Senior engineers from National Renewable Energy Laboratory (NREL) are expanding a research partnership with operators, utilities and turbine manufacturers to determine why some key wind turbine components tend to wear too soon – sometimes within a few years of installation.
Generally, wind turbines are expected to operate for 20 years. Early equipment fatigue, especially in wind turbine gearboxes, threatens to reduce performance and drive up wind power costs, just as the industry is poised to capture a greater share of U.S. generating capacity, according to NREL.
Improving reliability is key to generating a consistently competitive power source. Both are needed if wind power is to meet 20% of the nation's electricity needs by 2030 – a scenario a U.S. Department of Energy report issued last year says is feasible.
The tests at the National Wind Technology Center (NWTC) focus on several aspects of gearbox performance, including the following:
– Automated spray lubrication. Wind turbines crank at low revolutions per minute under high torque, especially in the first stage of gearing, where heat and pressure are high. New designs have lubrication channeled directly to the bearing races.
– Oil cleanliness. New turbines have more aggressive filtration systems.
– Automated gearbox monitoring instruments. These systems are supposed to detect damaging operating conditions before a failure occurs.
– Micro-pitting. This phenomenon occurs as metal fatigue creates microscopic weak spots in gears that degrade the equipment over time.
– Load distributions on the gear tooth contacts and the bearing roller elements.
Initially, the gearboxes under review are being tested on the NWTC dynamometer, where NREL scientists will simulate a variety of loads and measure the results.
Later, the scientists plan to put one gearbox into test turbines at the Xcel Energy Ponnequin wind farm and monitor them under real load conditions. A second testing phase is likely to follow.
SOURCE: National Renewable Energy Laboratory
