Floating Wind Turbines

Floating offshore wind is a new technology with a bright future, allowing access to more wind power in deeper oceans than fixed foundation turbines. But how can countries use this technology’s potential to produce wind energy and accomplish ambitious environmental goals?

This article will discuss the enormous potential of floating wind projects as part of the worldwide energy revolution, including inventing floating wind turbines, their history, and their environmental influence on our surroundings.

A floating wind turbine is an offshore wind platform mounted on a floating foundation. It can generate renewable wind power in sea depths where fixed-foundation turbines are not viable. Floating wind farms can considerably enhance the sea area available for offshore wind farms, particularly in nations with shallow oceans.

Why floating offshore wind?

Driving for a more environmentally friendly and sustainable planet, we need ways to harvest new renewable energy sources efficiently and safely rather than relying on fossil fuels from the oil and gas industry. Offshore wind is one of the most promising energy sources we have just begun to capture. The wind offshore is typically more substantial and more consistent than onshore wind, allowing the turbines to have better energy efficiency.

We estimate that most wind energy is found offshore and in locations where fixed foundations do not work. For example, we estimate that Americans can only capture 60% of available USA offshore wind energy with floating offshore wind turbines. Europe and Japan can get an additional 4 Terawatts and 500 Gigawatts of power from floating offshore wind turbines.

Easier Installation And Maintenance

Assembling the floating wind system components in port reduces highly weather-dependent procedures like offshore large lifts. In addition, less weather-dependent processes require smaller vessels. This means projects do not have to wait for good weather to avoid significant delays and fewer safety hazards.

In terms of installation, certain maintenance operations, such as turbine maintenance or part-exchange and repair, can also take place in port. Port-based maintenance minimizes the need for employees to stay offshore for extended periods and use big construction vessels.

Less Environmental Impact

Floating wind turbines benefit not only from being “out of sight, out of mind,” but their installation is also less invasive than standard bottom-fixed projects:

• Drag anchors, SEPLA anchors, suction piles, and other anchoring technologies reduce the need for noisy piling erection, putting fish and marine mammals at risk. 
• They have less influence on the delicate coastal environment and terrain because they are further away from the coastline.
• They also have a lower impact on other marine users like fishing, pleasure boats, and marine transportation.

Improved Access To Better Resources Means Increased Capacity

Winds are not only stronger farther offshore, but they are also more consistent. Over 80% of offshore wind energy resources are in waters deeper than 60 meters, making bottom-fixed installations impractical. Additionally, stronger and more consistent winds can result in capacity factors of over 60% for floating turbines, compared to 45-60% for a fixed wind turbine in the North Sea. As a result, floating wind projects may have a lower Levelised Cost of Energy (LCoE) than selected wind projects.

Positive Impact On The Local Economy

Floating wind turbines are built and assembled onshore near their final installation point. Local manufacturing means the local supply chain has to support the industry. The industry must include welding, assembly, electricians, heavy lifting equipment, and many other high-value jobs. 

Great Yarmouth is an example of a local manufacturing hub for the floating wind industry. Their yard, east of England, has ample storage and heavy lift facilities built for the offshore wind industry. 

What is floating offshore wind energy?

Remember that offshore wind energy is a renewable, clean energy source generated by harvesting the power of the wind with a floating turbine installation. Floating turbines are very similar to onshore wind turbines and offshore fixed foundations, except the foundation, is floating. Offshore wind is typically faster and more constant due to fewer barriers. Think about the wind at a beach versus the wind in a city. You may get small gusts in the city due to all the buildings and trees, and the wind at the beach is consistently blowing to shore.

History of floating wind turbines

Onshore wind turbine installations exist from the Tropics to Antarctica. In the early 1970s, developers began putting the structures in the ocean to create an offshore wind market. They added more than 6 gigawatts to capacity in 2019. Recently, the wind industry is attempting an even bigger ambition – installing turbines in boats instead of fixed foundations. Now at their peak, commercially mature floating winds may become a critical new renewable energy market.

Offshore wind energy is also one of the most minor utilized renewable energy sources. The costs of a floating offshore wind farm are much higher since they are at a larger scale with more equipment and higher risk since they are at deep water depths and far away from shore. It has been challenging to engineer and build floating foundations in deeper waters.

1972

In 1972, University of Massachusetts Amherst Professor William E. Heronemus pioneered the notion of large-scale offshore floating wind turbines.

2007

In December 2007, Blue H Technologies deployed the world’s first floating wind turbine 21.3 kilometers off the coast of Apulia, Italy.

2008

An 80 kW prototype was put in waters 113 meters (371 feet) deep to collect wind and sea conditions data before being decommissioned at the end of 2008. Developers built the turbine with a tension-leg platform and a two-bladed turbine.

2009

In September 2009, Hywind became the first large-capacity, 2.3-megawatt floating wind turbine to operate in the North Sea near Norway. Siemens Wind Power built the turbine and mounted it on a floating tower built by Technip.

2011

In September 2011, Principle Power, with funding from EDP, Repsol, ASM, and Portugal Ventures, launched the second grid-connected full-scale prototype in Portugal. Wind Float WF1 was equipped with a Vestas 2 MW turbine and generated over 17 GWh of electricity during the next five years.

2013

The first 2 MW Hitachi turbine, with a capacity factor of 32% and a floating transformer, entered service in November 2013. Following a 5-year trial phase near shore, Hitachi installed the first floating turbine in Japan at Fukue Island in 2016.

Environmental Impacts of Floating Wind Turbines

Floating wind turbines have a lower environmental impact than fixed foundation offshore wind farms. Compared to fixed foundation installations in contact with the sea floor and any species that call it home, floating structures are only attached to the seabed by a few anchoring systems with minimal environmental impact. Also, the floating offshore wind turbines are made onshore and towed out to their final offshore site, minimizing their onshore ecological implications.

Marine Life

Wind turbine foundations can function as artificial reefs, giving a surface to which creatures to attach. As a result, the number of shellfish and the animals that feed on them, such as fish and marine mammals, may rise. The shielding effect is another potential benefit. The exclusion of boats inside a safety buffer zone surrounding wind turbines may constitute a de facto marine reserve, reducing disruption from shipping.

Underwater Sound Levels

Underwater sound levels are unlikely to reach harmful levels during wind turbine operation or obscure marine mammals’ auditory communication. However, seabirds are most concerned during this stage of growth. Collisions with rotating turbine blades can result in death. In contrast, avoidance responses may result in displacement from critical habitats or increased energy expenditures.

Birds Migrating

Wind turbines pose a significant risk to birds, so developers must be aware of a wind turbine’s possibly fatal risk to migratory birds. Scientists have attributed risk to site-specific, species-specific, and seasonal factors. Therefore, turbine location analysis uses seabird collision risk models to evaluate turbine locations. 

Electromagnetic Fields

The cables that transmit the generated electricity during operation will emit electromagnetic fields. The electromagnetic field could impact the movements and navigation of species sensitive to these fields, such as fish, notably elasmobranchs. The fields also affect some teleost fish, decapod crustaceans, and sea turtles. 

Fishing

Fish tend to congregate by floating structures for protection and more transparent water. Therefore, commercial fish species may benefit if the wind farm region forbids fishing. Albeit, this may result in a shift in fisheries effort and, as a result, a change in catches and bycatch.

Seabirds

We believe seabirds are the most vulnerable when developers build wind farms near breeding colonies. Birds make frequent excursions between their nest and foraging areas during the mating season. Keeping wind turbines away from breeding grounds could lessen the risk of collision. For wind farms proposed further offshore, we know little about the distribution and habitat use of seabirds in these areas outside of the nesting season and their connectivity with any protected areas. 

How offshore floating wind turbines work

To understand how the floating wind turbines work, we must understand the theory of buoyancy. Buoyancy is the equal and opposite force a body of liquid (water in this case) will exert upwards on an object that displaces a volume of similar mass. All floating vessels rely on the basic principle of buoyancy. The buoyancy principle explains why offshore wind foundations are so big – they need to displace a large volume of water to offset how heavy they are! The foundations also need to be engineered to provide stability to the turbine while floating in the water with waves, currents, and winds.

We also need to describe the two main parts of a floating wind turbine: the foundation and the turbine.

Foundation

The foundation is the part that supports the wind turbine and allows it to float in water. The foundation must be strong enough to support 400-foot tall wind turbines, sturdy enough to stay balanced against storms, hurricanes, and typhoons, and lightweight enough to float. The foundations are attached to the seabed with mooring lines. Mooring lines are heavy-duty steel cables used to prevent the foundation from moving too much relative to the sea floor.

Turbine

The turbine sits on top of the foundation and is responsible for the power generated by wind energy. The turbine has three main parts, the tower, the nacelle, and the rotor. The tower is what connects the turbine to the foundation. It gives blades enough clearance away from the foundation to not get damaged. The nacelle is the turbine’s hub that holds the generator that makes electricity. The rotor is the part that has the blades of the windmill and is what turns wind energy into kinetic energy powering the generator.

Floating offshore wind turbines generate electricity like any onshore or fixed offshore wind farms. The first step is the wind turns the blades of the rotor. Then the rotor is connected to a generator by a series of gears and shafts. The rotating shaft spins inside the generator, where the generator makes electricity.

Types of floating offshore wind platforms

There are three main types of floating offshore wind foundations used today:

• Spar buoy platforms
• Semi-submersible platforms
• Tension leg platforms.

Spar buoy platform

Buoy platforms look like long cylinder that floats in water. 

These platforms lower their center of mass by putting lots of weight at the lowest possible point. The lower center of mass improves the stability of the floating foundation. Since the buoys are very tall and relatively skinny, the weight must be at the bottom to prevent the buoy platform from flipping over.

The spar buoy platform achieves buoyancy from its large size that can displace a large volume of water with minimal horizontal surface area. Creating a buoyant foundation is challenging for spar buoys as the wind turbines get larger and larger. The larger the turbine is, the longer and heavier the buoy will have to be to keep it afloat.

Semi-submersible platform

Semi-submersible platforms are large cylindrical platforms connected by rope or cables. They try to maximize surface area with the water. They can offset a large amount of water by going as shallow as possible. Since these use large cylindrical platforms, they have a broader base and are very stable. A downside of the wider stability is they take up much more space than other platforms.

The semi-submersibles can easily accommodate more giant turbines since these platforms displace a large volume of water without going very deep. A turbine that weighs twice as much would only require twice as much water displacement, which would not be very deep for these platforms.

Tension leg platform

Tension leg platforms are similar to other platforms, except they do not float when under the weight of a turbine. Tension legs affix the platforms to the ocean floor – very rigid cables that keep the platform up and eliminate any vertical movement. Think of the tension legs like legs for a chair.

A tension leg platform is becoming more preferred as they cost about one-third as much as the other platforms. The tension cables are very rigid, and the cabling is susceptible to being moved by earthquakes and natural disasters. These are also more challenging applications than the others since the platform is floating before installing the turbine offshore.

People Also Ask

Why are floating wind farms constructed?

Because there are no obstructions to its route, wind speed and frequency are higher and more steady on the water than on land. Furthermore, being placed far from the coast reduces the visual impact. Another rationale is that construction crews may do most fabrication and assembly work in port before transporting to the offshore site. Towing eliminates installation vessels such as jack-up or dynamic positioning vessels, which fixed foundation turbines require. These costly and scarce vessels lengthen these foundations’ installation times and costs.

How does an offshore wind farm export energy?

Wind farms transport the electricity their transformer station generates via a power line to a distribution substation to the end consumer. Suppose the offshore wind farm is close to the coast. In that case, it can directly transmit the electricity via cable to an onshore substation.

How deep can we build floating wind turbines?

In general, floating wind farms are erected at depths that fixed foundations cannot reach for technical or economic reasons. However, the depth distinction between fixed and floating wind farms is getting increasingly cluttered. Companies can currently install floating platforms between 60 and 300 meters in depth. Studies are underway to extend this range to shallower waters of up to 30 meters or deeper waters of up to 800 meters. However, this is not economically viable at the moment.

Conclusion

The floating wind project is rapidly evolving, and floating wind will play a significant part in its future. The industry is focusing on many platform ideas while evaluating several prototypes.

The resulting designs are unlikely to be universal, as some may be better suited to local electrical consumption and environmental conditions than others. Acteon uses its domain knowledge in engineering, mooring, and maritime installation to service this new and promising business.

Despite these challenges, the potential of harnessing a large portion of the open seas for renewable energy generation remains intriguing. According to the IEA, offshore wind power may someday be able to compete internationally.