Unexpected Carbon Dioxide Emissions From Wind Power

One law  that you can't avoid is the  Law of Unintended Consequences.  Bishop Hill (aka Andrew Montford) recently offered a blog post with the intriguing suggestion that the combination of wind power and intermittent  gas-fired back up (which is necessary if the lights aren't to go out when the wind stops blowing)  result in more carbon dioxide emissions than steady production of power through combined cycle gas turbines, or CCGTs.  The explanation is that CCGTs are much more efficient than standard gas turbines when run continuously, but the secondary power generation from the heat exchangers that contributes to their efficiency  takes too long to fire up, and therefore CCGTs can't be used  effectively as auxiliary power when the wind drops.  Here is how it was explained in one of his posts last month.:

[A]s wind rarely produces more than 25% of its faceplate capacity it needs 75% backup - which due to the necessity of fast response times needs OCGT generation (CCGT can respond quickly but the heat-exchanger systems upon which their increased efficiency relies, cannot - so CCGT behaves like OCGT under these circumstances). CCGT produces 0.4 tonnes of CO2 per MWh, OCGT produces 0.6 tonnes. Thus 0.6 tonnes x 75% = 0.45 tonnes. Conclusion: Wind + OCGT backup produces more 0.05 tonnes of CO2 per MWh than continuous CCGT.

Here is where it came from originally, and there are some interesting comments  at that blog.

All this came to mind this morning when I  read  George Hohmann's piece in the September 24 Daily Mail about wind power in West Virginia.  There's a real question as to whether wind power can survive without subsidies, and one of the primary justifications for subsidizing wind power is to cut carbon emissions.  It looks like that may not be the case.