Tidal Energy Explained: All You Need to Know

Tidal Energy Explained: All You Need to Know

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Grace Smoot

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Tidal energy is one of the most underused and underexplored renewable energies that promises one of the lowest levels of carbon dioxide emissions. So, we had to ask: What is tidal energy really, and how can it help mitigate climate change?

Tidal energy is the conversion of the movement of ocean water volumes into electrical energy. Per KWh produced, tidal energy emits 22 grams of CO2 on a life-cycle basis. Tidal energy helps combat climate change and has various environmental benefits, however, more research and development is needed.

Keep reading to find out all about what tidal energy is, its global capacity, its carbon footprint, its environmental benefits and drawbacks, and how it can mitigate climate change.

The Big Picture of Tidal Energy

Tidal energy contributes to the avoidance of greenhouse gas (GHG) emissions from the burning of fossil fuels (e.g., coal, oil, natural gas). It is classified as a renewable energy source because the resource (water) naturally replaces itself over time. 

How Is Tidal Energy Defined

Tidal energy is defined as the conversion of the movement of ocean water volumes into electrical energy through the use of various tidal systems.

Tidal Power: power that comes from the movement of the tide (= the rise and fall of the ocean that happens twice every day) and that can be used especially for producing electricity”

Cambridge Dictionary

Tidal energy is potential energy created by tides, height changes in sea level that are caused by the gravitational pull of the sun and moon coupled with the rotation of the earth. Tides are complex, and most major bodies of water also have internal tidal systems. 

What Are the Different Types of Tidal Energy 

There are three types of tidal energy technology:

  • Stream: turbines are placed in tidal streams. The machines are large and can disrupt the tides. The size of the turbine and the location of the tidal stream will dictate the level of environmental impact.
  • Barrage: a barrage (dam) is placed across a river, bay, or estuary. The barrage gates open as the tide rises and close at high tide, creating a lagoon. The water is then released through the turbines which spin a generator to create electricity. Barrages cause significant land disruption within the tidal range, and the change in water and salinity levels within the lagoon can harm plant and animal life. Also, turbines in barrages move fast and can kill marine life in their blades. 
  • Lagoon: a body of ocean water is partially enclosed by a man-made barrier. Lagoons function in the same manner as a barrage, but they generate continuous power and can also be constructed along a coastline. Lagoons provide a minimal level of environmental impact but also generate the least amount of energy. They can be constructed with natural materials like rock and would easily allow marine life to pass through. 
What tidal energy isTidal energy is defined as the conversion of the movement of ocean water volumes into electrical energy through the use of various tidal systems.
What the different types tidal energy areThe three types of tidal energy technology are stream, barrage, and lagoon systems.
How tidal energy worksTidal energy is generated when tidal turbines, barrages, and lagoons use the rise and fall of tides to produce electricity.
The global capacity of tidal energyThere are roughly 3,000 GW of energy stored in the world’s tides. South Korea, France, the United Kingdom, Canada, and Belgium are the top 5 tidal energy-producing countries taking advantage of this large energy-generating potential.
The carbon footprint of tidal energyEstimates for the life-cycle global warming emission of tidal energy are below 22 grams (0.05 pounds) of CO2 equivalent per kWh of electricity produced. 
The environmental benefits of tidal energyTidal energy is a predictable, stable, and concentrated energy source that mitigates climate change, promotes energy independence, and creates jobs.
The environmental drawbacks of tidal energyTidal energy may negatively impact estuarine ecosystems via underwater noise pollution, habitat changes, and wildlife collisions with turbines.
Tidal energy and climate changeTidal energy combats climate change by mitigating the temperature rise, sea-level rise, ice melting, and ocean acidification associated with global warming.

How Does Tidal Energy Work

Tidal energy is generated when tidal turbines, barrages, and lagoons use the rise and fall of tides to produce electricity.

How Does Tidal Energy Actually Produce Energy

Tidal energy operates in the following way:

  • Stream: Moving water turns turbines in tidal streams. The turbines power generators which produce electricity. 
  • Barrage: A dam (dam) is placed across a river, bay, or estuary. As the tide rises, water enters the reservoir. When the water is released it passes through turbines, turning them and powering generators to produce electricity.
  • Lagoon: These operate in the same manner as barrages, but they generate continuous power and can also be constructed along a coastline. 

The electricity is then transported via underwater cables to a substation on land where it is transmitted to consumers by transmission lines. Transformers receive the electricity and either increase or decrease the voltage as needed before it can be delivered to consumers. 

What Is the Global Capacity of Tidal Energy

There are roughly 3,000 GW of energy stored in the world’s tides. South Korea, France, the United Kingdom, Canada, and Belgium are the top 5 tidal energy producing countries taking advantage of this large energy generating potential.

Tidal energy installed capacity has increased over the past 20 years, but its development worldwide has been disproportionate. Europe and Asia have seen far more growth when compared to the rest of the world. 

Our World in Data: Cumulative Installed Marine Energy Capacity, 2000 to 2016

The Sihwa Lake Tidal Power Station in South Korea is the largest operational tidal power plant in the world. Opened in 2011, it has a capacity of 254 MW and a 12.5 kilometer (7.8 foot) sea wall for flood mitigation and agricultural purposes.

The second-largest operational tidal power plant in the world is the La Rance Tidal Power Station in France. Opened in 1966, it consists of 24, 10 MW capacity turbines

Tidal energy is not as developed when compared to the traditional renewable energies (e.g. solar, wind, hydropower, biomass, and geothermal). This is largely due to a lack of funding because of the high upstart and maintenance costs. As technology becomes cheaper to implement, experts predict that tidal energy will increase in production.

The marine (wave and tidal) energy market size is predicted to reach $28 billion by 2030, increasing at a compound annual growth rate of nearly 42%. Because the market potential for tidal energy is so high, it is important to understand what tidal’s carbon footprint is, and how its carbon emissions affect the global climate change process.

What Is the Carbon Footprint of Tidal Energy

The carbon footprint is one of the ways we measure the effects of human-induced global climate change. It primarily focuses on the greenhouse gas (GHG) emissions associated with consumption and includes other emissions such as methane (CH4), nitrous oxide, and chlorofluorocarbons (CFCs).

Carbon footprint: the amount of greenhouse gasses and specifically carbon dioxide emitted by something (such as a person’s activities or a product’s manufacture and transport) during a given period

Merriam Webster

Basically, it is the amount of carbon emitted by an activity or an organization. This includes GHG emissions from fuel that we burn directly (e.g., heating a home, driving a car) and GHG emissions from manufacturing the products that we use (e.g., power plants, factories, and landfills). 

Estimates for the life-cycle global warming emission of tidal energy are below 22 grams (0.05 pounds) of CO2 equivalent per kWh of electricity produced. 

Have a look at the illustration below to see the average life-cycle CO2 equivalent emissions of different energy sources. Tidal energy produces 0.03% of the CO2 emissions per unit of electricity than coal produces (820 gCO2 per KWh)

Illustration of CO2 equivalent per energy source
World Nuclear Association: Average life-cycle CO2 equivalent emissions

When discussing the carbon footprint of tidal energy, we must take into account carbon emissions across the energy’s building, operating, and building back phases.

The life-cycle stages of tidal energyEach stage’s carbon footprint
Building of tidal energyCO2 emissions from construction and transportation of materials
Operating of tidal energyLittle to no CO2 emissions or waste products
Building back of tidal energyTheoretically none as tidal infrastructure can be maintained indefinitely

There are very few CO2 emissions or waste products associated with operating tidal energy, making the carbon footprint of this phase very low. CO2 emissions at this stage are associated with the operation of the mechanical equipment (e.g., turbines, generators, substations, transformers). 

Tidal power plants have an average life expectancy of up to 100 years. This makes them a long-term, reliable source of energy. And if tidal plants are properly maintained, the civil engineering infrastructure should last almost indefinitely

Tidal energy is a low-carbon emitting energy source with a large energy generation potential, therefore it is important to understand what its carbon footprint is and how its carbon emissions affect the global climate change process.

Related: Are you interested in more about the carbon footprint of tidal energy? Check it out in this article here: “What Is the Carbon Footprint of Tidal and Wave Energy?

How Environmentally Friendly Is Tidal Energy

The environmental impacts of tidal energy come down to its effect on the marine ecosystem in which it is constructed.  

Environmentally friendly: (of products) not harming the environment.”

Cambridge Dictionary

Although it is not nearly as developed as other renewable energies, tidal energy comes with a host of environmental benefits and only minimal drawbacks. 

What Are the Environmental Benefits of Tidal Energy

Tidal energy has the following environmental benefits: 

  • Climate change mitigation: Tidal energy can help reduce global CO2 emissions from fossil fuel electricity generation. This reduction in CO2 emissions, in turn, reduces the effects of global climate change including increasing temperatures, rising sea levels, melting of sea ice, changing precipitation patterns, and ocean acidification.
  • A predictable, stable, and concentrated energy source: Unlike other renewable energies (solar and wind), marine energy is available for use 24/7, 365 days a year. Water contains approximately 1,000 times the kinetic energy of wind, so tides can produce the same amount of energy with less material and in a fraction of the space required by other renewable energies. 
  • Energy independence: Being able to produce our own electricity in the U.S. without the aid of foreign countries is an important step to help us become more self-sufficient. Former President George W. Bush signed the Energy Independence and Security Act of 2007 to reduce U.S. dependence on oil, expand the production of renewable fuels (and confront global climate change). 
  • Employment opportunities: The renewable energy sector collectively employed 12 million people worldwide in 2020. Renewable energy jobs continue to increase as we start to realize just how beneficial renewable energy is for our environment. 

Tidal energy helps mitigate climate change through reduced CO2 emissions while promoting energy independence and creating jobs. 

What Are the Environmental Drawbacks of Tidal Energy

The main environmental concern with tidal energy is the impact on aquatic wildlife. Construction and operation of marine energy technology may negatively impact estuarine ecosystems via underwater noise pollution, habitat changes, and wildlife collisions with turbines. Because tidal energy is a relatively new technology, more research needs to be done to fully understand this environmental impact. 

Why Is Tidal Energy Important to Fight Climate Change

Climate change is arguably the most severe, long-term, global impact of fossil fuel combustion. Every year, approximately 33 bt of CO2 are emitted from burning fossil fuels. The carbon found in fossil fuels reacts with oxygen in the air to produce CO2. This warms the earth by acting as a heating blanket, and a warmer earth comes with a host of negative side effects. 

Marine energy (tidal + wave energy) could help reduce global CO2 emissions from fossil fuel electricity generation by around 500 million tons by the year 2050. Using tidal energy instead of fossil fuel energy helps mitigate the following negative effects of climate change:

  • Melting of sea ice: Since 1979, arctic sea ice has declined by 30%. Sea ice plays a major role in regulating the earth’s climate by reflecting sunlight into space and providing habitat for animal species. If all of the glaciers on Earth melted, sea levels would rise by approximately 70 feet, effectively flooding out every coastal city on the planet. 
  • Changing precipitation patterns: Extreme weather events (e.g., hurricanes, floods, droughts) are becoming more common and more intense. Storm-affected areas will experience increased precipitation and flooding whereas areas located further from storm tracks will experience decreased precipitation and droughts.
  • Ocean acidification: The ocean absorbs 30% of the CO2 released into the atmosphere, which decreases the pH (increases the acidity) of the ocean. In the past 200 years, the pH of oceans has decreased by 0.1 pH units, which translates to a 30% increase in acidity. Aquatic life unable to adjust to this rapid acidification will die off. A prime example of this is coral bleaching, where coral expel the algae (zooxanthellae) living in their tissues as a result of changes in temperature, light, or nutrients. 

The more we reduce CO2 emissions, the more we slow the rate of temperature rise, sea-level rise, ice melting, and ocean acidification. When these rates are slowed, the earth’s biodiversity does not have to struggle to adapt to temperature and pH changes. People will not be displaced due to the flooding of coastal areas. And icebergs will continue to provide climate regulation. 

To help keep global temperature rise below 1.5C, as outlined in the Paris Agreement, we must shift at least 80% of our electricity generation to low carbon sources. Over 120 countries have already stated their net-zero carbon emissions ambitions for 2050 or 2060. But only 12 countries have thus far proposed or enacted any legislation, indicating that there is more work to be done.

Final Thoughts

Tidal energy harnesses the kinetic energy stored in the Earth’s tides and converts it into electrical energy. It is a renewable energy source with a low carbon footprint across its building, operating, and building back phases. 

Although it is not as developed as other renewable energies, tidal energy still has great potential to help mitigate climate change. Further research and development is needed to enhance the technology and explore possible adverse effects of tidal systems on marine life. But overall, tidal energy benefits both our atmosphere and Earth’s biota.

Stay impactful,

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Grace Smoot

Grace loves to research and write about all things related to climate action and sustainability. She holds a Bachelor’s of Science degree in Environmental Biology and works as an Environmental Survey Technician. Outside of work, she loves to work out, play soccer, and take her dog for long walks.

Did you know that the internet is a huge polluter of the environment? But fortunately not this site. This site is powered by renewable energy and all hosting-related CO2 emissions are offset by three times as many renewable energy certificates. Find out all about it here.

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