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Optical Properties Measurement

The last ten years has seen a surge in technology for solar and other alternative energy forms. This revival has led to the revision and reinstatement of a previously withdrawn ASTM standard, E903, Test Method for Solar Absorptance, Reflectance and Transmittance of Materials Using Integrating Spheres.

E903 is now under the jurisdiction of Subcommittee E44.20 on Glass for Solar Applications, part of ASTM International Committee E44 on Solar, Geothermal and Other Alternative Energy Sources. The standard covers the measurement of spectral absorptance, reflectance and transmittance of materials using spectrophotometers equipped with integrating spheres.

“Since 2003, there has been tremendous growth in solar energy systems technology, along with new developments in materials science related to solar energy, windows technology and thermal energy management films,” says Daryl Myers, an ASTM member who is retired after 37 years with the Electricity, Resources and Building Systems Integration Center at the National Renewable Energy Laboratory. “This is especially so for the glass industry. The increasing interest in this technology has been accompanied by a need to measure and report the optical properties of materials as weighted by various example or reference solar spectral distributions.”

According to Myers, different materials, such as formulations of window glass or solar panels, cover materials, heat management films and optical components in solar energy systems perform differently as the solar spectrum changes. E903 is used to provide objective assessment of the properties of materials under various realistic solar spectral variations.

The standard establishes uniform criteria for measurement procedures, equipment and reporting of results with respect to modern measurement equipment. E903 will be used by manufacturers of glass, coatings, films and optical components of solar energy systems elements to assess the reliability, durability and performance of these components in order to optimize the entire materials system performance.

Properties of interest that can be measured via E903 include transmittance of glass, absorption coefficients of solar thermal receiver paints and materials, and improvements in the collection of photons for photovoltaic systems by use of textured cover glasses.

All interested parties are invited to join in the standards developing activities of E44.

To purchase ASTM standards, visit www.astm.org and search by the standard designation, or contact ASTM Sales (phone: 877-909-ASTM; sales@astm.org).

CONTACT Technical Information: Daryl Myers • Arvada, Colo. • Phone: 303-431-7650 | ASTM Staff: Christine DeJong • Phone: 610-832-9736 | Upcoming Meeting: June 26-27 • In conjunction with D02 June meeting • Montreal, Quebec, Canada

This article appears in the issue of Standardization News.