Page 272 - Fundamentals of Ocean Renewable Energy Generating Electricity From The Sea

260 Fundamentals of Ocean Renewable Energy

FIG. 9.17 (A) Progressive and (B) standing wave systems over a single tidal cycle, where η is
elevation, and u is current. In (A), peak currents coincide with HW and LW. In (B), HW and LW
coincide with slack water.

9.3.3 Combined Tidal Range and Tidal Stream Phasing

For locations that exhibit an energetic tidal stream and tidal range resource,
it is interesting to consider the nature of the tides, as either progressive or
standing wave systems. In a progressive wave, tidal elevations and currents are
in phase with one another (Fig. 9.17A). High water (HW) is typically a time
of standing for a tidal range power plant (Section 3.14), when no electricity
would be generated; whereas this is the time associated with peak tidal streams
in a progressive wave. Therefore, there is scope for phase diversity between tidal
elevations and currents within the same region for a progressive wave system. In
a standing wave system (Fig. 9.17B), peak tidal currents occur mid-way between
HW and LW, at a stage when a tidal lagoon power plant would be at peak
generation (Section 3.14); therefore there is less potential for phase diversity
between currents and elevations in a standing wave system. Unfortunately, due
to resonance (Section 3.5), most promising tidal range sites will be standing
wave systems, hence minimizing the potential for developing combined tidal
range and tidal stream power plants at the same location.

9.4 OPTIMIZATION OF HYBRID MARINE RENEWABLE
ENERGY PROJECTS
There are many advantages in colocating or combining marine renewable energy
power plants at a single location, such as shared grid infrastructure, common