Method and arrangement to determine a wind-speed

摘要

The invention relates to a method and to an arrangement to determine the speed of the wind, which acts on a wind-blade of a wind-turbine. According to the invention an optical-signal with a known frequency is sent from an optical-transmit-unit to a joint measurement volume. The optical-signal is scattered and reflected by atmospheric particles of the joint measurement volume. The optical signal is shifted in its frequency due to the Doppler-principle, too. The frequency-shifted optical signal is received by a receive-unit. The frequency-shifted optical signal is compared with the sent optical-signal to determine the wind-speed based on the shifted frequency, which is caused by the atmospheric particles.