User's Manual for TMY2s

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This user's manual describes typical meteorological year (TMY) data sets derived from the 1961-1990 National Solar Radiation Data Base (NSRDB). Because they are based on more recent and accurate data and will make possible more accurate performance and economic analyses of energy systems, these data sets are recommended for use in place of earlier TMY data sets derived from the 1952-1975 SOLMET/ERSATZ data base.

To distinguish between the old and new TMY data sets, the new TMY data sets are referred to as TMY2s. TMY and TMY2 data sets cannot be used interchangeably because of differences in time (solar versus local), formats, elements, and units. Unless they are revised, computer programs designed for TMY data will not work with TMY2 data.

The TMY2s are data sets of hourly values of solar radiation and meteorological elements for a 1-year period. Their intended use is for computer simulations of solar energy conversion systems and building systems to facilitate performance comparisons of different system types, configurations, and locations in the United States and its territories. Because they represent typical rather than extreme conditions, they are not suited for designing systems to meet the worst-case conditions occurring at a location.

The TMY2 data sets and this manual were produced by the National Renewable Energy Laboratory's (NREL's) Analytic Studies Division under the Resource Assessment Program, which is funded and monitored by the U.S. Department of Energy's Office of Solar Energy Conversion.


Thomas D. Bath, Director                  Dave Rennè, Manager
Analytic Studies Division                   Resource Assessment Program


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