Offshore wind power

Offshore wind power is a way to make electricity using wind farms in large bodies of water, usually at sea. Because there are fewer things like trees or buildings out at sea, the wind blows more strongly and steadily, which helps create more electricity from each wind turbine. Offshore wind farms are often easier for people to accept than those on land because they do not change the view or use up land that people live or work on.

Offshore wind power includes areas close to shore, such as lakes, fjords, and sheltered coastal regions, as well as deeper waters. Most offshore wind farms today use wind turbines that are fixed to the sea floor in shallow water. However, there are newer floating wind turbines being developed for use in deeper waters.

As of 2022, the total amount of electricity that can be made worldwide from offshore wind power was 64.3 gigawatts. China, the United Kingdom, and Germany made up more than three-quarters of this amount. The largest offshore wind farm at that time was the 1.4 gigawatt Hornsea Project Two in the United Kingdom. Other big projects being planned include Dogger Bank in the United Kingdom and Greater Changhua in Taiwan.

Offshore wind power used to cost more than electricity made from other sources, but the price has dropped. By 2019, it cost about $78 for each unit of electricity. In Europe, offshore wind became competitive with traditional power sources in 2017. The amount of electricity from offshore wind has grown very fast, more than 30 percent each year during the 2010s. One big benefit of offshore wind power is that the wind is usually stronger and more steady at sea, so these farms can make more electricity over time than those on land.

History

Capacity

Europe leads the world in offshore wind power. The first offshore wind farm, Vindeby, was set up in Denmark in 1991. In 2009, the average power of an offshore wind turbine in Europe was about 3 MW, and future turbines were expected to grow to 5 MW.

By January 2014, 69 offshore wind farms had been built in Europe, with a total power of 6,562 MW. The United Kingdom had the most, with 3,681 MW, followed by Denmark with 1,271 MW and Belgium with 571 MW.

By the end of 2015, 3,230 turbines at 84 offshore wind farms in 11 European countries were in use, giving a total power of 11,027 MW. In 2022, the offshore wind industry grew by 8.8 GW, bringing the total to 64.3 GW. The Global Wind Energy Council expects even more growth in the future.

Costs

In 2010, offshore wind power was one of the most expensive energy sources. But costs have been dropping faster than expected. By 2016, some projects were cheaper than expected prices for the year 2050.

In the United States, offshore wind projects cost more to build than onshore ones. In 2023, building offshore wind cost US$4,000 per kilowatt, while onshore wind cost US$1,363 per kilowatt. Some big U.S. projects have faced delays due to rising costs.

Future development

In 2016, experts predicted that offshore wind power would grow to become 8% of the ocean economy by 2030, creating jobs for many people and adding great value.

The European Commission sees offshore wind as very important for the future, especially as part of its Green Deal. By 2050, the world may have 1550 GW of offshore wind power, which is much more than in 2017.

New technologies are helping build wind farms farther from shore where the wind is stronger. Floating foundations are one such technology that works well in deeper waters.

Economics

Putting wind turbines in the water has advantages because the wind is stronger there, especially in the afternoon when people use the most electricity. Turbines can also be placed closer to big cities, so we don’t need long power lines.

But there are downsides too. Building and fixing turbines in the water is harder and more expensive. The salt water can damage the machines, and workers need special gear and boats to reach them. Overall, offshore wind costs more than land-based wind farms.

In 2022, the cost of electricity from new offshore wind projects went up a little, unlike other renewable energy sources which were getting cheaper. However, researchers think costs will go down in the future as technology improves and we build more farms.

Offshore wind resources

See also: Wind power on the Great Lakes

Offshore wind resources are very large and spread out because most of the Earth's surface is covered by water. The wind at sea is usually stronger than wind on land because there are no trees, buildings, or other things in the way. This makes it a great place to generate electricity.

In places like the North Sea, wind turbines can produce about 30 kilowatt-hours of energy for every square meter of sea area each year. The amount of energy we can get from offshore wind depends on how strong the wind is and how deep the water is. Right now, wind turbines can be built in water up to about 50 meters deep. In deeper water, we would need special floating turbines, which could work in water up to one kilometer deep. Studies show that there is a lot of potential for offshore wind power—over 17 terawatts in just 50 countries. Countries like Argentina and China have especially big opportunities, with almost 2 and 3 terawatts of potential, respectively.

Planning and permitting

Planning an offshore wind farm needs lots of information. We need to know about the wind, the depth of the water, how the sea moves, and what the sea floor is like. We also need special tools like LIDAR, SODAR, radar, and underwater robots to help us learn more.

One big challenge is figuring out how all these pieces will work together and how they might wear down over time. We also have to think about how to protect the equipment from rust and water damage. Making these plans can take many years and lots of money, so countries are trying new ways to make it easier and faster to build these farms.

Legal framework

The rules for building and running wind turbines at sea are set by both national and international laws. The main international law is the UNCLOS (United Nations Convention on the Law of the Sea), which guides how countries can use the oceans.

Close to the shore, in territorial waters (up to 12 nautical miles from the coast), the nearby country has full control over the rules for offshore wind turbines.

Farther out, in the exclusive economic zone (up to 200 nautical miles from the coast), countries can build and manage wind farms for energy. They can also set up safety zones around these farms that ships must follow, as long as they tell others about these zones beforehand.

Beyond these zones are the international waters, where the rules for building wind farms are still unclear. Some suggest treating these farms like ships or artificial islands to make them fit within international laws.

Right now, building wind farms in very deep water is difficult, but new technology with floating wind turbines might make this possible in the future.

Types

Offshore wind farms can use two main types of turbines depending on how deep the water is. In shallow water, up to about 50 meters deep, turbines with fixed foundations are used. These turbines have strong bases that sit on the sea floor.

Most offshore wind farms today use these fixed turbines. The bases can be made in different ways, like single large pillars or triangle shapes, to keep the turbines steady. These designs help them stay strong even in rough waters.

For very deep water, over 60 meters, floating turbines are used. These turbines are special because they can float and stay anchored to the ocean floor. This makes it possible to build wind farms in deeper areas where fixed bases can't be used.

Main article: Floating wind turbine

Some smaller floating turbines have been tested, and bigger projects are being planned. Most large offshore wind turbines today spin horizontally, but scientists are also studying vertical spinning turbines for future use because they might be even bigger.

Turbine construction materials considerations

Offshore wind turbines are built in oceans and large lakes, so the materials must be different from those used on land. They need to resist rust from salt water and handle the forces from waves and wind. Steel towers are often used because they can withstand these forces well.

Because turbines are always near salt water, the steel must be treated to stop rust, especially where waves hit the tower. Two ways to protect the steel are using special coatings and a method called cathodic protection, where other metals are added to stop the steel from rusting. Coatings like zinc and special paint layers help keep the steel safe from water and weather.

Installation

Specialized jackup rigs and wind turbine installation vessels are used to put together the bases and turbines for offshore wind farms. Since 2019, newer, bigger ships are being built that can lift very heavy weights high above the water.

Many offshore wind farms use a single, big support structure called a monopile foundation to hold up the turbines. Other types include tripods and gravity base foundations. To build a monopile foundation, a large steel pile is driven deep into the sea floor. After that, concrete is poured around it, and extra stones are added to protect it. The turbine tower is put together in two parts and joined with a special concrete mix to make it strong.

Because the parts are so big, special offshore wind port facilities have been built to help move and prepare them before installation.

Connection

Grid connection

There are different ways to connect offshore wind power to the power we use on land. One common way is using high-voltage alternating current (HVAC) lines. However, HVAC has some problems, especially when the wind farms are far from shore. It can lose a lot of energy and become expensive over long distances.

Another option is using high-voltage direct current (HVDC) cables. HVDC does not lose as much energy and can work over much longer distances. But HVDC needs special equipment to change the power to work with the regular power grid. Researchers are also looking at new ways to combine these technologies to make them even better.

Marine vessel connection

A new system called Stillstrom, being developed by the Danish company Maersk Supply Service, will let ships use energy from offshore wind farms while they are at sea. This can help reduce pollution from ships that are just sitting still and using fuel.

Maintenance

Offshore wind turbines need special care because they are far out at sea. Workers use boats or helicopters to reach them, making it harder to fix things quickly. To keep the turbines working well, teams sometimes live right on the wind farm.

One way to protect the turbines is by using a special power system that stops rust and corrosion. This is safer for the environment and saves money compared to older methods. Inspecting the turbine blades used to mean climbing down them, but now some farms use cameras or drones to check the blades from a distance, which is much faster.

Decommissioning

As the first offshore wind farms reach the end of their use, a new industry has grown to safely take them apart and reuse materials. This process costs about DKK 2-4 million (or $300,000-600,000 USD) for each megawatt of power the wind farm produced.

The very first offshore wind farm to be taken apart was Yttre Stengrund in Sweden in November 2015. This was followed by Vindeby in 2017 and Blyth in 2019.

Environmental impact

Main article: Environmental impact of wind power

Offshore wind farms produce electricity with very little effect on the climate, similar to wind farms on land. They also make less noise and have less impact on the view compared to wind farms on land.

As companies that build offshore wind farms have learned more about how these farms affect nature, they have started using better ways to build them. In 2022, a big company that builds offshore wind farms called Ørsted teamed up with a group that helps protect nature called the World Wide Fund for Nature (WWF). They want to build more wind farms while also helping animals and plants. Another company, Vattenfall, invested money in projects in Norfolk to help fight climate change.

When building offshore wind farms, there are rules to protect the sea and its animals. In 2008, rules were made to make sure that building these farms does not hurt sea animals, the sea floor, or the whole sea environment. If a wind farm hurts the sea, the company must fix the problem in another way.

Even though offshore wind farms help fight climate change, they can sometimes affect sea animals. Building and fixing the farms can disturb animals that live in the sea, especially during times when animals are moving or having babies. Some sea animals might change where they live because of the farms. Also, the noise and sight of the farms can change how some birds and other animals behave.

One good thing about offshore wind farms is that they can create places where sea animals can live, like artificial reefs. But sometimes, the farms can also hurt sea habitats by moving sand and dirt on the sea floor.

People are still learning how offshore wind farms affect the sea and its animals. Some studies show that the farms might change where tourists go, but others think this is not a big problem. There are also worries that the farms might bring new sea animals that do not usually live in that area, which could change the balance of nature.

When planning where to build offshore wind farms, it is important to think about how they will affect the sea and its animals. Some ways to protect animals include using models to predict where birds might hit the wind turbines. Making plans for where to build wind farms can be tricky because many different people and groups have different ideas about what is best. But having rules to protect the sea can help make sure that building wind farms helps both people and nature.

Security considerations

Offshore wind farms have not always had strong security measures. After a big attack on pipelines called Nord Stream, companies are now starting to use cameras and drones to watch wind farms from far away. As more wind farms are built in different places, better security plans are needed, including ways to protect parts under the water.

There are also concerns about sharing information between different groups and governments to keep these farms safe. Some people worry that these wind farms could be used in conflicts, and this needs to be thought about when making security plans. Some groups have been seen watching important sea structures, which could be a sign of trouble. There are also worries about parts made outside of certain countries, and about keeping computer systems safe. In 2022, a company that makes wind turbines had problems with its computers, and another attack stopped communication with many wind turbines for a short time.

Largest offshore wind farms

Main article: List of offshore wind farms

See also: Lists of offshore wind farms by country

Location map

Projects

Many current projects are found in the waters of Europe and East Asia.

There are also plans for new projects in North America. In the United States, work is happening in areas with strong winds along the East Coast, the Great Lakes, and the Pacific coast. In December 2016, the first offshore wind farm in the USA, the 30-megawatt Block Island Wind Farm with 5 turbines, began operating. Some people and scientists think the bases of these turbines are helping create new homes for sea life.

Another wind farm is being planned off the coast of Virginia Beach. In August 2018, Dominion Energy announced plans for a small test project with two turbines, located 27 miles from shore.

Canada is also looking at places in the Great Lakes for future wind farms. India is exploring offshore wind power too, with plans for a demonstration plant off the coast of Gujarat.

The Netherlands set a big goal in February 2022 to produce 21 GW of offshore wind power by 2030, which would provide about three-quarters of the country’s electricity. This helps the country work toward reducing CO₂ emissions.

In 2026, the UK announced it would join a plan with other European countries to build a huge 100 GW wind power network in the North Sea, connecting nations with underwater cables. Countries taking part include Belgium, Denmark, France, Germany, Iceland, Ireland, Luxembourg, the Netherlands, and Norway.

Offshore wind power by country