Hi Joe,

Wonderful thinking about mountains and kites!!! I’ll try to build on your foundation. This is another crazy idea that would definitely work, but it remains to be determined how well it could work and what it would cost. As you implied, mountains cause rain and catch rain, so they are the source of most rivers, which are the sources of most human civilizations. Kite mountains may be the cheapest way to provide artificial falling rivers of water in the face of global warming and droughts.

Where possible, kite mountains might be constructed as fog nets. Fog nets are already in use around the world, but they are typically suspended on poles. A gutter below them collects the water.

If flown high enough, the fog-net-mountains could fly at the level of the clouds most common over a given land area. That would turn them into the equivalent of artificial rain makers, although instead of causing rain, the water would flow down flexible plastic pipes to near the anchor points of the kites. The kite mountains would provide rivers of water flowing from the clouds.

The water flowing down from the great height of the clouds could produce considerable energy from momentum alone (not from pressure, because that would require that kites support a tall, leaning column of water). Because the water would be continuously falling, it would not create a heavy mass for the kites to support.

A fog-net-mountain would be somewhat analogous to the face of a giant damn in that a damn traps water at a higher altitude and then generates electricity as that water falls through turbines. In the case of the fog-net-mountain, the clouds are equivalent to the reservoir behind the damn.

So kite mountains could provide both clean water and clean energy, the two thing we are now most in need of.

In principle, a buoyant kite mountain could be flown using a single anchor point, thus allowing the kite mountain to orient to the wind.

The fog-net should be suspended such that in high winds it can swing away from the wind to reduce its drag.

The original testing could be done in fog at near ground level.

[After writing this entire Email, including the following information on Sharp Rotors, I figured that the basic idea is fairly obvious, so I did a Google search. Indeed, the concept was first thought up a hundred years ago by Nicola Tesla. Bless him. That means I’m only 100 years late to the party! And there is a Russian company called Air HES (Air Hydro Electric System) that is trying to develop it. However, they use aerostats (blimp-shaped balloons) or buoyant wings to support the fog nets, and I don’t think that is going to provide a high enough lift for a low enough cost because such a large amount of helium will be required.

https://www.indiegogo.com/projects/cloud-power-clean-water-and-energy-from-clouds#/  

So I think I my idea of using Sharp Rotor kites is better.

I think that Sharp Rotors would also work better than the motorized rotating cylinder balloons being developed by Omnidea.

http://omnidea.net/site/index.php/research/wind-energy  ]

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I’m just guessing at the lift coefficient. It may be higher than 2 at a spin ratio of 1.

My models are small, with a low aspect ratio. Larger models with a high aspect ratio should have a lift to drag ratio of about 3, the same as for most Flettner rotors.

When driven by auxiliary power, the maximum lift coefficient should reach about 10 for high aspect ratio Sharp Rotors, the same as for Flettner rotors. (The maximum lift coefficient for conventional wings ranges from 1 to 3 using flaps and slats.)

Buoyant Sharp Rotors could provide the very high lift needed to support fog nets. A Sharp Rotor is a 3-sided, cylinder-like rotary wing, with end discs, that auto-rotates to create high lift, at a spin ratio of 1. Lift is due to the Kramer effect, which is that a wind that is increasing its angle of attack can reach a much higher angle of attack, and produce much higher lift, than a wing operating just below its stall angle. A Sharp Rotor has no stall angle, so it doesn’t stall. It doesn’t vibrate.

It can also be easily spun using auxiliary power to create extremely high lift utilizing the Magnus Effect. A Sharp Rotor requires a little more power to spin it at a high spin ratio than a smooth cylinder, but the lift can be as high.

If Sharp Rotors were used to lift fog-nets, the energy to spin them, to create maximum lift, could be derived from the momentum of the falling streams of water passing through a water turbine.

A Sharp Rotor auto-rotates with a spin ratio of one, meaning that its circumference moves at the same speed as its apparent wind. In contrast, a cylinder or Flettner rotor creates very little lift or even negative lift near a spin ratio of one. So if a Sharp Rotor is motorized to cause it to spin a ratio above one, it will produce higher lift than a Flettner rotor up to a spin ratio where their lift ratios become equal, perhaps at a spin ratio of 2 to 3. That implies that the power required to spin the two different rotors will be less for a Sharp Rotor up to a specific spin ratio, and above that specific spin ratio, the Sharp Rotor will require a little more power than a Flettner rotor. That specific spin ratio is not yet known. It will be determined to some extent by the exact profile of the Sharp Rotor.

A Sharp Rotor creates very little torque. But it can be configured to increase the torque by increasing the reverse camber near the trailing edge of each of the three surfaces.

Creating Magnus effect lift is not practical using two-sided rotors because they require far too much energy to spin them at a high spin ratio. They also have two dead-spots, meaning positions where they will not reliably self-start. When auto-rotating, two-sided rotors (Donaldson rotors, US Patent #2501442 A) produce strong vibrations because they stall twice each revolution. Four-sided rotors do not create useful lift when auto-rotating. (In 1977, I patented a Donaldson rotor with dihedral that gave it increased stability when gliding. It used a constant chord length but was much thicker at the ends next to the end discs. So from the front and back it looked like an hour-glass. A Sharp Rotor cannot be given dihedral like that because doing so reduces the lift significantly.)

A Sharp Rotor has a large internal volume so it could be made buoyant using helium or hydrogen.

A kite-mountain fog-net supported by Sharp Rotors would have three operational modes. Mode one would be windless conditions. The buoyancy of the rotors would support the dry fog-net. Mode two would be windy conditions but no clouds. The rotors would auto-rotate to provide the necessary lift to compensate for the wind drag on the fog-net. Mode three would be when there were passing clouds. The rotors would be spun using electric motors to create extreme lift to compensate for the added weight of the water collecting on the nets. The falling water, passing through flexible pipes of thin plastic (coated internally with a hydrophobic compound to reduce friction), should provide much more energy than would be consumed by the rotors to lift the fog-net.

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Information about testing Sharp Rotor models of various kinds:

n  I have tested paper Sharp Rotor models in free-flight gliding using auto-rotation, plus launching them with pre-spin using rubber bands. When pre-spun using rubber bands, Sharp Rotors could glide a little bit farther than comparable, pre-spun Flettner rotors. (Flettner rotors are cylinders with end discs.) The angles of descent are about the same. When launched using rubber bands, both rotors do a quick, tight back-loop before gliding forward.

n  When gliding, Sharp Rotor stability is provided by the pendulum effect -- because the top surface provides most of the lift, and it is above the center of mass (along the axis of rotation).

n  I have also tested a paper Sharp Rotor whip-stick glider/kite with a high wing loading using large, steel washers attached to the paper end-discs. The washers are necessary to create enough centrifugal force so that I can circulate the paper rotor. The lift is impressive. It can fly in tight circles above my head. When I whip it forward rapidly to spin it rapidly, and then instantly stop pulling, it does a quick, small back-loop and remains briefly suspended in air -- if it is facing into a very low wind speed. That demonstrates extreme lift because it can support its own heavy weight in a wind speed of only about 2 mph when the spin rate is very high.

n  About 1977, I flew a paper Sharp Rotor as a single-line kite (about 18” wide) with a large, central disc to provide stability (to avoid side-slip) – similar to some current-day rotor kites. It worked reasonably well, but I think that it needed to be larger, and the central disc needed to be larger for better stability. And it needed better bearings. A buoyant Sharp Rotor kite would not need a central disc for stability.

n  If a paper Sharp Rotor (11” span, 3” chords) is launched underhand, and thrown straight upward, while imparting spin to the rotor, it can do a large forward loop and return to my hand.

n  I also tested a tiny, paper Sharp Rotor (3” wide, 1” diameter) with weighted end-discs that was mounted on a shaft and free to rotate independent of the shaft. I pre-spun the rotor to a high rpm by blowing on it through a straw. When launched by pushing the shaft forward, the rotor does a quick back loop and then glides at a moderate speed with a 2 to 1 glide ratio. The high rate of spin stabilizes it and keeps it flying level. It cannot auto-rotate (because the chord length is too small), so its lift is due entirely to the Magnus effect.

n  I used a Sharp Rotor as the sail of a model land yacht, but the plain bearings caused too much friction. So although it worked, it didn’t work especially well.

n  For use as sails, or kites, Sharp Rotors could be stacked like the rungs of a tall ladder. Rotating the “ladder” 180 degrees around its long axis would reverse the direction of lift. Rotating the “ladder” 90 degrees would eliminate the lift and could be used for overspeed protection.

n  Since they have low torque, the rotors should be mounted on ball bearings to enable then to spin freely.

n  The curves of the Sharp Rotor could probably be duplicated using flat panels to simplify construction, without decreasing lift during auto-rotation, and without substantially increasing the auxiliary power needed to spin them at a high spin ratio.

n  Because a Sharp Rotor creates low torque, it could be easily braked to stop it from spinning so as to eliminate its aerodynamic lift. In other words, it can be easily turned “on” and “off”.

n  It is not yet known if a Sharp Rotor can exhibit the Barkley phenomenon, which occurs when a cylinder is spinning a little below a spin ratio of 1. The drag coefficient drops considerably below the normal drag coefficient of 0.8 for a non-spinning cylinder. The Barkley phenomenon can be used to lower the drag of a Flettner rotor in high winds.

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For ground-mounted fog nets, I thought about saving on the cost and weight of the fog net by using the vertical axis Sharp Cycloturbine or the vertical axis Bird Windmill to move a relatively small fog-net through a very large volume of fog as the VAWT drives the fog-net in a very large circle at 2 or 3 times the speed of the wind. That might create additional cooling due to the wind chill factor that could increase fog capture. The same circulating fog-net concept might be used at the level of the clouds to minimize the total weight of the kite, since fog nets are relatively heavy at present. But I haven’t explored that possibility yet.

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A Sharp Rotor has many uses. For example, it might make a good traction kite if inflatable using pre-formed carbon fiber ribs and spars, plus an inflatable pontoon hanging down at both ends so it could easily take off from water, and 3 control lines. It could also be powered using small batteries and onboard motors. There are lots of options.

PeterS

Hi DaveS,

To be clear, I’m thinking of kite mountains as being loosely analogous to redwood forests that are fed by coastal fog, meaning clouds that are low enough to engulf the hillsides and mountainsides where there are redwood forests. The trees cause condensation and dripping, which for them is the equivalent of rain. So the fog-nets carried up to the clouds would be analogous to redwood trees on mountainsides. A difference would be that instead of causing random dripping, the fog-nets would direct the water to a ultra-lightweight drain pipe extending to the ground.

For creating kite mountains, my guess is that lifting devises using the Magnus effect may be necessary to create a high enough lift for a low enough cost, given that water is so cheap, even in drought stricken areas.

Another use of kites for providing fresh water is desalination along coastlines. I envision an endless row of Bird Windmills (using towers or kites for support) along coastlines used to pressurize sea water for reverse osmosis or other desalination techniques. That way of providing fresh water might be especially cheap, so kite mountains might be better suited – cost-wise -- to inland areas far from salt water, such as the Great Plains of the US where the aquafers are being drained down and will soon be gone, which will eliminate a large percentage of the farming.

By the way, a way to think about the Bird Windmill is to see it as an unfolded, conventional, vertical axis wind turbine (VAWT) with multiple blades all moving in the same circle. For the Bird Windmill, each blade creates a separate circle of its own, so the swept area is enormously increased, and the Bird blade can capture more energy because it has access to more wind during the downwind pass of the blade. For most VAWT, the downwind pass of the blades captures relatively little energy (about 20% of the total).

You raised a very important subject: the concern that kite mountains could extract too much water from the atmosphere and cause less water to be available downwind. I read something relevant to that concern not long ago. I wondered how rain could get inland behind mountains if the mountains caused heavy precipitation. Wouldn’t that make for drought conditions behind the mountains? Well, in some cases, it most definitely does. That’s why Death Valley is downwind of (behind) the Sierra Nevada Mountains. But in other cases, the forests on the mountains transpire large amounts of water that gets carried downwind to behind the mountains where it can be delivered as rain. In other words, some forests create rain, just as water evaporating off the surface of the sea causes rain. Forests can provide rain for other forests that are downwind. For example, much of the rain in the Amazon rainforest is from water transpired from the trees. The rain gets continuously recycled in the downwind direction. I don’t understand why some forests transpire enough moisture to cause rain downwind and some don’t, but it may have to do with the kind of trees and the temperature and the topology (flat may be better), and in some cases the jet streams. In any case, we may need to think about extracting water from clouds in terms of how some natural systems replenish moisture in the air, and how some don’t. And I worry that climatologists may not know enough yet.

A technical/political fix, where affordable, would be to insure that the water from kite mountains was distributed downwind to more than make up for any losses, so as to insure fair distribution.

PeterS

Hi JoeF,

Another possible use for mosquito nets is as an active way to capture mosquitos before they get close to people: use the nets sort of like the butterfly nets that are swept through the air to capture insects for study. But in this case, use, for example, a Bird Windmill (a circulating kite) pulling a net sort of like pulling a tall, narrow parachute made out of mosquito netting. Coat the net to kill the mosquitoes, or spray it with a sticky substance so that the mosquitoes can’t get loose. Then the net could be dipped in soapy water, or spritzed with some liquid, to kill the mosquitos. Beneficial insects might be removed from the net, such as ladybugs. Since the windmill produces energy, the net could be electrified to zap the mosquitos to kill them.

Mosquitoes fly at night when the wind speed is fairly low, and stop flying if it gets too windy. But they fly in wind speeds that are higher than was previously assumed. They are attracted mainly to carbon dioxide which animals exhale, and perhaps to some other trace gasses that contribute to the smell of normal breath. So a source of CO2 would be necessary to draw the mosquitos to the Bird Windmill. That might be done with a tiny fan and a pipe (or covered ditch) that vented air from a nearby home or stable to near the center of the windmill. Or, the Bird Windmill could be mounted right above the house, and air would be vented through a screened hole in the roof by the natural convection of warmed air, or by using a small fan spun by the windmill.

The windmill can be easily mounted above a house without touching the house anywhere (to avoid transmitting noise to the house, and to avoid stressing the structure of the house). The Bird Windmill starts in a wind of 3 to 4 mph, and can continue to orbit in winds as low as 2 mph, but then the orbit diameter is small.

A Bird Windmill made mostly from indigenous materials bamboo support-poles, locally made cords, strips of inner-tube for the bottom shock-cord below the blade, locally made mats for the blade, and free mosquito netting) might cost only a dollars for the swivels. The blade might sweep a ten foot circle in a wind-speed of 6 to 8 mph.

If the blade scared off mosquitos, the net might be mounted in front of the Bird blade to take the place of the normal counterweight. So the mosquitos couldn’t react until it was too late.

The net wouldn’t need to be large because it would sweep a very large area of wind at about twice the speed of the wind.

A Sharp Cycloturbine could be used to do the same thing, and it would start moving the net in winds as low as 1 mph since the windmill has strong starting torque. It could sweep an extremely large area of wind if it were made much wider than tall, and it would cost almost nothing if it were built using local materials. The blades move at about 3 times the speed of the wind. A small net could be mounted out beyond the blades.

Even when there was no wind, a battery could zap mosquitos attracted to an electrified net over the vent hole in the roof. This is basically the way modern mosquito traps made for use on outdoor patios work. They generate CO2 and then zap the mosquitos when they arrive.

As I recall, I’ve mentioned these potential methods for mosquito protection to some aid organizations concerned with malaria, but they showed no interest, perhaps because the concept is too different from what is being done at present (spraying, mosquito nets, releasing sterile male mosquitos). Maybe they see a technical flaw in my suggestions, but I’m not aware of any as yet. Most engineers seem to shy away from these two windmills because how they work is not obvious and requires some study. They can be much cheaper and lighter than other windmills.

PeterS

Hi JoeF,

On the subject of kite lifetimes, I’m concerned that fabrics just can’t last long enough, given that they need to last 20 years, or if they need to be cheap enough to replace periodically. What affordable fabrics, if any, have long lifetimes when exposed every day to UV radiation? If none, then would that define all fabric kites as temporary kites? Some kite people claim that there are fabrics that are very durable, but I don’t know what they are. I know that sails don’t last long when in constant use – maybe a year or two. And I assume that they would use the same materials as kites. Is there a difference?

PeterS

Hi DaveS,

Thanks for showing us this information.

Their drawing looks like an under-developed version of my Turboships (see my article), which have been in the public domain for maybe 10 years, so it’s not clear what they could patent. Their concept seems obvious to anyone “practiced in the art” (patent speak), and obvious devices are not patentable.

Just a reminder: Turboships are robotic, twin-hulled, twin-bow ships that cruise slowly back and forth across the wind, using electric steering pods, while supporting a wall of VAWT on the windward hull and multiple turrets for launching and retrieving energy kites (such as the Makani energy kite) on the leeward hull. Their primary purpose is to produce liquid hydrogen to be transferred to cargo ships and transported to shore. They would operate in fleets of about a thousand ships. They would have the speed to get out of the way of dangerous storms when necessary by using energy from various sources: stored hydrogen, kite pull, kite generated electricity, and wind turbine generated electricity. The machinery would be located in the windward hull and the hydrogen would be stored in the leeward hull. Located below the windward hull, or between the hulls, would be an extremely large, folding, centerboard to provide adequate resistance to the wind forces while moving at a speed of about 1/5 the wind speed. It would fold horizontal under the hulls when entering shallow waters.

Are you objecting to the crudeness of their ship design in the drawing, or do you have something more technical in mind?

PeterS

Hi DaveS,

Thanks much for your comment. Please note that I didn’t advocate depriving redwood forests of fog. That would be counter-productive, to say the least. I was talking about redwood forests as analogous to kite mountains in some ways. If you think I did advocate taking their fog, please quote me so I can see my stupid mistake.

Ironically, given that many redwood forests are now threated by droughts brought on by global warming, we might want to consider using kite mountains to provide them with more moisture during really bad years. Since we are killing them, we might wish to try to save them by extracting water from the clouds above them that aren’t coming down low enough to feed them.

A good scientific question you raise is: What percentage of the moisture in the air could be extracted without causing measurable harm. 0%, 1%, 10%, 50%? I have no idea. Do you have any data on that subject? Should we ban kite mountains until we know? Should be we limit kites to water desalination? What about areas of famine due to lack of rain and inadequate ground water? A great many ecosystems that have endured for tens of thousands of years are now changing too rapidly for their species, especially plants, to adapt. We are currently re-engineering nature without knowing what we are doing, so to what extent should we try to do a better job at deliberately re-engineering nature? Or should we just work as fast as possible to develop energy kites that can replace fossil fuels? Or both?

Here is an odd twist. Research on the turbulence caused by large-scale wind turbines indicates that their turbulence causes an increase in ground moisture evaporation and a drying of the soil. So maybe we will need kites to tap clouds to bring down moisture where wind turbines cause its loss!

PeterS

Hi JoeS,

Interesting info. I wonder which is better suited to cloud seeding, airplanes or kites?

PeterS

Hi JohnO,

That’s an interesting problem to solve. Thanks for mentioning it. If you find any data on the problem, please tell us.

PeterS

Hi DaveS,

Thanks much for your comments. I’ll try to find out more about aviation and architectural fabrics.

And thanks for your other comments today too.

PeterS

Hi DaveS,

Good points. Thanks.

PeterS

Hi JoeF,

Dust damping is an interesting challenge.

On the subject of dust damping, here are some first thoughts:

I assume that lowering the wind speed near the ground would be a way to do that. Cheap Bird Windmills, arranged in long arrays using multiple rows, one behind the other at different altitudes, could function as effective wind breaks – instead of using trees. They could capture energy as well. Leaving crop residues on fields retains moisture in the soil to reduce dust. The arrays would help to prevent winds from blowing away the crop residues. The Bird Windmill blades could be suspended from cords extending between (guyed) tall trees, thus further lowering the costs by eliminating the need for towers (the main expense). Plowing should be eliminated when possible because it is a major cause of soil drying and reduced biota in the soil.

If the energy from the windmills were used to pump warm, summer air through pipes located below farm fields, the warmed soil well below the surface could extend the growing season.

Windmill kites might be used to intercept and compress cold, moist air and send it down from higher altitudes, and channel it to the ground where it would serve to reduce soil evaporation and the creation of dust. The compressed air would be used to generate electricity and provide refrigeration and cooling before being released to cool the soil. The heat of compression would be dissipated by the down tube from the kite to the ground, thus further cooling the air. The system might also yield a significant amount of water (water-from-air technology).

During the winter, Bird Windmill arrays could provide electricity needed to power electric tractors to collect snow into covered ponds to be used during the summer for drip irrigation, which would help to prevent the soil from drying.

They could also be used to pump cold, winter air through underground tubes to provide air conditioning for homes, stables, dairies, and crop storage facilities during the summer.

An underlying theme here is to try to accomplish a number of goals at the same time by thinking in terms of integrated systems.

PeterS

Hi JoeF,

Thanks for sending us the paper. Well done, and darn good for a Masters level thesis. (I skimmed it.) I wrote a paper on flying energy generators (FEG) in 2009 that AWES members might find interesting, so I attached it. After it was published on a computer disc and distributed to a conference on global warming, I found a brief reference to Wayne German. So I now give him due credit. I invented mutually tethered dirigible kites independently as a consequence of developing my Metatheory of Sailing (book in progress), which predicts that they should be possible. I just added some sketches at the end that weren’t included in the original paper due to space limitations.

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I now think that perhaps a particularly effective energy kite would be a manned, flying-wing dirigible equipped with high speed wind turbines. It would fly facing into the strong winds circling Antarctica. It would lower a remotely steered “hapa” (sub-surface device to provide resistance like a centerboard; a sort of upside-down water kite) to enable the dirigible to fly (sail) back and forth across the wind, going hundreds of miles in each direction. It might be able to hold its longitude while generating and liquefying hydrogen. Then, using its wind turbines as propellers, it would fly to the southern tip of South America, Africa, or Australia to unload its hydrogen and take on fresh water before returning. The hydrogen would be carried by ships to ports around the world, and the ships would be powered by the hydrogen venting from the spherical liquid hydrogen containers. Some of the hydrogen ships would intercept cargo ships to transfer hydrogen to them for fuel – so as to reduce the use of bunker-oil fuel, which is highly polluting. The original flying-wing dirigibles would use helium for safety, and they would be manned using a small crew. Eventually the dirigibles would function as autonomous craft using computer control, and they would use hydrogen instead of helium (a limited resource). Special sensors would be used in the air and in the water to spot whales or ice, and avoid them by retracting the hapa briefly. This concept is closely analogous to Wayne German’s concept because it is mutually tethered kites, although one of them is a water-kite. It should be reasonably inexpensive to develop because it could be built and tested using radio-controlled models, and scaled up in small steps.

PeterS