Obtaining Solar Radiation Data

Data for USA (NREL - National Renewable Energy Lab)

Please Note: The Solar Pathfinder Assistant software has the NREL solar radiation data already in it.

In the United States, a major program was undertaken by NREL (National Renewable Energy Lab) to correlate sparse solar radiation data with available weather data at nearby sites. These correlations were used to estimate solar radiation for 239 sites in the US with extensive weather records. The data for the 239 sites is available in an excellent 250-page publication called Solar Radiation Data Manual for Flat-Plate and Concentrating Collectors. The data is available in HTML and PDF format from the website http://rredc.nrel.gov/solar/pubs/redbook. Individual PDF files are available for the main body of the manual and for each of the 50 states, the Pacific Islands (Guam) and Puerto Rico. Compressed files containing the individual PDFs for the manual and the site data tables can be downloaded in three compression formats: PC, Macintosh and Unix. Maps derived of the data represented in the tables are also available for viewing.

NREL is an excellent resource, and though it tends toward the large utility scale projects, it is funded by your tax dollars. If you have additional technical questions, try 303-275-4626 or 4648. Like most NREL numbers, you will likely get a machine.

The manual mentioned above has a page of tables for each location. The data tables have columns for each month of the year and an annual total. There are five tables: southfacing fixed-tilt collectors, 1-axis trackers, 2-axis trackers, direct-beam concentrating collectors, and average climatic conditions. Units are metric (kilowatt-hour per square meter per day). Most tables give average, maximum, and minimum values for each month. The fixed and 1-axis tracker tables are broken down into tilts of: horizontal, latitude minus 15 degrees, latitude, and latitude plus 15 degrees.

Data for Global Use (NASA)

The data is available at: https://eosweb.larc.nasa.gov/sse/
Detailed information on how to obtain solar radiation data from this NASA site:

Word file How to obtain Solar Radiation Data (Word)