CHICAGO – Wind turbine lubricant demand is expected to grow at a compound annual rate of 7.5 percent through 2020 thanks to a healthy increase in wind turbine installations, said Chuck Coe at the ICIS North American Industrial Lubricants conference held here.
According to Coe, president of Grease Technology Solutions, wind turbine lubricant demand reached between 70 million pounds and 80 million pounds in 2015. Gear oil makes up 70 percent of that demand, followed by hydraulic fluid at 25 percent.
Greases are only 5 percent but, frankly, its the most challenging application. Its 5 percent of volume but Id be willing to bet its probably 15 percent to 20 percent of the lubricant suppliers margin, said Coe.
Gear oil is used for the gearboxes and hydraulic fluid is used in the hydraulic systems that control the pitch, which is the angle of the blades in the wind. Though it makes up the smallest amount of demand, grease is used in the highest number of locations: in the main rotor shaft bearing; the yaw bearing; pitch or blade bearings; pitch drive gears; and generator bearings.
The gearbox and hydraulic systems use considerably more volume of lubricants compared to the greased bearings, explained Coe in an interview.
Typically National Lubricating Grease Institute 1.5 to 2 grade lithium, lithium complex and calcium greases are used in pitch, yaw and main bearings, and NLGI 2 grade lithium, calcium and lithium complex greases are used in generator bearings.
Demand is a function of many things, including operating capacity and relubrication frequency. In terms of operating capacity, a larger turbine doesnt tend to use more lubricants, so you get more power with less lubricant, Coe noted. This means that there may not be a direct correlation between lubricant demand growth and wind energy capacity. Turbines are often in remote locations and stand at least 80 meters tall, complicating the task of relubrication.
Theres a huge drive from both the wind turbine operators and the wind turbine original equipment manufacturers to try and up lubricant life and reduce relubrication frequency, said Coe during his presentation. This dampens lubricant growth rate.
Because of the drive to reduce relubrication intervals and because weather conditions around wind turbines can be extreme, penetration of synthetics among wind turbine greases is roughly 75 percent. The higher viscosity index of synthetic oils offers better low-temperature mobility and high-temperature thermal stability, increasing lubricant life. You want that long life to reduce the maintenance, noted Coe.
Photo courtesy of Senvion Assets