Windaction.org has updated its database of US wind production and capacity factors to include the years from 2011 through to 2015. The data are based on monthly energy output figures released by the U.S. Energy Information Administration. Aggregate annual capacity factors for each state and for the nation can be found here. A spreadsheet of each project for which production is reported can also be downloaded from the page.
There is apparent consistency from year to year for most states and for the country. The US average annual capacity factor is holding at around 32% overall, but some states are clearly more productive than others.
|US Production and |
Many factors contribute to a project's capacity factor including transmission curtailments, turbine availability and, of course, the wind resource. We are beginning to see larger turbines sited with longer blades that could result in production increases. Newer blade technology is included in the 2014 and 2015 projects but the effect is not apparent in the aggregate numbers since the megawatts are low. Also, most of these projects do not have a full year of production under their belt, so their production data are not factored into the computed capacity factors.
In looking at the data, we can also see the impact of the wind-drought that hit the western region of the country in 2015 resulting in notable drops in capacity factor in Oregon, Washington, and Idaho. California and Texas were also hit hard by the drought but appear to have recovered overall from the deep loses of Q1'15. However, looking at the production for individual projects is more revealing. For example. NextEra's Horse Hollow Wind Energy Center (736 MW facility in Texas) had an annual capacity factor in 2015 of 30.9%, down from 35.8% in 2014.
Not all wind projects are cited by EIA individually in every year. This helps explains why some states may show wide fluctuations in average capacity factors from one year to the next. This would be the case for Delaware, Rhode Island, New Jersey and Alaska, but overall, the production trends are notable.