倾斜面上直射辐射计算方法的探讨

在太阳能系统的设计中常涉及倾斜面上日总直射辐射的计算。计算倾斜面上日总直射辐射最常用的方法是Liu and Jordan所提出的数学方法,该方法是在假设地球表面没有大气层的情况下得出的,是一个典型的近似计算方法。研究通过直接数值积分和Collares-Pereira and Rabl辐射计算经验关系对Liu and Jordan计算方法的正确性进行分析。结果表明：Liu and Jordan所提出的计算倾斜面上日总直射辐射的方法存在明显的计算误差,误差的大小与倾斜面的倾角和方位角有关,且方位角越大,计算误差越大;对于垂直表面,计算误差随着方位角的增加迅速增加,当方位角偏离正南90度时,由Liu andJordan方法所计算出的年总直射辐射误差高达20%以上。

On the calculation of daily beam radiation on tilt surfaces

In practical applications, it is essential to calculate the daily beam radiation on a tilt surface. The widely used correlation for the calculation of daily beam radiation on a tilt surface is the one suggested by Liu and Jordan. However, the method of Liu and Jordan was developed based on the assumption of no atmosphere over the earth, and is a typical approximate mathematical method for the estimation of daily beam radiation on tilt surfaces. The objective of this work is to validate the correlation of Liu and Jordan by direct numerical integration of beam radiation on any surface based on the correlations suggested by Collates - Pereira and Rabl. Results indicate that Liu and Jordan correlation are not accurate for estimating daily beam radiation on tilt surfaces, especially for those surfaces with high tilt and azimuth angles. Results also show that the relative deviation for the calculation of annual beam radiation collection on tilt surfaces by the method of Liu and Jordan increases with the increase in azimuth angle of a vertical wall with a maximum value of over 20% for western or eastern vertical surfaces.