Influence of a floating photovoltaic system on water quality

Abstract

The incessant search for ways to reduce damage to the environment is one of the factors that lead the technology and research sector to be in constant motion. In this sense, renewable energies, with an emphasis on photovoltaic solar energy, appear to reduce the use of fossil fuels, minimize aspects such as pollution and deforestation and also to benefit from environmental potentials that are available, such as the sun. Photovoltaic solar energy is considered an inexhaustible energy and its use has become more expressive in recent decades, although, due to the population and urban centers growth and also agricultural areas expansion, areas for the installation of large photovoltaic plants have become scarce. As a way of overcoming this obstacle, the installation of floating photovoltaic systems (FPS) appears as an alternative, however like all the development of new technologies, it has both positive and negative aspects related to its operation and its impacts on the environment. In this sense, an FPS was installed in the Passaúna reservoir, in the metropolitan region of Curitiba, as an experimental model, to generate energy for the water pumping system. This reservoir is one of which supplies water to the capital of the state of Paraná and it has been showing high concentrations of algae interfering in the water treatment system and also in its cost. The high concentration of algae is the characterization of eutrophication and it brings negative impacts to water such as taste, odor and, depending on its concentration and also the type of algae, it can be toxic to humans. Thus, a specific assessment of water quality and also the impacts of the installed FPS is important, especially in the regard of water quality. Therefore, the objective of this work is to evaluate the influence of the FPS on the water quality of the Passaúna reservoir, mainly related to algae growth. In addition to carrying out a comprehensive literature review regarding the impacts caused by FPS’s. For practical evaluation of water quality, five parameters were evaluated: pH, turbidity, ammonia nitrogen, nitrate and chlorophyll a were analyzed at six different points, three internals (I1, I2, I5) and three externals to the system (E1, E2, E3). The water sample collections were done on the water surface and at half the depth of each point. The collections were carried out between June and December 2022, fortnightly. For pH, the results range were among 7.1 to 8.4. For turbidity it varied among 0.917 NTU to 4.567 NTU. For ammonia nitrogen, the lowest result was 0.003 mg NH3-N/L and the highest was 0.185 mg NH3-N/L. Nitrate had the lowest result at 0.106 mg/L and the highest 0.436 mg/L. And for chlorophyll a, the results varied among 1.558 μg/L and 6.889 μg/L. Chlorophyll a results demonstrate that the reservoir is in the mesotrophic state, meaning that there is no eutrophication. Due to the area of the floating photovoltaic system representing less than 1% of the area of the reservoir, no significant influence of the system on water quality was found in any of the parameters analyzed. However, the literature presents positive aspects regarding floating photovoltaic systems, such as a reduction in water evaporation rates and a decrease in algae growth.