Building better blades

Researchers at Purdue University and Sandia National Laboratories have developed a technique that uses sensors and software to constantly monitor forces exerted on wind turbine blades, thereby improving wind mill efficiency by adjusting for changing wind conditions.

“The ultimate goal is to feed information from sensors into an active control system that precisely adjusts components to optimize efficiency” Purdue doctoral student Jonathan White said in a statement.

White is leading the research with Douglas Adams, a professor of mechanical engineering and director of Purdue’s Center for Systems Integrity.

“Wind energy is playing an increasing role in providing electrical power,” Adams noted in the statement. “The United States is now the largest harvester of wind energy in the world. The question is, what can be done to wind turbines to make them more efficient, more cost effective and more reliable?”

The engineers embedded sensors called uniaxial and triaxial accelerometers inside a wind turbine blade as the blade was being built. The blade is being tested at the U.S. Department of Agriculture’s Agriculture Research Service laboratory in Bushland, Texas.

According to the press release, the sensors could be instrumental in future turbine blades that have “control surfaces” and simple flaps like those on an airplane’s wings to change the aerodynamic characteristics of the blades for better control. Research findings show that using a trio of sensors and “estimator model” software developed by White accurately reveals how much force is being exerted on the blades. Purdue and Sandia have applied for a provisional patent on the technique.

Some other facts and finding of the Purdue/Sandia release include:

A wind turbine’s major components include rotor blades, a gearbox and generator. The wind turbine blades are made primarily of fiberglass and balsa wood and occasionally are strengthened with carbon fiber.

Sensor data in a smart system might be used to better control the turbine speed by automatically adjusting the blade pitch while also commanding the generator to take corrective steps. Sensor data also will be used to design more resilient blades.

The sensors measure two types of acceleration. One type, the dynamic acceleration, results from gusting winds, while the other, called static acceleration, results from gravity and the steady background winds.

The research is ongoing, and the engineers are now pursuing the application of their system to advanced, next-generation turbine blades that are more curved than conventional blades. This more complex shape makes it more challenging to apply the technique.

In 2008 the United States added 8,358 megawatts of new wind-power capacity, which equates to thousands of new turbines since the average wind turbine generates 1.5 megawatts. The new capacity increased the total U.S. installed wind power to 25,170 megawatts, surpassing Germany’s capacity as the world’s largest harvester of wind power.