Hi All, Last year I read a short comment by Dr. Caldera on "High Wind"
energy harvesting posted on Bill Gates website
http://www.thegatesnotes.com/Conversations/What-About-Wind. Dr. Caldera
stated "if we were to meet future power demand by this source exclusively,
we must intercept more than 1% of natural flows. I think when we get above
a 1% change in a natural system, we need to be concerned about large scale
unintended consequences.". And, now I see this report by Dr. Kleidon
reporting concerns about Boundary Layer Winds and Wave Energy. I am
somewhat disappointed that such exotic extrapolations are getting serious
play on the issue of renewable energy.
First, I believe Dr. Gaskill statement in this tread is the the clearest
thinking on this issue of the use of these renewable energies. This planet
is in fact solar powered and the solar energy that it receives is far more
than we can use. Also, Boundary Layer winds are effected by the difference
between the rotational speed of the planet and that of the total (fluid)
mass of the atmosphere. High altitude winds also get impacted by this
differential to a certain degree. Wave energy has not just the solar energy
input, but, the added lunar diurnal gravitational influence.
I am not an expert in any shape or form, but, I have twirled a coffee cup
and watched how the "boundary friction" between the cup and fluid causes
the fluid to move. And, I have stood by the shore and watched the force of
a tide rise and fall and watched the wave production from that force. On a
global scale, these basic physical forces are clearly significant enough to
be considered into the equation. Looking beyond just the solar energy
input/effect seems worth factoring into these types of calculations.
We should not be looking to calculate any renewable energy option into the
ground. We will need all of them (including High Wind) to power our
civilization.
Dr. Gaskill, when they wake you up, I'll cook breakfast!
My reading of the article suggested that the authors of the study were
principally claiming that wind has an impact on climate, so it is already
being "used". What wasn't clear from the article was what type of impact
reducing the energy level of winds all over the globe through the
prolific use of wind turbines might have. In a warming world, I
understand we should expect stronger winds. On a simplistic generalized
level that might not be relevant to local climate, slowing those stronger
winds down might have an ameliorating effect on climate change. Hence the
claim that "The magnitude of the changes was comparable to the changes to
the climate caused by doubling atmospheric concentrations of carbon
dioxide" might not be as bad as it is made to seem.
As usually, I'm grasping at straws, but as a layman, that's what stood
out for me.
Nando
On Sat, Apr 2, 2011 at 3:15 PM, Alvia Gaskill [email protected]> wrote:
Wind and wave energy are the result of the conversion of
solar energy into kinetic energy, ie the motion of molecules. Once
converted into kinetic energy it's a use it or lose it proposition.
Extracting kinetic energy from the atmosphere or the ocean doesn't mean
it won't
be replaced by more energy from sunlight. Planting more trees will also
intercept winds, albeit without the electricity generation. Who funded
this research? The same people who want to prevent contact with alien
civilizations? I note that the Royal Society was also a party to that one
too. Note to Royal Society. When you actually find something under
the bed I should be afraid of, wake me up.
----- Original Message -----
From:
Andrew Lockley
To: geoengineering
Sent: Friday, April 01, 2011 8:10
Subject: [geo] Wind and wave energies are
not renewable after all
Wind
and wave energies are not renewable after all
30
March 2011 by Mark
Buchanan
Magazine
issue 2806. Subscribe
and save
For
similar stories, visit the Energy
and Fuels and Climate
Change Topic Guides
Editorial: "The
sun is our only truly renewable energy source"
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.
Is solar electricity the answer?
A
solar energy industry large enough to make a real impact will require
cheap
and efficient solar cells. Unfortunately, many of the most efficient of
today's thin-film solar cells require
rare elements such as indium and tellurium, whose global supplies could be
depleted within decades.
For
photovoltaic technology to be sustainable, it will have to be based on
cheaper
and more readily available materials such as zinc and copper, says Kasturi
Chopra of the Indian Institute of Technology, New Delhi.
Researchers
at IBM showed last year that they could produce solar cells from
these elements along with tin, sulphur and the relatively rare
element selenium. These "kesterite" cells already have an efficiency
comparable with commercially competitive cells, and it may one day be
possible
to do without the selenium.
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.
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--
Nando M. Breiter
The CarbonZero Project
CP 234
6934 Bioggio
Switzerland
+41 91 606 6372
[email protected]
www.carbonzero.ch
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