Offshore wind farms: Wind energy in the middle of the sea

Offshore wind farms

Wind energy in the middle of the sea

EnBW is today already one of the leading developers and operators of offshore wind farms. In the Baltic Sea, we placed the first commercial wind farm in Germany EnBW Baltic 1 into operation in 2011. This was followed by Baltic 2 with its significantly greater dimensions. We are now moving our attention to the North Sea where we have started construction of two neighbouring wind farms at the same time: Hohe See and Albatros. We also have the approval to construct another wind farm called He Dreiht.

Hohe See and Albatros

EnBW has started the construction of both wind farms in the North Sea at the same time. They will supply electricity for an aggregate of around 710,000 households from 2019.

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Baltic 1

Our EnBW Baltic 1 wind farm is the first commercial offshore wind farm in Germany and has been in operation since April 2011.

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Baltic 2

EnBW Baltic 2 was connected to the grid in September 2015. 80 wind turbines produce up to 1.2 billion kilowatt hours of electricity annually.

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Wind power plants on the high seas

In the Baltic Sea, our two offshore wind farms Baltic 1 and Baltic 2 reliably generate electricity that can supply an aggregate of almost 400,000 households. We are gaining experience and also increasing the size and output through every new offshore wind farm – thanks also to the advances made in offshore technology. Our North Sea projects Hohe See, He Dreiht and Albatros will be constructed in close proximity to one another. Together they will form a 1,500 megawatt piece of the Energiewende.

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EnBW Baltic 1: How a wind farm is constructed on the high seas

Preparation: A traffic management ship arrives at the construction site and monitors the traffic at sea. The construction office is procured and the employees gradually commence their work.

Groundbreaking ceremony: official start of construction at sea. The components for the turbines that were manufactured on land are now successively installed at the offshore construction site.

Foundations: The special ship Sea Worker brings the foundations consisting of monopiles and transition pieces to the construction site.

Special ship: The Sea Worker anchors the monopiles, steel foundations around 37 m long, into the seabed using a powerful pile driver.

Colossus: Transition pieces are used to connect the foundations and the wind power plants together.

Transfer: The floating crane Matador (middle) transfers the 430 t monopile for the substation to the installation ship Sea Worker (right).

Precision work: The floating crane has delivered the 900 t substation to the construction site and will place it onto the transition piece in the evening.

Basis: The yellow crowhorn serves as the supporting surface for the substation and is fitted to the transition piece at the construction site.

Cable: Divers guide the sea cable upwards from the seabed through the transition piece. The cable will later be connected to the wind power plant.

Tower construction: The tower for the first wind power plant rises up piece by piece.

Raising the star-shaped rotor: The special crane has mounted the rotor with its 45m long rotor blades to the nacelle.

Precision landing: The first star-shaped rotor has been raised and the first wind power plant is installed.

For now the first turbine stands alone on the high seas...

...but the remaining 20 turbines will also soon be installed – EnBW Baltic 1 has been generating enough electricity for an aggregate of 50.000 households since 2010.

Powerful Teams

Wind, weather and waves are the greatest challenges facing offshore wind farms and are what govern the construction work and operation of the turbines. An international team of specialists for planning at the Hamburg office and a competent service team at the Barhöft service station provide vast expertise for the expansion of wind energy.

Engineers, economists, geologists and logistical experts from around the world are involved in the planning work.

On course for the future

Offshore office in Hamburg: Around 100 employees are involved in planning the EnBW wind farms. This is where expert reports are produced, authorities are consulted and decisions are made. Manufacturers and service providers must be commissioned, transport and delivery chains planned and all processes that make up the highly complex erection work must be coordinated – while possible delays also need to be compensated for.

The wind farm is monitored around the clock by the Barhöft service station.

The station that never sleeps

The service station in Barhöft: It is from here that the wind farm installed at sea is controlled and all the service tasks are coordinated – round the clock, seven days a week. Data about the weather and sea conditions indispensable to the operation of a wind farm are delivered continuously through measurements taken at sea. The offshore turbines switch themselves on from wind force 3 and automatically switch themselves off again in storms from wind force 10.

Safety for people and machinery

Everything comes together in Barhöft: This is where the EnBW Baltic 1 and EnBW Baltic 2 wind farms are monitored around the clock and the service tasks are coordinated.

Offshore, we need to plan far ahead. We work under extreme conditions: wind and weather, the motion of the sea and ice dictate our work schedule. Our team needs to work very well together because we cannot simply get into a boat and sail out there.

Torsten Richter, responsable SAV Barhöft

The safety measures on the high seas are particularly strict. Before employees are permitted to work at the wind farm, they must complete safety training lasting several days.

Anne Fischer, chef de projet partiel Sécurité au travail

We are venturing into unknown territory. That means it is possible to shape a lot of things yourself as an employee. Therefore, I am certain that I have one of the hundred most interesting jobs in the world.

Sven Kastrau, manager projet Électrotechnique

Wind power today and tomorrow

Our EnBW Baltic 1 wind farm is the first commercial offshore wind farm in Germany and has been in operation since April 2011. It is located 16 km north of the Darß/Zingst peninsula. The 21 wind power plants at EnBW Baltic 1 have a total output of 48.3 MW. They can thus cover the aggregate annual electricity requirements of around 50,000 households, preventing 167,000 t of harmful CO2 being released into the environment.

Our EnBW Baltic 2 wind farm surpasses EnBW Baltic 1 in all its dimensions. The construction of the second offshore project began at the end of 2011. It was officially placed into operation in 2015. The wind farm is located approximately 32 km north of the island of Rügen in the Western Baltic Sea on an area of around 27 square kilometres. EnBW Baltic 2 comprises 80 wind power plants each with a capacity of 3.6 MW and a total capacity of 288 MW. The offshore wind farm generates 1,200 GWh of electricity per year for around 340,000 households.

Following on from the Baltic Sea, EnBW will now take on the North Sea. In cooperation with its Canadian co-investor Enbridge Inc., EnBW will construct this offshore wind farm with a capacity of 497 megawatts around 90 kilometres north of Borkum and 100 kilometres north-west of Helgoland. 71 turbines will be installed on an area covering 42 square kilometres and generate around two billion kilowatt hours of electricity per year. After the wind farm has been commissioned – anticipated in 2019 – it will be able to supply around 560,000 households and save around 1.5 million tonnes of CO₂.

On course for the future with offshore wind power. EnBW aims to move further out to sea with the offshore wind farms planned in the North Sea – Albatros and He Dreiht. The demands relating to the scope, size and environmental conditions increase with every project. That means that the tasks involved are best tackled with years of experience, commitment and an international team of offshore experts – which is what happens at EnBW.

EnBW Baltic 1 wind farm

EnBW Baltic 2 wind farm

Hohe See wind farm

On course for the future

You ask – we answer

Can the wind turbines be seen from the coast?

EnBW Baltic 2 is located so far out at sea at around 32 kilometres from land that the wind power plants cannot be seen from the coast. The wind turbines at EnBW Baltic 1 that is located 16 km away can only be perceived as match-stick sized silhouettes from the coast. The curvature of the earth covers part of the around 115 m high turbines and a special paint coating prevents them from glistening in the sunlight.

What impact do the wind farms have on the environment?

Studies have demonstrated that mammals such as the harbour porpoise, sea lions and seals return to the areas taken up by the wind farm after a while. Numerous species of fish are also protected from the nets of deep-sea fishing vessels between the wind power plants. In addition, numerous species settle on the scour protection – a layer of stones deposited to protect the foundations from being washed away – like on an artificial reef. Migrating birds also display the behaviour that has been observed on land and mostly avoid flying through the area.

Do offshore wind farms have an impact on sea and air traffic?

Every offshore wind farm is marked in multiple locations by buoys, lighting and warning signs so that the area is visible for miles around. For this purpose, EnBW creates a so-called identification and lighting plan for every offshore wind farm in advance that is inspected by the responsible authorities. In general, the wind farms are erected sufficiently far away from very busy shipping routes. At a distance of 24 km, EnBW Baltic 1 lies far away from the Kadet Trench, which runs between the Fischland-Darß-Zingst peninsula in Germany and the island of Falster in Denmark.

What is the wind speed at which the wind power plants start to rotate?

A wind power plant starts up automatically from approximately 3 - 5 m/s (wind force 3). It achieves its maximum capacity of 2.3 MW (nominal output) from a wind speed of approximately 13 - 14 m/s (wind force 6). The output is then held at a constant level by adjusting the rotor blades (pitch system). In the partial-load range, the rotor speed and the pitch angle of the rotor blades is continuously adjusted in order to achieve a maximum level of aerodynamic efficiency. At wind speeds greater than 25 m/s (from wind force 10), the wind power plant is automatically switched off by adjusting the rotor blades. If the wind speed falls below the restart value, the safety system is automatically reset. The rotor blades are set to their operating position and the turbine is restarted.