This paper has reported the interim outcomes from the performance appraisal of a novel contra-rotating tidal current rotor. The work was undertaken to quantify the performance benefits that might be achieved relative to conventional, singular rotor technology. The findings have demonstrated that centre dot A marginal improvement in rotor performance can be expected due to the capture of the energy normally dissipated in the downstream swirl, centre dot The reduction in the downstream swirl will minimise seabed scouring, centre dot A reduction of reactive torque should be possible, enabling a mooring-based supporting system to be employed as opposed to the expensive structural support systems employed with conventional rotor systems, centre dot The increase in relative shaft speed reduces the sub-sea mass to be supported and the complexity associated with a high step-up ratio gearbox and centre dot The introduction of variable pitch control on the upstream rotor will optimise the angle of attack for all stages of the tidal stream while ensuring proper interaction with the downstream rotor. The next stage of the work programme involves additional mathematical modelling of the two-rotor turbine configuration. The expectation is that this will lead to the construction of a prototype for use in empirical research using tow tank testing. The data from such tests will be used to verify the parameter values assumed within the modelling stage. In this way, modelling and laboratory testing will then be used together to identify approaches to the minimisation of the reactive torque over the full operating envelope of the turbine and the development of a new generator system based on direct coupling of the turbine.
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