Development of an Analytical Optical Method for Linear Fresnel Collectors

An analytical optical approach-. First-principle OPTical Intercept Calculation (FirstOPTIC)-is developed for the optical performance evaluation of linear Fresnel collectors. Instead of treating all optical error sources as probability distributions and convolving them with the sun shape into an overall beam spread function, FirstOPTIC treats mirror slope error, receiver position error, and collector tracking error as geometric modifications to the collector, as interpreted in laboratory measurements. Calculation of intercept factors is analytically derived through a rigorous mathematical model. It is shown through test cases that FirstOPTIC can provide accurate and fast calculation of collector intercept factors as a function of incidence angle. Finally, FirstOPTIC is used to conduct analysis on the incidence angle modifier (IAM) and indicates that the factorized IAM representation with respect to independent transversal and longitudinal components can be a good approximation but in general underestimates the optical performance of a linear Fresnel collector.