Linear diffraction modelling and ocean basin tests giving capture width, response, mooring forces and energy yield for several sites
The M4 wave energy converter originally consisted of three in-line floats increasing in diameter (and draft) from bow to stern so that the device heads naturally into the wave direction with power take off (PTO) from a hinge above the mid float. Linear diffraction modelling was found to make quite accurate predictions of power and response. This has been extended to a larger number of floats, up to eight with four PTOs. This showed that capacities similar to wind turbines were possible for some sites. Experimental comparison is presented for a six-float system with two PTOs. For irregular uni-directional waves with JONSWAP spectra measured power was a little larger than that modelled with maximum capture widths greater than one wave length for energy period. Wave conditions with different spectral peakedness and multi-directional spreading are applied and energy yield with electricity cost estimates made for 11 offshore sites. Without the PTO to give worst case response, results are presented for angular motion and mooring force variation with significant wave height up to extreme values for different peak periods. Angular motion is predominantly linear but mooring force is more complex with largest values in extreme waves occurring in the range of periods for operational conditions. Mean second-order forces have been added to the model, including effects due to a stationary body as standard, but effects due to radiation damping and the mechanical damping of wave energy conversion have been missing and are added here. However comparison with experiment indicates that mean mooring forces are generally underestimated.
Short biography of Professor Peter Stansby:
Peter graduated with a BA in Engineering from Cambridge University in 1971, and a PhD in aerodynamics three years later. His working life began in industry with the Atkins Group. In 1980 he joined the University of Manchester where he was awarded a DSc. He has been a Fellow of the Royal Academy of Engineering since 2001. His research interests have focused on offshore structures, coastal engineering, marine energy (wave and tidal), and Computational Fluid Dynamics (CFD) including Smoothed Particle Hydrodynamics (SPH). He has supervised over 60 grants/contracts mainly as PI and published 140 papers in Q1 journals, with a Scopus h-index of 35, making several seminal contributions. He is now the Osborne Reynolds Professor of Fluid Mechanics at Manchester.