Similar to the leaked report from Germany (see earlier post) a study published last year by the Irish grid manager (172-KB PDF) found the benefits of wind-generated power to be small and that they decreased as more wind power was added to the system and as the system as a whole grew. Their model assumed that all energy produced from wind facilities would be used and did not consider less than hourly output fluctuations -- quite generous assumptions.
Three problems they described that mitigate the benefits of wind power were the large amount of extra energy required to start up thermal generators that would otherwise never have been turned off, the mechanical stresses of more frequent ramping of production levels up and down, and the increased prices of energy necessary to pay for any lower usage of thermal plants. They noticed that there was very little possibility of closing any non-wind facilities, because their capacity would still be needed to respond to periods of peak demand. So wind plants add more capacity (requiring more infrastructure) with almost no reduction of non-wind capacity, the latter of which must be used more inefficiently than otherwise.
As for CO2 reduction -- the primary argument for wind-generated power -- the study concludes, "The cost of CO2 abatement arising from using large levels of wind energy penetration appears high relative to other alternatives."
