December 8, 2015 Webinar Q&A
See below for questions and answers from our December 8 webinar.
Q: Will these slides be available after the webinar?
A: Yes. The slides are available at https://nsrdb.nrel.gov/links.
Q: Will there be anything published regarding the uncertainty of this data set?
A: Yes: please go to http://nsrdb.nrel.gov/publications and search for recent publications. One of the publications is:
Sengupta, M.; Weekley, A.; Habte, A.; Lopez, A.; Molling, C.; Heidinger, A. (2015). "Validation of the National Solar Radiation Database (NSRDB) (2005‒2012): Preprint." 6 pp. NREL/CP-5D00-64981.
Q: Have you done a side-by-side comparison of the accuracy of the empirical and physics-based models compared with the SURFRAD data?
A: No, we have not.
Q: The new database, does it have data for India?
A: There is an ongoing project under the India-US Energy Dialogue. This project is separate from the NSRDB project, but the India data will be accessible through the same NSRDB viewer. Please check back by the end of January 2016 to get the India data.
Q: Where do you download TMY data sets for the PSM?
Q: Will you be touching upon data that is present outside of the U.S.?
A: Yes, the current extent includes the U.S., the southern part of Canada, and South America. However, only 2005-2012 data is freely available for countries outside of the U.S. Please contact us for 1998-2014 data for these countries. Note: the validation of the current NSRDB data was done using the U.S. ground stations since there are very limited good-quality ground stations outside of the U.S.
List of Countries: Anguilla, Antigua and Barbuda, Aruba, Bahamas, Barbados, Belize, Bermuda, Bolivia, Brazil, British Virgin Islands, Canada, Cape Verde, Cayman Island, Chile, Colombia, Costa Rica, Cuba, Curaçao, Dominica, Dominican Republic, Ecuador, El Salvador, Grenada, Guatemala, Guyana, Haiti, Honduras, Jamaica, Kiribati, Mexico, Montserrat, Nicaragua, Panama, Paraguay, Peru, Puerto Rico, Saint Barthélemy, Saint Lucia, Sint Maarten, St Vincent and the Grenadines, St-Martin, St. Kitts and Nevis, St. Pierre and Miquelon, Suriname, Trinidad and Tobago, Turks and Caicos Islands, U.S. Minor Outlying Islands, U.S. Virgin Islands, and Venezuela
Q: Are there similar limits to data downloads using the API?
A: Yes, there is a limit to downloading data through API. That is 50 pixels an hour and 100 pixels a day, and these limits are mainly because of hardware limitation. We expect to increase some of these limits in the near future, but there will always be a limit.
Q: If I want to do solar grid integration studies with time-series NREL data, what kind of data set should I consider? GHI?
A: The NSRDB data is in the SAM CSV format, which is suitable for solar power data conversion using SAM. The data format includes DNI and DHI, and also some meteorological parameters, which are helpful for solar power data conversion and solar grid integration studies.
Q: In addition to the TMY data sets, will there be "TGY and TDY," i.e., typical GHI and typical DNI year sets similar to NREL's Solar Prospector?
A: We did a comparison between TMY, TGY, and TDY, and the publication is freely available (http://www.nrel.gov/docs/fy14osti/60886.pdf). The results in the publication show that TMY, TGY, and TDY are not significantly different. Therefore, while this is one of the things we have on our list, we are not currently treating this as a priority unless we hear specifically from our users about this need.
Q: Will more recent (closer to real-time) data ever be available in the NSRDB?
A: Our current DOE project does not emphasize the production of real-time data. However, we advise you to please communicate your needs and reasoning for such a data set to us, and we will send it to DOE for consideration.
Q: How does the met data in PSM compare with that in MTS2, for specific years and TMYs?
A: The meteorological data for the PSM comes from the NASA Modern Era-Retrospective Analysis (MERRA) model; however, the MTS has measured data from the Integrated Surface Database (ISD).
We conducted a comparison between various modeled meteorological data sources relative to the ISD, and the MERRA data compares relatively better than the other modeled metrological dataset. That is why we implemented MERRA as a meteorological data source. A publication is being worked on, but if you need a specific comparison, please contact us.
Q: Is it possible to search by Lat/Long?
A: Yes – in the top righthand corner of the NSRDB Viewer, there is a “Zoom to Location” button. Press the button and you will be able to search by latitude and longitude or by address, county and more.
Q: Does the current relative humidity error affect the radiative transfer modeling results?
A: No, it doesn’t, because the current radiative transfer model requires the water vapor path, which was calculated accurately. The relative humidity is a surface meteorological variable, and it is calculated using the specific humidity. We currently have a minor error in the calculation when converting specific humidity to relative humidity, which will be corrected in the near future.
Q: Will this NSRDB continue to build through the end of the current GOES-N/O/P series, and have a logical breakpoint when the new GOES-R series begins (with improved spatial/spectral/radiometric quality and presumably improved products)?
A: It is our plan to have a 5-minute 2-km dataset in the GOES-R Era. However, again this depends on DOE priority and funding, and that is determined significantly by feedback DOE gets from industry about their needs.
Q: How about posting the entire dataset on AMAZON EBS snapshot, so it won't use your server?
A: Yes, we are exploring this, but we need to find a mechanism to pay for this. So any new ideas are welcome.
Q: Is there a plan to release a GIS data set for annual date?
A: Yes, check back to the NSRDB viewer in January 2016 for these data sets.
Q: How do we provide DOE feedback?
A: Please send your feedback through the NSRDB website contact link or support forum for now, and we will communicate it to DOE. We are exploring the best way to convey feedback directly and will post this information when available.
Q: Do the validation publications include comparison with the previous SUNY model that NSRDB utilized?