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Uncertainty Evaluation

Once approved, WK36479 will be used to test large samples of radiometers.

A proposed new ASTM International standard will improve the accuracy and usefulness of radiometry-related uncertainty estimates in a wide range of fast developing solar renewable energy applications, such as system performance and acceptance testing, resource assessment and solar energy system design engineering.

The proposed standard, WK36479, Practice for Uncertainty Evaluation of Calibration and Measurements with Pyranometers and Pyrheliometers, is being developed by Subcommittee G03.09 on Radiometry, part of ASTM International Committee G03 on Weathering and Durability.

“The emerging importance of solar energy conversion systems in the U.S. and world energy economies requires accurate statements of uncertainty in the assessment of available solar radiation resources, which impact conversion system design and performance data, and outdoor testing of materials in such systems, as well as for general materials degradation studies,” says Daryl Myers, chairman of G03.09, and recently retired after 33 years of service at the National Renewable Energy Laboratory. “These measurements are based on solar radiometers of widely varying design and performance.”

According to Myers, while manufacturers quote accuracy specifications for their instruments, the derivation of these specifications is often unstated or unknown. The proposed standard will provide the means for manufacturers to develop uncertainty statements in a documented fashion.

“Specific applications, such as solar radiation monitoring during outdoor weathering of materials, solar resource assessment, solar energy system design data, solar energy system performance data or making measurements appropriate for generating solar resource or system performance forecasts, require different levels of accuracy or uncertainty,” says Myers. “A common frame of reference for the uncertainty statements quoted by manufacturers will improve user ability to choose appropriate instrumentation and confidence in the data that the instrumentation provides.”

Myers says that the task group developing WK36479 is looking for active participation from solar radiation measurement manufacturers and solar energy system design and operating engineers.

“G03.09 is active in developing proposed standards related to solar radiometry for indoor and outdoor weathering and durability testing, solar energy conversion system testing and measuring optical properties of materials,” says Myers. “Experts in these areas are always invited to make contributions to developing and/or revising standards to meet the needs of these manufacturing and research communities.”

CONTACT Technical Information: Daryl Myers • Arvada, Colo. • Phone: 303-431-7650 | ASTM Staff: Jeffrey Adkins • Phone: 610-832-9738 | Upcoming Meeting: June 24-26 • In conjunction with D02 June meeting • San Francisco, Calif.

This article appears in the issue of Standardization News.