Advanced Turbine Concepts

Duct velocity fieldThe focus of this research study is on understanding the behaviour of the fluid flow through some of the novel advanced turbine concepts being currently proposed. It should be noted that for all but horizontal axis turbines, i.e. those that resemble conventional wind turbines, no complete theoretical description of the fluid flow through the turbine exists. Hence, little is known of how to model flows through and therefore optimise power take off from some of the more exotic turbine designs being proposed.

Examples of such advanced turbine concepts are ducted turbine concepts and open-centre horizontal axis turbines, which are both currently in prototype phase. The costs and challenges assosciated with traditional fixed support systems means that floating platforms may be a technologically and financially appropriate solution for turbine deployment, particularly in shallow waters. However, there are complex dynamic interactions between the floating platform and the flow incident upon the turbines. All these concepts exhibit interesting features and designs quite different to those known from the wind energy industry.

Duct pressure fieldSince the only existing analyses of ducted and open centre devices have been performed by the manufacturers themselves, and often only in controlled laboratory-scale conditions, it is of importance to the industry to conduct unbiased independent research using theoretical, computational and where appropriate experimental modelling. Numerical (Computational Fluid Dynamics, CFD) and experimental modelling is being performed using high performance computing and flow channel facilities at the University of Oxford.

The results of these studies may also be compared to the output from parallel studies being conducted at Oxford on other devices such as the THAWT concept.

Floating tidal fenceFloating tidal platforms are attractive as they offer a remedy to some of the key challenges for the installation and maintenance of tidal stream turbines, namely the cost and technical challenge of installing fixed support structures, and ease of access for turbine maintenance. A floating platform also allows larger turbines to be deployed in shallow waters, as the need to allow marine traffic to pass above the turbines is eliminated. Furthermore, floating platforms, with multiple turbines, can be designed to exploit the constructive interference effects that arise from deploying turbines in a closely spaced arrangement. However, in addition to the challenges of designing an appropriate mooring system, the roll, pitch, and heave motion of the floating platform due to waves as well as variations in tidal stream flow speed and the moment created by turbine thrust results in a more complex flow field being presented to the turbines. Numerical simulations are being used to parameterise multi-degree of freedom models to allow the floating platform - multi-turbine system to be modelled.