Wind Power Innovation Enables Shift to Utility-Scale
NREL scientists are confident that continued research will enable wind energy to make major contributions to meeting the nation's electrical demand.
In the 1930s, a farmer in South Dakota built a small wind turbine on his farm, generating enough electricity to power his radio. He never dreamed that it might be possible one day for his descendants to have multi-megawatt wind turbines on the farm towering several hundred feet above his barn and generating enough electricity to power thousands of homes.
In the '70s and '80s, with the advent of the first small wind farms in California, many members in the power industry thought wind power was an interesting concept. They never dreamed the technology would one day become the fastest growing electricity resource in the world.
When the scientists at NREL began conducting wind energy research in the late '80s and early '90s, they knew that innovation born from research could make a significant difference in the technology's advancement and industry growth.
For the next two decades, they worked diligently with industry partners developing and testing innovations that would lower the cost of wind energy and increase production and reliability. These innovations included more aerodynamic designs for airfoils, permanent-magnet direct-drive drivetrains, state-of-the-art control systems, and stronger lighter-weight materials and design codes.
Today that farm in South Dakota is home to seven 1.5-megawatt (MW) turbines capable of powering about 2,600 homes. And by the end of 2010, U.S. wind energy capacity topped 40,000 MW (enough to power about 10 million homes), was cost-competitive in many areas, and was the fastest growing energy industry in the nation.
Although 40,000 MW sounds like a lot of electricity, it represents about 2% of our nation's electricity demand. But the scientists at NREL are confident that with continued research, wind energy can contribute much more.
State-of-the-Art Test Facilities
When NREL first started conducting wind energy research in the 1980s on a site just south of Boulder, Colorado, its test facility consisted of a few small wind turbines and an office building. Most people driving by didn't even notice it was there. In 1994, NREL completed construction on a 2.5-MW dynamometer test facility and the U.S. Department of Energy (DOE) dedicated the site as a National Wind Technology Test Center (NWTC).
Since then, the facility has continued to grow and increase its research and development capabilities. In addition to the 2.5-MW dynamometer, the site now hosts three multi-megawatt test turbines that feed power into the electric grid. These generating giants make it easy to spot the site from more than 20 miles away. The NWTC is also home to two 600-kW advanced research turbines, numerous small wind energy test turbines, and a structural testing laboratory capable of testing wind turbine blades up to 50 meters in length.
Today, NREL's test facility is one of a select few in the United States accredited through the American Association of Laboratory Accreditation to perform the tests required by turbine certification agencies, financial institutions, and other organizations. Certification testing validates the performance of new wind turbine designs and paves the way for manufacturers to begin commercial production.
Utility-Scale Turbine Development
For more than two decades, NREL has worked with industry partners such as General Electric (GE) Wind Energy, Clipper Windpower, Siemens, and Vestas to improve the performance of utility-scale wind turbines. NREL's work with GE Wind and its predecessors contributed to the design and commercial production of GE's 1.5-MW commercial wind turbine now operating in wind farms worldwide.
In 2009, DOE purchased a GE 1.5-MW wind turbine and installed it at the NWTC for long-term research and testing. Data collected from this turbine will lead to increased reliability and performance of current and future wind turbines, helping achieve the aspiration of supplying 20% of the nation's electricity from wind energy by 2030. Planned areas of research include the turbine's aerodynamic design, the effects of turbulence on its structural loads and performance, and how the combination of these factors may affect wind plant performance.
A competitive solicitation issued by NREL resulted in the signing of a cooperative research and development agreement (CRADA) with Siemens to install and test a 2.3-MW utility-scale wind turbine at the NWTC in 2009. The Siemens' project is the largest government-industry research partnership for wind power generation ever undertaken in the United States. The purpose of the multi-year CRADA is to increase the performance and reliability of future wind turbine designs by studying the performance and aerodynamics of this new class of large, land-based machines. Areas of research include structural and performance testing; modal, acoustics, and power quality testing; aerodynamic testing; and turbine performance enhancements.
NREL installed its third multi-megawatt wind turbine, an Alstom 3-MW ECO 100, at the NWTC in 2010. Under a Work for Others Agreement with Alstom, NREL is testing the company's new 60-Hz model to finalize the International Electrotechnical Commission requirements for type certification. The successful outcome of this test will enable Alstom to begin commercial production of the ECO 100 in the United States. Philippe Cochet, senior vice president of Alstom Power's Wind and Hydro business divisions, said, "NREL is a well-respected authority on technical issues related to wind energy and the renewable energy market in general. Having their input and validation will give our customers confidence that our equipment is fully suited to the particular characteristics of the U.S. wind energy market."
Increasing Gearbox Reliability
Gearbox reliability is an ongoing challenge for the wind energy industry. Gearbox failures require expensive and time-consuming replacement, significantly increasing the cost of wind plant operation while reducing power output and revenue. In an effort to increase gearbox reliability, NREL launched a Gearbox Reliability Collaborative (GRC) in 2007 that brought together the world's leading turbine manufacturers, consultants, and experts from more than 30 companies and organizations.
The goal of the GRC is to validate the typical design process—from the wind turbine system loads to bearing rating—through a comprehensive dynamometer and field-test program on extensively instrumented gearboxes. This design analysis will identify gaps in the design process to improve reliability of future designs and retrofit packages.
Since the GRC was launched, it has tested two nonproprietary gearbox designs on NREL's 2.5-MW dynamometer test bed and in the field. Data collected from the nonproprietary gearbox testing will be made publicly available, which is an unprecedented resource for industry. Gearbox modelers will be able to use the data for analyses and complex model validations. The data will also be used to better define gearbox design processes and to validate predicted fatigue loading.
The long-term research conducted on the Alstom turbine is aligned with the GRC objectives to increase gearbox reliability. During the first phase of the study, NREL will build its own model of the Alstom wind turbine using the lab's design code. NREL will then compare its model to Alstom's model and to field measurements to identify and understand any design code shortcomings. This will enable NREL to better predict wind turbine loads and advance its design and analysis tools, which are made available to the wind industry. By providing industry with state-of-the-art design codes, NREL is helping to develop advanced, more reliable wind turbine technology.
For NREL, the opportunity to study Alstom's new drivetrain configuration may lead to innovative approaches to mitigate loads that reduce gearbox reliability and will validate simulation models for improving future designs. For Alstom, the long-term research at the NWTC will provide the company with an opportunity to test the machine's durability under the extreme wind conditions often experienced at the site and the tests will validate its performance on the U.S. grid, ensuring its successful entry into the U.S. market.
Learn more about wind energy research at NREL.
Photo credits: Dennis Schroeder