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254 Fundamentals of Ocean Renewable Energy

FIG. 9.11 (A) Total power output and (B) power variance for the four global WEC geometries
shown in Fig. 9.10. (Reproduced from M. Göteman, J. Engström, M. Eriksson, J. Isberg, Optimizing
wave energy parks with over 1000 interacting point-absorbers using an approximate analytical
method, Int. J. Mar. Energy 10 (2015) 113–126, with permission from Elsevier.)

Device Spacing
The spacing between individual devices within a WEC array has been shown to
influence variance in power output. As summarized by Göteman et al. [21], a
2
3 × 3 square wave array covering an area of 400 m (10 m device spacing) has
2
considerably lower variance than an array that covers 1600 m (20 m device
spacing). A relatively closely spaced WEC array, provided the ‘park effect’
is minimized, will have the added advantage of lower cabling costs, that is
similar to cabling issues associated with the longitudinal and lateral spacing
of tidal energy devices (Section 9.2.2). In a further study of a 3 × 3arrayof
point absorbers, Göteman et al. [25] found a localized peak in power variance
associated with 18 m device spacing. Although this exact value is unique to
this particular device, it demonstrates that careful design is required to avoid
nonoptimal device spacings.

Size of WECs in an Array
One final issue in WEC array optimization is the size of individual devices
within an array. Consider Fig. 9.10, for example, where larger WEC devices
would be more suited to the ‘front’ of the array, and smaller devices to the
‘rear’. Blending WEC sizes within an array can lead to higher power output for
the array [21] and, it could be assumed, lead to more efficient use of each WEC
within the array. Indeed, a concert of wave energy devices within a single array,
each exploiting different parts of the wave energy spectrum, could be achieved,
but only as a result of detailed knowledge of the wave climate, and extensive
optimization.