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The Challenging Future Of Floating Wind Farms

Illustration of a floating offshore wind farm courtesy Damen

The Challenging Future Of Floating Wind Farms

John Konrad
Total Views: 2875
July 6, 2023

by John Konrad (gCaptain) Far offshore, in the limitless expanse of the ocean, where the wind conducts the rhythmic ballet of the waves and the horizon stretches into the infinite, a new lineage of titans is being conceived. These are not the mythical leviathans of ancient seafarer’s tales, but the trailblazers of a sustainable future – floating wind turbines. Engineers envision these to be towering structures, reaching hundreds of meters into the sky, perched atop colossal floating platforms, anchored in the profound abyss of the sea, to seabeds thousands of feet beneath. Crafted to withstand the harshest marine conditions, these floaters promise to deliver unwavering, zero-emission energy. However, the construction of such stability presents significant challenges, including the mobilization of vast manpower, the procurement of substantial materials, and the deployment of an immense quantity of steel. This will require a scale of ambition larger than the towers themselves.

Today the vast majority of offshore wind turbines are built on foundations resting firmly upon the seafloor. These bottom-fixed turbines stand high as sentinels in the ocean, harnessing the power of the wind. This approach has been favored due to its stability and the relative ease of installation in shallow to medium-depth waters, and relatively short transmission line distances to shore. However, as we venture further from the shore, into deeper waters where the winds are stronger and more consistent, the limitations of bottom-fixed turbines become apparent. The cost and complexity of installing fixed foundations increase significantly with water depth, making them less feasible for deepwater locations. This is where floating wind farms come into play.

Floaters can be located in areas of high wind potential, in thousands of feet of water (for comparison Perdido, Spanish for lost, is the deepest floating oil platform in the world and is capable of anchoring in 8000 feet of water), reducing visual impact and potential conflicts with other marine uses. Experts believe that these floating leviathans of the sea represent the future of offshore wind energy, promising a new era of sustainable power generation that can tap into the vast wind resources of the deep oceans.

The Hywind Scotland and Kincardine pilot projects, trailblazers in this new frontier, each command an army of five floaters. Their combined might? An impressive 80 MW. But this is merely the introductory chapter. Envision a 1 GW floating offshore wind farm, energized by the largest commercially available 15MW turbines. To realize such a venture, we would need an armada of no less than 67 of these gargantuan foundations, or a smaller number of massive floaters would have to support much larger turbines.

Also Read: Equinor Begins Power Production at Hywind Tampen, Norway’s First Floating Offshore Wind Farm

The industry is locked in a race against time, innovating and experimenting with various floater designs. Some are opting for concrete over steel, as exemplified by the Hywind Tampen project. However, the future seems to favor steel, with the majority of the floating offshore wind farms in the coming years expected to be steel-based. The steel requirement for each floater is estimated to be twice that of monopile foundations for bottom-fixed wind farms. This implies that managing a floating wind project’s capital expenditure will necessitate large and cost-efficient fabrication capacities, likely situated far from the installation sites in Europe or the US.

Why this insatiable demand for steel? The answer lies in the realm of physics.

Three of the common types of floating wind turbine platforms. Josh Bauer/NREL

Picture these turbines as towering giants, their heads piercing the sky, their bodies plunging into the depths of the sea. They stand tall, like a lever arm, with the wind exerting its force high up at the turbine’s shaft. This scenario is reminiscent of a child on a seesaw, pushing down on one end with all their might. The turbine, like the seesaw, experiences a torque, a rotational force that threatens to topple it.

Beneath the surface, the floater serves as a counterbalance, akin to the leaded keel of a sailboat. It provides a low center of gravity, helping to keep the structure upright. But this is only part of the solution. The wind, relentless and powerful, pushes against the turbine, threatening to displace it from its location.

This is where anchors or tension legs – connected via thick cables – come into play, serving as the roots of these sea giants. They dig deep into the seabed, holding the turbine in place, much like the roots of a tree gripping the earth to withstand a storm. These anchors or tension legs counteract the force of the wind, preventing the turbine from being pushed off its location.

Consider a kite flying high in the sky. The string of the kite, held firmly by the flyer, acts as the tension leg. It keeps the kite from being carried away by the wind. Similarly, the anchors or tension legs of the floating wind turbine hold it steady against the force of the wind.

However, the challenge is far from simple. The forces at play are immense, and the balance is delicate. Too much tension and the structure risks damage. Too little, and the turbine could drift off location. It’s a dance with the elements, a delicate waltz between the forces of nature and the principles of physics. A waltz performed not by ballerinas but Olympic weightlifters.

Building A Support Fleet

dominion energy wtiv
An illustration of the Dominion Energy’s Wind Turbine Installation Vessel (WTIV) currently under construction at Keppel AmFELS in Brownsville, Texas. Illustration courtesy Dominion Energy

The challenge of long-range, deep-sea transportation is a critical one. Companies in the offshore wind sphere are grappling with how to transport hundreds of foundations or sub-parts in a timely and efficient manner. The fleet of suitable vessels is limited, and these vessels are already being used in other competing markets. To limit the requirement of very large and expensive transportation vessels, several companies are offering floater designs that can be transported in pieces and assembled at a site close to the installation.

The future of floater designs will be heavily influenced by manufacturing and transportation questions. We might see new vessels dedicated to floaters or floater component transportation, similar to the recent emergence of freighters dedicated to the transportation of wind turbine components.

Building the navy of support vessels required for floaters will also require large shipyards and a lot of steel.

The operation of ports is another crucial aspect. Bottom-fixed wind turbines are assembled on pre-installed foundations by Wind Turbine Installation Vessels (WTIVs). For floating wind farms, turbines are installed on their floaters by massive floating cranes in sheltered areas close to shore and then towed out at sea. This requires large onshore and offshore storage areas, tugs, barges, and relevant moving and lifting assets.

The developers of floating wind farms will need to compete for port access. They will need to secure large storage areas for wind turbine and floater components, and large offshore storage areas for floaters waiting for turbines to be installed. They will also need to secure tugs, barges, and relevant moving and lifting assets.

This infrastructure with requires not just land but massive amounts of concrete, machinery, and steel.

The industry is still grappling with the challenges of port operations. Some companies are investigating the concept of temporary “floating ports” that could be mobilized in shallow waters closer to the wind farm site. These could be relocated and reused for future projects but will also require massive amounts of steel and materials to construct.

Durability and Design

WIND TURBINE SMOKE TEST AT PLUM BROOK PB
WIND TURBINE SMOKE TEST AT PLUM BROOK PB. Photo via NASA

The sea, in all its majestic grandeur, is a realm of relentless forces. It is a world where saltwater gnaws at metal, where winds howl with unyielding ferocity, and where waves crash with the power of a thousand hammers. In this harsh and unforgiving environment, our floating wind turbines would stand as defiant sentinels, their survival a testament to human ingenuity. Yet, their existence will be a constant battle against the elements.

The longevity and reliability of these structures are paramount, but achieving this is no small feat. The corrosive saltwater, the battering winds, and the relentless waves all conspire to wear down the turbines and their components. Regular maintenance is the shield against this onslaught, a necessary ritual to ensure their continued operation.

Yet, the task of maintenance is a complex dance with the elements. The turbines stand in remote locations, far from the comforting shores, making them difficult to access. The logistics of this task are akin to the challenges faced by the oil and gas industry in their deepwater construction projects. The costs, both financial and logistical, are substantial, but they are the price we pay for harnessing the power of the wind in the vast expanse of the sea.

The other shield is engineering durability into the design, this is effective but requires the use of expensive metals and high-end components.

Offshore Weather

The open sea, with its consistent and powerful winds, is a stage set for the performance of our floating wind turbines. Yet, this stage is not without its perils. The sea can transform from a calm expanse to a raging tempest in the blink of an eye. Storms and hurricanes, the titans of weather, pose a significant risk to the integrity of the turbines.

Designing structures that can withstand these extreme conditions is akin to building a fortress that can stand against a siege. It is a formidable task, one that requires a deep understanding of the forces at play and the resilience to match them.

The offshore industry has faced similar challenges, with hurricanes causing significant damage to oil and gas platforms. The cost of insurance and the downtime required for repairs can be substantial. A floater, damaged by a storm, is not just a loss of a valuable asset, but also a pause in the symphony of energy production.

Yet, these challenges are not insurmountable. With careful design, robust construction, and diligent maintenance, our floating wind turbines can weather storms but repairs made to damaged structures will require additional materials in addition to what is required to build wind floaters.

Grid Connections

New Power Lines to Restore Electricity in Mayaguez
New Power Lines to Restore Electricity in Mayaguez. Photo via dvidshub

In the grand symphony of sustainable energy, the floating wind turbines play a powerful melody. Yet, at least in maritime industry conversations, we tend to forget this melody needs to be carried from the heart of the ocean to the homes and industries on land. This is where the challenge of grid integration comes into play.

Imagine the energy produced by the turbines as a mighty river. This river needs to flow from the turbines to the power grid. To carry this river of energy, we need undersea cables, the arteries of our power system. These cables need to be robust and efficient, capable of transmitting large amounts of electricity over long distances.

The task is akin to building a bridge. The bridge needs to be strong enough to carry the weight of the traffic, yet flexible enough to withstand the forces of nature. The materials used in the construction of this bridge are crucial. Concrete forms the foundation, providing the stability needed to withstand the forces at play. Copper, with its excellent conductivity, forms the core of the cables, carrying the electricity from the turbines to the grid. Steel provides the strength and durability, protecting the cables from the harsh marine environment.

Yet, the challenge doesn’t end here. The wind, in all its power and glory, is an intermittent source of energy. It ebbs and flows, rises and falls, much like the waves of the sea. To ensure a consistent supply of power, we need effective energy storage solutions.

Energy storage is like a reservoir. It collects the excess energy produced during periods of high wind, storing it for use during periods of low wind. The design and construction of these storage solutions require a variety of materials, including some rarer metals. These materials, are not as abundant as concrete, copper, or steel, but are crucial to the efficient storage of energy.

The conundrum of energy storage also looms large. Should the batteries be housed on terra firma, enjoying the stability and accessibility of land? This option, while advantageous in many respects, would necessitate the installation of extensive subsea transmission cables, a significant undertaking. Alternatively, should the energy be stored at sea, reducing the need for such subsea infrastructure but introducing its own set of challenges? The hazards associated with battery storage, particularly the risks of fire and explosions, are already a complex issue for power utilities on land. These concerns are amplified when projected onto the vast, remote canvas of the sea, far from the reach of fire engines and HAZMAT trucks. The question of where to store the energy harvested by these floating titans is a puzzle that remains to be solved.

In the grand scheme of things, the amount of these materials required is substantial. Yet, it is a necessary investment, a price we pay for the promise of a sustainable future. With every ton of concrete poured, every meter of copper and steel cable laid, and every unit of energy stored, we move one step closer to our goal of sustainable floating energy.

Blades On The Cutting Edge

WIND TURBINE BLADES
WIND TURBINE BLADE TESTING, Photo Via NASA

At the leading edge of this melody, the start of each watt of energy produced is the relentless dance of the blades. These blades, sweeping through the air, harnessing the power of the wind, are the heart of the turbine. Yet, they too have their own tale to tell, a tale of creation, of service, and of retirement.

The life of a wind turbine blade begins in a factory. Here, they are crafted from a cocktail of materials, primarily fiberglass reinforced with balsa or foam. The process is meticulous, requiring precision and care. The blades must be strong, to withstand the relentless forces of the wind, yet light, to spin with ease. The resources required for their creation are substantial, a testament to the complexity of their design and the importance of their role.

Once created, these blades embark on a journey to their destined turbines. The logistics of this journey are a challenge in themselves. The blades, often over 50 meters long, require special transportation and careful handling. They traverse roads, seas, and sometimes even the skies, to reach their new homes on the turbines.

In service, these blades dance with the wind, spinning tirelessly, day and night. Yet, this dance takes its toll. Over time, the blades wear down. The relentless wind, the harsh sun, and the corrosive sea air all conspire to degrade the blades. Typically, after about 20 years, the blades need to be replaced.

The task of replacing these blades is a delicate ballet of precision and skill. Large cranes and skilled technicians are required to remove the old blades and install the new ones, a problem made even more difficult when the generator is located far at sea. The old blades, once the heart of the turbine, are now a challenge in themselves.

One advantage of floaters is they would potentially be disconnected from the seafloor and towed into a repair shipyard where each component could be inspected and reconditioned. This might occur but the challenges of disconnecting and moving a giant floater, and the downtime required as the rig is overhauled, means that blade and turbine replacement might happen offshore.

Then you have the problem of waste. Recycling these blades is not easy. The very properties that make them so effective – their strength and durability – also make them difficult to break down. Currently, most wind turbine blades end up in landfills, a far cry from the sustainable vision they once represented.

The environmental impact of disposing of these blades is a growing concern. The sheer size of the blades means that they take up a significant amount of space. Furthermore, as more turbines reach the end of their service life, the number of blades needing disposal is set to increase.

Yet, in the face of these challenges, the industry is innovating. New methods of recycling are being explored, with the aim of repurposing the blades into new products. Some companies are investigating ways to use old blades to create everything from bridges to car parts. With innovation and determination, the industry is continuing to look for new ways to ensure that the dance of the blades is as sustainable as the energy they produce.

Challenges Ahead

offshore wind farm with vessel in foreground
Stock Photo: Ian Dyball/Shutterstock

As we stand on the precipice of a new era of sustainable energy, the floating wind turbines are not just a testament to human ingenuity and our ability to harness the principles of physics. For some, they are also a beacon of hope, a symbol of our commitment to a sustainable future. Yet, this future is not without its challenges.

The sea, in all its majestic grandeur, is a realm of relentless forces. It is a realm where saltwater gnaws at metal, where winds howl with unyielding ferocity, and where waves crash with the power of a thousand hammers. In this harsh and unforgiving environment, floating wind turbines will stand as defiant sentinels, their survival a testament to human ingenuity. Yet, their existence is a constant battle against the elements.

The logistics of constructing these titans, transporting them to their locations, and maintaining them in the face of the relentless sea, are immense. The materials required – concrete for the foundations, copper, and steel for the cables, and a variety of rarer metals for energy storage – are substantial. These are the necessary investments we must make, the prices we must pay, for the promise of a sustainable future yet it would be foolish to start without an honest assessment of cradle-to-grave cost. We must also consider the opportunity costs and the feasibility of alternatives like floating nuclear power stations.

The floating wind turbines, in all their grandeur, are a symbol of our commitment to this future. They promise to stand tall against the relentless forces of nature, harness the power of the wind, and lead the way towards a cleaner, greener future. The challenges are many, and the voyage is fraught with difficulties, but many believe the destination is worth every effort. For in the heart of the ocean, where the winds whip up waves and the sea stretches out to the horizon, a new breed of giants is taking shape, expensive and complicated energy sentinels that promise a future powered by the wind, by the sea, by the relentless forces of nature.

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