System design and control of a novel ocean wave energy converter array
L.R.A. Hogervorst (TU Delft - Mechanical Engineering)
Jan Willem van Wingerden – Mentor (TU Delft - Team Jan-Willem van Wingerden)
Nima Tolou – Mentor (TU Delft - Mechatronic Systems Design)
T. W.A. Blad – Mentor (TU Delft - Mechatronic Systems Design)
Paul Breedveld – Graduation committee member (TU Delft - Medical Instruments & Bio-Inspired Technology)
A. J. Jarquin Laguna – Graduation committee member (TU Delft - Offshore and Dredging Engineering)
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Abstract
There is a great amount of wave power in earth's oceans. The amount of power harvested for electricity is however very small in comparison to solar and wind. One of the reasons for this is the lack of consensus on the best design of wave energy converters. This thesis develops a novel system design for a wave energy converter array that has promise and implements, evaluates and compares control for it. The most important benefits of this new design versus the most used type of devices are that it does not rely on a connection to the ocean floor for energy harvesting and it is space efficient, meaning that devices lie close together. Control has never been designed for the type of device in this study to the best of this author's knowledge. The wave energy converter array consists of floating pontoons that are connected to each other. The wave energy is harvested through power take-off mechanisms in these connections. The most important requirement on the system design is survivability, as the ocean is a harsh environment. The kinematics are thus designed in such a way that forces on the connections can be set by the damping and stiffness coefficients of the connections. The array is optimized for efficient energy harvesting by its design, while keeping cost effectiveness in mind when possible. Not only the array itself is optimized for efficiency, the control is optimized for this as well. This means that the control problem is to maximize energy capture. Reactive and Resistive control are implemented and compared. A distributed version of these algorithms is investigated as well and improves on computation time for large arrays. Reactive control can improve upon Resistive control up to three times in terms of energy capture, depending on the efficiency of the power take-off mechanism. The reason for this great improvement is that Reactive control makes it possible for the array to reach resonance with the waves. The array performs average in terms of energy capture in comparison to other wave energy converters when Resistive control is used.