Optimisation of the Output of a Heaving Wave Energy Converter

  • Ka Lok

Student thesis: Phd


This research project is to investigate the control of the wave power device, known as the "Manchester Bobber" (MB), and to optimise the output by tuning its drive-train parameters. The work starts with building a numerical model and developing a control strategy. The work sequentially progressed to obtain the experimental results from a physical model in order to make a comparison with the numerical results.An assessment of three different control strategies is made. These are reactive control, latching control, and two methods of torque control based on either time-averaged velocity or a pre-defined static characteristic. It is found that reactive control and latching control are not feasibly applicable to the MB wave energy device due to the configuration of the device. It is also found that the historical data approach is able to reduce the problem of high rate of change of electromagnetic torque but with a subdued output performance. A method based on a static characteristic, similar to the approach used to control wind turbines, is shown to significantly enhance the power output performance although this imposes a high rate of change of electromagnetic torque.The findings of the numerical simulation are supported by experimental measurements obtained in the wave tank. The parameters used in the numerical model (i.e. hydrodynamic damping co-efficient, added mass co-efficient and Froude-Krylov force co-efficient) are calibrated by comparing with the experimental measurements.Two drive-train parameters, the number of generator poles and flywheel inertia, are optimised in order to both maximise output power and minimise rate of change of electromagnetic torque. The proportional gain and integral time constant of the PI controller are tuned to further reduce the maximum rate of change of electromagnetic torque, so that the device is protected from the high mechanical stress. It is found that the annual energy production from the device at a range of locations is found to be almost linear with the annual average significant wave height of each site.
Date of Award31 Dec 2010
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorPeter Stansby (Supervisor) & Timothy Stallard (Supervisor)


  • Wave Energy Converter

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