• Thu. Jun 30th, 2022

Fewer Parts and Pieces: Rethinking Wind Turbine Construction

By Gary Bills, Regional Director EMEA, K2 Management

As the world prepares to recover from the COVID-19 pandemic, its demand and appetite remains unchanged and continues to grow.

Credit: Gemini Wind Park, Netherlands

The IEA predicts that in 2022 there will be a 4% increase in global electricity demand. With gas prices at an all time high and net zero targets set to reduce dependence on fossil fuels in general, it is more essential than ever that renewable energy is delivered at maximum efficiency.

To do this, we need to increase the pipeline of projects under construction – and fast.

The offshore wind industry will be key in this regard. As part of the call to meet demand, the industry is on a continuous march to get projects built quickly, while ensuring that the levelized cost of energy continues to fall.

Harnessing innovative new technologies and new design techniques is key to reducing construction costs, shortening project timelines and moving towards a more sustainable, lean and profitable industry.

It is through innovation, new technologies and fresh thinking that we will eventually deliver renewable energy projects with greater efficiency.

New construction methods and the potential they offer

Credit: K2

Foundation technologies are a key area where construction process improvements are possible and represent a notable opportunity to build more projects quickly and efficiently.

The foundation represents a substantial part of the development costs of any project, accounting for around 15-20% of total investments. This means scrutinizing the technical and financial implications of planned works, especially as the industry becomes more ambitious in terms of the geographical conditions for which projects are proposed.

Developing in these harsher conditions, where the water is deeper, the seas rougher and the type of soil is more diverse, coupled with larger turbines, means dynamic thinking is needed about the options available when It’s about creating solid and profitable foundations for towers and turbines.

Larger components

A few years ago, a large blade was 45 m long. Now they extend more than double, and the forward trajectory should be wider again. But, as a natural consequence, it is not just the blades of wind turbines that are increasing in size.

Offshore wind monopiles are getting bigger and bigger, reaching deeper waters and becoming the most common type of foundation. We are now witnessing the installation of monopiles over 8.5 m in diameter.

As they increase in size, the technology behind installing them in the ground, and then connecting them to the rest of the turbine, improves. New techniques make it possible to use the monopile foundation in waters now reaching 55 m.

Alternative foundation possibilities

Gravity-based structures were among the first of the foundations used for offshore wind, due to their relatively well-understood function derived from their use in onshore wind. Although they have traditionally been used in shallower waters, they are also expected to be used in deeper waters in the coming years, due to their low production costs.

There are naturally many other structures available, such as jackets and tripods. As the industry develops, a combination of concrete and steel is becoming more common for these structures, expanding the economic benefits of the raw materials involved and making it another notable choice for foundations.

And then there is the fluttering wind. With its growing share in offshore wind power generation, this technology is making a marked transition from experimental fleets to industrial-scale commercial fleets. More than half of the rental areas allocated to Scotwind were for floating projects, showing how the industry can expect significant progress in the commercial scale deployment of floating projects in the years to come.

Removal of transition pieces

New offshore wind turbine designs have created the possibility of building a wind turbine without a transition piece. This steel element connecting the monopile to the rest of the wind turbine was once essential, ensuring that the wind turbine was perfectly aligned. However, this component is no longer a necessity.

Credit: Gemini Wind Park, Netherlands

Technological advances mean that pile drilling is more precise than ever, allowing developers to avoid having to correct misalignment by adding a transition piece to the top of the monopile.

The transition piece also serves as a construction from which secondary steel elements essential for operations and maintenance can be attached, such as ladders and landing stages. But again, these can now be attached directly to the turbine tower, avoiding the need for that extra step in construction and streamlining the process.

Building wind turbines without a transition piece can bring even more advantages in terms of construction speed, cost and environmental friendliness.

First, transportation of turbine equipment and parts – an offshore turbine tower built without a transition piece can reduce the number of trips a vessel has to make, as there are fewer parts. The ship that was previously needed to transport this part of the turbine will no longer be needed.

Although a larger vessel may be required to carry a larger monopile, economies of scale mean this could reduce the number of trips a vessel has to make between ports and offshore wind farms, thereby reducing costs fuel, time and carbon emissions.

In addition, the large diameter flanges used to attach the monopile to the transition piece and then the transition piece to the turbine have significant manufacturing times, sometimes among the longest for turbine parts. By removing the transition piece, there is no need for these additional pieces, which can theoretically be an effective way to gain efficiency in construction time.

Building without a transition piece can also provide lifetime operations and maintenance savings. Removing an entire turbine section eliminates time spent performing maintenance checks and repairs on that section. Although the weight of the turbine will naturally be transferred to other parts, there will be a connection that must be regulated and maintained, which improves safety and, when multiplied across a wind farm, could save considerable time.

Although these are small scale changes, each gain will be valuable as margins are reduced to maximize development.

Time and cost savings for the adoption of new technologies

Note the multiple effect that increases in scale, which then filters down to the monopile. As industry ambitions continue to grow, larger foundations are needed for deeper waters and greater turbine capacity.

Credit: Gemini Wind Park, Netherlands

But although this requires more raw materials, it translates to more power by the amount of steel and raw materials used – because larger turbines in areas with better resources generate more power.

More energy produced means a direct increase in project revenue returns, investor confidence, and continued support for new technologies that help meet these higher energy demands.

The extent to which different designs can leverage resources is also important. Offshore floating wind is a key example of a technology that presents a huge opportunity for the industry. With over 80% of all potential offshore wind energy resources lying in waters deeper than 60m – which is deeper than current fixed-bottom designs can handle – floating wind will be essential to stimulate the growth of the industry.

We must also recognize the advantage of structures, such as gravity foundations, which can be concrete rather than steel. As steel prices continue to be volatile, infrastructure construction techniques that may limit its use, such as building without a transition piece, or not using steel as a primary component, such concrete gravity structures, are likely to gain popularity.

Look to the future with ambition

However, seeking to move faster and at lower cost is not necessarily a recipe for success. This approach should be considered carefully, as cutting costs can be detrimental to meeting demand when not done with sufficient caution.

For example, the ripple of cable issues that continue to plague the industry shows the financial and reputational burden that can come from projects that focus too much on cost reduction.

With the offshore wind market so liquid and the current push to bring more renewable energy projects online, we need to be nimble when it comes to engineering turbine towers and foundations – especially when developers look to deeper waters to access the best resource.

Continuing to innovate, explore new and improve existing development methods by looking at things like monopiles, other foundations and transition pieces means the industry can move faster, lower costs and lower LCOE while making project processes more sustainable.

With over 15 years of experience in the renewable energy sector, Gary is the EMEA Regional Director at K2 Management. After holding various positions in engineering design, business development and consulting, he is now responsible for the commercial activities of the commercial division and business development activities in the EMEA territory.

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