ASTM Subcommittee Sets Solar Terminology
The ASTM E44.20 Subcommittee Glass for Solar Applications met in early
July to further discuss the creation of standards and guides for the solar
The group began with a review of work item “Edge Classifications for Glass
Used in Solar Applications,” led by Wayne Boor of PPG Industries. During
the group’s last meeting it had heard a proposal to use SAE J673, a standard
that describes the different edge types used in the auto glass industry,
to define edges for solar glass. However, it was quickly realized that
the architectural glass, solar module and even aluminum industries had
different terms to describe various edge shapes, finishes and defects.
The group’s task is to provide names for these edge characteristics, rather
than to provide information on edge strength, which should be a work item
for the future, suggested subcommittee chair Doug Hall of Corning Inc.
Hall noted that the point was to classify the terms, not set tolerances,
in order to be able to have conversations with others about tolerances
The group agreed on five edge shapes to begin to classify. The group will
look to the Glass Association of North America’s Glazing Manual to gather
terms already in use for these shapes, as well as for the finishes and
A discussion of descriptions and terms for the treatment of glass corners
began. “This is an area that’s new to the glass industry. Generally speaking,
there really is no corner designation in any standard I’ve ever seen.
However in the solar industry it is important,” Boor said.
The group came up with a list of the terms they’ve seen used to refer
to corners and then whittled it down to two—dubbed and rounded—upon agreeing
that most names agree to one of these two treatments.
Terms for glass classification came up again later in the meeting as the
group met to discuss a guide to solar glazing terminology. The guide defines
types of glass by its composition, but when it came to the portion of
the outline setting out to define iron composition, specifically, what
percentage of iron makes a glass mid-, low- or ultra-low-iron, the glass
industry spoke out. Representatives of AGC, Cardinal and Guardian agreed
that what customers request is a certain visible light transmittance,
not iron content, and that to get to those specifics of the iron composition
would be to share what sets their solar glazing products apart from competitors.
The subcommittee addressed several other issues. Daryl Myers with the
National Renewable Energy Laboratory gave a presentation urging the group
to support the reinstatement of ASTM E903, Standard Test Method for Solar
Absorptance, Reflectance and Transmittance of Materials using Integrating
Spheres. This test method, which essentially “died” in 1996 due to lack
of re-balloting, covers the measurement of spectral absorptance, reflectance
and transmittance of materials using spectrophotometers equipped with
integrating spheres. Myers noted that these properties are important in
all solar energy systems.
It also began the first steps in drafting a “New Guide for Durability
and Reliability Issues of Glass and Coated Glass Used in Solar Energy
Products.” The current work item is intended to serve as an educational
document for manufacturers of solar energy products and to help E44.20
learn where future standards might be needed.
© Copyright 2010 Key Communications Inc. All rights reserved.
No reproduction of any type without expressed written permission.