ENERGY LOSSES IN FLOATING OFFSHORE WIND TURBINE WITH VARIABLE WIND DIRECTION

Carlos Armenta-Deu; José Lomo

Abstract

The paper analyses the effects of the variation of wind direction onto the performance of a floating offshore wind turbine (FOWT). The evolution of the Cp coefficient is developed as a function of the velocity of the yaw angle correction when realigning the FOWT after a wind direction change. The results are computed for velocities correction of the yaw angle between 1º/min and 5º/min. A maximum drop of the Cp coefficient of 7.4% has been found at the transient state. Simulation tests have been run over a period of 24 hours. The maximum drop value does not depend on the velocity correction of the yaw angle, but the elapsed time for the transitory state does, what affects the performance of the FOWT and the global power generation over a specific period. The loss of global power is inversely proportional to the velocity correction of the yaw angle, with a minimum loss of 0.83% for the case of 5º/min and a maximum loss of 4.16% for 5º/min. The absolute power loss in a marine turbine of 8 MW can reach values up to 0.33 MW. A quadratic dependence of energy loss on the yaw speed has been found within a 100% accuracy. The correlation shows there is a threshold value of 4º/min for the yaw speed beyond which absolute and relative energy losses maintain quite constant. This value is considered as the optimum value for the yaw speed to obtain maximum performance in the wind turbine.

Abstract

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