How Are Wind Turbines Made At Sea?

Except for a few extant offshore wind turbines, all are supported by a fixed foundation, which is typically a huge steel tubular pile that connects to the turbine mast above the seabed. Fixed-bottom turbines can only operate in water depths of 50 or 60 meters.

However, recent initiatives such as Hywind off the coast of Scotland and Windfloat off the coast of Portugal have demonstrated that floating wind turbines can be built. A single six megawatt turbine, such as those used in the Hywind farm, can power 4,000 UK houses.

However, providing similar residential electricity for a global population of 9 billion people by 2050 would necessitate half a million offshore wind turbines a 100-fold increase from current levels as well as additional capacity to meet future energy demand.

While floating wind farms are theoretically conceivable, they are not commercially feasible. Anything done overseas is costly. The cost of conducting the requisite site survey for a one gigawatt fixed-bottom wind farm is in the region of 15 million. The farm’s installation and commissioning expenses would be around 650 million, with annual operating and maintenance expenditures of around 75 million. Decommissioning will cost another 300 million at the end of its life, which may be over 25 years.

Floating wind farms, on the other hand, are even more expensive because they are still in the early stages of design and technology. While the cost of supplying offshore wind energy in 2019 was between 36 and 45 per MWh of electricity, floating wind auctions are now costing more than twice as much.

Offshore buildings can also be rather large. The 154-meter-diameter blades of the Hywind six-megawatt turbines are the same length as an A380 plane’s wing span. The rotor diameter of the Siemens Gamesa 10 megawatt turbine is 193 meters, while the rotor diameter of the US National Renewable Energy Laboratory 15 megawatt reference turbine is 240 meters. Building, installing, running, monitoring, maintaining, and dismantling large-scale infrastructure in the water is no easy undertaking.

While energy corporations frequently construct offshore oil and gas rigs, a single floating wind turbine produces significantly less electricity. It might be 1,000 times less throughout the course of its operating life, depending on the size of both structures. As a result, far more infrastructure is required to produce the same amount of electricity from renewables. To equal the cost of energy generation from offshore oil or gas, putting an offshore wind turbine out at sea and keeping it there must become a lot cheaper.

Traditional offshore engineering can teach us a lot about how to make the shift to renewable energy. However, doing more of the same or improving the effectiveness of existing processes and technology will not result in the necessary cost savings.

What goes into the construction of offshore wind turbines?

In 2016, wind power accounted for 11.5 percent of total energy output in the UK, surpassing coal for the first time, which accounted for 9.2 percent (3).

The majority of wind power electricity generated in the UK, however, comes from onshore turbines. Only 27 operating offshore projects with 1,465 turbines (21 percent of total) are operational, compared to 1,088 operational onshore projects accounting for 79 percent of total turbines (2).

Offshore wind power might be a good place to start if you want to boost your energy generation. One example is E.ON’s upcoming Rampion Wind Farm, which will include 116 turbines with a total generating capacity of 400MW and will be built off the Sussex coast near Brighton (4). Rampion will provide electricity to 290,000 houses, or more than 4 out of every 10 Sussex families (5).

How do you put a wind turbine out in the middle of the ocean? That was the question I wanted to know the answer to. The engineering challenges of installing a turbine at sea have resulted in the development of specialized machinery and novel construction procedures.

The wind turbine itself is built from a kit on the beach. The turbine is built in pieces, with the base (seat), tower sections, nacelle (which houses the generator), and turbine blades being the most important ones. Out at sea, these components, like a model kit, can be put together to form the turbine.

On special seajacking ships, these turbine components are transported and installed out at sea. These are specifically designed to jack themselves out of the water in order to create a sturdy platform for precision lifting. The ships also have hydraulic rams, which are used to install the turbine foundations, in addition to a high-performance crane.

A monopile is utilized to attach the turbine to the seabed in the Rampion Wind Farm. A monopile is a steel cylindrical tube with a 150mm thick steel skin and a diameter of up to 6 meters. Due to its ease of installation in shallow to medium depths of water, monopiles are one of the most prevalent foundation designs in offshore wind building. A specialised hydraulic ram piles the steel cylinder into the seabed.

After the monopile has been anchored to the seabed, a transition piece (also known as chairs) is installed on top. The transition piece is carefully lowered into place and secured because it is responsible for connecting the turbine and the monopile. The transitional piece is typically brightly colored and features a boat mooring stage with a ladder leading up to the work platform for technicians.

The turbine tower, which is craned into place and put together, is the following step. The nacelle is joined to the top of the tower and the generator is connected once all of the tower sections are connected. The next step is to connect each turbine blade to the nacelle’s hub. The pitch angle and yaw of the blades can be modified once the turbine is fully constructed to optimize the turbine’s performance. The offshore substation, which feeds into the National Grid, is then connected to each wind turbine.

Siemens created this animation to walk you through the installation of an offshore wind turbine.

Is it true that there are wind turbines in the ocean?

Fixed foundations are uneconomical or technically impossible at depths of more than 6080 meters, hence floating wind turbines attached to the ocean floor are required. The world’s first floating wind turbine was installed in 2007 by Blue H Technologies, which was later acquired by Seawind Ocean Technology. Hywind is the first full-scale floating wind turbine in the world, having been erected in the North Sea off the coast of Norway in 2009. The first operational floating wind farm, Hywind Scotland, was commissioned in October 2017 and has a capacity of 30 MW. Other types of floating turbines have been installed, and more are in the works.

What is the procedure for repairing wind turbines in the sea?

How do these turbines keep in place at a height of 113 meters (370 feet)? Elevating the turbines while attaching them to the seafloor is the most difficult phase. A steel cylinder known as a monopile is fastened to the sea bed up to 15 meters and buried up to 30 meters deep. A gravity foundation is employed at a depth of 30 meters in the ocean. This foundation is made up of a “huge concrete or steel platform with a diameter of around 15 meters and a weight of approximately 1,000 tons,” according to Iberdrola. Deeper installations can be produced with the use of a jacket or a foundation with a lattice framework, similar to an antenna tower, with three or four legs anchored to the bottom. Of course, depending on the type of foundation, the composition of the seafloor must also be considered.

What are the materials used to construct offshore wind turbines?

Steel is the most common material used in turbine constructions, but fiberglass (and carbon fiber), resin or plastic, iron or cast iron, copper, and aluminum all play a role. By 2025, 12,000 offshore wind turbines will be erected around the world, requiring 3.5 million tonnes of steel for foundations.

Who manufactures offshore wind turbines?

GE is a global leader in offshore wind energy, with a portfolio of offshore wind turbines ranging in size from 6 MW to 14 MW that provide customers with greater value via proven performance, reliability, efficiency, and availability.

We can supply the offshore wind farm solutions you need, with cutting-edge offshore wind farm technology to modernize your fleet, full offshore wind services support to keep your turbines running smoothly, and our Digital Wind Farm to make our turbines even smarter and more connected.

What is the lifespan of an offshore wind turbine?

A modern wind turbine of acceptable quality will typically last 20 years, however this can be extended to 25 years or beyond depending on environmental circumstances and proper maintenance practices. However, as the structure ages, the maintenance expenditures will rise.

How are offshore wind farms able to stay afloat?

  • A spar buoy platform is a long hollow cylinder that extends from the turbine tower downwards. It floats vertically in deep water, its center of gravity being lowered by ballast in the bottom of the cylinder. It’s then moored in situ, but with slack lines to allow it to move with the water and avoid being damaged. For years, the oil and gas sector has relied on spar buoys for offshore operations.
  • Large floating hulls radiate out from the tower of semi-submersible platforms, which are also tethered to prevent drifting. On several of these hulls, designers have started experimenting with numerous turbines.
  • Smaller platforms with tight lines flowing straight to the floor below are known as tension leg platforms. Because they rely more on mooring lines and anchors for stability, they are lighter yet more vulnerable to earthquakes and tsunamis.

Each platform must be able to hold the turbine’s weight and stay stable while it is in operation. It can do so in part because the turbine is supported by a hollow platform, which is frequently composed of huge steel or concrete constructions.

Fixed-bottom structures, which require specialised boats for installation on site, may be significantly more expensive than those that can be fully assembled in port and towed out for installation.

Wind turbines with a capacity of 10 megawatts or more can be supported on floating platforms, which is comparable to other offshore wind turbines and several times greater than the capacity of a typical onshore wind turbine found in a field.

Why do we need floating turbines?

Off the coast of the United States, the Great Lakes, the Mediterranean Sea, and the coast of Japan, some of the strongest wind resources are offshore in sites with hundreds of feet of water below.

Interior Secretary Deb Haaland and California Governor Gavin Newsom announced plans to open up areas of the West Coast for offshore wind generation in May 2021, along the coast of central California’s Morro Bay and near the Oregon state line. Because the sea there is shallow, any wind farm even a few miles from the shore will require floating turbines.

According to Newsom, the land may supply 4.6 gigawatts of clean energy at first, enough to power 1.6 million households. That’s more than 100 times the current amount of offshore wind power in the United States.

Several full-scale demonstration projects across Europe and Asia are already operational.

With five 6-megawatt turbines supported by spar buoys manufactured by Norwegian energy company Equinor, the Hywind Scotland project became the first commercial-scale offshore floating wind farm in 2017.

While floating offshore wind farms are becoming a viable commercial option, there are still technical hurdles to overcome. Higher forces on the blades and tower, as well as more intricate and unsteady aerodynamics, may result from platform motion.

Furthermore, when sea depths get deeper, the cost of mooring lines, anchors, and electrical cabling may become prohibitively expensive, necessitating the use of less expensive but still reliable technology.

In the near future, expect to see additional offshore turbines supported by floating structures.

Matthew Lackner is a mechanical engineering professor at the University of Massachusetts Amherst.

The Conversation has given permission to republish this article under a Creative Commons license. Read the full article here.

What is the depth of wind turbines in the sea?

Floating wind turbines are moored to the seabed by mooring lines, whereas most offshore wind turbines are anchored to the ocean floor on fixed foundations, limiting them to depths of roughly 165 feet. These massive buildings are built on land and then towed out to sea by boats.

What is the depth of foundations for offshore wind turbines?

Offshore wind turbines, which are anchored to the seabed with monopile or jacket foundations, can only operate in waters less than 50 meters deep. This eliminates sites with the greatest winds and, in many cases, easy access to large markets.

What is the height of an offshore wind turbine?

The hub height of a wind turbine is the distance from the ground to the center of the rotor. Since 19981999, the hub height of utility-scale land-based wind turbines has climbed by 59%, to around 90 meters (295 ft) in 2020. That’s around the same height as the Statue of Liberty! In the United States, the average hub height for offshore turbines is expected to rise even higher, from 100 meters (330 feet) in 2016 to around 150 meters (500 feet) in 2035, or roughly the same height as the Washington Monument.