Engine & Turbine Technology
Cost pressures for wind turbine bearings
Even higher expectations regarding service life and reliability twinned with pressure on costs: this is the picture currently emerging for bearings in the wind energy industry.
Incluso con unas mayores expectativas en relación a la vida útil y a la fiabilidad hermanada con la presión de los costes: actualmente esta es la imagen emergente de los cojinetes en la industria de energía eólica.
Aktuell gehen in der Windenergiebranche immer höhere Erwartungen an die Lebensdauer und Zuverlässigkeit von Lagern mit steigendem Kostendruck einher.
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Fig. 1. NSK always modifies its bearings to cater for the specific application scenario and/or turbine type.
t first sight, the business news from the wind energy industry appears contradictory. Last year, turbines with a total output of 40GW were installed around
the world and the industry is expected to keep growing in the future. In fact, a whole new market is being born with the emergence of offshore technology. At the same time, however, leading manufacturers of wind turbines and suppliers who specialise in wind power are announcing harsh cost-cutting programmes. Experts also expect to see further consolidation amongst suppliers.
Cost pressure
Te explanation for this apparent contradiction is that although the industry is growing, it had anticipated even stronger growth. Tis means that it now has substantial excess capacity. Te result is considerable pressure on prices, which is also affecting suppliers. For one of the world’s leading manufacturers of bearings for wind turbines, this means that research and
development projects must keep striving to meet the industry’s extremely high expectations for bearings’ service life in adverse operating conditions with highly dynamic stress. At the same time, however, the R&D team must take into account the costs associated with any new development or enhancement at an early stage and produce a clear cost-benefit analysis. Where does the greatest potential for
innovation lie? Of course, wind power companies also
welcome innovations which cut costs without compromising on bearings’ reliability. Tis is particularly important as experts agree that the global competition among turbine manufacturers is set to become even more intense in the future. With all this in mind, suppliers have to look
very closely at which areas have the greatest market potential for developing new generations of bearings. NSK has identified multi-megawatt turbines with an output of 2 to 4MW as one such area. Te company is already well positioned in this segment: in recent months, leading manufacturers have presented new turbines equipped with NSK bearings.
Cylindrical roller bearings NSK has already optimised cylindrical roller bearings for the planet wheels of turbines in the 3MW class, running two development projects simultaneously in this field. Te first project aimed to improve the internal design. Without changing the bearing diameter or the number of rollers, the team optimised the micro-geometry’s design and production engineering while keeping the macro-geometry the same – resulting in a 15 per cent increase in the dynamic load rating. Tis leads to a 70 per cent longer calculated service life. As well as being suitable for use in planet wheels, these bearings are ideal for other applications on the ‘fast’ side of the wind turbine gearbox.
Te second project was dedicated to fundamentally redesigning the bearing’s internal construction. Te number of rollers was increased, meaning that the cross section of the cage was reduced. It still has to withstand the same loads, however. Te project team achieved this by optimising the cage’s geometry without impairing
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