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3 tier spg 2013 ppt

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Gwendalyn Bender
Gwendalyn Bender

1) The 3TIER TMY methodology uses satellite-derived irradiance data from 1997 to present and numerical weather prediction model output for weather variables, selecting 4-day samples to develop typical meteorological years. 2) A case study in Southern California found that when compared to private observations over 2 years, the 3TIER TMY values more closely matched the observed data than the nearest NREL TMY sites. 3) While 3TIER TMY data provides a global dataset, its long-term variability is limited. For accurate system performance predictions, obtaining a long-term on-site weather dataset is preferable to using a TMY.

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Building a Better TMY Gwendalyn Bender - Presenting Andrew Etringer, Steve Ihnen, Pascal Storck Co-authors February 14, 2013
Setting the stage
NREL TMY Methodology TMY2: Ground data derived 1961- TMY3: TMY2 database + Satellite 1990 (mixed irradiance and data derived irradiance data 1991- meteorological observations) 2005 With met data obs only: Irradiance is With irradiance obs: Monthly derived. Then monthly cumulative Monthly cumulative distribution of cumulative distribution of daily distribution of daily means for 5 daily means for 5 variables using means for 5 variables using different variables using different weights (GHI different weights (GHI (25%), DNI weights (GHI (25%), DNI (25%), (25%), DNI (25%), temperature (25%), temperature (20%), dew point temperature (20%), dew point (20%), (20%), dew point (20%), and wind (20%), and wind speed(10%)) and wind speed(10%)) speed(10%))
3TIER TMY Methodology Satellite Derived Data (1997 NWP run (1997 Current) for Current) for irradiance. weather variables. 4-day samples, within 0.5% deviation, for monthly means, Temperature, wind speed, Choose irradiance value as the monthly cumulative wind direction, surface main input (GHI, DNI or DIF). distribution of daily means, pressure, and relative humidity monthly diurnal cycles and for matching time period the annual mean. 4-day samples for irradiance must also preserve temporal correlation for weather, within 1.0% deviation, for the same statistics.
TMY Dataset Differences Direct irradiance & weather observations for the TMY2 database vs derived irradiance & weather observations from 3TIER and the TMY3 database. The time periods covered vary. NREL dataset is static vs the 3TIER updated dataset NRELs monthly sampling period vs 3TIERs 4-day sampling period Weighting for the different parameters also varies Coverage of the United States and India with NREL vs global coverage with 3TIER so how do they compare?
Comparison Results
Comparison Results January July
Case Study Southern California Private observations with 2+ years of GHI observations 3TIER TMY pulled at the site Nearest 7 NREL sites were TMY3 locations Nearest TMY2 location ~130km away
Case Study Southern California 103km 105km 17km
Case Study Southern California Mean (W/m2) Private Site 3TIER NREL Site 1 NREL Site 2 NREL Site 3 Annual 251.27 241.77 240.36 224.8 225.67 Jan 146.5 143.36 148.58 146.13 144.78 Feb 189.39 177.64 172.86 179.86 177.08 Mar 256.41 247.41 239.89 207.06 189.7 Apr 303.45 299.56 300.18 287.36 277.55 May 338.6 330.97 327.19 291.53 324.74 Jun 341.12 345.68 340.27 292.08 300.2 Jul 315.86 315.12 316.14 294.94 298.1 Aug 288.34 288.03 296.96 263.87 273.7 Sept 266.12 258.11 254.19 254.31 250.93 Oct 205.99 206.2 191 208.39 209.66 Nov 162.28 155.43 155.53 164.17 153.5 Dec 124.26 130.21 137.58 106.48 105.68
Case Study Southern California Private Observations NREL Site 1 TMY Monthly Means Comparison 3TIER TMY NREL Site 2 TMY NREL Site 3 TMY W/m2 Months
Case Study Southern California GHI DNI DIF 2010 2011
Case Study Southern California
Case Study Southern California Annual Yield Ann Avg DNI Ann Avg GHI [GWh] [Wh/m2-day] [Wh/m2-day] 3TIER 14-year 33.778 6,441 5,784 data set 3TIER TMY 33.816 6,405 5,803 methodology NREL TMY 35.751 7,230 5,767 methodology
Long-term Variability is Important The TMY should not be used to predict weather for a particular period of time, nor is it an appropriate basis for evaluating real- time energy production or efficiencies for building design applications or solar conversion systems. NREL Technical Report 2008
Conclusions 3T TMY = pretty good, available any where for better site accuracy BUT TMYs suck Get a long-term timeseries
Questions? Gwendalyn Bender gbender@3tier.com

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3 tier spg 2013 ppt

  • 1. Building a Better TMY Gwendalyn Bender - Presenting Andrew Etringer, Steve Ihnen, Pascal Storck Co-authors February 14, 2013
  • 3. NREL TMY Methodology TMY2: Ground data derived 1961- TMY3: TMY2 database + Satellite 1990 (mixed irradiance and data derived irradiance data 1991- meteorological observations) 2005 With met data obs only: Irradiance is With irradiance obs: Monthly derived. Then monthly cumulative Monthly cumulative distribution of cumulative distribution of daily distribution of daily means for 5 daily means for 5 variables using means for 5 variables using different variables using different weights (GHI different weights (GHI (25%), DNI weights (GHI (25%), DNI (25%), (25%), DNI (25%), temperature (25%), temperature (20%), dew point temperature (20%), dew point (20%), (20%), dew point (20%), and wind (20%), and wind speed(10%)) and wind speed(10%)) speed(10%))
  • 4. 3TIER TMY Methodology Satellite Derived Data (1997 NWP run (1997 Current) for Current) for irradiance. weather variables. 4-day samples, within 0.5% deviation, for monthly means, Temperature, wind speed, Choose irradiance value as the monthly cumulative wind direction, surface main input (GHI, DNI or DIF). distribution of daily means, pressure, and relative humidity monthly diurnal cycles and for matching time period the annual mean. 4-day samples for irradiance must also preserve temporal correlation for weather, within 1.0% deviation, for the same statistics.
  • 5. TMY Dataset Differences Direct irradiance & weather observations for the TMY2 database vs derived irradiance & weather observations from 3TIER and the TMY3 database. The time periods covered vary. NREL dataset is static vs the 3TIER updated dataset NRELs monthly sampling period vs 3TIERs 4-day sampling period Weighting for the different parameters also varies Coverage of the United States and India with NREL vs global coverage with 3TIER so how do they compare?
  • 8. Case Study Southern California Private observations with 2+ years of GHI observations 3TIER TMY pulled at the site Nearest 7 NREL sites were TMY3 locations Nearest TMY2 location ~130km away
  • 9. Case Study Southern California 103km 105km 17km
  • 10. Case Study Southern California Mean (W/m2) Private Site 3TIER NREL Site 1 NREL Site 2 NREL Site 3 Annual 251.27 241.77 240.36 224.8 225.67 Jan 146.5 143.36 148.58 146.13 144.78 Feb 189.39 177.64 172.86 179.86 177.08 Mar 256.41 247.41 239.89 207.06 189.7 Apr 303.45 299.56 300.18 287.36 277.55 May 338.6 330.97 327.19 291.53 324.74 Jun 341.12 345.68 340.27 292.08 300.2 Jul 315.86 315.12 316.14 294.94 298.1 Aug 288.34 288.03 296.96 263.87 273.7 Sept 266.12 258.11 254.19 254.31 250.93 Oct 205.99 206.2 191 208.39 209.66 Nov 162.28 155.43 155.53 164.17 153.5 Dec 124.26 130.21 137.58 106.48 105.68
  • 11. Case Study Southern California Private Observations NREL Site 1 TMY Monthly Means Comparison 3TIER TMY NREL Site 2 TMY NREL Site 3 TMY W/m2 Months
  • 12. Case Study Southern California GHI DNI DIF 2010 2011
  • 13. Case Study Southern California
  • 14. Case Study Southern California Annual Yield Ann Avg DNI Ann Avg GHI [GWh] [Wh/m2-day] [Wh/m2-day] 3TIER 14-year 33.778 6,441 5,784 data set 3TIER TMY 33.816 6,405 5,803 methodology NREL TMY 35.751 7,230 5,767 methodology
  • 15. Long-term Variability is Important The TMY should not be used to predict weather for a particular period of time, nor is it an appropriate basis for evaluating real- time energy production or efficiencies for building design applications or solar conversion systems. NREL Technical Report 2008
  • 16. Conclusions 3T TMY = pretty good, available any where for better site accuracy BUT TMYs suck Get a long-term timeseries

Editor's Notes

  1. A hypothetical 20MW capacity array with losses and downrates characteristic of the US SW.