Tidal Energy: Definition, Concepts, and Facts You Should Know

Oceans make up around 70 percent of the Earth’s surface, so why are we not using their energy more? The future of power and electricity generation come with great potential for tidal energy exactly because the massive size of our oceans. Today we learn more about tidal energy and power and what is required to harness the fascinating movement of the water.

The tides are the direct result of the moon’s gravitational pull – and the sun’s. Combined with Earth’s rotation, this pull causes the water altitudes near the coasts to fluctuate up to 30-40 ft. People have been exploiting the tides to run grain mills for over 1,000 years, especially on the shores of Europe. Today, we’ve developed great tidal energy facilities capable of generating electricity. But how do they work, exactly?

La Rance tidal power plant in France

La Rance tidal power plant in France / Credit

What Is Tidal Energy?

Tidal energy is a type of hydropower that transforms the movement of the tides into electricity or other practical forms of power. The tide, created by the gravitational sun and moon’s effect on the planet, causes seasonal movement of the oceans and the seas. Therefore, tidal energy is a predictable form of renewable energy, which gives regular cycles of power generation. It can be utilized in two forms:

  • Tidal Range

Tidal range is the difference in height between the high tide and the following low tide. The construction of artificial tidal lagoons or barrages may help capture the tide. Setting up turbines in the lagoon or barrier harnesses the power of the tide flooding the reservoir, thus generating electricity. Once the tide outside the barrier retreats, the retained water can exit the reservoir through the turbines once again, generating more electricity.

  • Tidal Stream

Tidal stream refers to the flow of water caused by the ebb of the tide, and it reveals itself in the form of tidal current. Devices designed to harness tidal stream obtain energy from the kinetic flow of water. The process is similar to those of wind turbines extracting energy from the air movement.

The sea currents created by tidal movement are often heightened around headlands or in places where water flows forcefully through narrow pathways. The tidal stream is particularly high in a number of locations around the British coastline, which has prompted the local industry to lead early technology developments. The UK is a prominent player in the field, successfully exploring the prospect of exploiting tidal energy.

RELATED: [Indian Government to Offer Tidal Energy Support Soon]

Tidal Barrages

The barrage is one of the most popular tidal energy systems. A framework comparable to a dam, the barrage usually occupies the inlet of a lagoon or ocean bay that makes up the tidal reservoir. The water heights and the flow rates are controlled with the help of sluice gates on the barrage. This way, the tidal pool fills with the entering high tide and empties via an electric turbine structure with the exiting low tide. The most efficient type of system is a tidal power arrangement that goes both ways, as it produces electricity during the incoming and the outgoing tide.

Tidal power comes with plenty of advantages – not the least of which is its renewable nature – but it has potential disadvantages, too. For instance, a tidal facility may have negative effects on the ecosystems in the proximity of the tidal reservoir. Tidal barrages, in particular, can influence the tidal levels in the basin, as well as increase the water’s turbidity (which represents the cloudiness of the water). These systems also affect recreation and navigation in the area.

There are multiple tidal energy barrages around the globe. The South Korean Sihwa Lake Tidal Power Station holds the title for the greatest electricity production capacity (254 Megawatts). Meanwhile, La Rance, France, is home to the first operating tidal power station, featuring around 240 Megawatts of electricity production capacity.

Other countries have smaller tidal power facilities, including China and Russia. Because there are almost no appropriate sites to produce tidal energy economically, the U.S. has zero tidal power plants at the moment. On the other hand, Canada, France, and England, as well as Russia, have more untapped capacity to harness the power of the tides.

Tidal Turbines

Firstly, these are much like wind turbines in appearance. If installed on sea beds where the dial flow is the strongest, tidal turbines are most efficient. Because the water’s density surpasses the air’s by approximately 800 times, tidal turbines must be much heavier and more robust than wind mills. While tidal turbines cost more to erect than wind mills, the also generate more energy.

Scottish Strangford Lough and South Korean Uldolmok are two of the most powerful tidal stations in the world. Both of them boast 1.5 MW tidal turbines. Plans are under development for a tidal power plant in New York, on the East River. Also, another project in northern Scotland plans to open a tidal station to sustain around 400 MW of electricity production capacity.

Tidal Fences

Similar to tidal turbines, tidal fences use vertical axis turbines anchored in a row or fence and placed on sea beds. This type of tidal power system allows water to pass through the rotary engines, which in turn generates electricity. In spite of the practicality of the tidal fences, there are no projects operating since the start of 2017.

Facts about Tidal Energy

  • Tidal energy is one of the oldest types of energy known to man (harnessed since circa 787 A.D.)
  • Undersea currents power tidal turbines and barrages for the production of energy.
  • This form of energy is influenced by location, and speed and volume of the currents. Therefore, a limited places in the world can produce it.
  • Tidal turbines may have a negative effect on wildlife habitats. Unfortunately, they lead to the displacement and alteration of ecosystems.
  • The speed of the tides is unencumbered; man has no control over it, which can sometimes be inconvenient.
  • The generation of electricity via tidal energy causes on side products such as pollutants or greenhouse gases.
  • A seashore must meet specific criteria to host a tidal power station. One of those criteria is having a tidal range of over 7 meters. Also, tidal power can be controlled for no longer than 10 hours each day.
  • The expansion of tidal power is rather slow because the cost of building a tidal power station is very high (upwards of $1.3 million per MW).

Header Image: cdn.com

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Rick Carlstrom
 

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