Investor Presentaiton
Energies 2019, 12, 3658
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The PTO system is located on the topside deck and consists of a gearbox and a rotational generator
(Figure 21). The vertical motion of the buoy is transferred through a central rod (heave stem) to
the gearbox. Then, the pulley converts the vertical movement into rotation that is adequate for the
electrical generator. A backstop system unifies the rotation direction using freewheels. This implies
that the buoy can drive the PTO system either upwards or downwards. A solid cylindrical flywheel
is used to amplify the rotational inertia as well as smooth the delivered energy to the generator.
Additionally, the PTO system includes a gearbox that multiplies the rotational speed so that it is
adequate for power generation.
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The location that has been considered for installation of the WEC is near to a small island called
"Ilha Rasa". The location's water depth is about 20 m, and its distance from shore (Copacabana beach,
Rio de Janeiro, Brazil) is about 14 km. The predominant wave climate of the region is a peak period
of Tp
= 9.6 s and a significant height of Hs 1.33 m. Shadman et al. [189] showed that a very large
buoy is required to maximize the power absorption in a region like nearshore Rio de Janeiro, where the
predominate wave periods are beyond 7 s. This might lead to higher costs, which could make the
project economically infeasible. Hence, a specific control called "latching", presented originally by
Budal and Falnes [190], was applied on the WEC to overcome this challenge. Latching is a mechanical
control method that tunes the natural period of the buoy to the predominate wave period of the sea site
by halting and releasing the buoy at its motion extremum. As a result, larger buoy motion amplitude
and velocities can be achieved, leading to higher power production. Eventually, the latching control
enables a smaller buoy with a smaller natural period to be tuned with such a wave climate [191].
A hydraulic system is designed and tested for latching the oscillating buoy.
Backstop
Speed
Multiplier
Flywheel
Generator
Pulley
Buoy
Stem
Figure 21. Schematic view of the power take-off (PTO) system.
Experimental tests of small-scale models, shown in Figure 22, were performed in a wave and
current channel (LOC) at the COPPE/UFRJ. The hydrodynamic behavior of the buoy was studied by
applying different modeling scales including 1:17, 1:20, 1:30, and 1:40. Additionally, a strategy was
developed to investigate the effect of latching control on the WEC.
(a)
(b)
Figure 22. Experimental tests of the COPPE nearshore WEC in a wave channel: (a) 1:17 scaled model,
(b) instruments for data acquisition.View entire presentation