Integrated hydrodynamic-electrical hardware model for wave energy conversion with M4 ocean demonstrator

Marine wave energy is a potentially valuable renewable energy resource that can share the same infrastructure as floating wind, with a complementary power delivery pattern. Despite many small-scale sea trials, most previous results are not in the public domain and the technology remains immature. This programme aims to put a 20 m long, kW scale, wave-to-wire multi-modal raft attenuator into the sea in 2023/24, and make datasets ranging from site wave resource surveys to real-time electrical power generation available to researchers. This paper addresses the project design stage, covering the full system integrated hydrodynamic-electrical modelling and hardware specifications for both dry testing and sea trials. The modelling reveals the inter-relationships between the mechanical platform and electrical system constraints. Models are applied to identify the operational limits of the power take-off, particularly the generators, and show how this impacts on total energy extracted with conventional linear damping control. The exercise has identified the energy-storage isolation transformer as under-specified –this is a relatively low-cost item that can be upgraded. The gearbox has emerged as a more significant limiting factor for power scale-up.