Back Irradiance Measurements and Influence of the Ground Coverage on the Production of a Bifacial Agrivoltaics System

Agrivoltaics systems have been gaining increased attention as PV is deployed massively, due to the dual use of the available land. Bifacial modules can increase the energy output of Agrivoltaics systems but the effect of the back irradiance cannot be straightforwardly evaluated. The Agrivoltaics system is located in Lisbon, Portugal, at the solar campus of the Faculty of Sciences of the University of Lisbon. It consists of 12 mono facial modules from LONGI (LR4-60HPH 350) rated at 350 Wp each and 6 bifacial modules LONGI (LG440N2T-E6) rated at 440 W for the front surface or 470 W for an additional 100W/m2 back irradiance. This work presents in-situ measurements of the albedo's impact on the power output of a bifacial agrivoltaics system, for different ground conditions and along the day. A method to measure the back irradiance with spatial resolution, without any assumptions on simulation models is presented. It is shown how the back irradiance spatial distribution along the different parts of the PV system change along the day, as the sun moves.