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| 3. |
- Leijon, Jennifer, et al.
(författare)
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Marine renewable energy sources for desalination, generating freshwater and lithium
- 2019
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Ingår i: Proceedings of the International Offshore and Polar Engineering Conference. - 1098-6189 .- 1555-1792. ; 1, s. 562-568
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Konferensbidrag (refereegranskat)abstract
- A novel concept is presented on lithium extraction of desalination from marine renewable energy sources. The wave-and marine current energy converters designed at Uppsala University in Sweden are evaluated as potential drivers of desalination processes, off-grid, for both local lithium extraction and freshwater production. Also, aqueous mining for other minerals is briefly discussed. Calculations, estimating the freshwater and lithium production from desalination plants powered by marine renewable energy sources, are presented. It is estimated that a medium-sized desalination plant, producing 7500 m3/day, could also generate 1.28 kg lithium daily, utilizing reverse osmosis desalination and electrodialysis, powered by marine energy converter parks. To the best of our knowledge, this concept has never previously been suggested in literature.
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| 4. |
- Leijon, Jennifer, et al.
(författare)
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Study of an Altered Magnetic Circuit of a Permanent Magnet Linear Generator for Wave Power
- 2018
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- Parwal, Arvind, et al.
(författare)
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Experimental Test of Grid Connected VSC to Improve the Power Quality in a Wave Power System
- 2018
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Ingår i: 2018 5th International Conference on Electric Power and Energy Conversion Systems, EPECS 2018. - 9781538664575
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Konferensbidrag (refereegranskat)abstract
- This paper provides an overview of electric power conversion system installed at the Lysekil research site, located at the west coast of Sweden. The electric power conversion system consists of rectifiers, rectifying the power from the wave energy converters, a DC-link and a grid-tied inverter. The paper focuses on the performance of the inverter and the filter and presents experimental results obtained during the grid integration.
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| 6. |
- Parwal, Arvind, et al.
(författare)
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Grid integration and a power quality assessment of a wave-energy park
- 2019
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Ingår i: IET Smart Grid. - UK : Institution of Engineering and Technology (IET). - 2515-2947. ; 2:4, s. 625-634
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a step toward the grid connection of a wave-energy park through an electric power conversion system (EPCS) developed and installed for the wave-energy harvesting in Lysekil, Sweden. The EPCS comprises a rectifier, a DC bus, and an inverter followed by a harmonic filter (HF). The higher- and lower-order harmonics injected by the inverter in a power quality context are investigated. The lower-order voltage harmonics partially distort the voltage-source inverter output grid current. A phase-locked loop-based (PLL) grid-phase tracking is used to attenuate the lower-order harmonics by reflecting the grid harmonics in the inverter output. An expression for the grid-current harmonics as a function of the grid-voltage harmonics has been derived and implemented. A mathematical model is derived to obtain a transfer function for the PLL, and finally, proportional–integral gains are tuned for stable system operation. An HF for mitigating the higher-order harmonics has been implemented. The total harmonic distortion is evaluated experimentally, and the results fulfil the grid-code requirements at various frequencies and harmonic orders.
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| 7. |
- Apelfrojd, Senad, et al.
(författare)
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A Back-to-Back 2L-3L Grid Integration of a Marine Current Energy Converter
- 2015
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 8:2, s. 808-820
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Tidskriftsartikel (refereegranskat)abstract
- The paper proposes a back-to-back 2L-3L grid connection topology for a marine current energy converter. A prototype marine current energy converter has been deployed by a research group at Uppsala University. The concept behind the prototype revolves around a fixed pitch vertical axis turbine directly connected to a permanent magnet synchronous generator (PMSG). The proposed grid connection system utilizes a well known and proven two level voltage source converter generator-side combined with a three-level cascaded H-bridge (CHB) multilevel converter grid-side. The multilevel converter brings benefits in terms of efficiency, power quality and DC-link utilization. The system is here presented for a single marine current energy converter but can easily be scaled up for clusters of marine current energy converters. Control schemes for both grid-side and generator-side voltage source converters are presented. The start-up, steady state and dynamic performance of the marine current energy converter are investigated and simulation results are presented in this paper.
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| 8. |
- Apelfröjd, Senad, et al.
(författare)
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Experimental Verification of a Back-to-Back 2L-3L Grid Connection System for a Marine Current Energy Converter
- 2016
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Konferensbidrag (refereegranskat)abstract
- Rivers, tides and other ocean currents are renewable energy sources with great potential across the globe.A research group at Uppsala University is working on converting the power in rivers and ocean tidesusing a vertical axis turbine with a directly driven permanent magnet generator. The concept in focususes an omnidirectional, fixed pitch vertical axis turbine directly connected to a permanent magnetgenerator. Few moving parts and an overall low mechanical complexity is the main idea behind theconcept. A first full prototype was deployed in 2013 in the river Dalälven in the town of Söderfors. Thework presented here is a step towards grid connection of the marine current energy converter prototype.A back-to-back 2L-3L grid connection topology has been proposed. The system is adapted to the scaledprototype but is intended for larger turbines. The proposed grid connection system utilizes a three-levelcascaded H-Bridge voltage source converter (3L-CHBVSC) on the grid side together with a well knowtwo-level voltage source converter on the generator side. The use of a multilevel converter brings severaladvantages such as higher efficiency, more sinusoidal voltages and currents and smaller grid filtersamong other advantages. The proposed grid connection system has been constructed in the laboratory.The work presented here aims to evaluate the system in the laboratory. A synchronous generator with avery similar design to the on-site generator is used for the tests. The generator, driven by an inductionmotor, is connected to the system and power is successfully transferred to the grid. The conducted testsare used to verify the functionality of the system before installation at the research site.
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| 9. |
- Baudoin, Antoine, 1984-, et al.
(författare)
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Thermal Rating of a Submerged Substation for Wave Power
- 2016
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Ingår i: IEEE Transactions on Sustainable Energy. - 1949-3029 .- 1949-3037. ; 7:1, s. 436-445
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Tidskriftsartikel (refereegranskat)abstract
- The costs of offshore maintenance operations put high reliability-requirements on offshore equipment for ocean energy, especially on submerged ones. Thermal management is thus essential in the design of the prototypes of a marine substation, developed at Uppsala University, for grid interface of wave power parks. The cooling system itself should be efficient as well as reliable. Therefore, the feasibility of a completely passive cooling strategy was evaluated. The studied substation includes various power components, which dissipate heat and are installed in one pressurized vessel. Thermal cross-coupling was investigated with 3-D submodels and a thermal network model. An electric circuit was coupled to determine the rated power of the substation. The results depend mainly on the dc-voltage, the seawater temperature, and the thermal contact between the components and the hull.
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| 10. |
- Carpman, Nicole
(författare)
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Marine Current Resource Assessment : Measurements and Characterization
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increasing interest in converting energy from renewable resources into electricity has led to an increase in research covering the field of marine current energy, mainly concerning tidal currents and in-stream tidal turbines. Tides have the advantage of being predictable decades ahead. However, the tidal resource is intermittent and experiences local variations that affect the power output from a conversion system. The variability is mainly due to four aspects: the tidal regime, the tidal cycle, bathymetry at the site and weather effects. Each potential site is unique, the velocity flow field at tidal sites is highly influenced by local bathymetry and turbulence. Hence, characterizing the resource requires careful investigations and providing high quality velocity data from measurement surveys is of great importance. In this thesis, measurements of flow velocities have been performed at three kinds of sites.A tidal site has been investigated for its resource potential in one of all of the numerous fjords in Norway. Measurements have been performed to map the spatial and temporal variability of the resource. Results show that currents in the order of 2 m/s are present in the center of the channel. Furthermore, the flow is highly bi-directional between ebb and flood flows. The site thus have potential for in-stream energy conversion. A model is proposed that predicts peak current speed from information on tidal range at the site. A corresponding model can be set up and implemented at other similar sites affected by tides, i.e. fjord inlets connecting the ocean to a fjord or a basin.A river site serves as an experimental site for a marine current energy converter that has been designed at Uppsala University and deployed in Dalälven, Söderfors. The flow rate at the site is regulated by an upstream hydrokinetic power plant nearby, making the site suitable for experiments on the performance of the vertical axis turbine in its natural environment. The turbine has been run in uniform flow and measurements have been performed to characterize the extent of the wake.An ocean current site was a target of investigation for its potential for providing utilizable renewable energy. A measurement campaign was conducted, mapping the flow both spatially and temporally. However, the site was shown to not be suitable for energy conversion using present technique.
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