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"Wind and wave energy are not renewable after all" watch

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    Build enough wind farms to replace fossil fuels and we could do as much damage to the climate as greenhouse global warming

    WITNESS a howling gale or an ocean storm, and it's hard to believe that humans could make a dent in the awesome natural forces that created them. Yet that is the provocative suggestion of one physicist who has done the sums.

    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.

    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.

    "It's hard to put a precise number on the fraction," he says, "but we certainly use more of the free energy than [is used by] all geological processes." In other words, we have a greater effect on Earth's energy balance than all the earthquakes, volcanoes and tectonic plate movements put together.

    Radical as his thesis sounds, it is being taken seriously. "Kleidon is at the forefront of a new wave of research, and the potential prize is huge," says Peter Cox, who studies climate system dynamics at the University of Exeter, UK. "A theory of the thermodynamics of the Earth system could help us understand the constraints on humankind's sustainable use of resources." Indeed, Kleidon's calculations have profound implications for attempts to transform our energy supply.

    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.

    "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 (Earth System Dynamics, DOI: 10.5194/esd-2-1-2011).

    "This is an intriguing point of view and potentially very important," says meteorologist Maarten Ambaum of the University of Reading, UK. "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."

    This by no means spells the end for renewable energy, however. Photosynthesis also generates free energy, but without producing waste heat. Increasing the fraction of the Earth covered by light-harvesting vegetation - for example, through projects aimed at "greening the deserts" - would mean more free energy would get stored. Photovoltaic solar cells can also increase the amount of free energy gathered from incoming radiation, though there are still major obstacles to doing this sustainably (see "Is solar electricity the answer?").

    In any event, says Kleidon, we are going to need to think about these fundamental principles much more clearly than we have in the past. "We have a hard time convincing engineers working on wind power that the ultimate limitation isn't how efficient an engine or wind farm is, but how much useful energy nature can generate." As Kleidon sees it, the idea that we can harvest unlimited amounts of renewable energy from our environment is as much of a fantasy as a perpetual motion machine.


    There was an article in NewScientist last week about a hypothesis that Wind and wave energy could be as damaging to our planet as fossil fuels. If you don't want to read through the full article (in Spoilers), then essentially the problems stems from applying the Laws of Thermodynamics to renewable energy generation. There is only a limited supply of "free energy" (energy which can be used to do work- work such as the movement of air to create winds) in our planet which gets replaced continuously by the Sun. If a lot of additional free energy is used up by Wind/Wave turbines and dissipated as waste heat (unusable energy), that could cause serious trouble to our planet's balance.

    What do you guys think of this? Is it just another hypothesis that will never go anywhere, or could this mean some serious problems for the renewable energy industry?
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    Very interesting stuff. I had always thought of wind and wave energy as limitless.....
    The future is nuclear and solar!!
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    I accept this theory. Back to the nuclear band wagon we go!
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    It's a very interesting theory, although one I don't really understand :erm:
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    (Original post by Student2806)
    It's a very interesting theory, although one I don't really understand :erm:
    I really struggled to understand it too. This hypothesis is based on lots of calculations (and perhaps climate modelling), so it's pretty hard to understand conceptually.

    Here's my attempt to grasp it. Thermodynamic free energy is basically the energy that you can use to do "work"- work is a mechanical process such as the movement of air in winds. The petrol in a car engine is high in free energy, because it can do work and propel the car. The waste heat that your car dissipates from burning petrol on the other hand is low in free energy, as you cannot use this waste heat to propel a car. Free energy is NOT conserved. The Earth has a certain amount of free energy because the Sun heats the Earth unequally, causing differences in air pressure on the Earth. Since a system always tries to equalise pressure, this causes winds (and by extension waves) to be produced.

    When the wind blows normally, work is being done, which results in a loss of free energy. Now this is fine normally, because the Sun will continue to heat up the Earth unequally and replaces the free energy of the Earth. However, if you do try to extract further work by having the wind generate electricity in wind turbines, that reduces the free energy in the system, so there is less available energy for the Earth to do work and produce winds.

    Essentially, the presence of too many wind turbines means we drain free energy from the winds at a rate faster than this free energy is replenished by the Sun. Hence the headline of the article that wind energy might not be so renewable after all.
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    (Original post by innerhollow)
    I really struggled to understand it too. This hypothesis is based on lots of calculations (and perhaps climate modelling), so it's pretty hard to understand conceptually.

    Here's my attempt to grasp it. Thermodynamic free energy is basically the energy that you can use to do "work"- work is a mechanical process such as the movement of air in winds. The petrol in a car engine is high in free energy, because it can do work and propel the car. The waste heat that your car dissipates from burning petrol on the other hand is low in free energy, as you cannot use this waste heat to propel a car. Free energy is NOT conserved. The Earth has a certain amount of free energy because the Sun heats the Earth unequally, causing differences in air pressure on the Earth. Since a system always tries to equalise pressure, this causes winds (and by extension waves) to be produced.

    When the wind blows normally, work is being done, which results in a loss of free energy. Now this is fine normally, because the Sun will continue to heat up the Earth unequally and replaces the free energy of the Earth. However, if you do try to extract further work by having the wind generate electricity in wind turbines, that reduces the free energy in the system, so there is less available energy for the Earth to do work and produce winds.

    Essentially, the presence of too many wind turbines means we drain free energy from the winds at a rate faster than this free energy is replenished by the Sun. Hence the headline of the article that wind energy might not be so renewable after all.
    Does that mean hypothetically we could stop all wind and waves by using up all free energy in the Earth energy system?:eek:
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    (Original post by therealOG)
    Does that mean hypothetically we could stop all wind and waves by using up all free energy in the Earth energy system?:eek:
    Well wind/wave turbines aren't 100% efficient so no you couldn't stop wind/waves altogether. However, according to this article, wind/wave energy could cause long-term decreases in wind/wave speed (causing far less electricity than expected to be produced) and various climate instabilities.
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    "Wind and wave energy are not renewable after all"...so are they variably renewable or semi-renewable?
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    Well at least my question of how winds and waves are produced have been answered thanks hollow it kept bothering me ^__^.
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    That's the green party stuffed.
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    Why don't Christians, Muslims etc. simply pray for energy ?
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    I've always wondered about this. Surely any method of generating usable energy will have some impact on the environment because it's got to be taken from somewhere. I don't think there is such thing as perfectly "green" energy. Anything we do is going to use up some natural resources.
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    (Original post by CoolDude)
    "Wind and wave energy are not renewable after all"...so are they variably renewable or semi-renewable?
    Think of Wind/Wave energy as a bucket.
    We can take some water out of the bucket and it will be continually refilled and so there will be no real affect on the system (the bucket).

    However if we start taking water out of the bucket at a massive rate then the natural refilling of the bucket will not be able to keep up, and there will be a macroscopic change on the system.

    It is renewable in that it will always (ignoring what's going to happen in a few billion years time) be renewed, but if we take too much of the energy then it will have massive effects on our planet, which obviously doesn't sound too good.


    I would be interested if they have made similar studies into the effects of Nuclear Fusion power.
    For those who don't know, fusion would basically be infinite in that a tiny about of Hydrogen (which we can make as much as we like of) will produce, using the technical term, a **** load of energy.
    That said, if we want 20-30TW of electrical power, that means producing 100-150TW of heat energy from fusion. This is heat that would otherwise never be released into the system (fusion does not occur naturally on Earth), and would normally remain safely tied up as mass.
    So, what is the effect of producing an extra 100-150TW of heat in our system? Is that enough to change our planet as a whole?
    I bloody hope someone has asked this question high up, because clearly they didn't think through Wind power that thoroughly.

    As a side note, Fission is definitely not the way forward in the long term because, contrary to popular belief, there is not actually that much fissionable material out there. Less than 100 years of Uranium at current consumption (which is set to sky-rocket), although I don't know how much of the other materials we could use we have left.
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    (Original post by Fallen)
    Think of Wind/Wave energy as a bucket.
    We can take some water out of the bucket and it will be continually refilled and so there will be no real affect on the system (the bucket).

    However if we start taking water out of the bucket at a massive rate then the natural refilling of the bucket will not be able to keep up, and there will be a macroscopic change on the system.

    It is renewable in that it will always (ignoring what's going to happen in a few billion years time) be renewed, but if we take too much of the energy then it will have massive effects on our planet, which obviously doesn't sound too good.


    I would be interested if they have made similar studies into the effects of Nuclear Fusion power.
    For those who don't know, fusion would basically be infinite in that a tiny about of Hydrogen (which we can make as much as we like of) will produce, using the technical term, a **** load of energy.
    That said, if we want 20-30TW of electrical power, that means producing 100-150TW of heat energy from fusion. This is heat that would otherwise never be released into the system (fusion does not occur naturally on Earth), and would normally remain safely tied up as mass.
    So, what is the effect of producing an extra 100-150TW of heat in our system? Is that enough to change our planet as a whole?
    I bloody hope someone has asked this question high up, because clearly they didn't think through Wind power that thoroughly.

    As a side note, Fission is definitely not the way forward in the long term because, contrary to popular belief, there is not actually that much fissionable material out there. Less than 100 years of Uranium at current consumption (which is set to sky-rocket), although I don't know how much of the other materials we could use we have left.
    You're not taking into account resource exploration. 80 years reserves is our assured uranium supply at present, that number will rise as countries start looking for more uranium! Moreover, improvements in nuclear energy technology further increase our fission economy, such as breeder reactors to reprocess spent fuel, and new lines of reactors which can use different fuels (i.e. thorium fission reactors).

    I don't think fission is a long-term solution to be fair, because it's still non-renewable, but certainly until we are able to implement a long-term feasible renewable energy solution (which we don't really have at the moment), we are rather stuck for options. And as countries like France have demonstrated, switching a large proportion of your energy production to nuclear in a short space of time is manageable.

    The waste heat from Fusion would cause Climate Warming, yes.
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    (Original post by innerhollow)
    You're not taking into account resource exploration. 80 years reserves is our assured uranium supply at present, that number will rise as countries start looking for more uranium! Moreover, improvements in nuclear energy technology further increase our fission economy, such as breeder reactors to reprocess spent fuel, and new lines of reactors which can use different fuels (i.e. thorium fission reactors).

    I don't think fission is a long-term solution to be fair, because it's still non-renewable, but certainly until we are able to implement a long-term feasible renewable energy solutio (which we don't really have at the moment), we are rather stuck for options.

    The waste heat from Fusion would cause Climate Warming, yes.
    It is very, very dangerous to start building dozens of multi-billion pound Fission reactors in the [I]hope[\I] that our (generally fairly good) estimates are wrong.
    You must also factor in the cost of establishing Uranium supply-lines, pre- and post- fission processing plants, and long term waste storage facilities.
    All in all there is a lot of expense which may be worth it, but we'd better be pretty dam'n sure before we place trillions or pounds and our energy security in it.

    True, other fuels are also viable, but as I suspect you are aware the processes involved in, say, a thorium reactor are completely different, and large parts of a Uranium power station would be left both redundant and require substantial modification and replacement to convert it.
    In addition, Uranium power stations have very specific requirements for their waste processing plants, which would be rendered useless even if we converted all old Uranium power stations to other fuels after the Uranium is depleted.

    Yes, it would cause Climate Change, but do you or anyone else have any idea how much ~100TW is? It is evidently a lot, but the Earth could be radiating it away with ease. I don't know...
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    (Original post by Fallen)
    It is very, very dangerous to start building dozens of multi-billion pound Fission reactors in the [I]hope[\I] that our (generally fairly good) estimates are wrong.
    You must also factor in the cost of establishing Uranium supply-lines, pre- and post- fission processing plants, and long term waste storage facilities.
    All in all there is a lot of expense which may be worth it, but we'd better be pretty dam'n sure before we place trillions or pounds and our energy security in it.

    True, other fuels are also viable, but as I suspect you are aware the processes involved in, say, a thorium reactor are completely different, and large parts of a Uranium power station would be left both redundant and require substantial modification and replacement to convert it.
    In addition, Uranium power stations have very specific requirements for their waste processing plants, which would be rendered useless even if we converted all old Uranium power stations to other fuels after the Uranium is depleted.

    Yes, it would cause Climate Change, but do you or anyone else have any idea how much ~100TW is? It is evidently a lot, but the Earth could be radiating it away with ease. I don't know...
    It's pointless to outline the problems associated with fission on an individual basis. Any global energy solution will be horrificially expensive and have a multitude of associated problems. No one said that fission is problem-free, just that it's preferable to the possible alternatives- it's the least of many evils.

    Also, assured reserves are completely different to total reserves. Assured reserves are NOT an estimate or a prediction. You're also forgetting that depleted Uranium is still a possible fuel.
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    (Original post by innerhollow)
    It's pointless to outline the problems associated with fission on an individual basis. Any global energy solution will be horrificially expensive and have a multitude of associated problems. No one said that fission is problem-free, just that it's preferable to the possible alternatives- it's the least of many evils.

    Also, assured reserves are completely different to total reserves. Assured reserves are NOT an estimate or a prediction. You're also forgetting that depleted Uranium is still a possible fuel.
    Oh, I didn't realise it was 80 years of assured reserves, yes I know the difference.

    Even so. I mean, I am all for Uranium fission, but I certainly don't think rolling out many dozens of new stations globally is going to help anyone.
    Saying there isn't any point of listing the problems with Uranium isn't really true. I never said other sources were perfect, Christ no, but that doesn't mean that some solutions are better than others.

    I don't suggest we do away with Uranium power, I don't even suggest we reduce our current usage. I just disagree with the opinion that Uranium 'is the answer' to all our fossil fuel based problems - because such an opinion (and I am not saying it is your opinion) is very short-sighted indeed.

    Uranium plays and will play an increasing important role, but I would much prefer building more tidal barrages (like the one the last government decided to scrap plans for to 'save the wetlands' - Ignoring what's going to happen when we strip-mine for coal, uranium, and tar sands), some wind, some solar (although perhaps not in the U.K).
    Saying 'Oh lets have a selection' really does sound idealistic, but then again there is no real reason why we shouldn't.
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    "Green" industry lobby: "QUICK, SILENCE THIS REPORT IMMEDIATELY!!"

    It's true. Expect not to hear any more of it for 20 years.
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    (Original post by Liquidus Zeromus)
    "Green" industry lobby: "QUICK, SILENCE THIS REPORT IMMEDIATELY!!"

    It's true. Expect not to hear any more of it for 20 years.
    Indeed, but what will be annoying now is politicians will still be committed to green technology and say they are doing so on the basis of science. But when said science doesn't support that view, they just ignore it or discredit the report.

    It's a disgusting way to go about the energy provision of our country.
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    (Original post by Fallen)
    Oh, I didn't realise it was 80 years of assured reserves, yes I know the difference.

    Even so. I mean, I am all for Uranium fission, but I certainly don't think rolling out many dozens of new stations globally is going to help anyone.
    Saying there isn't any point of listing the problems with Uranium isn't really true. I never said other sources were perfect, Christ no, but that doesn't mean that some solutions are better than others.

    I don't suggest we do away with Uranium power, I don't even suggest we reduce our current usage. I just disagree with the opinion that Uranium 'is the answer' to all our fossil fuel based problems - because such an opinion (and I am not saying it is your opinion) is very short-sighted indeed.

    Uranium plays and will play an increasing important role, but I would much prefer building more tidal barrages (like the one the last government decided to scrap plans for to 'save the wetlands' - Ignoring what's going to happen when we strip-mine for coal, uranium, and tar sands), some wind, some solar (although perhaps not in the U.K).
    Saying 'Oh lets have a selection' really does sound idealistic, but then again there is no real reason why we shouldn't.
    No I concur. Relying 100% on one energy source is never the answer. Fission will inevitably play a huge part in our energy future, as will renewables and possibly CCS-equipped fossil fuels. However, at the moment if we want to severely reduce our fossil fuel intake, the only one of these that can be expanded in a reasonable timeframe is fission. Neither renewables nor CCS can be implemented on a large enough scale at present. That's why people view it as the "answer". I don't think anyone's said we shouldn't keep investing in renewables.
 
 
 
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