Thermisch-mechanische Optimierung eines Sekundärreflektors

Abstract

Secondary reflectors are flat, high-temperature mirrors that are attached to the top and bottom of the absorber of a solar power tower plant. They are used to further focus the incoming radiation and are exposed to high radiation flux densities. In this work, a concept for passive and active air cooling of these secondary reflectors was developed, dimensioned and thermally analyzed. Since the used mirror coatings are only stable up to approx. 400°C, it is examined at which reflectivity the developed concepts exceed this maximum temperature. The influence of the aiming offset and the flow velocity are examined using thermal, parametric FEM simulations. Based on the reflectance of current coatings, it can be shown that passive cooling of the secondary reflectors is only possible to a limited extent, which is why active cooling is recommended. Since the lower reflector experiences significantly lower flux densities, an adapted aiming strategy is proposed, which allows a more even load spread between the two reflectors. Based on the results of the thermal analysis, a design for the supply of cooling air was developed and optimized. To determine the electrical power consumption, the performance curve of the developed design was determined and the total power consumption roughly estimated.