This comment comes from a physicist, so I may be more critical that the average bear.
To begin with, antireflective coatings have been around for a long time. The trick with antireflective coatings is as follows: (1) Even if the material (e.g. low iron glass) absorbs ~1% of the light incident on it, at the "boundary" between the air and glass, light will be reflected due to a "mismatch in the index of refraction". This reflection depends on the angle of incidence, and depends on the polarization of the light (direct sunlight is unpolarized). (2) For example a 3 mm (1/8") thick sheet of low iron glass will average 89% transmittance and 8% reflectance of "solar energy" (over that part of the spectrum that Si solar cells are most sensitive). If a single layer is used, the material used for the antireflective coating has to have an index of refraction that is half way between 1.0 (air) and glass (~1.45) or 1.23 and be 110 nm thick. Although not a perfect match, MgF2 (index equal to 1.38) is commonly used. Teflon is an excellent coating but it is easily scratched and difficult to apply in films as thin as 110 nm. (3) Coating the glass has to be tightly controlled and I doubt this would work as a DIY project. So I am pretty sure that this coated glass would improve the transmission, but I am very skeptical about it protecting underlying glass and I would be very surprised if it more scratch resistant that regular float glass. On the contrary, I would expect the coated glass to require special handling and be LESS environmentally robust. - Peter Peter T. Parrish, Ph.D., President California Solar Engineering, Inc. 820 Cynthia Ave., Los Angeles, CA 90065 CA Lic. 854779, NABCEP Cert. 031806-26 <mailto:[email protected]> [email protected] Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 _____ From: [email protected] [mailto:[email protected]] On Behalf Of Keith Cronin Sent: Saturday, December 05, 2009 10:09 AM To: RE-Wrenches Subject: [RE-wrenches] Antireflective coatings http://www.ecmag.com/?fa=article <http://www.ecmag.com/?fa=article&articleID=10827> &articleID=10827 Do any of you have any comments on the efficacy of these types of products?
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