The effect of device geometry on the performance of a wave energy converter

Wave energy presents an excellent opportunity to add much-needed diversification to the global renewable energy portfolio. However, a competitive levelised cost of electricity for wave energy conversion devices is yet to be proven. Here, we optimise the geometry of a wave energy device to maximise power while also minimising the power take-off reaction moments. Using theory, numerical modelling and optimisation techniques, we show that by including minimisation of reaction moments in the optimisation, instead of only maximisation of power, it is possible to substantially lower the design loads while maintaining high efficiency. Using the underlying physics of how geometry affects the wave-structure interaction, we explain the resulting performance of these new designs for wave energy converters. We examine the resulting geometries for practicality, including performance over a wide range of sea states, motion requirements, and performance in a real sea-state off the coast of Scotland, United Kingdom. Comparing against the single shape which extracts the theoretical maximum power, the optimal shapes found in our study extract almost as much power (12% less) with substantially less moment (reduced by up to 35%), revealing a promising direction for wave energy development.