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Study of an Altered Magnetic Circuit of a Permanent Magnet Linear Generator for Wave Power
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.ORCID iD: 0000-0001-8097-0223
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Seabased Ind AB, Verkstadsgatan 4, S-45330 Lysekil, Sweden..
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
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2018 (English)In: Energies, E-ISSN 1996-1073, Vol. 11, no 1, article id 84Article in journal (Refereed) Published
Abstract [en]

The wave energy converter (WEC) studied and developed at Uppsala University in Sweden is a point absorbing buoy connected to a linear generator (LG) on the seabed. Previous studies have improved the sustainability of the generator, changing its magnets from Nd2Fe14B-magnets to ferrites. In this paper, the magnetic circuit of the linear generator is further studied. Ferrite magnets of two different types (Y30 and Y40) are studied along with different shapes of pole shoes for the system. The finite element method (FEM) simulations in a program called Ace are performed. The results show that a linear generator including both Y30 and Y40 magnets and shortened T-shaped pole shoes can generate a similar magnetic energy in the airgap as a linear generator only containing Y40 magnets and rectangular pole shoes. This shows that the magnetic circuit can be altered, opening up sizes and strengths of magnets for different retailers, and thereby possibly lowering magnet cost and transportation. This work was previously presented as a conference at the European Wave and Tidal Energy Conference (EWTEC) 2017 in Cork, Ireland; this manuscript has been carefully revised and some discussions, on magnet costs for example, have been added to this paper.

Place, publisher, year, edition, pages
2018. Vol. 11, no 1, article id 84
Keywords [en]
wave energy converter (WEC), linear generator (LG), ferrite permanent magnets (PMs), renewable energy sources
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:uu:diva-348930DOI: 10.3390/en11010084ISI: 000424397600084OAI: oai:DiVA.org:uu-348930DiVA, id: diva2:1201543
Funder
Swedish Research Council, 2015-03126Swedish Energy Agency, P42243-1Available from: 2018-04-26 Created: 2018-04-26 Last updated: 2023-08-28Bibliographically approved
In thesis
1. Wave Powered Desalination
Open this publication in new window or tab >>Wave Powered Desalination
2018 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this licentiate thesis is to investigate opportunities to produce fresh-water and electricity using marine renewable energy sources, such as wave power and marine current power, for water scarce areas. It summarizes the ongoing work within the field and suggests some possibilities of future re-search. Specifically, the desalination process reverse osmosis has been dis-cussed in combination with the wave energy concept designed at Uppsala Uni-versity for a site by the Kenyan coast. A review on wave powered desalination systems was presented, and the wave climate of the Kenyan coast was reana-lyzed and discussed with respect to the wave power and desalination applica-tion. Also, the magnetic circuit of the linear generator was investigated, as well as the control of the system, to enhance its sustainability. Moreover, the marine current energy converter designed at Uppsala University was investi-gated for desalination purposes. Only literature studies and simulations were performed, and the research would benefit from experimental work.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2018
Series
UURIE / Uppsala University, Department of Engineering Sciences, ISSN 0349-8352 ; 354-18L
Keywords
wave power, desalination, marine renewable energy sources, marine current, freshwater
National Category
Energy Engineering
Research subject
Engineering Science
Identifiers
urn:nbn:se:uu:diva-369356 (URN)
Presentation
2018-11-15, 2005 Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 2015-03126StandUp
Available from: 2018-12-12 Created: 2018-12-12 Last updated: 2020-05-15Bibliographically approved
2. Wave Power for Desalination
Open this publication in new window or tab >>Wave Power for Desalination
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This doctoral thesis presents work related to wave powered desalination. Wave power for desalination could be an interesting alternative for islands or coastal regions facing freshwater shortage, and several systems have been proposed in literature. However, desalination is a process which demands a lot of energy. Studies presented in the thesis indicate that the wave energy converter designed at Uppsala University in Sweden could be used for desalination. This wave energy converter includes a floating buoy connected via a wire to a linear generator. The linear generator has magnets mounted on its movable part (the translator). Small-scale experiments have been included, indicating that intermittent renewable energy sources, such as wave power, could be used for reverse osmosis desalination. Moreover, hybrid systems, including several different renewable energy sources, could be investigated for desalination. There may be interesting minerals in the desalination brine. The thesis also includes investigations on the magnetic material inside the linear generator, as well as on control strategies for wave energy converters. An opportunity of including different types of ferrites in the linear generator has been analyzed. The thesis also presents pedagogic development projects for the electro engineering education at Uppsala University, suggesting that including a greater variability and more student-centered learning approaches could be beneficial.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2020. p. 59
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1959
Keywords
Wave power, desalination, freshwater, engineering education, linear generator, wave energy converter
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-417998 (URN)978-91-513-0995-8 (ISBN)
Public defence
2020-10-16, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2020-09-25 Created: 2020-08-28 Last updated: 2020-10-06
3. On the System Optimization of Magnetic Circuit with Alternative Permanent Magnets and its Demagnetization
Open this publication in new window or tab >>On the System Optimization of Magnetic Circuit with Alternative Permanent Magnets and its Demagnetization
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Permanent magnet (PM) machines are often associated with the usage of rare earth magnets, due to their high energy density. One such rare earth magnet is the neodymium-iron-boron (NdFeB), which is mainly produced in China. Due to the global scarcity of the rare earth magnets, much interest is put into utilizing other permanent magnet materials. Among those materials is the category of ferrite permanent magnets, known for having lower magnetic properties than NdFeB. Ferrites share some of the properties with NdFeB that makes simulations simpler, namely that they have, at least, partly linear behavior in the demagnetization curve. The lower coercive properties of ferrites can, however, force them more easily into the non-linear regions of the demagnetization curves, resulting in a gradual irreversible demagnetization that lowers the performance of the ferrites. 

In this thesis, the magnetic circuits of electrical machines with ferrites are investigated. The implications of the reduced coercive properties are studied and means to account for the irreversible demagnetization when designing the magnetic circuit. An optimization methodology for the magnetic circuit in a linear generator is developed and presented. It is found that the coercive properties may influence the PM geometry, for the given penalty for demagnetization. By proper pole shoe design, one can reduce the inclination angle of the magnetic fields inside the PMs. The difference in topology between the surface mounted NdFeB and the buried ferrites is studied regarding the inherent longitudinal end forces of linear machines. It is found that the end forces can be reduced under both no-load and load by alterations of the stator ends.  Electrical machine simulations in finite element software are often done in a two-dimensional cross section of the machine. The difference between the two-dimensional cross section and the more accurate three-dimensional model is investigated, showing that the magnetic end leakage flux in the end regions can cause a discrepancy between the two models. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2021. p. 84
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2034
Keywords
Permanent magnet machines, Finite element method, ferrite permanent magnets, linear machines
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-439815 (URN)978-91-513-1190-6 (ISBN)
Public defence
2021-06-03, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency, 42243-1
Note

Join defence on Zoom: https://uu-se.zoom.us/j/69391513482

Passcode: 794049 

Contact: Jonathan Sjölund (jonathan.sjolund@angstrom.uu.se)

Available from: 2021-05-11 Created: 2021-04-11 Last updated: 2021-05-25

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Leijon, JenniferSjölund, JonathanBoström, CeciliaEriksson, SandraTemiz, IrinaLeijon, Mats

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