UPDATE: The Inhaber Graph curve is discussed in 2015. Later work shows this curve may be too pessimistic, though the shape of it is largely correct, the numbers are not quite this dismal.
One windfarm: bad; ten windfarms: useless.
If we replace 5% of the power grid with windpower we could reduce our CO2 emissions by 4% or so. (If only there was some point to doing that.)
But here’s the non-linearity trap for the fans of green energy. If we replace 20% of the power grid with wind power, we don’t get a 16% reduction in CO2 emissions: we get about 2% reduction (give or take a lot). Indeed if we use enough windpower we might even increase CO2 emissions. Yes Coal + Wind = more CO2. Oh the irony. Quick, can someone email Julia Gillard?
A review of wind power’s success in reducing emissions of CO2 shows the folly of pretending that successful small wind and solar power units can be upscaled to replace a large part of our electricity grid. The major difference between a coal-burning future and a “clean technology” one turns out to have nothing to do with CO2 — instead, in a coal burning future it’s impossible to waste this much money.
The Gillard Carbon Tax plan very much pretends that Australia can “convert” to wind and solar, but a new review by Herbert Inhaber shows the big gains in cutting emissions with these technologies only applies to the first few percentage points of power generated.
How can this be, I hear you ask? The problem is that because wind and solar are so variable — promising one hour, lousy the next — we need to run the conventional power generators and cycle their output up or down to smooth out the bumps. Inhaber compares the efficiency of power generation to mileage for driving a car in the city versus the country. Major generators are efficient when operating at a steady continuous rate. Starting and stopping these mammoth industrial machines is a bit like starting and stopping a car in city traffic (only with a lot times more horsepower). With city-driving we use a lot more fuel to cover the same distance. And windpower is the tool that converts good country-mileage power stations into sloppy city-mileage ones.
In other words, all the CO2 savings the alternative generators promise us are used up by the reduction in efficiency of our large industrial baseline generators that have to be kept spinning due to the intermittent nature of the wind.
Inhaber’s paper is unfortunately behind a paywall, so I can only link to the abstract of “Why wind power does not deliver the expected emissions reductions”.
He compares German and Danish windfarms with experiences in Colorado and Texas as well as Ireland and Estonia.
3.4. E.On Netz report
By the end of 2004, Germany had an installed wind farm capacity
of over 16,000MW. This made Germany the world’s leader in total
wind energy capacity . This utility managed one third of the
world’s wind energy at that point, and thus had more experience
with this energy form than any other.
They conclude (Summary),
. . .traditional power stations with capacities equal to 90% of the
installed wind power capacity must be permanently online in
order to guarantee power supply at all times.
This implies that any carbon dioxide reduction would be at most
10%. The report goes on to say that based on the projected increase
in German wind energy, the relative contribution of wind to guaranteed
capacity will drop to 4%, implying a decrease in carbon
dioxide of about the same percentage
Windfarms can increase real pollution — sulphur dioxide and NOX. Hip Hooray.
3.6. Bentek: Colorado
Bentek  took a different approach in studying emissions in
Colorado. The process by which generation is ramped up and down
at a plant due to wind or any other factor is called cycling (p. 23).
[Coal] cycling makes coal generating units operate much less
efficiently. . .so inefficiently, that these units produce significantly
greater emissions (p. 1).
…incidence of coal cycling is common and has risen sharply since
introduction of wind generation, and in 2008 and 2009 the result
has been significantly greater emissions of SO2, NOX and CO2
than would have occurred if the coal units had not been cycled.
The Review Paper:
Renewable and Sustainable Energy Reviews, volume 15, pages 2557–2562 (2011), “Why wind power does not deliver the expected emissions reductions”, by Herbert Inhaber.
 Bentek Energy LLC. How less became more: wind, power and unintended consequences
in the Colorado energy market. Evergreen, CO: Bentek Energy LLC;
April 16, 2010.
 E.On Netz GmbH. Wind report 2005. Bayreuth, Germany: E.On Netz GmbH;
… he has published, over 150 papers, articles, book chapters, and reviews in such journals and publications as Science, Nature, Philosophical Transactions of the Royal Society, Risk Analysis, Risk Abstracts, Risk Management Quarterly, Annals of Nuclear Energy, Transactions of the American Nuclear Society, Transactions of American Society of Mechanical Engineering, Atmospheric Environment, Journal of Japanese Atomic Industrial Forum, Kerntechnik (Germany), Hazardous Waste Management, Journal of Hazardous Materials, Environmental Science and Technology and Technology Review. His work has been cited over 1070 times in technical literature, including over 280 books and monographs. Authored eight books: “Energy Risk Analysis”; “Slaying the NIMBY Dragon” (on siting undesirable facilities); “Why Energy Conservation Fails”; “Physics of the Environment”; “Environmental Indices”, others. He has published 200 newspaper columns.
UPDATE: From comments
TonyfromOz points out that CO2 emissions are rising in the US — even faster than the power output. “While overall total power consumption for the year increased by 4.3%, CO2 emissions increased by 6.7%.”
More Renewable Power Leads To An Increase In Carbon Dioxide Emissions
Wind energy in Germany is even worse than Jo says. The spinning reserve coal fired power stations cannot run steadily so there is a major hit to their efficiency. So much so that if you turned off all of Germany’s wind turbines their net CO2 emissions would likely go down significantly. Going to gas turbines does not help either, as ‘rapidly reacting open-cycle gas turbines’ only achieve 30% efficiency compared to a steadily running 55% for a coal plant. Thanks to Bruce of Newcastle http://www.wind-watch.org/documents/hidden-fuel-costs-of-wind-generated-electricity/
“A carbon price of around $2,500 per tonne would be needed for wind power to reach 20% penetration. The Renewable Energy Target is 20% renewables by 2020 and most of this is expected to be provided by wind power. Therefore, the expected initial carbon price of about $25 per tonne would have to increase by a factor of one hundred to achieve the Renewable Energy Target.” http://bravenewclimate.com/2011/05/21/co2-avoidance-cost-wind/ Thanks to Chris Y.
Wind power variability in Germany ranged from 0.2% of the grid to 38%. Inhaber also used this graph from the .E.ON Wind Report report which was posted on this Wind-watch page. (h/t Bruce of Newcastle). This is the killer variability that dooms large scale windpower.