Offshore wind energy: From theory to practice in clean energy

Introduction

The modern wind turbine was invented by a Scottish electrical engineer, James Blyth, in 1887. Everything that is invented arises out of necessity. Sometimes by mistake, but sometimes by pure ingenuity and curiosity. And that is what happened with this pioneer who built a wind turbine to illuminate his vacation home. The shape and size of the turbine were very different from those we see today. It was 10 meters high and consisted of a wooden tripod tower, semi-cylindrical canvas sails and a vertical main rotor shaft. Other sources also tell us that, in 1887, American scientist Charles F. Brush (1849-1929) built the first wind turbine for electricity generation, which had a rotor diameter of 17 meters and 144 rotor blades made of cedar wood.

From that time until today, the evolution and the need to resort to this way of generating alternative energy has increased. Nowadays, wind turbines can measure between 80 and 120 meters, unlike those built by Blyth and Brush. The blades can even reach 100 meters in length and weigh approximately 200 tons.

The transition to a sustainable future depends largely on our ability to harness clean, renewable energy sources. Wind energy is one of the most promising emerging technology development opportunities and stands out as a viable solution for reducing carbon emissions and mitigating climate change.

Like onshore, offshore wind energy has key components such as offshore wind turbines, wind farms, the number and capacity of installed devices and their importance in the context of clean energy. The differences between them, their advantages and challenges associated with the implementation of these technologies, make offshore a greater investment than onshore.

What is the principle and operation of offshore wind energy?

The principle is the same for both offshore and onshore OWE. Offshore, unlike onshore, offshore winds are more constant and this allows for more efficient and predictable power generation (WindEurope, 2023). “The average power output of an onshore wind turbine is between 6 and 7 MW, while offshore wind turbines can reach 10 MW. It should also be noted that the OWE can be fixed or floating, according to the generation requirements and conditions of the installation.

But there is one distinctive feature of offshore wind turbines and that is that their design allows them to withstand extreme conditions, such as saltwater corrosion and strong currents” (Musial & Ram, 2010).

A question of design and technology

There are 248 wind power component manufacturing plants in Europe, most of which can increase their capacity depending on demand. In the specific case of offshore wind turbines, they must have corrosion protection for their components. For this purpose, special materials and coatings are used that resist the saline environment. It is worth noting that marine turbines, due to their characteristics, must be larger, i.e., taller towers and longer blades to allow them to capture more energy from the wind.

Generally, these construction materials for wind turbines are steel, fiberglass, resin or plastic, iron or cast iron, copper and aluminum, but also wood. Aluminum alloys and steel are used for the main tower structure and turbine blades, while advanced composite materials such as fiberglass or carbon fiber reinforced with epoxy resin are used for the blades. Specifically for offshore wind energy, turbines are predominantly made of steel (66-79% of the total turbine mass); fiberglass, resin, or plastic (11-16%); iron or cast iron (5-17%); copper (1%); and aluminum (0-2%), according to a report by the National Renewable Energy Laboratory (Table 30), depending on the make and model.

However, the installation of offshore wind turbines is a complicated and expensive task. It requires the use of floating platforms or fixed foundations, depending on water depth. “Fixed foundations are suitable for shallow water, while floating platforms allow installation in deeper water. This advanced technology allows offshore wind turbines to be located in areas where winds are stronger and more constant, thus maximizing energy production” (International Renewable Energy Agency, 2022).

Offshore wind farms: A collective approach

“An offshore wind farm is the grouping of several wind turbines installed at sea. They are strategically located in areas with high wind resources to make the most of wind energy. One of the most prominent examples is the Hornsea 1 wind farm in the United Kingdom, which is the largest offshore wind farm in the world, with an installed capacity of 1,218 megawatts (MW)” (Global Wind Energy Council, 2023).

One of the main characteristics is that offshore wind farms have several advantages. First, their offshore location reduces the visual and acoustic impact on coastal communities. In addition, being far from the coast, they do not compete for land use with other human activities, such as agriculture or housing in urbanized areas. However, these farms are more expensive to build and maintain than onshore wind farms due to the need for advanced technology and specialized equipment. Offshore wind farms are mega-structures that are built at an average distance of 41 kilometers from the coast and sit at an average depth of 27.5 meters.

“This involves several engineering challenges: How are the wind turbine parts transported to the wind farm? How is the nacelle placed on the tower? And how are the blades assembled? Having the right lifting equipment and trained personnel is important to the success of the project. For example, one of the biggest challenges is placing the nacelle on the tower. The weather conditions at sea can be tricky: waves, wind, etc. So precision is vital” (Crosby Airpes, 2022).

Installed capacity: Growth and projection

Installed OWE capacity in Europe has experienced significant growth in recent years of up to 102% in the last decade. This growth reflects the commitment of governments and companies to the transition to cleaner and more sustainable energy sources.

The increase in installed capacity is partly due to investments in research and development of offshore wind technologies. In addition, favorable government policies, such as subsidies and feed-in tariffs, have incentivized the construction of offshore wind farms (European Commission, 2022). Installed capacity is expected to continue to grow in the future, as more countries recognize the potential of offshore wind to contribute to the decarbonization of their economies.

The importance of offshore wind

“The wind industry generated up to 2019, €2.5 billion of value added to the EU economy for every new GW of onshore wind power installed and €2.1 billion for every new GW of offshore wind power” (WindEurope, 2024).

OWE stands out as one of the main sources of clean energy due to its ability to generate large amounts of electricity without emitting greenhouse gases. Unlike fossil energy sources, wind is an inexhaustible and free source, which guarantees a constant supply of energy. By generating electricity from wind, the need to burn coal, oil or natural gas is reduced, which in turn reduces emissions of carbon dioxide (CO2) and other pollutants (U.S. Department of Energy, 2022). This is critical to mitigating climate change and improving air quality.

Differences between onshore and offshore wind

Onshore and offshore wind energy are based on the same principle of harnessing the wind, but there are significant differences between the two. The main difference is the location of the wind turbines, which has several implications in terms of design, installation, operation and maintenance.

One of the most notable differences is the greater constancy and strength of the wind at sea. This allows offshore wind turbines to generate more power compared to their onshore counterparts. In addition, offshore wind farms tend to have a higher installed capacity due to the possibility of installing larger turbines. However, the installation and maintenance costs of offshore wind turbines are higher due to the challenging conditions of the marine environment (National Renewable Energy Laboratory, 2020).

Advantages of offshore wind energy over onshore wind energy

Offshore wind energy has several advantages over onshore wind energy. First, offshore winds are stronger and more constant, which allows for greater energy generation and consequently greater efficiency and profitability in the long term.

Another advantage is the possibility of installing offshore wind farms in areas that do not compete with other human activities. On land, the installation of wind turbines may face land use conflicts with agriculture, urbanization and other economic activities. At sea, this problem is minimized, which facilitates the expansion of installed wind energy capacity.

Challenges and considerations

Despite its many advantages, offshore wind energy also faces significant challenges. One of the main ones is the high cost of installing and maintaining offshore wind turbines. The need for strong structures and advanced technologies makes the construction and operation process more expensive. In addition, the logistics of transporting and installing components at sea are more complex and require the use of specialized vessels and offshore cranes.

Another major challenge is the environmental impact of offshore wind farms. Although offshore wind energy is a clean energy source, its construction and operation can affect marine life, ocean currents and coastal ecosystems. Environmental impact studies and mitigation measures are needed to reduce these effects. In addition, the coexistence of offshore wind farms with other activities, such as fishing and shipping, requires careful planning and proper management.

Investment and costs

The investment to install an offshore wind farm is considerably higher than that of an onshore wind farm. According to estimates, the average cost of installing an offshore wind turbine can be two to three times higher than an onshore wind farm. This is due to several factors, such as the need for advanced technologies, firm structures and specialized equipment. In addition, maintenance costs are higher due to the difficult conditions of the marine environment.

However, despite the high upfront costs, OWE can be a profitable investment in the long term. The higher efficiency and generating capacity of offshore wind turbines allow for more consistent and predictable energy production, which can translate into higher revenues. Furthermore, reducing carbon emissions and contributing to the decarbonization of the economy can generate additional benefits in terms of sustainability and meeting environmental targets.

Offshore wind energy investments in Europe and the U.S.

“Denmark was the forerunner of wind energy in Europe, both onshore and offshore. The country installed the first offshore wind farm in 1991 at Vindeby in the Baltic Sea. Although the farm has since been decommissioned, its creation marked the beginning of the large-scale development of offshore wind energy in Europe. Denmark continues to be a leader in technological innovation and implementation of both onshore and offshore wind projects.”

Investment in offshore wind energy has grown significantly in Europe in recent years, with several countries investing significantly in this technology. Let’s take a look at some updated data:

United Kingdom: It is the world’s largest producer of offshore wind energy, with an installed capacity of 13.9 GW.

• Germany: It has an installed capacity of 7.7 GW.
• Netherlands: It has an installed capacity of 3.3 GW.
• Belgium: Installed capacity of 2.1 GW.
• Norway: A 300-meter wall of 40 floating turbines is currently being erected to catch the wind offshore. It is an energy giant that will be erected north of Bergen, producing 99 GWh per year.

The following table shows the most significant investments by country:

In the United States, offshore wind is booming. Here are some of the major offshore wind farms and their investment and generation details:

• Vineyard Wind: This is one of the largest and best known projects. It has a capacity of 800 MW and is expected to generate enough energy to supply more than 400,000 homes. The total investment in this project is approximately $2.8 billion.
• Revolution Wind: With a capacity of 704 MW, this offshore wind farm is designed to provide energy to more than 350,000 homes. The investment in this project is around US$2.5 billion.
• Coastal Virginia Offshore Wind: This project has a capacity of 2.6 GW and is expected to generate enough energy to supply more than 650,000 homes. The total investment in this project is approximately US$8 billion.
• Commonwealth Wind: It has a capacity of 1,232 MW, and is designed to provide energy to more than 750,000 homes. The investment in this project is around US$4 billion.

In total, the U.S. offshore wind industry is expected to invest $65 billion by 2030, with a projected capacity of 40 GW by 2035. Of note, the largest offshore wind farm in the U.S. is moving full speed ahead. With 2.6 GW of power, the CVOW project will change energy in Virginia forever. Dominion Energy is building a mega offshore wind project with 176 turbines, capable of powering millions of homes. The project is already 50% complete and remains on track for delivery in 2026.

Conclusion

The future of offshore wind energy is promising. As governments and businesses recognize the importance of clean energy in combating climate change, installed offshore wind capacity is expected to continue to grow. Investments in research and development are driving innovation in offshore wind technologies, enabling the installation of larger and more efficient turbines.

References

1. WindEurope. (2023). Offshore Wind in Europe: Key Trends and Statistics 2023. Retrieved from https://windeurope.org
2. International Renewable Energy Agency (IRENA). (2022). Offshore Renewable Energy. Retrieved from https://www.irena.org
3. Global Wind Energy Council (GWEC). (2023). Global Offshore Wind Report 2023. Retrieved from https://gwec.net
4. Musial, W., & Ram, B. (2010). Large-Scale Offshore Wind Power in the United States: Assessment of Opportunities and Barriers. National Renewable Energy Laboratory (NREL). Retrieved from https://www.nrel.gov
5. European Commission. (2022). Clean Energy for All Europeans. Retrieved from https://ec.europa.eu
6. National Renewable Energy Laboratory (NREL). (2020). Offshore Wind Market Report: 2020 Edition. Retrieved from https://www.nrel.gov
7. U.S. Department of Energy. (2022). Offshore Wind Technologies Market Report. Retrieved from https://www.energy.gov