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Wave Climate off the Swedish West Coast
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2009 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 34, no 6, 1600-1606 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents and discusses the wave climate off the Swedish west coast It is based on 8 years (1997-2004) of wave data from 13 sites, nearshore and offshore, in the Skagerrak and Kattegat. The data is a product of the WAM and SWAN wave models calibrated at one site by a wave measurement buoy. It is found that the average energy flux is approximately 5.2 kW/m in the offshore Skagerrak, 2.8 kW/m in the nearshore Skagerrak, and 2.4 kW/m in the Kattegat. One of the studied sites, i.e. site 9, is the location of a wave energy research site run by the Centre for Renewable Electric Energy Conversion at Uppsala University. This site has had a wave power plant installed since the spring of 2006, and another seven are planned to be installed during 2008. Wave energy as a renewable energy source was the driving interest that led to this study and the results are briefly discussed from this perspective.

Place, publisher, year, edition, pages
2009. Vol. 34, no 6, 1600-1606 p.
Keyword [en]
Wave climate, Wave power, Sea state, Extreme waves, Skagerrak, Kattegat
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-97856DOI: 10.1016/j.renene.2008.11.016ISI: 000264306500024OAI: oai:DiVA.org:uu-97856DiVA: diva2:172942
Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Energy from Ocean Waves: Full Scale Experimental Verification of a Wave Energy Converter
Open this publication in new window or tab >>Energy from Ocean Waves: Full Scale Experimental Verification of a Wave Energy Converter
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A wave energy converter has been constructed and its function and operational characteristics have been thoroughly investigated and published. The wave energy converter was installed in March of 2006 approximately two kilometers off the Swedish west coast in the proximity of the town Lysekil. Since then the converter has been submerged at the research site for over two and a half years and in operation during three time periods for a total of 12 months, the latest being during five months of 2008. Throughout this time the generated electricity has been transmitted to shore and operational data has been recorded. The wave energy converter and its connected electrical system has been continually upgraded and each of the three operational periods have investigated more advanced stages in the progression toward grid connection. The wave energy system has faced the challenges of the ocean and initial results and insights have been reached, most important being that the overall wave energy concept has been verified. Experiments have shown that slowly varying power generation from ocean waves is possible.

Apart from the wave energy converter, three shorter studies have been performed. A sensor was designed for measuring the air gap width of the linear generator used in the wave energy converter. The sensor consists of an etched coil, a search coil, that functions passively through induction. Theory and experiment showed good agreement.

The Swedish west coast wave climate has been studied in detail. The study used eight years of wave data from 13 sites in the Skagerrak and Kattegatt, and data from a wave measurement buoy located at the wave energy research site. The study resulted in scatter diagrams, hundred year extreme wave estimations, and a mapping of the energy flux in the area. The average energy flux was found to be approximately 5.2 kW/m in the offshore Skagerrak, 2.8 kW/m in the near shore Skagerrak, and 2.4 kW/m in the Kattegat.

A method for evaluating renewable energy technologies in terms of economy and engineering solutions has been investigated. The match between the technologies and the fundamental physics of renewable energy sources can be given in terms of the technology’s utilization. It is argued that engineers should strive for a high utilization if competitive technologies are to be developed.

Place, publisher, year, edition, pages
Uppsala: Universitetsbiblioteket, 2008. 130 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 580
Keyword
wave power, wave energy converter, sea trials, ocean energy, linear generator, point absorber, search coil, wave climate, utilization
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:uu:diva-9404 (URN)978-91-554-7354-9 (ISBN)
Public defence
2008-12-12, Polacksbackens aula, Lägerhyddsv. 2, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2008-11-21 Created: 2008-11-21 Last updated: 2012-11-09Bibliographically approved
2. Hydrodynamic Modelling for a Point Absorbing Wave Energy Converter
Open this publication in new window or tab >>Hydrodynamic Modelling for a Point Absorbing Wave Energy Converter
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Surface gravity waves in the world’s oceans contain a renewable source of free power on the order of terawatts that has to this date not been commercially utilized. The division of Electricity at Uppsala University is developing a technology to harvest this energy. The technology is a point absorber type wave energy converter based on a direct-driven linear generator placed on the sea bed connected via a line to a buoy on the surface.

The work in this thesis is focused mainly on the energy transport of ocean waves and on increasing the transfer of energy from the waves to the generator and load. Potential linear wave theory is used to describe the ocean waves and to derive the hydrodynamic forces that are exerted on the buoy. Expressions for the energy transport in polychromatic waves travelling over waters of finite depth are derived and extracted from measured time series of wave elevation collected at the Lysekil test site. The results are compared to existing solutions that uses the simpler deep water approximation. A Two-Body system wave energy converter model tuned to resonance in Swedish west coast sea states is developed based on the Lysekil project concept. The first indicative results are derived by using a linear resistive load. The concept is further extended by a coupled hydrodynamic and electromagnetic model with two more realistic non-linear load conditions.

Results show that the use of the deep water approximation gives a too low energy transport in the time averaged as well as in the total instantaneous energy transport. Around the resonance frequency, a Two-Body System gives a power capture ratio of up to 80 percent. For more energetic sea states the power capture ratio decreases rapidly, indicating a smoother power output. The currents in the generator when using the Two-Body system is shown to be more evenly distributed compared to the conventional system, indicating a better utilization of the electrical equipment. Although the resonant nature of the system makes it sensitive to the shape of the wave spectrum, results indicate a threefold increase in annual power production compared to the conventional system.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 91 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 878
Keyword
Ocean wave energy, Point absorber, Wave energy converter, Wave energy transport, Polychromatic wave, Linear generator, Resonance, Finite depth, Modelling
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Marine Engineering Oceanography, Hydrology, Water Resources
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-160319 (URN)978-91-554-8214-5 (ISBN)
Public defence
2011-12-09, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2011-11-17 Created: 2011-10-21 Last updated: 2011-11-23Bibliographically approved

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Waters, RafaelEngström, JensIsberg, JanLeijon, Mats

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