Metal contaminant risk at active floating photovoltaic sites and future research roadmap

Floating photovoltaics (FPVs) are solar energy systems deployed in aquatic environments, sparing land for other uses. It has been nearly twenty years since photovoltaics were first deployed on water bodies as FPVs. However, the potential for FPVs to contaminate host basins with metals due to some FPV components containing metals is understudied. We conducted a pilot study investigating cadmium (Cd), chromium (Cr), iron (Fe), manganese (Mn), lead (Pb), and tin (Sn) concentrations and their variability at FPV sites in two states in the United States. Next, we contextualized these results using the heavy metal evaluation index (HEI) to understand risks to human health. We found that the predominant metals at the FPV sites were Fe and Mn, and Cd was the least occurring metal. The greatest and least variable metals were Fe and Cd for the study sites. The total mean concentration of metals from the “FPV” and “Open” nodes at the FPV site for SITE 1 (59.92 ppb) was lower than the reference “Control” (76.43 ppb), the latter driven predominantly by the presence of Fe and Mn. The HEI revealed that water at the FPV-host basins have metal concentrations two orders of magnitude below the threshold for low metal pollution (<10), interpreted as safe for drinking. We leveraged these results and those from previous studies to develop an experimental framework and conceptual roadmap to guide future experimental research toward establishing high confidence in metal source attribution at FPV sites.