Current Technologies
In this section, one example of each broad type of wave energy converter has been described briefly although there are many more technologies available today: Oscillating water columns (LIMPET), Heaving buoys (WaveBob), Pitching devices (Pelamis), Bottom-hinged systems (Power-Oyster) and Overtopping converters (Wave Dragon).
Oscillating Water Columns
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Oscillating water columns or OWCs are the only viable onshore wave energy converters to date and these devices are the focus of this project. The first grid connected OWC device was the LIMPET on the Isle of Islay. The video on the left made by Voith Hydro Wavegen Ltd. - designers and operators of the plant - presents the LIMPET and how it works. Also, a live webcam of the device can be viewed here: LIMPET Webcam and the Voith Hydro website can be accessed by clicking here. For more information on OWCs click here. For the sake of showing a more complete overview of available technologies, a few of the other promising wave energy converters being researched are listed below. |
WaveBobWavebob is an axi-symmetric, self-reacting (or inertial) oscillating point absorber which primarily works in 'heave' mode. Unlike other self-reacting heaving buoys, its natural frequency can be set to match the typical ocean swell [1]. It is a two-body heaving system in which the relative axial motion between the two floating bodies pushes high-pressure-oil through a hydraulic circuit which drives an electrical generator [2].
'Body 1' in the picture on the left is floats on the surface of the water while 'Body 2' is fixed to a weight which increases its inertia, causing it to oscillate at a different frequency [3]. Click here to access the Wavebob website |
PelamisThe Pelamis - pictured left and designed by Pelamis Wave Power Ltd. - is an 'attenuator' type of WEC which lies parallel to the predominant wave direction. It looks like a sea-snake and is an articulated structure made up of four floating cylindrical segments joined together by hinges [4]. It is deployed at depths of 50m+ and the wave motion induced in the joints between each segment is resisted by hydraulic rams which pump oil through hydraulic motors driving electrical generators to produce electricity. [3]
To access the Pelamis website click here |
Aquamarine Power-OysterThe Power-Oyster is an oscillating wave surge converter designed by Aquamarine Power. These devices are for deployment in shallow waters (10-15m) and are comprised of a buoyant hinged deflector (pictured right) positioned perpendicular to wave-motion which moves back and forth using the horizontal velocity of the waves [2]. These oscillations activate two-way hydraulic rams which pump high pressure sea water (the working fluid) through a pelton turbine onshore.
To access the Aquamarine Power's webiste please click here |
Wave DragonThe 'Wave Dragon' - pictured left - is one example of a Tapchan device. Tapchan means Tapered Channel Wave Power Device and is made of a collector, converter, reservoir and low-head water-turbine. The reflectors each side focus the incident waves which overtop a sloping ramp and fill a reservoir which is higher than the surrounding sea level before being let through the turbine for electricity production [2].
To access the Wave Dragon website please click here |