Tidal Power: Using the Ebb and Flow of the Tides to Generate Energy

Although some people are calling tidal power the future of electricity production, the use of tidal power dates back to about 900 AD when early civilizations constructed tide mills. These mills used the force of the tide to turn a waterwheel, which in turn was used to grind grain into flour 1.

Ocean tides are created from the gravitational pull of the moon and the rotation of the earth, causing the tides to ebb and flow twice a day. Only certain areas in the world are economically viable locations to harness the power of the tides. That’s because the difference between the high tide and low tide must be more than 16 feet to harness tidal enough power needed to produce electricity 2.

Tidal power is generated by using up to three different methods.

  1. Building a barrage. A barrage is essential the same concept as building a dam and must be built across a tidal estuary that allows the water to fill a tidal basin. Once the basin in full, it is then closed off, and, as the tide goes out on the other side of the basin, the gates are open and the water flows through underwater turbines causing them to spin and produces electricity.
  2. Installing a tidal fence. A tidal fence can be used to harness energy of tidal currents that are much slower than what is needed to turn a tidal turbine. They act as giant underwater turnstiles that turn from the force of the currents much like a wind turbine. However, because water has a much higher density (about 800 times more), tidal fences can generate more energy than wind power can.
  3. Creating Tidal Turbine Farms. Just like wind farms, tidal turbine farms produce electricity when they turn. Tidal turbines are installed underwater in depths about 90 feet and can be located anywhere there is a strong enough tidal flow that can turn the turbines.

Tidal Barrage
Tidal Barrage

While most current tidal electricity generation today employs the barrage technique, the costs for building such a structure are extremely high and can have a negative impact on the environment. Building a tidal dam has the same negative effects that damming a river can have on the environment. It can block fish migration and cause excess silt to build up, which affects the ocean ecosystem 3.

The current trend, however, is heading toward installing more tidal turbine farms and tidal fences throughout the world, which have much less of an impact on the environment.

Tidal Power Plants at Work

Today, the United States does not have a tidal power plant, although development is underway to pursue using this powerful energy source. There are actually plans to install 875 turbines in the Niagara River 4. Areas along the Pacific Northwest and the Atlantic Northeast have also been identified as potential sites for tidal power because of the optimum tide conditions.

Rance Tidal Plant
Rance Tidal Plant

Currently there are two commercial tidal power plants in operation in the world. The first and largest was installed in 1966 in La Rance, France and is a 240 megawatt plant. The second is a much smaller facility, only 20 megawatts, in Annapolis Royal in Nova Scotia 5.

Potential sites have been identified throughout the world as locations that have fast enough currents that can feasibly harness tidal energy. Some of those locations include: Bay of Fundy in Canada, the East River in New York City, Pembrokeshire in Wales, Cook Strait in New Zealand, Golden Gate in the San Francisco Bay, and the Piscataqua River in New Hampshire 6.

The Benefits of Tidal Power

One of the most important and highly significant benefits of using the power of the tides is that there are no fuel costs. The energy is fueled by the reliable and sustainable force of the ocean. Although initial construction costs are high, the overall maintenance of the equipment and the return of power in the form of electricity can help offset this expense.

Tidal power is also an emission free source of power, providing clean energy by harnessing this natural resource. It can be used to displace other electricity-producing methods that rely on the burning of fossil fuels. Burning fossil fuels like coal, contribute to the greenhouse effect because they release poisons into the atmosphere like carbon dioxide. Sulfur is also a result of burning fossil fuels and contributes to the cause of acid rain in our environment.

Tidal power can also provide secondary benefits because transportation corridors can be built above the tidal generators. These can support roadways, water mains, rail lines, or communication lines, which again can offset the expense of installing the tidal equipment 7.

And, unlike renewable resources such as wind power, the ebb and flow of the ocean tides are entirely predictable and consistent and aren’t affected by outside forces such as the weather.


There is also minimum impact on the surrounding communities. Complaints have been made about how people think that wind farm turbines decrease the value of the nearby properties. Because the tidal turbines are completely submerged underwater, they won’t have an effect on the aesthetics of the community.

Tidal Power: A Necessary Resource in Today’s Energy Demands

Even today, it’s tough to meet the rising demands of energy throughout the world. There are still developing countries that are without electricity, an estimated 2 billion people. In the next 20 years, most of the demand will probably come from these developing countries in Asia, which contains about half of the world’s population. Even in the United States, we’ve encountered rolling blackouts of power, when there just wasn’t enough energy in the power grid to meet the demands of certain areas of the country.

Tidal power has the ability to help meet these rising demands, and in conjunction with alternative forms of renewable energy such as biomass, wind, and solar energies, can provide the world with a renewable, clean source of energy that won’t negatively impact the world we live in.

1. Tidal Electric. History of Tidal Power. http://www.tidalelectric.com/History.htm

2. US Department of Energy. Ocean Tidal Power. http://www.energysavers.gov/renewable_energy/ocean/index.cfm/mytopic=50008

3. Energy Consumers Edge. Pros and Cons of Tidal Energy Use. http://www.energy-consumers-edge.com/tidal_energy_use.html

4. Alternative Energy. Clean Energy from Flowing Waters. http://www.alternative-energy-news.info/clean-energy-flowing-waters/

5. Interesting Energy Facts. Tidal Power Facts. http://interestingenergyfacts.blogspot.com/2008/04/tidal-power-tidal-energy-facts.html

6. Wikipedia. Tidal Power. http://en.wikipedia.org/wiki/Tidal_power

7. Blue Energy. Green Energy Wins in a Recession. http://www.bluenergy.com/economic.html

4 Responses to “Tidal Power: Using the Ebb and Flow of the Tides to Generate Energy”

  1. kelly says:

    WOW!!!!!!! This fascinating and very very awesome it really help me with my project

  2. kelly says:

    NotIt sucked so much that i din’t really learn anything

  3. kelly says:

    Sad but very true

  4. Paul Tyler says:

    If electrical power generation turbines were installed in rivers, then the power generation would be continuous.
    Tidal power generation is equally important, but power generation in rivers has decided advantages.
    Equipment and machinery installed in oceans is difficult to control, the water is corrosive, and unusual weather presents more severe obstacles than rivers. The mathematics involved in designing river power generation would not have to account for as wide an amount of safety factors. Also, power generation in rivers can be located far inland, or almost any location within an area provided there is sufficient river current.
    Good luck.
    Paul Tyler, 17 Wood Lane, Maynard, MA 01754
    Tele: (978) 897-1901

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