Siping

Hi, thanks for your replay You mean BkVFLss * GCR = BkVFLss_refers_to_ground? I checked these variables relationship: GlobBak = ReflBck + DifSBak - BackShd （assume BeamBak = 0） But what is relationship among ReflBck, BkVFLss_refers_to_ground, ReflLss, GlobGnd?

This is what GlobGnd and GkVFLss described in PVsyst help GlobGnd Global incident on ground, below the system. ReflLss Ground reflection loss (albedo) BkVFLss Loss due to the view Factor for rear side So I think GlobGnd is source energy for other parameters such as ReflLss and DiffGnd etc. That means value of GlobGnd should be the largest during these parameters. But I processd some simulation and looked into details of results. I found that BkVFLss always larger than GlobGnd. Does anyone know why about this? GlobGnd DiffGnd ReflLss BkVFLss kWh/m² kWh/m² kWh/m² kWh/m² January 26.1 9.94 13.06 18.8 February 41.5 13.76 20.73 35.4 March 70.9 23.17 35.45 67.1 April 98.7 27.04 49.34 96 May 125 28.2 62.51 121.1 June 124 29.7 62 119 July 122.1 32.43 61.07 117.3 August 103.1 31.35 51.56 99.9 September 75.3 24.16 37.64 72.3 October 52.8 18.7 26.41 47.2 November 30.3 12.88 15.13 23.6 December 20 10.03 10 14.4 Year 889.8 261.35 444.88 832.2 albedo=0.5 GlobGnd=889.8 BkVFLss=832.2 GlobGnd DiffGnd ReflLss BkVFLss kWh/m² kWh/m² kWh/m² kWh/m² January 26.1 9.94 5.22 30 February 41.5 13.76 8.29 56.7 March 70.9 23.17 14.18 107.4 April 98.7 27.04 19.74 153.6 May 125 28.2 25 193.8 June 124 29.7 24.8 190.4 July 122.1 32.43 24.43 187.7 August 103.1 31.35 20.62 159.9 September 75.3 24.16 15.06 115.7 October 52.8 18.7 10.56 75.5 November 30.3 12.88 6.05 37.7 December 20 10.03 4 23 Year 889.8 261.35 177.95 1331.5 albedo=0.8 BkVFLss=1331.5