However, we would like to focus our attention on two other more technically advanced concepts. A good idea is probably to show them “in action”, and there is a simple YouTube video clip that explains pretty well how they work. OK, once you have watched the video, we can continue with a more detailed explanation.
One highly interesting type of wave power converter is known as the attenuator. Many of such devices have been already in- stalled in Europe – most R&D work and prototype testing has been done on Pelamis-type attenuators, named after Pelamis Wave Power, a company
which developed them.
The Pelamis-type attenuator has the form of a long “caterpillar”, consist- nig of 4-5 floating segments connected to one another with hinged joints. The length of each segment is approximately equal to one half of the crest-crest distance of the incoming waves. The caterpillar is moored at one end to the ocean bottom, so that it gets aligned perpendicular to the incoming wave crests.
When the waves pass by, the hinged segments form a “broken line shape” approximating the shape of the waveform. The angle between two neigh- boring segments varies thus in an oscillatory manner. This motion is used to drive pistons in two pumps. The pistons move in an alternating fashion, as shown in Fig. 8.10: when the hinged joint moves up, the piston in the lower pump is moving in, and the one in the upper pump is withdrawing. And when the join moves down, this motion pattern is reversed. So, the hydraulic fluid in the pumps is always pushed through the hydraulic motor, one way or another. The hydraulic motor always turns in the same direction, no matter which direction the fluid circulates – and it drives the electric generator.
It will surely be instructive to watch another YouTube clip, illustrating specifically the action of the Pelamis-type attenuators.
And here is yet an- other one, showing not animated graphics, but a real attenuator floating in the waves off the coasts of Portugal.
From the pictures, it’s difficult to get the right idea of what’s the size of a Pelamis-type attenuator. They are really big! The first model, P1, consisting of four sections, is 3.5 meter (12 feet) in diameter, and 120 m (400 ft.) long. It can generate 750 kW of power. The second-generation machine P2 has 5 sections, its 4 m in diameter, and 180 m long, and it weights 1350 tons.