December 2018

The U.S. offshore wind market is finally heating up. This is evidenced by the likes of Deepwater Wind being acquired by Ørsted — bringing opportunities for the market to scale up — as well as Siemens Gamesa adapting its turbines to U.S. standards and predicting higher revenues for 2019 as it moves into this emerging offshore market.

These moves from offshore wind’s heavy hitters not only signal that it’s time to take the U.S. market seriously, but also that European industry leaders are keen to apply their knowledge and experience in the U.S.

It is important for the success of the market that the likes of Ørsted and Siemens, who are accustomed to established working practices in Europe, have confidence in the ability of the domestic supply chain to support their investment decisions throughout development, construction, and operations. One critical requirement is the availability of proven vessel concepts.

First steps
The journey of the U.S. offshore energy support vessel market started with the launch of Atlantic Pioneer, the first U.S. purpose-built crew transfer vessel (CTV) to service the first offshore wind farm in the U.S., Deepwater Wind’s Block Island. This was a huge milestone for the U.S. maritime sector, and, furthermore, demonstrated its capacity to work with firms “across the pond” to deliver a vessel built to a proven European specification.

However, with more and more wind farms to be developed off the coast of the U.S., the challenge is now to quickly build out a domestic fleet of vessels which meet this same standard, are Jones Act compliant, and build upon lessons that continue to be learned from the European market.

Lessons learned
Technical and operational evolution in the CTV market in Europe has been swift, driven by the increasing demands of the industry when it comes to the core attributes of availability, versatility and safety.

In all wind-energy operations, safety comes first. In light of the reputational impact of a number of documented incidents in the early days of large-scale offshore wind development in Europe, alongside systems such as ISM-approved safety management, building vessels to the stringent requirements of a classification society like DNV-GL, BV, LR, or ABS is one of the most effective safety approaches. This not only ensures that the vessel build is of the highest quality, but also involves rigorous ongoing checks throughout operations to confirm that each individual component is performing as it was from the start.

One of the core attributes of the technical and operational evolution of the offshore energy support vessel is technical availability. In conjunction with the reliability gains that go hand-in-hand with class certification, the most significant development in availability has arguably been the mainstream adoption of round-the-clock shift-based operation. Platform and vessel-based accommodation has improved to support 24-hour rotations, and the capacity to refuel at sea can keep a CTV operational on site for prolonged periods.

Vessel designers are now aiming to hit the “sweet spot” with CTV size, and data and evidence collected from the field suggests that 24-meter boats are best placed to meet the diverse demands of offshore wind support. Vessels of this size can effectively fulfil both crew transfer and logistical requirements in offshore energy operations — they are large enough to carry enough industrial personnel and crew, plus a significant amount of cargo and equipment, while also remaining nimble enough to provide fuel-efficient access to offshore turbines.

Furthermore, CTVs need the capacity to work with other vessels on site, for example with offshore refueling. This need for CTVs to be able to efficiently work with other vessels on site is a particularly important factor for the U.S. market where you often have European built jack-ups and larger vessels moored some way offshore to avoid restriction from Jones Act requirements. Vessel operators therefore need boats that can stay out in the field for long periods, even supporting the overnight accommodation of turbine technicians.

With this extensive experience and knowledge, European offshore wind farm developers and operators know what they want from their vessel support suppliers and are looking to apply the same principles to their operations in the U.S.

Adapting to U.S. offshore environment
There is a lot to gain from taking lessons learned from the mature European offshore wind industry, but substantial opportunities exist for those who can refine and optimize vessels for US market conditions.

In particular, crucial advantages will derive from meeting EPA Tier 4 air quality requirements with bespoke propulsion options, hull and deck designs that stand up to larger Atlantic swells, and the ability to respond to unique development approaches with enhanced logistical support capacity.

The U.S. market has particular interest in the hybridization of offshore wind transportation to reduce the overall carbon footprint of the maritime sector. A repeat build of the Atlantic Pioneer would in fact not be compliant due to ever-increasing EPA air quality standards. An effective approach for meeting this market need is not to drastically redesign the whole vessel or simply replace diesel engines with hybrid ones, but instead to make small, necessary changes to reduce the time spent burning up fuels by making the whole vessel more efficient.

Vessels have typically been built with two 1,400 horsepower engines whereas vessel now can be built with four 700 horsepower engines, achieving the same level of power but better meeting air quality requirements. With four engines of lower power, a vessel is able to operate at lower speeds, turning off two of the engines, leading to lower carbon emissions while either idle or at low speeds. This is particularly beneficial for wind-farm support vessel operators as when the vessel is on the wind farm, rather than traveling between the site and the port, high power operation isn’t necessary.

Additionally, as owners and operators are moving into the U.S. market from Europe, they have worked with vessels with different sized engines, and they know which engine OEM models they prefer. The important thing is to be able to have a vessel design which can be adapted based on operator preferences.

A key difference between U.S. and European waters is the vastly different “sea state.” For example, the East Coast sees longer wave lengths and greater swells than are experienced in the U.K., and vessel hull designs need to take this into account. One way this can be done is with a larger freeboard, meaning the ship deck that is closest to the water is positioned higher, reducing the risk of waves crashing onto the deck in rough seas. This also improves the overall stability and safety of offshore vessels.

Meeting technicians’ needs
Not only do vessels need to respond to operators’ requirements, they also need to respond to the needs of crews and passengers on board.

As the industry grows, there will be an increased need for highly skilled turbine technicians in the construction stage, but also then into the long-term O&M phases. The challenge the market will face here is that, while the U.S. onshore wind market is mature and strong, turbine technicians operating in this market will likely not have offshore experience — and may not have any experience at sea at all.

At the end of the day, turbine technicians aren’t seafarers, and in order for them to work effectively and efficiently construction or repair jobs, they need to feel safe and comfortable when travelling to and from site.

The way in which vessel designers and manufacturers will need to ensure this safety and comfort is to look carefully at the seating and space on board. Larger vessels typically benefit from lower acceleration and less aggressive journeys; however, on smaller boats, the journey can be somewhat rough, and the overall design should accommodate for passengers who may not be experienced at sea.

With the exception of mandatory class/flag sill heights, a boat designed with safety at the forefront would have no steps or trip hazards, with designated walkways, handrails, and safety sliding rails for the purpose of safe, repeatable, effective crew transfer. After all, if wind-turbine technicians feel comfortable and aren’t suffering from fatigue or seasickness as a result of their journey to site, they’re more likely to do a good job.

Turbine technicians are essential to the effective running of an offshore wind project — so it is equally essential that the vessel market meets their needs.

Conclusion
The U.S. is primed to develop its capacity for generating wind power offshore, with U.S. ship yards of the highest quality ready to respond with a supply of safe, reliable and versatile vessels. Naval architects from Europe and around the world are excited to work with the U.S. on developing vessels that best meet the needs of seasoned offshore wind players, having learned best practice and design from operating in maturing and thriving offshore markets.

By taking — and refining — proven vessel concepts, U.S. maritime firms and service providers can de-risk complex projects for international wind-energy investors, developers and operators, ensuring the ongoing success of American offshore wind.

Slowly but surely, the floating offshore wind-energy sector is becoming more important, particularly because of the fact that the number of locations with shallow waters suitable for fixed-bottom foundations is limited. Floating wind is turning into a highly scalable future energy source because the wind resource in deep waters is extensive and offers a significant potential for marine renewable energy development and growth to many countries.

Europe remains the world leader in floating wind-energy installations with the North Sea being the main region for deployment, accounting for 78 percent of the European total, followed by the Baltic Sea, with 14.1 percent. Based on the number of offshore wind projects under construction, WindEurope estimates total European offshore wind capacity will be 24.6 GW by 2020.

Furthermore, Europe is continuously investing in innovative projects and designs aimed at improving the performance, maintenance, and installation of offshore floating wind turbines.

There is Hywind and the simulations models developed by Nielson [1] for integrated dynamic analysis and the role of the effect of pitch-angle control of blades. There is other research done as well into the pontoon-type floating wind turbine [2], aimed at characterizing the dynamic response and at identifying potential loads and instabilities, resulting in significant design modifications.

It is important to mention that, besides leading European industries, there are a couple of serious emerging markets interested in the development and deployment of offshore floating wind power. Between 2017 and 2026, China is expected to install 13 GW (a big part of it in floating solutions), according to the MAKE magazine. The Global Offshore Wind Market Report (Norwegian Energy Partners) points out the capacity of China, Japan, and Taiwan to become global market leaders after 2020.

Latest researches from Equinor emphasize the fact that in the U.S. and Japan, there are only a few sites suitable for bottom-fixed installations since fixed-based wind is not viable in water depths of 60 meters or more. Therefore, floating turbines could be a game changer in these areas by overcoming the engineering challenges of deep-water installations and yield that untapped potential.

The Sector’s Biggest Challenges
Even though progress is clear, all professionals know the industry is still facing significant challenges with the need for appropriate vessels for installation and maintenance, innovative design solutions, and the lack of industry standardization. Weather fluctuations are another significant hurdle, and to fight these, offshore wind installations still need improvement in installation vessels — better navigation, higher crane capacity, and more space.

Since the floating offshore wind turbine is a relatively recent invention, there is still a lot of room for new ideas concerning the way the turbine can be held in place and the entire design of the configuration. Mooring architecture, which has been successful in the oil and gas industry, includes the catenary mooring or the taunt leg. For the platform, the assessment is the same with the development of semi-submersible or spar platforms, which are well known in the offshore industries. These solutions aren’t perfect, and their choice strictly depends on the project’s priorities, including environmental conditions and operating parameters.

Another problem originates from the power grid connection. Integrating large amounts of offshore wind generation to the power system requires solid knowledge and better infrastructure.

Technical advancements
Areas where the most progress was achieved include larger, more effective turbines and improved foundations.

Here are some examples:
• Equinor (Ex Statoil) deployed the first full scale spar buoy off Karmoy Island in 2009. The 5,300 metric ton spar buoy was equipped with a 2.3 MW wind turbine. In 2017, Equinor deployed Hywind Scotland, the first floating pilot wind farm. This project features an important scaling with an 11,200 metric ton spar buoy and five 6-MW wind turbines.
• Ideol deployed earlier this year a prototype based on its damping pool platform, a platform different from all known oil and gas standards such as spar, semi sub, or TLP. Moreover, its mooring system is equipped with innovative synthetic fiber mooring lines, an innovative choice of material for a permanent mooring system.
• At an earlier stage of deployment, Sway has chosen the horizontal axis for its wind turbine. This technological choice, according to Sway, lowers the center of gravity, eases the maintenance, and reduces the spacing between wind turbines.
• Still in a concept phase, Hexicon expects to reduce CAPEX and installation costs by developing floating multi-turbine platforms allowing the increase of power generated per platform.

There are, of course, some hybrid types comprising two or three of the mentioned turbines — for example, the spar floater and tension leg mooring system mix. However, much more advancement is expected in this area.

Despite the different types and configurations, there are, in general, three basic floater types of floating offshore wind turbines:
• The semi-submersible type, moored by catenary lines.
• The TLP (Tension Leg Platform) type, moored by vertical tendons, using buoyancy.
• The spar type, formed as a single deep-draft cylindrical and vertical column.

The biggest challenge concerning the foundation type is cost can quickly increase, and therefore the demand for innovative, cost-efficient, and high-quality solutions is needed. Mooring methods feature a close relationship with the construction performance, and for a successful turbine, performance should be carefully studied. Many tests and observations have confirmed that the mooring method using weights is highly effective in reducing cost.
In general, a floating platform can achieve stability through ballast, mooring lines, and buoyancy. It is important to mention the performance of the turbine is affected by the choice of platform, and every existing concept uses one or a combination of these three primary stability methods.

Clump Weights
Floatgen is the first French floating offshore wind turbine system for power generation in Atlantic waters. The three main objectives of this project are to prove the technical, economic, and environmental feasibility of an EU technology floating system in deep waters, bringing wind-energy applications closer to market in diverse European deep offshore areas, and assessing the expected global generation cost per MWh in a 15-year perspective.

The turbine was submerged in September 22 kilometers off Le Croisic (Loire-Atlantique) and is expected to provide electricity to the 5,000 residents of the city.

Floatgen is kept in place by a mooring design using clump weights designed and manufactured by the European leader in ballast solutions, the French company FMGC. These are the first clump weights in France that have been used in the installation of a floating offshore wind turbine. The solution contributes to the optimization and cost effectiveness of the entire mooring system.

The clump weights are designed to offset the vertical forces against the anchor and restrict the movement of the floating structure. They are available in two models:
• The “distributed” configuration is a set of medium-sized clump weights, distributed over a segment of the anchor line. This configuration optimizes the effectiveness and the cost of the solution.
• The “mutualized” configuration consists of one clump weight, attached to one specific point of the anchor line. This configuration neutralizes the impact of wind and wave on the anchoring line.

However, in the case of Floatgen, the foundry has provided a customized solution, based on the target weight and the available installation means.

The mutualized clump weights, made with EN GJL 200 cast iron, have been connected to the mooring lines with a forged steel insert designed for this purpose. To reach the targeted weight and ensure an easier installation, the clump weights were composed of an assembly of several smaller pieces positioned on the steel inserts. Connected with shackle, the clump weights are hanging to the mooring lines and contribute to the limitation of the tensions on the lines. With this dynamic effect, the FMGC solutions contribute to a reliable and cost-effective station-keeping system.

In Europe — and around the world — all professionals are trying to invest knowledge and resources into technological developments in order to cut costs and make offshore floating wind power function better, faster, and easier. As technology is continuously advancing, costs are dropping, and this trend will hopefully continue, pushing the expansion of future projects.

Europe is, for now, the world leader in the investment and development of offshore floating wind power with greater transparency and understanding of the key factors. Other regions in Asia and North America are expected to follow this trend and take an active stance to shift to renewable and clean energy sources as well.

References
1. (2006, 25th International Conference on Offshore Mechanics and Arctic Engineering, Volume 1: Offshore Technology; Offshore Wind Energy; Ocean Research Technology; LNG Specialty Symposium, Hamburg, Germany, June 4–9, 2006)
2. (Jonkman and Buhl, 2007, Jonkman, J.M. and Buhl, M.L. Jr, (2007) Loads analysis of a floating offshore wind turbine using fully coupled simulation. Proc. of Wind Power 2007 Conference and Exhibition, Los Angeles, California.

Each year in the U.S., new wind-farm developments get built and are placed into production. This process does not happen by accident and includes years of hard work to get to that end. These wind farms have budgets of hundreds of millions of dollars. The risks are high, but then the benefits and rewards can often be even higher.

The greatest risk for any project, including a wind farm, is safety. There is no greater risk and impact to life than the occurrence of a safety incident, and prevention must always remain the highest priority. There is no financial, scheduling, or quality issue that takes precedence over safety. This is the first and highest priority of the construction management team.

Construction phase
Beyond safety, each step of the way, there needs to be checks and balances to ensure the project is on track. This is most important during the construction phase. The construction phase does not necessarily start with the physical activity of turning a shovel of dirt. The process starts in parallel with the middle of the development stages.

When a project has progressed to having secured a site and has selected a turbine model, the next big step is to prepare a request for proposal (RFP) to solicit bids for the construction of the facility. The RFP needs to be inclusive of checks and balances. Typically, these checks and balances take the form of required schedule updates and quality check points. The team must be ready to provide verification of progress to validate invoices and ensure compliance with design. This is vital to the success of the construction phase.

These efforts prior to construction are called the pre-construction services. These services beyond the issue of an RFP continue with the review of the bids resulting from the RFP. This review includes not only an economic evaluation but also an in-depth evaluation and recommendation concerning the responding contractors. In addition, the pre-construction activities also include efforts to ensure that all permitting required for the project is compliant. These permits cover such issues as special-use land permits, as well as power-line and pipeline crossings. There are also environmental permits and studies required, including wetlands, archeological, and avian and bat studies, just to mention a few.

After the award of the construction contract, which normally includes engineering, procurement and construction, (EPC), there are equally important tasks. The team must manage the deliverables from the engineering and procurement stages of the contract. These deliverables include drawings and specifications of equipment and their intended installation. The procurement delivery information is vital to the overall project schedule. All of this transpires prior to that first shovel of dirt being moved.

When it is finally time to move that dirt, wind-farm owners have deployed internal resources for the management of the construction. In other cases, owners have deployed independent services providers to perform the same role. What makes up a comprehensive construction management team is a team that covers overall project management and also specific disciplines. These specific disciplines require specialists that cover the areas of civil, mechanical, and electrical construction.

Civil construction
The civil construction starts with that first shovel of dirt but includes much more. The roads are mostly soil and aggregate and are laid down with the use of water and binders. The civil specialist will use a testing service to verify soil compaction of the roads. It is vital that the roads are able to support the heavy erection crane used later in the project. Next, there is a concrete source, usually a batch plant located temporarily on the job site. Then the foundations are begun, which start as a giant hole in the ground and include large amounts of steel reinforcing rebar and a lot of concrete. The civil specialist is responsible for tracking all slump tests, concrete, and grout-break test results to ensure compliance with specifications. After the foundations are completed, the remainder of the project requires ongoing road and drainage improvements and dust control as the roads get used.

Mechanical construction
The mechanical construction mostly relates to the wind turbine itself. This can start with the review of the delivered components. This is an important first step in identifying any issues from manufacturing and/or shipping. The mechanical specialist will document any issues found and work with the manufacturer to resolve those issues. The main emphasis of the mechanical scope is the erection of the unit and the eventual internal completion of the wind turbine.

The erection process is critical, paying close attention to initial bolted connections and their eventual torque and tensioning specifications. The myriad of mechanical connections within the unit requires detailed work instructions and procedures to ensure the wind turbine is fully assembled in accordance with the manufacturer. Finally, the walkdowns done by the mechanical specialist will ensure that the tower, blades, pitch, yaw, and brake systems are installed and functioning correctly.

Electrical construction
The electrical construction covers areas outside as well as inside the wind turbine. The collection system includes the connecting cabling between each turbine and a longer final run from the end of a string of turbines to the substation or switchyard. The collection systems can be installed either above ground or underground. In either case, the electrical specialist will ensure that the collection system is constructed, installed, and terminated in accordance with the drawings and industry standards. Many wind turbines require a small step-up transformer near the base of the turbine. These transformers also must be installed and terminated in accordance with drawings and standards. Finally, the electrical specialist will ensure that the wiring to be installed and connected within the turbine is compliant.

The project can also include substations and switchyards. The team applies the same principles to the construction of these facilities as they applied to the wind farm. There are many high voltage industry standards that must be met, and this is the direct responsibility of the electrical specialist. The specialist will verify that all relay testing is completed and that the results support the design for isolation of events and protection of equipment. The electrical specialist is also focused on the DC battery system installed in the control house and will verify it is tested and compliant. The electrical specialist is usually aided by the civil and mechanical specialist to cover foundations and building inspections.

Some projects also include high voltage transmission line construction to connect the new wind farm to the actual point of interconnect with the transmission grid. This is again a responsibility of the electrical specialist to provide inspection and verification services. The transmission line structures need to be inspected as they are received and then installed. The cabling is measured and documented in its stringing sag report and would be verified as compliant by the electrical specialist. In this area, there may be concrete used to support the structures, and if so, the civil specialist would support this effort as well.

O&M buildings
The O&M buildings are often not given the attention they deserve, as everyone is so focused on the wind farm power generation and distribution equipment. The O&M building usually houses the technicians, spare parts, and the main computer control system for the wind farm. All of these items are equally important to inspect and verify. The O&M building also would receive the same three-disciplined approach to management: The civil specialist will oversee the excavation and foundations; the mechanical specialist will monitor the HVAC systems and associated equipment. Lastly, the electrical specialist will watch over the rest from an electrical perspective.

The meteorological mast, also known as the met mast, is usually the most forgotten equipment on a wind farm. The met mast also has requirements for proper installation. All three disciplines will be involved, civil for the foundation, mechanical for the erection, and electrical to get it all connected. This can be more critical than one might think. If the data stops flowing from the met mast during production, the wind farm can suffer a curtailment until such time that the data flow is reinstated.

All of this pre-construction and construction management is quite an undertaking. All of the work must be in accordance with engineering design, manufacturers’ instructions, and industry standards. This is not to be taken lightly.

Alternative planning
The members of the construction management team not only ensure quality of the construction, but they also are the planners for alternatives when things do not go according to plan. Late delivery of major components can be the most common delay for a wind farm. It is the responsibility of the construction management team to develop workaround plans to keep the project on schedule.

An owner must watch over the construction of the wind farm to protect their interests and the interests of the investors. As stated prior, some owners have the sophistication to manage the construction and others use a third-party independent service provider. Either way, it is recommended that the construction phase from pre-construction to the first day of operations needs to be managed by a professional team and not left to self-management by the EPC contractors. Either way, the cost for a construction management team equates to less than 1 percent of the overall project cost. This is money well spent.

Some people don’t supervise contractors working on their home, please don’t let that happen on a wind farm. Remember, there is no greater issue to be concerned with than safety; everything else is secondary.