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Advances in Mechanical Engineering
Volume 2013 (2013), Article ID 978140, 8 pages
Research Article

Efficiency of a Directly Driven Generator for Hydrokinetic Energy Conversion

Division of Electricity, The Ångström Laboratory, The Swedish Centre for Renewable Electric Energy Conversion, Uppsala University, P.O. Box 534, 751 21 Uppsala, Sweden

Received 23 May 2013; Revised 6 September 2013; Accepted 6 September 2013

Academic Editor: Fabrizio Marignetti

Copyright © 2013 Mårten Grabbe et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


An experimental setup for hydrokinetic energy conversion comprising a vertical axis turbine, a directly driven permanent magnet generator, and a control system has been designed and constructed for deployment in the river Dalälven in Sweden. This paper is devoted to discussing the mechanical and electrical design of the generator used in the experimental setup. The generator housing is designed to be water tight, and it also acts as a support structure for the turbine shaft. The generator efficiency has been measured in the range of 5–16.7 rpm, showing that operation in the low velocity range up to 1.5 m/s is possible with a directly driven generator.