uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
A wave power unit
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.
Show others and affiliations
2009 (English)Patent (Other (popular science, discussion, etc.))
Place, publisher, year, edition, pages
2009.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-140112OAI: oai:DiVA.org:uu-140112DiVA: diva2:383037
Patent
WO 2010/085188 (2010-07-29)
Available from: 2011-01-04 Created: 2011-01-04 Last updated: 2016-04-14Bibliographically approved
In thesis
1. Electrical Systems for Wave Energy Conversion
Open this publication in new window or tab >>Electrical Systems for Wave Energy Conversion
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Wave energy is a renewable energy source with a large potential to contribute to the world's electricity production. There exist several technologies on how to convert the energy in the ocean waves into electric energy. The wave energy converter (WEC) presented in this thesis is based on a linear synchronous generator. The generator is placed on the seabed and driven by a point absorbing buoy on the ocean surface. Instead of having one large unit, several smaller units are interconnected to increase the total installed power.

To convert and interconnect the power from the generators, marine substations are used. The marine substations are placed on the seabed and convert the fluctuating AC from the generators into an AC suitable for grid connection.

The work presented in the thesis focuses on the first steps in the electric energy conversion, converting the voltage out from the generators into DC, which have an impact on the WEC's ability to absorb and produce power. The purpose has been to investigate how the generator will operate when it is subjected to different load cases and to obtain guidelines on how future systems could be improved. Offshore experiments and simulations have been done on full scale generators connected to four different loads, i.e. one linear resistive load and three different non-linear loads representing different cases for grid connected WECs.

The results show that the power can be controlled and optimized by choosing a suitable system for the WEC. It is not obvious which kind of system is the most preferable, since there are many different parameters that have an impact on the system performance, such as the size of the buoy, how the generator is designed, the number of WECs, the highest allowed complexity of the system, costs and so on. Therefore, the design of the electrical system should preferably be carried out in parallel with the design of the WEC in order to achieve an efficient system.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 104 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 797
Keyword
Wave power, direct driven linear generators, electrical systems, non-linear loads
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-140116 (URN)978-91-554-7982-4 (ISBN)
Public defence
2011-02-18, Polhemsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Note

Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 727

Available from: 2011-01-28 Created: 2011-01-04 Last updated: 2013-05-17Bibliographically approved
2. Experimental Measurement of Lateral Force in a Submerged Single Heaving Buoy Wave Energy Converter
Open this publication in new window or tab >>Experimental Measurement of Lateral Force in a Submerged Single Heaving Buoy Wave Energy Converter
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The search for new solutions for the generation of energy is becoming more and more important for our future. Big arguments and disagreements on e.g. the questions of gas transport or the dependence on energy supplied by other countries raise demands on the development of new forms of alternative energy resources. Wave power is one of the main sources of renewable energy due to the high power density stored in ocean waves.

Nevertheless, the dynamic forces of waves are so large that serious questions popped up on how to design a system which could work even in an unfavourable wave climate or could at least retain working capabilities after big storms without significant damages.

This thesis studies the reliability of the mechanical parts of a linear direct driven permanent magnet generator. The results of offshore experiment where strain gauge sensors instrumented on the capsule and the inner framework structure are presented. Stress estimation analyses using strain gauges are carried out. A method for measuring forces and moments in the mechanical structure of the WEC is developed.

Evaluation of the lateral force acting on the outer structure is a key factor for the design and construction of the WEC. A method for the measurement of the lateral force acting on the capsule has been developed.

A study of the inclination angle between the Wave Energy Converter and the floating buoy has been carried out.

The aim of this work is to contribute to the development of wave energy conversion system, and especially to the estimation of structural loads which are important for the survivability of the system under hard sea states.

This work is a step that may influence future design of wave energy devices in terms of material aspect, survivability in a hard wave climate and cost-effective renewable energies.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 99 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 886
Keyword
Wave energy converter, Tight mooring system, Offshore measurement, Strain gauge, Estimation of stress, Lateral force, Inclination angle, Snatch load
National Category
Energy Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-159519 (URN)978-91-554-8240-4 (ISBN)
Public defence
2012-02-03, Häggsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2012-01-12 Created: 2011-10-03 Last updated: 2012-01-16Bibliographically approved
3. Experimental results from the Lysekil Wave Power Research Site
Open this publication in new window or tab >>Experimental results from the Lysekil Wave Power Research Site
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents how experimental results, from wave power research performed offshore at the Lysekil research site, were obtained. The data were used to verify theoretical models as well as evaluate the feasibility of wave power as a future sustainable energy source.

The first experiments carried out at the research site was the measurement of the force in a line where one end was connected to a buoy with a diameter of 3 m and the other end to a set of springs with limited stroke length. The system is exposed to high peak forces compared to average forces. The maximum measured force in the line, when the buoy motion is limited by a stiff stopper rope is ten times the average force in that particular sea state.

The experiment performed on the first wave energy converter tested at the Lysekil Research Site is described. The infrastructure of the site is presented where the central connection point is the measuring station. The key finding is that it is possible to transform the motions of ocean waves into electrical energy and distribute it to land.

Many wave energy converters must be interconnected if large amounts of energy are to be harvested from the waves. The first submerged substation intended for aggregation of energy from wave power converters is described, with focus on the measurement and control system placed inside the substation. During this experiment period the generators were equipped with many different sensors; these measurements are explained in the thesis.

The system that aggregates power from the studied wave energy converter is regularly exposed to peak power of up to 20 times the maximum average output from the converter.

Vertical and horizontal movement of the buoy has been measured in different ways. The result is that the vertical displacement of the buoy can be measured with a simple accelerometer circuit but it is much more complicated to measure the horizontal displacement. A special method for measuring the horizontal displacement has been implemented by measuring the strain in the enclosure and the force in the line.

Abstract [sv]

Den här avhandlingen berättar om hur experimenten vid Lysekils forskningsområde för vågkraft har utförts. Insamlade mätdata har använts för att verifiera teoretiska samband som modulerats vid Elektricitetslära, Uppsala universitet. De teoretiska och praktiska resultaten har visat på att vågkraft har förutsättningarna att implementeras som en hållbar framtida energikälla. Intressanta mätmetoder har utvecklas och påfrestningarna  på utrustningin och dess samband med medel effekten har studerats.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 101 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 957
Keyword
Wave power, Lysekil, Marine Substation, Offshore measurement, strain gauge, lateral force, Invlination and azimuth angles, Wave energy converter, Temperature measurements, Inverter, Energy, Control sustem, CompactRIO, Vågkraft, Mätteknik, Styrsystem, Lysekil
National Category
Marine Engineering Energy Systems Other Electrical Engineering, Electronic Engineering, Information Engineering Ocean and River Engineering Control Engineering
Research subject
Engineering Science
Identifiers
urn:nbn:se:uu:diva-179098 (URN)978-91-554-8433-0 (ISBN)
Public defence
2012-09-28, Polhem Å 10134, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Opponent
Supervisors
Projects
Lysekils projektet
Funder
Swedish Research Council, grant no. 621-2009-3417
Available from: 2012-09-05 Created: 2012-08-07 Last updated: 2013-01-22
4. Linear wave energy converter: Study of electromagnetic design
Open this publication in new window or tab >>Linear wave energy converter: Study of electromagnetic design
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The thesis presents results from synchronous linear wave energy converters developed at Uppsala University. A study is done on closed stator slots and a study presenting offshore data focusing on the power absorption from a wave energy converter (WEC). The first step in studying the closed slots has been done during no-load, to study the magnetic flux path from the permanent magnets and to study the forces in the linear generator. The initial studies show a reduction in cogging force and a reduction in harmonics in the magnetic flux density in the air-gap. It also shows an increase of the total flux entering the stator and an increase in flux leakage. The study has been done with FEM simulations and compared with analytical calculations.

The second study was done to investigate the power absorption of a WEC in upward and downward motion in relation to the volume of the buoy and mass of the system. The experimental results were compared with a static model focusing on the limit in the absorption. As expected from the model, the WEC absorbs more energy in the upward direction. Also indications of snatch load were observed. Within this thesis, results from a comparison study between two WECs with almost identical electrical properties and the same volume of the buoy, but with different height and diameter have been presented. Moreover, experimental studies including the conversion step between AC to DC have been done.

The work done in this thesis is a part of a larger wave power project at Uppsala University. Where everything between the energy absorption from the waves to the connection to the electrical grid is studied. The project has a test-site at the west coast of Sweden near the town Lysekil, where wave energy research has been carried out since 2004.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2014. 62 p.
Series
UURIE / Uppsala University, Department of Engineering Sciences, ISSN 0349-8352 ; 335-14L
Keyword
Wave energy, permanent magnets, linear generator, closed stator slots, offshore experiments
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-237522 (URN)
Presentation
(English)
Opponent
Supervisors
Funder
Swedish Research Council, 2009-3417
Available from: 2014-12-11 Created: 2014-12-03 Last updated: 2014-12-11Bibliographically approved
5. Theoretical and Experimental Analysis of Operational Wave Energy Converters
Open this publication in new window or tab >>Theoretical and Experimental Analysis of Operational Wave Energy Converters
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis studies wave energy converters developed at Uppsala University. The wave energy converters are of point absorbing type with direct driven linear generators. The aim has been to study generator design with closed stator slots as well as offshore experimental studies.

By closing the stator slots, the harmonic content in the magnetic flux density is reduced and as a result the cogging forces in the generator are reduced as well. By reducing these forces, the noise and vibrations from the generator can be lowered. The studies have shown a significant reduction in the cogging forces in the generator. Moreover, by closing the slots, the magnetic flux finds a short-cut through the closed slots and will lower the magnetic flux linking the windings.

The experimental studies have focused on the motion of the translator. The weight of the translator has a significant impact on the power absorption, especially in the downward motion. Two different experiments have been studied with two different translator weights. The results show that with a higher translator weight the power absorption is more evenly produced between the upward and downward motion as was expected from the simulation models. Furthermore, studies on the influence of the changing active area have been conducted which show some benefits with a changing active area during the downward motion. The experimental results also indicate snatch-loads for the wave energy converter with a lower translator weight.

Within this thesis results from a comparative study between two WECs with almost identical properties have been presented. The generators electrical properties and the buoy volumes are the same, but with different buoy heights and diameters. Moreover, experimental studies including the conversion from AC to DC have been achieved.

The work in this thesis is part of a larger wave power project at Uppsala University. The project studies the whole process from the energy absorption from the waves to the connection to the electrical grid. The project has a test-site at the west coast of Sweden near the town of Lysekil, where wave energy systems have been studied since 2004.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 67 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1339
Keyword
ocean wave energy, WEC, permanent magnet, linear generator, closed stator slots, offshore experiments
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-274635 (URN)978-91-554-9460-5 (ISBN)
Public defence
2016-03-11, Häggsalen, Ångström, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2016-02-18 Created: 2016-01-24 Last updated: 2016-03-09

Open Access in DiVA

No full text

Authority records BETA

Leijon, MatsBoström, CeciliaLejerskog, ErikRahm, MagnusSvensson, Olle

Search in DiVA

By author/editor
Leijon, MatsBoström, CeciliaLejerskog, ErikRahm, MagnusSvensson, Olle
By organisation
Electricity
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 587 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf