Towards reliable and survivable ocean wave energy converters

Graduation date: 2010Ocean wave energy is a new and developing field of renewable energy with great\ud potential. The energy contained in one meter of an average wave off the coast of Newport Oregon could supply dozens of homes with electricity. However, ocean waves are usually quite irregular which leads to large bursts and lulls in the power available for extraction. These bursts and lulls generate large cyclic system stresses that will invariably work over time to damage an ocean wave energy converter.\ud Due to the generally remote and extreme conditions of deployment, the reliability and survivability of an Ocean Wave Energy Converter (OWEC) are expected to greatly impact the cost of generated power passed to the consumer. For this reason, it is imperative that OWECs are both highly reliable during operation, and highly survivable through extreme conditions.\ud This thesis is a compilation of three papers relating to the reliability and survivability of OWECs. The first paper broadly addresses the probabilistic design of ocean wave energy converters for real ocean waves. The analysis conducted in this paper used 13 years of data from the Stonewall Banks data buoy off the coast of Newport Oregon (NDBC buoy 46050) to extrapolate probabilistic information that could be used throughout the design process to improve system reliability. The second paper provides a definition and metric for the widely used term survivability. Survivability is often confused with the similar concept of reliability. The paper seeks to highlight differences between the two terms with the intention of clarifying their relation to system design. The final paper presents a method for concept evaluation in the earliest stages of design. A comparative function based failure analysis is conducted during the concept stage to aid in design selection. Selecting concepts that show promising failure traits early in the design process will improve the reliability and survivability of the final system