Just as there is an aftermarket for the automobile industry, there is one for the wind industry. Although the wind turbines going into service in the last few years are technically the most reliable to date, active engineering minds are finding ways to improve them. For instance, the turbines on a wind farm probably came from an OEM that placed the lowest-priced bid, and so may have not included many of the available options, such as leading-edge protection on the blades, a load-spike limiter on the main shaft, or even a condition monitoring system. This modest assemblage of admittedly extra-cost options just scratches the surface of what a wind farm owner might add on to improve power output and turbine reliability. Here’s a slightly longer list of wind turbine upgrades.
SCADA, or Supervisory Control and Data Acquisition systems, tell owners and operators what and how the turbine is doing. Some older machines were not fitted with such capability. Recent regulations have intruded and require bringing older machines up to date. While some machines of about 2003 vintage, the dawn of the modern wind era, could be purchased without a SCADA system, the systems are now a necessity. Without the remote-control capability, a technician would have to drive to the site to learn anything about the turbine. And although it is not a condition monitoring system, SCADA is a step in the right direction.
Vortex generators are small fins that attach to blades along about two-thirds of its length. They keep the airflow attached to the blade for longer periods, thereby increasing its lift and the torque the rotor produces. One developer claims up to a 10% improvement in power production after adding VGs to a rotor.
Torque limiters prevent shock loads from transmitting through the drivetrain. The device functions like a clutch. So, for example, during an emergency stop when the disk brake tries to bring the rotor, gearbox, and generator to a full stop in a short period, the driveline winds up like a huge spring. You can imagine the rotor rocking back and forth, but still spinning. That sends the load spikes through the gearbox, which essentially hammers the bearings. Once that happens, the bearings shed particles into the oil, which eventually damages the gears, and the function of the gearbox. Filtering out the load spikes, or just keeping them positive, lengthens the life of gearboxes.
Particle detection devices monitor oil for debris. Although it is the filter’s job to clean the oil, recommended practice suggests occasionally letting a lab analyze an oil sample. Mounting a particle counter in a nacelle may provide similar information and more frequently.
Several particle counters are on the market. The developer for a recent one says it is intended for stationary online measurement of dark fluids. It sports a built-in system that can dilute dark fluid samples prior to measurement, thereby reducing the sample’s turbidity level. As light passes through the liquid, electromagnetic waves may be deflected or absorbed when meeting the particles in the measuring cell. The light effect on the particles is analyzed with the help of an optical electronic hardware. The measuring result provides information on the number of particles per milliliter, and on the size of each single particle. Eight different size channels allow counting particles in eight size classes.
Lightning protection essentially involves directing a lightning strike to ground. The problem with lightning is not one strike, it’s the effect of many strikes over the years. While most blades have a lightning receptor near the blade, and down-wires that lead to ground, the receptor is often less effective than recent designs. One such idea places a row of several, thin metal discs in a cross pattern, centered on and connected to the receptor, ensuring that lightning hits the diverters. Blades are the second biggest wind turbines maintenance issue after gearboxes. The diverters promise to minimize the problem.
Filed Under: Featured, O&M, Turbines