Page 261 - Fundamentals of Ocean Renewable Energy Generating Electricity From The Sea

250 Fundamentals of Ocean Renewable Energy

FIG. 9.8 Effect of energy extraction in a split channel. Change in transport amplitude is measured
in segment 3 (upper constriction). denotes extraction only from segment 3 (upper branch).
denotes equal extraction from segments 3 and 6 (both branches). (Reproduced from B.L. Polagye,
P.C. Malte, Far-field dynamics of tidal energy extraction in channel networks, Renew. Energy 36 (1)
(2011) 222–234, with permission from Elsevier.)

may be neither desirable (e.g. it would preclude the dedicated navigational
channel mentioned earlier) nor attainable (e.g. natural flow asymmetry between
the two channel branches).

9.2.3 WEC Array Optimization

Park Effect
Since a renewable energy converter absorbs energy from its surrounding
environment, the total available resource is reduced for neighbouring energy
converters [20]. For a wave energy converter (WEC) array, the ‘park effect’ Q
can be represented as the ratio of the power of the full array (P tot )tothe sumof
the power for each isolated WEC (P isolated )
P tot
(9.7)
N (isolated)
Q =
j=1 P j
where N is the number of WECs in the array [21]. Although it is theoretically
possible for some WEC array configurations to result in constructive wave
interactions (i.e. Q > 1), in general Q < 1, and array designs tend to focus
on limiting destructive interferences [20]. As the number of devices in a WEC
array increases, the mean power per WEC reduces (Fig. 9.9B); but it is possible