||The Performance Assessment of Wave and Tidal Array Systems (PerAWaT) project, launched in October 2009 with £8m of ETI investment. The project delivered validated, commercial software tools capable of significantly reducing the levels of uncertainty associated with predicting the energy yield of major wave and tidal stream energy arrays. It also produced information that will help reduce commercial risk of future large scale wave and tidal array developments.
This report presents and discusses the results of fully nonlinear simulations of linear and nonlinear power take-off for controlled devices in regular wave interactions involving a single truncated cylinder (representing a wave energy device) and an array of four devices. By including nonlinear control and power take-off (PTO) in the device motion, the simulations here model more complex interactions.
The key objectives of this study were to demonstrate the capability of OXPOT in modelling linear and nonlinear PTO mechanisms – in later deliverables involving validation of the models by comparison with experiment it will be necessary to be able to simulate the experimental setup as closely as possible. The PTO force to be used in the experiments has been specified to be nonlinear in nature.
Furthermore, an investigation into the effect of nonlinearities in PTO forces and the influence of different control strategies on device response and device power take-off is conducted in this report. It outlines how these objectives have been met and describes any issues arising from their completion.
The analysis of the effects of the nonlinear PTO forces is conducted using the linear PTO force results as a frame of reference. Furthermore, the results of the single device PTO simulations are utilised in the analysis of the power absorption properties of the devices in a square array.