Harnessing Tidal Energy: Stream, Barrage, Dynamic, and Lagoon Power
Harnessing Tidal Energy
Tidal stream generators (TSGs) utilize the kinetic energy of moving water to power turbines, similar to wind turbines. Some TSGs can be integrated into existing bridge structures, minimizing aesthetic impact. Land constrictions, such as straits or inlets, can create high-velocity sites suitable for turbines. These turbines can be horizontal, vertical, open, or ducted and are typically placed near the bottom of the water column.
Tidal Barrage
Tidal barrages harness the potential energy from the difference in height between high and low tides. Dams strategically placed across tidal estuaries channel the incoming tide into a basin, storing potential energy. As the tide recedes, this energy is converted into mechanical energy by releasing water through turbines, generating electricity. Barrages essentially span the full width of a tidal estuary.
Dynamic Tidal Power
Dynamic tidal power (DTP) is a promising technology that exploits the interaction between potential and kinetic energies in tidal flows. It involves constructing very long dams (30–50 km) from coasts into the sea, without enclosing an area. This creates tidal phase differences across the dam, leading to significant water-level differentials in shallow coastal seas with strong coast-parallel oscillating tidal currents, such as those found in the UK, China, and Korea.
Tidal Lagoon
Tidal lagoons are a newer design option, using circular retaining walls with embedded turbines to capture tidal potential energy. These artificial reservoirs are similar to those of tidal barrages but do not contain a pre-existing ecosystem. Lagoons can be configured in double or triple formats, with or without pumping, to flatten power output. Excess renewable energy from sources like wind or solar can be used for pumping, storing energy for later use. Geographically dispersed tidal lagoons with staggered peak production times can provide near base load production, though at a higher cost than some alternatives. The proposed Tidal Lagoon Swansea Bay in Wales, UK, would be the first tidal power station of this type.