Optimizing design of a Linear Fresnel Reflector for process heat supply

Lineal Fresnel Reflectors (LFR) is a promising technology in the field of concentrating solar thermal collectors which presents several advantages in comparison with the widely used parabolic-trough collectors (PTC). A methodology to properly design a LFR is presented as well as several issues arisen out the study of a particular case. As first step, a brief review was performed to select the proper receiver configuration, resulting in a trapezoidal cavity with multitube absorber receiver. Secondly, several stages of the optimized process were followed using an in-house ray tracer computer code to simulate the optical behavior of the system. Different characteristics, as width of the mirrors, number of rows, mirror geometry profile, height, length and configuration of the receiver. were optimized setting the power impinging in the absorber tube surface as the objective function. According to the results obtained, the shape of the mirrors was stablished based on the optical advantages that parabolic mirrors have over flatted ones. The point strategy was focused on achieving a homogeneous flux in the receiver tubes surface. The height of the receiver over the mirrors plane was selected as the one that maximizes the impinging power. A practical analysis related with the facilities characteristics was carried out to set the number and width of mirrors. In addition, a thermal balance between the impinging power and the thermal energy gained by the heat transfer fluid (HTF) was performed to calculate the length of the receiver tubes. Finally, the results of the analytical model were cross checked with a ray tracer software (Tonatiuh), with satisfactory results.