Harland and Wolff

Harland and Wolff Heavy Industries Ltd. in Belfast, a Fred. Olsen related company specialising in shipbuilding and offshore construction, recently completed a contract to build the world’s first commercial offshore suction Bucket Foundations. Three Bucket Foundations have left the Harland and Wolff fabrication yard in the past months on board the Fred. Olsen Windcarrier vessel Brave Tern.

Two of them are for met mast installations on Dogger Bank, the wind farm zone being developed by Forewind, and the third one, also for a met mast, on the Firth of Forth zone being jointly developed by SSE and Fluor.

Fred. Olsen United and related companies are presenting the Bucket Foundation as their preferred solution for offshore wind turbine foundations. The foundations are designed by Universal Foundation A/S at their design facility in Aalborg, Denmark, also a Fred. Olsen related company. Capable of being installed as foundations for current wind turbines, 6MW for example, the Bucket Foundations are also able to be scaled up for 10MW turbines in the future. Fred. Olsen United are currently busy with tenders to design, build, deliver and install Bucket Foundations on the next generation of wind farms, such as for the UK Round 3 licences.

Round 3 wind farms in UK waters have many areas where water depths reach 50m. This foundation is ideal for waters between 20m and 50m. There is no one set of dimensions to suit all conditions. The met mast foundations delivered recently have a 15m bucket diameter. For the larger and heavier wind turbines they do not envisage that the diameter will exceed 20m, a foot print of over 300m2 (larger than the area of a tennis court of 260m2.) The weight of the foundations already delivered is comparable to a conventional jacket foundation between 350 and 400 tonnes.

Quicker, cheaper and more environmentally friendly

The advantages of this type of foundation become apparent in both the short term and long term scales. Short term they are cheaper and easier to build than a traditional jacket structure.

With an installation process devoid of pile driving and the necessity for divers, and most importantly, multiple and expensive vessels, they are also cheaper, estimated to be as much as 20% less expensive, and easier to place on site. Just one WTIV such as the Brave Tern is all that is required to deliver and install the foundation, there is no need for a separate installation of a transition piece. The entire installation work can be carried out in one day. When the Bucket Foundation is placed on site, the installation is divided in two phases. In the first phase the foundation is driven into the soil by means of its own weight. The installation is continued in the second phase by applying assisted suction inside the bucket. By applying suction the effective stresses in the soil are significantly reduced and the Bucket Foundation is sucked downwards until the target depth is reached. If you have ever lost a rubber boot while walking through deep mud you will know exactly how powerful this suction can be. When the bucket is sufficiently embedded on location it is immediately ready for the turbine tower to be placed.

In the long term it has a low life-cycle cost and an easy removal operation is all that is needed when decommissioning the wind farm. By reversing the installation process it is possible to remove the Bucket Foundation in its entirety and it can then be recycled or reused, making it stand out as an eco-friendly alternative to many current solutions.

Production yard

However, Harland & Wolff is by no means a one product company. The yard has already adapted and used their facilities for other activities connected with the offshore wind industry. These have recently included the storage, assembly and offloading of components onto delivery jack-ups for Robin Rigg, assembly and erection of the transformer platform and jacket for BARD Offshore 1, and logistic and assembly activities for the Ormonde offshore wind farm. The company also jointly designed, engineered and fabricated the 2 offshore substations for Gwynt y Mor with Siemens. With an investment over £1M on new automatic cutting and welding machinery in their yard, Harland and Wolff are continually improving the facilities to enable a dedicated production facility. There is currently 30,000m2 of covered manufacturing halls and 300,000m2 of hard standing area. These facilities give them the ability to store the completed foundations on land with easy loading on to vessels to take them to the wind farm site.

The yard also boasts the largest dry dock in Europe at 556m x 93m. This dock is covered by the trade mark of the Belfast skyline, the twin 840t gantry cranes, appropriately named Samson and Goliath. As a fabrication facility Harland and Wolff are able to manufacture and deliver a full range of offshore wind farm structures including monopiles, gravity bases, jackets and floating foundations. Just before we went to press, as if to prove our point that Harland & Wolff is by no means a one product company, they announced the signing of 2 contracts, one with E.ON for the design and fabrication of the substation jacket for E.ON’s 219MW Humber Gateway wind farm, and one with Glosten Associates for the construction of an offshore wind floating platform system demonstrator.

Dick Hill