What is a tidal barrage?
A tidal barrage is a dam built across an estuary or tidal inlet. It uses the rise and fall of tides to produce electricity by letting seawater move through turbines.
How does it generate electricity?
- Build across an estuary with large walls, gates, and turbines inside the dam. The barrier holds back sea water and creates a gap that can be controlled.
- During high tide water from the sea flows into the basin behind the barrage through controlled gates. The water level on the sea side is higher, so water starts to pile up behind the barrier.
- Trapping water Gates can close to trap water in the basin. This creates a head, which is the height difference between the sea and the water behind the dam.
- Release through turbines as the tide goes out (ebb). The stored water is released back to the sea through turbines, turning them and generating electricity.
- Optional variations some designs let water pass through turbines during both flood and ebb with special reversible turbines. The exact timing depends on the plant.
Why is it useful and what are the challenges?
- Pros: predictable power from a renewable source, helps with energy supply, and can meet high, steady demand when tides are strong.
- Cons: large construction cost, environmental impact on habitats and fisheries, and limited locations with big enough tides.
Examples and quick notes
One famous example is the La Rance barrage in France. Tidal barrages require careful planning to balance energy needs with ecosystems and navigation.