Abstract
Deployment of co-located wind and tidal stream turbines is proposed as a method for reducing cost of electricity generation from either technology individually. Energy yield for wind turbines is modelled using an eddy viscosity wake model and for tidal turbines using a method of selfsimilar superposition of wake deficits. Yaw strategy is considered for the tidal turbines, finding that although a continuous yaw strategy generates highest yield, a slack-tide strategy offers a suitable compromise with mechanical complexity. A case-study of the MeyGen site in the Pentland Firth is considered for co-location. The addition of 12MW of wind capacity to a 20MW tidal array results in a two-fold increase in annual energy yield, compared to operating the tidal turbines alone. Phasing of the tidal cycle means that during a neap tide, the combined system may be entirely dependent on wind generation, but during a spring tide there is a regular tidal supply. Steady state loads for wind and current are also modelled for a braced monopile support structure. For tidal turbines only, the mean probable loads vary by 12% across the array. Net horizontal force on the tidal turbines is 28% greater than on the wind turbines. However, due to the distance between turbine axis and base, the magnitude of the base moment for the combined support structure is found to be driven by wind loading.