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Wind power CO2-cutting benefit challenged

We’ve long known wind power’s flaws – produces inconsistently, can’t be economically stored, kills birds – but along with those came an obvious, sparkling virtue: It runs clean, helping drive down carbon dioxide (CO2) emissions in a big way. But a Colorado-based energy research firm is challenging that last assumption, asserting that analysis of real-world data shows in most areas of the country the CO2 savings from wind “are either so small as to be insignificant or too expensive to be practical.”

Bentek Energy calls this “the wind power paradox,” and says the issue is what happens when wind power comes onto the grid. “When power plants on a regional power grid are ‘cycled’ to accept wind energy, the plants run less efficiently, leading to significant emissions and higher plant maintenance costs,” the firm said.

Bentek bases this conclusion on what it calls the first study “to systematically assess the emission reduction performance of wind generation based on hourly generation and emissions data.” The firm said it worked with Daniel Kaffine of the Colorado School of Mines to collect and analyze hourly data – instead of making projections based on average data – on U.S. wind generation and emissions from plants in four regional power areas.

Esoteric though it may sound, this point of hour-by-hour vs. average is crucial to the criticism of wind power, because it focuses the analysis on marginal emissions as generation shifts between wind and conventional sources. In a draft paper on his website entitled “Emissions savings from wind power generation: Evidence from Texas, California and the Upper Midwest,” Kaffine and his co-authors explain that wind power coming onto the grid tends to overwhelming replace relatively clean natural gas, not dirty coal. That alone trims wind’s CO2-saving contribution, Kaffine writes. And so does the ramping up and down of coal-fired generation. After drawing an analogy with an automobile driving steadily at 55 mph vs. one stop and starting, Kaffine writes: “When coal plants are cycled down to accommodate wind, those plants will be operating at an inefficient level of output, raising emissions rates.”

In his academic study, Kaffine concludes “this paper provides a transparent framework for updating and refining emission savings estimates as data.” Bentek, however, goes much further, stating that while some regions of the country – the Midwest, especially – show more CO2 savings from using wind power, “In none of these areas … are the savings sufficient to justify the federal tax credit that underpins the technology.”