Wind power currently supplies 48 billion kilowatt-hours (kWh) of electricity annually in the United States, powering the equivalent of more than 4. 5 million homes. The U.S. wind energy industry shattered all previous records in 2007, with 45 percent growth and more than 5,400 MW of generating capacity installed (Figure 1). Wind farms accounted for about 30 percent of all new power generating capacity added in the United States in 2007. No other technology is installing zero-emissions power generation on such a scale today.
ANNUAL AND CUMULATIVE
25,000
Annual 20,000 Cumulative
15,000
MW
10,000
reserves of approximately $5 per megawatt hour, or roughly 10 percent of the cost of the wind energy. As we gain experience with wind, we keep seeking ways to achieve low integration costs,” Bonavia said.
Some question whether wind power, being a variable, non-dispatchable resource (meaning it generates electricity when the wind is blowing, not on demand) can be relied upon as part of a system that provides reliable electricity to consumers without interruption. Based on a growing body of analytical and operational experience, the answer is “yes.”
Many utilities and system operators have already found that large amounts of wind power can be reliably and economically integrated with the grid. Denmark receives more than 20 percent of its electricity from wind power and other countries in Europe produce significant amounts of their electricity from wind power as well (Table 1). Both Spain and Portugal had periods in 2007 when wind power provided more than 20 percent of their electricity. In the United States, Minnesota and Iowa both get close to 5 percent of their electricity from wind power. These examples illustrate that wind power can be a valuable part of a utility generation mix that supplies reliable electrical service to consumers without interruption.
5,000
0
1995
1997
1999
2001
2003
2005
Source: American Wind Energy Association
This growth has been spurred by utility companies’ increasing recognition that wind energy offers a variety of important benefits and can be reliably integrated at low cost. Paul Bonavia, Chief Operating Officer of Xcel Energy, said wind energy is an integral piece of the utility’s power supply portfolio. It provides a hedge against fuel price volatility associated with other forms of electric generation.
“Our studies and experiences show that wind energy integrates effectively and reliably into our power systems with regional market operations to mitigate the impact of wind variability. In these cases, even with 25 percent of the electricity on our system from wind, we forecast cost for operating system
When wind output decreases, reliable electrical service is maintained by turning up the output of other generators on the
2007 electric power system. System operators
can dispatch generators on their system such as natural gas-fired and hydroelectric generators. They have always actively dispatched their systems in response to electrical demand, which varies randomly over the course of an hour or day. Demand, like wind, is variable and non-dispatchable. Some generation is always kept in reserve to accommodate unexpected increases in load (demand) or to respond to the sudden loss of large conventional generating plants or transmission lines.
Conventional resources, such as baseload coal-fired plants or nuclear plants, occasionally shut down with no notice, often in fractions of a second; as a result, system operators are required to maintain operating reserves to address these “forced outages.” The power system can still be operated perfectly reliably in this fashion. Thus, “reliability” is not
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