Among various renewable energy technologies, offshore Floating Photovoltaics (FPV) represents a new and favorable approach to the constantly diminishing amounts of fossil fuels and the need to reduce carbon emissions in the pursuit of a sustainable future. The advantages of an FPV system include the conservation of land areas and high PV efficiency because of the water cooling effect. Despite the advantages, offshore FPV technologies also face significant technical and economical challenges, and there are few robust systems that can withstand harsh offshore environmental conditions. To address the technical challenges of a recently proposed novel FPV concept using semi-submersible floats and rope connections, this thesis created, calibrated, and studied a numerical model for a model-scale FPV array. The FPV array consists of 3 by 2 modules with cross-shaped rope connection and horizontal moorings. The time-domain numerical simulations were carried out in OrcaFlex, which accounts for the structural behaviour of the FPV array and the fluid-structure interaction under wave loads. The numerical simulation results were compared against those obtained from hydrodynamic model tests for a physical model. Ten regular waves and three irregular waves with different wave periods and heights are considered. During the numerical study, the motion of a single floating body within the array, tension in mooring lines and the ropes connecting the floating bodies are analysed in detail. The results show that the Reponse Amplitude Operators (RAOs) of the numerical model have a percentage difference of less then 5.67% compared with those of the physical model in heave. An analysis of the tension in connecting ropes that tie the floating bodies together reveal that the diagonal ropes can experience snatch loads. A sensitivity study reveals that reducing the line stiffness can eliminate these snatch loads. Furthermore, spectral density graphs show a good comparison for irregular waves, the numerical and experimental surge and heave motion response appears to be excited at similar frequencies with similar spectral density. The outcomes of this study contribute to improved numerical modelling and comparison against physical models and more robust design of critical structural components (e.g., rope connection) for the novel FPV system.