2. Materials and methods
2.1. Mathematical model
In this section, the mathematical model for attaching an STSC to a Stirling engine is developed using the mathematical estimation of the intercept factor for an STSC, which considers the optical and geometric models and incorporates the thermal model of a cavity receiver in accordance with the following considerations: the distribution of the solar image at the focal point corresponds to a normal distribution; the temperature inside the receiving cavity is evenly distributed; the heat transfer analysis is performed under stable conditions and is one-dimensional; the material properties remain constant; and the mathematical model begins by using Eq. (1), described by Duffie and Beckman [16], which estimates the amount of energy captured by a cavity receiver.