The graphic is from a writeup of a calculation which indicates that CO2 emissions reductions associated with wind power were 0.279 tCO2/MWh for the Irish electricity grid in 2011. Wind power met 17% of electricity demand that year. Such savings are a lot lower than have usually been assumed. Most grid operators do not publish official numbers on the effectiveness of wind power each year, despite the large investment going into this technology. Fortunately in the Irish case, the detailed data required to do the analysis is publicly available.
co2calc contains the details of the emissions model and the simple statistical analysis. It uses 1/2-hourly generation data compiled from market operator www.sem-o.com. Zipped data files can be downloaded below, although the script can also be run directly in an R terminal without downloading these files.
The European Wind Energy Association claims that wind power saves 0.696tCO2/MWh, while the British Wind Energy Association uses a figure of 0.43tCO2/MWh.
A 2012 report by the Institute for Public Policy Research, a UK think tank, entitled “Beyond the Bluster: Why Wind Power is an Effective Technology” claims that “every megawatt-hour (MWh) of electricity produced by wind power in Great Britain results in a minimum CO2 saving of around 350kg”.
(Paper submitted to Energy Policy, Elsevier November 2012)