Alternate protection concepts for second surface silver/glass solar mirrors

Technical Report · Wed Oct 01 04:00:00 EDT 1980

DOI:https://doi.org/10.2172/6765476· OSTI ID:6765476

Buckwalter, C Q; Dake, L S; Hartman, J S; Lind, M A

Investigations into three technologies having the potential of significantly enhancing the durability of solar mirrors are reported. The approaches are based on the assumption that sealing the silver layer on second surface mirrors from the external environment with protective overcoats will significantly extend their useful service life. Considered are: (1) edge sealing a second sheet of glass over the silver layer using solder glasses, (2) overcoating the silver layer with liquid applied SiO/sub 2/ or TiO/sub 2/ coatings, and (3) overcoating the silver layer with an electroless nickel film. Preliminary experiments were performed using Sb/sub 2/O/sub 5/-K/sub 2/O and PbO based solder glasses to edge seal a second sheet of glass over the silver mirror surface. Problems encountered in the formulation of the Sb/sub 2/O/sub 5/-K/sub 2/O glasses forced abandonment of these low melting point solder glass experiments. Materials compatibility problems were encountered when using several of the commercially available PbO based solder glasses alternatives. A cursory evaluation of liquid SiO/sub 2/ and TiO/sub 2/ coatings was also undertaken. The films were applied as direct overcoats on both silver only and silver/copper mirror substrates. Although the process appeared to yield visually acceptable coatings, under microscopic examination the films were found to be porous and pinhole riddled after the final curing step. Consequently, they did not stand up well to salt spray and HCl vapor tests. Background data were collected in an investigation of overcoating the silver or silver/copper mirrors with an electroless deposited nickel film. Two formulations, one a basic solution, the other a commercial acidic solution, were attempted. Film integrity problems were encountered for fairly thick films in the feasibility experiments attempted. Nevertheless, the concept appears sound and merits further investigation.

• Research Organization: Battelle Pacific Northwest Labs., Richland, WA (USA)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 6765476
• Report Number(s): PNL-3629
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
141000* -- Solar Collectors & Concentrators
CHALCOGENIDES
COATINGS
COMPATIBILITY
ELEMENTS
EQUIPMENT
GLASS
LAMELLAE
METALS
MIRRORS
NICKEL
OXIDES
OXYGEN COMPOUNDS
PROTECTIVE COATINGS
SEALS
SERVICE LIFE
SILICON COMPOUNDS
SILICON OXIDES
SILVER
SOLAR CONCENTRATORS
SOLAR EQUIPMENT
SOLAR REFLECTORS
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
WEATHERING