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Power from the Ocean

By: Maria R.

Photo from: Bedding and Beyond


Oceans cover approximately 71% of the earth’s surface, producing over half of the world's oxygen and absorbing carbon dioxide from the atmosphere. Besides all of these capabilities, remarkably they also have the potential to become the largest powerhouse in the world. That is, humankind can use the movement of ocean tides to generate electricity.


Even though the technology for producing electricity from this movement of water is quite recent, over a thousand years ago people in Europe already used to exploit tides to operate grain mills. Tides are the rise and fall of sea levels, which occur as a result of the gravitational force exerted on Earth by the sun and the moon. Coastlines often experience two high tides and two low tides per day. The difference in height between the high tide and the low tide is called the tidal range. This motion can be used to convert kinetic energy into electric power.


Most tidal energy is generated in tidal streams using underwater turbines, which are similar to wind turbines. Essentially, the mechanical energy of tidal currents turns turbines connected to a generator which produces electricity.


Tidal turbines.

Photo from: Energy Central


Another way to generate electricity from tides is through tidal barrages, which arethe most efficient tidal energy sources. A tidal barrage is a dam, similar to the ones in hydroelectric power plants. The dams are built near the sea and capture water during high tides. The water is stored and then released during low tides, going through a turbine that generates electricity.


Tidal barrage system.

Photo from: ResearchGate


All these technologies are still relatively recent and are not widely used yet. There are very few commercial-sized tidal power plants operating in the world. The first project to generate electricity through tides was executed in 1967 in northwestern France. A barrage of 710 meters (approximately 2,329 feet) was built in the Rance River.


The five largest tidal power stations to date are:

  • Sihwa Lake Tidal Power Station, in South Korea

  • La Rance Tidal Power Plant, in France

  • Swansea Bay Tidal Lagoon, in Wales

  • MeyGen Tidal Energy Project, in Scotland

  • Annapolis Royal Generating Station, in Canada


Sihwa Lake Tidal Power Station in South Korea.

Photo from: Using Tidal


There are tidal plants in operation also in China, India, the Philippines, Russia, and the Netherlands. In the United States, there are not any consolidated tidal energy plants yet, but several projects are being developed across the country, including:

  • The Roosevelt Island Tidal Energy (RITE) Project Pilot in the East River of New York

  • The Western Passage Tidal Energy Project in Maine

  • The Cobscook Bay Tidal Energy Project in Maine


The most significant advantage of tidal power is that it is renewable and clean (it does not directly emit any greenhouse gases into the atmosphere). Moreover, tides are one of the most reliable phenomena in the world, thereby being a much more predictable source of renewable energy than the wind or the sun, for instance. Tidal energy can also generate much energy even at low speeds due to the high density of the water. An underwater turbine can generate energy at 2.2mph, while a wind turbine needs 7-9mph to start generating power.


However, tidal energy has some downsides as well. Only a few regions have characteristics propitious to the implementation of this type of energy since the tidal ranges must be greater than 23 feet to generate electricity. The construction of tidal power plants can also negatively impact the environment, even though the energy they produce is environmentally friendly. It can have critical impacts on marine life: fish and other sea creatures can get caught in the turbines, and the barrages can prevent sea life from migrating, causing environmental disruption.


Transitioning from fossil fuels to clean energy is a major step towards mitigating the climate crisis. Tidal power is an up-and-coming alternative to nonrenewable energy, but it alone can not replace fossil fuels. If combined with other clean energy sources, such as solar and wind, it may contribute significantly to achieving a sustainable future.


Discussion Questions:

  • What other countries and regions tidal energy plants could be implemented in?

  • How could we make the construction of tidal energy plants have a minor impact on marine life?


Sources:


National Geographic (n.d.). Tidal energy. Retrieved September 15, 2021, from https://www.nationalgeographic.org/encyclopedia/tidal-energy/.


National Ocean Service (2021, February 26). How frequent are tides? Retrieved September 16, 2021, from https://oceanservice.noaa.gov/facts/tidefrequency.html.


National Ocean Service (2021, February 26). What are tides? Retrieved September 16, 2021, from https://oceanservice.noaa.gov/facts/tides.html.


National Ocean Service (2021, February 26). Why should we care about the ocean? Retrieved September 16, 2021, from https://oceanservice.noaa.gov/facts/why-care-about-ocean.html#:~:text=The%20air%20we%20breathe%3A%20The,our%20climate%20and%20weather%20patterns.


Ovo Energy (2021, January 14). A guide to tidal energy: how does it work, and what are the advantages? Retrieved September 16, 2021, from https://www.ovoenergy.com/guides/energy-guides/tidal-energy-what-it-is-advantages-and-disadvantages.


U.S. Energy Information Administration (2020, September 24). Tidal Power. Retrieved September 16, 2021, from https://www.eia.gov/energyexplained/hydropower/tidal-power.php.



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