5.1 Tidal Range Energy Conversion Concepts

Tidal range energy harnesses the power of tides using barrages and lagoons. These structures create head differences between water levels, driving turbines 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 two-way generation. 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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  Cardiff Bay Barrage, Sluice Gates © Colin Smith :: Geograph Britain and Ireland View original

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  Tidal power - Wikipedia View original

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  Cardiff Bay Barrage, Sluice Gates © Colin Smith :: Geograph Britain and Ireland View original

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Top images from around the web for Tidal barrage structures

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  Cardiff Bay Barrage, Sluice Gates © Colin Smith :: Geograph Britain and Ireland View original

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• 

  ESSD - Measurements of hydrodynamics, sediment, morphology and benthos on Ameland ebb-tidal ... View original

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• 

  Tidal power - Wikipedia View original

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  Cardiff Bay Barrage, Sluice Gates © Colin Smith :: Geograph Britain and Ireland View original

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  ESSD - Measurements of hydrodynamics, sediment, morphology and benthos on Ameland ebb-tidal ... View original

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• Tidal barrage is a dam-like structure built across a tidal estuary or bay to capture potential energy from the tides
• Consists of turbines, sluice gates, 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 head difference
• 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 Tidal Lagoon 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

• 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

• 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