The objective of this paper is to present experimental results on distribution characteristics of solar irradiation absorbed by the narrow channel wall of desiccant rotor. Experiments are performed with the channel made by silica gel and poly propylene (PP). Energy absorption rate was measured in conditions of different channel lengths, incident irradiation angles, air temperatures and humidity. The measurements for silica gel were almost equal to the result of previous study which was conducted using laser light as a source. Therefore, the prediction model to evaluate the absorption rate of laser light can be used for this solar light system. However, the rate of laser for PP was larger than that of solar. We improved a prediction model for PP. These models are useful to predict desorption rate of water vapor in a rotor in order to investigate a mathematical model for the rotor heated directly by concentrated solar irradiation.