United States Department of Energy

National Renewable Energy Laboratory

Electric & Hydrogen Systems Center

• "Live" data and plots, updated every 60 seconds (during the day).
• Daily plots and raw data files, are available from October 19, 2001 to yesterday.
• Solar Calendars, are available from October 2001 to the present month.
• Derived Spectral Data, are available since October 19, 2001, updated every 60 seconds (when ideal conditions exist).

The Atmospheric Optical Calibration System (AOCS) was developed at the National Renewable Energy Laboratory (NREL) to provide low-cost measurements of atmospheric optical and spectral solar irradiance conditions pertinent to photovoltaic (PV) device performance measurements. Optical properties of interest are molecular and aerosol scattering, aerosol absorption, water vapor absorption and the ratio of diffuse to global horizontal photon flux densities for the region 0.40 to 0.70 micrometer. Measurements are used as input to the SPECTRL2 model to estimate the spectral solar irradiance (0.3 to 4 micrometers) impingent on the device. Measurements using the AOCS will be used by the PV community to measure, in real time, the effects of atmospheric optical and spectral solar irradiance on device performance.

More information is available in the Atmospheric Optical Calibration System for Outdoor Testing of Photovoltaic Devices paper (1.11 MB PDF File).