Google has signed a 20-year purchase agreement to buy all the power generated by a 100-megawatt wind farm to be built near one of its data centers in Mayes County, Oklahoma. Greenpeace steps up its criticism of big Internet companies for using “dirty power” that contributes to global warming. Google: “These purchases represent long-term, meaningful actions to reduce our carbon footprint and power our operations with clean electricity” Google also published a white paper explaining the complexities of trying to use renewable energy to run a data center.”]