Developments in component technology are reducing the weight, frictional losses, energy consumption and maintenance costs of wind turbines. Phil Burge, communication manager for SKF explains

Both OEMs and energy companies are constantly seeking to maximise the operating life of wind turbines, while simultaneously reducing operating costs. As such wind turbine technology is developing rapidly. No more so than in the development of critical systems that are as robust, reliable and as long lasting as possible.

This has sparked a trend for ensuring that wind turbines are constantly operating at optimum efficiency, while requiring as little manual intervention as possible. However, meeting these goals can be a tough challenge, especially when it comes to refurbishing turbines that are already operating in the field. In order to make these objectives a reality, a number of new advances in component design look set to help increase service life and reduce operating costs in both new and existing turbines.

Bearing efficiency in mind

In particular, the use of new double row tapered roller bearings can increase reliability and eliminate the need for a main shaft, enabling particularly compact turbine designs. The Nautilus bearing from SKF, for example, allows OEMs to depart from the traditional main shaft design and integrate the bearing directly between the machine frame and the hub. In such designs, the nacelle dimensions and weight are also reduced, delivering further cost savings to the machine builder.

The latest bearings have been developed for multi-megawatt onshore or offshore wind turbines with or without a gearbox, and carry the rotor loads in terms of both force and movement, thus allowing only rotor torque to be transmitted to the drive train. Two rows of tapered rollers lock the unit axially, while a large number of rolling elements, offering precision between the raceways, enables large load carrying capabilities.

Moreover, these bearings have a large diameter, making them strong enough to withstand yaw and tilt movements. As a result, the only forces that reach the generator or the gearbox are torsional, generating energy and ultimately, profitability. This design also prolongs the drive train life, allowing improvements in turbine reliability to be realised.

Furthermore, some of the latest large double row tapered roller bearings feature a segmented PEEK (polyetheretherkeytone) cage to give higher operational reliability together with low friction. The segmented design of this enclosure allows it to minimise contact forces and friction still further. This also means that there are no additional loads to add to normal internal bearing forces. Moreover, this construction improves the guiding and, together with the internal design of the bearing, gives optimised load distribution among the rollers.

Further enhancements

Similarly, the latest rolling elements have been designed for optimised bearing performance, enabling maintenance intervals to be increased, while also giving high load carrying capacity with high stiffness. In addition, new yaw bearings with integrated gearing are helping to reduce the overall weight of nacelles, while the use of high efficiency bearings cut the frictional losses in rotating parts to save energy still further.

Just as critically, the intervals between essential maintenance are being extended by new automated lubrication systems that are connected directly to remotely monitored condition monitoring equipment. Among the latest innovations are high performance single-line, dual-line, multi-line and circulating oil lubrication systems that are suitable for use with a variety of components, including the main generator, yaw and blade bearings, as well as yaw and blade gearings, improving the effectiveness of lubrication tasks.

These devices feature distribution blocks that control the flow of oil to multiple bearings of varying sizes and ensure the optimum volume of lubricant is delivered to each lubricant point, eliminating the problems of carrying out the task manually, such as over or under greasing.

As an example, SKF’s WindLub centralised system cuts the time needed for lubrication, as well as extending service intervals by reducing wear and retaining the value of modern high output systems to minimise operating costs. The lubricant reservoirs used in this system have the capacity to contain supplies for up to two years as grease consumption is optimised in an environmentally friendly manner, minimising the need for manual intervention and overcoming the problems of having to carry out lubrication in remote and hard to access areas.

Making green greener

As the wind power sector continues to grow, so too does the technology that is making this clean, renewable energy more viable for all to use. Due to the development of the new generation of specialised engineering solutions, the latest wind farms are now more efficient than their predecessors. Just as importantly, these new innovations prolong equipment life in wind turbines, while minimising maintenance requirements and down-time to reduce operating costs, thus increasing the potential of wind power for the future.