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
Hydro-Kinetic Energy Conversion: Resource and Technology
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Division of Electricity)
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The kinetic energy present in tidal currents and other water courses has long been appreciated as a vast resource of renewable energy. The work presented in this doctoral thesis is devoted to both the characteristics of the hydro-kinetic resource and the technology for energy conversion.

An assessment of the tidal energy resource in Norwegian waters has been carried out based on available data in pilot books. More than 100 sites have been identified as interesting with a total estimated theoretical resource—i.e. the kinetic energy in the undisturbed flow—in the range of 17 TWh. A second study was performed to analyse the velocity distributions presented by tidal currents, regulated rivers and unregulated rivers. The focus is on the possible degree of utilization (or capacity factor), the fraction of converted energy and the ratio of maximum to rated velocity, all of which are believed to be important characteristics of the resource affecting the economic viability of a hydro-kinetic energy converter.

The concept for hydro-kinetic energy conversion studied in this thesis comprises a vertical axis turbine coupled to a directly driven permanent magnet generator. One such cable wound laboratory generator has been constructed and an experimental setup for deployment in the river Dalälven has been finalized as part of this thesis work. It has been shown, through simulations and experiments, that the generator design at hand can meet the system requirements in the expected range of operation. Experience from winding the prototype generators suggests that improvements of the stator slot geometry can be implemented and, according to simulations, decrease the stator weight by 11% and decrease the load angle by 17%. The decrease in load angle opens the possibility to reduce the amount of permanent magnetic material in the design.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. , 96 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1025
Keyword [en]
Tidal energy, renewable energy, vertical axis turbine, permanent magnet generator, resource assessment
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Energy Systems
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
URN: urn:nbn:se:uu:diva-195942ISBN: 978-91-554-8608-2 (print)OAI: oai:DiVA.org:uu-195942DiVA: diva2:608774
Public defence
2013-04-12, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2013-03-20 Created: 2013-03-01 Last updated: 2013-12-12Bibliographically approved
List of papers
1. A review of the tidal current energy resource in Norway
Open this publication in new window or tab >>A review of the tidal current energy resource in Norway
2009 (English)In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 13, no 8, 1898-1909 p.Article, review/survey (Refereed) Published
Abstract [en]

As interest in renewable energy sources is steadily on the rise, tidal current energy is receiving more and more attention from politicans, industrialists, and academics. In this article, the conditions for and potential of tidal currents as an energy resource in Norway are reviewed. There having been a relatively small amount of academic work published in this particular field, closely related topics such as the energy situation in Norway in general, the oceanography of the Norwegian coastline, and numerical models of tidal currents in Norwegian waters are also examined. Two published tidal energy resource assessments are reviewed and compared to a desktop study made specifically for this review based on available data in pilot books. The argument is made that tidal current energy ought to be an important option for Norway in terms of renewable energy.

Place, publisher, year, edition, pages
Elsevier, 2009
Keyword
Tidal current, Renewable energy, Ocean energy
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Oceanography, Hydrology, Water Resources Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-113144 (URN)10.1016/j.rser.2009.01.026 (DOI)000269135000012 ()1364-0321 (ISBN)
Available from: 2010-10-28 Created: 2010-01-25 Last updated: 2017-12-12Bibliographically approved
2. On the velocity distribution for hydro-kinetic energy conversion from tidal currents and rivers
Open this publication in new window or tab >>On the velocity distribution for hydro-kinetic energy conversion from tidal currents and rivers
2013 (English)In: Journal of Renewable and Sustainable Energy, ISSN 1941-7012, E-ISSN 1941-7012, Vol. 5, no 2, 023115- p.Article in journal (Refereed) Published
Abstract [en]

Tidal currents and rivers are promising sources of renewable energy given that suitable turbines for kinetic energy conversion are developed. To be economically and technically feasible, a velocity distribution that can give a high degree of utilization (or capacity factor), while the ratio of maximum to rated velocity is low would be preferable. The rated velocity is defined as the velocity at which rated power is achieved. Despite many attempts to estimate the resource, however, reports on the possible degree of utilisation from tidal currents and rivers are scarce.

In this paper the velocity distribution from a number of regulated rivers, unregulated rivers and tidal currents have been analysed regarding the degree of utilisation, the fraction of converted energy and the ratio of maximum to rated velocity. Two methods have been used for choosing the rated velocity; one aiming at a high fraction of converted energy and one aiming at a high degree of utilisation.

Using the first method, with a rated velocity close to the maximum velocity, it is unlikely that the turbine will reach the cut-out velocity. This results in, on average, a degree of utilisation of 23% for regulated rivers, 19% for unregulated rivers and 17% for tidal currents while converting roughly 30-40% of the kinetic energy. Choosing a rated velocity closer to the mean velocity resulted in, on average, a degree of utilisation of 57% for regulated rivers, 52% for unregulated rivers and 45% for tidal currents. The ratio of maximum to rated velocity would still be no higher than 2.0 for regulated rivers, 1.2 for unregulated rivers and 1.6 for tidal currents. This implies that the velocity distribution of both rivers and tidal currents is promising for kinetic energy conversion. These results, however, do not include weather related effects or extreme velocities such as the 50-year velocity. A velocity factor is introduced to describe what degree of utilisation can be expected at a site. The velocity factor is defined as the ratio U-max/U-rate at the desired degree of utilisation, and serves as an early indicator of the suitability of a site. 

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2013
Keyword
tidal currents, rivers, degree of utilisation, marine current energy, capacity factor, renewable energy, velocity factor
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-195499 (URN)10.1063/1.4795398 (DOI)000318242100037 ()
Available from: 2013-04-12 Created: 2013-02-25 Last updated: 2017-12-06Bibliographically approved
3. A low-speed generator for energy conversion from marine currents: experimental validation of simulation
Open this publication in new window or tab >>A low-speed generator for energy conversion from marine currents: experimental validation of simulation
2008 (English)In: Proceedings of the Institution of mechanical engineers. Part A, journal of power and energy, ISSN 0957-6509, E-ISSN 2041-2967, Vol. 222, no 4, 381-388 p.Article in journal (Refereed) Published
Abstract [en]

A low-speed permanent magnet (PM) cable wound generator for electrical energy conversion from marine or tidal currents has been designed and constructed. A key feature of this variable speed direct drive generator is its capability to efficiently generate electricity from tidal currents with very low velocities, in the order of 1 m/s. In arriving at an appropriate design for the generator typical characteristics of tidal currents were considered. Using these characteristics as input, and accounting for the electromagnetic losses, detailed computer simulations using a finite-element method software were carried out to come up with the final design. Various parameters that can influence the generator design are presented. An experimental set-up has been constructed based on the above-mentioned design in order to study the electrical and mechanical performance of the generator through a variety of experiments. The power input for this set-up is a variable speed motor, capable of operating the generator at rotational speeds of 0–16 r/min, representing tidal currents with very low velocities. The generator presented in this paper may be beneficial for a better understanding of an appropriate design and layout of tidal energy conversion systems.

Keyword
finite-element method, marine currents, permanent magnet generator, tidal power
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-96614 (URN)10.1243/09576509JPE567 (DOI)000258167400005 ()
Available from: 2008-01-11 Created: 2008-01-11 Last updated: 2017-12-14Bibliographically approved
4. Matching a permanent magnet synchronous generator to a fixed pitch vertical axis turbine for marine current energy conversion
Open this publication in new window or tab >>Matching a permanent magnet synchronous generator to a fixed pitch vertical axis turbine for marine current energy conversion
Show others...
2009 (English)In: IEEE Journal of Oceanic Engineering, ISSN 0364-9059, E-ISSN 1558-1691, Vol. 34, no 1, 24-31 p.Article in journal (Refereed) Published
Abstract [en]

Extracting energy from a free-flow marine current using a vertical axis fixed pitch turbine requires a generator that can handle varying speeds and loads, since such a turbine gives maximum power capture for a fixed tip speed ratio. A prototype of such a generator has been designed and constructed. In this paper, its variable speed and load operation is evaluated, both in terms of how the constructed generator performs in relation to simulations, and in terms of how the generator could perform with three different fixed pitch turbines. Measurements of root mean square (RMS) voltage and current differ 10% from simulations. Performance analysis with example turbines shows that the generator can match fixed tip speed ratio operation of several turbines for current speeds between 0.5 and 2.5 m/s.

Keyword
Fixed tip speed ratio operation, permanent magnet generators, tidal power generation, variable speed generator, vertical axis turbine
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-96617 (URN)10.1109/JOE.2008.2010658 (DOI)000264618000003 ()
Available from: 2008-01-11 Created: 2008-01-11 Last updated: 2017-12-14Bibliographically approved
5. A Permanent Magnet Generator for Energy Conversion from Marine Currents: No Load and Load Experiments
Open this publication in new window or tab >>A Permanent Magnet Generator for Energy Conversion from Marine Currents: No Load and Load Experiments
2012 (English)In: ISNR Renewable Energy, ISSN 2090-7451, Vol. 2012, 489379- p.Article in journal (Refereed) Published
Abstract [en]

This paper presents experiments and measurements on a low speed permanent magnet cable wound generator for marine currentenergy conversion.Measurements were made for no load and nominal load (4.44Ω/phase) conditions at nominal speed (10 rpm).For either load condition, the magnetic fields in the air gap were also measured. The measurements on the generator werecompared with the corresponding finite element method simulations used to design the machine. It is shown in the paper thatmeasurements and corresponding case simulations show good agreement. At nominal speed, the measured and simulated loadvoltages (nominal load) differ less than 1% for the rms values and less than 5% for peak values. At no load, measured and simulatedvoltages had larger differences, that is, <9% for rms values and <5% for peak values. Harmonic analyses of measured and simulatedphase voltages and currents show only the presence of third harmonics. The percentage of harmonics in the measured data wascomparable with the corresponding predictions of the simulations. The discussions and results presented in the paper could bebeneficial for future design of efficient and reliable marine current energy converter systems.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-176990 (URN)10.5402/2012/489379 (DOI)
Available from: 2012-06-29 Created: 2012-06-29 Last updated: 2013-03-22Bibliographically approved
6. On the Stator Slot Geometry of a Cable Wound Generator for Hydrokinetic Energy Conversion
Open this publication in new window or tab >>On the Stator Slot Geometry of a Cable Wound Generator for Hydrokinetic Energy Conversion
2015 (English)In: Scientific World Journal, ISSN 1537-744X, E-ISSN 1537-744X, 812149Article in journal (Refereed) Published
Abstract [en]

In this paper, the stator slot geometry of a cable wound permanent magnet synchronous generator for hydro-kinetic energy conversion is evaluated. When designing generators, practical experience is of great importance to result in a realizable design. Therefore, practical experience from winding two cable wound generators is used to propose optimized dimensions of different parts in the stator slot geometry. A thorough investigation is performed through simulations of how small geometrical changes alter the generator performance. Simulations are performed by using the finite element method (FEM) to solve coupled field and circuit equations. The parameter study shows that small changes in the geometry can have large affect on the performance and the generator dimensions. Furthermore, it is concluded that the load angle is especially sensitive to small geometrical changes. A new generator design is proposed which shows improved efficiency, reduced weight and a possibility to decrease the expensive permanent magnet material by almost one fifth.

Keyword
permanent magnet, synchronous generator, tidal energy, hydro-kinetic energy conversion, cable wound
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-195501 (URN)10.1155/2015/812149 (DOI)
Available from: 2013-02-25 Created: 2013-02-25 Last updated: 2017-12-06Bibliographically approved
7. Design of an experimental setup for hydro-kinetic energy conversion
Open this publication in new window or tab >>Design of an experimental setup for hydro-kinetic energy conversion
Show others...
2009 (English)In: International Journal on Hydropower & Dams, ISSN 1352-2523, Vol. 16, no 5, 112-116 p.Article in journal (Refereed) Published
Abstract [en]

A hydro-kinetic energy project has been underway in Sweden since 2000, and an in-stream prototype setup for experiments at a site in a Swedish river is now in progress. The system comprises a vertical axis turbine and a directly driven permanent magnet generator. Methods and choices used in designing the system are described here. The turbine and generator are evaluated based on measurements and CFD simulations of conditions at the site for the experimental setup.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-113145 (URN)1352-2523 (ISBN)
Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2016-04-14Bibliographically approved
8. Efficiency of a Directly Driven Generator for Hydrokinetic Energy Conversion
Open this publication in new window or tab >>Efficiency of a Directly Driven Generator for Hydrokinetic Energy Conversion
2013 (English)In: Advances in Mechanical Engineering, ISSN 1687-8132, E-ISSN 1687-8140, 978140- p.Article in journal (Refereed) Published
Abstract [en]

An experimental setup for hydrokinetic energy conversion comprising a vertical axis turbine, a directly driven permanent magnet generator, and a control system has been designed and constructed for deployment in the river Dalälven in Sweden. This paper is devoted to discussing the mechanical and electrical design of the generator used in the experimental setup. The generator housing is designed to be water tight, and it also acts as a support structure for the turbine shaft. The generator efficiency has been measured in the range of 5–16.7 rpm, showing that operation in the low velocity range up to 1.5 m/s is possible with a directly driven generator.

Keyword
permanent magnet, cable wound, tidal energy, ocean energy, generator
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-195876 (URN)10.1155/2013/978140 (DOI)000325895100001 ()
Available from: 2013-02-28 Created: 2013-02-28 Last updated: 2017-12-06Bibliographically approved

Open Access in DiVA

fulltext(4491 kB)1183 downloads
File information
File name FULLTEXT01.pdfFile size 4491 kBChecksum SHA-512
c9bbe6fae4daf37534a78c109665b708ef3b087475a707318ff6490740e16a6d416a6369542c17470db9799781acf92b03d6e8e650b28efaff11ecbac784052f
Type fulltextMimetype application/pdf
Buy this publication >>

Authority records BETA

Grabbe, Mårten

Search in DiVA

By author/editor
Grabbe, Mårten
By organisation
Electricity
Other Electrical Engineering, Electronic Engineering, Information EngineeringEnergy Systems

Search outside of DiVA

GoogleGoogle Scholar
Total: 1183 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 3103 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