assistance Program (ESMAP) of The World Bank Group, U.S., Ministries, and Departments under the Government of Pakistan for their public reports, secondary data, and kind cooperation. Also, we would like to show our gratitude to the editor and anonymous reviewers for their suggestions to improve the manuscript.