A Seamless Integration of Communications, Networks, Distributed and Hierarchical Control for Reliable Conversion of Ocean Wave Energy to Electricity

Oregon State University, Corvallis OR

Investigators

Abstract

Solar radiation produces wind which, when it blows over the ocean surface, generates waves. These waves can travel very long distances with little energy loss. Most importantly, these waves are a source of clean energy readily available for harvesting using appropriate wave energy converters such as oscillating water column converters. Currently, most ocean wave energy conversion projects deal with design, development and testing of single wave energy converters. This research project proposes a vision of a large-scale wave energy conversion park which is capable of generating the electrical power of a large power generating plant. To achieve this goal, a wave energy converter park can be designed as a large intelligent system with intra wave energy converters communication, supervisory global control, and active local control to maximize clean electrical energy generation. The main benefit from the application of the ideas herein proposed is a significant increase in year-round electricity productivity. In fact, it can be shown that hydrodynamic active control as proposed in this research project could increase annual energy conversion productivity by a factor in the range of 1.5 to 2.8. Most wave energy converters absorb energy by means of an oscillatory motion that makes waves which constructively and/or destructively interfere with the incoming waves. A wave energy converter with fixed geometry and mass possesses a natural period, and it is known that the energy absorption from the sea is largest when the natural period agrees with the wave period, namely at resonance. When this is not the case, a passive wave energy converter has a natural response that is not optimal. This means that there is a possible motion other than the natural one that would absorb more energy. Specifically, in terms of sinusoidal waves and oscillations, there exist optimal values of phase and amplitude of the natural response which could be matched by the wave energy converter using optimal control. Hence, an optimal active control of the primary conversion system can be devised so that the electricity production can be maximized. In essence, what active control can do is to use the machinery in a purposeful way to change the dynamical resistance and mechanical reactance felt by the waves when they act upon the wave energy converter. Therefore, the proposed research will develop new active control techniques which will modify the motion of a wave energy converter closer to one or both of these parameters using both local and global wave climate information gathered by a network of sensors deployed on the wave energy park and other sources such as National Data Buoy Center.