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Water for Energy and Fuel Production
FiGUre 13.3 (See color insert.) WaveRoller wave energy farm installation in Peniche,
Portugal. (Adapted from “Wave power,” Wikipedia, the free encyclopedia, 2013.)
oscillating water column described in Figure 13.2a. This device has been in operation
in Finland since 1994.
Yet another type of machine looks like a giant sea snake (or a farm of snakes)
with floating pontoons that heave and sway on the ocean surface, driving hydraulic
pumps to power an electric generator [64,81–89]. This Pelamis “snake,” an offshore
machine, consist of five tube sections that float on the surface and use the motion of
the waves to generate electricity [60,64,81]. They use the principle of attenuator WEC
(Figure 13.2c) described above. When the tube sections flex, hydraulic arms move in
opposite directions and turn a generator that produces power. The amount of power
required will dictate the number of such snakes in a given farm and to some extent the
length of each snake (that can be as long as 600 ft). This device is also anchored to the
seabed and must withstand marine environments. Waves powerful enough to drive
these generators are often found off coasts with large oceans to their west (providing
long wind fetch) and strong prevailing winds such as the west coasts of the United
States, Chile, Australia, and in the North Sea among many others [46–60]. This technology is graphically illustrated in Reference [35] and extensively described in the
Pelamis wave power website enquiries@pelamiswave.com. The snakes are being
commercially used off the shores in Portugal and Scotland [35,64,81–90].
Finally, one device that uses the above-described “overtopping” principle
(Figure  13.2b) is “Wave Dragon” (shown in Figure 13.4), which is being used in
Denmark since 2003.
13.3.3.3 rotating hydrokinetic devices
The kinetic energy of flowing tidal stream, ocean current, or river can also be
captured by the rotating device [47–60] shown in Figures 13.5 [50]. Such a device
is generally installed underwater to harness maximum energy from the currents.