Effects of outdoor exposure on the solar reflectance properties of silvered glass mirrors
The specular reflectance properties of silvered glass heliostat mirrors have been studied during a 15 month period of exposure to outdoor weather conditions. A bidirectional reflectometer was used to measure the reflected beam profile at wavelengths of 500, 700, and 900 nm, with an incident angle of 20/sup 0/. Data were obtained by measuring exposed samples at two-day intervals. It was found that weather conditions such as wind and rain could decrease or increase the reflectance of a mirror. The largest decrease in reflectance for a two-day period was 0.06 reflectance units, while the largest increase for a two-day period was 0.083 reflectance units. A snow storm restored an exposed mirror's specular reflectance to within 0.01 reflectance units of the initial value obtained after the laboratory ultrasonic cleaning. Because of varying weather conditions, it is very difficult to take a short-term cleaning cycle result and predict the reflectance loss for a longer period of time. In long-term exposure tests, where the mirrors were never cleaned, the specular reflectance gradually decreased while being modulated by occasional sudden changes which corresponded to snow or rain weather conditions.
- Research Organization:
- Sandia Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- EY-76-C-04-0789
- OSTI ID:
- 6273455
- Report Number(s):
- SAND-78-2072C; CONF-790541-30
- Resource Relation:
- Conference: International Solar Energy Society meeting, Atlanta, GA, USA, 28 May 1979
- Country of Publication:
- United States
- Language:
- English
Similar Records
Optical losses of solar mirrors due to atmospheric contamination at Liberal, Kansas and Oologah, Oklahoma
Enhancement of Optical Efficiency of CSP Mirrors for Reducing O&M Cost via Near-Continuous Operation of Self-Cleaning Electrodynamic Screens (EDS). Final Report