NSK, Motion & Control
Bearing News
30/11/2009
Rolling bearings for micro wind turbines
Wind power technology is on the rise, with annual growth rates of 20% predicted for 2009 to 2014. In addition to the trend towards ever larger multi megawatt turbines, there is also a market (so far almost unknown to the general public) for micro wind turbines producing less than 1 kW for decentralised energy supplies e.g. for sailing boots, telephone installations and parking ticket machines. With these turbines, wind technology is conquering new application fields. NSK offers rolling bearings designed for these micro turbines: following consultation with engineers from NSK’s Wind Energy business unit, micro turbine providers save €337.000 annually and offer their turbines at a greatly reduced price. In addition to the economic benefits, the NSK rolling bearings feature a longer life span.
One of the main trends within the rapidly increasing wind turbine market is that turbine output is continuously on the increase. Just a few years ago, a 1 MW turbine would have ranked as the highest output category. In the meantime, turbines delivering some 5 MW have been installed, while the development divisions of wind technology manufacturers are working on even larger turbines.
However, developments in the opposite direction should not be overlooked: decentralised micro wind turbines with outputs of up to 500 W can generate electricity, for example, in areas with poor infrastructure or can supply energy to telephone installations. While this is not a new technology, it has so far been reserved for power generation on sailing boats.
These turbines must be highly reliable, highly efficient and available at a very economical price. This price sensitivity posed a particular challenge to a manufacturer of turbines who was planning mass production of micro wind turbines. Bringing the project from development stage to mass production with a planned annual volume of 20,000 wind turbines was hampered by the high costs of installing four rolling bearings per turbine. It was planned to use two 17 mm standard ball bearings with a standard lubrication system for the main drive, and one 17 mm and one 20 mm bearing in the yaw drive (that moves the nacelle and thus correctly aligns the rotor blades towards the wind).
The manufacturer asked the project engineers at NSK’s Wind Energy business division to come up with an alternative proposal for these bearings. NSK first developed a technical solution that retained the bearing construction and took account of the very long life span required by wind turbines. The engineers suggested using a special “longlife” lubricant developed by NSK for all four sealed ball bearings.
Once the rolling bearings had been configured and selected, the calculations were drawn up. The customer was surprised by the result: NSK’s solution offered a saving of precisely 73%. Consequently the manufacturer of the wind turbine only had to factor in 27% of the originally calculated rolling bearing costs. This amounted to an overall reduction in cost of €337.600 and improved their market opportunities because the turbines could be offered at a lower price.
Not surprisingly, the manufacturer implemented NSK’s solution. It now uses NSK bearings for its innovative micro wind turbines. An additional bonus is the longer lifespan of the bearings.
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