In response to this problem, Bosch Rexroth has developed a technology called BLADEcontrol that continuously monitors the state of each individual rotor blade. A sensor system detects the signs of damage that can go unnoticed in visual inspections to help avoid turbine downtime. In the event of serious damage, BLADEcontrol sends a signal to the system's control unit, which can shut down the turbine to avoid breakage. The system also detects other rotor problems, such as aerodynamic imbalances, loose parts in the blade and hub, and incorrect pitch settings.
One important feature of this system is the ability to detect and avoid ice buildup. Ice can change the natural oscillation of a rotor blade, with the frequency of the natural oscillation decreasing in proportion to the increasing mass of ice. Using highly sensitive sensor systems and evaluation processes, the system accurately measures ice down to millimeter thicknesses to make sure the turbine blade is sufficiently free of ice before it is started.
The system can also detect invisible damage to the rotor blade, inside and out, and signs of wear that change the natural oscillations of the rotor blade. In each rotor blade, measurements collected using highly sensitive, multidimensional acceleration sensors are compactly arranged in a single module. BLADEcontrol is available as an option for new turbines, or it can be used to upgrade the operation of previously installed turbines.
The move to larger megawatt turbines
Gupta said another major trend consistent with what Bosch Rexroth has seen is the wind industry moving to larger megawatt turbines. In the past, 1.5- or 2-megawatt turbines were the industry standard, but now turbines are moving up to 2.5 to 3 megawatts.
But even with the trend toward large turbines, the jury is still out on the move to more offshore turbine installations. Not all operators have bought into the value of offshore applications, because these turbines are expensive. "In places like Europe, where there is a relative shortage of land, offshore might offer good incentives," Gupta said. "But in the US, why would you want to install offshore when there is plenty of open available land with good wind blowing. There isn't a need to go offshore and live with all of the high costs of repair and maintenance."