Offshore Wind

Wind Energy Update speaks to Owec Tower’s CEO Bjørn Fjeld about its recent deal with Keppel Corp and key R&D projects that address major wind farm installation cost drivers.

Interview by Rikki Stancich

In the nascent offshore wind industry, Owec Tower’s Quattropods are fast becoming the industry reference for jacket foundations. Featured in the landmark Beatrice offshore demonstrator in the Moray Firth and in Germany’s inaugural Alpha Ventus offshore wind project, Owec Tower’s Quattropods went on to set new records in UK waters, on both the Ormonde and Thanet offshore wind projects.

On the Ormonde project, the Quattropod jackets chalked up a world best for speedy installation, with up to four jackets installed per day, and on Thanet, for the highest number of jackets installed on a single offshore wind project.

And at the end of last year, an Owec Tower designed foundation was built for Alstom's 6MW offshore wind turbine pilot at the Saint-Nazaire shipyard in France.

Such a track record proved too good an opportunity for Keppel Corp to pass up. Snapping up a 49.9% stake in Owec Tower earlier this month, Keppel Corp joins a growing number of major oil and gas players looking to corner a slice of the burgeoning the offshore wind market.

Wind Energy Update speaks to Owec Tower’s CEO Bjørn Fjeld about the recent investment by Keppel Corp, and its strategy for maximising the mileage from this latest cash boost.

Wind Energy Update: Keppel Corp, one of the world’s largest rig and vessel construction and repair companies has taken a 49.9% stake in OWEC Tower. What strategic advantage does the Keppel Corp investment yield for OWEC Tower?

Bjørn Fjeld: It is the financial position that we are coming into that yields the biggest advantage – it gives us the financial strength to pursue our growth plan, to improve our product, to increase our capacity and to increase the overall level of confidence in our product.

Keppel Corp and Owec share synergies; while Keppel views Owec as an entrance into the offshore wind market, the cash injection into Owec will enable us to grow much faster.

We have roughly 22 R&D projects that require a lot of finance and capital. This deal will enable us to start a lot of these projects, which will serve to strengthen our product and give us a head start on the competition.

Wind Energy Update: Which of those R&D projects will you focus on initially?

Bjørn Fjeld: We have gleaned a lot of experience from the four wind farm projects we have worked on to date, and this experience has yielded a lot of new ideas for improving our foundation concept. We have some very concrete ideas on how to improve it.

For example, cabling has been a big issue. We have seen from the insurance companies that 80% of accidents occur during the cable-laying process. When connecting the wind arrays and pulling through cables, a lot of problems occur.

We have identified a solution that will significantly reduce these problems. I estimate that our new design solution will be introduced over the next twelve months.

Wind Energy Update: Is the company expanding its workforce?

Bjørn Fjeld: We are now increasing our engineering staff to meet growing demand for engineering capacity in the years to come, in particular experienced structural Engineers. We are aiming to build up a windpower environment here in Bergen, expanding our area of expertise and increasing our reach in the value chain.

Wind Energy Update: To date, the highest volume orders for OWEC Tower foundations have come from UK projects. Where is Owec Tower likely to see greatest demand for foundations coming from in the next five years?

Bjørn Fjeld: Europe will remain the most important market, and especially Northern Europe, with countries like Germany, UK and France. We are actively looking at the French market and are involved in some of the tenders for the five projects there.

The UK’s Round 3 is important, given that our concept is viable for many projects but even more competitive for those being built further from shore, in deeper waters, using large-scale [5MW+] turbines.

We are also involved in different “new” markets like in Asia where Korea and China are very promising.

Wind Energy Update: How does OWEC Tower’s Quattropod jacket design address the issue of fatigue from wind loading?

Bjørn Fjeld: There are several stages in the design process which lead to a safe and optimised design with respect to fatigue from the wind loading.

The first stage is to create a basic design of the substructure. OWEC Tower has developed an in-house software which, based on site specific data and the preliminary turbine loads, enables our engineers to deliver an optimized jacket, midsection and pile basic design. The software uses simplified methods and has been calibrated based on experience.

In addition we always scrutinize and possibly adjust the results of the software based on our own experience and the project specific challenges. At that stage, the main dimensions of the substructure are defined.

The second stage is to run time domain integrated analysis where both the turbine and the substructure are modelled. The analyses are run such that the whole environmental conditions (e.g. wave and wind) met during the design lifetime are represented. As the number of points to check on the substructure is quite important, it leads to quite demanding computing time analysis.

The last stage is to post process the time domain analysis and check the results based on the chosen design guideline.

In the end what counts is to be able to propose a safe and optimized design at an early stage in the project. This way we avoid expensive iterations with the turbine manufacturer and expensive changes (increase weight) for our clients.

So far the only turbine that has used this foundation is REpower’s. But we have carried out studies for Alstom and Areva’s large-scale turbines (5MW+), among others. We have also designed the jacket which will support the first prototype of the new Alstom wind turbine to be installed soon in France

Wind Energy Update: Why is the Quattropod structure particularly suited to difficult soil types?

Bjørn Fjeld: The foundation is adaptable to all types of soil conditions. In the North Sea, where you generally neither have very hard bedrock or overly muddy conditions, we use driven piles with pre-piling.

But our jacket could also be installed with drilled piles for the hard soils, suction buckets in soft clay or even concrete caisson on sand and hard soils.

In the end, cost is a key consideration and until now driven piles have been the most competitive foundation solution for the soil conditions met in our previous projects.

Wind Energy Update: What design features lend themselves to low-cost, high-volume manufacturing, transportation and installation of the Quattropods?

Bjørn Fjeld: First of all, our midsection is very competitive. The forces from the tower to the jacket are transferred in a very efficient way and has therefore a low weight. We introduced our first midsection concept on Beatrice and improved the concept on Alpha Ventus.

For our last project with Alstom, we introduced a new midsection which is even more competitive. This midsection able us to carry even more loads and is much more fabrication friendly.

Also we are the first to have used pre-pile solution for offshore wind turbines. There is a huge advantage to this approach in that installation is more flexible and can be carried out more quickly. The steel amount on the jacket is also reduced (no pile sleeves). We started doing this on Alpha-Ventus, and after Ormonde we are now doing the same on the Thornton Bank project.

Our jacket designs are made in a way that simplifies the yard work. We aim at reducing the steel weight and limiting the amount of welding. Fitting time are also reduced with our concept.

Now we are in contact with the installation companies and many of them are building and designing new ships based on our jacket design.

As a last comment, I’d like to point out that all the jackets installed in sea for offshore wind until now have been designed by OWEC Tower, so in that respect you can say that our jackets are widely viewed as a sound design.

To respond to this article, please write to the Editor: Rikki Stancich