Designing Short-Term Wave Traces to Assess Wave Power Devices
- Pál Schmitt (Queen’s University Belfast) | Lucas Danisch (TU Hamburg-Harburg) | Paul Lamont-Kane (Queen’s University Belfast) | Björn Elsäßer (Queen’s University Belfast)
- Document ID
- International Society of Offshore and Polar Engineers
- International Journal of Offshore and Polar Engineering
- Publication Date
- March 2018
- Document Type
- Journal Paper
- 46 - 53
- 2018. The International Society of Offshore and Polar Engineers
- statistics, wave parameters, nonlinear effects, experimental tank testing, wave trace, Sea state
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- 15 since 2007
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It is generally accepted that an estimate of mean power capture for a wave energy converter (WEC) in a given sea state can only be obtained over many hundreds (or thousands) of wave cycles. The difficulty stems from the fact that WECs typically exhibit significant nonlinearities in their responses. A reduction in the number of wave cycles needed to obtain accurate results would allow the use of numerical tools for design optimization tasks that are currently too computationally demanding. In this paper, experimental time traces are analyzed to provide reasonable estimates of relative variations in device performance using short-duration sea states. We examine the suitability of various metrics of surface elevation time traces by comparing corresponding WEC data of interest. The results show that carefully selected wave traces can be used to reliably assess variations in power output due to changes in hydrodynamic design or wave climate. It is also demonstrated how confidence levels increase with running time, so in the future simulations could be run until sufficient accuracy is achieved to choose the best design.
One of the most common methods used in the development of wave energy converters (WECs) is physical experimentation undertaken in a wave tank, which can be both time consuming and expensive.
Oscillating wave surge converters (OWSCs) are designed to be deployed in the near shore region in water depths of approximately 12–15 m and utilize the amplified surge motion of water surface waves in this region to pitch back and forward about a hinge mounted on the seabed. The basic concept is shown in Fig. 1.
One design feature of OWSCs is the shape of the side edges (as shown in Fig. 2). The thickness of the edges of the flap affects energy loss, as a result of viscous effects, and thus power capture (Cameron et al., 2010).
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