# Floating Photovoltaic Plant Monitoring: A Review of Requirements and Feasible Technologies
###### Abstract  
Photovoltaic energy (PV) is considered one of the pillars of the energy transition. However, this energy source is limited by a power density per unit surface lower than 200 W/m\({}^{2}\), depending on the latitude of the installation site. Compared to fossil fuels, such low power density opens a sustainability issue for this type of renewable energy in terms of its competition with other land uses, and forces us to consider areas suitable for the installation of photovoltaic arrays other than farmlands. In this frame, floating PV plants, installed in internal water basins or even offshore, are receiving increasing interest. On the other hand, this kind of installation might significantly affect the water ecosystem environment in various ways, such as by the effects of solar shading or of anchorage installation. As a result, monitoring of floating PV (FPV) plants, both during the ex ante site evaluation phase and during the operation of the PV plant itself, is therefore necessary to keep such effects under control. This review aims to examine the technical and academic literature on FPV plant monitoring, focusing on the measurement and discussion of key physico-chemical parameters. This paper also aims to identify the additional monitoring features required for energy assessment of a floating PV system compared to a ground-based PV system. Moreover, due to the intrinsic difficulty in the maintenance operations of PV structures not installed on land, novel approaches have introduced autonomous solutions for monitoring the environmental impacts of FPV systems. Technologies for autonomous mapping and monitoring of water bodies are reviewed and discussed. The extensive technical literature analyzed in this review highlights the current lack of a cohesive framework for monitoring these impacts. This paper concludes that there is a need to establish general guidelines and criteria for standardized water quality monitoring (WQM) and management in relation to FPV systems. floating photovoltaic; autonomous surface vehicle (ASV); autonomous underwater vehicle (AUV); ROV; environmental monitoring; water quality monitoring (WQM); unmanned aerial vehicle (UAV); renewable energy; pervasive sensing +
Footnote †: journal: _sustainability_  
One of the major problems connected with the massive diffusion of this energy source is its low density of power installable per unit of surface area compared to conventional fossil sources, with an average energy produced per year and per unit of surface area which is 10-100 times lower than that produced, for example, by means of natural gas [2]. In the current state of photovoltaic sector technology, the power capacity that can be installed per m\({}^{2}\), even in the most favorable installation conditions, does not exceed 200 W/m\({}^{2}\)[3]. In these conditions, the diffusion of photovoltaic energy can imply a significant use of land areas, raising questions of competition with other land uses, such as agricultural uses. This opens ethical debates, since photovoltaic diffusion could create competition between the production of a good that is more relevant for richer countries, i.e., energy at the expense of another, e.g., food, which is still insufficient in many poor countries [4; 5]. In this context, the use of floating photovoltaics, which is characterized by photovoltaic systems built on water basins, including offshore areas, appears to be a particularly interesting solution to the aforementioned dichotomy since it could lead to a reduction in land consumption by approximately three times for photovoltaic system installation [6]. This may happen not only because FPV technology is potentially compatible with open sea offshore installations, with evidently no main conflicting problems with other area uses, but also due to the exploitation of internal basins, such as abandoned quarries, which generally have no other possible uses [7].