Maybe the problem is due to a Linke turbidity coeffcient too low
(atmosphere too transparent)...
Frank Reekers escribió:
the global radiation, calculated with r.sun, seems to be very high in
comparison to PVGIS (Photovoltaic Geographical Information System).
- r.sun for 14. Feb: ~2363 Wh/m² per day
- PVGIS: 1330 Wh/m² per day Irradiation on horizontal plane for
february on average
Below the detailed steps I did in GRASS and with PVGIS:
1. PVGIS:
a) http://re.jrc.ec.europa.eu/pvgis/apps3/pvest.php -> search for
location 'Osnabrueck, Germany' -> choose monthly radiation -> click
calculate -> the output table shows 1330 Wh/m² Irradiation on
horizontal plane for february.
2. GRASS
a) Take an existing DEM with the resolution of 1m and set all z-values
to 68m to have a completely horizontal plane:
GRASS 6.4.0RC6 (GRASS)> r.mapcalc dsxx94c68=dsxx...@permanent*0+68.00
b) Set Region
GRASS 6.4.0RC6 (GRASS)> g.region rast=dsxx94c68
c) Create slope & aspect:
GRASS 6.4.0RC6 (GRASS)> r.slope.aspect elevation=dsxx94...@permanent
slope=sdsxx94c68 aspect=adsxx94c68 --overwrite
d) Run r.sun for day 45:
GRASS 6.4.0RC6 (GRASS)> r.sun elevin=dsxx94...@permanent
aspin=adsxx94...@permanent slopein=sdsxx94...@permanent
glob_rad=g45phxx94c68 day=45 --overwrite
e) Get global radiation:
GRASS 6.4.0RC6 (GRASS)> r.what input=g45phxx94c68
east_north=3435430.596,5794315.99
3435430.596|5794315.99||2362.9213867188
Is there a reasonable explanation for this or did I something wrong?
Thanks for your help
Frank
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--
Alberto Pettazzi
MeteoGalicia - Departamento de Climatología y Observación
Consellería de Medio Ambiente, Territorio e Infraestruturas
Rúa de Roma, 6
15707 Santiago de Compostela. A Coruña
Teléfono: +34-881-999646
e-mail: [email protected]
<mailto:[email protected]>
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