Is "peak wind" coming?

Question

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?

Answer 1

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.

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"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.

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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.

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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.

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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.

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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.

Answer 2

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 W_e m⁻² reported in studies using observed wind speeds (3–5, 9, 10) down to 0.3–0.5 W_e m⁻² reported in climate model studies (6–8), with about 1.0 W_e m⁻² possible in more windy regions like the US Midwest (6, 8, 11–13).

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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 W_e m⁻² on land (0.59 W_e m⁻² over ocean) at an installed capacity of 24.3 MW_i km⁻² on land (9.1 MW_i 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).