Category — Integration/Firming windpower

Many claim that wind generation is beneficial because it reduces pollution emissions and does not emit carbon dioxide.  This isn’t necessarily the case. The following article explains a phenomena called cycling where the introduction of wind power into a generation system that uses carbon technologies to back-up the wind  actually reduces the energy efficiency of the carbon technologies. Recent studies  with actual data have estimated the impact of cycling on air pollution and carbon dioxide emissions.

Energy modelers evaluating the impact of legislation such as Senator Bingaman’s American Clean Energy Leadership Act and the American Power Act proposed by Senators Kerry and Lieberman should take note for their models most likely are underestimating the cost of compliance by incorrectly modeling the integration of wind power into the electricity grid.

Wind is not a new technology. It was one of our principal sources of energy, along with wood and water, prior to the carbon era. But the use of renewables in the pre-carbon age was very different from the current use of renewables. Today, people rely on energy being available 24 hours a day, 7 days a week, 365 days a year, regardless of whether the sun shines, the wind blows, or there are high or low water levels.  We now have over 1,000 gigawatts of generating plants[1], and a large and elaborate electrical grid that requires great coordination among system operators to avoid disruptions.

Also, in the pre-carbon energy era, when renewables were the sole source of energy, there were no coal-fired or natural-gas fired power plants to provide back-up power. Studies have found that the efficiency of those carbon-based plants is affected by incorporating wind energy into the system. [Read more →]

It is the irony of ironies. Taxpayer and ratepayer-forced subsidies for utility-scale windpower also subsidizes emissions of carbon dioxide (CO2). The same would be true under a national renewable portfolio standard as proposed in pending federal legislation.

Such is a vivid demonstration of the perils of unintended consequences and, to borrow a phrase, “an inconvenient truth” about wind power.

My recent four-part Wind Integration Realities reviewed two new studies, based on actual experience, that show fossil fuel consumption and CO₂ emissions are increased, not reduced, with the introduction of wind. Their results were compared as well as to those of my fossil fuel and CO₂ emissions calculator for the same conditions. The brief summary in Part IV of the series is expanded upon here for clarity of this game-changing argument.

In general, the studies show that as wind penetration increases, the effect on fossil fuel and CO₂ emissions worsens. Specifically, at wind penetrations of about 3% (as is the case in the Netherlands), the savings are zero. At 5-6% (as for Colorado and Texas) the “savings” become negative, that is, emissions actually increase due to the presence of wind power. [Read more →]

[Editor's note: This is the final post in the series reviewing studies for the Netherlands, Colorado and Texas on (elevated) fossil-fuel emissions associated with firming otherwise intermittent wind power. Part I introduced the issues. Part II showed negated emission savings for the Netherlands at current wind penetration (about 3 percent). Part III extended the Netherland's experience to the higher wind penetration in Colorado (6%) which demonstrates higher emissions. Part IV concludes with the Bentek results for Texas,which confirms those for Colorado.]

There are a number of relevant, notable characteristics of the 2008 Texas electricity production profile, 85% of which is managed by ERCOT:

• The utility portion of the total electricity production is only about 24% of the total, with independent suppliers providing 57% and CHP installations, 19%. This distribution suggests that ERCOT’s ability to balance wind production is more limited than what might first appear.
• Wind production is 5% of the total (less CHP), but a very large 17% of the utilities portion.
• A large proportion of gas production is provided by independent suppliers and CHP, 45% and 39% respectively, again likely limiting ERCOT’s ability to balance wind with gas.
• The ratio of utility gas to wind production is 192%, which suggests that this is tight if dedicated to wind balancing. This, plus high production from wind at night, explains the high degree of cycling of coal plants required.

Because of recycling events, arguably attributable to the presence of wind plants, the results are the same as for PSCO, that is, there is an increase in CO₂ emissions with the presence of wind. In ERCOT, the coal plants produced an additional CO₂ emissions in 2008 of about 0-566,000 tons over running stably without these events, and in 2009, an additional 772,000-1,102,000 tons. [Read more →]

Part I of this two-part post reviewed most of the considerations that must be understood in evaluating analyses of wind power.

Part II completes this analysis by focusing on one of the most important considerations in the wind utility debate, wind’s capacity value.  To this end, I review a paper by Gross et al, which is relied on by Komanoff, and conveniently provides an opportunity for the review of a second paper.

Wind’s Capacity Value

Komanoff uses a flawed analogy by claiming that a backup quarterback contributes value to a team even if he never plays. First, the concept of “never playing” is arguably a reasonable notion with respect to industrial wind power. Second, the analogy applies more correctly to operating reserves, which are needed to fill in for the other generation means if, and when, needed.

These operating reserves have similar characteristics to that which is being replaced, that is they provide steady reliable power at the call of the system operator (football coach). The appropriate analogy with wind would be to have a basketball player sitting on the football team bench to back up the quarterback. The basketball player has different characteristics and does not add value to the team. If you prefer, substitute a guard or tackle as the quarterback backup, but this does not change the situation. In these cases an additional, and effective, backup quarterback would have to be added to realize the “value” that Komanoff claims. Table 1 further illustrates this point.

Table 1 – Comparison of Characteristics

Table 1 illustrates the capacity value aspects of generation plants. Wind has zero capacity value just as the basketball player, guard or tackle adds no value to a football team as a backup quarterback.

Another aspect of the analogy is a backup quarterback who has an extensive, “wild” social life. [Read more →]

Is the introduction of industrial- or utility-scale wind power into our electricity systems good public policy?

This political economy question (wind power is government dependent, or it would only be a market question) hinges to a large degree on operations research, or engineering. And it is here that a hotly contested debate is going on, for it is an open question about how much wind power really displaces fossil fuels–the raison d’etre of wind subsidies in the first place.

This two-part series evaluates some of the latest approaches and considerations in this debate. One important paper published in 2009 by Charles Komanoff sees wind-for-fossil-fuel displacement as robust and is currently being cited by wind proponents in Maine. Another paper in my review is a study by Gross et al, which is relied on by Komanoff.

Part I critically evaluates Komanoff by extending the critique of Milligan et al; Part II focuses on the important consideration of electricity generation capacity value and analyzes some of aspects of the referenced Gross et al paper.

Introduction

The following is a summary of important areas of consideration in assessing documents such as Komanoff’s:

· Treatment of wind volatility

· Use of emotive and pejorative language in referring to those of an opposing opinion. On the other hand, those with the same views are treated with complimentary descriptions. This treatment raises red flags that invite closer analysis.

· Distinction made between very small and larger wind penetrations

· The realities of wind production in Denmark.

· Complete consideration of the impact on overall system capacity requirements, fossil fuel consumption and CO₂ emissions in connection with the displacing of some fossil fuel plant production with highly intermittent renewables.

· Evaluation of normal operating reserves as sufficient to act as wind shadowing/backup .

· Assumptions about the fast ramping capability of nuclear and coal-fired plants

· Assessment of wind’s capacity value

· Dependence upon a report by Gross et al, which itself is not convincing.

· Questionable arithmetic and graphical representation approaches

· Claims about the benefits of geographic diversity and the possibility of improved wind forecasting

Wind Volatility

At the beginning Komanoff quotes what he wrote a few years ago: [Read more →]

Most analyses and reviews of utility-scale, highly intermittent new renewables, especially wind power which will be the focus here, are lacking in perspective. This makes marginal aspects appear to have significance out of proportion to the very little value they represent.

A few examples are:

· A focus on the energy contribution (MWh) from wind power leads to error in assessing the contribution to electricity costs, reliability, impact on fossil fuel consumption and CO₂ emissions, transmission needs and the operation of an electricity system.

· The possibility of some improvements in wind forecasting. Given the current state of weather forecasting in general, it seems difficult to believe that wind can be forecast for short time intervals, say 24 hours in advance. In any event, even if such forecasting was possible, it does not change the need for balancing generation plants to be ramped frequently to mirror wind conditions.

· The use of statistical averaging over long time periods, which obscures the more important real time effects, to show low impacts of various aspects of introducing utility-scale wind plants.

Similarly in media coverage,

· The Economist Technology Quarterly review in the March 6, 2010, issue  highlighted the use of a technology that will allow individual wind turbines to sense the upwind conditions and adjust blades accordingly. It concludes with, “The result is a system that can already improve electricity production by 5%.” What if increased electricity production from wind actually increases fossil fuel use and CO₂ emissions, stresses the grid and other generation plants and leaves users more at risk when such production falls rapidly shortly thereafter?

· A Canadian national newspaper column proclaiming the virtues of new renewables over traditional electricity sources included a picture of a mass of electricity transmission towers to illustrate a disadvantage of existing technologies. What was not considered was that substantially increased grid deployment would be required to transport the output from new renewables in necessarily wide-spread locations to demand centers.

The result of these marginal, and often invalid, representations is to artificially make unfeasible new intermittent renewables, especially wind plants, somehow appear attractive.

USAEE Article

To assist in providing a basis for the effective evaluation of these renewable sources, my recent article in the USAEE Dialogue proposes a broad framework to assess how the available electricity generation sources, both new renewables and those that are more traditional, meet public policy objectives. These objectives are suggested to be: [Read more →]

Why has California expressed concern over the EPA holding up approvals for natural gas-fired power plants?

Answer: because state regulators know that California’s gas plants are crucial for establishing new wind and solar projects. After all, firming intermittent power sources is essential short of employing cost-prohibitive battery packs to continuously match supply to consumption.

But the analysis can go a step further. What if the gas backup actually runs more poorly in its fill-in role than if it existed in place of the wind and/or solar capacity? It does run less efficiently, in fact, creating incremental fuel use and air emissions that cancel out the fuel/emissions “savings” from wind.

Thus California should go a step further than just allowing new natural gas capacity. Regulators should rethink the rational of wind per se and block its new capacity–if only by removing the government subsidies that enable industrial wind power in the first place.

Background

Parts I to IV (links provided at end) introduced an analytic framework and calculator as a working hypothesis to assess the impact of industrial-scale wind on fossil fuel consumption and CO2 emissions. This post, Part V, provides an update to the calculator. The methodological framework has not changed, and the need for confirmation from actual performance data using extensive real-time local dispatch analysis at finely grained time intervals capable of accurately and sufficiently assessing how wind affects all the variables within the electricity system remains. In summary, the calculator:

(1) refines the emissions rates for the fuel plants modeled;

(2) improves the manner in which fossil fuel consumption is calculated, which increases the amounts previously reported; and

(3) adds a coal plant scenario.

This update also includes examples of the use of some of the input parameters to incorporate subtleties not considered in Part I and Part II. [Read more →]

Three previous posts have examined the emissions problem related to intermittent industrial windpower that is firmed up with fossil-fuel generation.

1. Part I presented a framework of the necessary considerations and an interim assessment of the effects on fossil fuel consumption and CO2 emissions until sufficiently comprehensive studies can be performed in the areas indicated. This analysis shows approximately the same gas burn and an increase in related emissions, including CO2, compared to the no-wind case.
2. Part II reviewed the simplistic, incomplete approach that is usually claimed by wind proponents and policy makers. Introducing necessary considerations shows the dramatic, negative impacts presented in Part I.
3. Part III critically reviewed an article by Milligan et al, introduced in a post on Knowledge Problem in response to Part I. The Milligan article claims negligible reductions from the theoretical maximum and contains questionable material.

This post deals with issues raised in comments and other feedback received to date. Further comments and debate on new issues will continue this series.

Reciprocating Engine Gas Plants as Wind Shadowing/Back-up

It has been suggested by Donald Hertzmark and Robert Peltier of MasterResource that reciprocating engine gas plants as wind shadowing/back-up be recognized as a partial solution to the wind emissions problem. It is also mentioned by Milligan et al.

Specifically, Midwest Energy (MWE) in Kansas has implemented a natural gas-fired plant consisting of nine 8.4 MW reciprocating gas engines to help support MWE’s 325 MW total system demand and back-up power supply in the event of a transmission outage. The MWE system will also be accommodating 49 MW of industrial wind power by the end of 2009, representing 16 per cent of the peak load in capacity terms.

An additional advantage of the small multi-engine configuration is its ability to provide back-up power for the wind component. The reciprocating engines are fast-starting and represent a spinning reserve capability, which suits them for this task, especially as individual engines can be added or removed from production as needed, as opposed to the ramping up and down of a larger unit, such as a gas turbine. It is important to note that the capacity ranges for gas turbine plants start at the top end of those for the reciprocating engine plants. The question is: is this a better solution than gas turbine plants for wind shadowing/back-up?

In addressing this, some considerations are: [Read more →]

Posts at Knowledge Problem acknowledge the range of results from Part I and Part II in my series; Katzenstein and Apt; and an article by Michael Milligan et al, Wind Power Myths Debunked, but attribute much of the differences to characteristics of the power system to which wind power is added.

However, although results will vary by jurisdiction, the differences I reported are not derived from this consideration but from general issues with respect to wind power integration. Milligan claims low reductions from the theoretical maximum (negligible to 7 per cent), apparently from Gross et al’s literature review, but this does not survive critical assessment.

The work of Katzenstein and Apt is cited in the bibliography to Part I, even though they show that as much as 75–80 per cent of the CO2 emissions reductions presently assumed by policy makers is realized. The reason for its inclusion is that the underlying approach is used in the calculator. The difference is that the calculator takes into account the limitations that they acknowledge in their article, for example:

• The realistic introduction of different generators providing “fill-in” power than that used without wind present.
• The limitation that emission and heat rate data they used did not cover all combinations of power and ramp rate.

Even so, according to the Knowledge Problem post, they have been criticized as overstating the need for backup power supplies by Mills et al, and that geographic diversity helps to smooth out variability. In an update to the post attention is drawn to the Milligan article. This article contains often used, and questionable, arguments to support the ability of wind to offset fuel consumption and the resulting emissions despite its high degree of variability. The following addresses some examples of these. [Read more →]

My initial post, “Wind Integration: Incremental Emissions from Back-Up Generation Cycling: (Part I: A Framework and Calculator),” provided an overview of a fossil fuel and CO2 emissions calculator. It showed that industrial wind plants do not provide the claimed reductions in these important areas, which brings into question their value as good public policy.

This post provides some background, a base case and the results of taking necessary additional considerations into account. The base case has two scenarios.

The first is that every MWh of wind production directly reduces the full fossil fuel consumption and CO2 emissions for every MWh of the “displaced” fossil fuel plant, which is a very simplistic view.  The second takes some limited considerations into account, which can show that as much of 85 percent of the simplistic-view savings are still achieved. Calculator runs illustrate how similar results can be produced.

Background

A major consideration is the need for fast-responding gas generation plants to mirror or shadow wind’s highly volatile output, especially during periods of high wind production. Figure 1 illustrates the concept. The gas production is shown in black and is necessary to render wind’s output useful. As the gas production is the complement of that for wind, the vertical axis has to be read in reverse for gas. While operating in a wind-shadowing/wind-mirroring backup role, the gas turbine plants consume more gas and produce more CO2 emissions per MWh than in their normal mode of operation.

Figure 1 – Illustration of the Shadowing/Backup Concept

The calculator treats these two considerations separately. The first, fossil fuel consumption (gas) per MWh, is increased by an efficiency loss factor, or heat rate penalty. The second, CO2 emissions per MWh, is increased by another efficiency loss factor, which is greater than the heat rate penalty and non-linear. This second factor is derived from a paper by White and is not in addition to the heat rate penalty.

The calculator credits wind with the full electricity production contribution as measured over a year, [Read more →]