The Durability of Solar Reflective Hard Coat Materials Produced on a Laboratory Scale Roll-Coater

摘要

Concentrating solar power (CSP) technologies use large mirrors to collect sunlight for conversion from thermal energy to electricity. The development of advanced reflector materials that are low cost and maintain high specular reflectance for extended lifetimes under severe outdoor environments is important to the viability of CSP systems. A promising low-cost material consists of a chrome-plated steel strip with a silver reflective layer protected by an alumina coating 2-4 microns thick. The alumina hard coat is deposited by ion beam assisted deposition (IBAD) under high vacuum. To demonstrate that the material can be produced continuously in a roll format, a laboratory scale roll coater was built to process 30.5-cm-wide strips. The advantage of a steel strip compared to polyester is that it withstands a higher process temperature and lowers the final product installation costs. Initial samples of reflective material were produced on steel strip with an alumina deposition rate of 10 nm/s. In general, the durability of these samples is excellent. Recent efforts have concentrated on increasing the alumina deposition rate to 20 nm/s and improving durability by adding various adhesion layers. The production and performance of these materials will be discussed.