On-site real-time stress health monitoring of the steel structure of a floating photovoltaic system installed in the Soyang River over a 7-year period

Abstract The design of floating photovoltaic (PV) systems faces challenges owing to irregular environmental stressors, such as unpredictable wind speeds, wave heights, wave periods, and tidal flows. Environmental factors cause repetitive dynamic movements of the components of these systems, leading to fatigue stress. In this study, on-site real-time stress health monitoring of the material stress changes in the steel structure of a floating PV system located in a river was conducted under environmental stress conditions. A 50.4 kWp floating PV system was installed in the Soyang River in the Republic of Korea. The support structure for this system is made of steel coated with a Zn–Mg–Al alloy. To monitor environmental conditions and structural dynamics, various sensors were deployed. For real-time dynamic analysis of the movement of the steel structure, rosette strain gauges were installed. To analyse the real-time stress–strain characteristics, rosette strain gauges were placed at the connecting points of the steel structure. A maximum wind speed of 21 m/s was recorded over a period of 7 years starting in 2017. The C-type steel structure supporting the horizontal placement of the PV modules exhibited the highest stress, reaching 54.5 MPa, with stress levels increasing in correlation with the wind speed. As the floating PV structure moved over a certain distance along the X–Y axis in response to the wind pressure and surface waves at low water levels, a snap-induced impact occurred due to mooring. The stress generated under high water-level conditions with slack to taut transitions in the mooring lines of the floating PV system was greater than that observed under low water-level conditions at lower wind speeds.