In order to assure a constant availability of electricity, a grid needs to be protected against the sudden loss of any power plant. This can occur, for a wind farm, if the wind speed increases beyond acceptable limits. The sudden loss of wind power must be accommodated by the rest of the power plants connected to the grid. They must be available with a spinning reserve to provide this backup power when needed. Of course, this is true for the loss of any type of power plant. But a wind increase may occur suddenly over a large area and shut off all the wind power connected to the grid.Most grid managers would prefer not to have any wind power on the grid, since dealing with even a small amount of wind power is like dodging bullets for electrical grid personnel.
Hydro electric plants and natural gas plants can respond fairly quickly to the sudden loss of another power plant, but as more wind farms are added to the grid, the problem of grid stability gets more severe. Grid stability, therefore, limits the amount of wind energy that can be accommodated by the grid (to roughly 15 percent). _FittingWindOntotheGrid
A typical wind farm would generate electricity about 30 percent of the time, and not necessarily at times when electricity is needed. There is a very big difference between intermittent sources of electricity, such as wind farms, and baseload sources, such as nuclear power. The argument that nuclear power also has down times is true, but these refueling and maintenance outages are largely planned during times of low electricity demand (during spring and fall). _Economics of Wind PowerMost of the time either there is no wind, too little wind to use, or too much wind to safely run the turbine. During the UK's recent spell of super-cold arctic weather, its wind generators provided power less than 5% of the time. Imagine if the UK were even more dependent on wind power than at present. Imagine that to be the case, without nuclear energy from France available as backup, during an extended cold spell of years, decades, or longer.
The capacity factor of the 104 nuclear reactors operating in the United States is 90 percent. In other words, nuclear facilities crank out electricity around the clock, 365 days of the year, at pretty near their total capacity. Compare that to the results of a study from a group of wind power advocates at the University of Delaware that modeled data from off shore meteorological stations from Maine to the Florida Keys. Their results show that a large offshore turbine array would attain a 90 percent capacity factor only 2.2 days a year. Their numbers show that 20,000 five megawatt turbines would be needed to equal the full generating capacity of those 104 reactors. Even 1,200 turbines would not supply electricity as dependably as a new reactor like the one proposed at Calvert Cliffs in Maryland. _BaltimoreChronicleIt sounds as if an advanced nation that allowed itself to become dependent on wind power for its electricity, would experience the same sort of quality of electrical service provision as a typical third world country.
Here are some "levelized cost comparisons" for building various types of power generation plants
If you haven't read John Droz presentation on wind energy, you need to do so ASAP
Ted Rockwell's Energy Facts PDF is also a must-read (PDF)
David Mackay's "Without Hot Air" is another useful quantitative comparison of energy sources
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