Structural Reliability of Plain Bearings for Wave Energy Converter Applications

Simon Ambühl, Morten Kramer and John Dalsgaard Sørensen
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Simon Ambühl: Department of Civil Engineering, Aalborg University, Sofiendalsvej 11, Aalborg SV 9200, Denmark
Morten Kramer: Department of Civil Engineering, Aalborg University, Sofiendalsvej 11, Aalborg SV 9200, Denmark
John Dalsgaard Sørensen: Department of Civil Engineering, Aalborg University, Sofiendalsvej 11, Aalborg SV 9200, Denmark

Energies, 2016, vol. 9, issue 2, 1-20

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.

Keywords: plain bearing; probabilistic reliability assessment; sensitivity analysis; structural reliability; wave energy converter; Wavestar (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2016
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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