3 tier spg 2013 ppt
TRANSCRIPT
Building a Better TMYGwendalyn Bender - PresentingAndrew Etringer, Steve Ihnen, Pascal StorckCo-authors
February 14, 2013
Setting the stage…
NREL TMY Methodology
TMY2: Ground data derived 1961-1990 (mixed irradiance and
meteorological observations)
With irradiance obs: Monthly cumulative distribution of daily
means for 5 variables using different weights (GHI (25%), DNI (25%),
temperature (20%), dew point (20%), and wind speed(10%))
With met data obs only: Irradiance is derived. Then monthly cumulative
distribution of daily means for 5 variables using different weights (GHI
(25%), DNI (25%), temperature (20%), dew point (20%), and wind
speed(10%))
TMY3: TMY2 database + Satellite data derived irradiance data 1991-
2005
Monthly cumulative distribution of daily means for 5 variables using different weights (GHI (25%), DNI
(25%), temperature (20%), dew point (20%), and wind speed(10%))
3TIER TMY Methodology
Satellite Derived Data (1997 –Current) for irradiance.
Choose irradiance value as main input (GHI, DNI or DIF).
4-day samples, within 0.5% deviation, for monthly means,
the monthly cumulative distribution of daily means, monthly diurnal cycles and
the annual mean.
NWP run (1997 – Current) for weather variables.
Temperature, wind speed, wind direction, surface
pressure, and relative humidity for matching time period
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
• NREL’s monthly sampling period vs 3TIER’s 4-day sampling period– Weighting for the different parameters also varies
• Coverage of the United States and India with NREL vsglobal 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
17km
103km
105km
Case Study – Southern CaliforniaMean (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 CaliforniaPrivate ObservationsNREL Site 1 TMY3TIER TMYNREL Site 2 TMYNREL Site 3 TMY
Monthly Means Comparison
W/m
2
Months
Case Study – Southern California
20
10
20
11
GHI DNI DIF
Case Study – Southern California
Annual Yield [GWh]
Ann Avg DNI [Wh/m2-day]
Ann Avg GHI [Wh/m2-day]
3TIER 14-year data set
33.778 6,441 5,784
3TIER TMY methodology
33.816 6,405 5,803
NREL TMY methodology
35.751 7,230 5,767
Case Study – Southern California
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 TMY’s suck
• Get a long-term timeseries
Questions?
Gwendalyn [email protected]