[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.
What is the response to this argument?
I’m willing to believe either of the following two positions:
1) Don’t be silly, of course generating electricity from wind reduces CO2 emissions.
2) The inefficiency of needing to have gas backup for wind power means that wind ‘leccie generation doesn’t reduce CO2 emissions.
As far as 2) goes I am persuaded that having to have gas plants available, spinning but not producing, to take account of wind variability makes such gas plants less efficient than ones that are operating constantly, or spun up over hours rather than seconds.
But is this enough to make a wind/gas system more emittive than a gas system alone?
And the reason I ask? I’d rather like to have real numbers from disinterested experts. Given that we don’t actually have that, we’ve two sides shouting at each other, what is it that the other side says in response to the above argument?