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| 2. |
- Grabbe, Mårten, et al.
(författare)
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A review of the tidal current energy resource in Norway
- 2009
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 13:8, s. 1898-1909
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Forskningsöversikt (refereegranskat)abstract
- 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.
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| 3. |
- Grabbe, Mårten, et al.
(författare)
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Design of an experimental setup for hydro-kinetic energy conversion
- 2009
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Ingår i: International Journal on Hydropower & Dams. - 1352-2523. ; 16:5, s. 112-116
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Grabbe, Mårten, et al.
(författare)
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Efficiency of a Directly Driven Generator for Hydrokinetic Energy Conversion
- 2013
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Ingår i: Advances in Mechanical Engineering. - : SAGE Publications. - 1687-8132 .- 1687-8140. ; , s. 978140-
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- Grabbe, Mårten, 1979-
(författare)
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Hydro-Kinetic Energy Conversion : Resource and Technology
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 6. |
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| 7. |
- Grabbe, Mårten, et al.
(författare)
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On the Stator Slot Geometry of a Cable Wound Generator for Hydrokinetic Energy Conversion
- 2015
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Ingår i: Scientific World Journal. - : Hindawi Limited. - 1537-744X .- 2356-6140.
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Lalander, Emilia, et al.
(författare)
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On the velocity distribution for hydro-kinetic energy conversion from tidal currents and rivers
- 2013
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Ingår i: Journal of Renewable and Sustainable Energy. - : American Institute of Physics (AIP). - 1941-7012. ; 5:2, s. 023115-
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
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| 10. |
- Lundin, Staffan, et al.
(författare)
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Experimental demonstration of performance of a vertical axis marine current turbine in a river
- 2016
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Ingår i: Journal of Renewable and Sustainable Energy. - : AIP Publishing. - 1941-7012. ; 8:6
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Tidskriftsartikel (refereegranskat)abstract
- An experimental station for marine current power has been installed in a river. The station comprises a vertical axis turbine with a direct-driven permanent magnet synchronous generator. In measurements of steady-state operation in varying flow conditions, performance comparable to that of turbines designed for significantly higher flow speeds is achieved, demonstrating the viability of electricity generation in low speed (below 1.5 m/s) marine currents.
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