Johannes Wette

Correlating outdoor exposure with accelerated aging tests for aluminum solar reflectors

Guaranteeing the durability of concentrated solar power (CSP) components is crucial for the success of the technology. The reflectors of the solar field are a key component of CSP plants, requiring reliable methods for service lifetime prediction. So far, no proven correlations exist to relate accelerated aging test results in climate chambers with relevant CSP exposure sites. In this work, correlations have been derived for selected testing conditions that excite the same degradation mechanisms as for outdoor exposure. Those testing conditions have been identified by performing an extensive microscopic comparison of the appearing degradation mechanisms on reference samples that have been weathered outdoors with samples that underwent a high variety of accelerated aging experiments. The herein developed methodology is derived for aluminum reflectors and future work will study its applicability to silvered-glass mirrors.

Sandstorm Erosion Simulation on Solar Mirrors and Comparison with Field Data

Solar reflectors for concentrating solar power applications can be subject to performance losses due to their permanent exposure to the environment. In this work the risk of erosion due to sandstorms is evaluated. Aluminum and glass reflector samples were exposed in Missour and Zagora (Morocco) and measurements of the wind velocity and the particle concentration were carried out. Both measured quantities were connected to the single particle momentum distribution SPMD. This novel parameter is shown to be adequate to describe the erosion characteristics of outdoor sites and laboratory setups. Its deduction will be explained and it will be applied to both outdoor sites and two accelerated erosion simulation setups, a sand trickling device -named soil pipe- and a closed loop wind channel with particle injection. Furthermore different erosion failure modes are described and explained by the use of the SPMD.