"This report assumes a fictional world that bears no relation to how real power systems operate, and as a result vastly overstates the impact of variable resources like wind power," said Denise Bode, CEO of AWEA, herself the former head of the Regional State Committee of the Southwest Power Pool, and former chairman of the Oklahoma Corporation Commission that regulates the energy industry.
"American wind power has added over 10,000 megawatts to the grid in a single year. Wind has built 35% of all new U.S. electric generation since 2007. And at this moment we need that safe, affordable homegrown electricity more than ever," Bode added. "Wind turbines makes the grid more reliable, not less, as we’ve seen in Texas where wind turbines provides about 8% of the state’s electricity, or in Iowa where we’ll soon reach 20%."
Michael Goggin, Manager of Transmission Policy for AWEA, provided the following analysis:
The report is based on a fundamental misunderstanding of how the power system works. The power system has always had large amounts of variability and uncertainty, driven by things like factories turning large electrical equipment on and off, millions of people changing their use of air conditioning and electric heating as the weather changes, and large conventional power plants experiencing sudden outages due to mechanical or electrical failures taking 1,000 MW or more offline instantaneously.
The report fails to understand that all sources of variability and uncertainty are integrated together on the grid, many of them canceling each other out. Much of the time downward changes in wind output are being canceled out by downward changes in electricity demand, and vice versa. Deviations in the output of conventional generators also cancel out opposite changes in wind output. Attempting to "firm" wind by holding it constant will be counterproductive in many cases by increasing the variability that grid operators have to deal with.
A comparable example would be arguing that I need to tie a battery or a natural gas power plant to my house to accommodate all of my changes in electricity use as I turn various appliances on and off. Obviously such a solution would be grossly inefficient, as it would ignore the fact that my changes in electricity consumption are being canceled out by opposite changes in other consumers’ electricity use. That benefit of aggregation is one of the main reasons why we built a power grid in the first place, yet this report is written around the assumption that wind power variability would not be aggregated with other sources of variability.
Because of this, the report grossly overstates the true incremental impact of adding wind power on aggregate power system variability. All sources of variability must be statistically combined, which has the effect of reducing smaller sources of variability (like wind) to an almost inconsequential amount. Because load is a so much larger source of variability than wind, in most cases except for very high wind energy penetrations, load variability dwarfs incremental wind variability.
As a hypothetical example, a typical power system might have 100 MW as the average 10-minute variability of load, while the variability of wind output over this time scale might be 5 MW (data from actual wind farm plants shows that the output of wind farmplants, particularly multiple wind plants spread over a broad area, tends to remain relatively constant over the 10-minute time frame). In this example, the aggregate system variability would be the square root of 100^2+5^2, or 100.125. Thus, the wind turbines fleet’s incremental variability would be 0.125 MW. In contrast, this report would assume that the entire 5 MW of wind variability must be accommodated, which would overstate wind’s actual impact by a factor of 40. If other sources of variability, like conventional generators’ deviations from scheduled output, were also accounted for, wind’s incremental burden would be even further reduced. This report accounted for none of these counteracting sources of variability, and thus so grossly overstates the incremental variability associated with adding wind energy to the grid that the results of the study are almost entirely useless.
It appears that many of the gas infrastructure investments and operating changes proposed in the report are changes that would be needed anyway, even in the absence of wind energy. Natural gas use for electricity generation is rapidly increasing anyway, and it would have been easy for the authors to argue that corresponding investments and changes in gas system operating procedures will be needed. However, possibly in an attempt to pass the costs for these changes onto a new and politically popular resource like wind energy, the report made the crucial mistake of ignoring the fact that the power grid is a complex system with many interrelated parts. As a result of the attempt to single out wind by creating an artificial segmentation of the power system that is completely contrary to the integrated manner in which the grid actually works, the authors were left with a study that produced meaningless results.
In contrast, the North American Electric Reliability Corporation (NERC), the organization of electrical grid operators responsible for maintaining grid reliability, has said that modern wind farm plants’ abilities to contribute to grid reliability can meet or exceed those of conventional generators.
By Michael Goggin, Manager of Transmission Policy for AWEA. Michael Goggin is available for interviews, which can be scheduled by contacting Ellen Carey of AWEA media relations at 202-249-7357 (office), 405-203-9535 (cell), or ecarey@awea.org.
