What is it?
The motion of large bodies of water can be used to turn mechanical devices to produce electricity. Tidal energy exploits the natural ebb and flow of coastal tidal waters caused principally by the interaction of the gravitational fields of the earth, moon and sun.
How does it work?
Tidal power falls into 3 main categories:
- Tidal Stream generators: make use of the kinetic energy of moving water to power turbines, in a similar way to wind turbines use moving air. This method is becoming more popular because of the lower cost and ecological impact compare to tidal barrages.
- Tidal barrage: make use of the potential energy in the difference in height (head) between high and low tides (in a similar way to hydro electric power plants). Barrages are essentially dams across the full width of an estuary. They are very costly, there is a shortage of appropriate sites worldwide, and have an impact on the ecology of the estuary.
- Dynamic tidal power: exploits both the kinetic energy of moving water and the potential energy of the difference in water levels. Very long dams are built from coasts straight out into the sea or ocean without enclosing an area.
Is it suitable?
Schemes are costly and may take years to construct. No power can be generated until they are complete, hence long payback periods.
Putting barriers into waterways, particularly highly diverse estuaries (often the most feasible for tidal power sites) can have adverse effects on natural habitats, impacting on sedimentation and erosion, water flow, salinity and overall water quality.
Some of the ideal sites for tidal power generation are not located in areas where electricity demand is high.
What are the benefits?
- Unlike wind or solar power production using tidal forces is constant as it is less vulnerable to weather or seasonal variations.
- No waste is produced.
- Basically it needs no fuel to operate.
- Tides are more predictable than wind or solar power.
- Long-term operating and overhead costs are very low compared to conventional energy sources.
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