Aerodynamic performance and noise emission of different geometries of Wells turbines under design and off-design conditions

The path to the World’s energy system decarbonisation requires the contribution of a mix of renewable energy sources. In particular, wave energy and oscillating-water-column (OWC) devices can be significant contributors. However, they are still in an early stage of development, and their levelized cost of energy (LCOE) is still too high to compete in the utility market. The Wells turbine is an attractive solution to reduce the LCOE of OWC devices. Completing the available information in the literature on the performance of different Wells arrangements is a necessary step towards decision-making on which configuration is most cost-efficient given the hydrodynamic characteristics of a particular OWC wave energy converter (WEC). Furthermore, there is a research gap on these devices’ acoustics, which needs to be filled, given the impact noise might have on surrounding ecosystems. This study investigated the aero-acoustics performance of four Wells turbine geometries, including monoplane and biplane turbines with and without guide vanes. Experimental tests of the turbine models were conducted in an open-circuit test rig under design and off-design flow conditions. The research provides accurate aerodynamic data on very high flow rate (pressure) coefficients, essential to turbine-generator control algorithms and OWC WECs wave-to-wire numerical models. A specific noise level definition was inferred by analysing the aerodynamic noise sources in Wells turbines. This allows the prediction of noise emission from geometrically similar turbines of different sizes and rotational speeds from the experimental noise data collected with the tested Wells turbines.