Irradiance Transposition and Reflections in BIPV Installations

Data sets of three European vertical PV installations with CIGS modules and irradiance sensors in all 11 module planes were studied and rated. Horizontal irradiance data was therefore converted into the module planes using most available irradiance transposition and decomposition models of the pvlib library with default parameters. With the filtering and adjustment methods shown, the Perez transposition with DISC decomposition demonstrated the best performance over the respective time periods, also for the North facing directions. One of the PV systems is situated on top of a river bench similar to a vineyard. For this site, increased irradiances by light reflection off the water surface with a total of more than one sun were recorded over longer time periods. These reflections increased the electrical yield by a similar amount by about 20% short term, and approximately 1.5% for the whole year.