An increasing number of wind turbines are being installed worldwide. The success of wind power means that the productivity of wind turbines is gaining in importance. Schaeffler is making its contribution by providing reliable components and a comprehensive range of services
Records & Record Marks
The wind year 2015 began with a new record. The wind turbines installed in Germany produced 9,776 gigawatt hours of power during January, the largest amount ever produced in a single month. This amount of power is equal to the production of twelve nuclear power plants operated at full power round the clock. The new record is due to the consistent expansion of wind power, which also reached a new record mark in the previous year. According to information from the Germany Engineering Federation VDMA, new wind turbines with a total output of 4.8 gigawatt were installed on shore alone in 2014. This is in addition to the number of new wind turbines installed off shore, which was significantly less than on land. All the offshore wind turbines had a combined output of more than one gigawatt for the first time at the end of 2014.
Global Player in Wind Power
Today, Schaeffler is a global player, which offers the right solution for every bearing position in wind turbines. The company not only has manufacturing capacity in China. It also has a team in Anting near Shanghai, which develops wind power components specially for local customers. In the USA and India, large-size bearings are also manufactured for the relevant markets.
The development in the markets has not been uniform: The two-megawatt class dominates internationally with correspondingly high quantities. In contrast, there is a trend towards higher outputs in Europe. For example, the average output of the wind turbines installed in Germany in 2014 was 2.7 megawatts. This means that rotor diameters are increasing: The average is currently 99 meters. In comparison, the Airbus A380 has a wingspan of only 80 meters. However, this is not the end of the line. At the beginning of 2014, the first prototype of an offshore wind turbine from MHI Vestas was put into operation in Denmark. The peak output of eight megawatts is achieved with a rotor diameter of 164 meters.
Cost-effective Wind Turbines Require Reliable Components
The power from today’s wind turbines must satisfy economic criteria - a decisive difference to the pioneering days. Schaeffler’s customers, i.e. wind turbine and gearbox manufacturers, are facing strong, global competition. Therefore, the operating life costs of wind turbines are becoming increasingly important. These are mainly dependent on three factors: the investment costs, overall efficiency and reliability throughout the entire operating life, which must be a minimum of 20 years.
In view of the large quantities of steel that are installed in a wind turbine, it is essential to save material or increase the power density in order to reduce investment costs. For Schaeffler, this primarily means offering solutions which enable downsizing.
A decisive factor for the economic balance of a wind turbine is the number of achievable operating hours. Downtimes must be prevented. Furthermore, repairs are very expensive, particularly on offshore wind turbines. If a gearbox fails due to bearing damage at sea, the operator will be faced with repair costs of at least one million euros. Today, reliability is a decisive differentiation criterion for wind turbine manufacturers - regardless of whether on land or in the sea.
With the Schaeffler Wind Power Standard (WPOS), the highest quality standard for products and processes, Schaeffler ensures optimum quality and reliability worldwide and is offering the same high standards of quality as it is already successfully offering in the automotive, aviation and aerospace industries.
Rotors with increasingly large diameters mean that the loads acting on the rotor shaft are also increasing significantly. Schaeffler offers relevant customer-specific solutions depending on the design of the wind turbine.
FAG spherical roller bearings are suitable for extremely high loads and can compensate for alignment errors and shaft deflections. Schaeffler has consistently developed this proven bearing solution for main rotor shaft bearing supports according to customer requirements in order to increase robustness and service life even further.
There is a trend towards direct bearing supports in gearboxes. Schaeffler has developed a high-capacity cylindrical roller bearing for this application. Due to the particularly streamlined design of the cage, the FAG high-capacity cylindrical roller bearing combines the advantages of full complement bearings with those of cage bearings. As a direct bearing, it allows an optimum utilization of the installation space.
Generator bearings are subject to electrical currents, which can cause damage. Schaeffler offers current-insulated bearings to prevent damage due to the passage of electrical current.
From Multi-body Simulation to Large-size Bearing Test Rig
When designing these bearings it is important that the load carrying capacity is ensured under all conditions without "overspecifying" – i.e. installing levels of safety that are unnecessary. In addition to its extensive experience in the wind power business, Schaeffler also uses relevant development tools in the design process. A complete wind turbine including the detailed drive train can therefore be tested using multi-body simulation before the first prototype is built. Schaeffler specialists can subsequently check if their calculations were correct on the large-size bearing test rig "Astraios" in Schweinfurt. This test rig is used to test bearings with a diameter of up to 3.5 meters for wind turbines with a peak output of up to six megawatts.
ASTRAIOS simulates the real loads and moments that occur in a wind turbine. More than 300 sensors in the test bearings supply information that is evaluated for various analyses.
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