In my previous article, “Integrating Renewables: Have Policymakers Faced the Realities”, I concluded that introducing large amounts of new renewable sources into the electricity system does not contribute to society’s goals, and that the only argument for the current renewables push is political expediency driven by prevailing conventional wisdom.
Two aspects warrant further detail, especially with respect to utility-scale wind plants: CO2 emissions and capacity value. The issues surrounding CO2 emissions are obscured due to the lack of the necessary published information. Papers claiming that wind power reduces CO2 emissions are not convincing for a variety of reasons (examples are: Komanoff, Gross et al and Milligan et al). The issues surrounding appropriate comparison of costs are also shrouded in the complexities of electricity market pricing. In this connection, capacity value is a poorly understood but vital concept.
Drawing upon the recent literature, this present paper argues that wind plants do not reduce CO2 emissions and, lacking capacity value, do not make any worthwhile contribution to electricity supply.
This section provides three recent analyses of CO2 emissions:
- The le Pair and de Groot study for the Netherlands
- The Bentek Energy study for Colorado and Texas
- The results from my calculator for these jurisdictions (Calculator)
Le Pair and de Groot apply derived formulae to determine fossil fuel savings (and hence CO2 emissions savings) based on actual fossil fuel inputs for electricity production in the Netherlands.
Bentek analyzes detailed information on increases in coal plant cycling since the introduction of wind in Colorado. Their study is restricted to using a limited number of wind events, because the Public Service Company of Colorado (PSCO) does not publish even hourly wind production. The available information (from PSCO materials) provides limited wind-related actual impact on emissions, which Bentek uses to draw general conclusions. To validate the Colorado findings, Bentek applies the same analysis approach to Texas, using information from the Electricity Reliability Council of Texas (ERCOT), which reports wind production at 15-minute intervals. The Texas analysis not only provides validation of the PSCO analysis, but also conveniently adds experience from a third jurisdiction.
The Calculator is a general model of the interaction between an amount of wind generation in an electricity system and the fossil fuel plants (coal and gas) involved in mirroring wind’s volatility. It calculates the associated fossil fuel consumption and CO2 emissions with and without the presence of wind.
At the wind penetrations involved (3-6%), the studies show that there are no fossil fuel or CO2 emissions savings, and in some cases increases are indicated. For all three, the Netherlands, Colorado and Texas the studies report savings close to zero percent of the emissions for the total electricity system. The individual results are summarized below:
Le Pair and de Groot show that when the entire fossil fuel fleet efficiency is reduced by about 2% due to the presence of wind, the fossil fuel saving is zero. This is the calculated efficiency reduction in the fossil fuel fleet for the Netherlands for a wind penetration of about 3% based on the published fossil fuel input and electricity production information. Their conclusions include the following:
The use of wind energy for electricity generation in combination with the requirement for fossil fuel powered stations to compensate for wind fluctuations can easily lead to loss of the expected saving in fuel use and CO2 emission. In addition, the conventional stations will be subject to accelerated wear and tear.
It is recommended to get an accurate and quantitative insight into these extra effects before society sets out to apply wind energy on a large scale. All producers must be required to publish data on the efficiency effects and fuel use when wind energy is added on.
Colorado and Texas
The study by Bentek Energy, aptly named “How Less Became More: Wind, Power and Unintended Consequences in the Colorado Energy Market”, is a ground breaking analysis of the effects of the introduction of wind power into an electricity system. The study is based on actual results for the PSCO system in Colorado and ERCOT in Texas and their overarching conclusion is that there are unintended consequences to the implementation of Renewable Portfolio Standards (RPS). One of the key findings is:
“Contrary to their stated goals, implementation of RPS in Colorado and Texas appear to be adding to the air pollution problem, especially in areas where older plants are cycled more frequently.”
Fossil Fuel/CO2 Calculator
My recent four-part series at MasterResource, “Wind Integration Realities,” reviewed the above two studies and compares their results as well as to those of my Calculator for the same conditions.
The Calculator uses information provided in a paper by White to determine the increase in fossil fuel consumption and CO2 emissions due to the required cycling of wind balancing fossil fuel plants. The basis for the calculator is the relationship between CO2 emissions and fossil fuel plant efficiency loss for CCGT, OCGT and a sample bituminous coal plant shown in Figure 1.
Table 1 shows the increases in CO2 emissions and fossil fuel consumption (as it is in direct proportion to the CO2 emissions) of the three plant types for a range of efficiency losses derived from Figure 1.
There is inevitably some controversy about these efficiency-emissions trade-offs. There are studies that show these effects are small, but close scrutiny finds them to be limited or lacking in some important way. Studies referenced above describe many of these shortcomings. In addition:
- Relying on macro analyses of a nation’s energy use, with the assumption that the introduction of wind provides little or no inefficiencies at lower levels of analysis
- Ignoring the profile of the fossil fuel plant types needed with and without the presence of wind
This is the main reason why I emphasize the need for a comprehensive framework at the appropriate level, and have attempted to provide one in the calculator. The next step remains to be equally comprehensive analyses based on actual real-time information within a similar framework to clearly demonstrate the effects.
Comparison of Results
Figure 2 shows the CO2 emissions savings based on two approaches to the replacement of a portion of the coal plants in all three jurisdictions.
- Introduce wind plants, which produce no CO2 emissions at the point of wind electricity generation.
- Do not introduce wind and use efficient gas plants (CCGT) to replace coal production.
For comparison purposes, the wind plant capacity is used as a reference point. Wind production is based on the average over a year. Production from other energy sources (coal and gas here) used in the comparison is the wind production at 100% of capacity minus the wind average over a year. This is a useful basis for comparison, because in real-time wind can vary over the full range of its capacity. The sum of these two is the coal plant production being displaced.
The CO2 emissions savings shown are percentages of the total emissions for the electricity system. Percentages will increase (further positively and negatively) for higher wind implementations, and in the case of replacing coal with gas alone for higher implementations of gas plants. The four columns in each case represent:
- Column One – The typical wind proponent claim. Their view is that the average wind production over time replaces the CO2 emissions from the same production of the coal plant(s). This view ignores the loss in efficiency (resulting in increased fossil fuel consumption and CO2 emissions) for the plants that are frequently cycled up and down to mirror wind’s highly variable, real-time production. It is purposely shown as somewhat washed out because it is not realizable. Column two shows the reality. It is coincidental that all column ones are at about 6% of total emissions and is due to the combination of the specific wind capacity factors and the proportion of coal and wind in each jurisdiction.
- Column Two – Study results. This shows the results based on actual experience in the three jurisdictions studied. The Netherlands result is zero. The mid-points of the ranges for PSCO and ERCOT were used.
- Column Three – Calculator results
- Column Four – High efficiency gas plants only. This shows the result of not implementing wind and using high efficiency gas plants to replace the same coal production. The variation in percentage reductions in column four is due to the underlying proportion of coal and gas. Colorado has the highest reliance on coal and CO2 emissions are greater in proportion to the other two. As a result, the same level of reduction is less as a percentage.
The two studies and calculator results demonstrate that, with the introduction of wind plants, CO2 emissions are not reduced, but are increased and a straight substitution of gas for coal production is a far superior strategy.
This is by no means the last word, as all three analysis approaches call for comprehensive and objective studies, based on complete information, to confirm their findings.
In the previous article, I described capacity value as follows:
“In electricity generation and use, which is a real-time matter, one of the most important, yet most overlooked factors is capacity value. This represents the ability of electricity generation means to be dispatchable, that is capacity available on a real time basis, as opposed to a statistical expectation over time. For most plant types this approaches 100 percent and must be so. Values for hydro and solar, especially thermal solar, are complicated and not assessed here. Wind power has zero capacity value because of the extensive, uncontrollable, stochastic nature of the fuel supply.”
In other words, for electrical energy to be useful we must be able to switch it on and off as needed and rely on it being available during the period of use. To accomplish this, capacity (in this context capacity and power are interchangeable terms) must be reliably available on a continuous basis. This is as opposed to wind power, which is available only randomly and in varying degrees over time. Statistical expectations of this are not meaningful. This cannot be over-emphasized, as electricity is a vital resource for many of our activities and continued well-being. Further, unlike most resources, electricity cannot be stored, and in most applications, in its absence, substitution of some other energy source is not feasible.
For utility-scale wind plants to have value, they must provide renewable power. This means wind capacity must be reliably available on demand and throughout the period of use, and it is not. This is why it was separated from conventional generation sources in Table 1 of the previous article, and is characterized as having no capacity value. Even at the disadvantageous increased costs, it cannot be directly compared to the conventional generation sources as inclusion in the same table implies.
In summary, reliable capacity is the means by which useful electrical energy is provided. In its absence, the availability of energy, regardless of the reliability of the energy source, is of very little, if any, value.
Wind proponents acknowledge wind’s capacity inadequacies and make the seductive argument, based on the erroneous assumption that it is “clean” or “green”, that it must be used if, as and when it becomes available. As such, they maintain that wind makes an energy contribution that is, in itself, useful. This does not bear close examination.
There are two important components for pricing electricity in wholesale electricity markets: capacity and energy payments. Capacity considerations and payments are a form of insurance against curtailment as described by McCullough.
Capacity payment is intended to provide financial support for the fixed costs of a project, development costs, and the equity return on the project sponsor’s investment. An important underlying proviso is that electricity can be reliably produced at agreed-upon levels. Energy payment is intended to cover the variable operating costs, such as fuel and variable operating and maintenance expenses, and is based on the electricity delivered.
Clearing prices in the spot, or real-time balancing, market tend to reflect variable operating costs and wind has a major cost advantage over other market participants, for example gas turbine plants where operating costs include gas consumption. As clearing prices are paid to all successful bidders below the clearing price, which tends to be at the level of gas plants, wind plants can obtain energy prices that also contribute to fixed costs. Separately, they may even be able to receive their full power purchase agreement prices, which can be at a substantial premium above the clearing price. Even in this market, wind cannot be relied upon and must be supported by government mandates that it must be used as available.
So, wind attempts to be an electricity market player by focusing upon the energy component. Wind project owners will likely chose to participate only in the spot electricity market, in part because of their greater inability to ensure delivery in the larger day-ahead market, except in cases where, unlike other market participants, wind non-delivery is not penalized.
As a further insight into the overall value of wind-generated electricity, in Germany there are times when customers are paid to take unneeded wind production. Note the questionable comment that this lowers rates to customers.
The absence of the ability to reduce CO2 emissions and to provide reliable capacity combines to seriously question the value of utility-scale wind in an electricity system. These are not the only two critical failures of wind.
Kent Hawkins has a BScEE and is retired.
 Hawkins K. (2010). “Integrating Renewables: Have Policymakers Faced the Realities?” USAEE Dialogue Volume 18, Number 1 – 2010.
 Komanoff, Charles (2009). “Wind Power’s Displacement of Fossil Fuels”
 Gross et al. (March 2006). “The Costs and Impacts of Intermittency: An assessment of the evidence on the costs and impacts of intermittent generation on the British electricity network”
 Milligan et al. (2009). “Wind power myths debunked”, Power and Energy Magazine, IEEE, Volume 7, Issue 6, November-December 2009, pp 89-99.
 Le Pair, C. and de Groot, K. (2010). ”The impact of wind generated electricity on fossil fuel consumption.”
 Bentek Energy LLC (2010). “How Less Became More: Wind Power and Unintended Consequences in the Colorado Energy Market.”
 Hawkins, K. (2010). “Wind Integration: Incremental Emissions from Back-Up Generation Cycling (Part V: Calculator Update).”
 Hawkins, K . (2010). “Wind Integration Realities: Case Studies of the Netherlands and of Colorado, Texas.”
 White, David, (2004). “Reduction in Carbon Dioxide Emissions: Estimating the Potential Contribution from Wind Power, Renewable Energy Foundation.”
 McCullough, Robert (1998). “Can Utility Markets Work without Capacity Prices?” Public Utilities Fortnightly.
 Hoffman, Scott L. (2008). The Law and Business of International Project Finance. Third Edition. Cambridge University Press. Section 19.07
 Linowes, Lisa (2010). “The Cape Wind Approval: It’s Not Over Yet.”
 Hutzler, Mary (2010). “Wind Integration: Does it Reduce Pollution and Greenhouse Gas Emissions?”
 Bloomberg Businessweek (2010). “Where Wind Power is Blowing Away Profits: A surplus in Germany forces utilities to pay customers to use it.”
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