Design optimization and experimental validation of a two body Wave Energy Converter with adjustable Power Take-Off parameters

Abstract

Wave energy is extracted from the motion of sea waves. The technologies to convert this energy into electricityhave not yet reached maturity and there is no clear dominant design. In this work, a design methodology isproposed for a two-body Wave Energy Converter (WEC) with a novel configurable electromechanical Power-Take-Off (PTO) that allows setting its parameters for optimal power output according to wave conditions. Aprototype has been modeled, designed and tested experimentally. It is intended for low power and energyself-sustainable applications, such as in telecommunications and data acquisition. This work addresses themodeling, optimal design, and parameter setting, to obtain maximum power output and efficiency for thisclass of WEC. A floating body is connected via the PTO to a submerged body in neutral buoyancy. If the PTOparameters are correctly set to match the external frequency of the waves, the system can operate close to resonancecondition, which maximizes the generated power.Modeling aWEC can be extremely complex, so a linearmathematical model originally proposed by Falnes was adapted to find optimal PTO parameters for both regularand irregular waves. To validate the design model, tank tests were performed. Optimal PTO parameters in theWEC were determined experimentally. In the experiments, 16 cm high waves and 0.55 Hz of frequency wereused to test multiple design parameters searching for optimal power output. Peaks of up to 20Wwere generatedwith these waves. Extrapolating the experimental results, output power in the range of 400–600 W and anefficiency of 48.3% can be expected for 1 m high waves. The design model gives an acceptable prediction forthe amplitude of the relative motion between bodies, the optimum damping coefficient of the PTO (^cpto), andthe maximum generated power. The design model also makes a good prediction for the optimum stiffnesscoefficient (^kpto) for smaller values of the mass of the submerged body.