Wave energy is an active area of research which deals with one of the largest untapped sources of renewable power in the modern world - the energy contained within the oscillation of ocean surface waves. Many different types of prototype wave energy devices are currently under development, one of which is the CCell - an asymmetric oscillating surge wave energy converter with a novel curved shape. This thesis describes the development of a numerical model of an array of CCell devices, with a realistic power take-off (PTO) model and control strategy having been implemented for an individual device. This model has been used to investigate various methods of improving the economic viability of arrays using fault-tolerant control strategies and efficient array layouts.Firstly, the open-source boundary element method (BEM) solver NEMOH has been used to generate a hydrodynamic model of the device, which is tuned against data from laboratory-testing. A realistic model of a hydraulic power take-off unit has also been developed to accurately simulate the non-linear effects in a hydraulic circuit such as friction, flow losses and limited stroke lengths.Next, a number of control strategies have been evaluated for improving the device’s performance across a range of sea-states, based on maximising the power captured while still keeping the device within well-defined position constraints. The effects of parameter variation and faults have also been studied, and a simple methodology has been presented to prevent a device from getting damaged in large waves.Finally, the open-source toolbox WEC-SIM has been used to model three different array configurations for three-device CCell arrays. Each array configuration has been simulated across a range of wave frequencies, at different device spacings and damping ratios to study the effect of hydrodynamic interactions between devices. A novel methodology has been presented to evaluate the practical viability of each array configuration,using which the most effective and space-efficient array layouts have been identified.
Modelling, Control and Optimisation of an Array of Non-linear Oscillating Wave Surge Converters
Chandel, D. (Author). 6 Sept 2018
Student thesis: Doctoral Thesis › PhD