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Studies of a Vertical Axis Turbine for Marine Current Energy Conversion: Electrical system and turbine performance
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. 198508136911. (Marine Current Power)
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ocean energy is a field of growing interest when it comes to renewable energy thanks to its high density of energy per unit area, and to the high predictability. Conversion of hydrokinetic energy, found in marine currents, is the utilization of the energy in free-flowing water for conversion to electric energy. This thesis presents experimental data from a test site with a marine current converter.

The converter system features a vertical axis turbine directly connected to a permanent magnet synchronous generator placed on the riverbed. The converter is controlled by an electrical system. The focus of the work is to evaluate power control methods and turbine performance.  

Results of a simple voltage control system is presented and compared with operation without control. The turbine type in the converter system is not self-starting. The startup power and energy has been investigated through experiments. The converter system has been connected to the local electric utility grid and the first experimental results are presented.  

The performance of the turbine for a range of water speeds is investigated. The range of experiments are limited by the water velocity at the experimental site. To address the issue, a simulation model coupling the electrical system and hydrodynamic model into one has been validated. One factor affecting the turbine's power capture is the angle of the blade pitch relative to the water flow. The influence of blade pitch on turbine performance is studied with experiments and two 3D simulation models.

The possibilities of powering a desalination plant using marine current converters is discussed. Water speed data from outside the east coast of South Africa has been used for a case study. The study investigates how many people can early be supplied with freshwater using the converter system at the experimental site as a model. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. , p. 77
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1739
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
URN: urn:nbn:se:uu:diva-363256ISBN: 978-91-513-0491-5 (print)OAI: oai:DiVA.org:uu-363256DiVA, id: diva2:1258678
Public defence
2018-12-13, 80101, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2018-11-21 Created: 2018-10-25 Last updated: 2018-11-30
List of papers
1. The Söderfors Project: Experimental Hydrokinetic Power Station Deployment and First Results
Open this publication in new window or tab >>The Söderfors Project: Experimental Hydrokinetic Power Station Deployment and First Results
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2013 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The Division of Electricity at Uppsala University recently deployed an experimental hydrokinetic power station for in-stream experiments at a site in a river. This paper briefly describes the deployment process and reports some initial results from measurements made at the test site.

Keywords
Marine Current Power, Renewable energy, Söderfors, Strömkraft, Förnybar energi, Söderfors
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-209220 (URN)
Conference
10th European Wave and Tidal Energy Conference (EWTEC), 2-5 september, 2013, Aalborg, Denmark
Projects
Marine Current Power
Funder
StandUpSwedish Research Council, 621-2009-4946
Available from: 2013-10-15 Created: 2013-10-15 Last updated: 2018-10-25Bibliographically approved
2. Experimental Results of a Load-Controlled Vertical Axis Marine Current Energy Converter
Open this publication in new window or tab >>Experimental Results of a Load-Controlled Vertical Axis Marine Current Energy Converter
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis investigates the load control of a marine current energy converter using a vertical axis turbine mounted on a permanent magnet synchronous generator. The purpose of this thesis is to show the work done in the so far relatively uncharted territory of control systems for hydro kinetic energy conversion. The work is in its early stage and is meant to serve as a guide forfuture development of the control system.

An experimental power station has been deployed and the first results are presented.

A comparison between three load control methods has been made; a fixedAC load, a fixed pulse width modulated DC load and a DC bus voltage control of a DC load. Experimental results show that the DC bus voltage control reduces the variation of rotational speed with a factor of 3.5. For all three cases, the tip speed ratio of the turbine can be kept close to the expected optimal tip speed ratio. However, for all three cases the average extracted power was significantly lower than the average power available in the turbine times the estimated maximum power coefficient. A maximum power point tracking system, with or without water velocity measurement, should increase the average extracted power.

A simulation model has been validated using experimental data. The simulated system consists of the electrical system and a hydrodynamic vortex model for the turbine. Experiments of no load operation were conducted to calibrate the drag losses of the turbine. Simulations were able to predict the behaviour in a step response for a change in tip speed ratio when the turbine was operated close to optimal tip speed ratio. The start position of the turbine was varied in the simulation to view the influence on the step response from a changed turbine position relative to the direction of the water flow.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2015. p. 53
Series
UURIE / Uppsala University, Department of Engineering Sciences, ISSN 0349-8352 ; 345-15L
Keywords
Marine Current; Vertical Axis; Load Control;
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-268867 (URN)
Presentation
2015-12-16, Å4101, Lägerhyddsvägen 1, Ångströmlaboratoriet, Uppsala, 09:15 (English)
Opponent
Supervisors
Funder
StandUpÅForsk (Ångpanneföreningen's Foundation for Research and Development)Vattenfall ABSwedish Research CouncilSwedish Energy Agency
Note

Funders: J Gust Richert, Bixia Miljöfond

Available from: 2015-12-10 Created: 2015-12-10 Last updated: 2018-10-25Bibliographically approved
3. Power And Energy Needed For Starting A Vertical Axis Marine Current Turbine
Open this publication in new window or tab >>Power And Energy Needed For Starting A Vertical Axis Marine Current Turbine
2017 (English)Conference paper, Published paper (Refereed)
Abstract [en]

A marine current power station has been deployed in Söderfors, Sweden. It comprises a five bladed fixed pitch vertical axis H-rotor turbine directly connected to a permanent magnet synchronous generator. The turbine is rated for 1.3 m/s, but at lower water speeds the turbine is generally not self starting. This paper investigates the energy and power needed to at low speeds start the turbine electrically with a BrushLess DC (BLDC) motor until  he turbines gives a net positive torque to the generator. A range of startup BLDC powers have been investigated. It is shown that for three water speeds (0.98 m/s, 1.04 m/s and 1.16 m/s) the energy needed for start up is equivalent to less than 1.2 s of power production at maximum power capture of the turbine. The startup time is mostly dependent on BLDC power setting, not on water speed. A BLDC power of 1/7th of rated power of the machine is enough to start the machine within 2 seconds. The results suggest that a higher BLDC power than that will not significantly reduce the startup time nor reduce the energy needed (increase the efficiency of the startup process). The water speed has the highest impact on the time it takes to recover the energy needed for startup once the BLDC power is well above the losses in the system.

Keywords
Marine current power, startup energy, Söderfors, vertical axis turbine
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-330188 (URN)
Conference
Proceedings of the 12th European Wave and Tidal Energy Conference 27th Aug -1st Sept 2017, Cork, Ireland
Projects
Marine Current Power
Funder
Vattenfall ABStandUpÅForsk (Ångpanneföreningen's Foundation for Research and Development)Swedish Energy AgencySwedish Research Council
Available from: 2017-09-27 Created: 2017-09-27 Last updated: 2018-10-25Bibliographically approved
4. First Experimental Results of a Grid Connected Vertical Axis Marine Current Turbine using a Multilevel Power Converter
Open this publication in new window or tab >>First Experimental Results of a Grid Connected Vertical Axis Marine Current Turbine using a Multilevel Power Converter
2018 (English)Conference paper, Published paper (Refereed)
Abstract [en]

An experimental marine current power station has been deployed in Söoderfors, Sweden. It comprises a vertical axis turbine directly connected to a permanent magnet synchronous generator rated at 7.5 kW. The generator is controlled by a Back-To-Back 2L-3L Cascaded H-Bridge full scale bi-directional Power Converter located on shore. This paper presents the first test results of the power converter, including grid connection. The startup of  the turbine, power extraction and initial active power injection to the grid, at 50 % of rated power, operated as predicted by laboratory experiments and simulations. After 40 seconds of grid connection the safety system disconnect the grid converter due to high currents injected to the grid. The problem is mostly likely associated with the current controller in the dq0 frame. Further tuning of the PI regulators and the potential addition of an anti-windup could mitigate the control issue.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-360576 (URN)
Conference
4th Asian Wave and Tidal Energy Conference (AWTEC). Taipei, Taiwan, 9-13 September 2018.
Funder
StandUpÅForsk (Ångpanneföreningen's Foundation for Research and Development)Swedish Research CouncilSwedish Energy AgencyVattenfall AB
Available from: 2018-09-14 Created: 2018-09-14 Last updated: 2018-10-25Bibliographically approved
5. Experimental demonstration of performance of a vertical axis marine current turbine in a river
Open this publication in new window or tab >>Experimental demonstration of performance of a vertical axis marine current turbine in a river
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2016 (English)In: Journal of Renewable and Sustainable Energy, ISSN 1941-7012, E-ISSN 1941-7012, Vol. 8, no 6, article id 064501Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Ocean currents, electric currents, rivers, hydrodynamics, torque
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Ocean and River Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-280762 (URN)10.1063/1.4971817 (DOI)000390115300019 ()
Projects
Marin strömkraft
Funder
Vattenfall ABÅForsk (Ångpanneföreningen's Foundation for Research and Development)StandUp
Note

Övriga finansiärer: J. Gust. Richert Memorial Fund och Bixia Environmental Fund.

Available from: 2016-03-15 Created: 2016-03-15 Last updated: 2018-10-25Bibliographically approved
6. Validation of a Coupled Electrical and Hydrodynamic Simulation Model For A Vertical Axis Marine Current Energy Converter
Open this publication in new window or tab >>Validation of a Coupled Electrical and Hydrodynamic Simulation Model For A Vertical Axis Marine Current Energy Converter
2018 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, article id 3067Article in journal (Refereed) Published
Abstract [en]

This paper validates a simulation model for a Vertical Axis Turbine connected to a Permanent Magnet Synchronous Generator in a direct drive configuration. The simulated system consists of the electrical system and a hydrodynamicvortex model for the turbine. Experiments of no load operation were conducted to calibratethe drag losses of the turbine. Simulations were able to predict the behaviour of a stepresponse for a change in Tip Speed Ratio (TSR) when the turbine was operated close to optimal TSR. The turbine start position could be changed to view the influence of changed relative position of the turbine to the water flow in the step response.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-267944 (URN)10.3390/en11113067 (DOI)
Funder
StandUpÅForsk (Ångpanneföreningen's Foundation for Research and Development)Vattenfall ABSwedish Research CouncilSwedish Energy AgencyVattenfall AB
Note

Funders: J Gust Richert, Bixia Miljöfond

Available from: 2015-12-10 Created: 2015-11-30 Last updated: 2018-11-07Bibliographically approved
7. Impact of Blade Pitch Angle on Turbine Performance of a Vertical Axis Current Turbine
Open this publication in new window or tab >>Impact of Blade Pitch Angle on Turbine Performance of a Vertical Axis Current Turbine
(English)Manuscript (preprint) (Other academic)
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-364264 (URN)
Available from: 2018-10-25 Created: 2018-10-25 Last updated: 2018-11-01
8. Marine Current Energy Converters to Power a Reverse Osmosis Desalination Plant
Open this publication in new window or tab >>Marine Current Energy Converters to Power a Reverse Osmosis Desalination Plant
2018 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, article id 2880Article in journal (Refereed) Published
Abstract [en]

Some countries are facing issues on freshwater and electricity production, which can be addressed with the use of renewable energy powered desalination systems. In the following study, a reverse osmosis desalination plant powered by marine current energy converters is suggested. The marine current energy converters are designed at Uppsala University in Sweden, specifically for utilizing low water speeds (1–2 m/s). Estimations on freshwater production for such a system, in South Africa, facing the Indian Ocean was presented and discussed. It is concluded that the desalination plant cannot by itself supply freshwater for a population all the time, due to periods of too low water speeds (<1 m/s), but for 75% of the time. By using ten marine current energy converters, each with a nominal power rating of 7.5 kW, combined with a reverse osmosis desalination plant and water storage capacity of 2800 m3, it is possible to cover the basic freshwater demand of 5000 people. More studies on the hydrokinetic resource of the Western Indian Ocean, system cost, technology development, environmental and social aspects are necessary for more accurate results.

Keywords
marine current- tidal energy converters, hydro-kinetic energy, desalination, freshwater production, renewable energy, western Indian Ocean
National Category
Environmental Engineering Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-362542 (URN)10.3390/en11112880 (DOI)
Available from: 2018-10-05 Created: 2018-10-05 Last updated: 2018-12-12Bibliographically approved

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