EFFECTIVE ACCURACY OF SATELLIT

GLOBAL, DIRECT AND DIFFUSE IRR

IN THE CENTRAL US

Richard Perez & Marek Kmiec

ASRC

Antoine Zelenka

MeteoSuisse

Ray George & David Renné

NREL

NREL/PR-550-40032Presented at the 2001 Solar Energy Forum: The Power to Choose held on April 21-25, 2001
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0

100200300400500600700800900

1000

0 200 400 600 

satellite-derived global irradiance (W/sq.m)

measured global irradianc

Satellite-derived global irradiance

Measured g

Short term Effective Accuracy Short term Effective Accuracytime/site specific data time/site specific data

Hourly RMS Error as a function of station distan

satellite becomes more accu

0%5%

10%15%20%25%30%35%40%45%50%

0 50 100 150 200 250 300

Northeastern USSwitzerland

satellite confidence level -- simple model

(accounting for time mismatch and solar geometry)

Relative RMSE (%)

Distance from station (km)

Nugget Effect

} 

A
NE-US / Switzerland Study

- Ground measurement 

networks not designed for research

- Hourly data only- Global irradiance only- Humid / temperate climates- Marked orographic features 0%

5%

10%15%20%25%30%35%40%45%50%

0 50 100 

satellite co

(accounting for 

Relative RMSE (%)

Nugget Effect
NE-US / Switzerland Study

- Ground measurement 

networks not designed for research

- Hourly data only- Global irradiance only- Humid / temperate climates- Marked orographic features 0%

5%

10%15%20%25%30%35%40%45%50%

0 50 100 

satellite co

(accounting for 

Relative RMSE (%)

Nugget Effect

SOUTHERN GREAT PLAINS STUDY- Ground measurement network designed for res

(ARM)

- One minute, hourly and daily data- Global, direct and diffuse irradiances- Continental climate - Limited orographic features
http://www.arm
ARM Extended Fa

• WMO class I glob• 19 out of 26 statio
0%

20%40%60%80%

100%

0 200 400

daily datahourly data1 min. data

 apparent satellite model accuracy

distance (km)

one-minute

hourly

daily

Daily breakeven distanHourly breakeven dist1-minute breakeven d
0%

20%40%

0 200

 apparent satellite model accuracy

distanc

one-min

hou

da

0%5%

10%15%20%25%30%35%40%45%50%

0 50 100 15

satellite confidenc

(accounting for time m

Relative RMSE (%)

Nugget Effect

Southern Great Plains

} Effe
0%

20%40%60%80%

100%

0 200 400

daily datahourly data1 min. data

distance (km)

 apparent satellite model accuracy

one-minute

hourly

daily

Daily breakeven distanHourly breakeven dist1-minute breakeven d
0%

20%40%60%80%

100%

0 200 400

daily datahourly data1 min. data

hourly satellite model accuracy

distance (km)

 apparent satellite model accuracy

one-minute

hourly

daily

Daily breakeven distanHourly breakeven dist1-minute breakeven d
0%

20%40%

0 200

 apparent satellite model accuracy

distanc

one-min

hou

da

} Effective accura

CONCLUDING REMARKS

Global effective accuracy Direct effective accuracy Diffuse effective accuracy 

Hourly

Confirmation / extension of initial inve
CONCLUDING REMARKS

Global effective accuracy Direct effective accuracy Diffuse effective accuracy 

Hourly

Confirmation / extension of initial inve

Need to expand study to arid and tropical/subtropical climates