A novel design for linear beam-down technology: retrofitting solatom’s linear fresnel solar field

This paper presents a novel design for Beam-Down Linear Fresnel Reflector (BDLFR) technology. An unprecedented bifocal aiming strategy is applied to Solatom’s LFR solar field to generate a BDLFR system. Previous studies aimed the solar irradiation towards a single focus line, which caused a wide secondary reflector with an empty space, or gap, in the symmetry axis. The novel bifocal aiming design eliminates this gap, resulting in a narrow secondary reflector that minimizes shading losses. The innovative method uses two dimensionless parameters for the design process and maintains the advantages of BDLFR technology for heating high-density materials on a ground solar receiver. The geometry of the secondary reflector, i.e. the position, width and inclination of the mirrors, and the ground-receiver width are calculated in Matlab, while solar field is simulated using SolTrace, a Monte-Carlo ray tracing software. The design methodology is applied to an existing LFR solar field to retrofit it into a BDLFR. The LFR solar field is composed by 8 mirrors of 0.5 m width and North-South orientation. The results reveal that this new design can achieve a concentration ratio of up to 15.33 suns and optical efficiencies of up to 84.58% for a receiver width of 0.23 m assuming ideal reflectivity. By incorporating optical errors (3 mrad slope and 1.5 mrad specularity) and 90% reflectivity in both primary and secondary mirrors, the energy yield is 0.772 MWh/m 2 in the latitude 40.332° (Leganés, Spain) and 0.407 MWh/m 2 in the latitude 47.163° (Iasi, Romania).