[Assam] A paper on Reverse Global Warming

[Mohan R. Palleti]

Folks,
What do you think of this paper? Please comment.

Mohan



Reverse Global Warming While Generating Energy, Water And Revenue
By Steve Nixon and Shawn McCaslin


Global warming has emerged as a serious global crisis.  Many ideas have
been proposed for mitigation, but the existing ideas, even in the
aggregate, do not provide a compellingly sufficient, timely, and
cost-effective solution.  The key to controlling global warming is a
system to regulate the mean global temperature--that is, if the Earth is
too hot, we need a way to cool it, a way that is predictable,
controllable, and affordable.  It seems clear that, to be effective, any
global temperature control system must have the ability to overwhelm the
heat problem.  The system and method to reverse global warming disclosed
herein meets these requirements, while simultaneously providing large
quantities of fresh water and electricity.

Alternative Approaches
Existing proposed approaches involve poorly understood, slow, indirect
and/or expensive means with little to no real-time flexibility.  For
example, reducing carbon dioxide production, and/or sequestering CO2
captured at the source from large polluters, by reducing the 'greenhouse
effect', which is certainly amplified by CO2, both of these methods would
eventually reduce global warming, but only gradually and incrementally,
since there is so much CO2 already in the atmosphere and oceans.  Properly
disposing of CO2 emitted by facilities burning fossil fuels would be
helpful, and possibly quicker and more effective than many straight
reduction efforts, since such installations generate a great deal of
carbon dioxide in a relatively concentrated and point-source form, which
is more
easily monitored and regulated.  Alternative fueling systems exist (at a
cost) which large coal-burning plants can use to produce
highly-concentrated CO2, just right for sequestration.  Yet reductions of
net emissions tend to increase costs, at least in the short term, and for
Carbon Capture and Sequestration (CCS), the costs will be on-going.  As
history shows, cost increases inevitably result in resistance and slow
adoption, regardless of the pollution-reduction method.
Meanwhile, new drilling, conversion of coal into oil and gas synfuels,
development of tar sand and oil shale deposits, decentralized coal
burning, and even deforestation, are all likely to increase significantly
as oil prices rise and existing oil reserves are depleted.  These will all
lead to releases of large quantities of CO2, much being in the form of
diffuse releases, which thus are impractical to capture and sequester
using conventional approaches.  Also, developing nations continue to
release ever-growing quantities of CO2, while CO2 sequestration is likely
to be practiced only by wealthy developed nations.  But even if all large
point-source emissions were captured, sequestration alone is unlikely to
be sufficient due to the cumulative effects of billions of small,
difficult to control point-source emitters (homes, small businesses,
automobiles, etc.)
While the century-long average residence time of atmospheric CO2 is a
major hurdle to prompt reduction of CO2-induced warming, what really hurts
the potential of efforts to reduce CO2 emissions is the oceans' current
excess of CO2.  This dissolved CO2, accumulated over centuries, will
immediately begin to come out of solution and return to the atmosphere as
soon as net CO2 emissions are decreased (in accordance with le Chatelier's
Principle), thus largely defeating the short-term benefits of reduced CO2
emissions.
Of course, sequestering CO2 and otherwise reducing net CO2 emissions are
good ideas, but these are only two of many possible small, corrective
steps.  Perhaps enough small steps, in the aggregate, could be sufficient
to stave off global environmental disaster--if we do not pass through a
climatic 'tipping point' beforehand, as many experts predict we will. 
Unfortunately, the optimistic view is pinned more on hope than on sound
judgment of engineering, environmental, economic or political issues.  It
is not at all clear that the small steps, even in aggregate, really can
offer a timely, sufficient and cost-effective solution to global warming. 
While reduction of net CO2 emissions would be a step in the right
direction, a bolder and much more direct and immediate form of control
seems far more helpful.
Even if small steps could work, a key flaw in the 'lots of small steps'
approach is that most of the proposed small steps depend on people's
willingness to make altruistic sacrifices of harm to themselves in the
short term.  It is particularly unlikely that people in developing nations
will be willing to make economic sacrifices, since for them, survival
itself is frequently a challenge, and survival is likely to become
increasingly difficult for many populations as the mean global temperature
increases and weather patterns change.  This overall bleak outlook is made
still worse by the fact that as developing nations grow and prosper across
the globe, their volume of greenhouse gas emissions increases, and will at
some point outstrip the total emissions from the currently developed
nations.  At that point, net CO2 emissions will begin to rise again even
if the developed nations have reduced their net CO2 emissions to zero. 
Instead of reducing emissions, however, the current trend is a move back
to more extensive use of the worst offender, coal, instead of the more
expensive but less CO2-intensive alternatives, oil and gas.  The situation
begins to appear hopeless, and desperation leads to proposals of some
truly grandiose 'cures'.
A recurring suggestion for a possible means of directly defeating global
warming is through the control of incident solar radiation, using mirrors,
shields, lenses, or gratings deployed in space.  At first glance this
seems an attractive option, since it provides direct control.  But it
still relies on altruism, and on a truly grand scale.  The expense and
additional pollution incurred to build and deploy such a system would be
huge (even if it were made from lunar materials), and it would require
enormous short-term sacrifices.  Then too, in view of humanity's
demonstrated inability to universally ratify the Kyoto treaty, which is in
comparison a much more modest proposal in required short-term economic
commitment, it seems highly unlikely that a space-based solution could be
successfully deployed sufficiently quickly.  In addition, the space-based
solutions are feared by some for their possible use as weapons!
The various shortcomings of the existing proposals for mitigating global
warming prompt us to suggest that to be truly 'green', sustainable, and
affordable, the preferred solution should have seven key attributes:
positive economic benefits (both short-term and long-term); immediate
deployability with off-the-shelf technology; no requirement for
international cooperation and consensus; minimal negative environmental
'footprint'; direct and predictable controllability of a large-scale
process for decreasing the mean global temperature; production of large
quantities of electricity; desalination of large quantities of water.

Heat Processing in Earth’s Atmosphere
To understand how such control might be accomplished, consider first how
Earth's atmosphere naturally processes heat: The heat 'source' is
primarily at the Earth's surface; i.e., much of the Sun's incident
radiation passes through the atmosphere and most of that light is
converted to heat when it reaches the surface.  In the lower layers of the
atmosphere, much of that heat is trapped near the ground by the insulating
effects of water vapor in particular, plus CO2, methane, etc., and the
bulk effect of simple density.  'Greenhouse gasses' increase the
insulative effect only slightly, but do so on a very wide scale, holding
back some of the thermal radiative emissions.  To the extent that the
solar energy does not immediately reflect or re-radiate back into space,
it undergoes a one-way conversion to heat.  That heat energy accumulates
temporarily in the lower atmospheric layers, interacting with the surface
and the air, until the air itself becomes hot enough to either re-radiate
the energy into space despite the insulative effects, or for air masses to
rise up to an altitude where they can re-radiate the energy into space.
In denser air, the molecules are closer together and thus appear somewhat
like 'a solid wall' to long-wavelength infrared, but shorter wavelengths,
corresponding to higher temperatures, can 'squeeze through the gaps' and
escape into space.  Heated air both absorbs and re-radiates 'blackbody'
infrared energy.  Unlike visible light, this infrared energy near the
ground does not tend to radiate back into space; instead, it tends to
reflect back and forth, being re-absorbed and re-emitted by both air and
ground.  Some escapes as radiant energy, but a large fraction does not. 
Much of this energy goes into heating the air mass itself until, through
convection, the heated air rises.  Then, at altitude, the heat diffuses
more easily, rising and scattering through the remaining 'thin' atmosphere
until the remnant air allows the heat to radiate into the only available
heat sink: outer space.
As a result, there is a general convective circulation of air from the
Earth's surface to the upper atmosphere and back.  But that exchange of
air is chaotic and non-uniform.  Through the process of convection, hot
air rises in 'blobs' towards the cooler upper atmosphere (often forming
characteristic cloud types) and mixing turbulently with the surrounding
cooler air in the process.  As the air mass rises, it also expands,
becoming less dense and cooler.  This mixing and thinning cools the hot
air, but not by radiation of heat into space.  The same amount of heat is
still present, but now at a lower temperature, which thus is slower to
radiate heat energy.
By this expansion and mixing, what started out as hot air becomes air
which is merely cool.  Compared to hot air, cool air must rise higher into
the atmosphere before it can efficiently radiate its heat into space, yet
air which is merely cool may lack the buoyancy necessary to rise that
high.  Thus, turbulence and mixing, which are good things in a mechanical
heat-exchange device, can greatly impede the heat-transfer process in the
atmosphere.  Hot air blobs are typically stopped and dissipated before
they rise high enough into the upper atmosphere to effectively radiate
much of their heat into space.  However, large masses of rising hot air
can retain coherence longer than can small blobs, and so dispose of heat
more effectively.  (This is all greatly simplified, and there are several
competing processes at work simultaneously.)
As a large, hot, humid air mass rises, it expands, becoming less dense and
cooler, eventually causing the moisture in the mass to begin condensing
into droplets, and finally into ice crystals if it rises high enough (but
herein we will refer only to droplets).  This moisture condensation
process has a remarkable effect--the air temperature increases! (Just as
evaporation cools air, so condensation heats air; the process is
reciprocal.  While this self-reheating does not normally completely cancel
out the expansional cooling, it does tend to insure that when air rises
moisture-laden, it is warmer and less dense than the surrounding cool, dry
air.)
This reheating accelerates the damp air upward, potentially forming a
thunderstorm.  Even though the air continues to cool some as it rises, it
remains warmer and less dense than the surrounding air outside the rising
mass, until finally the rising mass is high enough in the atmosphere to
effectively radiate heat into space directly.  Also, the rate of heat
release into space from the top of a rising cloud is greater than the heat
release rate from dry air at the same altitude and temperature, because
the cloud droplets are a much more efficient radiator surface than dry
air, which has no surface.  These effects make the interiors of
thunderstorms relatively warm, while the tops of thunderstorms are
relatively cold due to the greatly accelerated radiation of heat from the
droplets.  Combined with the greatly accelerated vertical flow of heat in
the form of warm, wet updrafts, these effects cause thunderstorms to have
a huge net cooling effect on the atmosphere around and below the
thunderstorm.

The Proposed Solution
Given these principles of physics, one way to cool the Earth's atmosphere
and surface relatively quickly is to arrange for hot air to rise up from
the Earth's surface while preventing the turbulence and mixing that would
normally dissipate blobs of hot air.  To accomplish this, you need a bit
of ancient technology: a chimney.  A BIG chimney.  Not for smoke, just for
air.  As warm or hot air rises in a chimney, more of this air is drawn in
from the bottom.  As long as a source of relatively warm or hot air
remains at the bottom, air will, of its own accord, flow up through the
chimney indefinitely, creating a flow through suction.  Here is a very
important point: Due to the chimney walls preventing inflow and mixing
with air from the sides, a chimney of a given height generates a much
stronger suction than can occur in open air under the same conditions of
heating.  Since ancient times, the draft from this 'chimney effect' has
been harnessed as a cooking aid, to turn rotisseries driven by small wind
turbines in the solid chimney base.  In a big chimney, this suction can
spin large wind turbines and generate much electricity, using as 'fuel'
mostly the low-temperature, leftover heat supplied for free by the Sun. 
Note that one does not have to supply larger and larger amounts of heat to
keep chimneys working as they are made taller.  In fact, the opposite is
true, taller chimneys work better: they make stronger suction.  Stonger
suction together with increased resistance to flow through the wind
turbines will generate more output power, even while the heat input and
the mass of air flowing through the chimney may remain constant.
The idea of a giant 'solar chimney' is not new either; the Australian
company EnviroMission plans to build one as soon as possible, one which
uses hot, dry air.  (See www.NewEnergyReport.org/016709.html, the content
of which is incorporated herein by reference.) However, their proposed
rigid chimney will be 'only' 1000 meters (1 km) tall and about 120 meters
in diameter.  While that would make it by far the world's tallest manmade
structure, and while it could generate 200 MW of pollution-free electric
'wind' power continuously, it would not be tall enough to be efficient at
either generating electricity (less than 3% thermal conversion efficiency)
or at cooling the atmosphere significantly, and the two effects go
hand-in-hand.  To move air high enough into the atmosphere for serious
cooling and power generation to occur, a chimney would need to be much
taller--perhaps on the order of 5 to 6 km.
If building such a tall chimney were possible, and the feed air were warm
and wet enough, the result would be a continuous sort of 'captive
thunderstorm' operating 24/7.  Large volumes of warm, damp air would move
up the chimney at moderately high speed under the influence of a strong
suction driven by the self-reheating effect, offering prodigious amounts
of suction-driven wind power.  Then, by imparting a small, controlled
amount of spin to the rising air, the larger water droplets would be flung
outwards to collect on the inner walls of the chimney, where considerable
volumes of this directly potable purified water would flow into drains and
down to the base for use and re-use.  (Additional water may be collected
near the top of the chimney by passing the updraft through a web of
strings running in all directions, like some spider webs do, which
prevents resonant vibrations.) Such 'wet' chimneys also potentially offer
much better 'availability' and 'up time' than most other solar or wind
energy systems, especially if the chimneys are placed in the tropics, away
from seasonal temperature variations.
A single tall chimney of, say, 300 meters diameter, could easily move
several (up to 125) cubic kilometers of air per day.  Several dozen of
these chimneys could, for example, turn part of Western Australia green
(literally and figuratively), while also significantly cooling the
regional atmosphere.  Several hundred, scattered about, could lower the
mean global temperature somewhat.  Several thousand of these 'wet' solar
chimneys, scattered around the planet, could lower the mean global
temperature significantly.  With enough units, global warming can be
reversed, even in the face of current elevated levels of CO2!

Practical Considerations
The key question, then, is "How could we construct such chimneys so that
the capital costs would be in line with the demands of short-term economic
return?" If such profit-making mega-chimneys were possible, altruism would
not be needed; construction would proceed rapidly, motivated by normal
capitalistic profit motives.  Indeed, if the economic return were good
enough, construction would likely need to be regulated to avoid excessive
global cooling! Though these mega-chimneys will be expensive, this idea of
good economic return is more realistic than may at first appear, for three
important reasons.
First, there is a 'geometrical economy of scale': Since these chimneys are
hollow cylindrical tubes, the amount of material involved in construction
(for a specified height) is basically proportional to the diameter of the
chimney, while the airflow capacity is basically proportional to the
square of the diameter.  Thus, all else being equal, if you make a chimney
twice as wide, it costs twice as much, but it moves four times as much
air, and it generates four times as much water and power, for an
approximate doubling of the net return on investment (2^2 = 4, 4/2 = 2). 
Similarly, if you make a chimney three times as wide, it costs three times
as much, but it moves nine times as much air and generates nine times as
much water and power, for an approximate tripling of the net return on
investment (3^2 = 9, 9/3 = 3), and so on.  Therefore, in principle, the
return on investment can be made quite large! It is only necessary to
avoid compromising other factors in the process of enlargement.
Second, the rigid base serves multiple essential functions: Initial riser
for generating suction; Housing a plurality of large wind turbines and
their associated wind tunnels, control valves and spin vanes; Anchorage
and storage for the inflatable tube portion of the chimney.  Additionally,
the very considerable area on the outside walls of the solid base
structure (above the wind tunnels and wind turbines) can easily be
designed to support high-rise office and residential space with a superior
view and commanding high prices for that reason as well as for the
prestige and 'green bragging rights' of this sort of address.  Interior
parts of the thick walls may be designed for multi-use roles.  The zone
encircling the tower base may be divided into rings or sectors where, for
instance, industrial facilities may be built for ready access to large
quantities of electricity, cooling water and personnel.  In other zones
around the base, residential and agricultural areas may be placed.  All
may benefit from the chimney's large volumes of condensate water, ranging
from tepid to cool to almost ice-cold.  Hot water may also be provided
quite economically, heated by solar ponds, by greenhouses or by collected
waste heat.  Even the interior 'floor' of the chimney base may find
additional uses, such as an energy storage area.  All these extra
activities and spaces make the chimney complex more prestigious, 'greener'
and more attractive and valuable in several senses, all yielding a greater
income for the project.
Third, while the building of 5-to-6 km tall towers out of steel-reinforced
concrete is unrealistic, both economically and technically, there is an
alternative: Build a hybrid, with the first, say, 2 or 3 hundred meters
made of concrete, but build the next 5 or 6 thousand meters out of
inflatable cylindrical sections to boost the created suction and to insure
discharge at a higher, colder altitude.  For a simple scale model, think
of this: an overgrown stack of inflated bicycle inner tubes all laying on
their sides and stacked up upon each other.  The inflatable sections would
be designed so that, when deflated, they would slip inside the rigid
concrete base section, out of harm's way.
In this mega-chimney, each of the inflatable sections would have walls
made of a light, rugged, airtight and (preferably) non-flammable material
such as 'PBO' (poly-bis-oxazole, twice the strength-to-weight ratio of
Kevlar, and fireproof) or gel-spun polyethylene (or any other material
with a high strength-to-weight ratio) or some combination of such
materials, probably varying in different layers, bonded together into a
very strong, heavy-duty fabric with protective outer layers, perhaps of
glass cloth, to guard against damage from UV (ultraviolet light).  The
sections might have a flexible metal skeleton made of cables, which might
spiral and counter-spiral almost vertically, and which would shunt
electrical charges to ground while also anchoring the inflated portion to
the solid base.  Flexible water pipes or hoses would also run vertically
or almost vertically, from condensate-collecting 'rain gutters', or other
devices, arranged at various heights, and collecting water at higher
pressures and lower temperatures from the upper zones.  This water would
be conveyed to the base for use in various ways, perhaps passing through
water turbines or hydraulic motors to generate power while also lowering
pressure to more normal values (water descended from 6km altitude with no
pressure drop would exert a pressure of almost 600 atmospheres or almost
8700 PSI).  Alternatively, the collected condensate water could be passed
through a plurality of pressure regulators as it descended, or passed
through rather narrow pipes and hoses, which would reduce the pressure in
a distributed way by the action of flow friction, while also minimizing
weight.
The sections would be inflated with and slightly pressurized using a
non-flammable blend of helium+hydrogen (or separate gas bags, nesting
hydrogen inside helium or nitrogen), to make the sections semi-rigid,
slightly buoyant, and fireproof, while also conserving the scarce
resource, helium.  In effect, the inflatable chimney would be a long,
vertical, hollow blimp: lighter-than-air, double-walled and attached to
the ground at the rigid base.  The slight pressurization of the buoyant
gas, together with internal cross-connects between inner and outer walls,
would make the tube hold its cylindrical shape against oscillations, and
resist effects of the internal suction produced by the rising air, likely
with the aid of higher pressure ribs in the form of 'bicycle inner
tube'-shaped (meaning "relatively skinny") gas compartments.  These
structures, together with others, would provide resistance to the kind of
'suction collapse' which can afflict a soda straw in a thick malt. 
Instead of the no-flow condition of a flat straw, it is desired to have
maximal flow, and pressurized circumferential ribs can help accomplish
this in a manner rather like that seen in pressurized firehoses:
semi-rigid and tending towards smooth, even curves.  It may be found
desirable to divide the inflated circumferential ribs into a plurality of
sealed chambers so as to reduce the chances of a kink developing in the
desired smooth curve and to minimize the effects of possible leaks. 
Either way, the buoyancy of the inflatable structure would keep the tube
in tension and approximately vertical.
As a somewhat cheaper non-power-boosting alternative, some or all of the
major cylindrical sections may be made to restrict the airflow along the
length (like a windsock) or at the upper terminus, either of which would
result in a self-pressurized tube, which would still deposit the heat at
high altitude, while avoiding the internal suction.  A power-generating
chimney could be made using both types of cylindrical sections, and
possibly other types, even if there is no suction in the upper portion.
Alternatively, it might be possible to engineer an inflatable chimney in a
very different way, possibly using heavier-than-air gasses to inflate, and
most likely using highly pressurized vertical or near-vertical inflated
'standing ribs' (somewhat like a collection of parallel firehoses, but
inflated with high-pressure air) to provide the necessary vertical
support, together with circumferential or near-circumferential inflated
'ribs' providing resistance to 'suction collapse' as described previously.
 Exactly how high one can build with this method alone remains to be seen.
When lighter than air gasses are employed, it may be desirable to reserve
them for use in the middle and upper chimney sections, especially when
standing ribs are used to support the lower section (above the massive
base).  This will both conserve the use of expensive gasses and assist
with deflation procedures, when needed, by keeping the chimney system
operational through as much of the process as possible, and therefore able
to contribute power to both winching and gas compression operations
(necessary for conserving the buoyant gasses).  A lower section supported
by standing ribs inflated with simple compressed air or nitrogen would
seem to have two additional desirable characteristics: Deflating that
final, lower section may be unnecessary in the case of high winds (which
are mostly at high altitudes), and even if full deflation is required,
mere air or nitrogen does not have to be conserved and can just be vented,
meaning no power is required for running compressors or winches.
It may be found attractive to use a combination of all these chimney types
together: massive, rigid base at bottom, then standing ribs section, then
lighter-than-air section, all three with suction, and finally a 'windsock'
section with no suction, but with enhanced water collection.
Relating to changes of altitude for the various sections being raised or
lowered, atmospheric pressure 5.5 km up is half the pressure at sea level
(one 'atmosphere' of pressure, 14.7 PSI (1 atm.), drops to 7.35 PSI,
one-half 'atmosphere'), which equates to a nominal doubling of gas volume
at the lower pressure.  This presents some challenges for gas compartments
which are nominally 'sealed', and mostly affects the circumferential rib
type of gas compartments, which must not go limp if 'suction collapse' is
to be prevented: If such compartment were inflated to normal stiffness at
lower altitude and then allowed to rise up to higher altitude, the lower
outside pressure would tend to result in that gas compartment being
overinflated at the higher altitude.  This could either rupture the gas
compartment, which must absolutely be avoided, or require it to be
over-built (with a heavier material) to withstand the excess pressure. 
Lofting heavier weights is very unfavorable and over-building could cost a
lot more, so these approaches may not be optimal.
One possibility for dealing with changing external pressure is to have gas
compartments which stretch and shrink to accommodate changes in volume,
while maintaining a fairly constant internal pressure.  This sounds just
about ideal, but could be quite hard to accomplish in practice, especially
with the weight constraints and the range of ambient temperatures.
However, the gas compartments which help resist 'suction collapse' are
operated at above atmospheric pressure anyway, and this will tend to help
swamp out the percentage change of pressure with altitude.  Assuming the
gas compartments are essentially non-stretchy: If initial pressure is set
at sea level to 1.5 atm, the pressure loading on the cloth is 1.5 - 1 =
0.5 atm.  Then at 5.5 km, the pressure difference is 1.5 - 0.5 = 1 atm,
which is exactly twice as great: 1 / 0.5 = 2x, a 100% increase in pressure
loading stress.  But if initial pressure is set at sea level to 2 atm, the
pressure loading on the cloth is 2 - 1 = 1 atm.  Then at 5.5 km the
pressure difference is 2 - 0.5 = 1.5 atm, which is less of a difference in
loading: 1.5 / 1 = 1.5x, a 50% increase in pressure loading stress.  Or if
initial pressure is set at sea level to 3 atm, the pressure loading on the
cloth is 3 - 1 = 2 atm.  Then at 5.5 km the pressure difference is 3 - 0.5
= 2.5 atm, which is still less of a difference in loading: 2.5 / 2 =
1.25x, a 25% increase in pressure loading stress.  An interesting pattern
is apparent, but it is also a pattern of diminishing returns, especially
when the extra weight is factored in for carrying the higher pressures. 
Thus, it's an optimization problem.  Another consideration is the changing
balance of forces, as high-altitude winds tend to be of higher velocity
but with reduced air density.  Yet winds of a given density exert a force
which varies as the square of velocity.  Which effect dominates? It
depends on wind speed and altitude!
With fixed quantities of lifting gasses, and if not otherwise handled in
one of the above manners, provisions must be built in for adjusting gas
pressure to suit altitude.  The compartments could be made to vent excess
pressure; for instance, into a gas recycling system, but that approach
seems problematic in its own way.  Another approach is to run thin 'gas
hoses' down to the rigid base, where an active pressure-control system can
be employed to prevent overinflation.
Similar, but generally smaller, concerns apply to gas pressure changes
resulting from temperature changes.
Besides the use of large, numerous or high-pressure circumferential ribs
to maintain the major tube in the desired state of wide-open
cross-section, despite suction, another approach is to employ a plurality
of interior cable stays from one side of the tube to the other.  This can
help maintain an approximately circular cross-section, help prevent
'suction collapse', and help detune large-scale resonance frequencies. 
These cables need not follow diameter lines.  It may prove beneficial to
angle the cables somewhat, vertically and/or horizontally.  Best practice
would seem to involve use of the lightest, strongest material for these
cables, possibly PBO, as well as the use of streamline fairings, probably
of thin cloth, on the cables to reduce wind resistance.  These fairings
may be small inflatable structures in themselves, but not necessarily
carrying static pressure.  They may instead be arranged with inlet ducts
or slots on or near the leading edge, which convey air to the enclosed
trailing space immediately downwind of the cable, and thus use the motion
of the chimney's internal updraft to inflate the streamline with
appropriate-pressure air, for 'free'.
To maintain the rather sharp trailing edge of these lightly-pressurized
'pipes', it seems necessary to have spaced along their length, internally,
a plurality of 'teardrop'-shaped or wedge-shaped stays of cloth, strings,
or otherwise, so as to redistribute the pneumatic stresses and enforce an
overall 'airfoil' shape, at least to the area behind the cable.  Also,
cables need not be circular in cross-section, nor must they be used
singly.  Instead, it may prove desirable to make the cable stays in the
form of bundles of parallel tethers attached to each other so as to impart
an overall 'airfoil' shape.  Or, it may prove desirable to make the cables
in the form of a plurality of tethers, perhaps as few as two, which would
occupy a few key points on the outline of the cross-section of an airfoil,
with some material, probably light cloth, being attached to the tethers
and forming the streamline shape, as before.  As few as two tethers might
be used, to act as the 'leading edge' of a mostly-open streamline shape,
rather like a thin parasail, but with massively reinforced leading edges
formed by the tethers.  The twin-tether approach may be favored as it
seems able to provide a 'sheltered area' (out of the 'wind' of the chimney
updraft) where water droplets gathered from the passing updraft can
coalesce and run downward to be deposited in the nearest water collection
zone.
All these streamlined structures may be either asymmetrical airfoils, like
normal airplane wings, in which case they may have an influence on the
overall rotation of the rising air mass inside the chimney cross-section,
or they may be symmetrical airfoils, like stunt plane wings, in which case
they would seem to have little to no influence on the overall rotation of
the rising air mass inside the chimney.
In all cases, by acting against the anchor mass at the base, the
upward-oriented forces within the major inflatable structure will and must
keep the tube primarily in tension and nearly vertical despite the shear
force from normal crosswinds, which will increase vertical tension on the
windward side and decrease vertical tension on the leeward side, which
creates a 'restoring force' pointed into the wind such that the overall
chimney tends toward vertical.  This 'restoring force' can be made larger
by increasing the upward-oriented 'lifting' forces within the major
inflatable structure, but the diminishing returns of this goal must be
balanced against the increased size, cost, weight, and wind resistance of
larger components.  Note that the shear force does not cause a torque on
the flexible chimney; instead, shear force is translated into tension,
just as with a string tethering a floating balloon, and this tension acts
upon the base, mostly on the windward side, but appropriate arrangements
of the vertical/near-vertical/spiraling/counter-spiraling cables should be
employed so as to distribute this tension, as much as feasible, along the
entire windward side of the base, rather than allowing the stress to
concentrate on the point most directly aligned with the wind.  Note also
that the wind direction spoken of here refers mainly to wind at altitude,
which may, and often will, blow in a different direction from wind at the
rigid base structure.
It may prove desirable to impart some streamlining to the exterior of the
chimney as well, either with inflatable structures or with vertical
'wings' or with 'slats' or 'flaps' which help redirect the ambient wind
into the low-pressure region immediately downwind of the chimney.  The
complicating factor here, of course, is that the ambient wind may vary in
direction, and thus any exterior streamlining techniques must be able to
vary their position or effect in order to still function properly.

Operational Considerations
One big problem would seem to be high-speed crosswinds.  The chimneys
could likely be designed to tolerate normal crosswinds without resorting
to draconian measures such as external guy wires, but a chimney might need
to be deflated and stowed in anticipation of an approaching strong weather
system.  If the chimneys are constructed in the appropriate manner, and
placed in appropriate geographic areas, the need for such protective
action should be rare.
Another aspect, possibly beneficial, but possibly a problem, is that
chimneys may be so effective at drawing in surface-heated air as to
disrupt the local natural atmospheric convection.  That is, the chimneys
may, in effect, 'repel' storms, thus reducing normal local rainfall.  For
this reason it may be desirable to locate the chimneys in naturally arid
areas, and to supply them with extra humidity from seawater, which the
chimneys will then desalinate for 'free' (in terms of major energy use),
followed by irrigation as necessary using the desalinated water.
Alternatively, any available source of fresh or brackish water may be used
to add humidity.  Humidity can be added to the inflowing air by spraying
water mist into the air, by passing the air over ponds of various
configurations, or over growing plants, or over large wicks, etc., or a
combination.  In any case, it is desirable to have a large and continuous
supply of warm, wet air to the base of the chimney.  Ponds and canals can
help capture and store large quantities of ambient and solar heat at very
low cost, thus helping the chimneys to perform better on an
around-the-clock basis.
Exactly how continuous a supply of heated and humidified air is optimal
will depend on a number of factors, such as the need for an unvarying
power output and the ability to use that power somehow.  It is suggested
that the entire chimney complex be designed to function nearly normally
even in 'worst case' conditions, and that the excess of power available in
better conditions be used in part to store large quantities of energy in
some form as a hedge against the times when conditions may be bad.  The
interior floor of the chimney seems ideal for storage tanks of various
sorts, and excavation below ground level there may also be employed,
perhaps for installation of a large flywheel- or superconductive- energy
storage facility.
Output power can be adjusted by varying the wind turbines' resistance to
rotation and airflow, the number of airflow tunnels open to flow, and the
heat+humidity input rates to the chimney.
To maintain the most continuous flow of warm, wet air, the chimneys should
(if locally feasible) be located near the coast in equatorial, tropical or
sub-tropical regions, or in a place like Southern Australia, which is not
subject to strong cold fronts or typhoons.  Of course, Southern Australia
is not equatorial, so the solar heating is not quite as strong there as it
is farther north.
A hot and humid local atmosphere is beneficial but not critical for
efficient operation of the mega-chimney, so long as there is a good supply
of water for humidification, and heat, such as low-grade geothermal heat
and/or waste heat, which could potentially be collected from nearby
residential, commercial and industrial facilities.  Alternatively or
additionally, a 'solar skirt' could be added, as in the EnviroMission
proposal, which would trap solar heat; but note that a skirt might be
unnecessary if the chimney is tall enough.
It may be found desirable to have one-way valve air shutters at
'greenhouse' air inlets, which would allow for capture of some energy from
any prevailing wind at ground level.
To enhance the environmental cooling effect (like Mount Pinatubo's
eruption did), the inflow air could be ‘spiked’ with dust, salt, sulfur
compounds, or other materials, which help to form cloud droplets.  In some
circumstances, such material may already be present in the air drawn in
from the local environment.  'Seeding' with such substances tends to
result in the formation of smaller and more numerous cloud droplets, which
may go on to radiate relatively more heat into space, or less, depending
on the exact characteristics of the droplets.  Since these adjustments to
droplet size and number can be controlled almost independently from power
production, there is great flexibility in the amount of radiational
cooling produced.  Seeding materials may be injected early (at the chimney
base), to affect droplet formation inside the chimney, or late (at or near
the chimney top), to affect droplet formation and lifetime in the
environment at-large.
To help reduce the global 'greenhouse effect', the in-flowing air may, if
desired, be passed over or through devices which adsorb or absorb CO2 from
the ambient air, in effect acting as 'scrubbers' for the atmosphere at
large.  The use of large chimneys to move very large quantities of air for
such scrubbing has been proposed by others, but in that case no power
production capability was suggested.  (e.g. the Lackner Tower, in which a
tall tower creates a downdraft that draws air through a sorbent material
and removes CO2).
Chimneys of the sort already planned for Australia by EnviroMission would
be expensive; their 1000-meter chimney plus wind turbines could cost $500
to $750 million USD while generating only 200 megawatts, which makes
EnviroMission power noticeably more expensive than if it were from
comparable-capacity fossil-fuel plants.  Note that the EnviroMission tower
proposed for humid southeast Australia does not rely on saturating the
inflowing air with moisture.  Quite the contrary, it relies on heating the
air fairly strongly (30 degrees Celsius above ambient) with no moisture
addition, thus insuring that such air is far too dry to experience any
condensation or self-reheating as it flows up their proposed 1000-meter
chimney.  At the same time, such strong heating of the air insures that
most of their giant greenhouse skirt (7000 meters in diameter) is too hot
for growing plants.
However, even a 1000-meter chimney (whether rigid or hybrid) might
generate more power by the addition of sufficient moisture to the
inflowing air, even at the relatively low temperatures compatible with
growing plants.  The revenue from the generated power could be used to
help finance the rest of an inflatable chimney, with promise of more
purified water, and power generation in the gigawatts, as the chimney is
lengthened.  However, there are good reasons for making the chimney as
tall as possible initially, and which may outweigh initial cost savings. 
For instance, taller chimneys yield enhanced efficiency and improved
capture of the humidity as fresh water, as well as the ability to run well
on heat from low-temperature sources (e.g. only slightly above ambient).

Conclusion
It is estimated that, depending on location, size, and other design
details, a few hundred to a few thousand of these multi-gigawatt
mega-chimneys would do more than supply the world with needed electricity,
there would be a large excess of electric power which could be used to
recharge the batteries of electric cars; refine metals; make glass,
bricks, silicon and carbon fibers; synthesize ammonia for both fuel and
fertilizer; produce hydrogen from water, and countless other applications
which would reduce the demand for coal, gas, and oil, while also providing
so much fresh water to arid regions that deserts would bloom. 
(Approximately 1 tonne per second of fresh water production can be
expected for each cubic kilometer per day of airflow, e.g. 125 km^3/day of
airflow could yield about 125 tonnes of fresh water per second, equal to
33,000 gallons per second.)  This large quantity of water, in descending
from an average altitude of about 2 km, would approximately double the net
output power of the MegaChimney.  Note that, at 125 cubic kilometers of
(sealevel) airflow per chimney per day, a fleet of about 8000 chimneys
would process 10% of the mass of Earth's entire atmosphere every year!
It is also estimated that, on a similar-diameter basis, the disclosed
design approach would require only about 1/4 as much reinforced concrete
as the much taller concrete towers proposed by EnviroMission.
'Wet' solar chimneys can provide a sufficient solution for global warming,
where "sufficient" is defined as a controllable ability to overwhelm the
problem with enhanced cooling.  Thunderstorms are existence proof that
'wet' solar chimneys would provide substantial atmospheric cooling. 
Exactly how many such chimneys, of what sizes and details, would be
required to stabilize the mean global temperature is a matter for further
analysis.
By appropriate use of installed mega-chimneys, active control over key
aspects of the outside environments may be achieved, in decreasing degrees
of impact, from local to regional to global.

Summary
In summary, 'wet' solar chimneys are a compelling potential solution to
global warming, possessing these seven key attributes: positive economic
benefits (both short-term and long-term); immediate deployability with
off-the-shelf technology; no requirement for international cooperation and
consensus; minimal negative environmental 'footprint';  direct and
predictable controllability of a large-scale process for decreasing the
mean global temperature; production of large quantities of electricity;
desalination of large quantities of water.  With an appropriate act of
will and comparatively modest initial funding, the inhabitants of the
Earth could be on their way to reversing the rise in mean global
temperature, ending the threat of global warming, and even helping to end
hunger.  All this, and sustainably ‘green’ too!