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NREL - National Renewable Energy Laboratory
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NREL's solar radiation research staff provides expertise in renewable energy measurement and instrumentation. Major capabilities include solar resource measurement, instrument calibration, instrument characterization, and solar monitoring training.

Solar Resource Measurement

NREL's solar radiation research staff collects high-quality solar resource and surface meteorological data. Since 1981, researchers have continuously gathered basic solar radiation information, and they now gather high-resolution data (in 1-minute intervals) from World Meteorological Organization first-class instruments. Staff also perform daily instrument maintenance and annual calibrations to ensure data quality.

Measurement activities support a number of Department of Energy renewable energy programs as well as its Atmospheric Measurement Program, which applies radiometry to climate change research. To learn more about NREL's solar radiation measurement capabilities and results, see the related data and resources.

Instrument Calibration

NREL's metrology staff calibrates hundreds of instruments annually to ensure data quality. Calibration involves comparing an instrument output signal with a measurement standard traceable to a recognized standard to identify and eliminate deviations in accuracy. Calibration therefore allows researchers to compare data from different sources, be confident in those data, and produce better estimates of the uncertainty of a measuring instrument, system, or process.

Calibration traceability is the ability of a measurement to be related to national or international standards through an unbroken chain of comparisons with stated uncertainties. Traceability also ensures data quality and is an important part of NREL's calibration activities.

NREL's calibration facilities include a metrology laboratory and an optical metrology laboratory that offer well-maintained measurement references, optimum instrument mounting platforms, and automatic data acquisition systems for electrical, temperature, pressure, and optical properties. Staff performs annual comparisons of absolute cavity radiometers to transfer World Radiometric Reference to researchers around the world. Staff also performs Broadband Outdoor Radiometer Calibration to calibrate pyranometers and pyrheliometers using specialized software for process automation and quality assurance.

In addition, the NREL metrology team can provide:

  • Quick turnarounds (2–3 days) for calibrations
  • In-house technical assistance for measuring techniques and uncertainty evaluation
  • Special calibrations for limited instruments usage
  • Calibration data sheets with "before" and "after" data for corrective-action applications
  • A notification system to identify instruments due for calibration
  • Certificates and data for accreditation.

Because of its expertise and facilities, NREL metrology staff can provide calibration services at 25% less than most vendors and work directly with outside metrologists to ensure calibration quality can be easily monitored.

Instrument Characterization

NREL also characterizes new instruments used to measure renewable energy resources. Researchers maintain procedures and calibration equipment traceable to national and international standards for electrical, pressure, temperature, and optical radiation measurements.

Solar Monitoring Training

Because the solar radiation research team is committed to open access to scientific data, it trains other researchers in solar monitoring network design, operation, and maintenance. Staff also provides training for meteorological measurements and experiment design. In addition, the solar radiation research team develops solar radiation research data-quality assessment procedures.