Title:	Validation of the National Solar Radiation Database (NSRDB) (2005-2012)
Author(s):	M. Sengupta, A. Weekley, A. Habte, A. Lopez, C. Molling, A. Heidinger
Topic:	OPERATIONS, PERFORMANCE AND RELIABILITY OF PHOTOVOLTAICS (FROM CELLS TO SYSTEMS)
Subtopic:	Operation of PV Systems and Plants
Event:	31st European Photovoltaic Solar Energy Conference and Exhibition
Session:	5CO.5.4
Pages:	1710 - 1716
ISBN:	3-936338-39-6
Paper DOI:	10.4229/EUPVSEC20152015-5CO.5.4
Price:	0,00 EUR
Document(s):	paper

Abstract/Summary:

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Publicly accessible, high-quality, long-term, satellite-based solar resource data is foundational and critical to solar technologies to quantify system output predictions and deploy solar energy technologies in grid-tied systems. Solar radiation models have been in development for more than three decades. For many years, the National Renewable Energy Laboratory (NREL) developed and/or updated such models through the National Solar Radiation Data Base (NSRDB). There are two widely used approaches to derive solar resource data from models: (a) an empirical approach that relates ground-based observations to satellite measurements and (b) a physics-based approach that considers the radiation received at the satellite and creates retrievals to estimate clouds and surface radiation. Although empirical methods have been traditionally used for computing surface radiation, the advent of faster computing has made operational physical models viable. The Physical Solar Model (PSM) developed by NREL in collaboration with the University of Wisconsin and the National Oceanic and Atmospheric Administration (NOAA) computes global horizontal irradiance (GHI) using the visible and infrared channel measurements from the Geostationary Operational Environmental Satellites (GOES) system. PSM uses a two-stage scheme that first retrieves cloud properties and then uses those properties to calculate surface radiation. The cloud properties in PSM are generated using the AVHRR Pathfinder Atmospheres-Extended (PATMOS-x) algorithms [5]. Using the cloud mask from PATMOS-x, and aerosol optical depth (AOD) and precipitable water vapor (PWV) from ancillary sources, the direct normal irradiance (DNI) and GHI are computed for clear-sky conditions using the MMAC model. For cloud scenes identified by the cloud mask, the Satellite Algorithm for Surface Radiation Budget (SASRAB) is used to compute the GHI. The DNI for cloud scenes is then computed using the DISC model [6]. The current NSRDB update has a 4-km x 4-km, 30-minute resolution covering 20052012. This paper evaluates the PSM-based NSRDB data set using ground-measured data and provides detailed evaluation statistics. The result of the comparison shows a good correlation between the NSRDB and ground data. Further, an outline of the next version of the NSRDB and future plans for enhancement and improvement are provided. This version is expected to be released in September 2015 and will contain data from 19982014.