Research Papers: Ocean Renewable Energy

The Effect of Environmental Contour Selection on Expected Wave Energy Converter Response

[+] Author and Article Information
Samuel J. Edwards

Naval Architecture and Marine
Engineering Department,
University of Michigan,
Ann Arbor, MI 48109
e-mail: sjedw@umich.edu

Ryan G. Coe

Sandia National Laboratories,
Water Power Technologies Department,
Albuquerque, NM 87185
e-mail: rcoe@sandia.gov

1Corresponding author.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received September 13, 2017; final manuscript received July 6, 2018; published online August 13, 2018. Assoc. Editor: Qing Xiao.The United States Government retains, and by accepting the article for publication, the publisher acknowledges that the United States Government retains, a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for United States Government purposes.

J. Offshore Mech. Arct. Eng 141(1), 011901 (Aug 13, 2018) (7 pages) Paper No: OMAE-17-1165; doi: 10.1115/1.4040834 History: Received September 13, 2017; Revised July 06, 2018

A wave energy converter must be designed to both maximize power production and to ensure survivability, which requires the prediction of future sea states. It follows that precision in the prediction of those sea states should be important in determining a final WEC design. One common method used to estimate extreme conditions employs environmental contours of extreme conditions. This report compares five environmental contour methods and their repercussions on the response analysis of Reference Model 3 (RM3). The most extreme power take-off (PTO) force is predicted for the RM3 via each contour and compared to identify the potential difference in WEC response due to contour selection. The analysis provides insight into the relative performance of each of the contour methods and demonstrates the importance of an environmental contour in predicting extreme response. Ideally, over-predictions should be avoided, as they can add to device cost. At the same time, any “exceedances,” that is to say sea states that exceed predictions of the contour, should be avoided so that the device does not fail. For the extreme PTO force response studied here, relatively little sensitivity to the contour method is shown due to the collocation of the device's resonance with a region of agreement between the contours. However, looking at the level of observed exceedances for each contour may still give a higher level of confidence to some methods.

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Grahic Jump Location
Fig. 1

All contours with data from NDBC Buoy 46022 as well as energy period choices for analysis

Grahic Jump Location
Fig. 2

Spectral density function for the PTO force time series from the PCA contour method with an energy period of 12.76 s

Grahic Jump Location
Fig. 3

Extreme PTO force response for each contour method at given energy periods

Grahic Jump Location
Fig. 4

Relationship between significant wave height and PTO force

Grahic Jump Location
Fig. 5

Power take-off extreme response prediction coefficient of variation amongst contour methods for a range of sea state energy periods



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