Thursday, May 21, 2009

Hot air and wind
The importance of numeracy

I am disappointed to see the - usually interesting - Heresiarch write a profoundly mistaken and, frankly, ignorant post attacking wind power. Now, I don't like dirty hippies any more than the next reactionary, but this is daft:

Why wind? As a giant wind-farm opens in Scotland, it should be obvious that wind power is not the future of energy supply in Britain or anywhere else. Wind-turbines are expensive and inefficient, they ruin the landscape, they are noisy when they work (which isn't very often) and they kill birds. In Taiwan, noise pollution from a wind farm has been held responsible for the death of four hundred goats. The amount of electricity they generate, even now, is negligible. It is said that the vast new Eaglesham Moor plant could potentially power the whole of Glasgow - but that is only when it is operating at full capacity, which even in a country as windy as Scotland is not even half the time.


As David MacKay would say, what we need is fewer adjectives and more numbers. Let's find them:

(i) "Oh noes, teh poor birdies!" MacKay [Without Hot Air, p63-64] notes that in Denmark, where wind generates 9% [!] of the electricity, 30 thousand birds a year are killed by wind turbines - but 1,000,000 are killed by cars! In the UK, a remarkable 55 million birds are killed by cats, and a similar number by flying into windows. If you are concerned about windmills, you must be distraught about cars, cats and windows! Unless, of course, the bird loving is just window dressing.

(ii) "but the property values by which I mean the integrity of the landscape" Didcott power-station used to have an annual open day (this was something of a holiday treat). I used to love it, being in awe of such a mighty chunk of engineering - but I don't think you could call it "landscape-enhancing". Other things you couldn't call it were "cheap" or - Carnot cycles being what they are - "efficient". 

(iii) "Which isn't often" We'll have a go at quantifing this in a bit, when we discuss the failings of James Lovelock.

(iv) The utterly surreal: "In Taiwan, noise pollution from a wind farm has been held responsible for the death of four hundred goats." Well, call me Dr. Picky, but I going to be politely sceptical about this remarkable claim. Martin at the Lay Scientist feels the same way, and is prepared to bet no fewer than two goats that the wind farms are innocent of the charge of goaticide.

(v) "The amount of electricity they generate, even now, is negligible." Albeit not as negligible as the amount of electricity now generated by the Heresiarch's chosen alternatives of tidal power and "tapping into the jet stream of the upper atmosphere"[sic].

(vi) A statement that speaks for itself:  " Geothermal energy may be even better. This taps directly into the inexhaustible energy of the earth itself, and (technicalities aside) consists of little more than a hole in the ground. It has almost no environmental costs." I think it may be time for my long-planned "Introduction to Thermodynamics" series, which will presumably drive the remaining 3 readers of this blog. I think that's the only way I can explain all the problems with this statement, although if anyone else wants to have a go they could start with defining what we mean by hot rocks, where we can drill the hole, what the rate of thermal conduction thru' rock implies for the rate that heat can be extracted, complete with a parable about aquifiers and oil-wells to make concrete the abstract.

Poor MacKay is enlisted in support for Heresiarch's argument:
Even as the new plant opens, plans are announced to expand it still further (although it already covers 55 sq. km), while over in Shetland an even more elaborate wind-power scheme is attracting increasing opposition. A BBCreport quotes Professor David MacKay of Cambridge, who said that a "100-fold increase" in wind farms in Britain would be necessary to achieve the government target of a complete decarbonisation of our electricity supply system by 2030. The only other alternative to carbon generation he mentioned was nuclear power - itself an outdated and non-renewable technology that brings with it its own problems.

Actually, were the Heresiarch to read MacKay's excellent book Without Hot Air - which you can do for free online here - he'd find out that in ALL five scenarios that MacKay sketches out for a decarbonized Britain, wind power makes contributions from 4% (plan N, WHA pages 208-209) to 64% (plan G, WHA page 210). In the book, he discusses desert-based solar power and carbon-captured - "clean"- coal as well as nuclear.

The quotation from Lovelock is puzzling for two reasons: (i) the specific claim that turbines have an efficiency of 17%, which must be a simple misunderstanding, although there are less charitable explanations. Anyone with GCSE Maths can calculate the efficiency for a disk-like turbine as a function of wind-speed , and anyone with either a bit of calculus or EXCEL skilz can show the maximum efficiency of such a turbine is 59%. This is Betz' law, for goodness sake, it's been around for the best part of a century. Now, actual turbines will show a lower efficiency than this, being made of steel rather than algebra, but Mitsubishi quote efficiencies of 40%.  Also note that the specific power of the wind increases with the cube of velocity, so you get much more available at higher windspeeds.  (Nuclear advocates like Lovelock might also recall that a nuclear power station is just a kettle, albeit a nuclear powered one: it has turbines, too, to generate electricity. Any heat engine is going to be limited by some efficiency - the World Nuclear Association reckons you can get to 50% efficiency using super-critical water in the heat exchanger) (ii)  I simply don't get his wider point. The idea that a turbine farm is sold as producing x MW of power, but only actually produce 0.17x MW in nonscence - everyone knows the difference between capacity (the peak power attainable by a turbine) and capacity load (the expectation value of the power, given local average wind speed) - at least, anyone offering opinions about energy policy should. Incidently, the capacity load of a windfarm in the UK of a good site is typically about 30%
(iii) Further, the idea you need to back up every MW of wind-power with fossil fuels is simply erroneous. Hydroelectric batteries, where surplus electricity is used to pump water uphill, and stored as gravitational potential energy, can and are used to even out the supply. As I say, the charitable explanation is that Lovelock - an extremely eminent man with something of a cult following - has not informed himself as well as his admirers might hope. 

We finish off with a fact-free smear: 
They make their supporters feel morally superior to their opponents, who can be dismissed as selfish Nimbys. The uglier the wind farms are, the more they ruin the environment, the better: for their very unattractiveness draws attention to the sacrifice that they represent. They are Gaia's temples. The clacking of their sails is like a prayer offered up to Nature to forgive our environmental sins. It's mad.
Greens may be fanatics, lunatics, anti-technology, cruel to children or bad in bed : but what has this to do with the merits and demerits of wind power? I also think persons with scientific pretentions ought to support remarkable claims - for example, that "the more [wind farms] ruin the the environment", the better Greens like them - with evidence. Also, if you're going to run with "T3h wind-farms r prayer-weel 4 Gaia worshippers" you'd be well advised not to quote so liberally from James Lovelock

The Yorkshire Ranter has suggested  the problem that macho techno types have with wind: it is "gay electricity". It isn't as hot as a decarbonised coal furnace, and it hasn't the appeal of mighty erections piercing the troposphere and riding the gulf stream like a cheap strumpet.

14 comments:

John B said...

Excellent post.

And I'm fairly sure they'll find the goats were killed by being pushed in front of aeroplanes.

The Heresiarch said...

Yes, that is quite an effective demolition job. Though I'm sure if I took the trouble to make myself conversant with all the facts I would be able to answer most of your points.

I plead guilty to over-egging the rhetoric. My last paragraph was not a smear, however: I really do think that the reasons for the concentration on wind power are partly psychological. It is because the wind-farms are so visible, and so invite loud opposition, that they seem virtuous to political leaders. There's a parallel with brutalist concrete architecture, which also seemed progressive and "modern" partly because it was so ugly.

On the practical points, I think it's unarguable that wind-turbines are inefficient. You seem to be gauging their efficiency when they are working at maximum capacity. Lovelock's figure, as I understand it, comes from a 2005 German report which concluded that the savings from wind-farms were more than offset by the increased inefficiency of conventional power-stations which they supplement.

The central point of my argument was actually the quote from Gould, which you didn't take on. My suggestion is that wind-power is diverting resources from potentially more efficient forms of carbon-neutral energy because it got there first, has high visibility and so much investment has already gone into it. Obviously, it offers more generating capacity today than the alternatives. The question is, though, whether if resources were switched from wind-power to the alternatives, would there be more or less capacity twenty or thirty years down the line than there would be if we continued privileging wind-power over other renewables. My guess - and I'm afraid it is only a guess - is that the answer is that there would be more.

LemmusLemmus said...

Data point: 6.4% of Germany's energy is provided by wind power (source: German Wikipedia). That's despite most of the country being much less windy than Denmark (evidence: anecdotal).

Political Scientist said...

Hello, everyone.

John : Glad you liked it. Thank you for the Julian Gough story, it’s brilliant. Have you read the pig-napping one, too?

LemmusLemmus: thank you - between that and The Heresiarch’s post above, I’ve identified how Lovelock has made his mistake.

Political Scientist said...

Lord Heresiarch: Thank you for commenting over here, I’ve posted a copy of this comment over at your place as well. I usually enjoy your blog, and I have no problem with hyperbole - indeed, this post indulges in it - but I do have a problem with erroneous assertions and wonky logic.

You write: “Though I'm sure if I took the trouble to make myself conversant with all the facts I would be able to answer most of your points.” But what if I am sure that I will be able to answer all of your answers to my points? Which will be quite sufficient to win my case, at least until you are sure that you will be able to answer all my answers to... but that way lies madness. It’s as if Borges quit being a librarian and joined a debating team with David Hilbert and MC Escher.

Further, you write: “My last paragraph was not a smear, however: I really do think that the reasons for the concentration on wind power are partly psychological. It is because the wind-farms are so visible, and so invite loud opposition, that they seem virtuous to political leaders. There's a parallel with brutalist concrete architecture, which also seemed progressive and "modern" partly because it was so ugly.”
Well, you claim that Greens like wind farms the “more they ruin the environment” and describe this as “mad”. That’s a bit like a smear, isn’t it? And I say that you don’t provide any evidence for these claims, because you don’t provide any evidence for these claims. I can’t, off hand, think of any Green party proposals to concrete over the Lake District, or any environmentalists who actually want to destroy the environment. In addition, as I am a physicist rather than a psychiatrist I am not qualified to comment on people’s personal peccadillos. All the less so, on your view, as I think the South Bank is beautiful and even had a soft spot for the NAPL building, back in the day.

Rather than recursive declarations of victory on the basis of unmade arguments and unknown facts, or amateur hour psycho-analysis, it’s probably more productive to focus on facts - things that can be measured and checked and calculated and understood. With that in mind, I’d like to examine the two issues you raise in your comment.

Political Scientist said...

First, regarding Lovelock, you write:

“On the practical points, I think it's unarguable that wind-turbines are inefficient. You seem to be gauging their efficiency when they are working at maximum capacity. Lovelock's figure, as I understand it, comes from a 2005 German report which concluded that the savings from wind-farms were more than offset by the increased inefficiency of conventional power-stations which they supplement.”

I think we’re talking at cross purposes - that’s probably my fault for not being clear in the post above. Let me try again. To say somethings is “inefficient” is a truism: all processes are inefficient. In order to say something meaningful about energy generation, we need to quantify the efficiency in order to compare different processes. You write “ You seem to be gauging their efficiency when they are working at maximum capacity”.
This is not the case: I distinguish between “capacity” (which is to say, the energy generated when the turbine is going at or close to its maximum speed) and “capacity load” (which is to say, how much of the time the turbine is operating at maximum capacity). Lovelock talks about “efficiency” meaning “capacity load” and he picks (I choose this verb deliberately) 17%, implying that this is a figure that ordains in all times and in all places. I’ve very much hope he got it from the 2005 report on Germany, for reasons that will become clear. MacKay quotes factors for the UK of average load for the UK of 28%, rising to 36% for North Hoyle (off-shore, near Wales) (WHO, p.268), and notes that the “load factor varied
during the year, with a low of 17% in June and July.”. I’m sure you will agree that it would be very dishonest to choose the lowest value and pretend that it were universally true. Of course, picking a German value when discussing UK power would hardly be a shining example of intellectual rigour, -as LemmusLemmus notes anecdotaly, and as MacKay records (WHO, p.267) - Germany isn’t very windy at all, with load factors of 19%(Germany) vs 28% (UK).

Load factors apply to other form of powers, too: Lovelock’s nukes, for example. Sizewell B has to shut down for 140 days a year - a load factor of 62% (link via the Yorkshire Ranter).

Further, Lovelock makes the simply untrue statement, that “ 83% of the electricity that should have come from wind has to be made in coal-burning power stations that can never work at optimum efficiency because they are forever adjusting to the fluctuating flow from wind generation.” No no no no no no no. As I explained above, this line of reasoning neglects hydroelectric storage [John B also points out in the other thread that an intermittent power source can reduce carbon emission, by using a power station that can rapidly start up, such as gas] This error is independent of Lovelock’s cherry picked figure.

His statement “The Germans, who have invested more than anyone in this form of energy, are finding, according to Der Spiegel, that despite more than 17,000 wind turbines across Germany the nation is emitting more CO2 than before it built them.” as it stands is a non-sequitor. After all, presumably it would have emitted even more if it hadn’t built 17,000 wind turbines! The questions are, “how much?” and “was it worth it it?”, neither of which Lovelock appears interested in addressing.

Political Scientist said...

Second, you write:
“The central point of my argument was actually the quote from Gould, which you didn't take on. My suggestion is that wind-power is diverting resources from potentially more efficient forms of carbon-neutral energy because it got there first, has high visibility and so much investment has already gone into it. Obviously, it offers more generating capacity today than the alternatives. The question is, though, whether if resources were switched from wind-power to the alternatives, would there be more or less capacity twenty or thirty years down the line than there would be if we continued privileging wind-power over other renewables. My guess - and I'm afraid it is only a guess - is that the answer is that there would be more.”

I personally believe that there’s going to be a pretty diverse range of alternative energy, and there’s plenty of stuff to be investigated. Indeed, plenty of stuff is being investigated. I have a lot of difficulty in seeing wind providing in excess of 20% of the energy budget - but (i) even 10% is better than a poke in the eye with a sharp stick, and (ii) 10% from wind is 10% that doesn’t have to come from clean coal, nukes, tides, solar, or even geothermal. (BTW, I really think you should re-examine your assumption that geothermal power-plant “consists of little more than a hole in the ground.”) It also makes sense to focus on technologies that our ready for/close to roll-out, so that mass-production can cut costs of plant.

If you are interested in energy policy, I hope you will read David MacKay’s book, which is available online for free. It really is very good, although I think he’s underestimates solar energy a bit (although not sufficiently to affect his argument). I might post on this at some point. I hope to write a few posts about climate change and energy policy generally over the next few months, and am flirting with the idea of a Great and Glorious Crusade against Christopher Brooker.

The likelihood of series of thermodynamics posts has increased since seeing an article in The Register today, assuming it is as ridiculous as a first read suggests.

LemmusLemmus said...
This comment has been removed by the author.
LemmusLemmus said...

I'm no expert in these matters, but isn't "capacity load", in and by itself, uninteresting? Wouldn't you want to look at the actual benefits (energy produced) and the (monetary and nonmonetary) when assessing various ways of energy production? To take a simplified example, technology A yields X at a price of Y, while technology B yields 2X at a price of 1.5Y, so technology B is better, no matter what the respective capacity loads are, right?

Someone please educate me if I'm wrong on this.

Political Scientist said...

"I'm no expert in these matters, but isn't "capacity load", in and by itself, uninteresting? Wouldn't you want to look at the actual benefits (energy produced) and the (monetary and nonmonetary) when assessing various ways of energy production? "

Capacity loads are extremely important, because you need some power all the time - you need to know how much you'll need to backstop the renewable with hydroelectric batteries or e.g. gas-fired power stations. Certainly you need to look at energy produced - but in designing a resilent energy policy, capacity loads are essential, too.

The Heresiarch said...

PS: If you posted those comments over at Heresy Corner, I'm afraid they didn't come out.

My point about not needing to know all the facts - deliberately paradoxical of course - was a reflection of the fact that there is clearly a debate about the merits of wind-power as a source of energy, and that there are plenty of opponents who are expert in the field.

Besides, your comments do leave at least one glaring opening, which I'll leap into. You write:

(i) even 10% is better than a poke in the eye with a sharp stick, and (ii) 10% from wind is 10% that doesn’t have to come from clean coal, nukes, tides, solar, or even geothermal.

10% now is not necessarily better than a poke in the eye, if there is a realistic possibility that investment in some other technology would produce a future gain well in excess of the 10% gained from wind-power.

Similarly, I don't understand why it should be an advantage that the 10% "doesn't have to come" from the alternatives. You could equally say that getting the 10% from one or more of the alternatives is 10% that "doesn't have to come" from wind generation. And since wind power has drawbacks (both aesthetic and in terms of load efficiency - thanks for the correct terminology) that an alternative might not have, that might be the more significant gain.

As for my smears against wind advocates - what of the smears of wind-advocates themselevs? For example, Mr Miliband's comment that disliking wind turbines ought to be "socially unacceptable".

Political Scientist said...

Lord H,

I respond to your latest post here.

Further to your comment above, you are mistaken about this being a gaping opening: the argument could only be appled to any power source that could provide all our energy needs. As it simply a matter of arithmetic that there is no single source of energy that could do this, it is an argument for wind being part of the energy mix.

Alex said...

Lovelock is seriously wrong on that; coal-fired generation is baseload, not peaker, power. I.E, because it is silly inefficient to run Drax below 100% and it takes hours to fire 'er up, they use the coal (and nuclear) stations for baseload.

If there is a shortfall, you fire up a gas-fired power station, because being essentially an aircraft engine tied to a shed, it can start up in minutes. This is termed peaking power, because you need it for the peaks in demand, and it attracts a premium price. This really is National Grid 101.

More broadly, the big question with regard to capacity factors is load-following; the aim is to keep supply and demand in balance, so what matters is whether the variability is "load following" or not. This is one of the reasons why people are interested in "smart grids"; if you can synchronise demand and supply, you don't need to store power and you don't need as much expensive peaking power.

So far the record wind power contribution to the grid was about 40%, in Spain a couple of months back.

Political Scientist said...

Hello Alex,

I hadn't heard about the Spain result - that's seriously impressive.

I think Lovelock has become a bit of a hack, at least regarding nuclear power boosterism. I haven't read his latest book, but that article is not a good sign. Wind power does make some people very cross, doesn't it?