Users Manual for TMY3 Data Sets

1 A national laboratory of the Department of EnergyOffice of Energy Efficiency & Renewable EnergyNational Renewable Energy Laboratory Innovation for Our Energy Future Users Manual for TMY3 Data Sets S. Wilcox and W. Marion Technical Report NREL/TP-581-43156 Revised May 2008 NREL is operated by Midwest Research Institute Battelle Contract No. DE-AC36-99-GO10337 National Renewable Energy Laboratory1617 Cole Boulevard, Golden, Colorado 80401-3393 303-275-3000 Operated for the Department of Energy Office of Energy Efficiency and Renewable Energy by Midwest Research Institute Battelle Contract No.

2 DE-AC36-99-GO10337 Technical Report NREL/TP-581-43156 Revised May 2008 Users Manual for TMY3 Data Sets S. Wilcox and W. Marion Prepared under Task No. NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights.

3 Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Available electronically at Available for a processing fee to Department of Energy and its contractors, in paper, from: Department of Energy Office of Scientific and Technical Information Box 62 Oak Ridge, TN 37831-0062 phone: fax: email: Available for sale to the public, in paper, from: Department of Commerce National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 phone: fax: email: online ordering.

4 Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste ERRATA SHEET NREL REPORT/PROJECT NUMBER: TP-581-43156 TITLE: Users Manual for TMY3 Data Sets AUTHORS: S. Wilcox and W. Marion ORIGINAL PUBLICATION DATE: April 2008 DATE OF CORRECTIONS: May 2008 The following corrections were made to this report: Pages 4-5: table 1-3, Lines 6, 9, 12, 15, 18, 21, 24 text changes Page 8: table 1-4 replaced Preface This user's Manual describes typical meteorological year (TMY) data sets derived from the 1991-2005 National Solar Radiation Data Base (NSRDB) update.

5 These data sets provide greater geographical coverage than previous TMY sets with 1020 locations in the United States and its territories. To distinguish between the old and new data sets, the new TMY data sets are referred to as TMY3. The TMY, TMY2, and TMY3 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 previous TMY data will not work with TMY3 data. The National Renewable Energy Laboratory (NREL) provides a software utility that allows reformatting of the TMY3 data to the TMY2 format.

6 The TMY data sets hold 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 TMY3 data sets and this Manual were produced by NREL's Electric and Systems Center under the Solar Resource Characterization Project, which is funded and monitored by the Department of Energy's Energy Efficiency and Renewable Energy Office.

7 Acknowledgements The meteorological data used in this data set are provided by the National Climatic Data Center (NCDC) from its Integrated Surface Database (ISD). NREL gratefully acknowledges the countless hours of time and expertise that went into the creation and maintenance of the ISD. More information on the ISD and NCDC is available at We also acknowledge the valuable contributions of the Atmospheric Sciences Research Center (ASRC), State University of New York at Albany. The ASRC team provided much of the modeled solar radiation data in this data set using the SUNY satellite model.

8 IiiTable of Contents iii iii List of List of v 1 Description of the TMY3 Data 1 1 Acquiring TMY3 1 Source Data for the TMY3 Data 1 TMY3 Data 3 TMY3 Site 9 2 Procedures for Developing 11 Sandia 11 Weighting and Index Modifications for TMY2 and 13 Changes from TMY2 to 14 El Chich n and Mount Pinatubo 14 Leap 14 Month Interface 15 Allowance for Missing 15 TMY3 Process Development and Quality 15 Calculation of Illuminance 19 Assignment of Source and Uncertainty 19 3 21 Appendix A TMY3 23 List of Figures Figure 2-1.

9 Cumulative distribution functions for June global horizontal solar radiation for Boulder, Colorado (example from TMY2 processing).. 12 Figure 2-2. Direct normal delta mean (new minus original 1961 1990) for each evaluation 16 Figure 2-3. Year selection frequency comparison between original 1961 1990 and re-created 1961 1990 17 Figure 2-4. Year selection frequency for 30-year 1976 2005 18 Figure 2-5. Year selection frequency for 15-year 1991 2005 19 ivList of Tables table 1-1. TMY3 data header (line 1).. 3 table 1-2. TMY3 data header (line 2).. 3 table 1-3. TMY3 data fields (lines 3-8762).

10 4 table 1-4. Solar radiation and illuminance source 8 table 1-5. Meteorological source 8 table 1-6. Meteorological uncertainty 8 table 2-1. Weighting values for FS 13 table 2-2. Bias (test data minus original 61-90 TMY).. 17 table 2-3. Standard 17 Acronyms ASHRAE American Society of Heating, Refrigerating, and Air-Conditioning Engineers TMY typical meteorological year NREL National Renewable Energy Laboratory NSRDB National Solar Radiation Data Base CSV comma separated value CDF cumulative distribution functions FS Finkelstein- Schafer WS weighted sum v 1 Description of the TMY3 Data Set This Manual describes how to obtain and interpret the data in the Typical Meteorological Year, version 3 (TMY3) data sets.