# Floating Photovoltaic Plant Monitoring: A Review of Requirements and Feasible Technologies
## 6 A Case Study for an FPV Autonomous Monitoring System
Object recognition is challenging beneath FPV because of poor lighting and backscattering caused by suspended particulates. The analysis of the water column could be also performed with multiparametric probes moored to an ASV (which guarantees movement in x and y in open waters) combined with an automated winch (to control sensor position in z). A more complex solution can be applied when the carrier is a team/swarm of ROVs/AVUs, also equipped with the necessary sensors and communication/self-localization capacity for team/swarm interaction. Docking systems [149] for launch, recovery, and automatic charging are necessary to reduce on-site human presence and allow remote management of the water body monitoring system. Some problems take advantage of simultaneous measurements. For example, Figure 5 shows an AUV swarm cooperating (data-driven) to efficiently map an illicit discharge outflow plume in a water body. The monitoring speed indicated by the authors (0.5 km\({}^{2}\) in 2 h) is probably optimistic, but it is useful to have an order of magnitude of the time needed to monitor a large water body with mobile sensors. The aim of this paragraph is to identify and highlight issues that can be encountered when studying an autonomous monitoring system for FPV installations. The study of an autonomous (with reduced human intervention) monitoring system depends heavily on the problem at hand: climatic conditions, water body types, currents, tidal effects, coverage ratios, etc. Water bodies on which an FPV system is planned to be installed (or has already been installed) can have, for example, very different dimensions. Areas can vary from 1 ha to 10,000 ha (10 km \(\times\) 10 km) [56] or more, and the depths generally range from less than one meter to several tens of meters. Large areas to be monitored [21; 56], very shallow water, algae bloom, etc., are issues to pay attention to for designing an autonomous monitoring system. Large areas are challenging because vehicles like ROVs, AUVs, and ASVs have limited resources in terms of navigation speed, battery life before recharge or substitution, tether length (for ROVs), etc. Furthermore, when monitoring a large area with mobile sensors in short-term analyses, survey timing could be comparable with the phases of some thermodynamic forcings such as solar radiation and wind intensity and direction. Water bodies in some cases present an algal bloom problem. A classic hub propeller may not be suitable in this situation. The design of an ROV/AUV/ASV from scratch for use in a such monitoring system could evaluate propellers such as Rim-Driven Thrusters (RDTs) [150]. Their further characterization regarding hydrodynamic performance, durability, etc., would be useful, specifically in their use with ROVs/AUVs. Commercial products exist, from large ships (Rolls-Royce, Schottel, Brunvoll, Voiith, Van der Velden) to small ROV/AUV prototypes, as in [151]. Other authors used an ROV to obtain vertical profiles of water quality in FPV systems [69]. The measuring strategy of [PERSON] et al. was to measure and compare water quality at several depths at the center of the solar farm (beneath the FPV) and at a reference location located over 100 m away from the FPV outside its influence. The authors compared measurements acquired with static sensors (configuration 1) with measures taken with the same sensors on an ROV (configuration 2).