Page 271 - Fundamentals of Ocean Renewable Energy Generating Electricity From The Sea

Optimization Chapter | 9 259

FIG. 9.16 Electricity generation from five barrages in the Irish Sea during spring tides. (Repro-
duced from N. Yates, I. Walkington, R. Burrows, J. Wolf, Appraising the extractable tidal energy
resource of the UK’s western coastal waters, Philos. Trans. R. Soc. A 371 (1985) (2013) 20120181,
with permission from the Royal Society.)

another, whereas a Severn barrage in the southern Irish Sea is approximately 180
degrees out of phase (Fig. 9.16). This is perhaps not surprising if we examine
the M2 cotidal chart of the region (Fig. 9.12). Because the northern part of the
Irish Sea is a standing wave system (Section 3.4), there are few cotidal lines in
this region (cotidal lines are all 300–360 degrees in Fig. 9.12), indicating that
tidal elevations throughout this region are more or less in phase. The cotidal
lines in the Severn Estuary have a phase of around 180 degrees in Fig. 9.12,
explaining the 180 degrees change in power output between power plants in
the southern and northern Irish Sea (Fig. 9.16). However, further optimization
(flood-only, ebb-only, and dual model) could be performed on this set of tidal
barrages to further smooth power output. Similar optimization could also be
performed on multiple tidal lagoon power plants, as considered, in part, by
Angeloudis and Falconer [32], who optimized annual electricity production
for the Bristol Channel and Severn Estuary. Although they did not optimize
to minimize variability of power output, they advise that multiple projects
should also consider the environmental consequences of changing the mode of
operation; for example, flood-only and ebb-only operation may lead to greater
loss of intertidal area and far-field effects, compared with dual-model operation.