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of wind. “Peak summer loads coincide with periods when there usually isn’t much wind, while the opposite happens during winter, meaning large differences in terms of gas-fired plant load: on 20
June 2008, Spain broke a record in terms of peak daily gas demand from the power sector.”
    On that day in June 2008, Spain’s gas-fired generators were operating at a capacity factor of 75 percent. But six months later, on December 20, when the wind was blowing strongly, the capacity factor for the country’s gas-fired generators was just 18 percent. “Such fluctuations require heavy investments in gas storage, particularly of the type needed to respond quickly to large gas demand movements from power generators,” said the IEA. 7
    Though it is true that gas consumption declines during periods when the wind is providing lots of electricity, it’s not yet clear how large those savings will be. Nor is it clear that the savings in fuel costs will be enough to offset the capital costs incurred to install the needed gas storage capacity, pipelines, and generators. Furthermore, all of that gas- and power-delivery infrastructure—and the generators, in particular—must be staffed continually. The utilities cannot send workers home only when the wind is blowing. The generators must be available and staffed to meet demand 24/7.
    The additional costs imposed by wind power can be seen by looking again at Colorado, one of the states in the vanguard of the push for renewable energy. In 2004, Colorado voters approved a ballot measure requiring the utilities in the state to generate or purchase enough renewable energy to supply at least 10 percent of their retail electricity sales. Since that time, the state’s legislature has raised that target to 20 percent of retail electricity sales, and that target must be met no later than 2020. 8 In December 2008, Xcel Energy, a natural gas and electric utility that serves customers in eight states, issued a report on the costs associated with integrating wind power into its mix of generation assets in Colorado. 9 The study says that the utility expects “the costs of integration to be predominantly fuel costs resulting from 1) the inefficiency of generation due to wind generation uncertainty,” and “2) the cost of additional gas storage.” 10
    To be clear, the integration of wind power into a specific electricity grid will vary widely depending on the size of the grid, what types of fuels it uses, and the amount of wind being added. But Xcel is correct about the need for gas storage. The gas-fired generators needed to back up
wind power must be switched on or off several times per day, and underground gas storage facilities must be located relatively close to the generators so that there is enough pressure in the gas pipeline to keep the generators going. For parts of the United States that have favorable geology—consider western states such as Colorado, Texas, Oklahoma, and Kansas, where gas production is common—the gas storage issue may not pose a problem. But in other states, and particularly in other countries with less-favorable geology, the lack of gas storage may pose a real barrier to wind power.
    TABLE 3 States That Get More Than 80 Percent of Their Electricity from Coal

    State
Electricity from Coal
West Virginia
97%
Indiana
95%
Wyoming
94%
North Dakota
93%
Kentucky
93%
Utah
89%
Ohio
86%
Missouri
84%
New Mexico
80%
    Sources : EIA, American Coalition for Clean Coal Electricity, “Your State” (clickable map), http://www.cleancoalusa.org/docs/state/ . Data current as of July 2009.
    Despite the situation in Colorado, there have been no comprehensive studies, on either the federal level or the state level, exploring how increasing deployment of wind power will affect natural gas infrastructure and demand. Furthermore, the dynamics of the wind–natural gas relationship will vary widely. It will likely be particularly