Last summer, Heerema Marine Contractors completed the installation of its first wind turbine generator (WTG) monopile foundation project at EnBW’s He Dreiht offshore wind farm. In a new project film, the team involved explains all about the installation with tight timelines and the noise mitigation measures that were taken.
He Dreiht is currently Germany’s largest offshore wind farm. On 6 August, as Heerema‘s semi-submersible crane vessel (SSCV) Thialf had installed all 64 windturbine generator (WTG) monopile foundations. Each monopile measures approximately 70 metres in length and weighs 1350 tonnes, and each transition piece is 32 metres long and weighs 670 tonnes.
In the project film below, which was published on Heerema’s Linkedin page this week, the Heerema team consisting of project manager for He Dreiht Erik Bögels, noise engineer and marine biologist Annabel Smith-Moorhouse, underwater noise engineer Govert Jan Glasbergen, operational manager Thialf Wesley Vollebregt, and senior specialist engineer Jetro Dam, discuss the challenges of the project, the tight deadlines and the noise mitigation measures in detail.
Efficient installation cycles and reducing noise
The installation was finished well within the agreed timeframe, with all activities, including full grouting, completed within 24 hours per foundation location. These efficient installation cycles were made possible by the efficient operation of Thialf’s dual cranes, the significant noise reduction achieved using the innovative Template-Noise Mitigation System 10000 (T-NMS-10000), and the feeder barge concept, which ensured a continuous supply of monopiles and transition pieces to the vessel.
The T-NMS-10000 was constructed at Heerema Marine Contractors and developed in close cooperation with IQIP. It is the largest noise mitigation system in the world. It measures 50 metres high, has a template base of 45 metres wide, a total weight of little under 2500 tonnes, and is capable of handling monopiles with a diameter up to 10.0 metres.
In addition, the system offers 15 dB driving noise reduction, levelling up to 3 degrees bottom slope and has capabilities to be used in up to 42 metres in water depth, making it is an essential tool for future installations of offshore wind.
Also read: Heerema’s Thialf wraps up He Dreiht monopile foundations
Double-wall steel screen
The NMS-T-10000 is derived from its successful NMS–8000 and NMS–8800 predecessors, which are recognised as the best-in-class underwater noise mitigation technology. The basic concept of IQIP’s noise mitigation systems is to create barriers between different media and materials.
The NMS-T-10000 is, simply put, a double-wall steel screen featuring an air-filled annulus between the inner and outer screens and a multi-level and multi-size bubble injection system. This efficient solution mitigates up to 98-100 per cent of the waterborne noise.
Also read: Heerema installs top section of new Noise Mitigation System
He Dreiht
When completed, the He Dreiht wind farm is expected to have a capacity of over 960 MW, providing renewable energy for approximately 1.1 million households. This project not only supports Germany’s energy transition, but also contributes to the European Union’s broader goals of increasing renewable energy capacity and reducing dependence on fossil fuels.
Picture by Heerema Marine Contractors.
