S Salter-Oxford Tidal Energy Workshop, March 2012
There were many possible options for onshore wind turbines but the three-bladed axialflow horizontal-axis design with a mono-tube tower is now universal. It is therefore not surprising that nearly all of the proposals for tidal-stream turbines use horizontal-axis axial-flow. The widely separated rotors are the equivalent of leaky pipes in a hydro-electric scheme. This paper attempts to show that, despite its widespread popularity, the transfer from wind technology is wrong and that a cross-flow design  with rotation about a vertical axis  is better.