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| Resource Applications Division >> |
May, 2007 |
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Contents
Resource Applications Division Annual Meeting Invitation and AgendaPlease Plan to Attend the Resource Applications Division Annual MeetingTuesday, July 10, 12:30 – 1:30Cleveland, Ohio
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 May/June 2007 FeaturesBreaking the Oil AddictionAddressing the Oil Crisis in the U.S. Renewable Hydrogen: Solar Water-Heating Resurgence Ahead? |
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Letter from the ChairKnowledge as PowerThe field of measurement, modeling, and reporting of renewable energy resources is changing and taking on new meaning for a new generation of solar professionals. In the past, assessment of the solar resource was the sole province of physicists and meteorologists. Translation of terrestrially incident irradiance into energy contributions to utility electrical demand was sometimes extrapolated to a continental scale based upon knowledge of the cell physics of pre-commercial photovoltaic products whose principle use had previously been relegated to powering satellites. Today the science that has led us here is being retooled to provide increasingly more commercial, operational and site-specific applications. In recent years, for large solar electric installations, there has been a trend away from system ownership by the end user toward projects structured as build/own/operate fee for service contracts. These are long-term energy contracts where the investor owns and operates the system, and their revenue derives solely from the energy it produces. Based on this kind of business model, ground was recently broken on a 15 MW photovoltaic installation at Nellis Air Force Base outside of Las Vegas. More than ever before the commercial decision to invest and build at a particular site hinges, among other things, on the best solar resource science that is available. Similarly, in daily operation central station solar plants, the short term assessment of the resource is critical to operations, and thus the bottom line. For concentrating solar power systems, be they trough plants or individual tracking heliostats, knowledge of the direct normal component of the solar resource is essential. Both satellite and ground based assessment technologies are being used to enhance the productivity and cost competitiveness of these generation sources. In addition to use in large commercial applications, resource assessment continues to play an invaluable role in education. Whether in the form of consolidated statistics for the science teacher or web-based reporting on individual system production –on a home or on the statehouse-- the information produced and delivered by the assessment community provides a tangible link for the public between their daily experience of the resource --sun, wind, tides— and the energy use that so many of us take for granted. Today that educational role extends beyond the purely pedagogical to the function of informing government policy. As more and more politicians awaken to an awareness of the long-term societal liability of nuclear and fossil fuel dependence, the assessment community is there to illuminate the renewable energy resources located in their cities, counties, states and nations. The native “assets” that are quantified through resource assessment represent commercial opportunities to local economies and job growth potential to their constituents. Eventually, if the goal of large-scale adoption of renewable energy becomes a reality, real-time integration of these variable energy resources with conventional electrical distribution systems will become a necessary component of grid management. Large-scale geographic resource databases, such as the National Solar Radiation Database (NSRDB), with their ever higher spatial resolution, will continue to be the fundamental tool in system site selection and the basis for long-term planning. But short-term forecasting of renewable resources –in the one to twenty four hour range-- could become a commercial service not unlike weather forecasting, integrated into the daily and hourly dispatch of generation and the economics of energy markets. The resource assessment science of past decades has laid the foundation for the engineered solutions of today. The continued focus on both solar resource assessment science and engineering will facilitate the commercial realization of our renewable energy future. James Bing, PE NREL and NCDC Release the Updated 1991-2005 National Solar Radiation DatabaseBackground. Culminating a three-year project, the National Renewable Energy Laboratory (NREL) and the National Climatic Data Center (NCDC) have released an update to the United States National Solar Radiation Database (NSRDB). The update contains solar radiation (global, direct, and diffuse) and meteorological data for 1454 stations covering the years 1991-2005. The original NSRDB covered the years 1961-1990 and contained solar and meteorological data for 239 stations in the United States and its territories. In addition to the conventional NSRDB ground stations, the update includes a one-tenth degree gridded data set produced by the Atmospheric Sciences Research Center at the State University of New York at Albany using images from the East and West Geostationary Operational Environmental Satellites (GOES). This hourly data set contains global, direct, and diffuse solar records for eight years (1998-2005) for the United States (excluding Alaska below 60˚) for about 100,000 pixel locations (a nominal 10-km pixel size). Project Participants. Primary project funding came from NREL with support from the following collaborators: The Atmospheric Sciences Research Center, State University of New York at Albany; Climate Systems Branch, National Aeronautics and Space Administration; National Climatic Data Center, U.S. Department of Commerce; Northeast Regional Climate Center, Cornell University; Solar Consulting Services, Colebrook, New Hampshire; and the Solar Radiation Monitoring Laboratory, University of Oregon. Station Classification. The original NSRDB was serially complete for daylight hours for the entire 30-year period of record. To increase the quantity of data available, the updated NSRDB did not mandate serial completeness. Rather, all possible gaps in a station’s record were filled, and then the stations were segregated according to data quality and completeness. Class I stations have a complete hourly data set for the 1991-2005 period and were produced using the best available input data for the models. Class II stations also have a complete hourly period of record, but have a higher uncertainty due to lower quality input data. Class III stations contain gaps in the period of record, but have at least three years of data that may be useful for some applications. Among the 1454 stations, 221 qualify as Class I, 637 as Class II, and 596 as Class III. Figure 1 shows the geographical coverage of the NSRDB ground stations, overlaid with the 1961-1990 NSRDB stations. Measured Data. Forty stations in the updated NSRDB include measured solar data, supplied by these agencies: Atmospheric Radiation Measurement (ARM) Program, DOE; Florida Solar Energy Center, State of Florida; Integrated Surface Irradiance Study (ISIS) and Surface Radiation Budget Measurement (SURFRAD) Networks, NOAA/ARL, NOAA/ESRL/Global Monitoring Division; Measurement and Instrumentation Data Center, NREL; University of Oregon Solar Radiation Monitoring Laboratory Network; and University of Texas Solar Energy Laboratory. One significant difference between the 1961–1990 NSRDB and the 1991–2005 update is how the measured data are stored in data records. In the original NSRDB, the measured data were merged with the modeled data such that a seamless data set of solar radiation values was produced (the model essentially filled gaps in the measured data). In the update, we opted to include fields for both measured and modeled data, allowing the user the flexibility of choosing either modeled or (if available) measured data for an application.
Data Access. Because of immense changes in data distribution technologies since the release of the original NSRDB, the updated NSRDB is distributed via the internet rather than a physical medium. Several options are available for data access. NCDC distributes a conventional NSRDB data set that includes modeled and measured (where available) solar data and key meteorological observations. They also distribute a solar-only data set at no cost and will include the solar data in their Integrated Surface Dataset infrastructure (without any filled meteorological data). NREL distributes a superset of the solar data without any meteorological fields. This solar research data set includes all modeled data, special clear-sky data fields (modeled with cloud cover set to zero), and other associated atmospheric components. Users interested in the NSRDB should start with the NSRDB User’s Manual, available for download here: http://www.nrel.gov/docs/fy07osti/41364.pdf (PDF 14 MB). This document provides a description of the data and how the database was developed. The manual includes a complete list of stations along with a data quality summary for each site, an example of which is shown in Figure 2. This summary shows the relative data availability and uncertainties for a station’s period of record.
The table below details data access options.
The table below details costs for the fee-based distributions from NCDC noted in the previous table.
For more information, contact Steve Wilcox: Stephen_Wilcox@nrel.gov or 303-384-7785. |
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Copyright © 2007 American Solar Energy Society • 2400 Central Ave., Ste. A, Boulder, CO 80301 P: 303.443.3130 • F: 303.443.3212 • ases@ases.org • www.ases.org |
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