Tandem turbine testing – interactions between devices

The interaction between the two turbines is investigated by pushing test in a calm water lake. Investigation of both in-plane and in-line configurations for the two turbines was undertaken. The research found no discernible interaction between the device when In-plane. For in-line spacing, at close proximity, two turbine diameter (2D) spacing between upstream and downstream devices resulted in a 63% reduction in performance of the downstream turbine. At 6D separation the performance of the second turbine remains poor at 59% reduction. It was identified however that a 1.5D lateral and 3D downstream displacement resulted in no noticeable interaction with the downstream device. These results are significant for developers with limited footprint seeking to maximise power output.

Control system – Speed control

The research highlights the importance of a tidal turbines control, which has a significant impact on performance characteristics when challenged with nonideal conditions. The research showed a 13.7% higher peak performance when closed-loop control was used in the tidal environment. This has significant implications for developers transitioning between simple lab experiments and field deployments.

Uncertainties in flow characteristics

By developing an alternative methodology for the use Acoustic Doppler Profiler (ADP) measurements for tidal energy resource characterisation, existing international standards have been challenged to reduce the error from ADP measurements in calculating the Mean Representative Velocity (MRV). This initial investigation has led to further challenges of the IEC TC114:62600-200 standard which will be issuing a second edition. The benefit of reducing the error in the MRV is critical due to its cubic relation to Annual Energy Prediction, a key metric used in tidal energy project developments, globally.