Prasad Padman / Control Design Engineer / Moog
A recently released pitch system boasts of 66% fewer parts than the designs installed today on most operating turbines. The new system is also lighter and smaller. As part of its design, its engineering team at Moog also eliminated many problematic components that historically failed at a higher rate than other parts of the pitch system. Using reliability analysis tools commonly applied in the aerospace industry, the design team directly quantified the reliability benefits of the Moog Pitch System 3 based on the system’s configuration.
In late 2016, Moog Inc. launched its next generation of wind turbine pitch-control technology, the Pitch System 3. The first shipment is successfully operating at a wind farm in Brazil. The company improved its earlier pitch-system design to help wind-farm operators and turbine makers meet the growing need to reduce wind farm capital and operating expenses.
Input from DNV GL
It is generally accepted that pitch systems keep a turbine running and ensure its safety in the event of high winds or catastrophic events. Pitch systems monitor and adjust the inclination angle and control the speed of the blades. Although pitch systems play a large role in the safe and the economic operation of a turbine, the devices account for less than three percent of a wind farm’s capital expenditures.
Earlier this year, DNV GL, an international certification body and provider of technical assessments, quantified the impact of pitch-system reliability on turbine failure rates. The organization’s research, in part, examined how innovative designs for advancing pitch-system reliability can improve the Levelized Cost of Energy (LCoE). This figure measures the net cost to install and operate a wind turbine against expected energy output over the course of a turbine’s lifetime.
DNV GL collected data from 69 projects totaling 5.3 GW of capacity across four million turbine days for wind turbines located in China, Europe, and North America. The turbines ranged in size from 1.5 to 3 MW. The organization’s DNV GL benchmarking study confirmed that pitch systems (whether electric or hydraulic) have a high rate of failure and significant effect on turbine reliability, downtime, operating expenses, and LCoE.
A conventional pitch systems on the left and the simpler System 3 by Moog.
A typical pitch system from five years ago (many of which are operating today in wind turbines globally) can have more than 4,000 individual parts. These components are integrated with thousands of wires and termination points, all potential sources of failure.
Industry-wide performance data from the DNV GL study showed that the current installed base of pitch systems manufactured by a number of providers left a lot of room for improvement. Moog engineers recognized that by increasing pitch-system reliability, it was possible to lower a turbine’s cost of energy. By designing a pitch system with less complexity, far fewer parts, and a modular architecture, the reliability of the system would be greatly improved. As a critical sub-system of the wind turbine, the pitch system has a direct impact on the overall turbine lifetime performance.
Reducing complexity to improve productivity
A cross-functional engineering team first considered how a pitch system might be improved in design. Few systems have changed over the last 10 years. Engineers simplified the basic structure by defining the minimum requirements for a high-performance pitch system in a whiteboard design. Then, engineers integrated functions into core modules that the team designed, optimized, and tested for a service life of more than 20 years. This design approach takes into account a wind-turbine operator’s requirements for improved reliability, ease of integration, interface compatibility and reduction in planned and unplanned maintenance in the field.
Reducing maintenance
The wind sector is under extreme pressure to deliver lower LCoE to grid operators. This requires reducing the capital cost per installed megawatt of capacity and increasing the turbine availability during operation.
Delivering lower LCoE requires the industry to reduce planned and unplanned maintenance costs. Wind-turbine maintenance is challenging and costly because of the difficulty in accessing the nacelle and hub, particularly in remote locations such as offshore. The cost of component failures is amplified by the high cost of accessing equipment for repair.
However, reducing maintenance also lowers LCoE. In fact, the DNV GL study shows that lighter, smaller pitch systems can save up to $1.70/MWh for a typical 3.0 MW turbine. By eliminating required planned maintenance and greatly reducing component failures in general, a wind-farm operator directly benefits from higher availability and lower maintenance costs.
Renewable technologies, such as wind power, have an opportunity to shoulder a larger percentage of the world’s energy needs. The mission-critical nature of a country’s energy grid demands better technology than a general-purpose industrial application, such as many pitch systems developed up to this point.
About the author
Mr. Prasad Padman, an instrumentation and control engineer with a master’s degree in finance and marketing, has been with Moog for eight years in various roles. He is currently responsible for developing next-generation pitch control solutions.
Filed Under: News
