Gwynt y Môr – Building an offshore wind farm

For Energy Engineering magazine


Constructing an offshore wind farm is no easy task. That might appear to be stating the obvious but the scale of the challenge can be underestimated by government, the finance community, the public, and even on occasion the industry itself.

Take Gwynt y Môr for example: development of the site (which lies 16km off the coast of North Wales) was first mooted in 2003 but it was a decade later, August 2013, before the wind farm began generating to grid and as this issue went to press construction is ongoing with the installation of the final array cables.

Nevertheless, the fact that the 576MW development is close to full commissioning vindicates the hard work of the project team. Over ten years the developers have had to deal with adverse conditions, both in terms of the offshore weather and political support in Westminster, yet project director Toby Edmonds is convinced that the investment of time, money and energy has been well worth it and that construction has provided an invaluable learning process as the offshore wind sector looks to industrialize in an effort to reduce the cost of energy.

The project’s primary developer RWE was granted the zone in The Crown Estate’s Round Two offshore wind leasing round (2003) but it was 2005 before a consent application was submitted. “We had to do a lot of studies on and off shore,” explains Edmonds. “We needed to secure all the land for the cable route and substation location; get the grid connection agreement from National Grid; and then get permission via a public enquiry. The determination by the Secretary of State took nearly two years but in 2008 we achieved consent.”

The Crown Estate had granted RWE development rights for the Gwynt y Môr zone up to a capacity of 750MW. However, it was decided for a variety of reasons including logistical and electrical efficiency to scale down to a 576MW capacity. Even taking into consideration the reduction in target capacity this was still a massive project, unprecedented in scale at the time of consenting. To share the €2 billion investment required, RWE pursued project partners bringing on board Siemens (a 10 per cent stake) and Stadtwerke München (a 30 per cent stake).

With finance in place, the installation of a met mast in 2009 signalled the start of construction proper. Onshore activity continued through 2010 with the preparation of the grid connection and the construction of the onshore substation. It was January 2012, seven years after the consent application was submitted, when offshore construction commenced.

Described by Edmonds as a “sequential activity” offshore construction progressed from the seabed up. “We started by preparing the seabed for the monopile foundations,” says Edmonds. “In some cases we had to put scour protection down. Then we moved straight into foundation installation: we had 160 monopile foundations to install – a huge amount of steel and work.”

Foundation installation continued until its completion in April 2014. During this period work continued in other areas including onshore activities and the installation of the offshore substation. Turbine installation (Siemens 3.6MW turbines) commenced in May 2013 and was carried out by the A2SEA vessels Sea Jack and Sea Worker – the last of the 160 turbines was installed in June 2014. “With offshore wind farms it is all about the planning,” comments Edmonds. “The actual execution can be extremely fast. We had two vessels on the project and we could put up five turbines in a week given the right conditions.”

The wind farm began generating power to the grid in August 2013 and at the current moment is moving ever closer to full operations as the final array cabling is completed.


Reflecting on the experience of the last decade Edmonds explains that huge lessons have been learnt. “The industry is developing at a rapid pace and we’ve learned an awful lot about offshore wind farms,” he says. “One key development has been the level of sophistication we now work at in logistics. Every second counts offshore. We are repeating each exercise 160 times, so if you save an hour or even five minutes each time that can save a considerable amount of money. The cash burn on these projects when you are in full construction is huge so saving 15 minutes off 160 operations could save £1 million.”

Working offshore, weather conditions were inevitably a complicating factor. “Most people’s memory of the summer of 2013 will be as a fantastic one, but April and May were worse than average and there was some shocking weather in September and October with a lot of storm systems coming through,” recalls Edmonds. “We work through the winter despite the increased downtime because starting and stopping is very expensive. What is amazing is that vessels might only need a four-hour window to make progress on the project and the quicker we build the less these projects cost.”

As has been the case for several offshore wind developments, cabling has proved a particularly challenging stage of the Gwynt y Môr project. “We’ve got four large export cables, two to each substation, which are all in. Now we are dealing with array cable installation. That’s been tricky for us as there are some challenges in that area,” says Edmonds. “Our ambition is to have a diverless process but there will always be some need for intervention. If you imagine you are trying to take a cable and bury it in seabed in continuous operation it is technical and challenging.”

With a number of Round Three projects entering the early stages of construction developers are looking to the experience of Round Two zones in considering how the offshore wind sector might industrialize its processes. “When we built Rhyl Flats [a Round One 90MW wind farm commissioned in 2009] it took six months to install 25 foundations, on this project it took six weeks to do 25,” comments Edmonds. “We are operating at a different level compared to the past. Everything is becoming much slicker and that speed is what saves you the money.”

He continues: “The whole process has been optimized through continuous improvement to drive out downtime. The market is moving towards a model of being paid per activity rather than for a vessel and crew’s time and that incentivizes fast and efficient performance.”

Edmonds predicts continuing improvement in the speed of installation (of foundations, turbines, and cables) and the standardization of design of offshore platforms.

Whilst the Gwynt y Môr offshore wind farm employs 3.6MW turbines, larger turbines (up to 7MW) are now available and this will have a significant impact on the industry. “Quality of ground conditions is paramount in developing a project,” says Edmonds. “As we go for bigger and bigger structures we need to put the foundations deeper into the seabed and a better understanding and modeling of ground conditions can be useful in understanding how long it will take to build and how deep foundations need to be.”

Looking forward Edmonds is confident of the offshore wind sector’s long-term future. Whilst he admits that the sector did experience a hiatus after the Government changed the incentives mechanism from ROCs to the Contract for Difference he now feels the sector is comfortable with the new regime. From his own perspective he is anticipating handing over the reins of Gwynt y Môr to the operations team before moving on to fresh development projects.