The use of VAWT to reduce the cost of Offshore wind Energy

Benoit Augier, IFREMER, Brest Wave&Wind Test tank, Plouzané, France, Camil Matoug, IFREMER, Brest Wave&Wind Test Tank, Plouzane, France, Benoit Paillard, HydroQuest, Brest, France, Alan Tassin, IFREMER, Brest Wave&Wind Test Tank, Plouzané, France, Guillaume Maurice, HydroQuest, Grenoble, France and Stephane Barre, CNRS, Laboratoire des Écoulements Géophysiques et Industriels LEGI, Grenoble, France
Horizontal Axis Wind Turbines HAWT have been intensively developed during the last decades and have now the monopole for bottom fixed wind energy harvesting. The recent rise of offshore floating wind energy project raises the question of the interest of Vertical Axis Wind Turbine. VAWT are indeed very good candidate for the FOWT application with low center of thrust and center of mass. The direct consequence of this low centers would be the significant reduction of the size of the floater impacting directly the building and the installation cost.

The aim of the project is to experimentally test the performance and the behavior at sea of two 10MW VAWT and HAWT on the same floater for different sea state and wind conditions. The original counter-rotating bi-rotor VAWT “Owlwind”, developed by HydroQuest and LEGI is tested on the 10MW NAUTILUS FOWT platform together with the DTU10MW HAWT rotor. Tests are done at 1:42 scale at the Wave&Wind test tank of Ifremer, Brest, France.

In order to compensate the scaling conflict between the Froud and the Reynolds numbers inerrant to the test of floating wind turbine in wave tanks, this work proposes a hybrid testing method consisting in simulating the thrust of the turbine by an external actuator, a fan. The thrust is coupled to a real-time “Software-in-the loop” (SiL) approach that computes from an aerodynamic simulation the expected aerodynamic load due to the measured platform motions. The paper will focus on the experimental campaign and its results.

Results illustrate that at the roughest sea state of the golf of Main (Hs =10.9m and T = 15s) the VAWT is still producing its nominal power when the HAWT has to degrade its performance significantly, as expected. Comparison with simulation confirms the safe general behavior of the VAWT due to the low centers of thrust and mass. The conclusion is that with 20% lower centers, the platform could be reduced up to 40%.