Textile-based solar thermal energy collectors (TSTECs) are one kind of novel flexible solar thermal harvesting products, which can be widely applied in the fields of building roofs and facades. In this paper, a proposed numerical model was developed to calculate the solar energy harvesting performance of textile-based solar thermal energy collectors with different layers of textile composites. Also, the outdoor tests were performed to confirm the effectiveness of the designed system and to validate the simulation results. It is found out that the numerical results showed a good agreement with the experimental results. As a consequence, the developed numerical model serves as a useful tool to predict and design the most promising and optimal performance of TSTEC with high efficiency. This research brings some progress in the field of textile-based solar thermal energy harvesting products and they can potentially extend to be widely used in an industrial application that needs heating supply in low-to-medium temperature level. (C) 2018 Elsevier Ltd. All rights reserved.