Lead Session Chair:
Stephan Barth, Managing Director, ForWind - Center for Wind Energy Research, Germany
Marzena Dziedzcika (1) F P Charlie Whyte (1) Alan West (1) Geir Olafsson (1)
(1) W3G Marine Ltd, Aberdeen, United Kingdom
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Presenter's biographyBiographies are supplied directly by presenters at OFFSHORE 2015 and are published here unedited
Ms Dziedzicka has been working in the wind industry for the last three years. She studied mechanical engineering at Robert Gordon University, completing her master thesis on “Noise vs efficiency of a tidal turbine”. She is currently a project engineer at W3G Marine Ltd. Her work is focused on the underwater noise mitigation method during piling operations offshore.
Hydronas - the future of underwater noise mitigation
This paper presents the development by W3G Marine (W3GM) of a revolutionary underwater noise mitigation system (NMS), HydroNAS™.
Currently Offshore Wind (OW) turbines are installed onto a fixed substructure which connects to the seabed through either a jacket or monopile. Both require the use of an impact hammer to drive a pile into the seabed. This generates underwater noise, harmful to marine life. To screen the noise an NMS is deployed. Currently available NMS’s are either heavy, have a high cost and/ or require main vessel critical path time. HydroNAS is none of these.
During 2010, following demands from the OW industry for a safe, effective, versatile and low cost NMS, W3GM commenced an R&D programme to prove a new concept. First, W3GM identified and partnered with EATEC, a specialist acoustics and vibration engineering firm with a track record of innovation and problem solving. EATEC provided the acoustic ‘brain’ with W3GM developing complementary offshore deployment methodologies. The R&D programme has been supported financially by Scottish Enterprise and a UK Round 3 developer and technically by most other European OW developers and industry specialists, such as Dr Michael Bellmann (ITAP).
Main body of abstract
The HydroNAS™ concept is simple. It’s an unbroken column of air around the pile from the seabed to the surface. This creates water-air-water impedance mismatches which reduce underwater noise. Without the use of a fixed metal structure, which inherently contains many leak paths, creating an unbroken air column at depth was the challenge. This solution identified and patented by W3G Marine is to use a lightweight inflatable fabric which is restrained internally, such as drop stitch.
Upon the inflation of drop stitch, a fixed volume panel of air is created which maintains a specified geometry underwater avoiding ballooning which would otherwise occur. Cells are joined to form rings which are stacked such that the inflated structure is deployed around the pile to provide a barrier along the full water column. This modularity allows for the system to be configured to fit any water depth, pile diameter or indeed any type of pile.
W3GM also has patents covering the use of an indexing arm within a piling template. The guide slot is shrouded in HydroNAS™.
HydroNAS™ R&D programme:
• Proof of concept (2010)
Result – The concept works
• 10m water depth quayside trail of an un-optimised system (2013)
Result - 12db-14dB SEL at 750m
• Optimisation trial at National Physical Laboratory open water facility (2013).
Result – multiple barriers improve noise suppression.
• ISVR Consulting (Southampton University) performance prediction analysis (2014).
Result - >14dB SEL at 750m expected for offshore piling.
• Offshore trial (2015)
As a result of over four years of R&D investment, W3GM expects to prove HydroNAS™ offshore during 2015. The system provides developers and installation contractors with a safe, efficient and cost effective NMS alternative which can be tailored to suit exact project requirements. The use of HydroNAS™ can result in no lost main vessel time representing a further cost saving. In addition HydroNAS™ solves other challenges such as seabed bearing strength issues and can even be preinstalled onshore onto a monopile. HydroNAS™ solves all underwater noise challenges faced by the industry at a fraction of the current cost.
Along the R&D journey two main learning outcomes were evident; Patience and the need for alternative revenue streams to support an R&D programme. Taking a new product into an immature market was always going to be a challenge, financially and technically. However through determination and perseverance W3GM has delivered a game changing technology which will realise improvements in safety and significant cost savings coupled with no installation vessel downtime.