# Floating Photovoltaic Plant Monitoring: A Review of Requirements and Feasible Technologies
## 3 PV Floating Monitoring Issues
### Monitoring FPV Systems for Evaluating Their Impact on Water Ecosystem
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Possible Effects on the Ecosystem** & **Observed Effects in an FPV Plant** \\ \hline Submarine & The intensity of sunlight at different depths not only activates biological processes, but can also play a role in the migration of animal species. On the contrary, shading may also influence fish behavior, attracting fishes which perceive increased safety from predators or reducing interactions [57]. & Under an FPV system, UV reduction has been observed [59] \\ Turbidity (NTU/FNU) & Turbidity may be correlated to the presence of suspended particles. As it increases, the fraction of light that can reach underwater plants, either sessile or floating, decreases along with photosynthesis intensity. & A certain decrease in turbidity has been observed due to the lower presence of algae [60] under an FPV. \\ Water Temperature (\({}^{\circ}\)C) & The temperature of the water affects the chemical reaction kinetics and the overall concentration of dissolved oxygen. & The average temperature of the basin as a whole decreases by approximately \(1^{\circ}\)C as its occupation by the FPV increases from 0 to 90\%. Correspondingly, the Schmidt stability index is almost halved [61]. \\ \hline Dissolved Oxygen (mg/L) & It is an index of self-purification of water, and it gives direct and indirect information on bacterial activity, photosynthesis, and leads to stratification. & Dissolved oxygen tends to decrease in non-aerated basins [62] and is observed to decrease significantly below an FPV system [63]. \\ Chlorophyll-a (\(\mu\)g/L) & Chlorophyll a is a measure of the amount of algae growing in a water body. It can be used to classify the trophic condition of a water body. & A slight increase, however not statistically significant, is observed under the FPV plant [63], which seems in contradiction with what is reported in Ref. [60]. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The physical–chemical parameters to be controlled in the case of installations of floating plants with the related possible effects on the ecosystem as per ref. [58]. Therefore, if there is a general consensus on what should be monitored in an FPV plant, the issues of first \"where\" and second \"how\" to measure such parameters seems to be much less defined. Figure 3 shows a diagram of the possible contamination processes and of the consequent environmental risks associated with the installation of a photovoltaic system on a reservoir. As can be seen from the possible contamination paths highlighted in Figure 3, in general, it should be necessary to monitor water quality immediately under the floating photovoltaic system at various depths and to compare the observed values with those of samples collected relatively far away from it. This is in fact the general approach followed in all works published in the literature. There are, however, differences regarding how such measurements have to be carried out. [PERSON] and co-authors [66] carry out measurement campaigns by means of static systems for water sample collection, displaced immediately near and below the plant, which are then analyzed in the laboratory. A similar technique is used by the authors in refs. [63; 64] and also in ref. [67]. Always static but by means of the use of multiparametric probes is the approach proposed by [PERSON] and co-authors in ref. [68], which is therefore advantageous in terms of a more timely water analysis. On the contrary, [PERSON] [69] and co-authors propose the use of robotic systems for the control of multiple points both under the FPV plant and at a distance from it, suggesting that the measurements should be carried out in multiple points, immediately below the plant and away from it (100 m in the specific case studied by the authors) and at depths such as to cover the full water column. It is interesting to underline that such a monitoring approach, by means of automatic systems, has also been proposed in other