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Wind And Wave Energies Are Not Renewable After All

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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.

Interesting thesis.

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I've been saying similar for a while. If you try and harvest terrawatts of power from wind you will change the local & perhaps global wind patterns and case claim it changed

however claim it changed isn't necessarily bad and the consequences will probably be very minor.

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I've been saying similar for a while. If you try and harvest terrawatts of power from wind you will change the local & perhaps global wind patterns and case claim it changed

however claim it changed isn't necessarily bad and the consequences will probably be very minor.

Flowing around a wind farm is only the same as flowing around any other semi movable object.

Such as a tree.

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So we have solar energy raining in through the hole in the ozone layer causing the planet to heat up or whatever, and these windmills and whatnot removing energy so presumably cooling it down again. It all balances out nicely. Assuming we have the power. And these climate scientists are right of course. Good, one less thing to worry about.

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Flowing around a wind farm is only the same as flowing around any other semi movable object.

Such as a tree.

Yes & no.

Wind farms are typically much taller than trees so slow wind higher up. Plus a wind farm is placed in a certain way to slow as much wind as possible and placed in locations where the wind is generally faster too.

Plus importantly if you have a billion trees in a firestone very very few slow the wind. Just the ones on the edge and the swung wind will form pressures in a way that most the wind will just blue above the mass of trees.

However have 10 million wind turbines spread across half the world and you will impact wind patterns.

Tbh I don't think the consequences will be anything to worry about it nay even be positive.

The research is important in that it tells us what the maximum energy is you can get out of wind without reducing the effectiveness if wind farms

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Didn't we just spend a century and a half reducing energy loss from wind by chopping down a shit load of forests?

nuff said! :rolleyes:

Classic oneliner.....

Oh, your later comment.. A wind turbine extracts more energy than a (said group of..) trees from the wind, but not vastly more. And anyway there are a damn sight more trees we have cut down.

Wind turbines can never be anywhere near 100% efficient and have a maximum efficiency of around 40-50% (from memory) for a lift based device

Edited by voidal

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Then there's all those huge multi storey office blocks that the global warmists occupy in every town and city all over the world. They must be slowing the winds down an enormous amount. No wonder the weather's changing.

Edited by billybong

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Flowing around a wind farm is only the same as flowing around any other semi movable object.

Such as a tree.

I don't understand your point Injin.

Trees do not grow at the same elevations targeted by wind generators, nor do they exist at elevation in environments targeted by the power companies. Nor do trees exist in clusters of 100's at 100m+ elevations in the ocean. Fluid dynamics shows they do introduce turbulence into once independent systems, proof being that some wind farms have suffered catastrophic failures due to harmonics. The science of understanding this is still in it's infancy.

Wind is a finite resource, as is the tide, et al. That is the point of the article.

But yes, there are less trees and ground level gusts have surely grown in a lot of geographic areas.

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Wind turbines can never be anywhere near 100% efficient and have a maximum efficiency of around 40-50% (from memory) for a lift based device

And more importantly a minimum of 0%, which could happen to any number at any time.

I am no scientist, but this sounds like total rubbish to me.

Why? It's fairly obvious that it would happen sooner or later, the only room to quarrel over with it are the numbers. There is only so much energy in the wind, waves, and tides, and take enough of it out of them and you'll affect everything that's affected by wind, waves, and tides. Whether this guy is right in that that would start to happen with what we could theoretically build and need, or whether it would take vastly more than that to even become noticeable is the only space for argument.

Edited by Riedquat

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Interesting thesis.

This is mentioned in the book K-Pax. He claims it's no good "harvesting" the wind as once you have harvested it it will be used up, spent, exhausted, whatever. It sounds semi-plausible although if we could actually make that much impact on the forces of nature is anybody's guess.

K-Pax reminded me a little of Injin, BTW.

eight

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I too seriously doubt that extracting wave or wind energy is going to have the slightest impact. However, a good scientist puts up and idea and then spends his/her time trying to prove it wrong on the basis that if it survives the onslaught of many minds working on testing it, then it is reasonable to assume the idea is correct. This isn't what the so called scientists lobbying to support the man made climate change idea are doing with their tree ring data.

Some things about wind turbines.

You can only extract up to one third of the energy from the wind passing through the path of the blades.

You have to place them in a clear laminar flow of air or the blades do not 'fly' - they are like wings not Archimedes screws.

Placing them close to trees or on top of house or in gardens is simply not going to work. The reason is that nearby buildings and trees will cause turbulence and wings do not fly in turbulent air. Indeed your roof tiles are specifically designed to have a rough surface to cause local turbulence and are wavy to create a wider turbulence. Why? To stop the them flying off when it is windy. To demonstrate the above, I raised a commercial 1 metre turbine 4 metres clear of the garden. With the big old Ash tree and Lombardy Poplar bending and roaring in a 50mph gale I filmed the turbine blades stationary and the tail fin causing it to fitfully re-orientate itself.

Trees are very much better at absorbing the wind energy than a wind turbine since they can absorb energy from turbulent wind which would leave a turbine swinging around trying to 'face the wind' and the blades stationary. Some trees like the Aspen have a neat trick, the stalks of their leaves are aerofoil shaped causing the leaves to shiver in the slightest breeze.

There is no way we can build enough turbines to make up for the energy effects of the trees we have lost.

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Didn't we just spend a century and a half reducing energy loss from wind by chopping down a shit load of forests?
We need a "like" option...
Flowing around a wind farm is only the same as flowing around any other semi movable object. Such as a tree.
Correct.
Wind farms are typically much taller than trees so slow wind higher up. Plus a wind farm is placed in a certain way to slow as much wind as possible and placed in locations where the wind is generally faster too.
No they are placed where the wind is CONSISTANT. You don't want high speeds... in fact the wind turbines have to shut down in strong winds.
Plus importantly if you have a billion trees in a firestone very very few slow the wind. Just the ones on the edge and the swung wind will form pressures in a way that most the wind will just blue above the mass of trees.
You're statement would make sense if the trees were a solid block of concrete. They aren't
Oh, your later comment.. A wind turbine extracts more energy than a (said group of..) trees from the wind, but not vastly more. And anyway there are a damn sight more trees we have cut down.
Surface area/wind reisstance... a small clump of trees provides far more wind resistance than a wind turbine. Think of all those branches and leaves versus the surface area of a wind turbines blades.
Trees do not grow at the same elevations targeted by wind generators, nor do they exist at elevation in environments targeted by the power companies.
LOL... seriously? Trees grow at altitudes WAY above where we even COULD build wind farms if we want to. In fact I'd suggest that most of the worlds trees grow at heights above where you could put a wind farm, as weve caut down all the ones that are easy to get to to make way for farming etc. Wind farms may be on top of hills in the UK, but not the tallest hills, and our hills aren't very big.
Wind is a finite resource, as is the tide, et al. That is the point of the article.
Technically correct. The sun will eventually die, and the moon may leave orbit, ending the tides. We will look at this problem again in 6 billion years time.
I am no scientist, but this sounds like total rubbish to me.
It is.
And more importantly a minimum of 0%, which could happen to any number at any time.
You are confusing "output" and "efficiency". Technically, if wind drops to zero, efficiency reaches 100%!

----------------------------------------

Can everyone please get a grip and apply some high-school science please, you are all being silly. (Just out of interest, was the paper published on April 1st?)

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I'm not sure I can agree that wind is a finite resource - are a lot of global trade winds and circulations a result of the earths rotation?

He's also got a paper out saying we'd better stop catching the suns rays on beaches as it will burn out our resident star.

Anyone betting the only possible answer is more regulation/higher tax/global government?

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This is mentioned in the book K-Pax. He claims it's no good "harvesting" the wind as once you have harvested it it will be used up, spent, exhausted, whatever. It sounds semi-plausible although if we could actually make that much impact on the forces of nature is anybody's guess.

There is no wind energy, it's all solar.

That keeps shining so far as I can tell.

Edited by bogbrush

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I'm not sure I can agree that wind is a finite resource - aren't a lot of global trade winds and circulations a result of the earths rotation?

The opposite of finite is infinite.

I doubt it is genuinely infinite.

Obviously all this renewable energy will slow the earth's rotation until it eventually stops. :)

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Apparently you can't build wind farms too close together as the ones upwind drain the wind energy for the ones downwind.

Indeed. I've seen what happens when turbulence creates harmonics. This happened not too long ago, and the manufacturer got it in the neck, until a study concluded that they were installed with too little distance between them. These big turbines are designed to work at a relatively steady state, but when turbulence is introduced you create harmonics in the blades, and the one that was destroyed was done so by harmonics.

http://gazette.jhu.edu/2011/01/18/new-study-yields-better-turbine-spacing-for-large-wind-farms/

Reynolds Number demonstration: http://video.google.com/videoplay?docid=1827702182265329855#

Edited by cashinmattress

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The opposite of finite is infinite.

I doubt it is genuinely infinite.

Obviously all this renewable energy will slow the earth's rotation until it eventually stops. :)

At any one time, there is only so much wind on this planet.

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Where there's a will there's a way.

If wind's peaking and going to run out then maybe there should be a height tax tradeable between nations. We now have the technology through the CO2 offsetting etc. Get rid of some hills, mountains, multi storey buildings etc then you can have some wind turbines. If your country doesn't need turbines have some money selling the surplus.

Low lying countries like Holland could be tiger economies exporting surplus. People around the Himalayas are going to have to work on the problem. To coin an old phrase "you know it makes sense" and it does sound like the sort of thing the UK could be good at. Think job creation.

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Apparently you can't build wind farms too close together as the ones upwind drain the wind energy for the ones downwind.

That is correct. Even individual turbines within a farm impact each other hence why they are spaced and patterned in a certain way.

This guy is saying if you plan on running man's power needs off wind or solar you will likely change the environment and that is certainly true but the quantity if change vs power drawn us debatable.

For example let's say a hundred years from now the world built a giant 20 terra watt solar farm in the Sahara.

Well that is 20 terra watts if heat that would have been disputed in that location going elsewhere.

For an extreme example let's say all that power went to Iceland to heat homes & streets.

Well in effect man has moved 20 terra watts of heat from the Sahara to Iceland. Both areas will change but how much.

Likewise with wind. If you draw say 1 terra watt of wind from Mongolia to feed Beijing you are taking that heat from mongolia and placing it in Beijing. Again you will impact both places.

No one can disagree with this heat transfer because it is fact that can be proven. The only aspect you can disagree with is if a number around 20 to 50 terrawatts would impact the areas you are drawing and dumping that energy to. This guy is saying yes it would.

I too believe it is big enough number to impact the claim it.

To put it into perspective its like having a daylight laser beam the size of England drawing power from one area and dumping it on another

It certainly will impact the claim it (note. Not necessarily negatively just like more co2 may cause a change but not necessarily a bad change)

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If it was a closed system he would be quite right however the energy comes from the Sun as was pointed out in a previous comment.

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