Reliability prediction of a wave energy converter’s hydraulic power take-off system

Eetu Heikkilä (Corresponding author), Tero Välisalo, Janne Sarsama, Risto Tiusanen

Research output: Contribution to conferenceConference AbstractProfessional


MegaRoller wave energy converter (WEC) concept is being developed to produce cost-efficient renewable energy from the kinetic energy of ocean waves. The MegaRoller device consists of an oscillating flange, which captures the energy from waves, and two power take-off (PTO) systems that convert the kinetic energy into electricity. In the MegaRoller concept, the PTOs employ a hydraulic system that is used in producing electricity that fulfils power quality requirements and achieves system-level reliability targets. During its operation, the MegaRoller device is submerged, making reactive maintenance costly and impractical. Thus, the system is designed for a long maintenance interval. Careful reliability analysis is needed to predict the system reliability performance and assess the survivability of the device over the intended scheduled maintenance interval, keeping in mind the harsh maritime operating environment.

In this paper, we present results from reliability analysis of the hydraulic system in MegaRoller PTO. The analysis utilizes a system modeling and simulation approach based on reliability block diagrams (RBDs). RBD is a probabilistic reliability engineering method that can be used to predict system availability over time. It describes the system components as a combination of interconnected blocks, each assigned with a probability distribution describing the component’s reliability performance. As a visual method, it provides an easily comprehensible representation of the system reliability structure. It also supports the identification of most reliability-critical components and highlights important areas for reliability improvement. In our modelling approach, we utilize RBD calculation based on Monte Carlo simulation, created in ReliaSoft BlockSim software. In addition to building the actual system model, another major task is to identify and interpret relevant data sources to be able to assign reliability predictions for individual components. This is particularly challenging in new product development, as failure data from previous installations is not widely available.

The main three contributions presented in this paper are the following. First, we describe the system modeling process, highlighting some identified advantages and disadvantages of the RBD approach. Second, we describe the work done to identify reliability data sources and discuss their suitability in the wave energy context. Finally, we present selected results from the PTO hydraulic system RBD modeling effort.
Original languageEnglish
Publication statusPublished - 13 Apr 2021
MoE publication typeNot Eligible
EventAutomaatiopäivät24: Automaatio, kestävä kehitys ja tulevaisuus - Virtual, Finland
Duration: 13 Apr 202114 Apr 2021


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