harnesses the power of tides using barrages and lagoons. These structures create head differences between water levels, driving to generate electricity. Understanding these systems is crucial for grasping tidal energy's potential.
Tidal barrages and lagoons operate in different modes: ebb, flood, and . Each mode has its pros and cons, affecting efficiency and environmental impact. Mastering these concepts is key to optimizing tidal energy conversion.
Tidal Barrage and Lagoon Systems
Tidal barrage structures
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is a dam-like structure built across a tidal estuary or bay to capture from the tides
Consists of turbines, , embankments, and ship locks
Turbines are located at the base of the barrage to generate electricity as water flows through
Sluice gates are opened to allow water to flow into the basin during high tide and out during low tide, creating a
Ship locks allow vessels to pass through the barrage safely (Panama Canal)
Tidal lagoon systems
Tidal lagoons are similar to tidal barrages but are constructed as self-contained structures along the coastline
Lagoons can be natural or artificial enclosures that fill with water during high tide and release it during low tide
Artificial lagoons are created by building a wall or embankment to enclose a portion of the coastline (Swansea Bay project, UK)
Tidal lagoons have less environmental impact compared to barrages since they do not block the entire estuary or bay
Generating head difference
Head difference refers to the difference in water level between the basin and the sea
Sluice gates are opened during high tide to allow water to flow into the basin, raising the water level inside
During low tide, the sluice gates are closed, creating a head difference between the higher water level in the basin and the lower sea level
The head difference drives the flow of water through the turbines, generating electricity
The greater the head difference, the more potential energy is available for conversion into electrical energy
Tidal Barrage Generation Modes
Ebb generation
mode operates during the outgoing (ebbing) tide
Sluice gates are opened during high tide to fill the basin and closed at the beginning of the ebb tide
Water is released from the basin through the turbines as the tide falls, generating electricity
Ebb generation is the most efficient mode since it utilizes the maximum head difference between the basin and the sea (La Rance Tidal Power Plant, France)
Flood generation
mode operates during the incoming (flooding) tide
Sluice gates are opened during low tide to empty the basin and closed at the beginning of the flood tide
Water flows into the basin through the turbines as the tide rises, generating electricity
Flood generation is less efficient than ebb generation due to the smaller head difference available
Two-way generation
Two-way generation mode combines both ebb and flood generation
Turbines generate electricity during both the incoming and outgoing tides
Sluice gates are used to control the flow of water and optimize the head difference
Two-way generation increases the overall energy output but requires reversible turbines that can operate in both directions (Annapolis Tidal Power Plant, Canada)
Turbine operation modes
Turbines in tidal barrages can operate in different modes depending on the generation scheme
In ebb generation, turbines operate as water flows out of the basin, rotating in a single direction
In flood generation, turbines operate as water flows into the basin, rotating in the opposite direction
Two-way generation requires reversible turbines that can operate efficiently in both directions
Bulb turbines, Straflo turbines, and Kaplan turbines are commonly used in tidal barrages due to their ability to handle large flow rates and low head differences