A method for comparing wave energy converter conceptual designs based on potential power capture
Section snippets
Background
Ocean waves are a vast, high-density renewable energy resource. The IEA estimates annual global wave energy potential of 29,500 TWh [1], which represents approximately 150% of annual global electricity demand [2]. In spite of this tremendous potential, there is currently no commercial deployment of a Wave Energy Converter (WEC) and, as is typical of a pre-commercial sector, proposed WEC conceptual designs vary widely [3], [4], [5]. This divergent design space exists, in part, due to the absence
Theory
Circuit methodologies originate from network theory in which physical systems are described in topological form as edges connected between nodes [22], [23]. Mathematical representation comes by means of associating constitutive equations expressing the physics for each edge. Circuits in which the substitution, superposition, and the reciprocity theorems hold are categorized as linear, satisfy the uniqueness criteria, and are suitable for simplification through application of Thévenin or
Methods
In this section we explore the potential of the mechanical circuit technique by progressively modelling more complex WEC architectures and determining the expressions for and as a precursor to the power analyses of Section 4. We start with a rederivation of Falnes' result for the intrinsic impedance of a heaving SRPA device. The SRPA system topology is then perturbed through addition of a new damper element representing linear viscous friction in parallel with the PTO. A perturbed
Discussion
To generalize our findings, we explicitly note Thévenin's theorem was successfully applied to all three WEC architectures described in Section 3 regardless of topological complexity, yielding the canonical form represented by Fig. 2e. In the following section, we now use these algebraic equations for and from Section 3 to build analytical expressions for that can be mined to establish important design principles applicable to linear WEC architectures. In the case of Falnes'
Conclusions
To be a competitive form of renewable energy, WEC conceptual design convergence must be achieved and further research efforts need to focus on areas with promising performance. To encourage the identification of WEC architectures which support this goal, a systematic methodology using the mechanical circuit framework has been proposed which builds on the fundamental contributions of Falnes to optimal PTO force control already widely accepted in the wave energy community. Through generalizing
Acknowledgments
We would like to acknowledge the support of the Natural Sciences and Engineering Research Council of Canada, Natural Resources Canada, and the Pacific Institute for Climate Solutions in funding this research. Personal gratitude goes to Dr. Helen Bailey, Dr. Scott Beatty, and Mr. Alexandros Dimopoulos for various helpful discussions in formalizing the theoretical basis for this work.
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