Friday, February 18, 2005

Another annual time vs. output curve

Here is a variation from Denmark on the infeed curves shown earlier this month from Ireland and Germany.

It shows the number of hours during which total infeed from Denmark's 2,374 MW of installed wind-generating capacity in 2003 was within each indicated range. The note (by Mike Hall, as presented at the Views of Scotland conference, January 15, 2005) adds the first three columns (3,250 + 1,750 + 1,000 = 6,000 hours, or 68% of the year) to state that for this amount of time (i.e., two-thirds of the year) the total infeed was not more than 600 MW, about one-fourth of the capacity.

Denmark's average wind-generation output in 2003 was 19% of capacity, or 451 MW. Drawing a curve over the graph allows us to guess that total output was 401-451 MW for 1,200 hours. Adding that to the first two columns shows that for 71%, more than two-thirds, of the time output was below the annual average. Again, that is exactly what the infeed graph from Germany shows: Wind plants produce power at or above their annual average only one-third of the time.