Declutching control of a wave energy converter

When hydraulic power take off (PTO) is used to convert the mechanical energy of a wave energy converter (WEC) into a more useful form of energy, the PTO force needs to be controlled. Continuous controlled variation of the PTO force can be approximated by a set of discrete values. This can be impleme...

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Bibliographic Details
Published in:Ocean engineering 2009-09, Vol.36 (12), p.1015-1024
Main Authors: Babarit, Aurélien, Guglielmi, Michel, Clément, Alain H.
Format: Article
Language:English
Subjects:
Applied sciences
Declutching control
Energy
Energy of waters: ocean thermal energy, wave and tidal energy, etc
Engineering Sciences
Exact sciences and technology
Fluid mechanics
Fluids mechanics
Hydraulic power take off
Mechanics
Natural energy
Optimal command
Physics
Wave energy converter
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Summary:When hydraulic power take off (PTO) is used to convert the mechanical energy of a wave energy converter (WEC) into a more useful form of energy, the PTO force needs to be controlled. Continuous controlled variation of the PTO force can be approximated by a set of discrete values. This can be implemented using either variable displacement pumps or several hydraulic cylinders or several high pressure accumulators with different pressure levels. This pseudo-continuous control could lead to a complex PTO with a lot of components. A simpler way for controlling this hydraulic PTO is declutching control, which consists in switching on and off alternatively the wave energy converter's PTO. This can be achieved practically using a simple by-pass valve. In this paper, the control law of the valve is determined by using the optimal command theory. It is shown that, theoretically when considering a wave activated body type of WEC, declutching control can lead to energy absorption performance at least equivalent to that of pseudo-continuous control. The method is then applied to the case of the SEAREV wave energy converter, and it is shown than declutching control can even lead to a higher energy absorption, both in regular and irregular waves.
ISSN:0029-8018
1873-5258
DOI:10.1016/j.oceaneng.2009.05.006