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Introduction

The tides contain energy that can be harnessed to produce electricity. Two types of tidal energy can be extracted. Kinetic energy can be harnessed from the ebbing and surging tides. Potential energy can be harnessed from differences in the high and low tides. Using tidal currents remains the primary method of generating electricity.

What is Tidal Energy?

Tidal energy is the utilization of the variations in sea level caused primarily by the gravitational effects of the moon, combined with the rotation of the Earth.

Types of Tidal Plants

Tidal Fences: Tidal fences block a channel, forcing water to go through it and turning its turbines to generate electricity.
Barrage Tidal Plants: Barrage tidal plants are the most common type of tidal plant. A dam or barrage is installed, usually where there is a narrow water channel, with gates and turbines at certain points. As water flow through the turbines, they turn a generator that produces electricity.
Tidal Turbines: Tidal turbines work like an underwater wind turbine, using the tides to turn blades and generate electricity.

How Barrage Tidal Plants Work

There are 3 main parts to a barrage tidal plant. These include:

Barrage: the barrage acts much like a dam, holding back water to be later released.
Sluice Gates: the sluice gates allow water to flow through the turbine.
Turbine: the turbine spins as the water flows through it, which in turn rotates an electricity-producing generator.

When the tide falls, water behind the barrage is held in the estuary. The water is then released, flowing seaward turning a turbine and generator, which creates electricity. Later, when the tide rises, it will be held back in the barrage and then released back into the estuary, flowing through another turbine and allowing the electricity-producing process to be repeated.

Click here to see a tidal power animation

Tidal Power Advantages and Disadvantages
Advantages
Disadvantages
  • Does not generate emmissions or wastes
  • Uses an abundant, inexpensive fuel source (water) to generate power
  • Electricity is reliably generated (tides are predictable)
  • May protect coastline against damage from high storm tides and provide a ready-made road bridge
  • Expensive to construct
  • Power is often generated when there is little demand for electricity
  • Limited construction locations
  • Barrages may block outlets to open water. Although locks can be installed, this is often a slow and expensive process.
  • Barrages affect fish migration and other wildlife- many fish like salmon swim up to the barrages and are killed by the spinning turbines. Fish ladders may be used to allow passage for the fish, but these are never 100% effective. Barrages may also destroy the habitat of the wildlife living near it
  • Barrages may affect the tidal level - the change in tidal level may affect navigation, recreation, cause flooding of the shoreline and affect local marine life

Summary

Tidal energy is a clean, renewable energy resource, but its environmental impacts and accessibility, limit its potential to become a major provider of electricity. Where tidal energy is a viable resource, it may prove to be expensive at first, but economical in the long run if the technology improves.

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