Harnessing the wind: Riffgat Wind Farm

Construction work on Riffgat Wind Farm remains on schedule.

Riffgat Wind Farm is a brand new €480 million wind farm project currently under construction in the German North Sea. The site is located 15 kilometres from the island of Borkum and 25 kilometres from the Dutch island of Schiermonnikoog.

Once work on the project is complete, Riffgat Wind Farm will comprise 30 turbines – with a total capacity of 108 MW – and a transformer substation which will transfer power to the German energy grid. The total area of the site, including a 500 meter wide security zone, measures 13.2 square kilometres.

Riffgat Wind Farm is being developed by leading energy, telecommunications and information technology provider EWE in collaboration with Enova Energy Systems. Once the site becomes fully operational RIFFGAT GmbH & Co. KG – a joint venture between EWE and Enova Energy Systems – will operate the wind farm.

Work began on the project in May 2012. Leading wind power facilities manufacturer Siemens is supplying 30 wind turbines for the project, which will be installed throughout 2012 and early 2013.

Each of the turbines on the project has a 3.6 megawatts (MW) capacity and will generate enough electricity to power approximately 120, 000 homes. With an installed offshore capacity of more than 1,000 MW, Siemens is the leading supplier of wind power facilities in offshore operations.

The turbine foundations on Riffgat Wind Farm will be attached to the seabed using 30 monopiles; with one monopile being used per turbine. The monopiles measure 70 meters in length, contain up to 800 tons of steel pipes and were driven 40 metres deep into the ground during installation.

International offshore installation and removal contractor Seaway Heavy Lifting Contracting Ltd (SHL) installed the foundations on the project, with the first monopile operation taking place in June 2012. To date Riffgat Wind Farm is the second wind turbine foundation contract undertaken by Seaway Heavy Lifting Contracting Ltd in 2012.

A 183-foot crane ship known as Oleg Strashnov was responsible for carrying out all of the monopile work on the site. The ship transported foundation piles from the Dutch port of Vlissingen to the construction site where they were installed in a water depth of between 18 to 23 metres. The installation of monopiles took two months and was completed in September 2012.

The monopiles have a tip diameter of either 5.7 meters or 6.5 meters (depending on the water depth) and now that each is in place they will be topped with transition pieces. The transition pieces measure 26 metres in height with a tip diameter of 5.6 meters and a weight of 207 metric tonnes.

G&G and Idesa fabricated the majority of foundations on the wind farm project, except one foundation which was fabricated by UK based company TAG.

Following the completion of the monopiles, work began on the installation of infield submarine power cables.

Worldwide cable industry expert Nexans is supplying and installing the infield cables as well as ancillary equipment on the project. The company is manufacturing the cables at its facility in Hannover, with approximately 24 km of 33 kV XLPE submarine infield cables being used on the site. Once installed, the cables will connect the wind turbines to the offshore transformer substation, which is also currently under construction.

To complete the project, nacelles and wind turbine rotors will be erected in spring 2013.

Riffgat Wind Farm is scheduled to begin generating environmentally friendly power to the German grid from summer 2013.

EWE 

Based in Oldenburg, EWE is a modern energy provider, currently serving more than a million electricity customers and 700,000 natural gas customers with reliable energy.

EWE offers a broad range of innovative energy services for use in the residential, industrial, public utilities and municipalities sectors. The company is also active in the gas storage business where it continues to build upon its already established position.

In addition to EWE’s involvement with Riffgat Wind Farm, the company was previously involved with Alpha Ventus, Germany’s first offshore wind farm.

Enova Group

Since 1996, the Enova Group has been involved with the development of a number of high-profile offshore wind energy projects across the North Sea.

From its base of operations in Bunderhee the Group’s team of experienced engineers have developed projects, taking concepts from the initial design stages through to planning and delivery. The company offers a turnkey delivery, alongside a technical and commercial management service which lasts the entire lifetime of the project.

Enova Group’s services include investments in windfarms, the optimisation of power consumption and the development, realisation and operational management of both onshore and offshore projects.

Fred Olsen Windcarrier AS

Since 2009, Fred Olsen Windcarrier AS, has built up its organisation, by specialising in the installation of offshore wind turbines and the implementation of crew transfer operations across the North Sea. The “Brave Tern” and her sister vessel “Bold Tern” will be the flagships in the Windcarrier fleet and, at the time of their launch, will be the largest self-propelled, custom built installation vessels in the world. The vessels are capable of carrying up to 8-9 Siemens 3.6MW turbines, up to 10 Vestas 3.0 MW turbines and are designed to operate in water depths of up to 45m. The 800 tonne GustoMSC type GLC-800-ED- crane has been designed around the rear portside leg to increase accessibility and full utilization of deck space.  The three Voith Schneider propulsion units coupled with the three bow mounted tunnel thrusters will ensure unparalleled manoeuvrability and positioning capabilities in high seas. Fred Olsen Windcarrier AS also provides crew transfer services via its five purpose-built vessels – a service soon set to expand with additional vessels.

On the Riffgat project, Fred Olsen Windcarrier AS is involved with the transportation and installation of 30 turbines across the site, which also includes the installation of all towers, nacelles and blades.

Fred Olsen Windcarrier AS Commercial Manager, Carl Erik Gurrik, said:

“The Riffgat project is very important to us. EWE is one of the largest German energy companies in the world and this project allows us to work closely with Siemens, a leading name in the wind farm sector.”

Carl Erik Gurrik added:

“The work that we are conducting on the site allows us to optimise and improve the installation phase by using high-quality, state-of-the-art vessels, with experienced crew members.

“Our vessels allow for a higher crane capacity, more deck space and more reliability and this will eventually result in energy companies delivering power to the grid quicker than before.”