November 3, 2015
During the building of offshore wind turbines a lot of noise is produced under water, which is harmful for submarine life. To protect sea mammals a bubble curtain is placed around the site. The oil-free air needed for this curtain is supplied by Atlas Copco Rental . Recently 13 oil-free air compressors were used during an offshore wind construction project in the North Sea.
The building of these wind turbines requires a firm and stable foundation, as the offshore turbines are exposed to extreme weather conditions such as heavy wind and strong current. For the foundation of one wind turbine, three to four piles must be driven into the seabed. Each pile weighs 250 to 420 tons and has a length of 86 meters, of which 35 to 40 meters are hammered into the ground. During hammering the underwater noise level is more than 160dB(A) with a speed of up to 1500 m/s.
These sound levels are five times higher than in open air, and can harm and even kill sea life. Even small increases of the underwater sound level can disorient dolphins and whales, which communicate through ultrasound, making them drift away from the waters where they find their food and feed their young. To reduce the underwater noise levels, a so called “bubble curtain” is placed at the bottom of the sea, around the construction site. This bubble curtain can reduce the noise levels by more than 90%, thus protecting submarine life.
The air to produce the bubbles is supplied by 100% oil-free compressors of Atlas Copco Rental. Before installation of the hammer, a perforated hose is placed around each pile on the seabed. This hose is connected to an Atlas Copco oil-free air compressor. When the compressor starts up, small air bubbles are released from the perforated hose, creating a bubble curtain from the seabed to the surface.
100% oil-free air produces high-quality bubbles and guarantees no oil pollution of the sea water. In total, 10 to 16 mobile oil-free air compressors of the type PTS 1600 are installed on a platform ship. They are offshore certified and placed in a 20 feet offshore frame, in accordance with the DNV 2.7-1 directions, making sure the compressors can be moved safely also offshore. Recently we supplied 13 oil-free units to a project in the North Sea, where they provide air for the bubble curtain around the platform ship.
Written by Ellen Jansegers