Tidal power facts for kids
Tidal power or tidal energy is a way to create electricity using the natural movement of ocean tides. It turns the energy from tides into useful power.
Even though it's not used everywhere yet, tidal energy could be a big source of electricity generation in the future. Tides are very reliable and predictable, unlike wind or sunlight. In the past, tidal energy was expensive. It also needed special places with very high tides or strong water currents.
But now, new technologies and designs are making tidal power better. Things like dynamic tidal power and tidal lagoons are helping. New types of turbines are also improving how we capture this energy. This means tidal power might be more available and cheaper than we thought.
People have used tides for power for a long time. In Europe and North America, there were "tide mills" in the Middle Ages and even Roman times. These mills used incoming water stored in ponds. As the tide went out, the water turned waterwheels to grind grain. In the 1800s, people started using falling water and spinning turbines to make electricity.
Making electricity from ocean technologies grew by about 16% in 2018 and 13% in 2019. More research is needed to make it even cheaper and more common. The first big tidal power plant was the Rance Tidal Power Station in France, which started in 1966. It was the largest until the Sihwa Lake Tidal Power Station opened in South Korea in 2011. The Sihwa station uses sea walls and 10 turbines to make 254 megawatts of power.
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Tidal Power: Energy from the Ocean's Tides
Tidal energy comes from the ocean's tides. Tidal forces are caused by the pull of gravity from the Moon and Sun. These forces make the ocean water move, creating currents. This causes the sea level to change regularly as the Earth spins. These changes are very steady and easy to predict. This is because the Earth's spin and the Moon's orbit are very consistent.
The strength of these movements depends on the positions of the Moon and Sun. It also depends on the Earth's rotation and the shape of the ocean floor and coastlines.
Tidal power is special because it uses energy from the Earth-Moon system. Most other natural energies, like fossil fuels, hydroelectric, wind, and solar energy, come from the Sun. Nuclear energy uses special elements from Earth. Geothermal power uses heat from inside the Earth.
A tidal generator turns the energy of moving tides into electricity. The bigger the tide changes and the faster the currents, the more electricity a site can make. Tidal energy is very reliable and has a lot of power in a small space. It also lasts a long time.
Because tides are caused by the Moon and Sun's gravity and Earth's spin, tidal power will practically never run out. It is a renewable energy source. The movement of tides causes a tiny loss of energy in the Earth-Moon system. This happens as water moves through tight spots along coastlines. This energy loss has made the Earth spin slower over billions of years. But using tidal power will take only a tiny bit more energy from the system. We won't notice any difference in the future.
Different Ways to Get Tidal Power
There are four main ways to generate power from tides:
Tidal Stream Generators
Tidal stream generators use the kinetic energy (energy of motion) of moving water. They work like wind turbines, but in water instead of air. Some tidal generators can be built into bridges or placed completely underwater. This means they don't spoil the view. Narrow places like straits or inlets can create very fast currents. Turbines can capture this energy. These turbines can be horizontal, vertical, open, or covered.
Tidal Barrages
Tidal barrages use the potential energy (stored energy) from the height difference between high and low tides. To make power, special dams are built across a tidal estuary. When the sea level rises, the incoming tide flows into a large basin behind the dam. This water holds a lot of potential energy. As the tide goes out, this stored energy is released. The water flows through large turbines, which spin generators to create electricity. Barrages are basically dams that block the whole width of a tidal area.
Tidal Lagoons
A newer way to get tidal energy is to build round walls in the sea. These walls have turbines inside them. The areas created are like the basins behind tidal barrages. But these "lagoons" are artificial and don't disturb existing natural areas.
These lagoons can even be built in pairs or triples. This can help make the power output more steady. If there's too much wind or solar power, that extra energy can be used to pump water into the lagoons. This stores the energy for later when it's needed.
Dynamic Tidal Power
Dynamic tidal power (DTP) is a new idea that uses both potential and kinetic energy from tides. It suggests building very long dams (about 30–50 km long) straight out from the coast into the sea. These dams would not enclose an area. They would create different tide levels along the dam. This works best in shallow coastal areas with strong currents that flow along the coast, like in the UK, China, and Korea.
History of Tidal Power
The first big studies of tidal power plants in the 1900s were done by the US Federal Power Commission in 1924. They looked at building plants in the border area between Maine (USA) and New Brunswick (Canada). These plants would have used the Bay of Fundy and Passamaquoddy Bay. But nothing was built from this study.
In 1956, a power company in Halifax, Canada, studied building tidal power in the Bay of Fundy. They found that a lot of power could be made, but it would be too expensive.
Later, in 1961, both the US and Canadian governments looked at the Passamaquoddy Tidal Power Project again. It seemed good for the US but not for Canada.
Another study in 1977 looked at building tidal barrages in the Bay of Fundy. Three sites seemed possible: Shepody Bay (1550 MW), Cumberland Basin (1085 MW), and Cobequid Bay (3800 MW). Even though they seemed possible, they were never built.
In the 2000s, a public power company in Washington State, USA, started a tidal energy project in 2007. They planned to test turbines in strong tidal flows. The project's cost grew a lot, and it was eventually canceled in 2014 after spending nearly $10 million. After this, the company stopped all tidal energy work.
Tidal Power Around the World
- The Rance Tidal Power Station in France was built from 1960 to 1966. It has 240 megawatts of power.
- The 254-megawatt Sihwa Lake Tidal Power Plant in South Korea is the world's largest. It was finished in 2011.
- The Jiangxia Tidal Power Station in China has been working since 1985. It currently makes 3.2 megawatts.
- The first in-water tidal current generator in North America was at Race Rocks in Canada in 2006. It ran for five years but was too expensive to operate.
- A small project was built in Russia at Kislaya Guba. It has 0.4 megawatts. In 2006, it was updated with a new 1.2-megawatt turbine.
- The Jindo Uldolmok Tidal Power Plant in South Korea plans to grow to 90 megawatts. The first 1 megawatt was installed in 2009.
- A 1.2-megawatt SeaGen system started working in 2008 in Strangford Lough in Northern Ireland.
- Plans for a large 812-megawatt tidal barrage in South Korea were canceled in 2013. Another 1,320-megawatt barrage project was also stopped in 2012 due to environmental worries.
- The Scottish Government approved plans for a 10-megawatt tidal stream project near Islay, Scotland. It would power over 5,000 homes, but as of 2023, it has not been built.
- In India, a company planned a 50-megawatt tidal farm in the Gulf of Kutch. But this project was also stopped due to high costs.
- Ocean Renewable Power Corporation was the first company to send tidal power to the US power grid in 2012. This happened when their system was put in Cobscook Bay, Maine.
- In New York City, Verdant Power successfully tested three tidal turbines in the East River. This project made over 300 megawatt-hours of electricity. This was a record for marine energy in America.
- A turbine project was installed in Ramsey Sound in 2014.
- The largest tidal energy project, MeyGen (398 MW), is being built in Scotland. Six megawatts have been working since 2018.
- A 320-megawatt tidal lagoon power plant in Swansea, UK, was approved in 2015 but later rejected in 2018. It would have been the first tidal power plant using a built lagoon.
- A proposed tidal barrage in the Mersey Estuary in the UK could make up to 1 gigawatt of power.
Challenges and Things to Think About
Environmental Concerns
Tidal power can affect sea life. The spinning blades of turbines might accidentally hit swimming animals. Some projects, like the one in Strangford, have a safety system. It turns off the turbine when marine animals get close. But this means losing a lot of energy because many animals pass by. Some fish might also avoid areas with noisy or constantly moving objects. Protecting marine life is a big part of choosing where to put tidal power generators.
The carbon footprint of tidal power is low. It's similar to wind and solar power. It's much better for the environment than power from fossil fuels. The Tethys database has information on how tidal energy might affect the environment.
Tidal Turbines
The main worry with tidal turbines is that fast-moving water might push marine animals into the blades. This could injure or kill them. Also, like all offshore energy, there are concerns about how the electromagnetic fields and sounds might affect sea creatures. Because these devices are in the water, the sound can be louder than from offshore wind energy. The sounds could affect marine mammals, especially those that use echolocation to communicate, like dolphins and whales. Removing tidal energy can also affect water quality and sediment movement. These effects can be small or they can seriously impact nearby ecosystems.
Tidal Barrages
Building a barrage can change the shoreline inside a bay or estuary. This can affect a large ecosystem that relies on tidal flats. Stopping the water flow might mean less fresh water enters the bay. This could lead to more cloudy water and less saltwater. This might kill fish that are important food for birds and mammals. Fish that migrate might not be able to reach their breeding streams. They might also try to go through the turbines. The same sound worries apply to tidal barrages.
Barrages can also make it harder for ships to pass. But locks can be added to allow slow passage. A barrage might also help the local economy by making it easier to cross the water, like a bridge. Calmer waters might also make recreation better in the bay. In 2004, a humpback whale swam through an open gate at a power station. It was stuck for days before finding its way out.
Tidal Lagoons
For tidal lagoons, the main worries are blades hitting fish trying to enter the lagoon. Also, the sound from turbines and changes in how sediment moves are concerns. But these effects are usually only in the local area. They don't affect the whole estuary or bay.
Corrosion
Saltwater can cause metal parts to rust. It can be hard to keep tidal stream generators working well because they are large and deep underwater. Using special materials like stainless steels or titanium can help stop rust damage.
Fluids like lubricants can leak out. This might harm nearby sea life. Good maintenance can help keep harmful chemicals out of the environment.
Fouling
When any structure is placed in the ocean where there are strong currents and lots of sea life, marine organisms will grow on it. This is called fouling.
Cost
Tidal energy costs a lot to set up at first. This is one reason it's not a very common renewable energy source. But research shows that people are willing to pay for and support new tidal energy devices. The technology for making electricity from tides is still quite new. It's possible that costs will go down in the future. The cost-effectiveness changes depending on where the tidal generators are placed.
Because tidal energy is reliable, it's easier to predict how long it will take to pay back the high starting cost. Newer, simpler designs, like the orthogonal turbine, can save a lot of money. They take less time to build, use less metal, and work better.
One possible risk is that rising sea levels from climate change could change local tides. This might reduce how much power can be made in the future.
See also
In Spanish: Energía mareomotriz para niños
- Hydroelectricity
- Hydropower
- List of tidal power stations
- Renewable energy
- Tidal barrage
- Tidal stream generator
- Wave power
