Solar Radiation Data Manual for Buildings

Table of Contents

Introduction

Technical Background

The solar radiation and illuminance data in this manual were modeled using data from the National Solar Radiation Data Base (NSRDB) Version 1.1, which was completed in March 1994 by the National Renewable Energy Laboratory (NREL). The NSRDB contains hourly values of measured or modeled solar radiation and meteorological data for 239 stations for the 30-year period from 1961-1990. A complete description of the NSRDB and how it was produced is presented in its user's manual (NSRDB-Vol.1 1992) and the final technical report (NSRDB-Vol. 2 1995). The original version of the NSRDB, Version 1.0, was completed in August 1992. Version 1.1 corrects two types of minor errors in Version 1.0 that affected about 10% of the stations (Rymes 1994).

There are two types of stations in the NSRDB: primary (denoted by asterisks in the station map) and secondary (denoted by dots in the station map). Primary stations, of which there are 56, measured solar radiation for a part (from 1 to 27 years) of the 30-year period. The remaining 183 stations, designated secondary stations, made no solar radiation measurements. Their data are modeled solar radiation values derived from meteorological data such as cloud cover. Both primary and secondary stations are National Weather Service stations that collected meteorological data for the period 1961-1990.

Succeeding the older 1952-1975 SOLMET/ERSATZ data base, the NSRDB accounts for any recent climate changes and provide more accurate values of solar radiation. The NSRDB data are more accurate for several reasons:

  • More measured data

  • Better model for estimating values (More than 90% of the solar radiation data in both data bases are modeled.)

  • Improved instrument calibration methods

  • Rigorous procedures for assessing quality of data.

    Results of a comparison of the NSRDB with the SOLMET/ERSATZ data base provide the incentive to develop new solar radiation resource products, such as this data manual. On an annual basis, 40% of the NSRDB and SOLMET/ERSATZ station values are in disagreement for global horizontal radiation by more than 5%; some station values show disagreement of up to 18% (Marion and Myers 1992). For direct beam radiation, 60% of the NSRDB and SOLMET/ERSATZ station values are in disagreement by more than 5%; some stations show disagreement of up to 33%. Disagreement is attributed to differences in the instruments' calibration procedures and models.

    This manual presents solar radiation and illuminance values to enable quick estimates of the incident solar energy for common window orientations. The solar radiation and illuminance values were computed using models and NSRDB hourly values of direct beam, global horizontal, and diffuse horizontal solar radiation, and dew point temperature. Climatic data were obtained from the NSRDB and from climatic data sets provided by the National Climatic Data Center, Asheville, North Carolina. The Appendix describes in more detail how this manual was produced.

    References

    Marion, W.; Myers,D.(1992). A Comparison of Data from SOLMET/ERSATZ and the National Solar Radiation Data Base. NREL/TP-463-5118, Golden, CO: National Renewable Energy Laboratory.

    NSRDB-Vol.1 (1992). User's Manual-National Solar Radiation Data Base (1961-1990). Version 1.0. Golden, CO: National Renewable Energy Laboratory and Asheville, NC: National Climatic Data Center.

    NSRDB-Vol.2 (1995). FInal Technical Report: National Solar Radiation Data Base (1961-1990). NREL/TP-463-5784, Golden, CO: National Renewable Energy Laboratory.

    Rymes,M. (1994). "Beyond the NSRDB Version 1.0." Proceedings of the 1994 Annual American Solar Energy Society Conference; June 25-30, 1994, San Jose, CA.

    Interpreting the Data Tables

    Table of Contents

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