Thursday
Dec022010
by 
Bishop Hill
Bishop Hill Wind capacity again
Dec 2, 2010 Energy 
Another interesting assertion by Prof Anderson on the earlier thread was what he had to say about capacity factors for wind turbines:
...the capacity factor for turbines - which ranges from low 20 to 50 depending on size and location (well sited on land probably 25-35%, with well sited offshore and bigger (3-5MW) 35 to 50%) - I recall a few years back some 3MW turbines near the Shetlands reached 52% over the year - though the Shetland is a particularly good site.
When we discussed this the other day, we were looking at figures that were much lower than this - more like 10%. Can anyone explain the discrepancy?
Reader Comments (76)
HI Andrew.
There'll be lots of people weighing in on this, but if anyone comes up with a more accurate and succinct statement than the following one, I'll be surprised.
The explanation of the discrepancy, is that you're looking for what's wrong with turbines, whereas Prof Anderson is looking for what's right with them.
[BH adds. This is not a constructive comment. If you are interested in understanding the differences in the two figures please feel free to take part in this thread. Otherwise please do not get involved.]
Bish, Having given evidence at wind farm public inquiries, I can state that the wind industry and its followers consistently give misleadingly high capacity factors. True values can be obtained from ROC returns and by government statistics (DUKES - Digest of UK Energy Statistics)
Good and up-to-date data are given by the Renewable Energy Foundation at:
http://www.ref.org.uk/uk-renewable-energy-data
The explanation of the discrepancy, is that you're looking for what really happened, whereas Prof Anderson is looking for results from mathematical models.
Trying to find what's right with wind trubines is like trying to find a needle in a haystack. You won't find anything of any use. Intermittency, unpredictability, safety, cost, need for back-up, environmental destruction, noise; the list of problems is virtually endless.
If anybody wants to see the environmental destruction of a welsh wind farm, I suggest looking at the pictures here:
http://www.users.globalnet.co.uk/~hills/cc/gallery/index.htm#photos
Zed, just do some reading.
Research load factors here:http://www.ref.org.uk/images/PDFs/REDs10/Wind%202010%20v1.pdf
Research the problems with integrating an intermittent and highly variable generation source to the grid.
Understand emissions increases through forced cycling of conventional backup capacity.
Get the point: wind is not despatchable. Wind is not capable of base load generation. Wind is - at best - a problematic add-on to stable conventional capacity.
These are facts, not anti-science rantings or whatever else you will probably claim.
At this point, the anti-science (or at the very least, anti-engineering) rhetoric is coming from you.
In Scotland even Scottish Renewabloes seem to accept the average figure is 27%. My guess would be that when the author says "from low 20 to 50 depending" they actually mean "from a median of 20% to the absolute maximum of 50% ever achieved, below average sites being ignored ".
I suggest readers look at
http://www.masterresource.org/
There is a very good post on German windfarmery. weep as you read. In answer to ZDB, what would you find right with a car that worked 52% of the time? Or an employee that thought 2.5 days per week for 5 days pay was "right".
Cheers
Paul
It depends what capacity factor you're talking about. There is the nominal CF that is used when planning a turbine, you can have a factor for individual turbines and farms, and then there is a 'capacity factor' of various sorts derived from the actual production.
If you're talking about specific turbines/farms as Prof A seems to be doing, then in nominally advantageous conditions you may well see higher factors, but these are usually theoretical.
The best measure of the effectiveness of wind is to look at what it actually generates as an average across the whole installed base. At the time of writing, the latest data (for 10.35GMT) shows an installed capacity of 2430MW of Wind power generating 523MW of power, or 21% of capacity (assuming the installed figure is not already factored). Over the last 24hrs that fleet of turbines has produced 13,874 MWh or 23% of theoretical amount rated. This is 1% of what the country needs.
That ties in with the usual 20-25% quoted as wind availability. The 10% mentioned may be due to people factoring down already factored ratings. The 50% suggested by the Prof would seem wildly optimistic, though may be seen in a particular place at a particular time. He would of course have to produce his reference for the quoted figures. Mine is here:
http://www.bmreports.com/bsp/bsp.php
Your Grace,
The reason for the discrepancy is obvious.
You are simply quoting the actual figures, whereas Professor Anderson has filtered them through the same part of his brain that allows him to hold simultaneously the ideas that nuclear power is not necessary and that rationing is essential.
@ Cumbrian Lad
Spot on. Thanks for linking to bmreports - I should have done in my response to ZDB above.
Zed - read and learn.
The super high figure is for the Burradale wind farm. It would appear to be an exceptionally well chosen site in terms of matching wind resources to the size of the turbines.
Perhaps the enormous ones that keep popping up are too big to achieve high capacity factors. They need slowing down in high winds whereas smaller turbines perhaps don't.(smaller forces at work) The smaller turbines may also require less maintenance. If any of those apply why are we seeing multi-MW turbines being constructed if they aren't as efficient as more modest installations? I would venture that it is in part a desire to race up the league table of installed capacity for national prestige purposes. It is also that the costs are being met by regulator and Government approved energy price rises rather than by energy firms saving money on their fossil fuel bills.
A capacity factor of 50% is not impossible for a particular year and a particular site. 1998 was particularly windy for instance. But generally as you add more and more windfarms, the overall capacity factor will drop as all the best sites are taken first. In the mid 2000s the capacity factor in UK/Ireland was in the range 30-35%, but this year it's down near 20% overall. Another factor is that a windfarm might have a nameplate rating greater than its contracted export capacity - e.g. 100MW might be installed, but they are only allowed export 90MW due to transmission constraints etc. This can have the effect of bumping up the capacity factor because it will be calculated based on the 90MW rather than 100MW.
The "capacity factor" is a function of output, capacity and time.
Comparison of any two estimates of of the "capacity factor" will need to consider the underlying basis of the three inpputs required and their consistency.
Chose a windy period of time and the capacity factor will be higher.
Calculate the capacity factor without properly calculating the avaialble capacity (i.e. the denominator in your calculation artificially lower.
Even silly things like averaging capacity factors across sites rather than aggregating across the entire grid can bias up the measured capacity factors (smaller sites are likely to have higher capacity factors).
660kW turbines are not going to go far in providing energy for the masses. Efficient yes, but productive? Cost effective?
It is becoming clear that it is very difficult to find "explainable" numbers. Don't really know what wind sites are included in the total energy produced (per National Grid), and don't really know what is the total capacity (to enable the computation of load factor. Finding inconsistencies most everywhere I look with nothing definitive. It could be that I'm just missing the obvious. The fact that there are so many inconsistencies is causing me to continue the journey on this. (Took a couple of weeks off to travel abroad and returned to UK by air just in the nick of time before the snow set in).
It must be noted that the "average" is only that. The distribution is skewed toward the low end, i.e. significant time below average which implies that to maintain security of supply power generation has to be augmented by other means or the power supplier has to practice "demand management". And it could be the 10% figure is low due to power off the national grid yet included in the denominator for load factor. Again, I'm seeking definitive lists of what's in and out of these numbers published by various parties.
Of course, what is really needed is for the Professor to cite his source data.
The Renewable Energy Database, already linked by Philip Bratby above, publishes actually generation data for UK windfarms. This supports what Professor Anderson has said - well sited wind farms on land operate to a capacity factor of about 25 - 35% (although a lot are in a lower bracket of 20 - 25%). Sites operating at less than 20% will have typically suffered intermittent generation either due to technical problems or environmental constraints (e.g. limits on operating hours due to noise), or suffer from sub-optimal siting (e.g. the windfarm at Nissan's plant at Washington operates at <20% CF as the site is not well-sited for wind, but Nissan used reconditioned turbines which would rebalance the financials somewhat). Sites operating at 10% capacity or less are rare - these would tend to be "vanity" turbines (installed at poor locations as a symobolic statement of intent) or else non-operational for long periods of time (e.g. some local authority turbines, installed with grant money, have been out of commission for long periods of time because the authority did not have a revenue budget to fund maintenance costs).
"actual" not "actually"!
"Sites operating at less than 20% will have typically suffered intermittent generation either due to technical problems or environmental constraints (e.g. limits on operating hours due to noise),"
Neither of these are reasons to exclude sites from the calculation of your ACTUAL - or actually :-) - capacity factor. Quoting "20-35%" for good sites is fine, as long as you are clear about the extremely heavy caveat surrounding that number.
But by the magic of MSM reporting, what we will actually get is "Prof Anderson says wind farm capacity factor is [...] 35%, [...] and in many instances above 50%", followed by a figure of the total installed capacity.
That's the issue here.
Angus,
And the important statistic is what is the system wide average capacity factor. Noting that there will be some theoretical universal factor that would be achieved over long periods of time over the entire country on average.
With best sites deployed first the system wide capacity factor would be expected to fall to that theoretical universal capacity factor as the system grows.
Your Grace
How goes the wind in your Residence in Kinross? As pathetic as further west along the A91? I've been watching the weather station from Stirling, and there's been barley a breath of wind in the last few days since the cold spell arrived.
There a distressingly large number of wind farms around Stirling, Callendar and the Trossachs. They are key to the Scottish economy becoming a 'world-leader in renewables', according to Mr Salmond.
And yet during this cold spell, when power is needed more than ever just to keep old folks like my Mum from freezing to death, they produce nothing at all. And this is not an isolated incident. Similar conditions occurred during the very cold spell last February.
Could one of the wind power advocates please enlighten me as to what wondrous capability of these subsidychewers I am missing?
Because to me they are about as much use as a spare p...k at a wedding...but not so decorative!
[BH adds - a breath of wind, no more]
The Bonneville Power Administration has 3011 mw of capacity in the US northwest. They provide real-time graphs(5-min) of power generation and usage. In the last six days there was only one day where they consistently provided 25% to 50% of rated wind capacity. Three days were consistently below 10% capacity.
Here is a link to their numerous graphic and data files if anyone is interested.
http://transmission.bpa.gov/business/operations/Wind/default.aspx
Every time I drive past the group of 8 near Scunthorpe, one or more is stopped. Why is this ?
Usual scenarioo is 7 rotating and one stopped. Not always the same dead turbine.
High variations in average output from wind-power turbines reflects the fact that their output is a function of the cube of wind speed. Small changes in wind speed thus lead to big changes in output.
I recall a brouhaha a few years back over two proximate sites in N Wales whose productivity differed widely with local objectors claiming fraudulent readings in the more productive site. However, quick calculation showed that the discrepancy could be accounted for by a mere one-metre-per-second difference in average wind speed.
Typically, wind power delivers ten per cent or less of its theoretical capacity for 80 per cent of the time. It is an irony that eludes the vociferous wind-power lobby that turbines are at their most effective when wind speeds are low because, though the displacement of fossil-fueled generation is modest, it is also relatively stable and thus likely to be more efficient.
The wind-power industry and its “green” apologists assume fatuously that the displacement efficiency of wind power is 100 per cent. It isn’t and only an ignorant fool assumes it is. At times of high wind speed, it is possible to demonstrate that the displacement may well actually be negative.
Citing load factors as Anderson does here is common practice but misleading. Note that LFs are a measure of productivity, not efficiency. Efficiency measures how much of the energy available in the wind is converted into electricity. On that parameter, wind power is efficient, typically 95 per cent or more (the rest being lost as heat in the turbine and of course as noise).
That wind power is typically less productive than its proponents previously claimed is for them to sort out with their bean counters.
A much more serious issue for any genuine believer in AGW theory is the lack of any measure of the extent (if any) to which wind power cuts CO2 emissions.
This is critical because, for all the crap that its supporters peddle, it is an adjunct to and not a replacement for fossil-fueled generation. However, cuts in emissions as a function of wind-powered generation are not measured and there are no plans to do so at the provincial (in my case, Scotland), the national (Westminster) or the EU levels.
I and others know this because we have have ensured that the issue has been raised in Holyrood, in the HoC and in the EU parliament. In each case, we were given the same answer.
Now, I’d have though that anyone who genuinely believed that we are hovering on the brink of an environmental catastrophe would take time off from bullying local communities and look into that. The eco-lobby groups have the resources to fund that research.
For serious answers on the limitations of the technology, see “The wind farm scam” by John Etherington. It does for wind turbines what The Hockey Stick Illusion did for dodgy graphics.
@ Philip Bratby and Angus Pangus,
Thanks for the pointer to http://www.ref.org.uk/uk-renewable-energy-data where they have http://www.ref.org.uk/images/PDFs/REDs10/Wind%202010%20v1.pdf and http://www.ref.org.uk/roc-generators/. The former is >900 pages of terrific data in text format (looks like produced with Microsoft Access report), and the latter is a list of the 5,539 Renewables Obligation Generators.
I've contacted the Renewable Energy Foundation to see if they have this data available in a database having a time series of the generated power by each generator, along with a related database of each each generator. I am hoping to do some analysis using my own tools to see the probability distributions of the raw data and this information isn't yet in a form which facilitates that.
Ideally what I want as a first graph is the probability distribution of achieved load factors for all wind generation in the entire country using as many years of data as possible. We have enough of tese devices them now in operation, I would think, to get a sense of the overall performance of all machines; not just those which are sited ideally, or those that are operating correctly. I want to have everything, including those not ideally sited, those not operating due to excess or insufficient wind, and those not operating due to periodic mechanical failure.
This overall picture, I think, will give us a good indication of what the future will be as we depend more and more on wind (which is the country's intentions).
Doesn't this highlight the general problem with the climate change debate - the chasm between the epoused catastrophism and a critical reality.
People like Prof Anderson can indulge in pure flights of fantasy, and get handsomely paid for it, because professional criticism and scepticism has been eliminated from the debate.
Prof Anderson can quote fantasy figures on all aspects climate science and climate policy with impunity in the knowledge that his position his safe.
That is the scale of problem with CAGW zealotry. It really doesn't matter if the elderly die from the cold when £bilions are required to support and safeguard a badly flawed ideology.
Gecko,
load factor/capacity factor might be expected to fall as less good sites come forward for development. But that assumes that all else remains equal, which is not the case. Technology advances, which can mean, for example, that turbines can extract energy across a wider spectrum of wind speeds, increasing the load factor at later, sub-optimal sites, or they are simply more "robust" (snigger!) meaning that they are out of commission for shorter periods of time, which also increases the load factor. Also, of course, the old, "prime" sites may get re-powered with newer turbines, which can also increase effective capacity.
Ultimately, of course, there is a limit to the number of sites that are technologically, environmentally and financially developable. In particular, the fact that wind turbines are rarely commercially viable (even with ROC/FIT support) below a load factor of about 20% pretty much guarantees that you will not see wind turbines operating below this.very often. So I wouldn't expect the system-wide load factor to fall much if at all from where it is today.
Dave B:
Wrong. The maximum theoretical efficiency of a turbine converting wind energy into rotational energy is given by Betz Law as 16/27 = 59%. A typical efficiency achieved by a real wind turbine converting wind energy into electrical energy, taking all losses into account, is likely to be in the range 25 - 30%.
Posters should be careful about being over-critical of these windmills, as their probable owners are not noted for their sense of humour. You might end up with a set of cement boots, always tricky to handle in deep snow.
Meanwhile, O/T, at Cancun, Kyoto refuses to renew the Kyoto treaty:
http://www.independent.co.uk/environment/climate-change/japan-derails-climate-talks-by-refusing-to-renew-kyoto-treaty-2148769.html
:-)
A summary of Danish data is readily accessible The average capacity utilization over the last 10 years I calculate to be 22.3%. It ranged from from 19.1% to 26.1% and got just above 25% only twice (2007 and 2008) I assumed that give daily, weekly, monthly or seasonal variability the range is from 0 to 50% - it seems to me that capacity utilization depends on the period over which you are averaging. At a minumum it should be calculated the same way and over the same period that the utilization rate is calculated for other methods of electricity power generation. IMHO, the Shetland data quoted needs checking - but it is hardly representative of anything. I daresay the rating in Patagonia would be higher than the Trossachs.
I meant here
@ Rick Bradford
Yes, predictably enough, the Italian Mob got into green energy quite early on. It's always been all over the construction sector, so it was a logical move. All those lovely subsidies just waiting to be hoovered up proved irresistible.
Here in the UK, the scam is mainly grounded in the City. Although the basics are much the same: invest in wind and harvest the subsidies until the government eventually wakes up to the scale of the disaster and turns off the money tap (see Germany, Spain, Italy, Denmark etc).
*Important health and safety advisory: to avoid danger of asphyxiation do not hold your breath*
Swedish data are also available (http://www.vindstat.nu/). I have analyzed these (about 1000 windmills) and the average capacity factor for land-based units is slightly over 20 % and for sea-based about 30 %. The highest single capacity factor is 44 %, so the probability of reaching 50 % is apparently well below one in a thousand. Very few sites are below 15%.
Interestingly there seems to be no clear trend that figures are better for larger or younger units. However inter-year variations are large, so figures are very uncertain for windfarms that haven't been in service for several years.
@ Bernie,
Thanks for the pointer to the Danish data on Wikipedia. Taking this data at face value I show it graphically as a distribution, time series, and the raw data. I used the last 20 years of data which over that period the mean load factor is about 21% with slightly better performance in recent years. See http://rmschneider.wordpress.com/2010/12/02/danish-wind-generation-load-factors-1990-2009/ if this is of interest.
If you look up the renewable energy foundation you will find every windfarm in the UK and its output listed. I can't imagine the average, if you bother to calculate it, will be very different from Sweden, but it does appear from casual inspection that in England there are lots - say 20% or more that are well below 10%.
The other big problem apart from availability is how to provide the power for the 70% to 80% of the time when they are not operating. Back up can be fairly easy when as in Scotland you can put them up beside a hydro station which can crank up or down quickly to keep the power output steady. But for most of the time in England the back up will be gas on take or pay contracts.
This means that while the wind farm is producing it not only attracts a large feed in charge subsidy from the consumer for any power it supplies, but the consumer also at the same time has to pay about 70% to 80% of the cost for the gas power he is not using in order to make sure it will be available when the wind drops.
Overall this means that the consumer pays far more when the wind farm is supplying than when it is idle and he would be well advised to come along at night and cut the cables ( or e.g. to encourage some terrorists to come along and blow them up).
I never normally have much time for nimbys but where wind mills are involved it is absolutely in our interest to support them and otherwise do our best to prevent these things from ever being built.
The big question is would anyone invest in all this claptrap trash if there were no subsidy? If not, then it is nothing more than a scam. It is an artificially driven financial farce.
Cumbrian Lad rightfully points out: 660kW turbines are not going to go far in providing energy for the masses. Efficient yes, but productive? Cost effective?
And when you look at where they are -- in the Burradale Wind Farm Shetland Islands, you have to ask what go are they going to do for the average punter in the Eastend?
If you look up the renewable energy foundation you will find every windfarm in the UK and its output listed. I can't imagine the average, if you bother to calculate it, will be very different from Sweden, but it does appear from casual inspection that in England there are lots - say 20% or more that are well below 10%.
The other big problem apart from availability is how to provide the power for the 70% to 80% of the time when they are not operating. Back up can be fairly easy when as in Scotland you can put them up beside a hydro station which can crank up or down quickly to keep the power output steady. But for most of the time in England the back up will be gas on take or pay contracts.
This means that while the wind farm is producing it not only attracts a large feed in charge subsidy from the consumer for any power it supplies, but the consumer also at the same time has to pay about 70% to 80% of the cost for the gas power he is not using in order to make sure it will be available when the wind drops.
Overall this means that the consumer pays far more when the wind farm is supplying than when it is idle and he would be well advised to come along at night and cut the cables ( or e.g. to encourage some terrorists to come along and blow them up).
I never normally have much time for nimbys but where wind mills are involved it is absolutely in our interest to support them and otherwise do our best to prevent these things from ever being built.
To all: Jeff Id posted and analysis about a month or two ago about the actual production of a typical wind farm in Texas.
http://noconsensus.wordpress.com/2010/09/15/10326/
Phillip Bratby:
Wrong. The maximum theoretical efficiency of a turbine converting wind energy into rotational energy is given by Betz Law as 16/27 = 59%. A typical efficiency achieved by a real wind turbine converting wind energy into electrical energy, taking all losses into account, is likely to be in the range 25 - 30%.
Sorry but you have misread my post. The phrase I used was "the energy available in the wind". How much is available is, as you note, given by Betz' law (which I am well aware of). How much of what is theoretically available gets converted into electricity is a measure of efficiency.
You don't say what you mean by "all losses" so I can't comment on that.
AngusPangus:
Technology advances, which can mean, for example, that turbines can extract energy across a wider spectrum of wind speeds, increasing the load factor at later, sub-optimal sites . . .
Not so. As I said, turbine efficiency is already close to the theoretical maximum. There is little if anything to be gained by lowering cut-in speeds as there is virtually no energy to be extracted at low wind speeds.
OTOH, though it is feasible to make turbines powerful enough to withstand higher wind speeds, there is less to be gained here than might appear because (a) overly-high speeds are comparatively rare, (b) gains tend to be outweighed by concomitant efficiency losses at lower speeds (due to having to make the kit stronger and thus heavier) and (c) the engineering effort would incur significant cost.
Turbines are about as good as they're going to get - which is pretty much what you'd expect from a technology essentially now over a century old - the first turbines date from the 19th century. Significant efforts to develop it were technology was made in a coal-strapped Danish economy during the two world wars and again in the wake of the 1970s oil crisis. The difference with the third push was that it was taken up and marketed by technically illiterate "environmentalists" as a means of saving the planet. It isn't.
The issues with wind power are not to do with efficiency or even LFs (primarily an economic problem) but of its integration with conventional generation - it is an essentially parasitic technology that threatens to destabilise the National Grid and unarguably reduces its overall efficiency.
The improved controls that transmission authorities have on occasion called for might well improve stability but would do so at the cost of productivity. The issue of "constrained-off" payments (where generators are paid for not producing when they could be because the grid cannot absorb the output) is of course more a political than a technical issue.
Models are not real world.
Here is what Jeff Id shows:
http://noconsensus.wordpress.com/2010/09/15/10326/
Where he shows a citation for this quote:
"According to a study of wind in the United States, ten or more widely-separated wind farms connected through the grid could be relied upon for from 33 to 47% of their average output (15–20% of nominal capacity) as reliable, baseload power, as long as minimum criteria are met for wind speed and turbine height.[25][26] When calculating the generating capacity available to meet peak demand, [ERCOT] (manages Texas grid) counts wind generation at 8.7% of nameplate capacity.[27]"
I have often seen it said that some wind turbines use electricity when not generating due to power absorbed by braking systems / slewing motors / frequency correcting apparatus and the like.
This is probably true. Does anyone have a feel for the amount of "negative generation" this might represent?
It seems to me that the only uses of wind generation that might have some merit are (a) extremely isolated and wind exposed properties where there is no likelihood of any connection to the grid and where it can reduce the amount of diesel used by a generator, or (b) where wind turbines are set up to pump water up to a raised reservoir, enabling the energy to be harvested when needed using water turbines and a pipeline (a variant of the four pumped storage schemes already in use. By using appropriate low head turbines you could image a suitable 'high level' reservoir being constructed (say) above the Humber estuary.)
But you'd be far better off going for gas and nuclear. At least they produce power predictably when you need it.
Of course, BuffHuhne has said that he thinks wind turbines are 'beautiful'. But, there again, did you see pictures of his lesbo lover, for whom he ditched his wife and children?
No accounting for taste, I'm afraid.
For those of you who don't know "ZedsDedBed" is a regular troll at the Daily Mail website, and spouts the same drivel in any similar thread. He's obviously trying to spread his influence.
I'm very grateful for the link to the Renewable Energy Foundation. I can see that our local windfarms have barely struggled above 30% on an annual basis. One of them has been operating for some 15 years or more, and consists of 10 - 225Kw turbines which are much smaller, and stand on shorter towers, than most new units. Not surprisingly these have a significantly poorer efficiency, due to the lower wind speeds closer to the surface. They are only a mile from the East coast, so still get the full force of the North Sea gales.
Sorry not to have had this with my earlier post.
Here is what is said about nuclear power:
"The remaining U.S. nuclear plants produce approximately 90% of their full-time full-load potential, but even they must shut down (on average) for 39 days every 17 months for refueling and maintenance.[32] To cope with such intermittence by nuclear (and centralized fossil-fuelled) power plants, utilities install a “reserve margin” of roughly 15% extra capacity spinning ready for instant use.[32]"
The madness of the AGW social moevement is shown so clearly in these two quotes.
Pour good money into bad power, and destroy the capacity to geenrate good power.
A question was asked "Every time I drive past the group of 8 near Scunthorpe, one or more is stopped. Why is this ?"
We recently had a public meeting concerning the erection of 8 x 2Mw wind generators in our commune. I asked the Technical chap from the wind company exactly the same question about a wind farm near here at Celles sur Belle. Finally after badgering him for about 15 minutes I managed to get out an admission that a turbine will be "out of order" (my translation of his words ) between 3 and 5% of their working life. Some will be more, some less. I was not able to obtain a figure for the amount of energy that a turbine uses when it is not generating. (He claimed that he did not understand my question. Probably my poor French.)
Martin Brumby:
Does anyone have a feel for the amount of "negative generation" this might represent?
The bulk of the power probably goes to spinning the blades as the wind approaches cut-in speed to keep the machine synchronised. I seem to recall a figure of seven per cent of total output being bandied about a while back but, as an earlier poster suggested, both the industry and the regulator are coy about it. In fairness, the power needed to turn the blades close to but just below cut-in is likely to be small but I never managed to get detail on this.
OTOH, I recall seeing a video clip of a turbine sited close to an industrial chimney stack. The turbine is spinning away fit to bust while smoke from the chimney is rising as vertical as a guardsman's back and up . . . up . . . and away. As it does when there is absolutely no wind.
I do not have sources available to quote as the papers I have seen are confidential. However it is certainly true that turbines are a waste of time financially if modelled on a commercial basis. The only way they are "viable" is with market-distorting tax breaks. That cannot be sustainable and at some point the tax-payers will hopefully spot the premium they are being asked to pay and then give their MPs earache to get it stopped. Shame the premium is not highlighted on electricity bills. Another case of more transparency required. I'd question the right of the Government to commit us all to long term deals like these for such a poor energy return.
Assume for one moment that we install 50% of our required electricity demand (at whatever CF) as wind generated with the other 50% from anything allowed other than wind. Then during a Climate Disruption Year, a high pressure centres over the UK during winter causing temperatures to drop below freezing and wind speed to near zero.
Who gets the electricity?
In this case, or 40%, 30%...... C-Factor is as relevant to grid power generation as X-Factor is. Society needs reliability, not rationing of supply.
@Martin Brumby 4:07,
There are a variety of power requirements by the wind systems themselves, as you note in your post - braking, slewing, feathering, control systems and similar, and for many units the elec generation requires power for exciter windings in the generator/alternator.
I have had great difficulty in obtaining any hard and fast numbers for this, other than the following observations -
The numbers are NOT trivial, I have had 'off the record' numbers of 20-30% of capacity quoted, which sounds very high, but not impossible.
The numbers for this are often hidden in 'operating and maintenance' costs, rather than directly declared in/subtracted from nameplate capacity of the unit.
The load for much of this is 24X7 NOT just when the unit is operating.