Page 14 - North American Clean Energy January February 2015

wind power

Challenging Assumptions about Wind Energy

In the U.S. Southeast

By Brian O’Hara

Some people think working on wind energy in the Southeast region of the United States is nonsense and not

worth the efort involved. A few years ago they might have been right. But recent technology trends are forcing

those assumptions to be challenged.

In fact, if these trends continue, areas like the Southeast may be one of the most increases. Based on the available data, researchers believe that the wind shear, or
promising new frontiers for wind energy growth in the US. Here’s why.
the rate at which that increase happens, is higher in the Southeast than many other
parts of the country. That means the impact of taller wind towers is even greater in
Advancing technology
the Southeast than what might be seen in other areas.

It’s no secret: the wind over land in the Southeast is certainly not as strong as the
wind-belt states of the central US. The average wind speed in most states in the region Mapping the impact
is only 4 to 5 meters per second (m/s) at 80 meters above ground, at least according
The one-two punch of blades getting longer (which improves energy capture in
to the National Renewable Energy Laboratory (NREL), while Plains’ states enjoy wind lower wind speed sites) and towers getting taller (which places the turbine in higher

resources in the 6.5 m/s to 9 m/s range.
wind speeds), is resulting in a drastic change to the economic viability of land-based
Historically, turbine manufacturers have designed their machines for the most wind in the Southeast.
energetic sites, since that’s where they were deployed. In response to market To highlight that impact, the US Department of Energy commissioned researchers
needs over the last few years, however, manufacturers have unveiled new turbines, at the National Renewable Energy Lab (NREL) to develop a new set of “Past,

specifically designed for lower wind speed sites.
Present, and Future” wind resource maps*. These maps highlight how much area
This change has had a dramatic impact on the viability of wind energy in places such would result in a capacity factor of greater than 35%—a reasonable measure
as the Southeast. The relevant technology trends can be summarized by the following of economic viability—if developed using turbine technology and tower height

two statements:
assumptions for the past, present, and future. Incidentally, the future assumptions
are based on what major turbine original equipment manufacturers (OEMs) are
1. Blades are getting longer; and telling the NREL will likely be available in five to ten years from now.
2. Towers are getting taller.
The result is a striking story for the Southeast. Whereas almost no areas in the

region would attain that level of output using older (2008) technology at 80-meter
When lower is better
hub heights, development using the “future” assumptions would appear to exceed
The result of longer blades is a lower “specific power” rating of wind turbines, which is 35% capacity factors in virtually the entire region.
measured in watts per square meter (W/m2). In this case, lower happens to be better.
This offers a pretty compelling story about the expanded role wind energy could

A lower specific power means that for a given sized generator, the swept area of the play in the not too distant future. To corroborate this story, the Southeastern Wind
turbine blades—and, therefore, the amount of wind being harnessed—is greater. Even Coalition has released a set of state-specific fact sheets with these maps, as well as
with the added cost of longer blades, this change greatly improves the economics of data on current electricity sources and the wind industry supply chain assets in each
wind in lower wind speed regions, including in the Southeast.
state**.

Reaching taller heights
The future of the Southeast
Increasing tower height is also having an impact on the viability of wind energy in Wind energy has not played a significant role in the Southeast so far, but that
regions of lesser winds. Typically, wind speed increases as the height above the ground
will change soon. Nationally, wind energy is at historically low costs. Technology

14 JANUARY/FEBRUARY 2015 nacleanenergy.com