NOISE REDUCTION
QUIET PLEASE
Construction of offshore wind turbine foundations is mostly done via pile driving using hydraulic hammers. These hammers typically consist of a steel ram weighing around 150-200 tonnes which impacts onto the pile top to drive it down. Big efforts must be made in order to reduce the underwater noise.
FEATURE SPONSOR
Underwater noise is a big issue when installing offshore windfarms – so what if we could reduce the noise at source?
That’s exactly what Netherlands-based Fistuca are doing with their ground-breaking BLUE Piling technology and Lloyd’s Register’s noise experts are helping to take it from a prototype to a commercial reality.
Image courtesy of Fistuca
NEW CONCEPT
Fistuca looked into a new concept for impact driving of monopoles – BLUE Piling. After a testing phase (in which four prototypes were tested over four years) the company, led by Jasper Winkes and with support from Huisman Equipment and the Dutch Government, started work on a fully developed model which, when completed, will be the largest hammer in the world, the BLUE 25M.
Unlike conventional hydraulic hammers, Fistuca’s BLUE Hammer uses the acceleration of a water column by combustion of a gas mixture to drive the pile into the ground. A combustion cycle pushes the water column in the air after which it falls back on the pile, delivering a second blow.
Essentially, the BLUE Hammer replaces the steel ram with a big volume of sea water – in turn replacing the loud ‘metal- on-metal’ impact to the comparatively more silent impact of ‘water-on-metal’. The physics of shallow water acoustics cause reduced noise propagation at these frequencies. This gives the BLUE Hammer a natural low-noise advantage.
TESTING THE ASSUMPTIONS To progress the technology towards mainstream development, Fistuca needed to test and validate the assumptions. Fistuca asked Lloyd’s Register’s Engineering Dynamics team (based in Copenhagen) to help with this. The team therefore looked at scaled input test data and performed numerical simulations of the expected underwater noise from the prototype device during operation.
According to the simulations, this has the potential to produce far less noise than the ordinary, hydraulic hammers. Whether that full potential is exploited is yet to be demonstrated in a full-scale trial at sea of the BLUE Hammer.
Lloyd’s Register
36
www.windenergynetwork.co.uk
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