Tidal flow variation at a test site: instrumentation, physics, or both?

In 2023 and 2024, a floating tidal stream turbine was tested at the Marine Energy Test Area at Warrior Way in Pembrokeshire, Wales. These tests included quarter scale and full scale testing of a two bladed turbine with hydraulic power take off, intended to illustrate lower cost methods of harnessing tidal energy. Concurrent with these tests, the tidal current at the site was measured using bottom mounted acoustic doppler profilers, a downward facing profiler mounted on the floating platform as well as by a velocimeter positioned parallel to the top of the rotor swept area. A converging beam acoustic doppler profiler developed at Swansea University was also deployed during 2023 alongside conventional instrumentation. The deployment of different instrument types in close proximity allows for comparison between the instrument types, building on previous work. The variation in flows between devices of the same type located between 30m and 60m apart is also discussed, with similar average speeds seen on each instrument but clear differences observed on both the diurnal and spring-neap periods.