I am all for wind power where it makes sense. It seems to make sense in certain high mountain passes in California where the wind is both strong and consistent – class 6 or 7 wind resources where class 3 or 4 is thought practical for power generation. For the most part, the US has thus far chosen its wind farm locations wisely in terms of energy generation. Some may say not so wisely from an aesthetic or habitat perspective, but that is not my concern here. Even without considering the base-load issues of wind (see previous post), projecting wind energy’s capability to supply a major portion of US energy demand by extrapolating from such high quality wind resources is ludicrous.
America’s wind farms on average have an output of about 1.4 watts per square meter of land they occupy. The Roscoe facility in Texas does somewhat better at about 1.9 w/sqm and California’s top locations do about 2.8 w/sqm. Data from the US Department of Energy National Renewable Energy Laboratory and AWS TruePower, a group that does wind analysis for DOE (which does seem a bit prone toward telling us what we want to hear) shows most of the US to fall far below these sites in capability.
Bold claims have been made by enthusiasts like Al Gore and advocacies like the Energy Justice Network about wind’s potential to power all our energy needs. Let’s take a quick look.
American energy demand in 2010 was 28,700 terawatts. Though peak demand is much higher than average demand, for the sake of easy (conservatively erring in wind’s favor) we can distribute that total energy consumption over 24 hours for the year and get an average power demand of 3.3 million megawatts for the US. The land area of the 48 contiguous states is 8.1 million square kilometers. With a 1.4 watts per square meter (equals 1.4 megawatts per square kilometer), we’d need 2.3 million square kilometers of wind farms to supply our 2010 consumption with wind. That amounts to 29% of the land area of the contiguous 48.
The portion of the US that would be needed to supply this power, without consideration of distribution, urban and reserved land, and wind resource quality then looks like this:
The National Renewable Energy Laboratory has published a lot of the AWS TruePower work on potential wind sites in America, usually focusing on areas with a capacity factor of 0.3 or greater, broken down by wind speed. Their charts show most of the US as having some potential for wind generation, but many wind advocates are clearly unaware that the energy contained in wind is not proportional to its velocity. It may seem that the forces of nature conspire against us, but the energy content of two mile per hour wind is only 4% of the energy content of ten mph wind. Worse yet, wind turbines are designed for peak efficiency at one specific speed; thus a wind turbine designed for 10 mph (4.5 m/s) wind will get much less than 4% of its design power with a 2 mph wind (more on that here).
The below map is based on a similar one at the DOE Wind Program site. Using Photoshop’s Hue-Saturation-Brightness tool I whitened the useless wind resources from their color coded map, removing the color for wind regions below wind power class 3 at a height of 80 meters (260 ft). Here’s what’s left, from which it is very apparent that wind can play only a limited role in American energy even if we cover every square foot of land where quality wind blows – without regard for environmental, aesthetic and practical considerations.
When President Obama recently said “all of the above” about energy policy, he certainly meant all of the above where sensible. Large subsidies to wind (which have thus far gone primarily to direct expeditures, not R&D) do not meet this requirement. Unbridled wind advocacy, whether stemming from uninformed enthusiasm, dirty politics, or corporate greed, contributes to the wickedness of our energy problem by taming a small increment of it whilst creating the illusion that the solution approach is scalable. Engineering fundamentals show that the energy problem is indeed solvable, so there’s plenty of room for optimism. But let’s not set ourselves up for disappointment by ignoring the hard facts about wind.