In this case, they are projecting from the 2001 experience of 120 MW of on-shore and 60 MW of off-shore wind power showing a combined annual average output of 37.4% capacity. Notice that with the higher capacity factor the curve flattens, bearing out the prediction of the previous post.
In this case the average level (175 MW) is at about 3,750 hours, or 2/5 rather than 1/3 of the year. But the projection is based on hourly averages only, which they admit makes the performance of the wind plant appear better. So it is likely that actual experience would shift the middle of the curve left, i.e., towards showing output at or above the annual average only 1/3 of the time.
