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The Söderfors Project: Experimental Hydrokinetic Power Station Deployment and First Results
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Marine Current Power)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Marine Current Power)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Marine Current Power)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.ORCID iD: 0000-0001-8229-4839
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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.

Place, publisher, year, edition, pages
2013.
Keyword [en]
Marine Current Power, Renewable energy, Söderfors
Keyword [sv]
Strömkraft, Förnybar energi, Söderfors
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
URN: urn:nbn:se:uu:diva-209220OAI: oai:DiVA.org:uu-209220DiVA: diva2:656291
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: 2017-04-04Bibliographically approved
In thesis
1. Marine Current Resource Assessment: Measurements and Characterization
Open this publication in new window or tab >>Marine Current Resource Assessment: Measurements and Characterization
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Abstract [sv]

Det ökande intresset för att producera elektricitet från förnybara energikällor har lett till en satsning på forskning inom området marin strömkraft, främst när det gäller tidvattenströmmar och tidvattenturbiner för fritt strömmande vatten. Tidvatten har fördelen att vara förutsägbar årtionden i förväg. Dock så är tidvattenresursen periodisk och varierar lokalt vilket påverkar effektuttaget från ett kraftverk. Variationerna beror till största delen på fyra aspekter: antal hög- och lågvatten per dag, tidvattencykeln, djupförhållanden på platsen (batymetri) och vädereffekter. Varje potentiell plats är unik, vattnets hastighetsfält påverkas i hög grad av lokal batymetri och turbulens. Därför krävs noggranna undersökningar för att karakterisera resursen. Att tillhandahålla hastighetsdata av hög kvalitet från mätningar är därför av stor betydelse. I denna avhandling har mätningar av flödeshastigheter utförts på tre typer av platser.

En plats med tidvattenströmmar, belägen i en av alla fjordar längs Norges kust, har undersökts för sin resurspotential. Mätningar har utförts för att kartlägga resursens variation i både tid och rum. Resultaten visar att strömmar i storleksordningen 2 m/s återfinns i mitten av kanalen. Dessutom uppvisar flödet liten variation från huvudriktningen för både inkommande (flod) och utgående (ebb) flöden. Platsen har således potential för energiomvandling av fritt strömmande vatten. En modell föreslås som förutsäger strömmarnas maxhastighet från information om höjdskillnaden mellan ebb och flod och vice versa. En motsvarande modell kan ställas upp och användas på andra platser med liknande förhållanden som berörs av tidvatten, dvs. fjordinlopp som förbinder havet med en fjord eller en bassäng.

En älv fungerar som en plats för experiment för ett marint strömkraftverk som har utvecklats vid Uppsala universitet och sjösatts i Dalälven, Söderfors. Flödeshastigheten på platsen regleras uppströms av ett närliggande vattenkraftverk, vilket gör platsen bra för att utföra experiment på prestandan av den vertikalaxlade turbinen i dess naturliga miljö. Turbinen har körts i jämnt flöde och mätningar har utförts för att karaktärisera vakens utbredning.

En plats med havsströmmar var mål för en utredning av dess potential för att ge användbar förnybar energi. En mätningskampanj genomfördes för att kartlägga flödets variation både rumsligt och tidsmässigt. Emellertid visade sig platsen inte vara lämplig för energiomvandling utifrån användning av nuvarande teknik.

Place, publisher, year, edition, pages
Uppsala: Institutionen för teknikvetenskaper, 2015. 39 p.
Series
UURIE / Uppsala University, Department of Engineering Sciences, ISSN 0349-8352 ; 342-15L
Keyword
ADCP
National Category
Oceanography, Hydrology, Water Resources Ocean and River Engineering Marine Engineering Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-266670 (URN)
Presentation
2015-12-15, Polhemsalen, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Funder
Swedish Research CouncilCarl Tryggers foundation ÅForsk (Ångpanneföreningen's Foundation for Research and Development)Swedish Energy AgencyVattenfall AB
Available from: 2015-12-02 Created: 2015-11-10 Last updated: 2015-12-10Bibliographically 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. 53 p.
Series
UURIE / Uppsala University, Department of Engineering Sciences, ISSN 0349-8352 ; 345-15L
Keyword
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: 2015-12-10Bibliographically approved
3. Marine Current Energy Conversion
Open this publication in new window or tab >>Marine Current Energy Conversion
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Marine currents, i.e. water currents in oceans and rivers, constitute a large renewable energy resource. This thesis presents research done on the subject of marine current energy conversion in a broad sense.

A review of the tidal energy resource in Norway is presented, with the conclusion that tidal currents ought to be an interesting option for Norway in terms of renewable energy.

The design of marine current energy conversion devices is studied. It is argued that turbine and generator cannot be seen as separate entities but must be designed and optimised as a unit for a given conversion site. The influence of support structure for the turbine blades on the efficiency of the turbine is studied, leading to the conclusion that it may be better to optimise a turbine for a lower flow speed than the maximum speed at the site.

The construction and development of a marine current energy experimental station in the River Dalälven at Söderfors is reported. Measurements of the turbine's power coefficient indicate that it is possible to build efficient turbines for low flow speeds. Experiments at the site are used for investigations into different load control methods and for validation of a numerical model of the energy conversion system and the model's ability to predict system behaviour in response to step changes in operational tip speed ratio.

A method for wake measurements is evaluated and found to be useful within certain limits. Simple models for turbine runaway behaviour are derived, of which one is shown by comparison with experimental results to predict the behaviour well.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 66 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1353
Keyword
marine current energy, renewable energy, turbine, energy conversion, wake, Söderfors
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-280763 (URN)978-91-554-9510-7 (ISBN)
Public defence
2016-05-04, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2016-04-08 Created: 2016-03-15 Last updated: 2016-04-12
4. Grid Connection of Permanent Magnet Generator Based Renewable Energy Systems
Open this publication in new window or tab >>Grid Connection of Permanent Magnet Generator Based Renewable Energy Systems
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Renewable energy is harnessed from continuously replenishing natural processes. Some commonly known are sunlight, water, wind, tides, geothermal heat and various forms of biomass. The focus on renewable energy has over the past few decades intensified greatly. This thesis contributes to the research on developing renewable energy technologies, within the wind power, wave power and marine current power projects at the division of Electricity, Uppsala University. In this thesis grid connection of permanent magnet generator based renewable energy sources is evaluated.

A tap transformer based grid connection system has been constructed and experimentally evaluated for a vertical axis wind turbine. Full range variable speed operation of the turbine is enabled by using the different step-up ratios of a tap transformer. This removes the need for a DC/DC step or an active rectifier on the generator side of the full frequency converter and thereby reduces system complexity. Experiments and simulations of the system for variable speed operation are done and efficiency and harmonic content are evaluated. 

The work presented in the thesis has also contributed to the design, construction and evaluation of a full-scale offshore marine substation for wave power intended to grid connect a farm of wave energy converters. The function of the marine substation has been experimentally tested and the substation is ready for deployment. Results from the system verification are presented. Special focus is on the transformer losses and transformer in-rush currents.

A control and grid connection system for a vertical axis marine current energy converter has been designed and constructed. The grid connection is done with a back-to-back 2L-3L system with a three level cascaded H-bridge converter grid side. The system has been tested in the laboratory and is ready to be installed at the experimental site. Results from the laboratory testing of the system are presented.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 79 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1436
Keyword
VAWT, H-rotor, Tap Transformer, Cascaded H-bridge Multi-Level, Renewable Energy, Wind power, Wave power, Marine Current Power
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-304659 (URN)978-91-554-9712-5 (ISBN)
Public defence
2016-11-25, Polhemsalen, 10134, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Projects
Wind PowerWave PowerMarine Currnet Power
Available from: 2016-11-03 Created: 2016-10-06 Last updated: 2016-11-16Bibliographically approved
5. Resource characterization and variability studies for marine current power
Open this publication in new window or tab >>Resource characterization and variability studies for marine current power
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Producing electricity from marine renewable resources is a research area that develops continuously. The field of tidal energy is on the edge to progress from the prototype stage to the commercial stage. However, tidal resource characterization, and the effect of tidal turbines on the flow, is still an ongoing research area in which this thesis aims to contribute.

In this thesis, measurements of flow velocities have been performed at three kinds of sites. Firstly, a tidal site has been investigated for its resource potential in a fjord in Norway. Measurements have been performed with an acoustic Doppler current profiler to map the spatial and temporal characteristics of the flow. Results show that currents are in the order of 2 m/s in the center of the channel. Furthermore, the flow is highly bi-directional between ebb and flood flows. The site thus has potential for in-stream energy conversion. Secondly, 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 hydro power plant, making the site suitable for experiments on the performance of the vertical axis turbine in a natural environment. The turbine was run in steady discharge flows and measurements were performed to characterize the extent of the wake. Lastly, at an ocean current site, the effect that transiting ferries may have on submerged devices was investigated. Measurements were conducted with two sonar systems to obtain an underwater view of the wake caused by a propeller and a water jet thruster respectively.

Furthermore, the variability of the intermittent renewable sources wind, solar, wave and tidal energy was investigated for the Nordic countries. All of the sources have distinctly different variability features, which is advantageous when combining power generated from them and introducing it on the electricity grid. Tidal variability is mainly due to four aspects: the tidal regime, the tidal cycle, local bathymetry causing turbulence, asymmetries etc. and weather effects. Models of power output from the four sources was set up and combined in different energy mixes for a “highly renewable” and a “fully renewable” scenario. By separating the resulting power time series into different frequency bands (long-, mid-, mid/short-, and short-term components) it was possible to minimize the variability on different time scales. It was concluded that a wise combination of intermittent renewable sources may lower the variability on short and long time scales, but increase the variability on mid and mid/short time scales.

The tidal power variability in Norway was then investigated separately. The predictability of tidal currents has great advantages when planning electricity availability from tidal farms. However, the continuously varying tide from maximum power output to minimum output several times per day increases the demand for backup power or storage. The phase shift between tidal sites introduces a smoothing effect on hourly basis but the tidal cycle, with spring and neap tide simultaneously in large areas, will inevitably affect the power availability.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 64 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1499
Keyword
Marine current energy, tidal currents, wake, variability, renewable energy, ADCP, flow measurement
National Category
Ocean and River Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-319033 (URN)978-91-554-9881-8 (ISBN)
Public defence
2017-05-31, Häggsalen, Ångströmlaboratoriet, Uppsala, 09:15 (English)
Opponent
Supervisors
Funder
StandUpSwedish Energy AgencyÅForsk (Ångpanneföreningen's Foundation for Research and Development)Carl Tryggers foundation
Available from: 2017-05-05 Created: 2017-04-04 Last updated: 2017-05-08

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