WIND ENERGY CO2 EMISSION REDUCTIONS ARE OVERSTATED
Because
wind energy is variable and intermittent, it requires backup by
quick-ramping, open cycle gas turbine generators that ramp up when wind
energy ebbs and ramp down when it surges which occurs at least 100 times
per day. Such part-load-ramping operation is inefficient and requires
extra fuel/kWh and emits extra CO2/kWh. The extras offset a significant
part of what wind energy was meant to reduce, as proven by studies of
the Irish, Texas and Colorado grid operations data. The studies are
based on 1/4-hour and 1-hour grid operations data.
Study of Irish Wind Energy:
The Irish grid was selected for analysis, because Eirgrid, the grid
operator, is one of the few that publishes the following real-time,
1/4-hr grid operations data:
- CO2 emissions, gram/kWh
- wind energy produced, GWh
- total energy produced, GWh
Ireland’s Energy Generation:
Ireland’s total electricity production was about 26,000 GWh in 2010.
Gas-fired OCGTs and CCGTs provided about 65.5%, coal 13.2%, peat 8.2%,
wind 9.8%, hydro 2.5% of which 1.7%, or 442 GWh, was
impounded/run-of-river hydro. Ireland imports 100% of its coal, about
90% of its gas and produces 100% of its peat.
Wind Energy:
In Ireland, good wind energy months are April, May, June, November and
February. On the west coast of Ireland, wind energy is greatest during
summer daytimes, because of increased wind speeds as the lands warms up.
The west coast wind energy coincides with greater daytime demands which
is fortuitous. However, much of the energy needs to be transmitted to
the east coast (line and transformer losses), as few people live on the
west coast.
Coal/Peat:
The below website shows coal/peat plants are base-loaded, i.e., not
used for balancing wind energy, i.e., their CO2 emission intensities are
essentially constant.
http://ee.ucd.ie/erc/member/2005transdenny.pdf
Hydro:
Ireland has many small hydro plants and a few larger plants, such as
the Ardnacrusha power plant, built 1929, capacity 85 MW, output 332
GWh/yr, Cathaleens Falls 45 MW, Poulaphuca 30 MW and Inniscarra 19 MW.
The below website shows hydro plant outputs follow daily demand, i.e.,
not used for balancing wind energy.
http://www.dconnolly.net/files/Modeling%20the%20Irish%20Energy-System%20-%20Data%20Required%20for%20the%20EnergyPLAN%20Tool.pdf
The
almost 40-year old, 292 MW Turlough Hill pumped-storage facility pumps
to add to its upper reservoir during low nighttime demand and produces
energy during peak daytime demand. Its net effect is to “flatten” the
daily demand profile. It is not used for balancing wind
energy. Currently, it operates at about 50% of capacity, because of
ongoing modifications.
Combined-Heat-Power:
Ireland has about 195 units totaling about 282 MW of operating
combined-heat-power, CHP, plants of which a few larger units totaling
248 MW is dedicated to industrial processes, such as food, manufacturing
and pharmaceutical. The output of these units is independent of the
weather.
CHP energy generation was 6.3% of Ireland’s total energy generation in 2008 (latest data).
Only
11 CHP units (mostly associated with industrial processes) exported
1,013 GWh to the grid in 2008, or 1,013/260 = 3.9% of total production.
Eirgrid includes the output and CO2/kWh of these units in its 1/4-hour
data sets.
CHP heat generation was 4% of Ireland’s total heat generation in 2008 (latest data).
The above indicates CHP operations have no material impact on the 1/4-hour CO2/kWh posted by EirGrid.
http://www.seai.ie/Publications/Statistics_Publications/EPSSU_Publications/CHP%20in%20Ireland%202010%20Report.pdf
OCGTs/CCGTs:
A part of the OCGT/CCGT capacity serves base-load, follows daily
demand, provides peaking power and performs voltage and frequency
regulation. It also performs wind energy balancing, if it has sufficient
spare ramping range to ramp down with smaller wind energy surges and
ramp up with smaller wind energy ebbs.
Because
larger wind energy surges and ebbs are unpredictable, additional
OCGT/CCGT capacity needs to be in spinning and part-load-ramping mode
for balancing wind energy; the greater the wind energy, the greater the
additional spinning and balancing capacity.
Because
of much degraded heat rates, gas turbines are rarely operated below 40%
of their rated output which limits their ramping range from 40 to 100
percent of rated output.
http://theenergycollective.com/willem-post/57905/wind-power-and-co2-emissio
How EirGrid Calculates CO2 Emissions/kWh: The following is a direct quote from the EirGrid website:
“EirGrid,
with the support of the Sustainable Energy Authority of Ireland, has
developed together the following methodology for calculating CO2
Emissions.
The
rate of carbon emissions is calculated in real time by using
the generators MW output, the individual heat rate curves for each
power station and the calorific values for each type of fuel used.
The heat rate curves are used to determine the efficiency at which a generator burns fuel at any given time.
The fuel calorific values are then used to calculate the rate of carbon emissions for the fuel being burned by the generator“
Grid
operators know the heat rate curves of the plants on their grids which
were obtained by testing. They need to know this for economic dispatch.
Eirgrid
takes the percent of rated output each plant is operated at and
multiplies it by the heat rate for that output percentage (from the
above mentioned heat rate curve) to calculate the fuel consumption/kWh
and CO2 emissions/kWh every 1/4 hour. It posts the grid CO2 intensity
(CO2 emissions of all plants/total kWh produced by all plants) as gram
CO2/kWh on its website every 1/4 hour.
The EirGrid CO2 emissions/kWh are understated, because they do not account for the extra CO2 emissions due to:
- Increased spinning plant operation; extra fuel and CO2
- Increased start/stop operations; extra fuel and CO2
- Increased ramping operation; less efficient, extra fuel and CO2
- less than optimum scheduling of generating units for balancing wind energy
- increased line losses to gather the distributed wind energy
Note: In my discussions with Mr. O’Sullivan, energy systems analyst of Eirgrid, he confirmed:
-
Eirgrid does not account for degradation of heat rates due to up/down
ramping, and for starting/stopping of units, i.e., EirGrid’s 1/4-hour
data understate the CO2 emissions/kWh.
-
CO2 emissions reduction is secondary, as there are other reasons for
building out wind energy, such as the Brussels’ mandated renewable
energy percentages that provide Ireland with subsidies for wind turbine
facilities.
- Ireland wants to reduce its fuel imports and increase its wind energy exports to Britain.
Changed Operations of Generating Units due to Wind Energy:
A greater wind energy percent on the grid requires a greater capacity
of generators to be in starting/stopping mode (which is less efficient),
in spinning mode (which produces no energy, but emits CO2, as an idling
car), in decreased part-load mode (which is less efficient), and in
part-load-ramping mode (which is less efficient). The net result is
increased fuel consumption/kWh and CO2 emissions/kWh of the fossil units
that significantly offsets the fuel and CO2 emissions that wind energy
was meant to reduce.
Nevertheless,
government officials and wind energy promoters usually claim (without
any measurements) one MWh of “clean” wind energy offsets one MWh of
“dirty” fossil fuel energy and its associated CO2, i.e., a 1 : 1 ratio.
However,
analysis of the November 2010 to August 2011 EirGrid grid operations
data shows that at a wind energy penetration of 12.6%, the average
efficiency of reducing CO2 emissions is about 70%, i.e., a ratio 1 :
0.7, for that 10-month period.
See Table 5 in http://www.clepair.net/IerlandUdo.html
This
ratio would be further reduced to about 1 : 0.6, or less, if the CO2
emissions from increased spinning and start/stop operations, efficiency
decreases due to ramping, less than optimum scheduling of generating
units and increased line losses were included.
See Figure 2 in http://www.clepair.net/Udo-okt-e.html
Note:
Ratios of 1 : 0.6, or less, may occur, if coal plants of grids
dominated by energy from coal, as in Texas, Colorado, etc., are
quick-ramped for balancing wind energy, which may destabilize their
combustion control systems causing extra fuel consumption, CO2 emissions
and NOx emissions/kWh, and destabilize their air quality control
systems causing extra particulate and SOx emissions/kWh.
http://docs.wind-watch.org/BENTEK-How-Less-Became-More.pdf
The
above ratios are not anywhere near the 1: 1 ratio claimed by government
officials and wind energy promoters. The above variations of the CO2
percentages are largely due to the heat rates, Btu/kWh, of the
combinations of CCGTs and OCGTs selected by the grid operator during
wind energy balancing.
The
fit lines of the scatter diagrams of CO2 intensity, gram/kWh, versus
wind energy, %, show increasing CO2 emissions/kWh as wind energy percent
increases. Where the fit line intersects the Y-axis, i.e., no wind
energy, is the lowest CO2 emissions/kWh.
This
appears entirely reasonable to power system engineers who know the more
their power generators are operated in part-load-ramping mode, the less
efficient they become and the less efficient the whole grid becomes.
Just
as a car, if operated at 20 mph, then accelerated to 50 mph and back
down again a few hundred times during a 24-hour trip would use more gas
and pollute more, so would the balancing CCGTs and OCGTs. However, gas
turbines have even greater degradations of heat rates, Btu/kWh, when
operating in part-load-ramping mode than gasoline engines. The extra
fuel consumed and extra CO2 emitted by the gas turbines are so much that
they significantly offset what wind energy was meant to reduce.
Note:
Ratios of 1 : 0.95 may occur, If hydro plants are quick-ramped for
balancing wind energy, as in Norway and Sweden which absorb most of
Danish wind energy in excess of Danish demand, thereby maintaining their
reservoirs at higher levels than they would have been. Other than the
CO2 emissions associated with transmission losses, little additional CO2
emissions occur due to wind energy balancing.
Note:
Ratios of 1 : 0.95 are likely to occur due to energy efficiency
measures. EE is the low-hanging fruit, has not scratched the surface, is
preferred to wind energy, because:
EE
is invisible, AND it does not make noise, AND it does not destroy
pristine ridge lines/upset mountain water runoffs, AND it would reduce
CO2, NOx, SOx and particulates more effectively than wind energy, AND it
would not require the transmission network buildouts for wind energy,
AND it would slow electric rate increases, AND it would slow fuel cost
increases, AND it would slow depletion of fuel resources, AND it would
create 3 times the domestic jobs and reduce 3-5 times the Btus and CO2
per invested dollar than wind energy, AND all the technologies are fully
developed, AND it would end the wasteful subsidizing of expensive wind
energy tax-shelters mostly benefitting the top 1% at the expense of the
other 99%, AND it would be more democratic/equitable, AND it would do
all this without the public resistance and controversies associated with
wind energy.
The analysis of the EirGrid data also found:
-
the greater the wind energy percent on the grid, the lower the ratio,
i.e., adding more wind energy becomes less and less effective for CO2
emissions reduction
-
at very high wind energy percent on the grid, the ratio will ultimately
go to zero and then become negative, i.e., adding more wind energy to
the grid will INCREASE CO2 emissions.
See Figure 1 in http://www.clepair.net/Udo-okt-e.html
In
general, for grids with low ANNUAL wind energy percent, such as the
0.6% on the New England grid, the ratio is about 1 : 0.95 during greater
wind speed periods. The ratio will decrease as more wind energy is
added to the grid.
The
above study results could only be determined because EirGrid publishes
real-time, 1/4- hour grid operations data. Almost all grid operators
HAVE those data, but do not publish them because:
- they are not required to, or they do not want to.
- wind turbine owners claim their data are proprietary.
- wind turbine owners have lobbied legislatures to maintain the “do-not-tell” status quo.
Because
the real-time, 1/4-hr data is generally not made public, it became
possible for government leaders and wind energy promoters to make
unrealistic CO2 emissions reduction claims, such as the 1 : 1 ratio,
using studies based on estimates, probabilities, algorithms,
assumptions, grid operations modeling, weather and wind speed forecasts,
etc., and thereby maintain a spell of deception and delusion regarding
the claimed CO2 emission reduction benefits of wind energy.
The
above shows too many renewable energy certificates, RECs, are being
granted to wind energy producers than is warranted based on their actual
CO2 emissions reduction.
The
lay public has been led to believe by government leaders and wind
energy promoters that wind energy is “fighting climate change and global
warming”. It turns out the net effect is much less.
http://theenergycollective.com/willem-post/64492/wind-energy-reduces-co2-emissions-few-percent
http://www.clepair.net/IerlandUdo.html
http://docs.wind-watch.org/BENTEK-How-Less-Became-More.pdf
http://www.clepair.net/windSchiphol.html
http://www.clepair.net/Udo-okt-e.html
http://www.clepair.net/Udo-curtail201205.html
Additional References Showing a Lack of CO2 Emissions Reductions:
However, as more grids now have significant annual wind energy
percentages, their grid operations data, such as those published by
EirGrid, show these studies appear to have significantly overestimated
the CO2 emission reduction/kWh. See below.
Bentek Energy LLC, How Less Became More: Wind, Power and Unintended Consequences in the Colorado Energy Market, http://www.bentekenergy.com/WindCoalandGasStudy.aspx
Institute for Energy Research, June 2010: http://www.instituteforenergyresearch.org/2010/06/23/wind-integration-does-it-reduce-pollution-and-greenhouse-gas-emissions/
Argonne National Laboratory, System-Wide Emissions Implications of Increased Wind Power Penetration, March 5, 2012; http://pubs.acs.org/doi/abs/10.1021/es2038432
Argonne National Laboratory, Grid realities cancel out some of wind power’s carbon savings, May 29, 2012; http://www.anl.gov/articles/grid-realities-cancel-out-some-wind-power-s-carbon-savings
Forbes, Wind Power May Not Reduce Carbon Emissions As Expected: Argonne, May 30, 2012; http://www.forbes.com/sites/jeffmcmahon/2012/05/30/wind-power-may-not-reduce-carbon-emissions-argonne/
Aol Energy, A Brave New World: Renewable Energy Without Subsidies, June 6, 2012; http://energy.aol.com/2012/06/06/a-brave-new-world-renewable-energy-without-subsidies/#page1?icid=apb1
Bloomberg, Renewable-Power Boom Leaves Nations Without Backup, Report Shows, June 8, 2012; http://www.bloomberg.com/news/2012-06-08/renewable-power-boom-leaves-nations-without-backup-report-shows.html
Climate Wire, Renewable Energy: Wind power may not reduce carbon emissions as expected, June 1, 2012; http://www.eenews.net/climatewire/2012/06/01/8
http://theenergycollective.com/willem-post/89476/wind-energy-co2-emissions-are-overstated
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