Wind power and wave energy are not renewable after all
Build enough wind farms to replace fossil fuels and we could do as much damage to the climate as greenhouse global warming
Rubbish. Indeed, what is surprising about this entire piece is just how much misinformation it contains. You can read the original, unsexy, somewhat opaque (and probably wrong) paper submitted to Philosophical Transactions of the Royal Society.
Even if it were true that increasing global wind power capacity 300-fold (!) would do as much damage to the climate as greenhouse warming — and there’s no evidence in this study that it would — wind turbines and wave power would still be renewable. As NASA’s Gavin Schmidt wrote me (see below), “The NS headline is wrong.”
I’ve been bombarded with people asking me to respond to this in detail, so here goes.
New Scientist explains the work of Axel Kleidon of the Max Planck Institute for Biogeochemistry this way:
He concludes that it is a mistake to assume that energy sources like wind and waves are truly renewable. Build enough wind farms to replace fossil fuels, he says, and we could seriously deplete the energy available in the atmosphere, with consequences as dire as severe climate change.
In fact, New Scientist has misrepresented Kleidon’s research. He coauthored a new open access paper in Earth System Dynamics, “Estimating maximum global land surface wind power extractability and associated climatic consequences,” which has been severely critiqued by multiple sources, including folks like Stanford’s Mark Jacobson (here and below), whom I trust a great deal.
UPDATE: Stanford’s Mark Jacobson has emailed me a comment on the paper, which I reprint at the end.
That study finds a maximum extractable amount of wind in the range of 18–68 TW and states “we show with the general circulation model simulations that some climatic effects at maximum wind power extraction are similar in magnitude to those associated with a doubling of atmospheric CO2.”
So Kleidon wrote “some” effects at 68TW might be “similar in magnitude” to 550 ppm — whereas NS says it would have “consequences as dire as severe climate change.” No, I don’t think wind turbines will cause a mass marine extinction or endless sea level rise.
As an aside, I just wish people who write this kind of stuff based on one paper which may or may not be true (that in any case they don’t understand) would actually read the dozens of scientific papers that explain how dire severe climate change is. Heck, they could even read multiple papers in the journal they are citing: Royal Society special issue details ‘hellish vision’ of 7°F (4°C) world — which we may face in the 2060s!
Back to the story:
Axel Kleidon of the Max Planck Institute for Biogeochemistry in Jena, Germany, says that efforts to satisfy a large proportion of our energy needs from the wind and waves will sap a significant proportion of the usable energy available from the sun. In effect, he says, we will be depleting green energy sources. His logic rests on the laws of thermodynamics, which point inescapably to the fact that only a fraction of the solar energy reaching Earth can be exploited to generate energy we can use.
When energy from the sun reaches our atmosphere, some of it drives the winds and ocean currents, and evaporates water from the ground, raising it high into the air. Much of the rest is dissipated as heat, which we cannot harness.
At present, humans use only about 1 part in 10,000 of the total energy that comes to Earth from the sun. But this ratio is misleading, Kleidon says. Instead, we should be looking at how much useful energy – called “free” energy in the parlance of thermodynamics – is available from the global system, and our impact on that.
Humans currently use energy at the rate of 47 terawatts (TW) or trillions of watts, mostly by burning fossil fuels and harvesting farmed plants, Kleidon calculates in a paper to be published in Philosophical Transactions of the Royal Society. This corresponds to roughly 5 to 10 per cent of the free energy generated by the global system.
Of the 47 TW of energy that we use, about 17 TW comes from burning fossil fuels. So to replace this, we would need to build enough sustainable energy installations to generate at least 17 TW. And because no technology can ever be perfectly efficient, some of the free energy harnessed by wind and wave generators will be lost as heat. So by setting up wind and wave farms, we convert part of the sun’s useful energy into unusable heat.
For the record, we are currently at some 0.2 TW of wind up from 0.1 TW about three years ago.
“Large-scale exploitation of wind energy will inevitably leave an imprint in the atmosphere,” says Kleidon. “Because we use so much free energy, and more every year, we’ll deplete the reservoir of energy.” He says this would probably show up first in wind farms themselves, where the gains expected from massive facilities just won’t pan out as the energy of the Earth system is depleted.
Using a model of global circulation, Kleidon found that the amount of energy which we can expect to harness from the wind is reduced by a factor of 100 if you take into account the depletion of free energy by wind farms. It remains theoretically possible to extract up to 70 TW globally, but doing so would have serious consequences.
Although the winds will not die, sucking that much energy out of the atmosphere in Kleidon’s model changed precipitation, turbulence and the amount of solar radiation reaching the Earth’s surface. The magnitude of the changes was comparable to the changes to the climate caused by doubling atmospheric concentrations of carbon dioxide [550 ppm].
Where to begin? First, as Schmidt wrote me:
However we extract energy from the ‘active’ system (i.e. not fossil energy), it will affect energy flows in the active system. The more we take, the larger the effect.
Regardless of the size of the impact, it is always renewable. The NS headline is wrong.
We are nowhere near the point at which energy extraction from the active system is a significant player in climate change. It might become so in the far future, but any forseeable growth is well below
In short, the “not renewable claim” is just wrong. It’s a sexed up but dead wrong headline to grab eyeballs.
Heck, our sun will die in about 5 billion years, so I guess solar energy isn’t renewable either.
Second, if by some staggering political conversion and then WWII-scale effort we actually adopted the strategy I have proposed for stabilizing at or below 450 ppm, a strategy that is quite similar to the one proposed by the International Energy Agency, we’d be using “only” 4 TW of wind by 2050.
There is no evidence whatsoever that this would cause any significant harmful global impacts, let alone ones that are even close to the multiple catastrophes that await us if we double CO2 concentrations, which by itself would almost certainly start us down a path of amplifying carbon-cycle feedbacks that would take us to a tripling or quadrupling (see NSIDC bombshell: Thawing permafrost feedback will turn Arctic from carbon sink to source in the 2020s, releasing 100 billion tons of carbon by 2100).
Third, the Miller, Gans, and Kleidon (MGK10) wind paper has been widely criticized by other leading experts. Here is the summary of the 7-page critique by Stanford’s Jacobson with Cristina L. Archer of Cal State:
We believe the wind power resources from MGK10, estimated as 17]38 TW over land, are low by a factor of up to four due to the unphysical nature of MGK10’s calculations and the fact that such calculations are not comparable with data]derived wind resources. Further, even if MGK10’s wind resources were correct and their scenario realistic, the climate consequences stated by the authors are overestimated by a factor of at least 50]100. In addition, when their scenario is put in a realistic context whereby wind energy replaces thermal power plants, the effects of wind turbines can only be no net change or a reduction in internal energy added to the atmosphere and a significant reduction in other forcings due to the elimination of greenhouse gases (GHGs) and black carbon (BC) from such power plants.
Another expert commenter concludes (here):
Energetically relevant wake-produced turbulence (not flow-variability) is an assertion and not yet proved by real-world measurements, which indicate rather the opposite. Therefore, energy-replenishment at turbine level is still an unsolved issue. Atmospheric-dynamics processes of energy-replenishment and of resource reduction are still widely unconsidered, but seem to be most relevant. Basic atmospheric dynamics is not correctly applied in the article, so that the model results are questionable.
But you’d never know of these critiques by reading NS. They not only misreported the study and ignored the severe critics, but instead write, “Radical as his thesis sounds, it is being taken seriously.” And then they quote two people who endorses Kleidon’s approach.
And as if this isn’t enough, they write an editorial too, based on their misreporting of this one, very questionable study, “The sun is our only truly renewable energy source.”
Finally, in a box titled, “Is solar electricity the answer?” New Scientist writes “A solar energy industry large enough to make a real impact will require cheap and efficient solar cells.” Apparently the authors have never heard about concentrated solar thermal electricity. Worse, the box ends with this whopper:
Even if solar cells like this are eventually built and put to work, they will still contribute to global warming. That is because they convert only a small fraction of the light that hits them, and absorb most of the rest, converting it to heat that spills into the environment. Sustainable solar energy may therefore require cells that reflect the light they cannot use.
No, no, 100,ooo times no.
We went through this with the authors of the error-riddled book Superfreakonomics and the very confused ‘genius’ who has so impressed Bill Gates, Nathan Myrhvold. The Superfreaks quoted Myrhvold:
“The problem with solar cells is that they’re black, because they are designed to absorb light from the sun. But only about 12% gets turned into electricity, and the rest is reradiated as heat — which contributed to global warming.”
At one obvious level, New Scientist and Myrhvold wrong because the issue is not how much sunlight PV panels absorb but how much they absorb compared to the material that the panel covered up. Lots of solar panels sit on black roofs.
But the far bigger error is that the solar electricity eliminates the emission of CO2 which would otherwise occur from electricity production, which reduces planetary warming by several orders of magnitude compared to the re-radiated heat (see Why solar energy trumps coal power: Exclusive new Caldeira analysis explains “the burning of organic carbon warms the Earth about 100,000 times more from climate effects than it does through the release of chemical energy in combustion”).
I realize that because solar and wind power are growing by leaps and bounds that the media feels obliged to play the contrarian, but this piece is ridiculous.
This New Scientist article rivals Charlie Sheen for being incoherent and incorrect.
UPDATE: Stanford’s Mark Jacobson emails me this comment:
This study provides inaccurate and misleading information about wind energy and its physical interactions with the atmosphere for the following reasons.
First, it states that the amount of power in the wind available for wind energy is 18-68 TW and that the climate effects of extracting all such power is equivalent to doubling carbon dioxide. However, wind power results in no net additional heat to the air since it replaces thermal power plants (coal, nuclear, natural gas), all of which directly add the same or more heat to the air than wind power directly through combustion or radioactive decay. These other sources also add carbon dioxide, which wind energy does not do during its operation. Even nuclear adds carbon dioxide continuously through uranium mining, transport, and refinement and, in its lifecycle, puts out 9-25 more carbon dioxide than wind.
Second, even if wind turbines did not replace thermal power plants, the actual heat resulting from converting 18-68 TW of wind power to electricity, which then gets converted to heat is 0.035]0.13 W/m^2. The radiative heating due to doubling of CO2 is 3.7 W/m2, a factor of 28-106 higher. As such, even if 18-68 TW of the wind’s power were extracted, it would affect temperatures by 28-106 times less than doubling carbon dioxide, not the same amount. However, as stated, wind displaces thermal power plants, so its net heat added to the atmosphere is zero.
Third, the world end-use power demand today is 12.5 TW. By 2030, this is expected to grow to 17.9 TW. Converting the world to clean energy and electricity reduces the world power demand in 2030 by 30% to 11.5 TW due to the efficiency of electricity versus thermal combustion. At most, half of this would be powered by wind, resulting in 5.5 TW required, not 18-68 TW. Thus, even if wind power added heat to the air, powering 50% of the world with wind would results in only 1/346th the heating due to doubling carbon dioxide. Again, though, wind adds no heat since it displaces thermal power plants, which directly heat the air the same or more than wind while increasing carbon dioxide and other pollutants.
Fourth, a portion of the heat generated by wind energy is converted back to potential and kinetic energy, so not all of it goes to heat. This was not accounted for by the authors.
Finally, the authors’ wind resource analysis is not based on physical principles or realistic calculations. It is based on simplistic calculations that are extrapolated over the world and unverified against observations. They significantly underestimate the resources.
By Joe Romm, climateprogress.org/