Testing, Analysis and Control of Wave Dragon, Wave Energy Converter

James Tedd

    Research output: Book/ReportPh.D. thesis

    1660 Downloads (Pure)

    Abstract

    One of the prongs in the attack on climate change is the development of alternative, non-polluting sources of energy. Wave Dragon is a device at the forefront of this field of development, converting the energy of ocean waves into electricity. This thesis presents the author's work on the technical aspects of the device. The work has been enabled by the close co-operation of the Wave Dragon partner companies and the use of the highly instrumented prototype device in Nissum Bredning in Northern Denmark.

    This thesis is presented as a collection of works published by the author. These include a chapter of a textbook, a submitted journal paper and three peer-reviewed conference papers. The content can be broadly divided into four topics: experiences gained with the Wave Dragon prototype device; power-production verification; overtopping analysis; and improvements in control.

    A comprehensive record of the process Wave Dragon has undergone to develop from an inventor's concept to a serious contender in the wave energy industry is very valuable. This shows the gradual steps of development testing, increasing in scale and complexity, in parallel with the growth in the organisational structure behind the device. The current high-point of this, the autonomously operating prototype, is presented in detail to show the operating methods, instrumentation and the challenges experienced during its lifetime.

    The purpose of the Wave Dragon is to produce electricity. Therefore at each increment in scale the first question asked is: "Does it produce as much as expected?" To answer this question results are presented from testing of the prototype device. This has given the broad answer "Yes", although the answer must be qualified by discussing operation away from the optimal configuration, and methods to scale the expected performance. Other sources of generation are presented, including development and tank testing of a novel power absorbing joint.

    Wave Dragon belongs in the family of overtopping wave energy converters. The energy is captured by waves running up a ramp and overtopping the crest into a reservoir. This stored water, at a higher level than the sea, is returned through lowhead turbines powering electrical generators. To improve the quality of modelling of these devices, the short-term characteristics of this overtopping flow are presented based on measurements taken on the prototype.

    Advance knowledge of the incident waves upon a wave device allows the possibility of accurately tuning the power-take off mechanism (the hydro-turbines for the Wave Dragon) to capture more energy. A digital filter method for performing this prediction in real-time with minimal computational effort is presented. Construction of digital filters is well known within signal processing, but their use for this application in Wave Energy is new. The filter must be designed carefully as the frequency components of waves travel at different speeds.

    Research presented in this thesis has advanced the development of the Wave Dragon device and contributes to the stated objective of furthering research in the wave energy field.

    Original languageEnglish
    Place of PublicationAalborg
    PublisherDepartment of Civil Engineering, Aalborg University
    Number of pages116
    Publication statusPublished - 2007
    SeriesDCE Thesis
    Number9
    ISSN1901-7294

    Keywords

    • Wave Dragon
    • Wave energy converter
    • Sustainable Energy
    • Nissum Bredning

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