PDF Publication Title:
Text from PDF Page: 005
2.4 Clear Sky Algorithms All of the solar radiation models evaluated here employ a clear-sky algorithm that attempts to produce an irradiance that can subsequently be modified with cloud cover. The validity of the clear sky component figures prominently because many applications seek to find the greatest solar resource, which typically only occurs under the clearest skies. Because cloud modifiers can be applied to any clear sky value, improvements in the clear sky algorithm would improve the overall model performance. To evaluate the global clear sky performance of the models, we produced special data sets from each model where the cloud input values were set to zero sky cover. These clear- sky values were compared with the recently developed REST2 model (7) and a data set with identified clear sky measurements. Although the REST2 model showed significant improvements over other clear-sky algorithms during its development using data from Bondville, results for the NSRDB evaluation showed that all models, including REST2, produced up to ±20 Wm-2 Root Mean Square errors (RMSE), and depending on the site, about ±10 Wm-2 Mean Bias Errors (MBE). These results may be an effect of using long-term averages for some model input data (in particular, aerosols and precipitable water) that do not match actual conditions for the measured data, or the variability may simply be within the measurement uncertainty limits. Additional work will be required to better understand the comparisons. 2.5 METSTAT Model The changeover to automated stations by the NWS eliminated the human observed total and opaque sky cover amounts used for inputs to the METSTAT model (8), which was used for the 1961-1990 NSRDB. To adapt the model to currently available data sets, we derived equivalent sky cover inputs (total and opaque cloud cover) from a combination of ASOS and ASOS supplemental cloud measurements (the latter derived from GOES satellite data). ASOS detects clouds to 12,000 ft, while the ASOS supplemental cloud measurements provide sky cover estimates for heights above 12,000 ft for a 50 km x 50 km area centered upon the ASOS station. Combining the low cloud amounts determined from the ASOS data, and the middle and high cloud amounts determined from the ASOS supplemental data, produced an equivalent total cloud estimate. Applying opacity factors based on cloud types inferred from cloud height produced estimates of opaque cloud amounts (low clouds opacity factor = 1.00; middle clouds opacity factor = 0.93; and high clouds opacity factor = 0.44). While availability of ASOS data for the 33 test sites was 95% or greater for 1999 and 2000, the ASOS supplemental cloud data was only available for about 70% of the period, with no data available for Alaska. About 1% of the ASOS supplemental data was unusable due to file format errors. The original METSTAT included an algorithm to compensate for human perception of cloud amounts nearer the horizon being greater than actual. This feature was eliminated because of the strictly vertical view of the ASOS cloud detector. 2.6 Improved Aerosol, Water Vapor and Ozone estimates The 1961-1990 NSRDB used only DNI measurements to estimate broadband Aerosol Optical Depth (BAOD). Today there is much less measured DNI data available, but much more aerosol data from other sources, including sun photometers and satellite-based estimates. These sources produce data that are spectral rather than broadband. A combination of surface sun photometry, satellite data from the NASA MISR project, and legacy DNI estimates of BAOD allowed creation of monthly mean estimates of BAOD for all locations in the U. S. Spectral AOD data are converted into BAOD using estimated Alpha parameters from sun photometry. All BAOD is adjusted to local elevation, utilizing an exponential function (9). These monthly values were smoothly fit to daily values using a mean-preserving interpolation method (10). For water vapor, NREL used the NASA Water Vapor Project (NVAP) dataset for daily estimates of water vapor on a 1o x 1° grid. NVAP integrates sounding data with satellite measurements of atmospheric water vapor. For the years 1983–1999, NVAP provides once daily estimates of water vapor on a 1o x 1o worldwide grid. For years 2000 and beyond, NVAP provides the data on a 0.5o x 0.5o grid twice daily. These data were interpolated in space to the location of each of the 33 NSRDB test stations and interpolated in time to provide hourly data for all stations for the years 1999 and 2000. For total column ozone, daily satellite observations from the Total Ozone Mapping Scanner (TOMS) are available once per day on a grid with spatial resolution of 1o in latitude and 1.25o in longitude. The missing data are replaced with long- term mean values from that location. 2.7 Data Filling Methods Serially complete data was a primary goal of the 1961–1990 NSRDB. However, maintaining this restriction for the 1991–2000 update may not be practical given the changes in the NWS network during the switchover to ASOS. The intersection of all qualifying stations for four rather than three decades would result in an even smaller roster of sites. 3PDF Image | Progress on an Updated National Solar Radiation Data Base for the United States
PDF Search Title:
Progress on an Updated National Solar Radiation Data Base for the United StatesOriginal File Name Searched:
37956.pdfDIY PDF Search: Google It | Yahoo | Bing
NFT (Non Fungible Token): Buy our tech, design, development or system NFT and become part of our tech NFT network... More Info
IT XR Project Redstone NFT Available for Sale: NFT for high tech turbine design with one part 3D printed counter-rotating energy turbine. Be part of the future with this NFT. Can be bought and sold but only one design NFT exists. Royalties go to the developer (Infinity) to keep enhancing design and applications... More Info
Infinity Turbine IT XR Project Redstone Design: NFT for sale... NFT for high tech turbine design with one part 3D printed counter-rotating energy turbine. Includes all rights to this turbine design, including license for Fluid Handling Block I and II for the turbine assembly and housing. The NFT includes the blueprints (cad/cam), revenue streams, and all future development of the IT XR Project Redstone... More Info
Infinity Turbine ROT Radial Outflow Turbine 24 Design and Worldwide Rights: NFT for sale... NFT for the ROT 24 energy turbine. Be part of the future with this NFT. This design can be bought and sold but only one design NFT exists. You may manufacture the unit, or get the revenues from its sale from Infinity Turbine. Royalties go to the developer (Infinity) to keep enhancing design and applications... More Info
Infinity Supercritical CO2 10 Liter Extractor Design and Worldwide Rights: The Infinity Supercritical 10L CO2 extractor is for botanical oil extraction, which is rich in terpenes and can produce shelf ready full spectrum oil. With over 5 years of development, this industry leader mature extractor machine has been sold since 2015 and is part of many profitable businesses. The process can also be used for electrowinning, e-waste recycling, and lithium battery recycling, gold mining electronic wastes, precious metals. CO2 can also be used in a reverse fuel cell with nafion to make a gas-to-liquids fuel, such as methanol, ethanol and butanol or ethylene. Supercritical CO2 has also been used for treating nafion to make it more effective catalyst. This NFT is for the purchase of worldwide rights which includes the design. More Info
NFT (Non Fungible Token): Buy our tech, design, development or system NFT and become part of our tech NFT network... More Info
Infinity Turbine Products: Special for this month, any plans are $10,000 for complete Cad/Cam blueprints. License is for one build. Try before you buy a production license. May pay by Bitcoin or other Crypto. Products Page... More Info
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)