Success Story

More Reliable Gearboxes Help Reduce the Cost of Wind Power

Gearbox failures have a significant impact on the cost of wind farm operations. To help minimize gearbox failures, in 2007 the National Renewable Energy Laboratory (NREL) initiated the Gearbox Reliability Collaborative (GRC), which consists of wind energy manufacturers, project owners, researchers, and consultants.

Gearbox deficiencies are the result of many factors, and the GRC team recommends efficient and costeffective improvements in order to expand the industry knowledge base and facilitate immediate improvements in the gearbox life cycle. The GRC combines analysis, field testing, dynamometer testing, condition monitoring, and the creation of a gearbox failure database.

NREL and other GRC partners have been able to develop improved processes for the design, testing, and operation of wind turbines to increase gearbox reliability. In contrast to private investigations of these problems, the GRC quickly shares its models, data, and findings among its participants, including many wind turbine manufacturers and equipment suppliers. Ultimately, the findings are made public for use throughout the wind industry. This knowledge is resulting in increased gearbox reliability and an overall reduction in the cost of wind energy.

The GRC started with a representative gearbox design, which was then redesigned to the best industry standards as of 2007. Two heavily instrumented gearboxes were built based on this design. One was mounted in a wind turbine and tested in the field, while the other was tested on a dynamometer, which simulates the loads experienced by a typical wind turbine, but on a compressed time scale. This effort built an understanding of how selected turbine loads and operational events translate into bearing and gear responses.

Based on all the lessons learned from the past five years, the GRC has now produced a new and improved design, which is projected to yield an operating lifetime of 12 years, more than triple that of the previous redesigned gearbox. This new design, shown in the illustration below, will be built and tested in the same way as the previous iteration, and again, all results will be shared first with the GRC members and eventually made public.