Tidal power

Tidal power, also called tidal energy, is a way to make electricity by using the movement of ocean tides. Tides are the regular rising and falling of sea levels caused by the pull of the moon and sun. This movement can be used to spin turbines, which then create electricity.

Although tidal power is not used as much as other energy sources, it has great potential for the future. Tides are more predictable than wind or sunlight, which makes them a reliable energy source. In the past, tidal power was expensive and only worked in a few places with very big tidal changes. But new technology is making it more possible to use tidal power widely and at lower costs.

Historically, people used tides to power waterwheels that ground grain, especially in Europe and along the Atlantic coast of North America. This practice dates back to Roman times and the Middle Ages. In the 19th century, people began using tides to create electricity. Today, big tidal power plants exist around the world. The first large tidal power plant was built in France, and later, a very large one opened in South Korea. These plants show how tides can be used to provide clean energy for many people.

Principle

Main articles: Tide and Tidal acceleration

Tidal energy comes from the regular rise and fall of ocean water, called tides. These tides happen because of the gravitational pull of the Moon and the Sun on Earth's oceans. As the Earth spins and the Moon moves around it, the water levels change in a predictable way.

Tidal power is special because it uses energy from the Earth-Moon system, unlike other energy sources that come from the Sun. This makes tidal power a reliable and lasting source of energy. Even though taking energy from tides very slowly changes the Earth's rotation, this effect is so small that it won't matter for a very long time.

Methods

Tidal power can be created in four different ways:

Tidal stream generator

Main article: Tidal stream generator

Tidal stream generators use the moving energy of water to turn turbines, much like wind turbines use wind. Some can be built into bridges or placed underwater, so they don’t change how things look. Narrow places between land can make the water move very fast, which turbines can use to make power. These turbines can be set up in different shapes.

Tidal barrage

Main article: Tidal barrage

Tidal barrages use the difference in height between high and low tides. Special dams are built to trap water when the tide comes in, storing energy. When the tide goes out, the water flows through turbines that make electricity. Barrages are like big dams built across wide areas where tides move in.

Tidal lagoon

A newer way to get tidal energy is to build round walls with turbines in them. These walls create spaces that are not natural, and they can be made in different designs. Some designs store extra energy from wind or sun power to help make electricity when needed. Plans for a big project in Wales, United Kingdom, were stopped before it could be built.

Dynamic tidal power

Main article: Dynamic tidal power

Dynamic tidal power is an idea for a new technology. It would use the way tides move to create power by building very long dams stretching out from the coast into the ocean. These dams would make a big difference in water level along the coast, creating strong currents that could be used to make electricity.

US and Canadian studies in the 20th century

In 1924, the US Federal Power Commission studied large tidal power plants. These would have been built in Maine and the Canadian province of New Brunswick, using dams and locks around the Bay of Fundy and Passamaquoddy Bay. However, nothing came from this study, and it is not known if Canada was even asked about it.

Later, in 1956, a company in Halifax asked two groups to study tidal power on the Nova Scotia side of the Bay of Fundy. Both groups said lots of power could be made, but it would cost too much.

In 1961, the US and Canada made a report about a tidal power project. It said the project would help the US but not Canada. In 1977, another study looked at possible places for tidal power in Canada, but these places were never built.

US studies in the 21st century

A public utility district in Washington State, called the Snohomish PUD, started a tidal energy project in 2007. They chose a company from Ireland to help build turbines and equipment. The plan was to place the equipment where the tides flow strongly and use it for four to five years before removing it.

The project was supposed to cost $10 million, with half coming from the utility and half from government grants. However, the costs grew too large, reaching about $38 million by 2014. The utility asked the government for more money, but when it wasn’t provided, they stopped the project. They had already spent nearly $10 million and decided not to continue with tidal energy after this.

Rance tidal power plant in France

In 1966, Électricité de France opened the Rance Tidal Power Station on the estuary of the Rance River in Brittany. It was the world's first tidal power station. For 45 years, it was the largest tidal power station in the world. The plant has 24 turbines that can produce up to 240 megawatts of electricity.

Tidal power development in the UK

The world's first place to test ocean energy was set up in 2003 in the UK to help grow the wave and tidal energy industry. This place, called the European Marine Energy Centre (EMEC), is located in Orkney, Scotland. It has helped more wave and tidal energy devices than any other single site in the world. EMEC offers different test spots where real sea conditions can be used. One of its tidal test sites is at the Fall of Warness, near the island of Eday. This spot has very strong tides that can move up to 4 meters per second. Many companies have tested their tidal energy ideas here. The area could provide a lot of energy each year. If more tidal energy tools are added across the UK, it could give a lot of power.

Current and future tidal power schemes

Main article: List of tidal power stations

Tidal power uses the movement of ocean tides to create electricity. One famous example is the Rance tidal power plant in France, which has been working since 1966. In South Korea, the Sihwa Lake Tidal Power Plant is the largest tidal power station in the world, finishing construction in 2011.

Other places are also planning or testing tidal power, like China and Scotland. Some projects, such as the one near Swansea in the UK, faced delays or changes due to environmental worries. Scientists and engineers keep finding new ways to use tides for clean energy in many parts of the world.

Issues and challenges

Tidal power can affect sea creatures. The moving parts of the machines might accidentally hurt or trap fish and other animals. Some projects have safety features to turn off machines when animals come close, but this means losing some power. Scientists work hard to place these machines where they will bother nature the least.

Saltwater can damage metal parts, making it hard to keep the machines working well. Engineers use special materials that don’t rust easily. Even with care, some harmful liquids might leak out, so regular checking helps keep the ocean safe. Tidal energy costs a lot to start with, but scientists are finding ways to make it cheaper in the future.

Structural health monitoring

Tidal energy is special because water is much heavier than air—about 800 times heavier! This makes tides very strong and reliable compared to wind. Because of this, checking the health of tidal energy structures is very important. It helps make sure we can use this energy in a smart and save way.