This study presents some comments on paper “Classification of solar radiation zones and general models for
estimating the daily global solar radiation on horizontal surfaces in China’’, [Energy Conversion and
Management, 2017.10.043.] proposed by Liu et al. (2017). In their paper, the selected 4 models were studied
before by Almorox and Hontoria (2004) in Spain and they did not present all discussion of their results which
indicated that the cubic model gave a slight improve rather than the quadratic and linear models. The proposed
general global solar radiation model is not new, it was developed and evaluated before by Rensheng et al.
(2006).