The West Michigan Wind Assessment is a Michigan Sea Grant-funded project analyzing the
West Michigan Wind Assessment April 2013
Page 1
Introduction
Wind turbines generate electricity without directly emitting air pollutants that
are known to affect the climate and human health. Wind turbines, however, do not
operate in a vacuum. They are integrated into the larger electrical grid that includes
coal and nuclear plants, natural gas turbines, hydroelectric dams, solar panels and
other technologies. The interactions between these electricity sources are complex.
If a new wind farm “displaces” a more polluting energy source - for example if
utility-scale wind farms have been in operation around the world for more than two
decades, it is possible to evaluate whether wind farms actually reduce air pollution
from the electricity sector.
wind energy as it is integrated into the electric grid. The brief includes estimates
of the pollution-reducing potential of wind energy in Michigan using a variety of
methods and the results of several life-cycle, or cradle-to-grave, analyses for wind
turbines. The science suggests that wind energy can be successfully integrated into
the electricity grid and doing so can reduce emissions of air pollutants like sulfur
dioxide (SO
2
x
) and carbon dioxide (CO
2
).
How Will Wind Energy Affect Air Pollution?
Wind turbines reduce air pollution by displacing a more polluting form of electricity
generation with wind-generated energy. The more polluting the displaced fuel is,
modelers use a combination of historical electricity and pollution emissions data,
computer models of grid interactions, and projections for future installations to
estimate the air pollution emissions from different mixes of electricity generation
sources. This technique is called dispatch modeling.
and government agencies related to dispatch modeling and the integration of wind
if any, fuels they
Estimates of
farms reduce
as the cost of those
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West Michigan Wind Assessment 2013
as well as the cost of those reductions, varies widely. These reductions are dependent
on the electricity generation mix in a region. This mix depends on the location of
the current energy source and which types of energy sources would be reduced if
wind farms were built at that location. This section summarizes a recent report from
20% Wind Energy by 2030
papers on the air-pollution-reducing potential of wind energy (Table 1).
but it would likely have a bigger effect on our use of natural gas. The Department
about 18 percent. Cumulative avoided CO
2
emissions would reach 7.6 billion tons by
the electricity sector from increasing substantially over the next 25 years (Figure 1).
CO
2
needs, regardless of the future mix of energy generation. If we build enough wind
allow us to use a wide range of energy sources in the future and enable greater
reductions in air pollution.
approach to understand the complex interactions among grid electricity sources.
potential of wind energy.
The Department
of Energy predicts
that if 20% of
our electricity
our natural gas
consumption by
about 50% and
coal consumption
us an additional
and beyond the $2
in the electric grid
that is needed to
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West Michigan Wind Assessment 2013
Study Author Locaon Conclusion
Delarue and colleagues
(2009) [2]
Belgium
Each megawa (MW) of installed wind capacity could
avoid 1,240 tons of CO
2
emissions, or about 500 kg CO
2
/
MWh.
Denny and O’Malley (2006)
[3]
Ireland
800 MW of installed wind capacity (11% of Ireland’s
total capacity) could reduce CO
2
emissions by 9%.
Adding wind to the grid did not substanally reduce SO
2
and NO
x
emissions, but combining wind with a carbon
tax did reduce SO
2
and NO
x
.
Denny and O’Malley (2007)
[4]
Ireland
The esmated benets of integrang wind into the
electricity grid exceed the esmated costs for wind
installaons up to about 20% of total capacity. The net
benets were about €1 billion ($1.3 billion) at nearly
2,000 MW of installed wind capacity.
Hart and Jacobson (2011) [5] California
A low-carbon electricity porolio (including wind) could
reduce emissions by 80% relave to 2005.
Holnen and Tuhkanen
(2004) [6]
Nordic
countries
Wind penetraon of 4-12% displaces mostly coal and
avoids CO
2
emissions at a rate of 700-620 g/kWh and a
cost of €20-35/ton (about $26-46/ton).
Jacobson and High (2010) [7]
Upstate New
York
The “me-matched marginal” method for calculang
emissions is more accurate than other methods. In their
N.Y. example, each 10,000 MWh of wind generaon
avoided 9,160 tons of CO
2
emissions
Kane and colleagues
(2011) [8]
Midwest,
Texas,
California
In the Midwest Independent System Operator grid
(including Michigan), 1 MWh of wind generaon avoids
4.9 lbs. of SO
2
, 2.0 lbs. of NO
x
, and 1.0 tons of CO
2
.
Katzenstein and Apt (2009)
[9]
5 regions in
U.S.
Displacement is not 1-to-1 because of backup reserves.
Realized polluon reducons are likely 75-80% of simple
esmates for CO
2
, 30-50% for NO
x
. Under the worst
condions, NO
x
emissions actually increased under a
20% wind scenario.
Lu and colleagues (2011)
[10]
Texas
30% wind penetraon could result in a 58% reducon
in CO
2
emissions (81 million tons per year) and could
increase electricity price by $0.011/kWh. The marginal
abatement cost of CO
2
reducon at 30% wind was $20/
ton.
Luickx and colleagues (2010)
[11]
Belgium
As wind capacity increases to 4.5 GW, CO
2
reducons
range from 5% to 60% depending on the specic wind
condions.
Troy and colleagues (2010)
[12]
Great Britain
Adding wind capacity increases system cycling, especially
in baseload plants. At lower levels of wind penetraon,
adding storage capacity can increase cycling of baseload
units. Storage becomes more favorable at high levels of
wind penetraon.
Ummels and colleagues
(2007) [13]
Netherlands
Emissions of CO
2
and NO
x
decline as wind penetraon
increases, up to a 25% reducon at 8 GW of wind
capacity. SO
2
emissions decline only slightly. Load
balancing problems can occur in systems with large
amounts of combined heat and power which results in
wasted wind energy. Wasted wind is insignicant below
4 GW (9.7% of total capacity)
1
.
1
Both are used in the literature on CO
2
emissions. The results reported in the table and elsewhere in the
All of the reports
farms can reduce
CO
2
emissions,
although
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West Michigan Wind Assessment 2013
be integrated into the grid and that doing so reduces CO
2
reports predict that wind energy would have no effect on air pollution. The addition
of wind energy to the electricity grid, by itself, is less effective at reducing SO
2
and
x
emissions than reducing CO
2
. The addition of a carbon tax could change the way
types of power plants in a given region.
speeds, which requires that other power plants increase their production when winds
x
emissions) could increase, depending on the type of turbine and on how
the turbines are ramped up and down, when the gas turbines are quickly ramped up
x
emissions fell, but not by as much as expected. When a different
x
emissions increased relative to a zero-
x
emissions. The study authors concluded if “system
operators recognize the potential for ancillary emissions from gas generators
Mo
fuels: coal, natural gas, and relatively small amounts of petroleum and various
like carbon dioxide (CO
2
Michigan’s electricity sector emitted 68 million metric tons of CO
2
The project team used two methods to estimate the emissions reduction potential of
database to estimate the degree to which wind energy (or other so-called green
typically used as “baseload sources”, continually generating electricity for the grid.
more easily ramp up and ramp down electricity production in response to varying
power demands or varying levels of electricity coming from other sources such as
wind farms.
so the team used four different estimated CO
2
reduction, capacity factors
2
, for the
calculations (Table 2).
Most of
Michigan’s
electricity, 75% in
2009, is generated
by burning fossil
plants are most
operating at a
they are typically
used as “baseload
sources”, continually
generating
electricity for the
Wind farms may
require that
plants operate
could affect
energy use and
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West Michigan Wind Assessment 2013
2
Table 2 illustrates that integrating wind energy into Michigan’s electricity grid can
reduce greenhouse gas emissions, even if wind energy displaces only non-baseload
2
emissions
could eliminate CO
2
2
would eliminate the average CO
2
emissions for either of
these geographic areas.
(MISO), the grid operator for the Midwest states including Michigan, to estimate how
much pollution could be avoided by using wind energy. Their approach accounted
for not only the marginal unit of generation displaced by wind, but also the marginal
emissions from the displaced generation. The researchers found that each MWh of
2
x
2
. The MISO grid is more coal-dependent than Michigan, where
portfolio with 66 percent coal by interpolating from the graph in the article by
2
, 1.5 pounds of
x
2
• More than 1 million pounds of SO
2
•
x
•
2
for a similar electricity output.
Capacity
Factor
2
Esmated Annual
Electricity Output
(kWh)
Esmated Annual CO
2
Emissions Reducon
(tons)
Number of Households
Supported by a 100 MW
Wind Farm
20% 175,200,000 157,998 17,872
25% 219,000,000 197,499 22,340
30% 262,800,000 236,998 26,808
35% 306,600,000 276,498 31,276
2
Capacity factor refers to the proportion of electricity actually generated compared to a wind farm’s
maximum potential to produce electricity. For example, a 1 MW wind turbine operating at full capacity
conditions.
A single 100MW
electricity-based
CO
2
emissions from
approximately
17,000 to 31,000
Each MWh of
added to the
pounds of SO
2
pounds of NO
x
, and
2
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West Michigan Wind Assessment 2013
2
x
emissions, and eleventh in CO
2
6.1 percent of the renewable requirement were met with wind energy, Michigan
could reduce substantial amounts of pollution, including a 6.9 percent potential
reduction in CO
2
Life cycle analysis (also known as a cradle-to-grave analysis) is a technique used to assess the
environmental impacts associated with all the stages of a product’s life from raw material extraction
through materials processing, manufacture, distribution, use, repair and maintenance, and disposal or
recycling.
Carbon dioxide equivalent is a metric measure used to compare the emissions from various
greenhouse gases based upon their global warming potential.
SO
2
(million lbs)
NO
x
(million lbs)
CO
2
(million tons)
Total emissions in 2009 545.2 157.9 73.6
Esmated emissions reducon
from exisng renewable energy
(3.9%)
-1.05 -0.45 -0.25
Esmated emissions reducon if
another 6.1% of energy came from
wind
-21.6 -9.3 -5.1
Percentage reducon if another
6.1% of energy came from wind
-4.0% -5.9% -6.9%
Power plants, including wind farms, also use electricity and generate pollution when
they are being built, maintained and then demolished at the end of their lifespan.
Figure 2 shows the cumulative greenhouse gas emissions, from “cradle-to-grave
” for
emission are in grams of carbon dioxide equivalent
per kilowatt hour of electricity
or gCO
2
e
.
generated electricity occurs when the turbines are being constructed. Offshore wind
turbines require large amounts of concrete and steel for their foundations, so their
small amount of emissions will occur while maintaining wind turbines. In contrast,
the majority of the emissions associated with fossil fuel based electric generation
occur during the operational phase of the power plant.
In 2009, Michigan
produced a total
of 101 million
MWh of electricity,
ranked 6th among
states in total SO
2
emissions, 6th in
NO
x
emissions,
and 11th in CO
2
farms, also
use electricity
and generate
they are being
built, maintained
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West Michigan Wind Assessment 2013
Figure 2: Cumulative carbon dioxide emissions from different types of energy facilities over the
2
2
Other scientists have reached similar conclusions on the life-cycle emissions of wind
from wind turbine manufacturing, use and decommissioning is offset by its use in
and decommissioning.
One study
found that the
pollution from
manufacturing,
use, and
decommissioning
is offset by
turbine for just one
2
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West Michigan Wind Assessment 2013
not straightforward and different scientists and methods predict different results.
If managed appropriately, wind energy has the potential to reduce the use of fossil
that integrating wind energy will result in some reduction of conventional pollutant
emissions such as SO
2
as well as greenhouse gases like CO
2
. However, the air quality
term, wind farms are more likely to reduce Michigan’s reliance on natural gas than
coal.
Wind energy is not a silver bullet for Michigan’s air pollution and climate challenges,
reduce CO
2
deployment would also reduce SO
2
x
, which would improve air quality. Life-
energy than what went into manufacturing, operating and decommissioning the
wind turbine.
result from Michigan’s constructed wind farms.
Wind energy is
for Michigan’s
air pollution
and climate
challenges, but
substantial
is readily
The actual effect of wind power on overall electricity
generation costs and CO
2
to generator portfolio planning and carbon emissions
assessments of systems with large penetrations of variable
power on CO
2
necessary to ensure accurate assessment of the air emission
estimates of emissions avoided from wind power
costs for savings in CO
2
amounts of wind power on the operation of an electricity generation
Impacts of wind power on thermal generation unit commitment and
1559.
analysis of wind turbines and the effect of size on energy yield.
Life-cycle assessment of a 2-MW rated power wind turbine: CML
