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The concept of "peak oil" has been bandied about for some time (see this question: Is peak oil still set for 2013?) by people who believe the world hydrocarbon stocks will soon be so depleted that annual production will soon decline whatever we do about it.

A recent article in The Register suggest that a similar problem might arise sooner than expected with wind energy.

The gist of the argument is that environmentalist proponents of the use of wind power as a way of generating electricity and avoiding carbon dioxide emissions have been far too optimistic in their forecasts of the potential of wind power. As the source article for the Register story says in its summary (my emphasis):

Estimates of the global wind power resource over land range from 56 to 400 TW. Most estimates have implicitly assumed that extraction of wind energy does not alter large-scale winds enough to significantly limit wind power production. Estimates that ignore the effect of wind turbine drag on local winds have assumed that wind power production of 2–4 W m−2 can be sustained over large areas. New results from a mesoscale model suggest that wind power production is limited to about 1 W m−2 at wind farm scales larger than about 100 km2. We find that the mesoscale model results are quantitatively consistent with results from global models that simulated the climate response to much larger wind power capacities. Wind resource estimates that ignore the effect of wind turbines in slowing large-scale winds may therefore substantially overestimate the wind power resource.

Is this argument plausible? Have believers in the potential of wind power significantly overestimated its potential?

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matt_black
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2 Answers2

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No, The Register has misrepresented the story.

There are several parts to this question. The summary is:

  1. "Peak Wind" is a myth: there is nothing similar in wind to how hydrocarbon stocks will get to such a depletion point that annual production will decline inexorably thereafter.

  2. The modelling methodology smackdown - Have previous estimates over-estimated the global onshore wind resource? This is currently unanswerable. There are two conflicting modelling methods - the aggregated micro-scale; and the meso-scale. The meso-scale modelling in this new Adams & Keith paper (and in the other related papers by Lee & Keith, and the Lee & Kleidon paper in Davephd's answer) cannot yet be validated, because there is insufficient information about the performance of wind farms greater than 100km2 in area - we haven't built them yet. Until we have real-world data on very large wind farms, we cannot say which modelling method is more accurate.

  3. Does it matter? No, it doesn't. There is a wide range of different estimates of global onshore wind resource, that are derived using different modelling methods. They all agree that the global onshore wind resource way exceeds global electricity demand, many times over. And in the absence of validation of meso-scale modelling, it will not get used for wind-farm design, which will continue to use micro-scale modelling.

"Peak Wind" is a myth

The original journal article is here. The concept of Peak Oil, which Peak Wind is being held analagous to, is the simple notion that when depleting a finite non-renewed resource, there comes a time when the extraction rate reaches a maximum, and thereafter declines year on year.

The paper by Adams & Keith that The Register claims to be reporting on, makes no such claim for wind: there is no claim in the paper that there is a wind resource which will become exhausted. That's because wind is constantly renewed by incoming solar radiation.

A typical Peak Oil peaks then depletes. Whereas global wind generation continues to increase as global capacity increases.

Asymptotic wind production

The paper in question models the output of power per unit area, and predicts that it will level out at around 1.2W/m2. Which means that with increasing wind capacity installed, wind output would continue to be a rising curve, and would not show a peak and a down-turn.

Instead, the paper is claiming that there are diminishing returns: that is, that building more wind will continue to yield more electricity, but at a declining rate. This is something that has been known for a long time. The difference is that Adams & Keith are claiming that it will happen faster than previously modelled, and that the global potential onshore wind resource is only a few times global electricity demand, rather than many times it.

Their specific testable claim is that:

wind power production is limited to about 1 W/m2 at wind farm scales larger than about 100 km2

As yet, we have very few windfarms larger than that, so this remain a theoretical exercise. There are plans to build windfarms substantially bigger than that over the next 10 years, so we will find out soon enough.

The modelling methodology smackdown

This paper is part of a long on-going discussion in the literature about the most appropriate way to model the wake effects of large onshore wind farms. The difference boils down to whether one models from the wake of an individual turbine upwards (the Jacobson method of aggregating from the micro-scale), or whether one uses

a parameterization of the atmospheric effects of wind turbine arrays

as Adams and Keith do in the paper in question (and as Keith & Lee do, and Lee and Kleidon do). This is to a degree a question of faith, as to whether the parameterization, in throwing away the detail of the individual turbine, adds to, or detracts from, the usefulness of the model. It's a question of faith, because as yet we don't have enough data from wind farms over 100 square kilometres to validate the meso models.

It's an interesting discussion about the fundamentals of atmospheric modelling, not least because Mark Z Jacobson is the man who literally wrote the book on it. His papers on the subject are listed here.

Does it matter for (inter-)national policy?

There are no implications for (inter-)national policy. Earlier estimates are of a global wind resource at least an order of magnitude greater than global electricity demand, so a quartering of that resource (as Adams & Keith predict) still results in potential global onshore wind production exceeding global electricity demand. That is to say. there is still no meaningful limit on the onshore wind resource. And that's ignoring the massive potential in the offshore wind resource.

Does it matter for wind-farm design?

As of now, no it does not: individual wind farms still get designed using wake-modelling at the level of individual turbines, rather than relying only on Adams & Keith meso-scale modelling. If there comes a time where empirical evidence supports their parameterised meso-scale modelling, then that may get used, because it's computationally simpler, faster and requires fewer inputs. Onshore wind farms larger than 100km2 will get built in the coming decade, so the testable hypothesis I mentioned above will get tested.

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410 gone
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    Good summary of some of the key issues. But I think you take The Register headline over literally: I think they were being a little whimsical in using the term "peak wind" to mean future wind resource would decline. They were pointing out that some estimates of wind's potential are ridiculously over optimistic. I think it also argues that, given realistic constraints on wind's potential, we should not expect it to meet a large proportion of world demand, ever. You still argue the opposite. – matt_black Feb 28 '13 at 17:34
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    @matt_black To be fair, your whole first paragraph was about peak oil and you even called the plateauing of wind power a "similar problem", when really the only similarity is that the Register called them both "peak" something. I think it fair for the answer to be too literal with the headline when it reads like the question is as well. And even if the estimates are ridiculously over optimistic, it doesn't matter - both sides have estimates for what will happen in fifteen to twenty years, and if the estimates *are* over-optimistic we'll have plenty of warning to build fewer wind farms. – Tacroy Feb 28 '13 at 19:27
  • "That's because wind is constantly renewed by incoming solar radiation." I'm skeptical. The amount of solar radiation that reaches Earth is limited. The amount that's turned into wind energy is more limited. The amount of that wind energy that can be harvested by people is even more limited, etc. There is certainly a maximum number of watts that can be harvested from wind, and, like peak oil, a maximum that can be harvested economically. – endolith Feb 28 '13 at 21:49
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    @endolith - you apparently don't understand the difference between renewable and non-renewable resources, and the meaning of "peak oil". There is a fixed amount of oil on Earth. No more will be added during time scales relevant to humans. That makes it a non-renewable resource. Wind, however, is derived from solar radiation, which newly arrives every moment. While there is certainly a ceiling on the amount of wind existing at any one moment, the volume of energy humans are able to extract at that moment *will have no impact whatsoever* on future wind resources. It is renewable. – Drew Mar 01 '13 at 03:37
  • @AndrewHeath: But the premise of the article is that there's a maximum amount of power that can be extracted from the wind (which is obviously true), and that this limit may be reached quickly. It's irrelevant that the total amount of energy is unlimited. It's the *rate* at which energy can be produced that's important. – endolith Mar 01 '13 at 03:57
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    @endolith - That's not a **peak**, that's a **ceiling**. A peak implies *impending decline*. The terminology is poorly applied to wind power. Your first comment shows that you equate peak oil and peak wind to be the same when they absolutely are not. **Max Wind** and **Peak Oil** would be the correct characterization. – Drew Mar 01 '13 at 05:58
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    I'm beginning to wish I hadn't used the (provocative but not-intended-literally) headline. The real claim is that wind-power advocates have used ridiculously overoptimistic estimates of wind's potential (and have ignored economic limits as well). Neither the Register or my question intended to imply anybody thought available wind power would **decline**. PS "peak oil" is controversial despite the fact that all finite resources will inevitably peak, but because there is a dispute about what causes the peak: economics or resource depletion). – matt_black Mar 01 '13 at 12:46
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    @matt_black as my answer says, both the meso- and the micro- scale modelling show onshore wind resource is much greater than global elec demand, so the difference between forecasts don't really matter in the real world. It's just a methodology spat between two schools of modelling that's been going on for at least 8 years to my knowledge, and probably more. Until we've got a few meso-scale windfarms (>100 sq. km) then neither of the modelling methods can be validated for that scale. – 410 gone Mar 01 '13 at 14:48
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    As a (sometime) wind farm designer, I'd disagree that wake models used in their design don't take full-array effects into account, although discussion of which model is "right" is always spirited. Unless you're lucky enough to be designing for an unbounded featureless plain, your layout will always be subject to compromises from terrain, habitat, vegetation and noise receptors. Hence energy density in large projects will always be less than ideal. The Reg also seems to delight in taking a renewables-negative stance for no reason I can explain. – scruss Jul 26 '14 at 16:33
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    @scruss Ah, I see what I've written in that last paragraph is unclear. What I meant was that within farm design, the level of resolution is turbine level; I didn't mean to imply that full-array effects aren't taken into account; but rather that farm design uses the detail available at turbine-level to get the full-array effects right (that is, they use Jacobson-scale modelling or finer, rather than coarse Keith-scale modelling). – 410 gone Jul 26 '14 at 16:39
  • I'm pretty sure a hybrid approach is being used by many people these days, but I'm just a practitioner, not a wake theory type. The often-cited Salmon, J.R. owes me a beer, so I'll ask when we next meet. I still hold that Wm⁻² isn't a useful metric for large onshore wind farms, as the opportunities to develop huge open spaces near useful electrical transmission are vanishingly rare. – scruss Jul 26 '14 at 18:10
  • @Oddthinking graph 1 is from a hubbert curve : https://en.wikipedia.org/wiki/Hubbert_curve graph 2 is from a Beverton–Holt model: http://www.fao.org/docrep/006/X8498E/x8498e0b.htm – daniel Sep 23 '17 at 20:00
  • @EnergyNumbers While of course it is silly to use the term "peak wind" in analogy with "peak oil", there is a peak (as opposed to asymptote) in electricity generation per area versus installed capacity per area, as shown in Fig. 1A here: http://www.pnas.org/content/113/48/13570.full – DavePhD Sep 28 '17 at 14:15
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    Amazing level of expertise in this answer, and by many in the comments, as well. Thank you (and scruss)! – PoloHoleSet Sep 28 '17 at 14:59
  • @DavePhD of course there's a peak in generation per unit area versus installed capacity: that's not news, and it's not relevant to the claim here. – 410 gone Sep 28 '17 at 16:25
  • @EnergyNumbers not "electricity generation per area versus installed capacity ", electricity generation per area versus installed capacity per area (which is that same as energy generation versus installed capacity). – DavePhD Sep 28 '17 at 16:29
  • @EnergyNumbers and yes is news to some because the 2016 paper states "Note that the generation rate does not 'saturate,' as suggested by ref. 8, but rather generation reaches a maximum limit, beyond which electricity generation is reduced due to the further slowdown in wind speeds" – DavePhD Sep 28 '17 at 16:31
  • @DavePhD yes, that's what I understood you meant. And of course there's a peak: have a think about the minimum possible spacing between turbines. (clue: we normally refer to the spacing in terms of number of rotor-diameters; for onshore, a 3Dx5D grid was fairly standard for a long time) – 410 gone Sep 28 '17 at 16:31
  • And either Miller has misunderstood [8], or is playing silly games: [8] is about maximum yield per unit horizontal area, which is what the claim is about here. – 410 gone Sep 28 '17 at 16:33
  • @EnergyNumbers The point is that there is a maximum in electricity production, at finite, as opposed to infinite, installed capacity. This is contrary to the word "saturation" which reference 8 used in its title. It is also different from the shape of graph shown in the this answer. – DavePhD Sep 28 '17 at 17:14
  • @DavePhD no, it's not contrary to saturation, and it's not contrary to the graph shown. Because no one (other than, apparently, you) ever considered infinite capacity per unit area. Did you have a think about minimum possible turbine spacing? Did you understand the clue? Let me help a bit more. What would a turbine spacing of 0.9D mean? – 410 gone Sep 28 '17 at 20:23
  • @EnergyNumbers This answer refers to "rises towards an asymptotic maximum" and "with increasing wind capacity installed, wind output would continue to be a rising curve, and would not show a peak". Now you are denying this in you comments. – DavePhD Sep 29 '17 at 11:25
  • What are missing labels on the graphs, wind power output vs time? vs installed capacity? vs Vegemite left? – daniel Sep 29 '17 at 11:29
  • DavePhD - you are talking about power per unit area with increaing capacity installed per unit area. Whereas both the question and my answer are talking about power per unit area with increasing total capacity across an increasing area. – 410 gone Sep 29 '17 at 13:39
  • @daniel not needed in this case, as readers who are smart enough will work it out: it's not that difficult, given the huge amount of context around it. Do you need a clue? – 410 gone Sep 29 '17 at 13:41
  • @Sklivvz I've removed the graphs. – 410 gone Sep 30 '17 at 07:39
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According to Wind speed reductions by large-scale wind turbine deployments lower turbine efficiencies and set low generation limits Proceedings of the National Academy of Sciences of the United States of America, volume 113, pages 13570–13575, (2016):

Increasing wind turbine deployment uses an increasing share of the kinetic energy of the atmosphere, thus likely slowing down wind speeds. Climate models can explicitly simulate these effects (6–8) and yield a 10-fold reduction of the expected large-scale electricity generation rate from 3 to 5 We m−2 reported in studies using observed wind speeds (3–5, 9, 10) down to 0.3–0.5 We m−2 reported in climate model studies (6–8), with about 1.0 We m−2 possible in more windy regions like the US Midwest (6, 8, 11–13).

...

As shown in Table 1, there are numerous observation-based approaches that, by neglecting these atmospheric effects, drastically overestimate wind power limits by a factor of 10. Accounting for these atmospheric effects results in large-scale limits to wind power use in most land regions that are well below 1.0 W m−2

So, yes the OP is correct that large numbers of wind turbines decrease the kinetic energy of the wind available, but the OP reference is still overestimating with the 1.0 W m−2 figure. It is another factor of 2 or 3 lower according to this more-recent research.

The article also explains there is a peak, not in the sense of using up all the wind, but instead a point beyond which adding more turbines actually decreases the amount of electricity generated:

As would be expected, electricity generation first increases with greater installed capacity but then reaches a maximum rate of about 0.37 We m−2 on land (0.59 We m−2 over ocean) at an installed capacity of 24.3 MWi km−2 on land (9.1 MWi km−2 over ocean). Note that the generation rate does not “saturate,” as suggested by ref. 8, but rather generation reaches a maximum limit, beyond which electricity generation is reduced due to the further slowdown in wind speeds (6, 7, 13).

DavePhD
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  • Graphs! I'd upvote twice if there was a pretty graph for the last sentence – daniel Sep 28 '17 at 16:35
  • @daniel can you see the graphs here? http://www.pnas.org/content/113/48/13570/F1.expansion.html – DavePhD Sep 28 '17 at 16:51
  • @DavePhD yep, I'd say that top blue graph has a peak, it's some unobtainable giant theoretical value still. The wind power output curve from the other answer is more like my households "% of vegemite taken out of the jar vs time" – daniel Sep 28 '17 at 17:33
  • @Daniel 9MW per square kilometer. That means one Vestas V164 wind turbine per square kilometer. Certainly not unobtainable for a particular region. – DavePhD Sep 28 '17 at 17:37
  • If the world was virtualized as a total annihilation map it would take 1 commander over 999 years to build that many wind farms in the ocean, and you would have to reclaim more metal than there is on the map. (This is my way of saying I don't actually know if that many offshore wind farms could be built) – daniel Sep 28 '17 at 17:44