Structural Reliability of Plain Bearings for Wave Energy Converter Applications

Abstract

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.

Statistical Analysis and Data Envelopment Analysis to Improve the Efficiency of Manufacturing Process of Electrical Conductors

“…In the present project, it is very useful to compare the use of ANOVA in [3,4], to improve the proposed method of analysis. Through optimizing other variables such as those mentioned in [5,6] it is possible to generate substantial improvements that will be taken into account in future work in the optimization of manufacturing processes. It can be concluded that DEA model is a method that can be of great help, and although it will not replace the DOE, if it allows manufacturing companies to perform analysis and process improvements in a faster way.…”

“…In [4], developed the DOE, improved manufacturing tolerances in permanent magnet motors. Taking into consideration [5], applied the DOE in a spot welding process to identify the key parameters of the process, which influence the tensile strength of welded joints. Also, DOE had been employed successfully en R&R analysis [6], surface response analysis [7] and, algorithm analysis [8].…”

Assessing wave energy converters in the gulf of Mexico using a multi-criteria approach

“…The Wavestar WEC is described as a point absorber (Marquis et al, 2012;Ambühl et al, 2016;Heo and Koo, 2021), oscillating body system or wave activated system (Chen et al, 2018;Curto et al, 2021), or attenuator (Amrutha and Sanil Kumar, 2022). It is essentially a group of floats whose operation does not depend on the direction of the waves, ascending and descending with the upward and downward motion of the waves.…”