Estimation model for global solar radiation in Lebanon

Availability of solar radiation data is very scarce in Lebanon and it is often not accessible. The estimation of solar data is the most important parameter for designing and developing various solar energy systems such as photovoltaic, solar water heater and concentrated solar power. The main objective of this paper is to present a comparison between different estimation models for global solar radiation based on sunshine duration applicable in Lebanon. Subsequently a new correlation is proposed to estimate the monthly average daily global solar radiation in Lebanon. Measured data were obtained from photovoltaic system installed on the roof of the Industrial Research Institute during 2013-2015. Estimated data of seven previous models and a proposed coefficients model, are compared to measured data based on the root mean error, the main bias error and the maximum permissible error. The results of using the new coefficients revealed that the error is minimized, and this new correlation can be used to predict the monthly mean average daily global solar radiations.