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Wave power is a potential technology for generating sustainable renewable energy. Several types of wave energy converters (WECs) have been proposed for this purpose. WECs operate in a harsh maritime environment that sets strict limitations on how and when the device can be economically and safely reached for maintenance. Thus, to ensure profitable energy generation over the system life cycle, system reliability is a key aspect to be considered in WEC development. In this article, we describe a reliability analysis approach for WEC development, based on the use of reliability block diagram (RBD) modelling. We apply the approach in a case study involving a submerged oscillating wave surge converter device concept that utilizes hydraulics in its power take-off system. In addition to describing the modelling approach, we discuss the data sources that were used for gathering reliability data for the components used in a novel system concept with very limited historical or experimental data available. This includes considerations of the data quality from various sources. As a result, we present examples of applying the RBD modelling approach in the context of WEC development and discuss the applicability of the approach in supporting the development of new technologies.

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Wave power is a promising technology for producing renewable energy. Several types of wave energy converters (WECs) have recently been developed and introduced as technical solutions for capturing the energy of ocean waves. One of the WEC types is an Oscillating Wave Surge Converter (OWSC) that extracts energy from wave surges and the movement of water within them. Reliable operation and high system availability of WECs are key aspects to achieve the levelized cost of energy (LCOE) targets. Systematic reliability engineering methods can offer valuable support for the design and evaluation of highly automated multi-technical WEC systems. Analytical and simulation-based methods such as Failure Mode, Effects and Criticality Analysis (FMECA), Reliability Block Diagrams (RBDs) and Life Cycle Cost (LCC) calculations can be utilized in from early conceptual design phase. The system approach aims to guide the work to right system hierarchy level and to enable the use of available but partly uncertain information for system models, analyses and simulations. The research on reliability engineering methodology in VTT is related to concept development and system design of an OWSC and especially its power take of system (PTO) in an ongoing EU funded research project 'MegaRoller'. Our results confirm that reliabilityengineering efforts should be considered as an interconnected and iterative process, and the system approach helps to look at things at the appropriate level and accuracy.

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