Performance review of first full- scale AdBm system An alternative noise mitigation system in the face of increasingly challenging underwater noise legislation
Presentation structure Contents • Introduction to offshore wind • Environmental concerns • Environmental legislation • The necessity for mitigation • Introduction of Underwater Noise Abatement System project • AdBm system • Test set up • Results • Discussion 2
Introduction to offshore wind General Trends and Characteristics • EU target 20% renewable energy production by 2020 • EU target 32% renewable energy production by 2030 • Global push towards alternative energy such as offshore wind • Increase in total generated MW as well as generated MW per turbine • Increasing monopile diameters • Increasing driving forces to reach target penetration depth 3
Foundation securing techniques Pile driving overview Piling options • Vibratory piling • Impact piling • Alternative piling methods All with pros and cons Future non piling alternatives such as suction buckets or floating foundations Most common method: impact piling 4
Environmental concerns Underwater sound mechanisms Marine fauna makes use of auditory mechanisms for navigation and foraging Amplitude of piling noise can directly impact mammals in the area Piling without noise mitigation increases the range at which potential mammal impact can occur 5
Environmental legislation • Varies strongly dependent on governmental philosophy (i.e. impact on individual, exclusion zone of impact) • No ‘one size fits all’ mitigation Country Indicator Limit Additional Measures Comments Germany SEL 05 (5% 160 dB re 1 μPa 2 s at Maximum piling time of 3 hours; Acoustic exceedance level) 750 m Deterrent Device (ADD) L p,pk 190 dB re 1 μPa at 750 m Netherlands SEL 1 (maximum 159–172 dB 1 re 1 Acoustic Deterrent Device (ADD) Sound limits are driven by μPa 2 s at 750 m sound exposure level season as well as total number of a single strike in the of monopiles installed and can entire piling vary per the wind farm site. sequence) Belgium L p,pk 185 dB re 1 μPa at Acoustic Deterrent Device (ADD) 750 m United Kingdom Soft start of piling, Acoustic Deterrent Device (ADD); Marine Mammal Observers (MMO) Denmark SEL cum 190 dB re 1 μPa 2 s at Acoustic Deterrent Device (ADD) Cumulatively unweighted sound > 1300 m limit modelled over an increasing distance starting at 1300 m United States - Varies by project Must comply with Marine Mammal Usually marine mammal Protection Act, Endangered Species observers are used, and often Act, and other possible federal, state and some noise limits set at a local legislation particular distance are in place 6
Environmental legislation Legislation and challenges • Increasing number of countries enforcing underwater noise limits • Increasing challenges to meet new and existing underwater noise limits for several reasons: • Increasing monopile diameters • Increasing driving forces required to reach desired penetration depth • Lack of accurate applied knowledge regarding core drivers of underwater noise (other than monopile diameter and driving force) such as bathymetric impacts, soil type and layer thickness impacts 7
The necessity for mitigation Possible noise mitigation strategy • Acoustic deterrent devices to deter mammals (e.g. FaunaGuard, pingers, seal scarers) • Reduction at source (e.g. lowering driving force, reducer units) • Near to pile system (e.g. AdBm, HSD, IHC NMS others) • Far from pile systems (e.g. Single or Double Big Bubble Curtains) 8
Introduction to UNAS project Underwater Noise Abatement System partnership UNAS Program; Dutch Government RVO program dedicated to test promising AdBm system at full-scale within a field setting. Van Oord • Dredging • Offshore Oil and Gas • Offshore Wind AdBm Technologies • Creator of novel noise mitigation system (NMS) TNO Netherlands Organisation for Applied Scientific Research • Front runner in applied science research • Experts in the field of underwater sound 9
AdBm system Core specifications • Helmholtz resonators, tuned to 100 Hz • Resonators moulded in slats • Open system, resonator panels lowered in a Venetian blind formation around monopile foundation • Passive system, no continuous power supply necessary 10
Test set up Scenario configuration Tests executed according to ‘direct’ test methodology Endeavour for scientifically sound comparison. Executed on 5 piles • First 3 piles at 1.0m vertical slat space • Last 2 piles at 0.67m vertical slat space 8m of consistent soil properties Constant driving energy and pile diameter Four scenarios: • Scenario 1 – Benchmark test: no noise mitigation • Scenario 2 – AbBm: AbBm only • Scenario 3 – AbBm & BBC: Both AbBm & BBC system active • Scenario 4 – BBC system active 12
Test set up Measurement set up • Measured according to DIN SPEC 456532017-04 standard • Four cardinal directions at 750 and 1500m • Each measurement location features two hydrophones: • one hydrophone 2–3 m above the seabed • one hydrophone at 10 m above the seabed 13
Results Broadband analysis Test phase Test Slat Effective Effective Scenario spacing noise noise • Reduction of 5 dB SEL and 6 dB Lpeak with the reduction of reduction of original 1.0m slat spacing the SEL [dB] the L p,pk [dB] • Reduction of 11 dB SEL and 12 dB Lpeak with the 1 AdBm 5 ≤ 5 ≤ 6 5 ≤ 6 ≤ 6 original 1.0m slat spacing in combination with SBBC AdBm + BBC 10 ≤ 11 ≤ 11 12 ≤ 12 ≤ 13 1.00 m BBC 7 ≤ 8 ≤ 8 9 ≤ 9 ≤ 10 • Reduction of 7 dB SEL and Lpeak with the reduced 0.67m slat spacing 2 AdBm 7 ≤ 7 ≤ 8 7 ≤ 7 ≤ 8 AdBm + BBC 14 ≤ 15 ≤ 15 18 ≤ 18 ≤ 20 • Reduction of 15 dB SEL and 18 dB Lpeak with 0.67 m the original 1.0m slat spacing in combination with BBC 10 ≤ 10 ≤ 11 12 ≤ 13 ≤ 15 SBBC • Clear increase in performance due to slat reduction due to increased void fraction in water column • All reductions refer to 750m 14
Discussion UNAS Overview Satisfying first result of first full-scale field tests AdBm Versatile system with many readily implementable potential improvements • Increasing number of slats, either radially or vertically • Manual filling of resonators by near-pile bubble curtain without resonators • Integration with a near-pile bubble curtain Very robust system from an operational perspective Very high potential to be deployed at future Van Oord offshore wind projects Potential for identification of ‘problem’ frequencies for predetermined sensitive receivers to cater for more effective mitigation rather than broadband 16
FaunaGuard future developments (video) 18
Questions? Thank you for your time! Questions? 19
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