Solar radiation data have been acquired over approximately a five to six year period (1996–2002) at 15 sites in Texas (Texas Solar Radiation DataBase—TSRDB). These data are compared with comparable sites in the National Solar Radiation DataBase (NSRDB). Comparisons of the TSRDB and NSRDB data for eleven (11) coincident or nearby locations show reasonably good agreement between their global horizontal values. The monthly average differences range from −18 to +13%, and the annual average differences vary from −10 to +8%. The differences are ratioed to TSRDB values and positive differences represent larger TSRDB values. Across the sites, the TSRDB global horizontal annual data are about 3% lower than the NSRDB. However, there are considerable differences in the direct normal values, with TSRDB generally being higher. Monthly average differences range from −17 to +41%, and the average annual differences range from −10 to +20%. Across the sites, the TSRDB direct normal annual data are about 6% higher than the NSRDB. The greatest deviations for direct normal data are for coastal locations in the winter, with the three compared coastal locations exhibiting an average difference of about +29% for the combined months of December and January. Also, the TSRDB data for the Trans-Pecos region in west Texas exhibits significantly higher direct normal solar radiation throughout the year (22%) than does the NSRDB.

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