Getting the most out of wind turbines with the right lubricant

Wind turbines place very high demands on lubricants and can degrade standard lubricants, which increases costs, and shortens the life of traditional lubricants. Wind power project operators looking to maximize productivity, reliability, and efficiency of their equipment should carefully consider what fluids to use.

However, today's market offers many choices, meaning that many different aspects of the turbine oil should be considered. First and foremost, only fluids that meet OEM requirements should be considered. After that, turbine operators should consider the performance aspect of the lubricant, as well as how the fluid will impact the total cost to operate the turbine.

Wind turbines operate around the world in a variety of different climates. Due to the wide range of climates, fluids contained in the wind turbine need to perform in a wide range of conditions from very hot to very cold ambient conditions.

In addition, many wind turbines are located in very remote locations meaning servicing these wind turbines can be time consuming and difficult. Fluids must be designed to be dependable and long-lasting and provide protection for the components for the reliable generation of power.

Fluids based on Gas-to-Liquids (GTL) base oils can accomplish many of the performance requirements needed for wind turbine operation. GTL-derived hydraulic fluids used in the hydraulic pitch and brake systems typically are fluids that have a wide temperature operating window (high viscosity index), good low temperature properties (pour point and Brookfield viscosity) and do not change viscosity over time (shear stable). In addition, the fluids need to be resistant to oxidation and thermal degradation to ensure a long oil life and be resistant to wear on critical system components. GTL base fluids cannot do this on their own, but respond very well to additive chemistry to ensure excellent performance.

Shell began the GTL journey in 1973 in their Amsterdam R&D labs. GTL is the integrated process of the manufacture of synthesis gas (syngas) from natural gas, the subsequent conversion of the syngas into hydrocarbons via the Fischer-Tropsch (FT) reaction, followed by liquid processing that typically consists of hydro-processing reactors and distillation columns to generate the final products with the targeted properties. To this day, GTL remains technologically complex and relies heavily on catalyst and processing expertise.

In 2011, Shell commissioned the Pearl GTL plant in Qatar with joint venture partner Qatar Petroleum, to produce 140,000 bbl/d of a wide range of high-quality hydrocarbon products, ranging from chemical feedstock to fuel, wax, and base oil. That base oil is then distributed to Shell lubricant blending plants in the various regions for manufacturing of finished lubricants.

GTL base oils are superior to crude-derived base oils and contain virtually none of the impurities such as sulfur and nitrogen that are commonly found in crude oil-derived products. GTL base oils are colorless, odorless, and extremely low in aromatics, while also having a lower density and outstanding thermal properties when compared to crude oil-derived counterparts. That makes GTL base oil highly desirable for formulation of finished lubricants for a wide variety of industrial applications, including wind turbines.

GTL base oils are excellent quality API Group III base oils, with physical and performance properties such as viscosity index, volatility, oxidative stability, low temperature performance, surface properties (such as foaming and air release), and friction characteristics similar to commercial polyalphaolefin base fluid (PAOs), and are considerably better than mineral derived base oils.

The characteristics of GTL derived lubricants offer advantages such as:

• Long service life
• Suitability for extreme temperature conditions
• Energy efficiency
• Excellent wear protection
• Meet or exceed latest industry OEM specifications
• Sustainability: Energy efficiency and long service life to help reduce CO2 footprint

Shell continues to invest heavily in GTL research and development to enhance process efficiency and flexibility, as well as to produce new products to meet the future challenges of the energy transition for sustainable growth.

Shell Tellus S4 VE utilizes GTL base fluids in combination with special viscosity modifiers to minimize the change in viscosity across a wide range of temperatures. It exhibits excellent fluid pumpability at sub-zero temperatures, which shortens warm-up time, saving energy. In addition, the high viscosity index at high temperatures enables consistent fluid film thickness even in very hot conditions, helping to protect critical system components.

Shell Tellus S4 VE's unique additive technology in combination with GTL base oils results in a fluid that is very resistant to oxidation translating to long oil life meaning fewer oil changes over time. Tellus S4 VE benefits from the rapid air release properties of GTL, minimizing the risk of trapped air in the hydraulic fluid resulting in noise and potential wear from air contamination.

Proper lubricant selection is critical to optimize performance and reduce total cost of wind power project ownership. Selection of a premium lubricant based on GTL base fluid such as Tellus S4 VE for hydraulic components in wind turbine applications can help extend life of the oil and the life of the equipment. This of course is also dependent on a proactive lubricant monitoring program. Lubricant monitoring enables end users to optimize their equipment's performance and enhance productivity.

This guest column was supplied by the Shell Lubricants Technical Team (www.shell.com/business-customers/lubricants-for-business.html).