Limits...
Underwater Noise from a Wave Energy Converter Is Unlikely to Affect Marine Mammals.

Tougaard J - PLoS ONE (2015)

Bottom Line: Median sound pressure levels (Leq) in third-octave bands during operation of the converter were 106-109 dB re. 1 μPa in the range 125-250 Hz, 1-2 dB above ambient noise levels (statistically significant).A likely explanation for the low noise emissions is the construction of the converter where all moving parts, except for the absorbers themselves, are placed above water on a jack-up rig.The results may thus not be directly transferable to other wave converter designs but do demonstrate that it is possible to harness wave energy without noise pollution to the marine environment.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioscience, Aarhus University, DK-4000, Roskilde, Denmark.

ABSTRACT
Underwater noise was recorded from the Wavestar wave energy converter; a full-scale hydraulic point absorber, placed on a jack-up rig on the Danish North Sea coast. Noise was recorded 25 m from the converter with an autonomous recording unit (10 Hz to 20 kHz bandwidth). Median sound pressure levels (Leq) in third-octave bands during operation of the converter were 106-109 dB re. 1 μPa in the range 125-250 Hz, 1-2 dB above ambient noise levels (statistically significant). Outside the range 125-250 Hz the noise from the converter was undetectable above the ambient noise. During start and stop of the converter a more powerful tone at 150 Hz (sound pressure level (Leq) 121-125 dB re 1 μPa) was easily detectable. This tone likely originated from the hydraulic pump which was used to lower the absorbers into the water and lift them out of the water at shutdown. Noise levels from the operating wave converter were so low that they would barely be audible to marine mammals and the likelihood of negative impact from the noise appears minimal. A likely explanation for the low noise emissions is the construction of the converter where all moving parts, except for the absorbers themselves, are placed above water on a jack-up rig. The results may thus not be directly transferable to other wave converter designs but do demonstrate that it is possible to harness wave energy without noise pollution to the marine environment.

No MeSH data available.


Related in: MedlinePlus

The Wavestar wave energy converter, located on the Danish North Sea coast.a) Schematic drawing of the wave energy converter, placed at the end of a stone pier, about 200 m from the coast. Recordings were made at the position indicated by the star. Blue arrow indicates wave direction during measurements. b) Photo of the two absorbers during operation. Note the person next to the hydraulic piston for scale.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4492488&req=5

pone.0132391.g001: The Wavestar wave energy converter, located on the Danish North Sea coast.a) Schematic drawing of the wave energy converter, placed at the end of a stone pier, about 200 m from the coast. Recordings were made at the position indicated by the star. Blue arrow indicates wave direction during measurements. b) Photo of the two absorbers during operation. Note the person next to the hydraulic piston for scale.

Mentions: An alternative realisation of a point absorber is the Wavestar[8]. In contrast to the 1/7th scale SeaRay, the Wavestar is a full-scale test and demonstration converter. The Wavestar consists of a number of absorbers (two in the present implementation), hinged onto a four-legged jack-up platform (Fig 1). During operation the independently operating absorbers float semi-submerged in the water and wave-generated up-and-down motion is converted into hydraulic pressure by means of pistons connected to the arms of the absorbers. The hydraulic pressure generated in the pistons is rectified and drives the generator. The jack-up design allows continuous adjustment to the tide and offers storm protection. During a storm the entire platform can be jacked up to a safe height above the waves. When absorbers are taken out of operation, due to service or storm protection, they are raised completely out of the water by the hydraulic pistons.


Underwater Noise from a Wave Energy Converter Is Unlikely to Affect Marine Mammals.

Tougaard J - PLoS ONE (2015)

The Wavestar wave energy converter, located on the Danish North Sea coast.a) Schematic drawing of the wave energy converter, placed at the end of a stone pier, about 200 m from the coast. Recordings were made at the position indicated by the star. Blue arrow indicates wave direction during measurements. b) Photo of the two absorbers during operation. Note the person next to the hydraulic piston for scale.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4492488&req=5

pone.0132391.g001: The Wavestar wave energy converter, located on the Danish North Sea coast.a) Schematic drawing of the wave energy converter, placed at the end of a stone pier, about 200 m from the coast. Recordings were made at the position indicated by the star. Blue arrow indicates wave direction during measurements. b) Photo of the two absorbers during operation. Note the person next to the hydraulic piston for scale.
Mentions: An alternative realisation of a point absorber is the Wavestar[8]. In contrast to the 1/7th scale SeaRay, the Wavestar is a full-scale test and demonstration converter. The Wavestar consists of a number of absorbers (two in the present implementation), hinged onto a four-legged jack-up platform (Fig 1). During operation the independently operating absorbers float semi-submerged in the water and wave-generated up-and-down motion is converted into hydraulic pressure by means of pistons connected to the arms of the absorbers. The hydraulic pressure generated in the pistons is rectified and drives the generator. The jack-up design allows continuous adjustment to the tide and offers storm protection. During a storm the entire platform can be jacked up to a safe height above the waves. When absorbers are taken out of operation, due to service or storm protection, they are raised completely out of the water by the hydraulic pistons.

Bottom Line: Median sound pressure levels (Leq) in third-octave bands during operation of the converter were 106-109 dB re. 1 μPa in the range 125-250 Hz, 1-2 dB above ambient noise levels (statistically significant).A likely explanation for the low noise emissions is the construction of the converter where all moving parts, except for the absorbers themselves, are placed above water on a jack-up rig.The results may thus not be directly transferable to other wave converter designs but do demonstrate that it is possible to harness wave energy without noise pollution to the marine environment.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioscience, Aarhus University, DK-4000, Roskilde, Denmark.

ABSTRACT
Underwater noise was recorded from the Wavestar wave energy converter; a full-scale hydraulic point absorber, placed on a jack-up rig on the Danish North Sea coast. Noise was recorded 25 m from the converter with an autonomous recording unit (10 Hz to 20 kHz bandwidth). Median sound pressure levels (Leq) in third-octave bands during operation of the converter were 106-109 dB re. 1 μPa in the range 125-250 Hz, 1-2 dB above ambient noise levels (statistically significant). Outside the range 125-250 Hz the noise from the converter was undetectable above the ambient noise. During start and stop of the converter a more powerful tone at 150 Hz (sound pressure level (Leq) 121-125 dB re 1 μPa) was easily detectable. This tone likely originated from the hydraulic pump which was used to lower the absorbers into the water and lift them out of the water at shutdown. Noise levels from the operating wave converter were so low that they would barely be audible to marine mammals and the likelihood of negative impact from the noise appears minimal. A likely explanation for the low noise emissions is the construction of the converter where all moving parts, except for the absorbers themselves, are placed above water on a jack-up rig. The results may thus not be directly transferable to other wave converter designs but do demonstrate that it is possible to harness wave energy without noise pollution to the marine environment.

No MeSH data available.


Related in: MedlinePlus