Inconsistency of supply is one of the biggest drawbacks of renewables such as wind and solar. Put simply: the wind doesn't blow all day, and the sun doesn't shine at night.
Now scientists are saying that the sporadic supply of renewables coupled with an inefficient power grid means that carbon emissions, in real terms, are not completely eliminated by wind power.
Researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory used computer models to try to determine how adding wind turbines to the grid system might impact overall emissions in Illinois. According to their report, adjusting for wind power adds inefficiencies that cancel out some of the CO2 reduction – a conclusion that the American Wind Energy Association (AWEA) disputed.
The problem, according to he Argonne research, is not the clean energy itself but inefficiencies endemic to fossil fuel-burning power plants and how these inefficiencies are impacted by sporadic supply. Because the wind doesn't blow all the time, operators have to turn on these older plants to keep up with demand. Lauren Valentino, who authored the report, said in a statement: "Turning these large plants on and off is inefficient. A certain percentage of the energy goes into just heating up the boilers again."
According to Valentino the fossil fuel-burning power plants are also less efficient when not operating at full capacity.
Illinois in particular gets high winds at night, the report's co-author Audun Botterud said, when demand is low. To accommodate these sudden bursts of wind, large, inflexible power plants had to be turned off and then on again, wasting power in the process. The solution Botterud proposes to the problem of sporadic supply is one that readers of this site will be familiar with. Botterud said a way to store large-scale amounts of energy created from wind needs to be found. This problem is being tackled elsewhere in the Argonne lab, Botterud said, but in the meantime smart grids can help by leveling out demand.
However, the AWEA, the U.S. wind industry's big trade group, said the Argonne study was "a theoretical exercise" that "had "little to no bearing on how the actual utility system works."
Among other flaws it alleged, the AWEA said the Argonne modeling treated Illinois as a grid unto itself, but Illinois power plants actually feed into two massive interstate electric utility systems covering parts of 23 states and Manitoba. This, the AWEA said, led the study to assume "that at high levels of wind energy output in Illinois, grid operators would be forced to reduce the output of the state's very large nuclear fleet, thereby resulting in no emissions savings." In reality, however, the nukes "would likely never see their power output reduced, because that wind and nuclear power would be shipped out of state on the large power lines," the organization said.
The study was a collaboration between researchers at Argonne and summer interns Valentino and Viviana Valenzuela, from the University of Illinois at Urbana-Champaign and Georgia Institute of Technology respectively. It was published in Environmental Science & Technology. Other Argonne co-authors are Zhi Zhou and Guenter Conzelmann.
Of course all this being said, the biggest block on reducing carbon emissions in Illinois, like elsewhere, is a lack of investment in renewables. Like many states, Illinois has pledged to get 25 percent of its energy from clean sources by 2025. Yet it currently lags a long way behind its potential. According to 2010 figures, the state got 2.2 percent of its energy from wind.
A report issued by a trio of wind energy associations suggests that if the state of Illinois were to develop all 3,200 megawatts of currently permitted wind projects, it could potentially generate as many as 20,000 jobs and close to $1 billion in wages. The report from the Illinois Wind Energy Association (IWEA) said the state currently has about 2000 megawatts of installed wind energy capacity, but is in a position to generate much more.