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Underwater radiated noise from Point Absorbing Wave Energy Converters: Noise Characteristics and Possible Environmental Effects
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Vågkraft)
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The conversion of wave energy into electrical energy has the potential to become a clean and sustainable form of renewable energy conversion. However, like all forms of energy conversion it will inevitably have an impact on the marine environment, although not in the form of emissions of hazardous substances (gases, oils or chemicals associated with anticorrosion). Possible environmental issues associated with wave energy conversion include electromagnetic fields, alteration of sedimentation and hydrologic regimes and underwater radiated noise.

Underwater noise has the potential to propagate over long distances and thus have the potential to disturb marine organisms far away from the noise source. There is great variation in the ability to perceive sound between marine organisms, one sound that is clearly audible to one species can be completely inaudible to another. Thus, to be able to determine potential environmental impact from WECs associated with underwater noise, the noise radiated from the WECs must be known. This thesis presents results from studies on the underwater radiated noise from four different full-scale WECs in the Lysekil Wave Power Project.

Hydrophones were used to measure the underwater radiated noise from operating point absorbing linear WECs. The main purpose was to study the radiated noise from the operating WECs with emphasis on characteristics such as spectrum levels, Sound Pressure Level (SPL), noise duration and repetition rate. This to be able to determine the origin of the noise and if possible, implement design changes to minimize radiated noise.

The results identified two main operational noises (transients with the bulk of the energy in frequencies <1 kHz). The SPL of the radiated noise fluctuated significantly, depending on wave height. Broadband SPLrms of the measurements ranged between ~110 dB and ~140 dB re 1 µPa and SPLpeak of specific noises ranges between ~140 and ~180 dB re µPa. Audibility was estimated range from 1km to 15 km depending critically on species and on assumptions of propagation loss. The noise is not expected to have any negative effects on behaviour or mask any signals, unless in the vicinity (<150m) of the WECs in significant wave heights. No physical damage, even in close vicinity are expected on either fish or marine mammals.

Having the aim to have as little impact on the environment a possible, these studies are important. This way precautions can be implemented early in the technical development of this kind of renewable energy converters. The benefits from the WECs the Lysekil wave power project are believed to outweigh possible environmental impacts due to underwater radiated noise.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. , 62 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1200
Keyword [en]
Wave energy conversion, renewable energy, environmental impact, marine ecology, underwater noise
National Category
Natural Sciences Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-235016ISBN: 978-91-554-9097-3 (print)OAI: oai:DiVA.org:uu-235016DiVA: diva2:758786
Public defence
2014-12-12, Häggsalen, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Note

Vid avhandlingens tryckläggning upptäcktes inte att tidpunkt för disputation var fel.

Available from: 2014-11-21 Created: 2014-10-28 Last updated: 2015-02-03
List of papers
1. Wave Energy from the North Sea: Experiences from the Lysekil Research Site
Open this publication in new window or tab >>Wave Energy from the North Sea: Experiences from the Lysekil Research Site
Show others...
2008 (English)In: Surveys in geophysics, ISSN 0169-3298, E-ISSN 1573-0956, Vol. 29, no 3, 221-240 p.Article, review/survey (Refereed) Published
Abstract [en]

This paper provides a status update on the development of the Swedish wave energy research area located close to Lysekil on the Swedish West coast. The Lysekil project is run by the Centre for Renewable Electric Energy Conversion at Uppsala University. The project was started in 2004 and currently has permission to run until the end of 2013. During this time period 10 grid-connected wave energy converters, 30 buoys for studies on environmental impact, and a surveillance tower for monitoring the interaction between waves and converters will be installed and studied. To date the research area holds one complete wave energy converter connected to a measuring station on shore via a sea cable, a Wave Rider™ buoy for wave measurements, 25 buoys for studies on environmental impact, and a surveillance tower. The wave energy converter is based on a linear synchronous generator which is placed on the sea bed and driven by a heaving point absorber at the ocean surface. The converter is directly driven, i.e. it has no gearbox or other mechanical or hydraulic conversion system. This results in a simple and robust mechanical system, but also in a somewhat more complicated electrical system.

Keyword
Wave power, Renewable energy, Sea trial, Linear generator, Point absorber, Environmental impact
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-107215 (URN)10.1007/s10712-008-9047-x (DOI)000260967900002 ()
Available from: 2009-07-29 Created: 2009-07-29 Last updated: 2017-12-13Bibliographically approved
2. Wave power - sustainable energy or environmentally costly?: A review with special emphasis on linear wave energy converters
Open this publication in new window or tab >>Wave power - sustainable energy or environmentally costly?: A review with special emphasis on linear wave energy converters
2010 (English)In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 14, no 4, 1329-1335 p.Article, review/survey (Refereed) Published
Abstract [en]

Generating electricity from waves is predicted to be a new source of renewable energy conversion expanding significantly, with a global potential in the range of wind and hydropower. Several wave power techniques are on the merge of commercialisation, and thus evoke questions of environmental concern. Conservation matters are to some extent valid independent of technique but we mainly focus on point absorbing linear generators. By giving examples from the Lysekil project, run by Uppsala University and situated on the Swedish west coast, we demonstrate ongoing and future environmental studies to be performed along with technical research and development. We describe general environmental aspects generated by wave power projects; issues also likely to appear in Environmental Impact Assessment studies. Colonisation patterns and biofouling are discussed with particular reference to changes of the seabed and alterations due to new substrates. A purposeful artificial reef design to specially cater for economically important or threatened species is also discussed. Questions related to fish, fishery and marine mammals are other examples of topics where, e.g. no-take zones, marine bioacoustics and electromagnetic fields are important areas. In this review we point out areas in which studies likely will be needed, as ventures out in the oceans also will give ample opportunities for marine environmental research in general and in areas not previously studied. Marine environmental and ecological aspects appear to be unavoidable for application processes and in post-deployment studies concerning renewable energy extraction. Still, all large-scale renewable energy conversion will cause some impact mainly by being area demanding. An early incorporation of multidisciplinary and high quality research might be a key for new ocean-based techniques.

Keyword
Artificial reef, Biofouling, Environmental impact, Offshore renewable energy, Sweden, Wave energy converters
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-107222 (URN)10.1016/j.rser.2009.11.016 (DOI)000275997200017 ()
Available from: 2009-07-29 Created: 2009-07-29 Last updated: 2017-12-13Bibliographically approved
3. Characteristics of the Operational Noise from Full Scale Wave Energy Converters in the Lysekil Project: Estimation of Potential Environmental Impacts
Open this publication in new window or tab >>Characteristics of the Operational Noise from Full Scale Wave Energy Converters in the Lysekil Project: Estimation of Potential Environmental Impacts
2013 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 6, no 5, 2562-2582 p.Article in journal (Refereed) Published
Abstract [en]

Wave energy conversion is a clean electric power production technology. During operation there are no emissions in the form of harmful gases. However there are unsolved issues considering environmental impacts such as: electromagnetism; the artificial reef effect and underwater noise. Anthropogenic noise is increasing in the oceans worldwide and wave power will contribute to this sound pollution in the oceans; but to what extent? The main purpose of this study was to examine the noise emitted by a full scale operating Wave Energy Converter (WEC) in the Lysekil project at Uppsala University in Sweden. A minor review of the hearing capabilities of fish and marine mammals is presented to aid in the conclusions of impact from anthropogenic sound. A hydrophone was deployed to the seabed in the Lysekil research site park at distance of 20 and 40 m away from two operational WECs. The measurements were performed in the spring of 2011. The results showed that the main noise was a transient noise with most of its energy in frequencies below 1 kHz. These results indicate that several marine organisms (fish and mammals) will be able to hear the operating WECs of a distance of at least 20 m.

Keyword
direct driven wave energy converter, underwater noise, environmental impact, renewable energy
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-203675 (URN)10.3390/en6052562 (DOI)000319443200013 ()
Available from: 2013-07-18 Created: 2013-07-17 Last updated: 2017-12-06Bibliographically approved
4. Hydroacoustic measurements of the radiated noise from Wave Energy Converters in the Lysekil project and project WESA
Open this publication in new window or tab >>Hydroacoustic measurements of the radiated noise from Wave Energy Converters in the Lysekil project and project WESA
2013 (English)In: Proceedings UA 2013 / [ed] John S. Papadakis & Leif Bjørnø, 2013, 199-209 p.Conference paper, Published paper (Refereed)
Abstract [en]

Field measurements of the hydroacoustic noise from Wave Energy Converters (WECs) in the Lysekil project at Uppsala University and the Project WESA (joint effort between Uppsala University (Lead Partner), Ålands Teknikkluster r.f. and University of Turku) are presented. Anthropogenic noise is increasing in the oceans world wide and wave energy conversion may contribute to this noise, but to what extent? The main objective in this study is to examine the noise from full scale operating WECs in the Lysekil and project WESA. Acoustic measurements were made in order to be able to estimate potential environmental impact. Submersible recording devices (SRD) were deployed at 1 m from WECs at a depth of approximately 24 meters. Both WECs are a full scale point absorber with a directly driven linear generator, placed on gravitation foundations at the seabed with a connected buoy at the surface that absorbs energy from the heaving waves. The SRDs used to measure the noise from the WECs, consists of a SM2-recorder from Wildlife Acoustics and hydrophones from High Tech Inc. (HTI 96 MIN and HTI 99 HF). Measurements at in the Lysekil project were carried out in the spring of 2013 and in the project WESA in Jan-Feb of 2012. Preliminary results show that the main operating noise radiated from the WEC are short transients with instant rise time when the translator moves past the stator and when the stator hits the end stop springs of the generator. Most of the power in the noise is between 20 – 1000 Hz.

Keyword
Wave Energy Converter, Underwater noise, renewable energy
National Category
Natural Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-234926 (URN)978-618-80725-0-3 (ISBN)
Conference
1st international conference and exhibition on Underwater Acoustics, UA2013, Corfu, Greece, 23rd - 28th June 2013
Projects
LysekilsprojektetProjekt WESA
Available from: 2014-10-27 Created: 2014-10-27 Last updated: 2015-02-03Bibliographically approved
5. Underwater radiated noise from direct driven Wave Energy Converters: Sound Pressure Levels in relation to Significant Wave Height and Wave Steepness
Open this publication in new window or tab >>Underwater radiated noise from direct driven Wave Energy Converters: Sound Pressure Levels in relation to Significant Wave Height and Wave Steepness
2014 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524Article in journal (Refereed) Submitted
Abstract [en]

The operation of Wave Energy Converters (WECs) will add to the anthropogenic impact on the marine environment. Underwater radiated noise is one suggested impact. To estimate if there might be an impact on the environment, the noise must be characterized. Noise from two full scale WECs was measured in 2013. The purpose of this study was to examine the change in noise levels from the WECs in different significant wave heights and wave Steepness, propagation loss and the significance of a noise dampening feature. Noise was measured simultaneously at two distances (1m and 150 m). Noise levels at 1m varied between 108-143 dB re 1 µParms in Hs 0.09-2.84m. The noise dampening feature had a significant impact on the noise levels. Noise levels increased logarithmically in relation to Hs and linearly in relation to α2. α2 was found to be an uncertain variable when used alone to estimate noise levels.

National Category
Engineering and Technology Natural Sciences
Identifiers
urn:nbn:se:uu:diva-234961 (URN)
Available from: 2014-10-27 Created: 2014-10-27 Last updated: 2017-12-05
6. Underwater radiated noise from direct driven Wave Energy Converters: Comparison between Sound Pressure Levels, Spectral levels and Noise Duration of Specific Operational Noises
Open this publication in new window or tab >>Underwater radiated noise from direct driven Wave Energy Converters: Comparison between Sound Pressure Levels, Spectral levels and Noise Duration of Specific Operational Noises
(English)Manuscript (preprint) (Other academic)
Keyword
Wave Energy Converter, Underwater noise, Spectral levels, Sound pressurel levels, Environmental Impact, Marine Ecology
National Category
Engineering and Technology Natural Sciences
Identifiers
urn:nbn:se:uu:diva-235015 (URN)
Projects
Vågkraft
Available from: 2014-10-28 Created: 2014-10-28 Last updated: 2015-02-03

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