Earlier this week, I posted on one of the arguments used by opponents of wind farms in support of their case. One of the other arguments frequently used by them is that because wind energy is intermittent, wind farms need to have substantial back-up from conventional power stations.
A very recent extension of that is the suggestion – generally presented as fact by some letter writers and campaigners - that Centrica has told DECC that it would need to build 17 gas-powered stations “simply to provide back-up for all those times when the wind drops”. It’s described as having been the “best-kept secret” of the government’s “obsession with wind”, and of course, as “proving” the insanity of a policy which includes the use of wind energy.
Were it indeed true, I’d have to accept that it’s a pretty good argument against wind turbines – but is it really true?
Thus far, I’ve been unable to turn up the source information for any such statement by Centrica, although I have found a number of news reports on the subject, such as this one and this one. By now, the suggestion has been copied, from this type of news report, across any number of anti-wind farm blogs and websites, always reported as fact, and never, as far as I have been able to trace, providing any link to a substantive source. I've failed to establish where the story actually started.
Perhaps there is some substance to it that I’ve been unable to trace, and if anyone knows of such, I’d be delighted to have an opportunity to read what was actually said. One of the problems with the internet is that it is very easy for an inaccurate, or perhaps misinterpreted, statement to spread and gain credibility.
What are the facts here?
Well, certainly, wind energy is intermittent. It’s wrong, though, to say turbines only produce electricity 30% of the time. It’s more like 80%, but the overall load factor – the amount of electricity produced as a percentage of the maximum capacity of a turbine – averages somewhere between 16% and 40% over a year, depending on the technology (age of the turbines, basically, since the newer ones score better), location, and size of the turbine, with an overall average of around 30%.
And certainly it’s true that keeping the Grid running means that wind energy needs some form of back-up, so that, in the event of output from a wind farm ceasing or reducing, the impact on the Grid does not exceed the agreed parameters before alternative generation comes into action. But that’s true of all types of generation – and the failure of a nuclear power plant can have a much greater impact than the failure of a wind farm.
Does wind energy require more back-up than any other form of electricity generation? Opponents invariably claim that it does, appealing by and large to the common sense observation that the wind doesn’t always blow when and where we might want it to. The National Grid doesn’t exactly support that viewpoint though, or at least, not to the same extent. In this report, they map out the expected contribution of different sources of energy to the Grid by 2020, and consider what measures they need to take in response to that changing mix.
Now their assumptions are, of course, open to challenge; and some of us might not want to see the same mix as they anticipate; but in this context, we can simply treat their scenario as a prediction, not a prescription. The precise mix of non-renewable sources doesn't significantly affect the argument here. They assume that wind will rise from 3.8GW out of 85.3GW in 2010/11 to 26.8GW out of 100.5GW in 2020/21. From 4.5% to 26.7%, therefore, with other renewable technologies providing a further 1.3%.
They say that will create greater uncertainties at times, although, as they point out, the dispersion of those uncertainties over a larger geographical area serves to smooth them to an extent. There are also other things which they can do, and are planning to do, to reduce unexpected volatility, such as improving their forecasting tools and methods, use of interconnections with other grids on the mainland – again, this is a way of spreading the effect of wind variability over a much larger geographical area and thus reducing its impact – use of smart grids, more storage capacity etc.
The report helpfully includes a little graph showing how much operating reserve is required at different levels of wind penetration into the mix of electricity generation. At 0%, the operating reserve required by 2025/6 would be a little under 5GW – i.e. that is the level of operating reserve required if there was not a single wind turbine operating in the UK. If the proportion of electricity being generated from wind by 2025/6 reaches around 30%, however, then the need for operating reserve rises to around 8GW – an increase of a little over 3GW.
Does that equate to 17 gas powered station? No, it does not. The capacity of such stations can vary – but the one being built at Pembroke, for instance, is rated at 2GW – which would mean a maximum of two extra gas stations to provide operating reserve to 30GW of wind turbines. Quite a different picture.
So, where does the need for 17 extra gas-fired power stations come from?
I’ve traced this report from DECC, which talks about the need to build 20 new power stations (fuel unspecified) by 2020. But it isn’t based on the need for operating reserve – it’s based on the fact that “A quarter of Britain’s capacity will need replacing before the decade is out, as old coal and nuclear plants come to the end of their useful lives” and the suggestion that “Demand for electricity could double by 2050, as we opt for electric vehicles and heating”.
There’s also this speech from the boss of Centrica, which argues that the fuel for those new stations should be gas. There’s perhaps just a hint of vested interest around that one, of course – “Major gas supplier says gas is the answer” would hardly be a surprising headline.
Then there’s this submission by Centrica to the Select Committee, which argues, inter alia, that since new stations are likely to be cycled on and off more frequently - because of the increased contribution from renewable generation - and to have longer periods when they’re not producing electricity, the operators should be incentivised (paid) to build the most flexible types of plant – which just happens to be gas-fired.
Even taken together, it’s hard to see how all of these factors could lead to the sort of categorical statement being made about 17 new plants for backup to wind, although I can see the glimmer of a basis for wilful misinterpretation.
I suspect though that the derivation of the 17 is much simpler than that. It is axiomatic to wind turbine opponents that there is a need for 100% operating reserve at all times for every turbine, regardless of any evidence to the contrary. If wind is projected to supply around 30GW of power, and if CCGT plants generate around 1.8GW each, then a simple division gives a number remarkably close to 17. The logic is impeccable, and the conclusion flows naturally from the premiss.
The problem is that the premiss is unsubstantiated, and not supported by those involved in actually running the system. It’s another example of the rule that arguing from axiomatic and unsubstantiated starting points generates more heat than light.
Posts
11 comments:
". . . the rule that arguing from axiomatic and unsubstantiated starting points generates more heat than light."
That is often as true of the pro-wind lobby as it is for the anti-lobby.
And you are right to mention (although you do so in passing) that we need far more energy storage - in fact I would say that was more important than prime generation, as the only times that we actually have a shortage of generation capacity is at peak times. And those are exactly the times when wind cannot be relied upon. On cold days in winter, for instance, wind contribution is minimal, and demand at its highest. A mismatch.
Siônnyn,
Agree - I don't like axiomatic arguments from any side in a debate.
And I agree with you on storage as well; it's a key element of a more renewables-based generation regime. The reason that I only mentioned it in passing was that I was trying to concentrate on one particular aspect of the debate - the derivation of the '17 power stations'.
John. The principle is substantiated by physics. Energy can neither be created nor be destroyed. It can only be transformed from one state to another. If the wind is not blowing, the energy is not available for conversion to electricity. If there is a demand for electricity at that time, then some other source has to be used to supply it. It's really quite disingenuous to use semantics and obfuscation to deny this. More seriously, you are failing to ask the more pertinent question of how loading on the grid (or micro grids) can be varied over time to avoid this dearth during calm periods. The real question is how we can adapt our energy consumption to make maximum use of renewable generated electricity when it is abundant, and minimise demand when it is not. To achieve this would also reduce losses in transmission and reduce losses by conversions under less efficient loading conditions. Something to consider?
Anon,
Yes, I understand the physics of that.
"If the wind is not blowing, the energy is not available for conversion to electricity. If there is a demand for electricity at that time, then some other source has to be used to supply it"
True, of course. And the same principle applies to all other sources of electricity. It's why the total generating capacity available to the Grid is always significantly larger than the capacity in use at any one time - and would be even if there were not a single wind turbine in place. It isn't the same thing, though, as saying that n power stations are needed purely to provide a backup for wind, let alone that those stations are on permanent 'spinning' standby. That is neither semantics nor obfuscation.
"More seriously, you are failing to ask the more pertinent question of how loading on the grid (or micro grids) can be varied over time to avoid this dearth during calm periods."
I'm not avoiding it; it's a key question. It just wasn't immediately relevant to the main thrust of this post, which was to challenge the '17 power stations just to back up wind' claim.
"The real question is how we can adapt our energy consumption to make maximum use of renewable generated electricity when it is abundant, and minimise demand when it is not"
I'd agree completely with that. A move to greater dependence on renewables and reduced dependence on thermal generation using 'fuel' of one sort or another does indeed require us to rethink the way we use (and store) electricity. The Grid report to which I linked contains some discussion around some of the issues involved with that, and I may well return to that in a future post. Again, it wasn't immediately central to the point that I was trying to make here - and trying to cover all aspects of a transition to renewables in one post would make the post too long - and repetitive, given that I cover some points in other posts over a period.
"To achieve this would also reduce losses in transmission and reduce losses by conversions under less efficient loading conditions"
Not sure that I'd agree with the bit about losses in transmission; they're often overstated somewhat. Best estimate I've seen is up to 2% on the Grid and up to another 6% on the distribution network; a total of <8%. Minor reductions there will not generate huge gains.
Losses in conversion is another matter, although I think that perhaps one aspect of a more renewable based electricity policy is that we might need to consider an increase in conversion losses. Using surplus electricity at one point in the cycle to electrolyse water, and then using that hydrogen to generate electricity at peak usage times is an inherently inefficient process in terms of energy losses, but may still be worth doing, to give just one example.
John - by disproving the exaggerated assertions of anti-wind people, you are not in fact proving your own assertion that Wind is a useful contributor to carbon reduction. The sums may be wrong, but the principle isn't.
I have yet to see convincing figures (after more than 20 years of wind farms) that demonstrate that they make a net contribution to carbon emission reduction. Do you have any?
My concern is that by blindly chasing Wind energy we are neglecting other, better sources of clean energy, like tidal and thorium based nuclear.
And as I said before, we should do far better in Wales to concentrate on energy storage, mostly in the shape of pump storage (not necessarily huge projects like Dinorwyg) than looking to generate more electricity when we already produce far more than we use.
Siônnyn,
"by disproving the exaggerated assertions of anti-wind people, you are not in fact proving your own assertion"
Agreed; and I don't claim that I have. Disproving A doesn't prove B; it is though an important part of debate.
"The sums may be wrong, but the principle isn't"
Not sure what you mean by that. To the extent that an argument is based on a set of numbers, that argument is inevitably undermined by errors in the mathematics.
"I have yet to see convincing figures (after more than 20 years of wind farms) that demonstrate that they make a net contribution to carbon emission reduction"
I'd accept that that is a difficult question to give a definitive answer to. There are a number of problems associated with it, not least the fact that demand for electricity has been growing over the long term (even if the recession has dented that growth somewhat); and the contribution of wind has been small to date. How much carbon reduction would you really expect from an installed wind capacity which accounts for only 4.5% of the total generating capacity? By definition, not a lot.
What I can say with confidence however is that every Kwh of wind-generated electricity would otherwise have had to come from thermal power stations; to the extent that wind energy displaces fossil-fuel, it saves carbon during generation.
A full comparison however involves whole lifecycle carbon costs. There are figures on that; I'll try and include references to them in a future post. The problem, though, is that any set of figures inevitably depends on a set of assumptions, and unless those assumptions are agreed and understood, then meaningful debate on the figures based on them becomes impossible. And actually, returning to the earlier point, that's part of the reason why the assumptions of opponents need to be challenged.
"My concern is that by blindly chasing Wind energy we are neglecting other, better sources of clean energy, like tidal and thorium based nuclear"
I don't seek to use wind exclusively. Wind has a place in the overall mix, and many of the arguments used against that are dodgy to say the least. But seeking to refute those arguments and supporting a degree of wind generation is not at all the same thing as supporting a wholly wind-based generation regime; that really would be madness.
Wind is, however more fully developed as an immediately deployable technology than tidal energy. I want to see us using both.
I'm much less convinced about the thorium option, although I'd be happy to see further research being done on it. It is, of necessity, further in the future than options which can be deployed now.
"we should do far better in Wales to concentrate on energy storage ... than looking to generate more electricity when we already produce far more than we use"
The problem with that is that of the excess electricity which we currently produce, the majority comes from power stations (coal, nuclear) which are due to close at some stage, and which we need to replace. We cannot simply ignore that replacement issue, and need to be planning to get our electricity from somewhere. Whilst Wales is a surplus producer now, we could easily become a net consumer of electricity produced elsewhere unless we secure our own future.
John - I mentioned thorium reactors here without really explaining what I meant. Here is an interesting, though rather breathless explanation of the advantages of thorium - in the shape of Liquid Fluoride Thorium reactors for energy generation -http://www.youtube.com/watch?v=N2vzotsvvkw&feature=player_embedded
The south Wales coalfields have vast deposits of thorium, which are regarded as a nuisance rather than a resource at the moment, as they contribute to raised background radiation. The reactors can be scaled from tens of MW to Gw - and can be deployed locally - reducing the need for high tension power lines. The safety hazards are minimal, and the dangerous waste a tiny fraction of that produced from conventional water cooled uranium fuelled reactors.
A piece of thorium fluoride the size of a marble provides all the power power that is consumed by and American for the whole of his life. A reserve the size of a football field can provide the total power used in the World for a year - and that includes non-electric power, but liquid fuel and gas as well.
One of the problems with the drive for renewable (ie exclusively WIND in this country) is that funding for R&D to develop home grown LFTRs has been curtailed, in favour of subsidising wind power, and it is likely that China and India will be the first to market with fridge sized prefabricated units, possibly within 5 years.
The Welsh government should have a policy on LFTRs, embracing it ahead of time, and encourage Welsh participation in R&D.
Siônnyn,
Thorium has started to receive a lot of public attention these days, and I'd accept that it seems to have a number of advantages over uranium as a nuclear fuel. I'd be careful though about seeing it as some sort of 'silver bullet' which is going to resolve all our energy problems, which is the way it has sometimes been presented.
Whilst the theoretical science is pretty well understood, there's quite a bit of research and development needed before it can be deployed, and even once we get to that point, we're talking about a lengthy lead time for the building and commissioning of reactors.
And, although it may produce hugely reduced quantities of long-lived radioactve waste, 'hugely reduced' is not the same as zero; it's still a problem that needs resolution.
So - potential contributor to meeting needs in the future, but some time off, and more research and development needed. And, in the meantime, we still need to replace coal and nuclear stations scheduled to close.
I think that the 'five years to market' is rather optimistic.
John - renewables are not the 'silver bullets' that a lot of people paint them - indeed, I and many other are very sceptical about whether they are bullets at all - especially wind.
Thorium does not bring the large scale construction problems of heavy water (they can be built in factories and delivered on the back of factories), they do not require very high pressure (very dangerous) vessels, they cannot melt down, and they only produce 0.01% of the waste - which is significantly shorter lived than spent uranium - and as an added bonus - it can be used to burn the products of uranium reactors, and extract most of the untapped energy from it!
The open engineering questions should not be allowed to deflect mankind from this technology. It is only a matter of time and effort.
I bet you a good lunch that India or China will have a production model in place within 5 Years!
Just another thought - I suggest that those who espouse Wind power as the answer to global warming agree to use power only when the wind is blowing!
Would you sign up to that?
Siônnyn,
I don't doubt that Thorium has the potential to play a rôle, but I simply don't believe that the technology is as well-advanced as you seem to be suggesting. Certainly, there have been some limited trials, both of purpose-built reactors and of using thorium in adapted reactors, and the science is well understood. But the engineering is less well-developed, and, as of today, it is not a technology available for deployment on a wide scale. As I said in an earlier comment, further research and development is something I'd support, but the claims are currently being over-hyped, and cannot be fully substantiated until the R&D work is done.
"they only produce 0.01% of the waste"
I'd be interested in the source of that figure. I've seen a range of suggestions - from 10% at the top end to 0.001% at the bottom. Your figure is certainly within that range, but the mathematician in me is instinctively sceptical of the certainty of any range which spans 4 orders of magnitude.
"India or China will have a production model in place within 5 Years"
Maybe, maybe not. Predictions of the future availability of technology are always dangerous; proponents tend to over-optimism, opponents to over-pessimism. I try to be open-minded, but without rather more certainty than exists today, I wouldn't put other things on hold until we find out.
"those who espouse Wind power as the answer to global warming agree to use power only when the wind is blowing"
If you can find me someone who really espouses wind power as the answer to global warming, I'll ask him or her. But I don't know anyone who does. What I, and I think most other supporters of wind, argue is that wind has a rôle to play in an energy mix which includes a range of renewable resources. We can't depend on it totally, but it can play a rôle in meeting part of our total energy needs.
Post a Comment