Experimental Investigation of Hydrodynamic Responses of Modular Floating Solar Arrays Under Irregular Wave Loading

Abstract Emerging renewable energy technology, such as Floating Photovoltaic (FPV) systems, is crucial for the process of slowing down and reversing climate change. This study presents experimental investigations into the wave-induced motions of modular FPV platforms subjected to irregular wave conditions. Two FPV configurations comprising strings of four and six rafts were assembled using rigid square modules connected by flexible tubular connectors to represent modular floating solar assemblies. Each string was moored at a single point using front and rear elastic mooring lines connected to a spring-based system pretensioned to 15 N. Tests were performed under calibrated JONSWAP-type irregular wave conditions with peak frequencies of 0.5 Hz and 1.0 Hz. Raft motions in heave, surge, pitch, and roll were recorded using a Qualisys motion capture system, and wave spectra were verified using multiple probes. Statistical and spectral analyses revealed that pitch motion consistently followed the dominant wave frequency, while heave and surge varied with wave period and array length. Longer-period waves (2 s) produced 3-4 times higher kurtosis values, indicating more stable and coherent motion, whereas shorter waves (1 s) induced multi-frequency excitation and pronounced roll resonance near 1 Hz. These findings provide quantitative insight into FPV hydrodynamics, supporting improved mooring design, scaling, and dynamic modelling of future offshore solar arrays.