Since wind energy on its own is not capable of delivering a reliable supply of electricity it can never be a substitute for large, centralized power stations.
The force of the wind generally fluctuates considerably within the space of a few days and even a few hours. Sometimes the wind can drop just when the demand for electricity is at its peak. The following graph, which documents the amount of electricity generated during the month of November in 2001, illustrates this point well.
The graph clearly shows that wind energy on its own is not capable of providing a reliable supply of electricity. Coal-and gas-fired power stations are required to smooth out the fluctuations in wind power output and need to be ramped up and down constantly as wind power output fluctuates. This shortens their service life and causes them to consume more fuel-in much the same way as a car in city traffic. The higher specific fuel consumption produces higher emission levels, thereby negating some of the environmental benefit of wind power.
The wind does not blow constantly, with the result that wind turbines have a very low capacity factor.
By contrast, coal-fired power stations can generate at 100 percent of their rated capacity at all times apart from when they are shut down for routine maintenance. That’s anything up to 8000 full-load hours a year, depending on the load band they are operated in. By contrast, wind turbines achieve only around 1,800 full-load hours a year. They are therefore economically unviable without subsidies.
In Germany, the Renewable Energy Law (EEG) provides that operators of wind turbines can charge feed-in tariffs of about 9 eurocents per kilowatt-hour-about three times the amount charged for power generated by coal-fired or nuclear power stations. As a result of these high subsidies, wind turbines are now appearing in unviable, low-wind regions, as high-wind sites have been fully developed. Wind-turbine subsidies should be limited to those geographic areas that are high in wind potential.
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