Erosion of mirrors in desert enviornments

Abstract

To guarantee the long-term efficient operation of concentrating solar power (CSP) plants the durabil-ity of the components is of major importance. Therefore various metrological and geological factors need to be taken into account. One threat to the performance of reflectors is represented by sand and dust storms in desert environments. To simulate general outdoor effects procedures have already been developed which are standard prac-tice, like the salt spray test (ISO 9227 [1]) for humidity in marine environments, ISO 16474 [2] for long-term radiation and alternating humidity stress or the IEC 61215 [3] for the simulation of thermal cycles. No standard is available to predict on the spectral reflectance loss of mirror materials during sand or dust storms. The existing abrasion standards (MIL-STD-810 G [4], ASTM D968-05 [5] and ASTM F1864-05 [6]) do not represent a realistic picture of the impact of eolian sand and dust parti-cles. One reason for the so far unsuccessful simulation is that the physical parameters present in such rare natural events are still unknown. In this work, field data from a meteo station in Missour (Morocco) is collected and the extracted insights about physical parameters like particle size distribution, particle shape and crystallographic composition, etc. of the collected material are given. For this purpose, optical particle detectors and one active dust sampler are installed on site. Furthermore, different methods to simulate erosion ef-fects under laboratory conditions are applied. The advantages and limitations of each setup are ex-plained and first test results are shown. The aim is to formulate a standardized process and verify its results with the observed effects on outdoor exposed reference materials.