a wind turbine may be controlled in a variety of manners to optimize operating parameters . in one arrangement , for example , the length or the pitch of a wind turbine rotor blade may be adjusted to avoid harmonic resonance frequencies . in another example , the length of a rotor blade may be modified to reduce noise or to optimize profits or both . the controls may be based on data from various types of sensors including accelerometers , sound meters , strain gauges and the like . actuation of extendable rotor blades can rotate wind turbine rotors without wind or generator pulsing affording multiple advantages . a battery test control may also be used to determine the operational readiness of a battery useful for a variety of purposes in a turbine .