PUSHING THE BOUNDARIES OF OFFSHORE WIND POSSIBILITIES WITH THE NMS

Building the largest German offshore wind farm to date

The construction of Gode Wind was driven by Germany’s hugely ambitious green goals. The country wants to produce 18% of its energy from renewables and cut its greenhouse gas emissions by 40% by 2020.

Noise mitigation

There’s a growing awareness of the effects of the sounds generated by offshore activities on sea creatures. Many countries have developed legislation that stipulates the acceptable levels of noise emitted during these operations.

It was of vital importance that the Gode Wind project met the strict maximum sound level of 160dB SEL05 at 750m – as enforced by German regulations agency BHS – throughout the duration of the installations. This has challenged IQIP to provide its latest innovation in noise mitigation with the NMS-8000. Not only did IQIP supply the hardware, but they also offered complete support during the construction, with location specific piling advise.

NMS-8000

The NMS-8000 is based on a double-wall steel screen capable of resisting harsh offshore conditions such as current and wave impact. The main noise mitigation features are the air-filled annulus between the inner and outer screens and a multi-level and multi-size bubble injection system. The basic concept of the noise mitigation system is to create barriers between different media and materials.

Compared to its predecessors the NMS-8000 is capable of housing piles with a diameter up to 8.2 metres and is equipped with an optimised air annulus and bubble injection system. Together with new developed piling methods such as HiLo, Smart Pile Driving and Efficient Pile Driving, the NMS provides consistent noise mitigation.

For efficient, accurate and safe installation of the largest monopiles

Significant savings

The first 40 monopiles at Gode Wind have been successfully installed on schedule, mostly using the NMS-8000 in combination with a big bubble curtain. This recipe has proven itself to be successful in noise mitigation with levels of 153 to 155 dB SEL05 at 750 metres. Frequency specific the NMS provides reductions over 45 dB which might be of minor influence in the SEL05 but are of great importance for the Harbour Porpoises that inhabit the area.

Several monopiles have also been installed using the NMS-8000 without BBC with results below 160 dB. These consistent noise results mean that the NMS is capable of complying with the German noise rules without an additional mitigation system. For contractors in offshore wind, this results in significant financial savings.

“The rotation tool allows for a connection to the monopile heading within a timeframe of 30 seconds”

Technical Director

INSTALLATION TIME

The monopile installations for Gode Wind were completed within six months – a fast turnaround for such a project. This is actually the same timeframe as a similar project without noise-mitigation measures. That’s an important achievement – to eliminate any extra time needed for mitigation – because time is a major cost driver.

INTEGRATED EQUIPMENT

One of the key factors in reducing installation time is the integration of several important functions into the NMS-8000 that would otherwise require separate pieces of equipment. As the number of tools required for a project increases, so does the number of resources used. These might include deck space, operators, energy and, perhaps most importantly, costs.

The rotation tool allows for a connection to the monopile heading within a timeframe of 30 seconds. It also eliminates the need for a number of other separate tools, including rotational slings and winches. And as it reduces the amount of deck space required for operations, it enhances the safety of personnel by decreasing the risk of injuries.

The NMS also creates a sheltered space for the monopile during installation. This makes it possible to increase the operational window, because the monopile is protected from the elements by the system.

In addition, as the result of a reduced DAF (dynamic application factor), the crane can be used to its full capacity, because it too is less affected by dynamic conditions in the surrounding waters. In fact, the whole operation becomes less reliant on weather conditions, which further speeds up the process.

MULTIPLE FUNCTIONALITY

Other vital elements of the NMS-8000 include a diaphragm centraliser, which helps to adjust the inclination of the monopile while avoiding damage to the structure. Meanwhile, an optional set of hydraulic operated bottom rollers enables a swift and accurate installation of a monopile, but also provides crucial protection to avoid damage during retracking or recovery.

By combining this multiple functionality into the NMS-8000, the project benefits from a speedier and more accurate installation process. It also results in increased workability, less risk and reduced costs – and it ultimately improves the overall integrity of the monopile.

LARGEST MONOPILES

One crucial trend within the wind sector, and particularly offshore wind, is the larger capacity per wind turbine. In order to support these next-generation wind turbines, monopiles have increased substantially in size, up to a point where almost all installed monopiles are now Monopiles XL.

At Gode Wind these boundaries are stretched further than ever before. Located 45km from the mainland, Gode Wind – a Dong Energy project – will become Germany’s largest offshore wind farm. With a total capacity of 582MW when it becomes operational in 2016, it will be able to power 600,000 households.

The monopiles used to house the 6MW turbines have a diameter of 7.5m, with the largest measuring 67m in length and weighing well over 900t – the biggest and heaviest monopile to be installed in the German part of the North Sea to date.

THE CHALLENGE

Installing a total of 97 wind mills to generate 582 megawatts, enough green electricity to supply 600,000 German households.

NMS GUIDING TOOL

Allows the NMS to be adjusted to the correct inclination from the deck by a single operator.

DOING THE HEAVY WORK AT GODE WIND

  • Hydrohammer S-3000: Hydraulic piling hammer for driving steel piles among others
  • NMS-8000/36: Used to reduce noise during monopile installation and as a handling tool.
  • NMS Guiding Tool: Tool for the positioning and supporting of the NMS for the installation of monopiles.
  • 1,000t Pile Upending Tool: Tool for upending large piles with a diameter up to 6500mm and a capacity of 1000t.
  • 600t Transition Piece Lifting Tool: Hydraulically operated lifting tool used for transition pieces with a working load limit of 600t.
Curious? Please do not hesitate to contact us!