ELEKTRICITETSLÄRA

Current Research Projects

Electric power generation from marine currents

  • Project leader: Professor Mats Leijon, Uppsala University
  • Researcher: Karin Thomas, Anders Goude, Mårten Grabbe, Irina Dolguntseva
  • Phd. students: Nicole Carpman, Johan Forslund, Staffan Lundin,
    Minh Thao Nguyen

A research project at Uppsala University is investigating electricity generation from the vast renewable energy source presented by tidal currents and ocean currents. The research is focused on energy conversion with a vertical axis turbine and a direct drive generator. This choice of technology is intended to provide a simple and robust system with low maintenance needs and minimal environmental impact.

Vertical axis turbine
Figure 1: The vertical axis turbine and direct drive generator placed on the sea bed.

The oceans, covering more than 70 % of the earth, have long been appreciated as a vast renewable energy source. As of today, this energy source is almost not used at all. The energy is stored in the oceans partly as thermal energy and partly as kinetic energy as waves and currents. The kinetic energy can be extracted in a way similar to the wind power technique. Compared to wind speeds, marine currents are very slow, but the density of water is about 800 times higher than that of air. This means that the energy content of a marine current of only 1 m/s is equivalent to a wind speed of 9 m/s. With a suitable technology for harnessing the kinetic energy in European waters, marine and tidal currents might yield 39-58 TWh of clean and sustainable electric energy per year as found in several studies.

The ocean current resources still remain predominantly untapped. However, the physics behind ocean currents is very promising for energy conversion. Looking at the source of the energy, marine and tidal currents offer a high degree of utilization with no emissions during operation. This yields good economical conditions for the energy conversion. Furthermore, there are no indirect emissions from fuel transports, little or no visual impact and presumed low impact on the fish ecology.

The ocean current resources still remain predominantly untapped. However, the physics behind ocean currents is very promising for energy conversion. Looking at the source of the energy, marine and tidal currents offer a high degree of utilization with no emissions during operation. This yields good economical conditions for the energy conversion. Furthermore, there are no indirect emissions from fuel transports, little or no visual impact and presumed low impact on the benthic ecology.

Extensive simulations using a 2D FEM tool have been carried out to create a generator suited to the slow moving marine currents. For a first prototype generator, a 5 kW cable wound generator with a 120 pole rotor was designed for a nominal speed of 10 rpm. Construction of the generator was completed in March 2007. The high efficiency at part load and at overload is an essential feature of the generator to be able to absorb energy even when the current velocity is low.

Magnetic flux Simulated Eff.
Figure 2: To the left, a section of the generator showing the magnetic flux density (T) in the stator tooth and the rotor ring. To the right, the simulated efficiency of the generator for variable load and speed.

The generator has been used in both research and education. The prototype generator and experimental setup verifies the previous simulations made. The experience gained in building the prototype has been useful in the construction of a generator aimed for the Söderfors project.

In a first phase, the generator will be tested in the laboratory without a turbine. Instead, it will be powered by an induction motor and connected to a resistive load. The prototype generator and experimental setup enable verification of previous simulations. The experience gained in building this prototype will also be useful in the future construction of a generator and a turbine for testing in a marine environment.

Computer model Stator
Figure 3: To the left, a computer model of the complete experimental setup and to the right the cable wound stator of the actual setup during construction.

The Söderfors Project

The aim of the Söderfors Project is to build a minor experimental station for marine current energy conversion in a realistic environment. Several sites for the station was considered before the final site at Dalälven River was decided. The site is downriver of the conventional hydro power plant in Söderfors in the municipality of Tierp. Permissions have been received from local land owners, the power plant owner, fishing rights owners and concerned authorities to build the research station.

Söderfors
Figure 4: Overview of Söderfors where the current power plant and the measuring cabin are marked. (Lantmäteriet Gävle 2009, permission I 2008/1962)

The research station includes the turbine, the generator and foundation on the river floor. A cable will connect the turbine and generator with a cabin on shore housing the measurement instruments. The installation procedure will begin during the summer of 2012. The turbine and generator will be lowered into the water using a crane. Divers will check the equipment during installation, which require the hydro power plant upstream to be shut down. The turbine’s position will be distinct marked on the water surface.

For more information regarding the Söderfors Project,
contact Mats Leijon: 018 - 471 58 08.

List of publications

Anders Goude, Olov Ågren, "Simulations of a vertical axis turbine in a channel", Renewable Energy, Volume 63, March 2014, Pages 477-485, doi:10.1016/j.renene.2013.09.038

Mårten Grabbe, Katarina Yuen, Senad Apelfröjd, and Mats Leijon, "Efficiency of a Directly Driven Generator for Hydrokinetic Energy Conversion", Advances in Mechanical Engineering, vol. 2013, Article ID 978140, 8 pages, 2013. doi:10.1155/2013/978140

Staffan Lundin, Johan Forslund, Nicole Carpman, Mårten Grabbe, Katarina Yuen, Senad Apelfröjd, Anders Goude and Mats Leijon, "The Söderfors Project: Experimental Hydrokinetic Power Station Deployment and First Results", Proceedings of the 10th European Wave and Tidal Conference (EWTEC), Aalborg, Denmark, 2-5 September 2013, Open Access

Emilia Lalander, "Hydrokinetic Resource Assessment : Measurements and Models", Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214; 1038, Abstract + Fulltext

Katarina Yuen, Senad Apelfröjd, and Mats Leijon, "Implementation of Control System for Hydrokinetic Energy Converter", Journal of Control Science and Engineering, vol. 2013, Article ID 342949, 10 pages, doi:10.1155/2013/342949

Mårten Grabbe, "Hydro-kinetic energy conversion: resource and technology", Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214; 1025, Abstract + Fulltext

Emilia Lalander, Paul Thomassen, Mats Leijon, "Evaluation of a Model for Predicting the Tidal Velocity in Fjord Entrances", Energies 6, no. 4: 2031-2051, 2013, doi:10.3390/en6042031

Emilia Lalander, Mårten Grabbe, and Mats Leijon, "On the velocity distribution for hydro-kinetic energy conversion from tidal currents and rivers",
Journal of Renewable and Sustainable Energy, vol. 5, issue 2, (2013);
doi:10.1063/1.4795398, open access

Katarina Yuen, "System perspectives on hydro-kinetic energy conversion",Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214; 976, Abstract + Fulltext

Eduard Dyachuk, Anders Goude, Emilia Lalander, Hans Bernhoff, "Influence of Incoming Flow Direction on Spacing between Vertical Axis Marine Current Turbines Placed in a Row", Proceedings of the 31st International Conference on Ocean, Offshore and Arctic Engineering, Rio de Janeiro, Brazil, July 1-6, 2012

Karin Thomas, Mårten Grabbe, Katarina Yuen, and Mats Leijon, "A Permanent Magnet Generator for Energy Conversion from Marine Currents: No Load and Load Experiments", ISRN Renewable Energy, vol. 2012, Article ID 489379, 7 pages, 2012. doi:10.5402/2012/489379, Open access

Katarina Yuen, Staffan Lundin, Mårten Grabbe, Emilia Lalander, Anders Goude, Mats Leijon. "The Söderfors Project: Construction of an Experimental Hydrokinetic Power Station". In Proceedings of the 9th European Wave and Tidal Energy Conference, Southampton, UK, 5-9 September 2011, Open access

Emilia Lalander, Mats Leijon, "In-stream energy converters in a river - effects on upstream hydropower station", Renewable Energy Volume 36, Issue 1, January 2011, Pages 399-404, doi:10.1016/j.renene.2010.05.019

A. Goude, O. Ågren, "Numerical Simulation of a Farm of Vertical Axis Marine Current Turbines", Proceedings of the ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2010), June 6-11, 2010, Shanghai, China, OMAE2010-20160.

Emilia Lalander, ”Modelling the hydrokinetic energy resource for in-stream energy converters”, UURIE 316-10L, Uppsala 2010 PDF, Errata

Grabbe, M., Yuen, K., Goude, A., Lalander, E. & Leijon, M., "Design of experimental setup for hydro-kinetic energy conversion.", Hydropower and dams, 2009 (5), pp. 112–116. Open access

Grabbe, M.; Lalander, E.; Lundin, S.; Leijon, M. "A review of the tidal current energy resource in Norway", Renewable & Sustainable Energy Reviews, Vol. 13, 2009, pp. 1898–1909, doi:10.1016/j.rser.2009.01.026, Open access

Goude, A., Lundin, S. & Leijon, "A parameter study of the influence of struts on the performance of a vertical-axis marine current turbine." In Proceedings of the 8th European wave and tidal energy conference, EWTEC09,
Uppsala, Sweden, pp. 477–483.

Lalander, E. & Leijon, M. "Numerical modeling of a river site for in-stream energy converters." In Proceedings of the 8th European wave and tidal energy conference, EWTEC09, Uppsala, Sweden, pp. 826–832.

S. Lundin, M. Grabbe, K. Yuen and M. Leijon, "A Design Study of Marine Current Turbine-Generator Combinations", Proceedings of the 28th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2009), May 31 to June 5, 2009, Honolulu, Hawaii.

A. Goude, E. Lalander and M. Leijon, "Influence of a Varying Vertical Velocity Profile on Turbine Efficiency for a Vertical Axis Marine Current Turbine", Proceedings of the 28th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2009), May 31 to June 5, 2009, Honolulu, Hawaii.

K. Yuen, K. Thomas, M. Grabbe, P. Deglaire, M. Bouquerel, D. Österberg & M. Leijon. "Matching a Permanent Magnet Synchronous Generator to a Fixed Pitch Vertical Axis Turbine for Marine Current Energy Conversion", IEEE Journal of Oceanic Engineering, vol.34, no.1, pp.24-31, Jan. 2009, DOI:10.1109/JOE.2008.2010658

Mårten Grabbe, "Marine Current Energy Conversion-Resource and Technology",
UURIE 309-09L, Uppsala 2009 PDF

Katarina Yuen, "System Aspects of Marine Current Energy Conversion", UURIE 307-08L, Uppsala 2008, PDF (815kB)

K Thomas, M Grabbe, K Yuen, M Leijon, "A low-speed generator for energy conversion from marine currents – experimental validation of simulations", Journal of Power and Energy (Part A of the Proceedings of the Institution of Mechanical Engineers), Volume 222, Number 4 / 2008, Pages 381-388,
doi:10.1243/09576509JPE567, Open access

K. Thomas, "Low Speed Energy Conversion from Marine Currents", Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 287, ISBN 978-91-554-7063-0 Abstract

M. Leijon and K. Nilsson, "Direct electric energy conversion system for energy conversion from marine currents", Proc. IMechE Part A: Journal of Power and Energy, Volume 221, Number 2, 2007, Full Text

K. Nilsson, M. Grabbe, K. Yuen and M. Leijon, "A direct drive generator for marine current energy conversion - first experimental results", Proceedings of the 7th European Wave and Tidal Energy Conference, 11-13 September 2007, Porto, Portugal.

K. Yuen, K. Nilsson, M. Grabbe and M. Leijon, "Experimental Setup: Low Speed Permanent Magnet Generator for Marine Current Power Conversion", Proceedings of the 26th International Conference on Offshore Mechanics and Arctic Engineering OMAE 2007, June 10-15, 2007, San Diego, California, USA.

E. Segergren and M. Leijon,"Relation between generator geometry and resistance in armature winding", Applied Energy, Volume 83, Issue 8, August 2006, pp. 884-892.

E. Segergren, "Direct Drive Generator for Renewable Power Conversion from Water Currents", Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 100, ISBN 91-554-6362-2.

E. Segergren, K. Nilsson, M. Leijon, "Frequency Optimization for Direct Drive Synchronous Current Power Generator", IEEE Journal of Oceanic Engineering Volume 30, Issue 3, July 2005, pp. 647-648.

E. Segergren, K. Nilsson, M. Leijon, "Permanent magnetized generator for marine current power conversion - proposed experimental setup", Presented at OMAE2005, Halkidiki, Greece, 12-17 June 2005.

E. Segergren, K. Nilsson, J. Sundberg, M. Leijon, "The Marine Current Power Project at the Swedish Centre for Renewable Electric Energy Conversion ", Presented at the 6th EWTEC conference in Glasgow, 28th of August to 3rd of September 2005.

K. Nilsson, E. Segergren, E. Sjöstedt, J. Sundberg, M. Leijon, "Converting Kinetic Energy in Small Watercourses using Direct Drive Generators" , Proceedings of OMAE 2004: 23rd International Conference on Offshore Mechanics and Arctic Engineering, 20-25 June 2004 Vancouver, Canada.

E. Segergren, K. Nilsson, D. P. Coiro, M. Leijon, "Design of a Very
Low Speed PM Generator for the Patented KOBOLD Tidal Current Turbine"
,
Proceedings from EnergyOcean2004, 28 - 29 June 2004, Palm Beach, Florida