1. Wind power output much higher in the U.S.:
The electricity output of wind farm plants in the U.S. is about 20% higher than assumed in the report. The report assumes an average output of 25-30% capacity factor, while in the U.S. the average capacity factor of a wind farm plant is between 30-35%. As a result, the cost of energy for a wind project in the U.S. will be about 20% lower than is assumed in this report.
2. Wind farm costs less in the U.S.:
The report claims that land-based wind farm plants cost between 1500-1900 euros per kilowatt (kW), which converts to roughly $1950-2450/kW. With 20-33% declines in wind turbine prices over the last several years, these costs are well on the high side for wind farm projects being installed in the U.S. today, making the cost of wind energy in the U.S. even further below what is claimed in the report.
3. Wind turbines displaces more coal generation in the U.S., increasing the carbon emissions benefits:
While the type of fossil fuel generation displaced by wind energy varies by region and over time, in many parts of the U.S. wind energy is displacing significant amounts of coal generation. While natural gas prices have fallen significantly in the U.S. over the last several years, coal prices have generally remained high, making coal power plants often the first ones to be turned off as wind power is added to the grid in some regions. Some detailed analyses of power grid operations, like the Eastern Wind Integration and Transmission Study, have also shown high penetrations of wind energy largely displacing coal generation, in part because coal plants are less flexible than less dirty gas power plants. Since burning coal emits roughly twice as much carbon dioxide as burning natural gas, wind’s emissions savings in the U.S. would be significantly higher than assumed in the report.
As an American commenter, I cannot say with certainty whether the above assumptions from the report are even valid for Europe. However, I can say with certainty that many of the report’s assumptions about how the power grid works do not hold up either here or in Europe:
4. Capacity value has no impact on carbon emissions, minimal impact on cost in most power systems:
The report claims that wind energy has reduced efficacy as a greenhouse gas reduction tool because it cannot entirely replace generating capacity provided by other types of generation. This represents a fundamental misunderstanding between the concepts of capacity and energy as they pertain to the power system. The simple act of keeping a power plant around so that it can provide capacity during the few hours per year when electricity demand is extremely high and wind power output is not high has almost zero impact on carbon emissions. What does affect emissions is when fossil fuel plants operate many hours per year to provide energy, and that is the main type of operation that wind plants replace.
A comparable argument is claiming that riding one’s bike to work does not reduce emissions because one still has a car sitting in the garage at home; in both cases, emissions only result from the burning of fossil fuels, not the simple act of having the car or power plant sitting unused. In addition, the report tries to claim that wind plants should be assigned the full cost of building a new natural gas-fired power plant that will sit idle until the hours when electricity demand is very high and wind output is not high. In reality, many parts of the U.S. and Europe are experiencing declining electricity demand that leaves them with excess generating capacity, meaning that the actual cost of this capacity is near zero. Moreover, as the report notes, demand response resources, underutilized hydroelectric resources, additional transmission investment, and innovative energy storage technologies are emerging as very low cost sources of new capacity, making the report’s assumption that the cost of new gas generation should be assigned to wind a major overestimate of the actual cost of any needed capacity.
5. Efficiency penalty is much lower than claimed, net effect of adding wind may actually be more emissions savings than expected:
Finally, the report claims that fossil-fueled power plants experience a significant decline in efficiency when they change their output to accommodate changes in supply and demand on the power system, including incremental variability added by wind energy. While the report does acknowledge that changes in electric demand and the unexpected outages of conventional power plants are among the largest sources of variability on the power system, it is important to keep in mind that much of the variability in wind energy output is canceled out by opposite changes in electric demand and supply. Moreover, the variability of wind farm plants spread over a large region is small and generally predictable, as it takes hours for a single weather event to affect a significant portion of the wind fleet; in contrast, outages at conventional power plants occur instantaneously and without warning, making them difficult and expensive for grid operators to manage.
In addition, any incremental variability added by wind energy is likely to be in large part handled by zero-emissions flexible resources, like hydroelectric dams, demand response, and energy storage. Even if fossil fuel plants are being used to accommodate some variability, data collected in the U.S. shows that most plants experience only negligible declines in efficiency when their output is reduced by 25% or more, and many types of power plants can reduce their output even further with no efficiency penalty. Finally, this analysis ignores the counteracting effect discussed above, whereby any incremental variability added by wind energy causes less flexible coal plants to be forced offline before more flexible and less polluting natural gas power plants. As a result, the net emissions benefit of adding wind to the power system is likely to be as large or larger than the amount saved if one only accounted for the direct displacement of fossil fired power plants.
By Michael Goggin, AWEA Manager-Transmission Policy, www.awea.org/blog/