Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 957 Experimental results from the Lysekil Wave Power Research Site OLLE SVENSSON ACTA UNIVERSITATIS UPSALIENSIS ISSN 1651-6214 ISBN 978-91-554-8433-0 UPPSALA urn:nbn:se:uu:diva-179098 2012 Dissertation presented at Uppsala University to be publicly examined in Polhem Å 10134, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, Friday, September 28, 2012 at 13:00 for the degree of Doctor of Philosophy. The examination will be conducted in English. Abstract Svensson, O. 2012. Experimental results from the Lysekil Wave Power Research Site. Acta Universitatis Upsaliensis. Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 957. 101 pp. Uppsala. ISBN 978-91-554-8433-0. This thesis presents how experimental results, from wave power research performed offshore at the Lysekil research site, were obtained. The data were used to verify theoretical models as well as evaluate the feasibility of wave power as a future sustainable energy source. The first experiments carried out at the research site was the measurement of the force in a line where one end was connected to a buoy with a diameter of 3 m and the other end to a set of springs with limited stroke length. The system is exposed to high peak forces compared to average forces. The maximum measured force in the line, when the buoy motion is limited by a stiff stopper rope is ten times the average force in that particular sea state. The experiment performed on the first wave energy converter tested at the Lysekil Research Site is described. The infrastructure of the site is presented where the central connection point is the measuring station. The key finding is that it is possible to transform the motions of ocean waves into electrical energy and distribute it to land. Many wave energy converters must be interconnected if large amounts of energy are to be harvested from the waves. The first submerged substation intended for aggregation of energy from wave power converters is described, with focus on the measurement and control system placed inside the substation. During this experiment period the generators were equipped with many different sensors; these measurements are explained in the thesis. The system that aggregates power from the studied wave energy converter is regularly exposed to peak power of up to 20 times the maximum average output from the converter. Vertical and horizontal movement of the buoy has been measured in different ways. The result is that the vertical displacement of the buoy can be measured with a simple accelerometer circuit but it is much more complicated to measure the horizontal displacement. A special method for measuring the horizontal displacement has been implemented by measuring the strain in the enclosure and the force in the line. Keywords: Wave power, Lysekil, Marine Substation, Offshore measurement, strain gauge, lateral force, Invlination and azimuth angles, Wave energy converter, Temperature measurements, Inverter, Energy, Control sustem, CompactRIO, Vågkraft, Mätteknik, Styrsystem, Lysekil Olle Svensson, Uppsala University, Department of Engineering Sciences, Electricity, Box 534, SE-751 21 Uppsala, Sweden. © Olle Svensson 2012 ISSN 1651-6214 ISBN 978-91-554-8433-0 urn:nbn:se:uu:diva-179098 (http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-179098) To my late father who started the journey ”from cultivation to education” List of Papers This thesis is based on the following papers, which are referred to in the text by their Roman numerals. Paper published 2005 I Gustafsson, S., Svensson, O., Sundberg, J., Bernhoff, H., Leijon, M., Danielsson, O., Ericsson, M., Thorburn, K., Strand, K., Henfridsson, U., Ericsson, E., Bergman, K., “Experiments at Islandsberg on the west coast of Sweden in preparation of the construction of a pilot wave power plant” Proceedings of the 6th EWTEC conference, Glasgow, UK, 2005. Papers published 2007 II Waters, R., Stålberg, M., Danielsson, O., Svensson, O., Gustafsson, S., Strömstedt, E., Eriksson, M., Sundberg, J., and Leijon, M. “Experimen- tal results from sea trials of an offshore wave energy system”. Applied Physics Letters, 90:034105, 2007. doi: http://dx.doi.org/10.1063/1.2432168 III Eriksson, M., Waters, R., Svensson, O., Isberg, J., and Leijon, M. “Wave power absorption: Experiments in open sea and simulation”. Journal of Applied Physics, 102:084910, 2007. doi: http://dx.doi.org/10.1063/1.2801002 Papers published 2008 IV Leijon, M., Boström, C., Danielsson, O., Gustafsson, S., Haikonen, K., Langhamer, O., Strömstedt, E., Stålberg, M., Sundberg, J., Svensson, O., Tyrberg, S., and Waters, R. “Wave Energy from the North Sea: Experiences from the Lysekil Research Site”. Surveys in Geophys- ics, Springer, 2008. Doi: 10.1007/s10712-008-9047-x Papers published 2009 V Leijon, M., Waters, R., Rahm, M., Svensson, O., Boström, C., Strömstedt, E., Engström, J., Tyrberg, S., Savin, A., Gravrakmo, H., Bernhoff, H., Sundberg, J., Isberg, J., Agree, O., Danielsson, O., Eriks- son, M., Lejerskog, E., Bolund, B., Gustafsson, S., Thorburn, K.,, “Catch the wave to electricity”, IEEE Power and Energy Magazine, Volume 7, Issue 1, January-February 2009 Page(s):50 - 54, doi: 10.1109/MPE.2008.930658 VI Svensson, O., Boström, C., Rahm, M., & Leijon, M., “Description of the control and measurement system used in the Low Voltage Marine Sub- station at the Lysekil research site.” Proceedings of the 8th European wave and tidal energy conference, EWTEC09, Uppsala, Sweden, pp. 44– 50. VII Boström, C., Waters, R., Lejerskog, E., Svensson, O., Stålberg, M., Strömstedt, E., Leijon, M. “Study of a Wave Energy Converter Con- nected to a Nonlinear Load” IEEE Journal of Oceanic Engineering, Vol- ume. 34, issue 2, pp. 123-127, 2009., DOI: 10.1109/JOE.2009.2015021 VIII Rahm, M., Boström, C., Svensson, O., Grabbe, M., Bülow, F. and Lei- jon, M. “Laboratory experimental verification of a marine substation” Proceedings of the 8th European wave and tidal energy conference, EWTEC09, Uppsala, Sweden, pp. 51–58. IX Boström C., Svensson O., Rahm M., Lejerskog E., Savin A., Strömstedt E., Engström J., Gravråkmo H., Haikonen K., Waters R., Björklöf D., Johansson T., Sundberg J. and Leijon M., “Design proposal of electrical system for linear generator wave power plants”, Proc. of IECON 2009, 35th annual conference of the IEEE Industrial Electronics and Society, Porto, Portugal 3-5 November 2009, no. PD-027448, pp. 4429-4434. doi: 10.1109/IECON.2009.5414903 X Savin A., Svensson O., Strömstedt E., Boström C. and Leijon M., “De- termining the service life of a steel wire under a working load in the Wave Energy Converter (WEC) ”, Proceedings of the 28th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2009), May 31 to June 5, 2009, Honolulu, Hawaii. doi: http://dx.doi.org/10.1115/OMAE2009-79164 Papers published 2010 XI Rahm M., Boström C., Svensson O., Grabbe M., Bülow F. and Leijon M., “Offshore underwater substation for wave energy converter arrays”, Renewable Power Generation, IET, Volume.4, no.6, pp.602-612, No- vember 2010 doi: 10.1049/iet-rpg.2009.0180 XII Boström, C., Lejerskog, E., Tyrberg, S., Svensson, O., Waters, R., Savin, A., Bolund, B., Eriksson, M., Leijon, M., “Experimental results from an offshore wave energy converter”, Journal of Offshore Mechan- ics and Arctic Engineering, Volume. 132, Issue 4, 041103, 5 pages, 2010. doi:10.1115/1.4001443 XIII Gravråkmo, H., Leijon, M., Strömstedt, E., Engström, J., Tyrberg, S., Savin, A., Svensson, O., Waters, R., “Description of a Torus-shaped Buoy for Wave Energy Point Absorber”, Renewable energy 2010, 27June-2July, 2010, pacifico Yokohama, Yokohama, Japan. Papers published 2011 XIV Tyrberg, S., Svensson, O., Kurupath, V., Engström, J., Strömstedt, E., and Leijon, M. “Wave Buoy and Translator Motions — On-site Meas- urements and Simulations”. IEEE Journal of Oceanic Engineering, Vol- ume. 36, Issue 3, pp. 377–385, July 2011. doi:10.1109/JOE.2011.2136970 XV Waters, R., Rahm, M., Eriksson, M., Svensson, O., Strömstedt, E., Boström, C., Sundberg, J., Leijon, M. “Ocean wave energy absorption in response to wave period and amplitude - offshore experiments on a wave energy converter”, Renewable Power Generation, IET Volume: 5, Issue: 6 pp. 465-469, November 2011. doi: 10.1049/iet-rpg.2010.0124 , XVI Lejerskog, E., Gravråkmo, H., Savin, A., Strömstedt, E., Tyrberg, S., Haikonen, K., Krishna R., Boström, C., Rahm, M., Ekström, R., Svensson, O., Engström, J., Ekergård, B., Baudoin, A., Kurupath, V., Hai, L., Li, W., Sundberg, J., Waters R., and M. Leijon. “Lysekil Re- search Site, Sweden: A Status Update” Proceedings of the Ninth Euro- pean Wave and Tidal Energy. Southampton .UK 2011. XVII Svensson, O., Strömstedt, E., Savin, A. Leijon, M. “Sensors and Meas- urements Inside the second and Third Wave Energy Converter at the Lysekil Research Site” Proceedings of the Ninth European Wave and Tidal Energy. Southampton .UK 2011. Papers published 2012 XVIII Boström, C., Rahm, M., Svensson, O., Strömstedt, E., Savin, A., Wa- ters, R., and Leijon, M., “Temperature Measurements in a Linear Gen- erator and Marine Substation for Wave Power”, Journal of Offshore Me- chanics and Arctic Engineering, Volume 134, Issue 2, 21901, 6 pages, May 2012. doi:10.1115/1.4004629 XIX Strömstedt, E., Svensson, O., Leijon, M. “A Set-Up of 7 Laser Triangu- lation Sensors and a Draw-Wire Sensor for Measuring Relative Dis- placement of a Piston Rod Mechanical Lead-Through Transmission in an Offshore Wave Energy Converter on the Ocean Floor ” ISRN Renew- able Energy, Volume. 2012, Article ID 746865, 32 pages, 2012. doi:10.5402/2012/746865 XX Savin, A., Svensson, O and Leijon, M. “Estimation of Stress in the Inner Framework Structure of a Single Heaving Buoy Wave Energy Con- verter”, IEEE journal of Oceanic Engineering, Volume 37 number 2 p.p.