Frank Reekers wrote: > I think, that's not a back-of-the-envelope calculation, it is more a > good way to verify things and not believe everything... > But, back to my problem: Yes, you are right. PVGIS values are real-sky > values => http://re.jrc.ec.europa.eu/pvgis/solres/solrespvgis.htm.
> So, if I build the ratio of real-sky to clear-sky (PVGIS/r.sun) I get > for february 0.5628, that means ~56% of the solar radiation doesn't > reach the earth, right? > Let's do the same calculation for a summer day. If I take mid of july > (day=196) using r.sun (with lin=4.4) I get a global radiation of 7651 > KWh/m² per day, PVGIS shows an average value of 4730 KWh/m² per day for > july. The ratio for july (PVGIS/r.sun) is 0.6182....hmm, in summer more > radiation losses in percent as in winter, could this be right? Why not? ( calcs are done for Germany, ever-cloudy summer-sky, etc. right? just kidding... :-p ) Nikos [...] _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
