The Wind Energy Challenge

written by Gabi Olpp on 03.08.2018

Wind energy is one of the fastest-growing forms of power generation worldwide

In terms of installed capacity, China, USA, Germany, India, Spain and the UK are the six countries that dominate the global wind energy market. China remains the most important single market, and the highest growth rates are currently being recorded in Asia as a whole.

Wind turbines are modern power stations. Their operations are governed by a simple principle. Wind movement is transformed into a rotary motion by means of rotor blades and converted into an electrical current by means of a generator. Wind turbines are sustainable and offer flexibility as well as constantly falling energy costs. Immense growth opportunities are therefore opening up for this technology.

What role does hydraulics play in wind turbines?

The technology used in wind turbines has reached such a high quality level that wind turbines today achieve an operational availability of about 98%. At the same time, however, the annual maintenance costs must not exceed 2-3% of the investment. This in turn means that to ensure this high availability level, modern hydraulic components and controls must work extremely reliably and also have a long service life.

In functions such as pitch control, yaw and rotor braking, and the supply of hydraulic power from power packs, Bucher Hydraulics components have established an excellent reputation. Many well-known systems integrators have been using our reliable and durable components, systems and subsystems for decades because they achieve a high degree of functional reliability.

Tailor-made solutions for specific, application-focused challenges

To provide the optimum solution for wind turbines, we develop customer-specific subsystems that are based on our proven, high-quality standard components and are therefore perfectly matched to one another – a subsystem is thus much more than the sum of its parts.

Overview of our product portfolio

Bucher Hydraulics offers components and subsystems for the following functions

Pitch control – responsive, safe and economical for wind power

Pitch drives not only ensure an optimum power flow, they are also responsible for the safety of the entire turbine in strong winds and storms. The pitch control principle – blade-angle adjustment – means that each individual rotor blade is infinitely adjustable via the electronics and hydraulics. This ensures that the electrical power required by the consumer is produced regardless of varying wind speed. If no power is needed, the blades simply rotate out of the wind. This prevents unwanted acceleration of the rotor and protects the rotor hub from extreme loads.

Rotor brake and lock – controlling and securing large forces for maintenance work or system shutdown

To prevent unintended movement of the rotor, systems with lower electrical power ratings and "stall control" usually employ passive brakes. The brakes are applied by integral spring packs and released by building up a pressure.

In the megawatt range, however, active braking is used. Here, the brakes are applied by a pressure build-up and released by allowing the pressure to decay. Return springs are sometimes used to assist the release action.

If on/off hydraulics with no progressive control are used for braking, very high torques can build up in the entire drive train, and this is frequently the cause of damage. In order to control the braking process gently, we recommend the use of pressure control. When the rotor is at a standstill, additional locking can be provided by a hydraulically actuated bolt.

Yaw brake – protecting high-value system components

The purpose of the yaw brake is to hold the nacelle in the correct position pointing into the wind. If the nacelle has to be swung round to accommodate a change in wind direction, this is done via the tower gear rim and by means of electric motor-powered gear drives. To do this, the clamping pressure on the yaw brake has to be reduced to a precisely defined braking pressure. This prevents the force-reversals that are generated by the effects of wind changes on the nacelle from passing unchecked to the gear drives and gear rim. Depending on the hydraulic concept, the yaw-brake controls are supplied either by the central hydraulic system or by independently positioned power packs with a pressure-monitored bladder accumulator.

Lubricating, filtering and cooling – vital for a long service life

Due to the high performance requirements, there is an increasing tendency towards the use of synthetic gear oils based on polyalphaolefins and esters, and also of polyglycols. Their ageing resistance and load capacity are superior to those of mineral oil, as are their friction and power-loss values. Lengthier intervals between maintenance and the higher efficiency generate substantial cost savings. Taking advantage of these superior properties does, however, necessitate more stringent control of oil cleanliness and temperature, both of which have to be monitored continuously. For this purpose, a bypass unit is usually employed for filtration and cooling.

The degree of efficiency and the service life of a plant are extremely important for power generation from renewable energy sources: Optimum lubrication prevents wear of moving components and minimizes power losses. This guarantees many years of low-maintenance operation.

Find out more about our products or subsystem:

We would be very happy to offer support for your customized design.

To learn more, please contact our Application Manager – Renewable Energies

Andreas Gruetter

Phone +41 33 672 61 22





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