Emissions Savings Details


In my Emissions Summary I stated my core position was there has been no demonstration, with real numbers off a real grid, that wind energy actually reduces emissions.  Further there are good reasons why there may be no reductions at all.  This post goes into more details about those good reasons.


First, some background on the operation of the electric grid. For all practical purposes the grid itself has no capability to store electricity in any useful amount. The generation must match, on almost a second-by-second basis, the demand at all times. This matching of supply and demand is critically important to the stability of the grid – if it is done badly, the customers will experience the effects very quickly, in the form of brownouts or worse. Almost needless to say, a steady supply of electricity is one of the fundamentals of an industrialized society; our standard of living takes a very quick drop if the supply isn’t available when we need it.

In the olden days the utility companies were responsible for doing this matching. With deregulation, in most jurisdictions, there now exists a quasi-government organization whose job it is to arrange for and then control the different suppliers. Names like ISO (Independent System Operator) or TSO (Transmission System Operator) are used to describe this organization. In Ontario it is named the IESO, or Independent Electrical System Operator. The IESO has a long historical record that allows them to predict quite accurately how much electricity will be demanded at any point in time. With conventional power generation they are able to control the supply quite accurately. By controlling the supply and knowing the demand they could highly optimize the generation to lower costs and emissions.

Unknowns in the Short-Term

The advent of wind power introduces a new uncertainty into that operation. Not only could the instantaneous demand change in (hopefully small, on the order of a mw or two per minute) unexpected ways, but now the generation can also change in not-so-small unexpected ways. The wind operators release no information they don’t have to, but one Warren Katzenstein, a graduate student at Carnegie Mellon University, managed to get some minute-to-minute data for a presentation and a study. By the way, this is the only minute-to-minute chart I’ve ever found. I added the vertical 5-minute markers and you can see that the output can go up or down by multiple tens of mw’s in a single minute! I expected some variation, but this is extraordinary. For a typical 200-mw Ontario project the changes would be twice what this chart shows.

The remaining generators (coal, gas, hydro and nuclear) must be tweaked not only to adapt to changes in demand, but now also to adapt to changes in wind supply. If our goal is to reduce fossil emissions you would use wind to replace coal and gas plants, and thus you would tweak them first. Tweaking nuclear isn’t practical in any event; it runs pretty much at full power constantly, providing “base load”. Depending on the facility, tweaking hydro is possible. But using CO2-free generation plants to back each other up doesn’t save on CO2; only replacing fossil fuel plants does. Coal plants don’t like to be tweaked, and are too slow to respond to the changes that wind can introduce. By default gas plants become the preferred choice. With the current penetration of less than 1% in Ontario this doesn’t represent much of a problem, but as the penetration increases it becomes a larger problem. Ontario is currently in the process of building at least 3 new gas plants. Alberta, with a 4% penetration, is in the process of building a fossil-fired backup plant, and even Bonneville, with all of its hydro, is also.

An important consideration of how to provide this backup is determining how quickly the controllable supply can be tweaked to match the demand minus the wind supply. The best circumstance would be to have a unit that consumed no fossil fuel until it was needed and then switch it into full production instantly. This circumstance is, by the way, what the advertised CO2 savings numbers all assume. Unfortunately no unit, even gas, is that quick. All ISO’s maintain a “spinning reserve” of generators that are kept in phase with the grid but generating at less than their capacity. Some of that reserve is used to back up potential failures; and now some addition reserve is needed to back up wind. Also unfortunately, when a fossil generator is run at something below its capacity its emissions go up, potentially enough to cancel out the savings from burning less fuel – and as mentioned above there is a surprisingly small reduction in fuel burned to begin with.

It Gets Worse

There are two types of gas turbines used in power generation – Simple Cycle Gas Turbine(SCGT, or sometimes OCGT, Open Cycle Gas Turbine) and Combined Cycle Gas Turbine(CCGT). CCGT is the most efficient, emitting around 0.35T/mw-hr, as opposed to SCGT, which emits around 0.5T/mw-hr. Unfortunately, CCGT is limited to how quickly it can ramp up or down, with a typical ramp rate limit of 5mw/min, compared with SCGT, which can handle changes of multiple tens of mw’s/min. The demand on Ontario’s grid seldom, if ever, changes unexpectedly by more than a few mw’s/min, so CCGT is entirely adequate for this application. All of Ontario’s major gas turbine plants (as of mid 2009) are CCGT’s. Unfortunately, the changes in wind output are far beyond the capability of CCGT to handle.

Let us say you wanted to produce 200mw of electricity. Two choices come to mind: (1)install a 200mw CCGT and be done with it, or (2)install a 200mw wind farm and 200mw of SCGT. But that gets very expensive to operate – remember that a 200mw wind project may average only 50mw, leaving an average of 150mw to be produced by SCGT. It also creates more emissions than (1). To save some money and emissions, you’d probably have a mix of CCGT and SCGT, and then have to use a higher proportion of SCGT in the windier months, when the variability of wind is at its greatest. Option 1 looks better and better, doesn’t it? Kent Hawkins has analyzed this at length (especially “My Articles”, item “D”). Kent has also published on WCO’s web site. Using any reasonable set of assumptions, it looks like option 2 ends up producing more emissions than option 1. Lang, 0.2mb and Hewson, 0.1mb have also come to similar conclusions.

And Worse

If all this weren’t bad enough, there’s more bad news – truly bizarre. What happens when there’s too much wind generation? Generally you sell it off, sometimes paying people to take it as Ontario sometimes does. You can guess who ends up paying for this – either the ratepayers or the taxpayers.

And Worser

One way to make fossil fuel plants more efficient is to make them into CHP’s – that’s short for Combined Heat and Power. Going to CHP sounds like a good idea, but as always the devil’s in the details. With CHP’s you now have two uses (heat and power) and two potential user groups for the output. What happens if you don’t need both the heat and the power? You can’t just turn off the generator when, for example, the need for power drops. Other users might still be needing the heat. So you’ve potentially got to keep the CHP going when you’ve already got excess power. Consider what happens when there’s even the possibility of too much wind generation, where you end up taking an emission-free nuclear plant offline and replace it with a “25/75” mix of wind and gas, just to keep the CHP’s going. Talk about shooting yourself in the foot.

Aren’t there some solutions?

If you’ve been doing much research prior to reading this, you probably have heard the argument, here advanced by AWEA that wind power variations are just like other power plant failures, and can be handled by the same techniques. Further, using statistical techniques, the argument goes on to claim that a penetration of 20% can be handled with current backup facilities with no significant extra emissions, due in part to geographical dispersion. This may explain why proponents are also big on the “super grid”. This logic sounds spookily similar to that used by AIG as they piled credit swaps on top of each other, including the use of statistics to make the risk appear lower than it really was.

A variant of this is the idea of “net demand”, where wind power is treated as a reduction in demand, as opposed to additional generation. Traditional dispatchable generators then “merely” supply the delta, albeit with “just” increased unexpected changes in demand. GE, a major supplier of all types of generation, pushes this variant, perhaps in part because wind power (and solar power too) generates power so randomly their computer generation modeling tool (MARS) isn’t able to model it. Ontario’s IESO apparently has adopted net demand, 0.5mb, section 3.1.3, and I also find it interesting that Ontario’s plan, 0.2mb, tables on page 5 calls for new SCGT generation, in the same amount as the planned future wind generation capacity. Even a system with lots of hydro, like Bonneville, has problems with wind variability.

And while I’m at it, take a closer look at the AWEA link above. On the first page there are 7 bullets with 4 external references all extolling the emissions and fuel savings of wind. The assertions look pretty impressive, unless you take the time to read through to the references. There’s no “there” there. NONE of the bullets NOR ANY of the references provide real-life numbers, just more assertions and computer models.

Here’s some typical questions

  • Couldn’t some conventional generators be shut down completely? Of course they can. But if too many of them are shut down and the winds drops quickly enough the ISO is then forced to start cutting power to users. In 2008 the Texas ISO got caught, with the resulting brownouts and shutdowns making the news. And I think it’s safe to say that any sort of interruption is far more costly, in terms of both dollars and emissions, than providing proper backup. I see no way around this – the ISO has to keep extra fossil fuel generation online and spinning, and this produces CO2.
  • Couldn’t you use hydro as the backup? Of course, within limits. But that assumes you always have it available. Generally hydro is already being used whenever it is available, as the water is “free” – both in dollars and in emissions. What would you in turn replace the hydro with? You’d end up just transferring the generation from hydro to fossil, back where you started.
  • Doesn’t the wind always blow somewhere? Not as much as you’d think. John Harrison did a study that quantifies the relationship in output. In summary, within 400km the output between wind farms is highly correlated. Tom Adams has done similar research, with similar conclusions.  My Bonneville posting has more data to support their conclusions.
  • Couldn’t you control the fossil turbines to minimize the emissions. Of course you could, and I would expect the ISO would do so, within all the other parameters they must follow. But whenever it’s running, it’s still producing CO2. The only question is “how much?” and that can only be answered with a study, a study that seems to not exist.
  • Couldn’t you build a super grid and move wind energy (and solar energy as well) around from where it was generated to where it was needed? Of course you could, but at what financial and environmental cost? Remember we started out with just wind farms, then we got into having backup, and now all of a sudden we’re into reworking our entire grid. I bet before we’re done we’ll be talking about some very expensive energy storage projects also.

In the meantime, the Chinese et al will be installing coal plants that produce a consistent kw-hr for 3 cents. We already have high wages, and when we add high energy costs, you can guess where the energy-intensive industries will go. Exporting our manufacturing base is certainly one way to cut our emissions; sadly the net effect on the planet is an increase.

Given the higher cost of energy and the job losses (see my Economics section) our standard of living will inevitably start downward.  As it does I suspect all political support for any emissions savings will evaporate, with uncertain political results.

Unknowns in the Longer-Term

So far we’ve been talking about the requirement to balance the grid on a minute-to-minute basis, and how extra fossil emissions are necessarily generated in order to do so. There are other patterns of demand that operate on different time scales other than minute-to-minute. There are also daily, weekly, seasonal and long term patterns. I hope that by understanding the shorter-term situation the reader can then apply that same reasoning to the longer terms as well. One potential solution for the daily problem would be to use some type of storage that would effectively isolate the turbines from the grid, and allow their output to be used in a controlled manner. Batteries, compressed air, heated salts, electrolysis are typical candidates. Sadly, none of these technologies are even close to being deployable, and may never be. If they were I would be much more positive about the contributions wind turbines could make to our grid. For terms longer than daily wind turbines do not provide much relief either. Their output is “non-dispatchable” – it cannot be commanded to contribute. Thus sufficient fossil plants must exist to meet the weekly and seasonal peaks.

For intermediate-term storage (i.e. daily) there does exist one scheme that might make wind more effective. That would be pumping hydro uphill in times of good wind and thus giving hydro power better capacity to handle times when the wind isn’t blowing very hard. Hydro storage is reasonably efficient – I’ve seen numbers in the 75% to 85% range. However, it does require some fairly specific geographical conditions that are not common in Ontario. Lake Erie would be the most obvious storage pool, and is already being used in this fashion. I don’t know if Niagara has the needed capacity (especially since the upstate NY wind farms are no doubt thinking the same thing). I also wonder what the total losses would be by the time you transmitted the wind energy to Niagara, pumped the water uphill, ran the water downhill and then sent the power back to the user. There’s also the difficulty of balancing competing interests, not just between countries, but among shippers, boaters, shore birds, cottage owners and all the other users of Lake Erie. In any event the costs and losses of this operation are not included in any current wind promotional figures.

As far as I can tell, no fossil plant anywhere in the world has been shut down due to the advent of wind. Perhaps a few have been shut down due to the advent of the necessary gas plants, but even that isn’t clear.


Proponents point to Denmark as an example of what wind power can accomplish, but when you look at the actual numbers, a different picture emerges.

  • Notice there’s no relationship between wind production and emissions.
  • Overall, there’s been little savings.
  • A closer look reveals their shift to CHP plants and exchanges with neighbors explains almost all of what little savings there have been.


One action that an ISO could take to improve the operation of the grid would be to remove as much of the uncertainty as possible, thus allowing for the low-cost and/or low-emission generators to be used at their best. Towards this end ISO’s are now requiring suppliers to forecast how much energy they will produce, or are creating their own forecasts. Alas, this letter from Environment Canada, in response to a query, shows there might be problems. Even the WSJ has opined on this topic in a well-written column.  The Economist also has a well-written column with more details.

Typically this forecast would be used in the ISO’s “day ahead” planning, when they figure who needs to be available when. For wind suppliers, this means a highly tailored weather forecast. And where there is money to be made, someone will appear to make it. The results to a google of “wind energy forecasting” will provide the reader some interesting hits, certainly including better explanations of this whole topic than I have provided. If the suppliers do not meet their forecast some ISO’s are fining them, and I assume the fines in some way compensate the ISO for the excess costs or emissions caused by a bad forecast. There are also people employed measuring and statistically analyzing how consistently each supplier meets their commitments so they know whose forecast they can trust. All of this, just to optimize a resource that nobody knows the value of in the first place. Incidentally, the ability to accurately forecast also affects the Capacity Credit, as discussed on my energy security pages.


Even if I’m correct in my assessments of these issues, does it really have any detrimental affect on our plans to cut emissions? There are likely two poor results. The first one is that it overvalues the contribution of wind turbines to solving the CO2 problem, thus potentially directing scarce resources away from more effective solutions. If Ontario thinks they are getting 1.0x reduction for y dollars but in fact they are only getting 0.5x, this might well lead to a situation where another solution could yield .75x but isn’t pursued due to its (incorrectly) lower perceived value. The second reason is that overestimating the CO2 reduction of wind leads countries to likely emit more CO2 than, for example, Kyoto allows them to. In addition to breaking treaty obligations, this error could confuse the measuring of, modeling of and responses to the increase in CO2.


Note that I am not saying I know for sure that there is no CO2 benefit to wind. My primary point is that we don’t know, and there are very good reasons why it is likely much less than advertised. It is bothersome that apparently no government seems eager to tell us this. I wouldn’t expect the industry to do so, unless it was good news. In addition to all the above problems, which are significant, there’s the added unknown of how much energy turbines receive off the grid in normal operation. That number, which could be a significant percentage of their output, seems to be a closely guarded secret.

If our politicians were actually interested in reducing CO2 emissions (instead of just wanting to appear “green”), they would be far more effective by working on reducing consumption. To install 2000 mw of wind power (producing an average of about 500mw, or about 3% of Ontario’s electrical consumption) will cost about $4B, not counting the grid itself nor any backup or storage facilities. For that kind of money we could, as an example, replace most of the older water heaters in the entire Province of Ontario with tankless ones, saving more than the production from all those turbines, and without screwing up the countryside.

If the technological arguments weren’t already complicated enough with all these unknowns, this topic is even further clouded over by the carbon trading market, as detailed in this article and this letter and this opinion piece. I hate to be so cynical, but actual carbon reduction seems to be among the least important goals of the “green energy” movement, with the desire for money and political power far more important.

6 thoughts on “Emissions Savings Details”

  1. You assume that a 200 MW wind plant needs to be backed up by 200 MW of gas plant and that the 200 MW gas plant is running below capacity whenever wind isn’t blowing. In fact, the system operator aggregates ALL the intermittency of load AND generation and places the required amount of spinning and non-spinning reserve into the system to maintain stability. For wind penetration up to 20%, the efficiency penalty may reach 7%. In other words, wind displaces 93% of CO2.

    That’s if gas is used as backup. In Ontario, we now have a tie line to Hydro Quebec that exceeds the entire installed capacity of wind. We don’t have to burn gas or coal to backup wind – we now have access to hydro.

    Here’s a more detailed explanation as written in the IEEE Power and Energy Magazine Nov/Dec 2009.

    Doesn’t Wind Power Need Backup
    Generation? Isn’t More Fossil Fuel
    Burned with Wind Than Without,
    Due to Backup Requirements?

    In a power system, it is necessary to maintain a continuous
    balance between production and consumption. System operators
    deploy controllable generation to follow the change in
    total demand, not the variation from a single generator or
    customer load. When wind is added to the system, the variability
    in the net load becomes the operating target for the
    system operator. It is not necessary and, indeed, it would
    be quite costly for grid operators to follow the variation in
    generation from a single generating plant or customer load.
    “Backup” generating plants dedicated to wind plants—or to
    any other generation plant or load for that matter—are not
    required, and would actually be a poor and unnecessarily
    costly use of power-generation resources.
    Regarding whether the addition of wind generation
    results in more combustion of fossil fuels, a wind-generated
    kilowatthour displaces a kilowatthour that would have been
    generated by another source—usually one that burns a fossil
    fuel. The wind-generated kilowatthour therefore avoids
    the fuel consumption and emissions associated with that
    fossil-fuel kilowatthour. The incremental reserves (spinning
    or nonspinning) required by wind’s variability and uncertainty,
    however, themselves consume fuel and release emissions,
    so the net savings are somewhat reduced. But what
    quantity of reserves is required? Numerous studies conducted
    to date—many of which have been summarized in previous
    wind-specifi c special issues of IEEE Power & Energy
    Magazine—have found that the reserves required by wind
    are only a small fraction of the aggregate wind generation
    and vary with the level of wind output. Generally, some of
    these reserves are spinning and some are nonspinning. The
    regulating and load-following plants could be forced to operate
    at a reduced level of effi ciency, resulting in increased fuel
    consumption and increased emissions per unit of output.
    A conservative example serves to illustrate the fuelconsumption
    and emissions impacts stemming from wind’s
    regulation requirements. Compare three situations: 1) a
    block of energy is provided by fossil-fueled plants; 2) the
    same block of energy is provided by wind plants that require
    no incremental reserves; and 3) the same block of energy is
    provided by wind plants that do have incremental reserve
    requirements. It is assumed that the average fl eet fossil-fuel
    effi ciency is unchanged between situations one and two. This
    might not be precisely correct, but a sophisticated operational
    simulation is required to address this issue quantitatively. In
    fact, this has been done in several studies, which bear out the
    general conclusions reached in this simple example.
    In situation one, an amount of fuel is burned to produce
    the block of energy. In situation two, all of that fuel is saved
    and all of the associated emissions are avoided. In situation
    three, it is assumed that 3% of the fossil generation is needed
    to provide reserves, all of these reserves are spinning, and
    that this generation incurs a 25% effi ciency penalty. The
    corresponding fuel consumption necessary to provide the
    needed reserves is then 4% of the fuel required to generate
    the entire block of energy. Hence, the actual fuel and emissions
    savings percentage in situation three relative to situation
    one is 96% rather than 100%. The great majority of
    initially estimated fuel savings does in fact occur, however,
    and the notion that wind’s variations would actually increase
    system fuel consumption does not withstand scrutiny.
    A study conducted by the United Kingdom Energy
    Research Center (UKERC) supports this example. UKERC
    reviewed four studies that directly addressed whether there
    are greater CO2 emissions from adding wind generation due
    to increasing operating reserves and operating fossil-fuel
    plants at a reduced effi ciency level. The UKERC determined
    that the “effi ciency penalty” was negligible to 7% for wind
    penetrations of up to 20%.

    Wind Power Myths Debunked, Milligan, et al IEEE power & energy magazine nov/dec 2009

  2. I’ve read over the study that Malcolm references, Milligan, in detail and it is not persuasive. All the numbers about savings etc that he quotes are calculated and/or modeled. Not a one of them is measured.

    Don’t forget that Milligan works for NREL, which has the mission of supporting “renewable” energy – and wishful thinking is sometimes the result of that mission. That doesn’t automatically invalidate his writings, but a close reading of this particular article, for example as detailed in this Kent Hawkins article


    tells me that, at best, the matter is unresolved and we really need to actually measure it. Since only the government, like NREL, has the information and the resources to do a good job of measuring, one has to wonder why they haven’t done so.

    I’d love to see a study, like Bentek’s, done on gas plants. Or on a grid as a whole. Until that type of study is done and published all Malcolm and Milligan can do is speculate, and I’m of the opinion that one doesn’t incur the numerous costs of wind energy on speculation.

  3. In any other form of investment, a prospectus for Wind power generation to reduce Co2 would be considered a SCAM and the perpetrators would be sitting behind bars. Models should never be used to justify the benefits.

    Even after the billions of dollars have been spent, the real world evidence shows a Wind power (factory, not farm) at best can only offset approx 8% of it’s claimed power output in Co2.

    The situation get progressively worse the greater the % that Wind makes up of total power system supply, dropping to 4% in efficient markets. Less efficient markets (where Wind fluctuates to greater degrees) is actually Co2 positive, due to the need for Coal backups.

    Those are the best case scenarios. Once the costs of Co2 in production of the Wind Turbines and the loss of efficiency from long transmission lines are considered, many Wind factories will be Co2 positive for their functioning life.

    Leaving on the enormous environmental costs to wildlife and humans. See link: http://www.youtube.com/watch?v=svicELHAWyw

  4. The wind blows, the blades rotate, electricity is generated and no smoke or CO2. I live 15 feet above high tide. FIGURE IT OUT! Your website shows lack of imagination. Should we give up on tidal and solar too? Nature is intermittent. Pressurized air or pumping water will have to be in the future as well as the overcapacity to make it work. Burning coal or gas is a short term solution for China or anyone. We will stop producing CO2 or we will have a severe population crash. (Problem solved??).

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