Energy and Power Engineering, 2013, 5, 72-77 doi:10.4236/epe.2013.54B014 Published Online July 2013 (http://www.scirp.org/journal/epe) Hydraulic Power Take-off and Buoy Geometries Characterisation for a Wave Energy Converter Pedro Beirão, Cândida Malça Mechanical Engineering Department, Coimbra Polytechnic Engineering Institute, Coimbra, Portugal Email: pbeirao@isec.pt Received April, 2013 ABSTRACT In the past few decades, world energy consumption grew considerably. Regarding this fact, wave energy should not be discarded as a valid alternative for the production of electricity. Devices suitable to harness this kind of renewable en- ergy source and turn it into electricity are not yet commercially competitive. The work described in this paper aims to contribute to this field of research. It is focused on the design and construction of robust, simple and affordable hydrau- lic Power Take-Off using hydraulic commercial components. Keywords: Hydraulic Power Take-off; wave Energy Converter; Simulation; Structural Analysis; Buoy Geometries 1. Introduction In the past few decades, world energy consumption grew considerably and the tendency is to increase even further. Regarding this fact, wave energy should not be discarded as a valid alternative for the production of electricity. Different countries with exploitable wave power re- sources are considering wave energy as a viable source of power supply. Governments introduced several meas- ures to help researchers and the industry towards the de- velopment of technically feasible wave power conversion technologies in the medium and long term. Devices suitable to harness this kind of renewable en- ergy source and turn it into electricity, called Wave En- ergy Converters (WECs) are not yet commercially com- petitive when compared with more mature renewable technologies, such as wind and solar energy. There are several concepts being tested and some of them have already reached full scale. In order to convert wave energy into electricity WECs must have some kind of Power Take-Off (PTO). PTO systems should include, among others, the ability to cre- ate high thrust because sea waves produce low velocity movement of floating bodies; high efficiency which is related from the economical point of view with the price of electricity; low maintenance requirements due to the obvious WEC inaccessibility during large periods of time [1]. The WEC and its hydraulic PTO components are illus- trated in Figure 1. This system should provide a reaction force at the hy- draulic cylinder in order to harness energy from the floa- ter motion. As a matter of fact the force developed by the buoy is transmitted through the PTO system. As a consequence the hydraulic cylinder pumps oil from the tank to the accumulator and the fluid returns to the tank trough the hydraulic motor. The floater has a mass and a vertical stiffness associated with the buoy- ancy force and the PTO behaves as a viscous damper with non-linear features due to the valves opening and closing. Being a near shore WEC, the hydraulic PTO components (rectangle of Figure 1) should be enclosed in a sealed waterproof platform placed at the seabed and the foundations should provide the reaction force [1]. The hydraulic PTO converts the reciprocating motion of the hydraulic cylinder into a rotary motion of the hydrau- lic motor coupled to an electrical generator. It is well known that particles near the sea surface move in circles Figure 1. WEC with hydraulic PTO [1]. Copyright © 2013 SciRes. EPE