Energy and Human Ambitions on a Finite Planet, 2021a

12 Wind <strong>Energy</strong> 193
0.1 0.2 0.3 0.4
Wind capacity factor
Figure 12.11: Capacity factor for wind installations
by state (based on 2018 data).
12.4 Upshot: Wind is not Overblown
Wind has surged tremendously in the last decade (Fig. 7.5; p. 108),
proving to be an economically viable <strong>and</strong> competitive resource. But how
much could we expect to get from wind?
Putting a few of the previous results together, If the entire contiguous U.S.
(area ∼10 13 m 2 ) were developed for wind at an estimated power density
of 0.2 W/m 2 —which was based on a 5 m/s average wind speed—<strong>and</strong> a
capacity factor of 33%, the U.S. could theoretically produce 0.7 TW 30 30: We’re fudging things a bit here for
from wind—roughly 20 times what is produced today. We should take
this crude estimate as an extreme upper end, since it is inconceivable
that we would develop wind so fully as to never be more than a few
hundred meters—a few rotor diameters—away from a wind turbine, no
matter where we go. Also, many areas are sub-threshold <strong>and</strong> would not
support investment in wind development.
Even so, the inflated 0.7 TW estimate falls short of the current 3.3 TW
energy dem<strong>and</strong> in the U.S., has major intermittency problems, <strong>and</strong> is
not in a form that can be well-used in all sectors, like transportation <strong>and</strong>
industrial processing. While wind alone cannot replace fossil fuels at the
current level of dem<strong>and</strong>, it can doubtless be a significant contributor.
Globally, estimates for wind potential tend to be in the few-terawatt
range, though can be as low as 1 TW for a number of practical reasons
. As was the case for hydroelectricity, wind is a viable player in the
renewables mix, but is unable to shoulder the entire load.
the sake of simplicity. If turbines are built
for 12 m/s, the capacity factor already has
some averaging built in, so using 5 m/s <strong>and</strong>
a capacity factor of 0.33 is unfair. On the
other h<strong>and</strong>, much of the country spends
substantial time below the cut-in speed for
turbines, <strong>and</strong> the cruel cubic function of
velocity greatly suppresses much of the l<strong>and</strong>
area as impractical for wind development.
So the approach is a compromise that might
balance out reasonably.
[70] [70]: Castro et al. (2011), “Global Wind Power
Potential: Physical <strong>and</strong> Technological Limits”
Wind energy is not free of environmental concerns, disturbing l<strong>and</strong>scapes
<strong>and</strong> habitats. Its impact on birds 31 <strong>and</strong> bats is most worrisome, as the
rotors move far faster than anything to which the wildlife is habituated.
Still, compared to the environmental toll from fossil fuels, it is fairly
clean—similar to the impact of hydroelectric power.
A pros <strong>and</strong> cons list will help summarize. First, the positive attributes:
31: Domestic cats turn out to kill far more
birds than wind turbines do, currently.
◮ Wind is replenished on the planet daily by solar illumination;
© 2021 T. W. Murphy, Jr.; Creative Commons Attribution-NonCommercial 4.0 International Lic.;
Freely available at: https://escholarship.org/uc/energy_ambitions.