This paper starts with a brief account of the pioneering SeaGen tidal turbine and the R&D
programme that was necessary to develop it. The main thrust of the paper is to review the
technical choices that needed to be taken and to indicate reasons for developing the
technology in its chosen form. In order to present the logic behind the SeaGen design the
author discusses some of the fundamentals of water kinetic energy conversion and the
consequent choice of rotor types. The paper also reviews key structural, operational and
economic issues and finally presents some key conclusions, notably that many of the lessons
learnt earlier in wind turbine development also apply to tidal turbine development.