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Wind Energy Does Little to Reduce CO2 Emissions

Here is an important article regarding wind energy not reducing CO2 on grids. The article is based on 2 studies using measured, real-time operations data of the Colorado, Texas and Irish grids, all with significant wind penetration. The studies show increases of CO2/kWh due to adding wind energy to electric grids.

For some years wind turbines were presented to the public as renewable energy producers that would reduce the CO2 emissions from fossil plants, because less fossil fuels would be burnt, while making the US less dependent on energy imports from unstable regions.

Wind turbine vendors, project developers, financiers, trade organizations, etc., popularized wind energy as saving the planet from global warming with PR campaigns that claimed there would be significant CO2 reductions/kWh, that capital costs/MW would decrease, and that wind energy costs/kWh would be at grid parity in the near future.

Apparently many people, including many legislators and the US president, believed it all, because a fear-driven, heavily-subsidized, multi-billion dollar build-out of wind turbine facilities occurred.

End December 2010 installed capacity: total US 41400 MW; top 5 states: Texas 10085 Mw, Iowa 3675 MW, California 3177 MW, Minnesota 2192 MW, Washington 2104 MW. Estimated capital cost about $70 billion, mostly during the past 10 years.

US 2010 wind energy production: 2.3% of total production, or 94,650 GWh

It may take another 10 years to install the next 40,000 MW and have 4.6% wind energy. However, there may not be sufficient capital, because the US fiscal and monetary conditions are not favorable.

After skepticism was expressed by power systems engineers in the US, the UK, Denmark, the Netherlands, etc., about claims regarding CO2 reductions/kWh due to wind energy for at least the past five years, several studies were performed which have accurately quantified the CO2 reductions/kWh based on measured operations data of the grids of Colorado, Texas and Ireland, all with significant wind energy penetration.

ERCOT of Texas, Public Service of Colorado, and EirGrid of Ireland are three grid operators that publish 1/4-hour or 1-hour operations data of relevant parameters that can be used to analyze the effects of wind energy on the operations of the other plants (coal, nuclear, hydro, gas) on their grids.


The Bentek study of the Colorado and Texas grids, based on measured hourly (in case of Colorado) and 1/4-hourly (in case of Texas) power plant operations data of fuel consumption and CO2, NOx and SOx emissions, proved that wind energy on the grid needs to be:

– balanced with energy from other plants, preferably quick-ramping CCGTs and OCGTs, to ensure grid stability and,

– that this balancing produces more CO2/kWh, more NOx/kWh, and more SOx/kWh (from coal plants on the grid), and uses more fuel/kWh with wind energy on the grid than without.

The balancing plants, usually consisting of quick-ramping gas turbines or hydro plants, would need to ramp down when wind energy surges and ramp up when wind energy ebbs to ensure a near-perfect balance of supply and demand is maintained on the grid. The balance needs to be maintained to minimize excessive frequency and voltage deviations from target values to avoid brownouts and blackouts and to avoid overloads.

The balancing plants would need to operate at a percent of rated output to be able to ramp up and down. Such operation is very inefficient for gas turbines and ramping up and down at a percent of rated output is even less efficient. This results in significantly increased Btus/kWh and increased CO2 and NOx emissions/kWh.

When coal plants are used as wind energy balancing plants, as is the case with Colorado and Texas, the rapid up and down ramping at part-load causes their combustion systems (designed for optimum, steady operation near rated output) to become unstable, and because the up and down ramping causes the chemical composition of the flue gas to vary, the scrubber-based air pollution control systems (designed for optimum, steady operation near rated output) also become unstable as the required stoichiometric chemical ratios cannot be maintained in a timely manner. The up and down ramping increases wear and rear of equipment and shortens useful service lives, just as with a car.


Public Service of Colorado, PSCO, owns insufficient gas-fired CCGT capacity for balancing wind energy on its grid. As a result PSCO is attempting to use its own coal plants for balancing for which they were not designed and for which they are highly unsuitable. The results have been significantly increased pollution and CO2, NOx and SOx emissions/kWh.

The heat rate of a coal plant operated near rated output it is about 10,500 Btu/kWh for power delivered to the grid. It is lowest near rated output and highest at very low outputs. If a plant is rapidly ramped up and down in balancing mode at a percent of rated output, its heat rate rises. See Pages 26, 28, 35, 41 of the Bentek study.

On Page 28, the top graph covering all PSCO coal plants shows small heat rate changes with wind power outputs during 2006. The bottom graph shows greater heat rate changes with wind power outputs during 2008, because during the 2006-2008 period 775 MW of wind facilities was added. For the individual PSCO plants doing most of the balancing, the heat rate changes are much higher.

On Page 26, during a coal plant ramp down of 30% from a steady operating state to comply with the state must-take mandate, the heat rate rose at much as 38%.

On Page 35, during coal and gas plant ramp downs, the Area Control Error, ACE, shows significant instability when wind power output increased from 200 to 800 MW in 3.5 hours and decreased to 200 MW during the next 1.5 hours. The design ramp rates, MW per minute, of some plants were exceeded.

On Page 41, during coal plant balancing across the PSCO system due to a wind event, emissions, reported to the EPA for every hour, showed increased emissions of 70,141 pounds of SOX (23% of total PSCO coal emissions); 72,658 pounds of NOX (27%) and 1,297 tons of CO2 (2%) than if the wind event had been absent.

Those increases of CO, CO2, NOX, SOX and particulate per kWh are due to instabilities of the combustion process during balancing; the combustion process can ramp up and down, but slowly. As the varying concentration of the constituents in the flue gases enter the air quality control system, it cannot vary its chemical stoichiometric ratios quickly enough to remove the SOX below EPA-required values. These instabilities persist well beyond each significant wind event.

PSCO does not release 1/4-hourly wind power generation data; its “proprietary”. Such information is critical for any accurate analysis and comparison of alternatives to reduce such emissions. PSCO deliberately withholding such information is inexcusable and harms progress regarding global warming.


The Texas grid in mostly independent from the rest of the US grids; the grid is operated by ERCOT. The grid has the following capacity mix: Gas 44,368 MW (58%), Coal 17,530 MW (23%), Wind 9,410 MW (12% – end 2009), Nuclear 5,091 MW (7%). Generation in 2009 was about 300 TWh. By fuel type: Coal 111.4 TWh, Gas CCGT 98.9 TWh, Gas OCGT 29.4 TWh, Nuclear 41.3 TWh, Wind 18.7 TWh.  Summer peak of 63,400 MW is high due to air conditioning demand.

Wind provides 5 to 8% of the average generation overall, depending on the season. Its night contribution rises from 6% (summer) to 10% (spring). Texas capacity CF = 18.7 TWh/yr/{(9,410 + 7,118)/2) MW x 8,760 hr/yr)} = 0.258. Texas has excellent winds and should have a statewide CF of 0.30 or greater. Explanations for the low CF likely are:

– grid operator ERCOT requires significant curtailment of wind energy to stabilize the grid.

– vendors, developers and financiers of wind power facilities, eager to cash in on subsidies before deadlines, installed some wind turbine facilities before adequate transmission capacity was installed to transmit their wind output to urban areas.

Much of the gas-fired capacity consists of CCGTs that are owned by IPPs (independent power producers) which sell their power to utilities under PPAs (power purchase agreements). That capacity is not utility-owned and therefore not available for balancing to accommodate the output of more than 10,000 MW of wind power facilities. Instead, utilities are attempting to use coal plants for balancing for which they were not designed. The results have been significantly increased pollution and CO2 emissions.

Unlike PSCO, ERCOT requires reporting of fuel consumption by fuel type and power generation by technology type every 15 minutes. The 2007, 2008, 2009 data shows rising amplitude and frequency of balancing operations as wind energy penetration increased. In 2009, the same coal plants were cycled up to 300 MW/cycle about 1,307 times (up from 779 in 2007) and more than 1,000 MW/cycle about 284 times (up from 63 in 2007). The only change? Increased wind energy penetration.

On Page 69:  The ERCOT balancing of plants to accommodate wind energy produced results similar to the PSCO system; increased balancing resulted in significantly more SOX and NOX emissions than if wind energy had been absent. Any CO2 emission reductions were minimal at best, due to the significantly degraded heat rates of the balancing plants. See websites.


A new report by Dr. Fred Udo, a Dutch engineer, describes his analysis of the CO2 emissions of the Irish electric grid, managed by EirGrid, which posts on its website 1/4-hour operations data of total electricity demand, wind energy and CO2 emissions on the Irish grid. Analysis of the data proves wind energy reduces the CO2 emissions by just a few percent.

For example:

During April 2011, 12% wind energy on the Irish grid reduces its CO2/kWh by 4%,

During April 1st and 2nd, 28% reduces it by 1%,

During April 3rd and 4th, 34% reduces it by 6%,

During April 4th, 5th and 6th, 30% reduces it by 3%,

The above reductions are not anywhere near to what is claimed by the PR of wind energy proponents.

The above variations of the CO2 percentages are largely due to the heat rates, Btu/kWh, of the combination of CCGTs and OCGTs selected by the grid operator during wind energy balancing. See website.

The fit lines of the scatter diagrams of CO2 intensity, gram/kWh, versus wind energy penetration, %, show increasing CO2/kWh as wind energy increases. Where the fit line intersects the Y-axis is the lowest CO2/kWh, i.e., no wind energy.

This appears entirely reasonable to power engineers who know the more their power generators are ramped up and down the less efficient they become. This means greater wind energy penetration produces greater up and down ramping amplitudes of wind energy to be compensated for by balancing plants and more balancing plant capacity is required to be in part-load, up/down ramping mode, which increases their CO2/kWh, and, according to the scatter diagrams of the Dr. Fred Udo report, the CO2/kWh of the entire grid.

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, except gas turbines have even greater degradations of heat rates, Btu/kWh, when operating at part-load AND ramping than gasoline engines. The extra fuel consumed and CO2 emitted are so much that they mostly offset the fuel savings and CO2 reduction due to wind energy, according to analysis of the EirGrid data posted on its website

Note: Paste this URL in the left field of your browser window to access the site.

The following is a direct quote from the site of EirGrid:

“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“

The heat rate degradation due to ramping down the fossil-fired plants with wind energy surges and ramping up with wind energy ebbs is not accounted for in the above calculation method; i.e., the gridwide CO2 emissions posted on the EirGrid website are understated, i.e., the above small reductions of CO2/kWh will likely disappear, or become increases.

This is devastating news for wind energy proponents who have been claiming more and more wind reduces CO2/kWh more and more, exactly opposite of the results of Dr. Fred Udo’s analysis of the EirGrid real time, 1/4-hour operations data.

Wind proponents made their claims without any substantiation based on 1/4-hour operations data. They could not have, because such data has been available only during the past 2-3 years.

The above results has very significant policy implications regarding the continued promotion of wind energy through various subsidizing schemes.

The above is only part of the story. The other part is capital costs.


The total capital cost of the wind turbine facilities (onshore about $2,000/kW, offshore about $4,200/kW), PLUS the capital cost of the new quick-ramping balancing plants required at higher wind energy penetrations (many grids do not have enough of such capacity), PLUS the capital cost of extensive grid modifications, including new HVDC lines on 80 to 135 foot-tall steel structures to transmit the wind energy from windy areas to population centers is about 2 to 3 times greater than the total capital cost of a capacity of 60% efficient CCGTs (about $1,250/kW) that would produce, in base-loaded mode, near rated output, the same quantity of energy, use about the same quantity of fuel/kWh and emit about the same quantity of CO2/kWh than the above (wind energy + balancing energy) combination, but do it at a much lower cost/kWh (see next paragraph), AND at minimal transmission system changes (the new CCGT plants would be located at or near the same sites as existing coal plants), AND at minimal impacts on quality of life (noise and infrasound, visuals, social unrest, psychological), property values and the environment.

See websites.

The US Energy Information Administration projects levelized production costs (national averages, excluding subsidies) of NEW plants coming on line in 2016 as follows (2009$) :

Offshore wind $0.243/kWh, PV solar $0.211/kWh (higher in marginal solar areas, such as New England), Onshore wind $0.096/kWh (higher in marginal wind areas with greater capital and O&M costs, such as on ridge lines in New England), Conventional coal (base-loaded) $0.095/kWh, Advanced CCGT (base-loaded) $0.0631/kWh.…


The above begs the question: If wind energy reduces CO2 by so very little/kWh, or not at all, or increases it, AND requires so much capital/MW to implement, AND produces energy at such a high cost/kWh, AND has such huge adverse impacts on quality of life (noise and infrasound, visuals, social unrest, psychological), property values and the environment, why are we, as a nation, making ourselves even less efficient relative to our competitors by this slavish, lemming-like pursuit of expensive wind energy?

Could it be that the Wall Street elites see the 30% federal cash grants, accelerated write-offs, generous feed-in tariffs and renewable energy credits as major tax shelters and long-term income streams for their high-income clients, all at the expense of the Main Street economy?

Wind energy proponents often use Denmark as the model to emulate. However, Denmark is in the fortunate position of having a large capacity of hydro plants of Norway and Sweden available for balancing wind energy; i.e., other grids with little or no hydro plants cannot use Denmark as a model.

Wind energy reduces the quality of life, health and psychological well-being of people who live near wind turbines. During the past 5 years, Denmark has stopped adding to its ONSHORE wind turbines for exactly these reasons.

Due to demonstrations by the Danes during at least the past 5 years, the government finally decided in August 2010 that any future wind turbines will be OFFSHORE and beyond the horizon. That is a huge admission on part of the Danish government. i.e., wind turbines near people have become an anathema in Denmark. A similar development is shaping up in the Netherlands.


The below article describes an economically and environmentally more attractive alternative to wind energy that is based on 60% efficient CCGTs.

The new “GE FlexEfficiency 50″ plant has a capacity of 510 MW and a 61% efficiency at rated output. Its design is based on a unit that has performed utility-scale power generation for decades. The plant fits on about a 10-acre site; i.e., minimal visual impact.

It is quick-starting: from a cold start, it reaches its rated output in about one hour. Its average efficiency is about 60% from rated output to 87% of rated output (444 MW) and about 58% to 40% of rated output (204 MW). It can be ramped at 50 MW/minute. CCGTs are usually not operated at less than 40% of rated output because of very high heat rates, Btu/kWh.

The GE unit is designed to efficiently produce electric energy in base-loaded mode and in daily-demand-following mode which implies 365 cycles per year.

Its high ramp rate enables it to also function as a balancing plant to accommodate the variable energy from wind turbine and solar facilities. However, such use would significantly increase wear and tear and shorten the useful service life of the units, because they would have to ramp up and down hundreds of times per day to follow the wind surges and ebbs.

See websites.

About Willem Post Willem Post, BSME New Jersey Institute of Technology, MSME Rensselaer Polytechnic Institute, MBA, University of Connecticut. P.E. Connecticut. Consulting Engineer and Project Manager. Performed feasibility studies, wrote master plans, evaluated and performed designs for incineration systems, air pollution control systems, utility and industrial power plants, and integrated energy systems for campus-style building complexes. Currently specializing in energy efficiency of buildings and building systems.

One Comment

  1. Michael Goggin, AWEA says:

    It is unfortunate to see people continuing to propagate the myth that wind energy doesn’t significantly reduce carbon dioxide emissions. There’s a large, well-established body of empirical evidence showing that as states like Colorado and Texas have added wind energy to their grids, their carbon dioxide emissions decreased by even more than had been expected. That data was used to directly refute the Bentek study even before the study came out 18 months ago, and the Bentek study has since been widely dismissed as the fossil fuel industry attack piece that it is, except for continued efforts by the fossil fuel industry to continue spreading its misinformation. There are also dozens of power system studies conducted by utilities, government agencies, and independent grid operators showing that adding wind energy to the grid results in larger emissions savings than the 1:1 offset commonly expected, largely because additional wind energy forces inflexible coal plants to be taken offline for extended periods of time and the share of their output not directly replaced by wind is replaced with more flexible and cleaner natural gas generation. I won’t waste time repeating the full discrediting of the Bentek study that has already taken place, but you can read through that with the numerous links at the bottom of my post.

    Ireland emissions: I was interested to see the Fred Udo piece mentioned in your post as I hadn’t seen that yet. It only took a few minutes to unravel the statistical trick Udo was using to get his results, which might explain why his analysis wasn’t published in a peer-reviewed journal and rather appears on an obscure Dutch anti-wind website. This appears to be a classic case of a lurking (or confounding) variable being used to misleadingly present correlation as causality; a comparable example is arguing that cigarette lighters cause lung disease since people who buy them tend to develop lung disease. In this case the lurking variable that is the actual causal factor appears to be cold weather and its impact on heating demand, data that Udo should have had access to but that (for reasons you can speculate) he chose not to use in his correlational analysis.

    What tipped me off was in part 3, Figure 3 of his text, where Udo called out an event in Ireland around June 9-12 2011 when the carbon intensity of Ireland’s electricity production surged. I was curious what might have caused that event so, on a hunch, I pulled weather records for Ireland. Sure enough, there was an abnormally cold spell when temperatures fell into the 30’s and 40’s F, 10 to 20 degrees below normal for that time of year. Aha! Cold temperatures drive heating demand, forcing Ireland’s numerous fossil-fired combined heat and power (CHP) plants to fire up and run at a high level of heat production (and subsequently more emissions/MWh since CHP plants relative to the rest of the fleet are not optimized for electricity production, and CHP plants being run to produce maximum heat are not being operated in a way that is optimized for electricity production; moreover, it appears that the emissions associated with heat production are rolled into the data that Udo is using, so a CHP plant producing only or mostly heat and little or no electricity under cold conditions like these would score at infinity CO2/MWh). A smaller possible factor is that higher demand for electric heating drives higher merit order, less efficient fossil plants to operate to meet the abnormally high electric demand.

    As one would expect, cold spells and home heating demand often correlate with high wind speeds, which is how Udo was able to draw his false conclusion that wind was the causal factor. Sure enough, a closer examination of the spikes in emissions/MWh in Udo’s data show that all are associated with cold spells, and only some are associated with an increase in wind output. It doesn’t take a statistician to tell you which is the causal factor in that relationship. Had Udo himself been more interested in finding the actual causal relationship at play here, he might have noted that the correlations between wind output and emissions intensity varied widely from month to month (as one would expect for weather-driven seasonal changes in electric demand), usually a strong indication that another variable may be the actual causal factor.
    I should also point out that, contrary to Udo’s claims, EirGrid’s method of calculating the emissions savings of wind is accurate. The plant-specific heat rate curve that they are using would account for all of the impacts wind energy would have on the efficiency of the fossil fleets under all operating conditions.

    Cost: To touch briefly on the cost issue, I’d suggest consulting with any of various independent analysts about how the cost of wind energy compares against other sources of electricity – some links are below. As is noted, the cost of wind energy has fallen drastically in recent years, though that hasn’t stopped some from using old data to perpetuate the myth that wind energy is significantly more expensive that alternatives. FERC’s collection of signed power purchase agreements showing the actual $/MWh costs for hundreds of generating projects from different electricity sources also backs up the conclusion that wind energy is very affordable. Moreover, when one looks at the history of extreme volatility in fossil fuel prices and the inevitability that fossil fuel prices are going to vary and likely increase in the future, wind energy looks even more attractive as a way to lock in an energy resource that will continue to have zero fuel costs for the life of the plant. Of course, that doesn’t even begin to factor in the massive environmental, public health, and societal costs of other sources of electricity production.

    Miscellaneous: On the topics of infrasound, property values, and other false claims used to attack wind energy, I’d suggest reading the consensus of scientists that all of those concerns are unfounded – the links are below. Of course, the most important point is that when compared to the massive environmental, public health, and quality of life impacts of other energy resources, wind energy and other renewables are far and away the best option for powering our society.
    As mentioned earlier, summaries of the evidence refuting the Bentek studies:

    Michael Goggin,
    American Wind Energy Association

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