Specular reflectance loss of solar mirrors due to dust accumulation

Conference · Sun Jan 01 04:00:00 EST 1978

OSTI ID:6849658

Pettit, R B; Freese, J M; Arvizu, D E

The specular reflectance properties of silvered glass mirrors have been studied after the mirrors experienced five weeks of outdoor exposure in Albuquerque, NM. The reflected beam profile from angular apertures of 3 to 15 mrad was determined from 400 to 900 nm using a bi-directional reflectometer. It was found that the main effect of the accumulated dust particles is to decrease the intensity of the specular beam while maintaining the same beam profile. At 500 nm, measured specular reflectance losses ranged from 6.5 to 24%. The diffuse reflectance outside an approximate 170 mrad cone around the specular direction was also measured from 320 to 2500 nm using an integrating sphere reflectometer. As expected, the reflectance losses determined from the two measurements were not in agreement. However, when properly normalized, the wavelength dependences of the reflectance loss determined by both measurements were identical for all areas measured. Thus it is possible to calculate the solar-averaged specular reflectance loss from a single measurement at 500 nm. For the silvered glass mirrors studied, the solar-averaged specular reflectance loss is equal to 0.78 +- 0.04 times the specular reflectance loss measured at 500 nm.

• Research Organization: Sandia Labs., Albuquerque, NM (USA)
• DOE Contract Number: EY-76-C-04-0789
• OSTI ID: 6849658
• Report Number(s): SAND-78-1169C; CONF-780550-7
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
141000* -- Solar Collectors & Concentrators
DUSTS
GLASS
LOSSES
MIRRORS
NEW MEXICO
NORTH AMERICA
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
REFLECTIVITY
SOLAR CONCENTRATORS
SOLAR REFLECTORS
SOUTHWEST REGION
SPECTRAL REFLECTANCE
SURFACE PROPERTIES
USA