Reducing the environmental impact of offshore piling activities
Offshore wind turbines have grown significantly in size in recent years, and as a result can generate more renewable energy to meet climate change targets. However, the ever-increasing size and weight of the new generation of wind turbines – and greater water depths – have implications for their installation, particularly regarding the impact of noise from piling activities on marine life.
This is an important consideration for developers. They must comply with international noise mitigation legislation to gain approval for, and continue working on, their offshore wind farm projects. The most stringent legislation is currently in Germany, and applicable to Arcadis Ost, a 257 MW offshore wind project located in the Baltic Sea.
“The noise threshold in German regulations is set at 160 dB Sound, Equivalant Level at a distance of 750m the pile to comply with this, additional noise mitigation is required,” e Offshore Wind Project Specialist at IQIP. “Arcadis Ost is one of the first projects to install ten-metre diameter monopiles – 28 in total – This meant that they were looking for a new method to reduce noise.”
Listening to the market
IQIP is supporting the contractor, DEME, and project developer, Parkwind NV, with an innovative piling method known as Pulse. “The new DP3 offshore installation vessel, ORION, will lift the monopiles and our IQIP’s equipment will be there to drive them down to final penetration,. “Although it’s still under development and this is its first commercial use, IQIP is confident that Pulse will make a significant contribution to staying within the noise limits.”
Pulse is a modular add-on to the standard IQIP Hydrohammer. The unit is positioned between the pile driving hammer and sleeve, and dampens the impact and noise with two steel plungers. The volume in between the plungers can be filled with water, which extends the impact of each blow of the Hydrohammer, resulting in reduced noise levels.
“The main advantage of Pulse is that it uses an adaptable volume of water as a cushion between two pistons, which helps to deliver a softer blow with a longer duration to the pile,”
“This causes less vibrations in the water and soil.”
In addition, the use of water eliminates the risk of wear or breakdown associated with other cushion materials. It is also highly flexible as the settings can be adjusted depending on the penetration required in addition, if something is not going according to plan, the customer can drain the water and go back to using a standard hammer.
Using Pulse will enable customers to complete installation more quickly due to the efficiency of penetration per blow. Results indicate efficiency improvements of 10%. It also contributes to reduced installation fatigue, which will give developers and monopile designers more opportunities to optimise structure designs and meet the need to lower the levelised cost of energy.
“It could accommodate TP-less monopiles, for example, and in the future even lead to the design of lighter monopiles, reducing the amount of steel required.”