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DONG Energy, which has erected half of the world’s major offshore wind farms, is currently building Denmark’s large- scale offshore wind farm, which includes an area of 88km² between Grenaa and the island of Anholt. The Anholt windfarm will become Denmark’s largest offshore wind farm with anoverall capacity of 400MW and will cover 4% of Denmark’s total power consumption.
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VIBRODRIVING TECHNOLOGY, A PILING SOLUTION THAT RESPECTS MARINE LIFE
The Anholt wind farm foundations required the driving of very large and heavy monopiles, which havebeen mainly driven into the sea bed with powerful hydraulic hammers using impact driving technology.Impact pile driving produces the highest under water noise level, as impulsive acoustic energy is createdupon impact. Strong sound waves travel then under water for several kilometers, putting in danger themarine life. As an alternative solution to reduce the noise emissions under water, Dong Energy decided to use in part of this jobsite PTC Vibrodriver’s technology (Vibratory pile driving), which produces lownoise emissions throughout the entire driving time.
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| Trio 3x200HD PTC Vibrodriving |
DENMARK’S LARGE SCALE OFFSHORE WIND FARM
Dong Energy is currently building the ANHOLT offshore wind farm, which includes an area of 88km² between Grenaa and the island of Anholt. It will become Denmark’s largest offshore wind farm, with anoverall capacity of 400MW and that will cover 4% of Denmark’s total power consumption. The Anholt wind farm foundations required the driving of very large and heavy monopiles, which havebeen mainly driven into the sea bed with powerful hydraulic hammers using impact driving technology.Impact pile driving produces the highest under water noise level, as impulsive acoustic energy is createdupon impact. Strong sound waves travel then under water for several kilometers, putting in danger themarine life. As an alternative solution to reduce the noise emissions under water, Dong Energy decided to use in part of this jobsite PTC Vibrodriver’s technology (Vibratory pile driving), which produces lownoise emissions throughout the entire driving time.
PTC SOLUTION: A TRIO OF 200HD VIBRODRIVERS
The foundations job required the driving of 275 t monopiles of conical shape with a bottom diameterexceeding 5 m. The complexity of this job with harsh offshore weather conditions and heavy piles,required a customised PTC solution: a Trio of 2OOHD Vibrodrivers perfectly synchronized to getan eccentric moment of 600 m.kg. These Vibrodrivers were powered by 3 PTC power packs 1200C model, supplying a total power of 2418 kW.
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| Trio 3x200HD PTC Vibrodriving |
FIRST PHASE: ONSHORE TEST, SYNCHRONISATION IS THE KEY
The synchronisation of the 3 Vibrodrivers as well as the 3 power packs was acomplex task, which resulted in a patented synchronization technology.In order to adjust the synchronisation of the PTC equipment before taken it to the barge, the jobsite begun with a onshore test. In this inital phase takenplace in the Aalborg harbour, the Trio of PTC 200HD drove into the ground ashorter test pile, which was then extracted with the same equipment. PTC’s technological approach was confrmed and the equipment was then taken to the barge. The next phase of the project was offshore in the waters of Kattegat between the North and the Balticseas, and just a few kilometers away from the Anholt island. The PTC pile driving equipment wasinstalled in the SVANEN barge owned by the company Ballast-Nedam and the driving of the 275 t pilesstarted as soon as the weather conditions were favourable. The piles were driven to the stipulateddepth in less than 30 min in a soil consisting of dense sand and compact silty sand. PTC Vibrodrivers proved a signifcantenvironmental advantage, as they drive thepile respecting the most recent germanregulations in noise emissions under water. (The regulation stipulates a maximum of 160dB at 750 m distance ). Dong Energy performed several sound measurements and washighly satisfed with PTC Vibrodriver’s lownoise emissions.In addition of an excellent driving speed of the pile, PTC Vibrodrivers confrmed othersignifcant advantages for offshore wind farm foundations:
• Pile extraction technology for precise pile positioning.
• An easier and safer pile handling• Underwater pile driving (up to 100m depth)
its a great.
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