Date of Award

Spring 2010

Project Type

Thesis

Program or Major

Mechanical Engineering

Degree Name

Master of Science

First Advisor

Christopher M White

Abstract

In this study, a computer model of the dynamics and generator output of a point-absorber-type wave energy converter (WEC) was developed and evaluated against a 1:25 scale prototype in wave tank tests. The WEC consists of a circular wave follower buoy with a central hole which fits over a slender spar buoy that extends up through the follower buoy opening. The wave follower buoy slides axially on the spar, providing relative motion for the power take-off unit consisting of a rack-and-pinion configuration connected through gears to a permanent magnet generator. Linear wave theory is applied to determine the response of the floating buoys to ocean wave excitation, while the coupled dynamics of the internal components of the power take-off system are derived from first principals where possible and characterized experimentally. Analysis is performed in the time domain where the dynamics of the WEC can be optimally evaluated.

Model validation was completed by way of mechanical bench testing and by comparing predictions and measurements obtained in an independent series of wave tank experiments. The robustness of the model was investigated by evaluating its accuracy at predicting WEC performance with and without a damping plate attached to the spar buoy.

The results show good correlation of the predicted model performance to measured positional data and power generation. In regular waves, the predicted average power generation was within 6--54% of the measured value for configurations without the damping plate attached to the spar. With the addition of the damping plate attached to the spar, model predictions improved to within 0.9--37% of the measured value. A similar trend was observed for the power generation predictions in irregular sea states. Predictions of average power generation in irregular sea were within 55--510% of the measured value for configurations without the damping plate attached to the spar, and within 12--33% of the measured value for configurations with the damping plate attached to the spar.

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