Not enough wind to go around

Kleidon: send climate science back to the drawing-board

Off-gridders love wind-power because it’s free, infinitely renewable and doesn’t damage the environment.


Er, wrong on all counts, says a new report by German scientists which challenges virtually all our assumptions about wind-power as a sustainable energy source, and questions wave-power for good measure.

According to the study carried out by the respected Max Planck Institute for Bio-geochemistry in Jena, Germany, wind and wave energies are not infinitely renewable after all. They can be ‘used up’ if there are too many turbines built.

Worse, says the study, the climate effects of using too much wind and wave energy could be comparable to doubling atmospheric concentrations of carbon dioxide. So the environmental costs could be enormous.

The conclusions may sound nonsensical but they are based on the concept of ‘free’ or usable energy, says academic Axel Kleidon who led the research. “Although the earth receives an enormous amount of energy from the sun, 99 per cent of it is reflected back into space. Only the remaining one per cent is usable by wind and wave power.”

He says the earth receives 100,000 terawatts of energy from the sun. Of this 99% is reflected back into space, leaving just 1,000 tw of ‘free’ energy. Of this, three quarters is unusable because it is over oceans, leaving 250 tw. At best you can be 50% efficient in energy conversion so this leaves maybe 120tw of ‘free’ energy.

He says that currently human beings use nearly 50tw of energy, nearly 20tw of it in fossil fuels and close on 30 in food production. This total is predicted to rise to 80tw by the end of the century –a level that is beginning to approach the limits of what is available.

The impact wont be immediate says Kleidon and still leaves room for wind as a transitional source of power. But in the long run it is unsustainable he says: “We have to understand that human beings play a substantial role in planetary energy usage and that role is getting bigger.”

” We need to understand that the human race is a real factor in the use of planetary energy. Human beings certainly use more of the free energy than all geological processes put together. More than all the earthquakes, volcanoes and tectonic plate movements put together.”

Although the winds will not die altogether, taking that much energy out of the atmosphere in the long run could result in substantial climate change. “The first signs will be an impact on local wind patterns affecting the efficiency of wind farms. The result of reduced energy in the atmosphere could also be changes in precipitation, turbulence and the amount of solar radiation reaching the Earth’s surface.”

Kleidon’s findings may sound outlandish and even alarmist, but they are being taken seriously by the scientific community. “While I might quibble with the details, there is a crucial message here for mankind. He is saying that there is a finite amount of free energy.  It shows that there is no such thing as a free lunch. You don’t get something for nothing in the physical world. Kleidon’s calculations have  implications for attempts to transform our energy supply,” says Peter Cox, Professor of Climate Studies at Exeter University

His view is supported by meteorologist Maarten Ambaum of the University of Reading, UK. “This is an intriguing point of view and potentially very important. Human consumption of energy is substantial when compared to free energy production in the Earth system. If we don’t think in terms of free energy, we may be a bit misled by the potential for using natural energy resources,” he told the UK’s New Scientist magazine

The implication of the study is that in the long run only solar power will be able to fulfil mankind’s energy needs without serious climatic damage, says Kleidon. He said that the Max Planck Institute is funded exclusively by the German government. “We receive no help from solar, nuclear, oil or conventional  electricity companies. This study has no commercial agenda.”

7 Responses

  1. On wind and the climate:
    The medium temperature of the world is increasing, however poles temperature is still regulated by the ice melting temperature, so the global thermodynamic engine is speeding up, producing stronger winds than ever on the surface.
    On wind turbine effect:
    Wind turbines might slow down winds, but trees also have a slow down effect on winds.
    How many trees are cut when one wind turbine is built ?
    Something is missing in that article.

  2. There are many very serious flaws in this study. A number of experts have already pointed out some of those flaws here:

    I’ll add a few more:
    1. On the wind resource estimates: The study’s wind resource estimate is based on a series of very questionable calculations. They take the raw wind production, 45,000 TW, and then whittle away 99.9% of that resource based on very questionable assumptions to get 18-68 TW of available energy. First, they use a very weakly supported and obsolete 1979 estimate to assume 98% of that energy is lost to friction. Even if that number were correct, in a world with a lot more wind turbines a lot more of that energy could be captured before it was lost to friction. Next, they throw away another 50% of the remaining energy due to assumed friction that seems to be redundant with what was thrown away in the previous step. Finally, they throw away 75% of the remainder on the assumption that wind produced over the ocean and over glaciated land cannot be used. Even without offshore wind deployment that assumption would be flawed, as wind energy over the ocean interacts with air masses over land and generates wind there. They even note that that is a flaw in their paper. So even if just one of those exclusions is slightly too high, and several appear to be, the wind resource estimate would be orders of magnitude higher. That would put it in line with many of the other wind resource estimates out there, namely Dr. Jacobsen’s work at Stanford.

    2. On wind and the climate: First, it is a very misleading to say that adding a massive amount of wind is “comparable” to doubling CO2, as the only metric on which they found climate change that was comparable to doubling CO2 was for changes in precipitation, not temperature. All of their model runs indicate a 100-fold increase in wind energy production would cause zero change in surface temperatures. A 1000-fold increase wind energy output does cause a small, 1 degree C increase in surface temperature, but that is not a real climate forcing, but rather just a localized movement of energy from the upper atmosphere down to the surface as the turbine catches less dense higher level air and it releases heat as it adiabatically expands. Again, no energy is being produced from that, and the earth’s energy balance is not being changed nor the climate forced; this is just a localized phenomenon downwind of a turbine that should normalize as the atmosphere mixes. More importantly, it only occurs at wind penetrations 1,000 times higher than we have today. Back to precipitation: While their model does show a few mm/day change in precipitation as one gets to wind penetrations several hundred times higher than today, this appears to be a sum of absolute value amounts and thus ignores that these effects are going to be both positive and negative in different places and at different times, meaning they will mostly net each other out. Second, most climate models are very bad at predicting changes in precipitation, and in fact, the two models they used disagree strongly on the impact. So the precipitation impact isn’t anything credible anyway.

    To sum up these flaws, which are in addition to the ones pointed out by others:

    On the wind resource estimate:
    – It is a very conservative estimate.
    – If more realistic assumptions had been used in several places, the estimated wind resource would have been dozens of times higher, which would put it in line with other estimates produced by researchers at Stanford University and at the U.S. Department of Energy, which calculated that there is enough wind energy to meet humanity’s energy needs dozens or even hundreds of times over.
    – Even if the very conservative assumptions are correct, there would be more than enough wind energy to entirely displace humanity’s current use of fossil fuels.
    – Wind energy is renewable, and always will be for as long as the sun continues to shine.

    On the wind-climate issue:
    – The study found humanity’s use of wind energy could increase hundreds of times over without having any impact at all on temperatures.
    – Even at unrealistically high wind penetrations 1,000 times greater than we have today, which would produce dozens of times more energy than is used by humans today in total, the only impact on temperature would be to move some energy around in the atmosphere so that temperatures at the earth’s surface appeared slightly higher than they are today, but that impact would dissipate immediately as the earth’s atmosphere mixes.
    – The study found that increasing our use of wind energy a hundred or more times over would also have no impact on precipitation or other aspects of the climate. Only at extremely high penetrations approaching 1000 times more wind energy than we have today were the authors able to estimate that there would be small, localized, and likely temporary changes in precipitation, and even then their models were uncertain about that conclusion.

    Michael Goggin
    American Wind Energy Association

  3. Get Tesla back and he’d have that energy tapped for you by 6 PM.

    Of course you’d have to break the bad news to the energy monopolies that their cash cow just died. Might wanna duck the passing bullets at that point. Good luck.

  4. Fundamentally, this is right. There is no such thing as a free lunch, but I have some questions about the numbers. First, how can we simply dismiss the energy that falls on the oceans as “unavailable”? Sure, we don’t typically build there, but the sun’s thermal impact on the seas contributes to the temperature and pressure gradients that are ultimately the source of wind. Those winds blow ashore; just look at how far inland seaborn hurricanes can travel. If we capture those winds, are we not then capturing some of the solar energy that these theorists dismissed as “unavailable”?

    Next, fossil fuel energy is not a debit against today’s free solar energy. Fossil fuels represent accumulations of solar energy in past eras. So how does the use of those fuels reduce the amount of energy that is available in today’s solar flux? Finally, I will simply repeat a variation of the same question for nuclear power. How would the use of nuclear power subtract from the energy that is available in the solar flux? I suppose the answer to these questions must be that they were calculating the percentage of the free energy that must be captured from the sun through a variety of renewable sources if we planned to displace all current fossil and nuclear sources with solar and renewables. Interesting point.

    Given that they incorrectly (in my opinion) discounted the energy impacting the oceans as “unavailable”, I would say that their estimates err on the conservative side. On the other hand, it is still true that the free energy is finite, and we would have to tap a very high percentage of it to replace all of our other sources of energy.

  5. well, how do we stop some of that 99 percent of solar energy from being reflected away?
    Doesn’t the planet Venus have a high albedo, meaning it reflects lots of sunlight, but probes have learned that it’s hellishly warm on the planet’s surface?
    I have heard that an efficient windmill will leave an area of calmness downstream of the vanes… but hey now, remember that the atmosphere is several miles thick and the winds aloft are quite mighty. I think even if every single household in the world had their own wind-powered generator, they would only be capturing a tiny percentage of possible wind energy.
    Worrying about too many windmills is as dumb as worrying about the sun going out or the proton death of the universe.

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