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Chapter 7: How accurate do the data need to be?

Chapter 8

How will we meet our solar radiation data needs?

One of the goals of the Solar Radiation Resource Assessment Project at NREL is to provide accurate information about solar radiation to minimize the economic risk of implementing solar energy conversion technologies. The data must accurately represent the spatial (geographic), temporal (hourly, daily, and seasonal), and spectral (wavelength distribution) variability of the solar radiation resource at different locations.

The new National Solar Radiation Data Base (1961-1990) for the United States will improve data quality over the existing SOLMET/ERSATZ (1952-1975) data base. For this new data base, NOAA used better equipment for measuring solar radiation at more sites and NREL used better modeling techniques for synthetic stations. Scheduled for completion in 1992, this new data base will include data for 250 sites. [Completed in 1993, the data base actually includes data for 239 sites.] After completing the data base we will produce special-purpose products such as typical meteorological year (TMY) data sets, maps, and data summaries. [All of these products except for the maps are currently available. In 1996, the maps will also be available.]

By continuing the long-term measurement of solar radiation at numerous sites, we can assess changes in climate and add new data to existing data bases. We can improve the quality of the solar radiation data base for the United States by working with existing regional solar radiation networks and establishing educational initiatives so that data are being collected at several hundred sites in the United States. This large number of measurement sites will improve the quality of the solar radiation data base, better represent the geographic distribution of solar radiation in the United States, and provide research data to develop techniques to estimate solar radiation where there are no measurement stations.

This type of research involves developing spatial interpolation techniques, such as mapping solar radiation using cloud-cover information from satellites, to estimate solar radiation between measurement stations. This cloud-cover mapping technique promises high spatial resolution for the optimum siting of solar energy conversion technologies and enables estimating of solar radiation for countries where no solar radiation data base exists.

NREL is improving the equipment and techniques used to measure solar radiation and the models and methods used to determine the performance of solar conversion technologies. Our recent activities include:

For information about solar radiation data, models, and assessments, contact the NREL Technical Inquiry Service at (303) 231-7303.

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