The gap angle as a design criterion to determine the position of linear Fresnel primary mirrors

Abstract

A common choice for Linear Fresnel Reflector primary mirrors is the so-called uniform configuration, in which a constant value of mirror width e and their relative distances e is used. Often, it results in large relative mirror distances, leading to significant losses of etendue and concentration due to the light lost between the mirrors. In this paper a method to optimize the position of primary mirrors is presented with the goal of producing a more continuous primary optic, eventually closer to the theoretical limits of solar concentration. This calculation was done for two Linear Fresnel Reflector concentrators with uniform configurations, exploring how this method can improve the performance of such systems. This paper analyses the impact of such modifications on the overall optical performance of the collector, through the calculation of Concentration-Acceptance Product, Incidence Angle Modifier curves and an estimation of the total amount of collected energy for a specific location, Faro (Portugal). For the analyzed cases, the simulation results show that the proposed method produces denser primary fields, with an increase up to 21% in mirror area and collecting up to 14% more energy.