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Figure 2: Example of wave converter based on the overtopping system (OTS) principle,
the Wave Dragon.
Figure 3. Example of wave converter based on the Oscillating water column (OWC)
principle, the Limpet Plant (Wavegen).
fences that stretch across a channel with tidal currents
and have vertical axis turbines, through which
the tidal water is forced to pass, and tidal turbines,
which are solitary units that resemble underwater
wind turbines.
Marine current energy differs from tidal energy in
that it takes advantage of the global ocean currents,
caused primarily by the thermohaline circulation
(one part of the thermohaline circulation is the Gulf
Stream). Ocean currents provide steady sources of
kinetic energy, which can be harvested by underwater
turbine devices, similar to tidal turbines. Since
water is approximately 800 times denser than wind,
energy can be extracted from the ocean even in
areas characterized by low current speeds. Current
energy is still in the research phase, and the
exact dimensions of structures are still unspecified.
Likely sites for tidal and marine current turbines are
expected to be in depths between 20 to 80 m (DTI
2003).
Potential impacts on the marine
environment
First, it is worth noting that tidal barrage systems
have similar environmental impacts as traditional
dams and can lead to significant habitat changes,
sedimentation, marine migration problems, and
changes in estuarine water flow (Pelc & Fujita
2002, Clark 2006, Fraenkel 2006). In the case of La
Range, the aquatic ecosystem was disturbed due
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