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Energies 2016, 9(2), 118; doi:10.3390/en9020118

Structural Reliability of Plain Bearings for Wave Energy Converter Applications

1
Department of Civil Engineering, Aalborg University, Sofiendalsvej 11, Aalborg SV 9200, Denmark
2
Wave Star A/S, Park Allé, Brøndby 2605, Denmark
*
Author to whom correspondence should be addressed.
Academic Editor: John Ringwood
Received: 4 December 2015 / Revised: 22 January 2016 / Accepted: 4 February 2016 / Published: 19 February 2016
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Abstract

The levelized cost of energy (LCOE) from wave energy converters (WECs) needs to be decreased in order to be able to become competitive with other renewable electricity sources. Probabilistic reliability methods can be used to optimize the structure of WECs. Optimization is often performed for critical structural components, like welded details, bolts or bearings. This paper considers reliability studies with a focus on plain bearings available from stock for the Wavestar device, which exists at the prototype level. The Wavestar device is a point absorber WEC. The plan is to mount a new power take-off (PTO) system consisting of a discrete displacement cylinder (DDC), which will allow different hydraulic cycles to operate at constant pressure levels. This setup increases the conversion efficiency, as well as decouples the electricity production from the pressure variations within the hydraulic cycle when waves are passing. The new PTO system leads to different load characteristics at the floater itself compared to the actual setup where the turbine/generator is directly coupled to the fluctuating hydraulic pressure within the PTO system. This paper calculates the structural reliability of the different available plain bearings planned to be mounted at the new PTO system based on a probabilistic approach, and the paper gives suggestions for fulfilling the minimal target reliability levels. The considered failure mode in this paper is the brittle fatigue failure of plain bearings. The performed sensitivity analysis shows that parameters defining the initial crack size have a big impact on the resulting reliability of the plain bearing. View Full-Text
Keywords: plain bearing; probabilistic reliability assessment; sensitivity analysis; structural reliability; wave energy converter; Wavestar plain bearing; probabilistic reliability assessment; sensitivity analysis; structural reliability; wave energy converter; Wavestar
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Ambühl, S.; Kramer, M.; Dalsgaard Sørensen, J. Structural Reliability of Plain Bearings for Wave Energy Converter Applications. Energies 2016, 9, 118.

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