This is an aspirational report, reflecting scenarios the department calls "ambitious but credible" which is to say it represents the upper bounds of feasibility. And it accomplishes this with assumptions of aggressive decreases in the cost of wind power, dramatic increases in the cost of fossil fuels, continued steady increases in the cost of nuclear, and by a considerable amount of handwaving about how the energy storage and levelizing problems will be solved cheaply. The statistical arm of the DOE, the EIA, in their analysis anticipates one seventh as much wind development based on more realistic trendline projections.
"Use of wind energy in 2013 has already reduced power-sector carbon dioxide emissions by 115 million metric tons."
That figure looks suspicious as hell. Wind energy provided 4% of the total kilowatt hours produced in 2013, and the electricity sector CO2 equivalent output was 2040 MMT. So this is saying that if you had removed that 4% of wind energy, then electricity sector emissions would have increased by more than 5.6%. So the assumptions here are 1) every watt hour of energy produced by wind was essential and would have been produced by other means without wind--which overlooks the wind gluts which create unwanted oversupply which has to be dumped. 2) every replacement watt hour comes from fossil fuels--not hydro or nuclear. and 3) that there is nothing related to wind power which has an adverse impact on CO2 reduction--which completely overlooks that the dominant form of backup is a peaking natural gas plant which typically has barely over half the efficiency of a slow-response combined-cycle gas plant. Since wind has considerably less than 50% capacity factor, the net result is nearly a wash compared to building a combined cycle plant and not building the wind power at all.
The article here cites Texas as a leader in wind development, which it is. But while it was doing its massive buildup of wind, up until the economic crash, Texas greenhouse gas emissions were also rising steadily. If the point of wind power is reducing greenhouse emissions, the Texas example should be cause for concern, not cheer. Texas wind power has been great for lining pockets and paying back political contributors, and for improving the economics of industries which can make use of erratic power output and capitalize on low-cost oversupply energy dumps, but the idea that Texas is any sort of model for how we can save the planet from the threat posed by fossil fuels is just a sad joke. Texas is the model for how wind power can coexist with, cooperate with, and even benefit fossil fuels.