Construction of a Universal Hydraulic Power Take-Off for Wave Energy Converters. Mathematical Modelling and Validation Testing

This paper presents the construction, mathematical modelling and validation testing of a scaled universal hydraulic Power Take-Off (PTO) device for Wave Energy Converters (WEC). A specific prototype and test bench were designed and built to carry out the validation tests. The results obtained by these tests were used to adjust an in-house mathematical model. The design of the PTO device led to an international patent application. The PTO was initially designed to be coupled to a scaled wave energy capture device with a low speed and high torque oscillating motion and high power fluctuations. Any energy capture device (ECD) that fulfils these requirements can be coupled to this PTO, provided that its scale is adequately defined depending on the rated power of the full scale prototype. The initial calibration included estimation of the pressure drops in the different components, the pressurization time of the oil inside the hydraulic cylinders and the volumetric efficiency of the complete circuit. Since the overall efficiency measured during the tests ranged from 0.69 to 0.8 and the dynamic performance of the PTO was satisfactory, the results are really promising and it is believed that this solution might prove effective in real devices.