Floating photovoltaic solar energy decreases water temperature and near-surface dissolved oxygen

Abstract Climate change and urbanization disrupt water body hydrothermal dynamics, altering aquatic ecosystems, water quality, and availability. Floating solar photovoltaic energy installations (FPVs) offer benefits by providing shade and generating renewable energy, supporting decarbonization goals. Despite limited studies on FPV impacts, we observed and analyzed three US water bodies with FPV installations. Results indicate an overall water cooling effect, on average, of 0.53 °C when FPV covers the majority of the water body, with maximum cooling reaching 2 °C during warmer summer months. Diel temperature ranges beneath the FPV were also lower, especially during high-temperature summer months. However, average dissolved oxygen levels were substantially lower (0.33–1.2 mg l −1 ) under FPV than in open water, possibly posing challenges to maintaining a healthy aquatic ecosystem. Our results reveal FPV’s potential as a passive mitigation measure against warming waters.