Experimental and numerical study of hydrodynamic responses of a combined wind and wave energy converter concept in survival modes

Abstract

The Spar Torus Combination (STC) concept combines a spar floating wind turbine and a torus-shaped heaving-body wave energy converter (WEC). Numerical simulations have shown a positive synergy between the WEC and the spar floating wind turbine under operational conditions. However, it is challenging to maintain structural integrity under extreme wind and wave conditions, especially for the WEC. To ensure the survivability of the STC under extreme conditions, three survival modes have been proposed. To investigate the performance of the STC under extreme conditions, model tests with a scaling factor of 1:50 were carried out in the towing tank of MARINTEK, Norway. Two survival modes were tested. In both modes, the torus WEC was fixed to the spar. In the first mode, the torus WEC is at the mean water surface, while in the second mode, it is fully submerged to a specified position. The measurements in the model tests were the 6 degrees of freedom (D.O.F.s) rigid body motions, mooring line tensions, and the forces between the spar and torus in 3 directions (X, Y and Z). The wind speed was also measured by a sensor in front of the model and the wind force on the wind turbine disk was measured by a load cell installed on top of the tower. This paper describes the model test set-up for the two survival modes, the test results and the numerical model. The results from the entire test matrix of model tests and numerical simulations are presented and compared. The numerical results agree well with the test results for the survival mode with the WEC fully submerged for which the linear hydrodynamic loads dominate. In addition, several nonlinear phenomena were observed during the tests, such as wave slamming, Mathieu instability and vortex induced motion. These nonlinear phenomena were not captured by the present numerical model and the work on a refined hydrodynamic model is still ongoing.

Real-Time Hybrid Model Testing of a Braceless Semi-Submersible Wind Turbine: Part II — Experimental Results

“…One form of non-geometrical scaling is to replace the wind turbine rotor with a drag disk (e.g. [6,7]), which gives the correct mean thrust and provides some aerodynamic damping, and can provide gyroscopic forces if spinning. A more sophisticated method of non-geometrical scaling is to modify the wind turbine airfoil shape and chord length in order to obtain improved performance at low Reynolds numbers.…”

Operational Performance of a Combined TLP-type Floating Wind Turbine and Heave-type Floating Wave Energy Converter System

“…It was showed that the STC system could increase total power production compared to the segregated FWT concepts [7][8]. The possible slamming and green water effects of the STC system have been in laboratory tests, a 1:50 scaling ratio model test of the STC system under operational conditions was performed to assess the performance of the concept, two survival modes tests (fixed model and submerged model) were proposed to investigate the performance of the STC in extreme conditions [9][10][11].what is more, the long-term performance in terms of annual power production, structural fatigue damage, and extreme responses of the STC system has been further investigated using coupled wind-wave time-domain analysis with the consideration of effect of different survival conditions [12][13].So far, there is limited information about the conceptual design of the combined WT and WEC nearshore systems with the fixed -bottom foundation.…”

Wave- and Wind-induced Responses of the Semisubmersible Wind Energy and Flap-type Wave Energy Converter Based on Experiments

“…For the case of a floating bottom rotating flap-type WEC, Pecher et al (2010) modelled the PTO with the use of a load adaptable friction wagon mounted on a rail, a potentiometer and a force transducer. So far experimental investigation of combined wind/wave concepts has been reported by , Wan et al (2015Wan et al ( , 2016 based on different physical model set-up strategies for the different parts of the combined concepts. Michailides et al (2016aMichailides et al ( , 2016b compared the experimental data of the SFC in operational and extreme conditions with numerical predictions.…”