Irish Wind Farms Operate at 25% Capacity
Whenever someone puts up a wind farm they talk about the huge amounts of power it will be generating - usually in the range of hundreds of megawatts. But as every engineer knows, this is only "nameplate capacity," the theoretical output that would occur if the wind were blowing all the time. In fact, it usually blows less than 30 percent of the time.
All forms of electrical generation have a capacity factor that is below their nameplate capacity. Coal plants operate at about 80 percent of capacity, nuclear at above 90 percent, hydroelectric dams around 50 percent because of low water levels and seasonal limitations. But wind and solar are generally at the bottom, in the 20-30 percent range.
When Irish Energy Minister Pat Rabbitte recently announced that wind energy had provided Ireland with 42 percent of its electricity on one windy night, The Journal, an Irish newspaper, decided to do a little investigating. What it found is expressed in the above graph.
Wind's overall capacity in Ireland is 2000 megawatts and it has hit peak levels as high as 1700 MW, near 85 percent of nameplate capacity. But the overall output averaged over a year is barely 500 MW, 25 percent of capacity. Moreover the really interesting thing is although output has risen with increased construction over the past two years, overall output has barely budged. This may be because wind patterns do not differ than much across the relatively small island or that once the best wind sites are taken new construction begins to show diminishing returns.