A joint project of the utilities EWE, E.ON and Vattenfall

alpha ventus - the first German offshore wind farm

 alpha ventus was commissioned as the first German offshore wind farm in April 2010. The construction phase proper was a brief 12 months, a pioneering feat in a location with a water depth of about 30 metres and a distance from the coast of 60 kilometres.

Reflecting its role as offshore test site, alpha ventus operates two types of wind turbines with two different foundation designs. The rated output of the wind farm is 60 MW. Experience gained in construction and operation is an input into the further development and expansion of the German offshore wind power industry.

The alpha ventus offshore wind farm is a joint project of the utilities EWE, E.ON and Vattenfall. These three energy providers established the “Deutsche Offshore-Testfeld und Infrastructur GmbH & Co. KG” (DOTI) operator consortium specifically for this purpose in June 2006. The shares distribution is: EWE 47.5%; E.ON and Vattenfall each 26.25%. The total investment is Euro 250 million with the BMU (German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety) providing Euro 30 million of funds.

During the operating years from 2011 to 2014, alpha ventus achieved 16,582 full capacity hours and generated 994.9 gigawatt-hours (GWh) of electricity. The yield is therefore 248.73 GWh per year on average and exceeds the generation forecasts by around seven per cent. Statistically, the average yearly energy yield is sufficient to supply annually approximately 71,000 average (3,500 kWh) households in Germany.

If the power generated during the commissioning period is added to the four full operating years, alpha ventus has generated over 1.2 terawatt-hours of electricity since 2009.

Press Release, 21.02.2014

Energy yield 2014: Germany’s first offshore windfarm “alpha ventus” continues to operate according to plan after four years of operation

 During the operating years from 2011 to 2014, alpha ventus achieved 16,582 full capacity hours and generated 994.9 gigawatt-hours (GWh) of electricity.

The yield is therefore 248.73 GWh per year on average and exceeds the generation forecasts by around seven per cent.

In the 2014 operating year, the yield was slightly below average at 235.6 GWh of climate-friendly energy, but still exceeded the forecast by 1.5 per cent. This relatively slightly lower output is attributable to the replacement of some components during the course of the year. The months of January and December 2014 were particularly high yielding with over 30 GWh of generated electricity in each month.

If the power generated during the commissioning period is added to the four full operating years, alpha ventus has generated over 1.2 terawatt-hours of electricity since 2009.

Follow-up projects in Germany

With the inclusion of the first follow-up projects to alpha ventus, EWE, E.ON and Vattenfall are currently realising and operating offshore-windfarms with a total output of 744 megawatts in the German Bight.

EWE: The “Riffgat” offshore-windfarm in the vicinity of Borkum was completely erected by July 2013, and has been feeding environmentally-friendly power into the German grid since February 2014. The 30 wind turbines have a total generation capacity of 108 megawatts.

E.ON: The "Amrumbank West“ offshore-windfarm lies to the north of Helgoland in the German Bight, and will achieve a total output of 288 megawatts from its 80 wind turbines. The substation and the first 60 foundations were installed in 2014. Installation of the wind turbines follows in 2015.

Vattenfall: The “DanTysk” offshore-windfarm lying to the west of Sylt was completely installed in 2014 and is already delivering electricity. The 80 wind turbines with a total generation capacity of 288 megawatts have been successively commissioned since December 2014, and are all scheduled to be connected up to the grid by early 2015. Work on the “Sandbank” offshore-windfarm lying approx. 35 kilometres to the west begins in summer 2015: it will have 72 4-megawatt wind turbines and a total output capacity of 288 MW.

Press Release, 21.02.2014

First terawatt-hour offshore power

 alpha ventus surpassed in February the mark of one terawatt hour of generated power. Germany’s first offshore wind farm, with 12 wind turbines, has generated the equivalent of one billion kilowatt hours of climate-friendly power for the German transmission grid. This figure is equivalent to the annual consumption of 285,000 households. The operator consortium of EWE, E.ON and Vattenfall looks back over three positive years of regular operations.

alpha ventus has been feeding power into the grid since August 2009. Regular operations commenced in April 2010. During 2011-2013 alpha ventus achieved a total of 12,675 full load hours. The average yield of the offshore wind farm in 2011 through 2013 was 253.14 GWh per annum, exceeding the forecast yield by approximately 10 per cent. The capacity factor of the wind farm of 48.1 per cent during this period is an outstanding result by international standards.

The annual yield in 2013 amounted to 224.6 gigawatt hours, for the first time falling 3.3 per cent below the forecast average annual yield. The low winds in the four months of February, April, May and July 2013 and technical downtimes of individual wind turbines could not be compensated in the annual average by the particularly windy months of October and December.

“Offshore is not yet routine. The economic, safe and environment-friendly operation of an offshore wind farm in the North Sea continues to be our key goal. We are pleased that the results for 2013 are better overall than we had still been expecting in September. The two storms “Christian” and “Xaver” generated good yields during the last quarter,” said Wilfried Hube, CEO of wind farm operator DOTI. “The further expansion of offshore wind power requires the right political framework to be in place. The offshore target of 6.5 GW installed capacity by 2020 remains ambitious. The three follow-up projects to alpha ventus demonstrate that the energy utilities are doing their share.”

Follow-up projects in Germany

EWE: The Riffgat offshore wind farm near Borkum was completed in July 2013 and feeds climate-friendly power into the German grid since February 2014. 30 wind turbines have a total output of 108 megawatts.

E.ON: Offshore wind farm Amrumbank West is situated north of Heligoland in the German Bight and will comprise 80 wind turbines with a total output of 288 megawatts. Work on installing the turbine foundations commenced in January 2014.

Vattenfall: Located to the west of the island of Sylt, the DanTysk offshore wind farm will generate a total output of 288 megawatts climate-neutral power with 80 wind turbines. All foundations were put in place in 2013; the installation of the wind turbines is to start in spring 2014.

Press release, March 5th, 2012


alpha ventus 2011 Annual Review – Encouraging Offshore Power Yields

 The alpha ventus consortium DOTI, formed by the companies of EWE, E.ON and Vattenfall, can look back with satisfaction on a successful 2011: the twelve wind power turbines of Germany’s first offshore wind farm have fed over 267 gigawatt hours of electricity into the German power grid over the entire year. This puts the amount of power generated by alpha ventus at around 15 percent over the projected total for the year.

“These results exceed our expectations", says a pleased Dr. Claus Burkhardt of EWE in his capacity as DOTI Managing Director and General Project Manager. “The exceptionally high power yields achieved by alpha ventus in 2011 are due primarily to the nearly constant and excellent wind conditions at the wind farm together with a high turbine availability of up to 97 percent.” Burkhardt adds that the alpha ventus offshore test field proves that offshore wind farms can be economically and commercially viable in Germany in the long term despite challenging conditions, such as long distances from coastlines and great water depths. The German government is correct in making offshore wind power a key technology for accomplishing the transformation of the German energy system (“Energiewende”). However, Germany’s ambitious development goals of ten gigawatts of installed offshore wind capacity by 2020 can only be achieved by quickly eliminating obstacles that are currently impeding industry growth and development. A particularly large obstacle is the uncertain and slow grid connection for planned offshore wind farms in the German North Sea and Baltic Sea.

Rudolf Neuwirth, DOTI Managing Director for E.ON shares the same opinion: “Now that the federal government has created better conditions, and therefore better incentives for new investments in offshore wind farms by amending the Renewable Energies Act (EEG) in the past year, they must now find a solution for ensuring the grid connection for these farms. Otherwise, many projects may fail, putting the continued growth and development of the industry at risk. This is how alpha ventus clearly demonstrates how offshore wind is a reliable a source of energy with enormous potential.” Neuwirth emphasises that the entire industry is currently placing great hopes on the findings of the “Arbeitsgemeinschaft Beschleunigung” (working group on the acceleration of offshore grid access), in which representatives from the Federal Environment and Economic Ministries, offshore wind farm investors and grid operators are presently working together to find solutions to the urgent problem of grid connection.

Bent Johansen, DOTI Managing Director for Vattenfall is optimistic: “Through the successful and positive experience of the joint realisation of alpha ventus, each of our companies has made further investment decisions to construct additional commercial offshore wind farms in Germany  Preparations to construct these projects are at full speed and for some projects construction will start within the year. This is how our companies are demonstrating their willingness to invest heavily in the offshore wind sector in Germany. Offshore wind is an important power generation technology for the German transition towards achieving sustainable energy (“Energiewende”).

Press release, June 30th, 2011


alpha ventus achieves positive interim results – offshore power yield higher than expected

 Germany's first offshore wind farm alpha ventus is generating more power than expected.While the first half of 2011 was disappointing for onshore wind farms, the constant and strong winds on the open sea over the last nine months have produced more than 190 gigawatt hours of electricity. The alpha ventus consortium, consisting of the utilities EWE, E.ON and Vattenfall, reports that the wind yield was around 5% higher than had been expected for this period.

"The high power yield of alpha ventus shows that offshore wind is already one of the pillars of a safe and reliable power supply. Offshore and onshore wind power complement each other perfectly, and even balance each other out", says Dr. Claus Burkhardt of the utility company EWE in his capacity as DOTI executive and overall project director of alpha ventus. After the technical problems of the first operating phase had been solved successfully, the wind turbines have reached a high availability. The turbines were operational for nearly 98% of the entire period. Claus Burkhardt: "This speaks for the reliability of German engineering in the wind energy industry. It also shows that our operations and maintenance concepts are fully validated."

On the other hand, Burkhardt points out that an offshore wind farm in Germany requires a considerably higher wind yield compared to its onshore counterpart in order to compensate for the significantly higher investment and operational costs. "This is a result of the difficult overall parameters here in Germany as opposed to other European countries, such as the required long distances from the coast and the correspondingly large water depths. They require elaborate offshore engineering for the turbines and foundations, as well as a corresponding infrastructure, such as suitable construction ships." According to Burkhardt, these factors continue to have a negative effect on the economic feasibility of German offshore wind farms and discourage potential investments. Thus, the German offshore wind industry first needs sufficient financial assistance to establish this young industry sector in Germany.

DOTI executive Rudolf Neuwirth of E.ON also underscores the great challenges the German offshore industry has to face in order to meet the ambitious goals set for offshore wind energy by the German Federal Government: "The successful alpha ventus pioneer venture shows the potential of offshore wind energy, but also the financial risks of complex offshore construction. Right now, as part of the massive changes in energy policy, the creation of no less than an entirely new industry is underway in the German North and Baltic Seas. Despite the positive experience of alpha ventus, many steps must still be taken", says Neuwirth. Nevertheless, alpha ventus’ positive interim results show that the German Federal Government is on the right path in focusing on offshore wind energy as an important element in establishing a CO2-friendly energy supply for the future of Germany.

DOTI executive Bent Johansen of Vattenfall is pleased that the pioneer venture is bearing its first fruits: "alpha ventus’ positive performance confirms that we are on the right path in terms of our offshore commitments. Both the plants and their 'motor' – that is, the wind – have proven to be reliable. With alpha ventus, we are making an important contribution to the development of climate-friendly energy production. Furthermore, in the rough conditions of the North Sea we are gaining valuable technical experience for the ongoing development of the entire German offshore industry. With the follow-up offshore projects by our three utility companies in the German North and Baltic Seas, we will further widen our expertise.”

alpha ventus

alpha ventus is the first German offshore wind farm that was constructed on the high seas. The pilot project is located some 45 kilometres from the coast of Borkum and provides fundamental experience in the construction and operation of an offshore wind farm. Twelve 5- megawatt class wind power turbines are operating at the alpha ventus test field: six AREVA Wind M5000 turbines and six REpower 5M turbines, resting on two different foundations. Whereas the AREVA wind turbines stand on tripods, the REpower turbines are mounted on jacket foundations in a water depth of 30 metres.

Research and development results will be incorporated into the design, construction and operation of future offshore turbines. EWE, E.ON and Vattenfall established the "Deutsche Offshore-Testfeld und Infrastruktur GmbH & Co. KG” (DOTI) in order to realise the alpha ventus wind farm. Using the name "Borkum West", DOTI leased the licensing rights for the test field from the Stiftung der Deutschen Wirtschaft für die Nutzung und Erforschung der Windenergie auf See (Foundation of the German Industry for the Utilisation and Investigation of Wind Energy at Sea.

 Press Contact


Christian Bartsch
Tel: +49 (0) 441 . 4805 . 1811


 Five years of ecological research at alpha ventus – Challenges, results and perspectives

Berlin, October 2013

 Key data

• Number of units: 12
• Total capacity: 60 MW
• Energy yield in 2011: ca. 267 gigawatt/hours (= annual energy consumption of about 70,000 households)

Technical data AREVA Wind M5000
• Rotor diameter: 116 m
• Height of hub: 90 m
• Total height above seabed: 178 m
• Rated output: 5 MW
• Speed: 5.9 - 14.8 rpm
• Cut-in wind speed: 3.5 m/s (= force 3)
• Rated wind speed: 12.5 m/s (= force 6)
• Cut-out wind speed: 25 m/s (= force 10)
• Blade tip speed: 90 m/s (= 300 km/h)
• Weight of nacelle without rotor and hub: 200 t
• Weight of nacelle with rotor and hub: 309 t
• Weight of steel in tripod, tower, nacelle: 1,000 t
• Tripod: Weight of steel: 700 t; Height: 45 m; Piles: 35-45 m

Technical data REpower 5M / Senvion SE
• Rotor diameter: 126 m
• Height of hub: 92 m
• Total height above seabed: 185 m
• Rated output: 5 MW
• Speed: 6.9 - 12.1 rpm
• Cut-in wind speed: 3.5 m/s (= force 3)
• Rated wind speed: 13.0 m/s (= force 6)
• Cut-out wind speed: 30 m/s (= force 11)
• Weight of nacelle without rotor and hub: 290 t
• Weight of nacelle with rotor and hub: 410 t
• Jacket foundation: Weight of steel: 500 t; tower: 210 t;

Technical data transformer station
• 30 m: elevation of helipad
• 25 m: elevation of main deck with crane, substation control and protection (I&C) / switchgear plant / neutral earthing transformer, fire extinguishing system, MV and LV systems, emergency generating set, MVAr throttle / 110 kV GIS (gas-insulated switchgear) system (AREVA)
• 21 m: cable deck with workshop, equipment room, lounge, diesel tanks, emergency generating unit, cable bench and oil sump
• Cable deck and main deck: 110/30 kV transformator 75 MVA (AREVA)
• Jacket foundation: approx. 750 t
• Foundation piles: 35 m long, 2.7 m diameter, 100 t apiece
• Position: N 54°00', E 6°37.40'

 Brochure on research at alpha ventus