A new research study by consultancy IntelStor looks at cost and performance benchmarking for turbine drivetrains that are 10MW and above. Five types of drivetrain configurations were evaluated based on an exhaustive search of over 900 patents to uncover the evolution of designs and the current state of the art.
The five drivetrain configurations currently in use today include 1, 2, and 3 stage gearboxes as well as axial and radial direct drive arrangements. FEA analysis for sizing optimization combined with current commodity cost analysis and performance benchmarking reveal that the optimized drivetrain configuration from the standpoint of lowest part count, lowest tower head mass, lowest CapEx as well as O&M cost is a single stage gearbox and low speed generator of about 90 – 100rpm. This architecture has a system efficiency only 0.3% lower than a radial direct drive architecture, but it currently represents a very small percentage of the designs being proposed for large turbines. Direct drive has the best overall system efficiency for drivetrains at or above 10MW, but is ultimately more expensive than having at least one reduction stage. O&M cost of direct drive is also a concern for large air gap diameters required for higher rated systems due to ease of service and a higher part count.