In addition to the solar radiation database table provided for most cities in the USA and Canada in Chapter 4, there is data available for global use available at: eosweb.larc.nasa.gov/sse/.
This site will lead you to numerous other websites, maintained by the National Aeronautics & Space Administration (NASA), that provide extensive data and maps dealing with solar radiation. PV solar energy system contractors and developers all over the world use NASA solar radiation data widely. Users will need to create a login for the NASA website. Then you’ll be able to connect to the following URL: eosweb.larc.nasa.gov/cgi-bin/sse/register.cgi.
In the United States, a major program was undertaken by the National Renewable Energy Laboratory to correlate solar radiation data that can be 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 following website: 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. Extensive maps from the data represented in the tables are also available for viewing.
Another valuable source for solar radiation data is provided by Solar Data Warehouse, whose URL is as follows: www.solardatawarehouse.com/Data.aspx. This group provides regularly updated solar data from 5,000 US ground stations and over 3,500 overseas ground stations. The site includes good coverage for most of Europe, South America, Asia, and Africa. Solar Data Warehouse claims that their solar data contains less than half of the errors typically found in satellite and “modeled data,” and they offer proof of this impressive assertion.
Another excellent source for solar data in the US is provided by an organization called Solar Pathfinder here: www.solarpathfinder.com/solar_radiation.
One of the principal sources for European solar radiation databases is provided by the group Satel Light at this URL: www.satel-light.com/indexes.htm.
Another good source of surface solar radiation satellite data for Europe, Africa, the Atlantic Ocean, and much of South America is provided at: climate dataguide.ucar.edu/climate-data/surface-solar-radiation-europe-africa-and-atlantic.