What is the optimal configuration for integrating hyperaccumulating plants with photovoltaic systems to enhance plant development and energy production?

Industrial brownfield soils are often contaminated with trace metals, and these areas can be remediated by agromining, using hyperaccumulating plants that can accumulate metals in their aerial parts. However, this process is too slow to be profitable in the short term. The installation of photovoltaic (PV) modules could improve profitability during the bioremediation period. Thus, the objective of this study was to determine the optimal trade-off between electricity production and the development of hyperaccumulating plants in a pilot site set up between July and November 2023. The pilot site consisted of opaque monocrystalline and bifacial semi-transparent PV modules, beneath which culture trays of a hyperaccumulating plant, Noccaea caerulescens (Nc), were placed in addition to reference trays exposed to the sun without shade due to the PV modules. Several parameters were assessed, including the plant cover rate in trays, the dry biomass of Nc and the PV module temperatures. Regarding the Nc cover, plants growing in the shade of a PV module were up to 5.5 times more developed than those without shade, and all the indicators measured allowed plant cover to be differentiated according to the intensity of solar radiation. Furthermore, regarding the PV modules, the cover of Nc seemed to reduce the temperature on the back of the PV modules and improved their performance ratio by 18 % in October. Analysis of the relationship between solar radiation and PV module heating, taking into account the Nc cover, highlighted a potential evapotranspiration effect of the plant cover in reducing the temperature of the PV modules. These results highlighted the importance of managing plant cover under PV modules and taking it into account in the thermal modelling of PV modules in variable climatic conditions.