Renewable energy will be the world’s fastest-growing source of electricity generation over the next two decades, although it will still make up a relatively minor portion of the global energy supply, according to the Energy Information Administration. The majority of that increase will come from the use of wind power and water power, or hydropower. The Obama Administration advocates a policy that would require 25% of United States electricity demand be met by renewable energy by 2025.

But wood, coal, and oil continue to be the primary fuels that provide energy for the majority of human activities. Alternative technologies that utilize the natural energy sources of the Earth — such as wind, water, and the Sun — continue to make progress.

Building a Better Wind Turbine

Purdue doctoral student Jonathan White holds a cross-section of a wind turbine blade like the one used in research to improve the efficiency of turbines.
The U.S. now has with the world’s largest installed base of wind power, according to the World Wind Energy Association. More than 8,300 megawatts of wind power were installed in 2008, expanding the nation’s total windpower- generating capacity by 50 percent in a single year. As part of the economic stimulus plan signed in February, President Obama extended tax credits for wind and increased the amount the government will spend on those credits by 30 percent.

Wind turbines convert the kinetic energy of the wind into mechanical energy, and then into electricity. A turbine is generally made up of rotor blades, a gearbox, and generator. Because wind speeds fluctuate, operating the generator and the turbine in the most efficient way is difficult. Engineers at Purdue University and Sandia National Laboratories have developed a technique that uses sensors and computational software to constantly monitor forces exerted on wind turbine blades, which are made primarily of fiberglass and balsa wood.

The engineers embedded sensors called uniaxial and triaxial accelerometers inside a wind turbine blade as the blade was being built. The sensors measure two types of acceleration. One type, dynamic acceleration, results from gusting winds, while the other, called static acceleration, results from gravity and the steady background winds. Accurate measurement of both forms of acceleration is essential to estimate forces exerted on the blades. 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.

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