Although research efforts for the past two decades have led to dramatic reductions in the cost of wind energy, continued incremental improvements to wind turbine performance will lower system costs even further while improving system integration and enhancing technology acceptance.
The Wind Energy Program focuses its cost energy reduction efforts on improving wind turbine components. For example, gearboxes comprise 35% to 40% of the total wind turbine system cost. To help industry identify opportunities for improved gearbox design, the program initiated a long-term industry collaboration. NREL sponsored a drivetrain workshop in 2006 to jointly identify research needs under a multilateral industry-driven test program at the NWTC.
Extending the fatigue life of system components like the drive-train, blades, and tower will play an important role in reducing system costs. As wind turbines become larger and taller, they become more flexible and susceptible to fatigue. To design fatigue-resistant wind turbines, the program is investigating ways to gain better control of the way the components interact and move. Control systems that regulate turbine power and maintain stable closed-loop behavior in the presence of turbulent wind inflow are critical to today’s large wind turbine designs. NREL is developing and testing control systems that maximize energy capture while reducing structural dynamic loads that cause turbine parts to wear out thus increasing the cost of operation and maintenance.
To better understand improvement opportunities for wind turbine availability, SNL hosted a Wind Turbine Reliability Workshop in Albuquerque, New Mexico in October, 2006. More than 90 partici-pants, representing wind farms, service companies, consultants, manufacturers, universities, and laboratories listened to presentations on topics ranging from hardware reliability (gearboxes, generators, pitch systems, blades, and condition monitoring) to stakeholder perspectives (owners, operations, maintenance, and user groups). The workshop also addressed planning for the characterization and reduction of operating and maintenance costs, data information sharing, and the establishment of user groups to address pressing common issues. SNL is planning another technical session in September 2007, and is currently working with the American Wind Energy Association (AWEA).
Working Group and others to begin a systematic data collection effort to collect, analyze, and report on issues affecting turbine reliability and availability.
To help increase the performance of wind turbine blades, program researchers have tested new blade designs and materials at NREL’s NWTC for the past decade using fatigue and static strength tests.
However, the rapid growth in wind turbine size has recently out-stripped the capacity of the blade test facilities. In 2006, the program announced a CRADA seeking partners to design, construct, and assist in operating wind turbine blade test facilities capable of testing blades up to at least 70 m (230 ft) in length. The Wind Energy Program will contribute capital equipment and provide NREL staff and expertise to help develop and operate the facility. Massachusetts and Texas were chosen as the two finalists from six applications. The partners in Massachusetts include the Massachusetts Technology Collaborative, the University of Massachusetts, and the Massachusetts Executive Office of Economic Development. In Texas, the Lone Star Wind Alliance, led by the University of Houston and the Texas General Land Office, is partnering with Texas A&M University, Texas Tech University, University of Texas-Austin, West Texas A&M University, Montana State University, Stanford University, New Mexico State University, Old Dominion University, and the Houston Advanced Research Center.
Distributed wind systems have been traditionally defined as wind turbines rated at 100 kW or less installed at remote locations. The Wind Energy Program has supported efforts to increase the reliability and performance of distributed wind turbines with a goal of produc-ing electricity at between 10 and 15 cents/kWh in a Class 3 wind resource (5.3 m/s at 10 m) by 2007. As achievement of the program’s distributed wind technology (DWT) goal draws near, the program is expanding its activities and its definition for distributed applications to include wind turbines that are installed remotely or connected to the grid at the distribution system, including behind the customer meters. An independent assessment of the various segments of the distributed wind market is in progress.
The program is also continuing its efforts to increase the performance and reliability of small wind turbines. In 2007, the program will launch an effort to establish a small turbine testing and certification program. The program will partner with industry to test a number of small turbines to International Electrotechnical Commission (IEC) and draft AWEA standards. The project will provide high-quality, detailed, and independent test results and allow small businesses the opportunity to earn a certification granted by an independent certification body. The certification body is in the process of being formed by the Interstate Renewable Energy Council (IREC)—the Small Wind Certification Corporation.