Mechanical Re-Design of a Wells Turbine Blade to improve the efficiency of the LIMPET Wave Energy Conversion System

A. Montes-Cabrera, D. Chávez-García, A. Flores-Valentín, J. López-Leyva
Centro de Enseñanza Técnica y Superior,

Keywords: Wells turbine, OWC, LIMPET, variable geometry control surfaces


This paper focuses in improving the efficiency of the Land Installed Marine Power Energy Transmitter (LIMPET) wave energy conversion system. This system generates energy based in the principles of oscillating water columns (OWC); it transforms the energy in oscillating waves into an airflow, which rotates a turbine-generator, and therefore electrical energy is obtained [1]. Queen’s University Belfast [2] determined that, in order to improve the energy production this system, the airflow produced by the waves has to be controlled to reduce stalling and the turbine configuration has to be re-designed. The LIMPET system uses a Wells turbine with a diameter of 2.6 m; a nominal operating speed of 1050 RPM; a hub-to-tip ratio of 0.62; and, a NACA0012 blade form with a chord of 320 mm. The modification proposed for the re-design of the turbine configuration is to apply an adaptive surface blade, capable to vary its surface contour depending on the airflow detected in the tunnel. By controlling the surface contour, stalling from low and high airflows can be prevented and it would also help to increase the operating range of the turbine, making it capable to start rotation at lower airflow profiles (this means less current needed for starting the turbine-generator rotation). It is intended to use a morphological surface to avoid heavy mechanisms and assemblies making the system lighter, and to increase in a 10 – 15% the energy capture by the turbine, just as stated by professor Sridhar Kota [3]. This upgrades would make the LIMPET system more efficient and suitable to be applied as a wave energy conversion system around the world. The main reason of improving this system is to make it possible to install it in the coasts of Mexico; Wells turbine is one of the most efficient OWC technologies nowadays [1]. It was estimated by Queen’s University that a minimum incidence of 15.9 kW/m energy wave was required to make it work, and the energy wave incidence in most of the Mexican coastline is 15-20 kW/m. The reason of this work is to re-design the mechanical profile of a Wells turbine to improve efficiency. References [1] (2016). Ahmed S. Shehata, Qing Xiao, Khalid M. Saqr, Day Alexander. Wells Turbine for Wave Energy Conversion. [2] (2002). Queen’s University of Belfast, Wavegen Ireland Ltd., Charles Brand Ltd., Kirk McClure Morton, IST Portugal. Islay LIMPET wave power plant. [3] (2018). Sridhar Kota. Flexsys.