Calculation and Analysis of Optimal Tilt Angle for PV/T Hybrid Collector

The use of solar energy received world wide attention in recent years. Solar energy is a free and clean natural resource which can be utilized by using a solar collector. In this paper, a model was presented for the calculation of the optimal tilt angle in Changsha. The anisotropic Hay's model of the sky was selected and by combining it with standard formulas for the two remaining components. The yearly optimal tilt angle and monthly optimal tilt angles for a solar collector were calculated using the aforementioned model. Then, the total collectible radiations on the collector surface with different kind of optimal tilt angles, such as yearly optimal tilt angle, monthly tile angle and local latitude, were calculated and compared. The results show that the yearly optimal tilt angle for a solar collector in Changsha is 19.22 degree near 10 degree less than the site latitude. Choose the optimal tilt angle can effectively improve the annual collectible radiation of a solar collector. Taking adjusted monthly optimum tilt angle and fixed yearly optimal angle, compared to the tilt angle of site latitude angle, the annual collectible radiation per square meter per year for a solar collector increase in 208.89MJ and 90.55MJ, enhance by 5.2% and 2.2 %, respectively.