As the world seeks cleaner sources of electricity, renewable energy is heralded for not burning fossil fuels to produce energy. For example, solar panels use sunlight to generate electricity, while wind power harnesses energy from the wind.
However, wind turbines contain moving parts and they require lubricants to operate at peak performance due to environmental and mechanical pressures.
The amount of oil used by a wind turbine varies greatly depending on the size and type of turbine. A small turbine for powering the home only requires a very small amount of oil, whereas the largest offshore wind turbines regularly need topping up with large amounts of oil and other lubricants to keep them running efficiently.
Wind turbines operate across the globe, even in some of the harshest climates. As the industry grows, it is expanding into more remote areas and using larger and larger wind turbines. Therefore, the use of industrial lubricants is critical for reliable energy production and operational efficiency. Proper maintenance including the use of oil ensures the reliability of cost-effective wind energy.
As the fleet of wind turbines ages, many are entering a post-warranty period. This means that equipment repairs are becoming more costly for wind farm owners. Thus, proper maintenance including the use of oil to prevent equipment failure is critical to reduce costs and promote renewable energy production. This is encouraging the use of conditions-based monitoring and maintenance.
Why do wind turbines need oil?
Lubrication protects wind turbines from premature wear of many critical parts so they operate at maximum performance for greater productivity. Grease oil and grease are used in the gearbox, pitch gear, open gear, and yaw gear.
Wind turbines contain moving parts and without proper lubrication, this movement causes excessive friction. Most wind turbines contain turbine blades that spin the rotor. The nacelle sits on top of the wind turbine tower and contains the gearbox, generator, controller, and break.
Engineers design wind turbines to be stable enough to withstand significant loading, yet small enough to fit within the nacelle. Each component plays a critical role in wind energy production. For example, the yaw motor and drive ensure that the wind turbine is perpendicular to the wind, harnessing the most energy. If a component fails, it can result in downtime, resulting in less energy production.
However, wind turbines need to reliably operate across the globe. Often, wind turbines are located in harsh environments. For example, dust or other airborne particles can be abrasive, leading to equipment failure. Thus, adequate lubrication is critical for avoiding these issues.
Unfortunately, gearboxes are somewhat prone to failure. Variations in wind speed and direction, vibration, and the ingress of water or moisture can create wear and tear, making it vulnerable to breakdowns. Factors that can adversely affect the main gearbox include variations in wind speed and direction, temperature, vibration, and the ingress of moisture. These factors make the gearbox a vulnerable component of a turbine’s drivetrain.
One common issue in gearboxes is micropitting, a unique gear failure mode that occurs in a rolling or sliding contact environment. If left unchecked, it can lead to teeth breaking and the need to replace gears. Unfortunately, replacing a gearbox causes wind farm downtime, leading to operating losses. However, micropitting can be minimized with adequate lubrication, reducing repair costs and wind energy production losses.
In wind turbines, micropitting occurs due to a constantly changing load. In addition, lack of lubricant film thickness, viscosity issues, or foaming can contribute to micropitting in wind turbines. Unfortunately, water and moisture in the gearbox can impact the performance of lubricants, and is difficult to remove water without changing the oil.
Changing the oil in a wind turbine gearbox is a challenging yet essential task that requires several technicians and hours of time. Periodic analysis of the lubricants through oil sampling and oil debris monitoring can help determine when this needs to be completed.
What type of oil is best for wind turbines: conventional mineral-based oil or synthetic oil?
In the wind energy industry, synthetic oils have a better reputation than mineral-based oils due to several factors. For example, synthetic oils have a lower pour point, which enables the gearbox to operate more efficiently at lower temperatures. Also, synthetic oils have a higher viscosity index. Thus, its viscosity changes less with temperature fluctuations than mineral-based oils.
What are the best lubricants and practices for wind turbines?
The best way to determine the ideal lubricants, fill volume, and removable filters are to refer to information from the wind turbine OEM. Typically, the oil fill volume is 60% of the gearbox capacity. Likewise, the frequency also varies based on the condition of the oil, manufacturer recommendations, and the type of lubricant used.
In some cases, changing the oil in the gearbox requires merely draining and filling. However, when converting to a new wind turbine gear oil with poor oil compatibility with the previous lubricant or when there are gearbox deposits and contamination, it is critical to flush and perhaps even clean before filling.
Different lubricants are used on various wind turbine components and are manufactured by various companies. For example, Mobil produces a line of synthetic oils and greases for various wind turbine components but recommends referring to OEM recommendations. AMSOIL produces a line of industrial lubricants for wind turbines. Kluber lubrication makes a product that is designed to grease all gears, the Klüberplex BEM 41-141.
|Gearbox||Mobil SHC Gear 320 WTMobilgear SHC XMP 320|
|AMSOIL PT Series Synthetic Power Transmission EP Gear Lubricants|
|Klübersynth GEM 4-320 NKlübersynth GH 6-320Klüber Summit Varnasolv HV (flushing oil)|
|Main, pitch, yaw, and generator bearings||Mobil SHC Grease 460 WTMobil SHC Grease 102 WTMobilith SHC 100|
|AMSOIL SG Series Synthetic Gear Oil|
|AMSOIL SG Series Synthetic Extreme-Pressure Gear OilAMSOIL Synthetic Power Transmission EP Gear Lubricants|
|Klüberplex BEM 34-131 NKlüberplex BEM 41-141Klüberplex BEM 41-301Klüberplex AG 11-461/462Klübersynth AG 14-61|
|Hydraulic system||Mobil SHC 524Mobil DTE 10 Excel Series|
|AMSOIL Multi-Viscosity Ashless Hydraulic Oil|
|AMSOIL Synthetic Turbine Hydraulic Brake Oil|
|AMSOIL Synthetic Multi-Viscosity Hydraulic Oil|
|AMSOIL Synthetic AW Series Anti-Wear Hydraulic Oils|
|Ancillary gearboxes||Mobil SHC 600 Series|
|Open gears||Mobiltac 375 NC|
|Mobilgear OGL 007|
|AMSOIL Open Gear Grease|
What is conditions-based monitoring of wind turbines?
Whereas monitoring industrial-scale wind turbines used to require having a technician climb a tower to inspect the wind turbine, wind farm operators are increasingly using condition-based monitoring to detect potential issues and prevent costly repairs and downtime as needed.
Condition monitoring systems (CMS) use sensors and electronics to accumulate and analyze data. For example, vibration monitoring analysis can help in making maintenance decisions and predicting failures.
Lubrication is a critical aspect of conditions-based monitoring and maintenance by identifying real-time operating conditions and proactively correcting issues. For example, lubrication analysis can provide insights into equipment conditions, lubrication conditions, and contamination.
As the wind energy industry matures, there has been greater development of high-performance and customized component lubricants. As the wind farm fleet ages, wind developers are putting more emphasis on proactive maintenance to reduce downtime and boost reliability. Thus, the use of specialized industrial lubricants is becoming an increasingly prominent way to achieve this.