An article from the Trianel GmbH press office
Successful noise protection at the Trianel wind farm in Borkum
Aachen / Hamburg / Essen. The Trianel wind farm in Borkum, 60 kilometers off the East Frisian coast, is still on schedule and budget despite the difficult weather conditions in November and December last year. Five months after construction began, the Jack-Up-Barge Goliath has now rammed 26 of the 40 foundation structures into the seabed. For the first time in Germany, underwater noise protection was successfully used. The so-called “large bubble veil” is intended to protect the North Sea’s strictly protected harbor porpoises from hearing damage.
During a joint press conference in Essen, Trianel and the German Nature Conservation Union (NABU) presented the interim results of the accompanying research on noise protection today, February 9, 2012.
“The energy turnaround entails serious interventions in nature. NABU needs to reduce the impact on threatened and legally protected species to a minimum. That is only possible in a controversial, but also constructive, dialogue with investors, ”says NABU expert Elmar Große Ruse, describing the basic position of the German nature conservation organization with the largest number of members.
Trianel discussed the issue of protecting harbor porpoises in the North Sea even before construction began. The interim results on noise protection, according to Große Ruse, are auspicious: “It is not a matter of course that energy providers take the lead in environmental protection, here the municipal utilities involved in the Trianel wind farm in Borkum have acted in an exemplary manner for the industry.”
The managing director of Trianel Windpark Borkum, Klaus Horstick, explains: “The offshore permits stipulate compliance with a noise protection guide value of 160 decibels dB at a distance of 750m from the sound source. The explosiveness of this value lies in the fact that there is currently no technology on the market that ensures the value. With the large bubble curtain, our partners and we seem to have found a way to comply with noise protection. ”
According to current information, 50,000 porpoises live in the German North Sea: biologists estimate the population at 50-100 individuals on the 56 square kilometer area of the Trianel wind farm in Borkum. Every single animal is strictly protected, so the requirement is clear to NABU. Elmar Große Ruse: “As long as a more gentle method for founding wind turbines at sea has not yet been established, technical noise protection such as the large bubble curtain must be standard from now on.”
Trianel Windpark Borkum Trianel Borkum West II is the largest wind project in the German North Sea and the first purely municipal offshore wind park in Europe that is fully project-financed. The decision to build the Trianel wind farm Borkum West II was made in December 2010. Trianel GmbH, 33 municipal utilities and regional suppliers from Germany, Austria, the Netherlands, and Switzerland plus Trianel are involved in the wind farm. The wind farm is being built 45 km north of the coast of Borkum in a water depth of around 30 meters. In the first construction phase, forty turbines with an output of five megawatts each have been erected since September 2011. The wind farm is scheduled to go online at the turn of 2012/13. The construction costs for phase 1 are around 800 million euros.
The Big Bubble Curtain
The large bubble curtain is a noise reduction technology developed by Hydrotechnik Lübeck, which is being used for the first time in large-scale series use on the high seas at the Trianel wind farm Borkum. In a joint research project, Trianel, Hydrotechnik Lübeck, the Institute for Technical and Applied Physics Oldenburg (ITAP), and BioConsult SH are investigating the bubble’s effectiveness curtain with the support of the Federal Ministry for the Environment.
The technology is very simple. A perforated hose is laid around the entire construction site within a radius of 80-100 meters. It is filled with compressed air so that a curtain of bubbles, the so-called bubble curtain, rises from the sea bed to the surface. The nozzle hose has a length of around 500 meters and a total weight of 5 tons.
The sound is generated by the ramming impacts that occur when the offshore wind farm’s pile foundations are being driven into the seabed. The piles at the Trianel wind farm in Borkum, around 30 meters long, are driven into the sea bed with more than 1,000 rams. The bubble veil is an obstacle for the sound waves, which reduces the sound level to 10 percent of the original strength and protects the hearing of sea acids. Porpoises navigate the water with clicks and with their ears.