Up Time Magazine - February/March 2009 - (Page 54) vibration upload Blowin’ in the Wind Vibration Analysis of Wind Turbines by Jason Tranter W ind turbines are dotted across the countryside, seaside, and even offshore. Many believe they are the answer to global warming and stopping the reduction of fossil fuel reserves. Whether you enjoy seeing them on the horizon, majestically spinning in the breeze, or believe they disturb the previously unspoiled landscape, for all of us in the reliability and condition monitoring fields, they pose a new challenge – we have to keep them turning! generated “just over 1.5% of U.S. electricity supply, powering the equivalent of over 5.7 million homes”. It also states that “to generate the same amount of electricity using the average U.S. power plant fuel mix would cause over 28 million tons of carbon dioxide (CO2) to be emitted annually”5. The U.S. is now the world leader in wind electricity generation. While Germany still has more generating capacity installed (about 23,000 megawatts), the U.S. is producing more electricity from wind because of its much stronger winds5. With Government assistance, a continuing threat of global warming, and growing demand for power, we are sure to see an increase in the number of wind turbines around the world. Wind Energy Around the World Almost wherever you go in the world you will now find wind turbines. Whereas they were once smaller, generating less than 250 kW, with blade diameters of up to 35 meters, now wind turbines are being developed up to 7.5 MW, with rotor diameters of over 100 meters! Whereas once they represented a fraction of a percent of total power generation, they now represent a far more significant proportion, with legislation in place to greatly increase that amount in coming years. Figure 1 - The size of wind turbines has continued to grow, with some now over 100 meters in diameter. A Brief Guide to the Operation of a Wind Turbine Wind turbines are remarkable machines. They are designed to operate, unmanned, in very windy locations; typically in remote farmland or at sea. As the wind blows, the yaw control points the blades into the wind, and the pitch of the blades is constantly varied to control the speed. Typically two large bearings support the main shaft driven by the blades. A gearbox increases the speed in order to drive the generator at 1800 RPM, for example. In Europe, wind power currently supplies 3.7% of EU electricity demand1. In Denmark, for example, more than 20 percent of electricity is wind-generated. In Spain, the figure is 13 percent and in Germany it is seven percent2. In 2001, the European Union passed legislation setting a target for 21% of the EU’s electricity demand to come from renewable energy by 20103. The United States wind energy industry is growing at an exceptional pace, and that pace will only accelerate in the coming years. Within days of being elected, President Barack Obama announced a new energy plan which includes measures to “create five million new jobs by strategically investing $150 billion over the next ten years to catalyze private efforts to build a clean energy future”4. The plan also includes “an economy-wide capand-trade system to reduce carbon emissions by the amount scientists say is necessary”4. The total installed capacity in the United States is 21,017 MW in 35 states. Over 8,000 MW more are under construction for completion this year or early next year. Over 7,500 MW were installed in 2008, and 5,249 MW were installed in 2007. The American Wind Energy Association (AWEA) stated that in 2008 American wind farms Figure 2 – Cross section of Planetary Gearbox. 54 february/march 2009
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