Air Wells & Dew Ponds

Humans need to drink at least

Two quarts of water daily to remain alive. If groundwater is not available, the atmosphere humidity can be condensed instead to provide our minimum requirements.

In 1993, Reginald E. Newell (M.I.T.) found 10 huge “atmospheric rivers” (5 each in the northern and southern hemispheres) with typical flow rates of 165 million kilograms of water per second. These rivers of vapor are bands up to 480 miles wide and 4,800
miles long, about 1.9 miles above the earth. They are the main means of transporting water from the equator. It should be possible to draw water from these rivers. The problem of accessing that height is not insurmountable, especially if the construction is done atop mountains. (1)

The collection of atmospheric humidity is an ancient technology that has been largely ignored in modern times. The most impressive example of this science was discovered in 1900-03 during the excavation of Theodosia (a Byzantine city dating to about 500 BC). Archaeologists found numerous pipes, about 3 inches in diameter, leading to wells and fountains in the city. The pipes were traced to a nearby hill, and were found to originate from 13 piles of limestone, each about 40 feet tall and 100 feet square. This system of ?air wells produced as much as 14,000 gallons of water daily!

Dew Ponds

Dew ponds have existed since prehistoric times, but today the technology is nearly forgotten. A few unfailing dew ponds can still be found on the highest ridges of England’s bleak Sussex Downs and on the Marlborough and Wiltshire Hills. Though far from any marshes, springs or streams, they always contain some water that condenses from the air during the night. Arthur J. Hubbard described a dew pond in his book Neolithic Dew-Ponds and Cattleways (1907):

“There is [in England] at least one wandering gang of men… who will construct for the modern farmer a pond which, in any suitable situation in a sufficiently dry soil, will always contains water. The water is not derived from springs or rainfall, and is speedily lost if even the smallest rivulet is allowed to flow into the pond.

“The gang of dew-pond makers commence operations by hollowing out the earth for a space far in excess of the
apparent requirements of the proposed pond. They then thickly cover the whole of the hollow with a coating of dry straw. The straw in turn is covered by a layer of well-chosen, finely puddled clay, and the upper surface of the clay is then closely strewn with stones. Care has to be taken that the margin of the straw is effectively protected by clay. The pond will eventually become filled with water, the more rapidly the larger it is, even though no rain may fall. If such a structure is situated on the summit
of a down, during the warmth of a summer day the earth will have stored a considerable amount of heat, while the pond, protected from this heat by the non-conductivity of the straw, is at the same time chilled by the process of evaporation from the puddled clay. The consequence is that during the night the warm air is condensed on the surface of the cold clay. As
the condensation during the night is in excess of the evaporation during the day, the pond becomes, night by night, gradually filled. Theoretically, we may observe that during the day, the air being comparatively charged with moisture, evaporation is necessarily less than the precipitation during the night. In practice it is found that the pond will constantly yield
a supply of the purest water.

“The dew pond will cease to attract the dew if the layer of straw should get wet, as it then becomes of the same temperature as the surrounding earth, and ceases to be a non-conductor of heat. This practically always occurs if a spring is allowed to flow
into the pond, or if the layer of clay (technically called the ‘crust’ is pierced.”

Additional construction details were explained in Scientific American (May 1934):
“An essential feature of the dew-pond
is its impervious bottom, enabling it to retain all the water it gathers,
except what is lost by evaporation, drunk by cattle, or withdrawn by man.
The mode of construction varies in some details. The bottom commonly consists
of a layer of puddled chalk or clay, over which is strewn a layer of rubble
to prevent perforation by the hoofs of animals. A layer of straw is often
added, above or below the chalk or clay. The ponds may measure from 30
to 70 feet across, and the depth does not exceed three or four feet.? (2)
(Figure 1)

Figure 1: Dew Pond ~

Spiral Dew Pond (Oxteddle Bottom, Sussex, 1997)

( Photo by Chris Drury )

Another form of dew pond was invented
by S.B. Russell in the 1920s. It was described in Popular Science
(September 1922):

“A dew reservoir 30 feet square will
collect 24,000 gallons of water in a year, or an average of 120 gallons
daily during the hot summer months and 50 gallons daily for the remainder
of the year…

“The Russell reservoir consists of
a concrete cistern about 5 feet deep, with sloping concrete roof, above
which is a protective fence of corrugated iron which aids in collecting
and condensing vapor on the roof and prevents evaporation by the wind.
The floor of the cistern is flush with the ground, while sloping banks
of earth around the sides lead up to the roof.

“Moisture draining into the reservoir
from the low side of the roof maintains the roof at a lower temperature
than the atmosphere, thus assuring continuous condensation.

“At one side of the reservoir is
a concrete basin set in the ground. By means of a ball valve, this basin
is automatically kept full of water drawn from the reservoir. (3) (Figure
2)

Figure 2: Russell’s Dew Pond ~

Air
Wells ~

In 1930, the Belgian inventor Achille
Knapen built an “air well” atop a 600-foot high hill at Trans-en-Provence
in France.Its construction took him 18 months to complete. The unique structure
was described in Popular Mechanics Magazine, thus:

“The tower… is about 45 feet tall.
The walls are from 8 to 10 feet thick to prevent the heat radiation from
the ground from influencing the inside temperature. It is estimated that
the aerial well will yield 7,500 gallons of water per 900 square feet of
condensation surface.” (4) (Figure 3)

Figure 3: Knapen’s Air Well ~

[ Knapen Air Well Photo: International
Organization For Dew Utilization ]

An article in Popular Science
Magazine (March 1933) also featured Knapen’s air well and included
these details of its construction:

“[The air well has] a mushroom-like
inner core of concrete, pierced with numerous ducts for the circulation
of air; and a central pipe with its upper opening above the top of the
outer dome.

“At night, cold air pours down the
central pipe and circulates through the core… By morning the whole inner
mass is so thoroughly chilled that it will maintain its reduced temperature
for a good part of the day. The well is now ready to function.

“Warm, moist outdoor air enters the
central chamber, as the daytime temperature rises, through the upper ducts
in the outer wall. It immediately strikes the chilled core, which is studded
with rows of slates to increase the cooling surface. The air, chilled by
the contact, gives up its moisture upon the slates. As it cools, it gets
heavier and descends, finally leaving the chamber by way of the lower ducts.
Meanwhile the moisture trickles from the slates and falls into a collecting
basin at the bottom of the well.” (5, 6)

Unfortunately, however, the structure
did not perform as hoped; at best, it collected only about 5 gallons per
night.

Knapen was inspired by the work of
bioclimatologist Leon Chaptal, who built a small air well near Montpellier
in 1929. The pyramidal concrete structure was 3 meters square and 2.5 meter
in height (10 x 10 x 8 ft), with rings of small vent holes at the top and
bottom. Its 8 cubic meters of volume was filled with pieces of limestone
(5-10 cm) that condensed the atmospheric vapor and collected it in a reservoir.
The yield ranged from 1-2.5 liters/day from March to September; In 1930,
the structure collected about 100 liters from April to September, but only
half that much in 1931. The maximum yield was 5.5 lb/day.

Chaptal found that the condensing
surface must be rough, and the surface tension sufficiently low that the
condensed water can drip. The incoming air must be moist and damp. The
low interior temperature is established by reradiation at night and by
the lower temperature of the soil. Air flow was controlled by plugging
or opening the vent holes as necessary.

Chaptal drew his inspiration from
a surprisingly successful experiment by Friedrick Ziebold, who constructed
an atmospheric condensor atop a hill at Feodosia (Theodosia), Crimea, modeled
after the ancient air wells discovered there in 1900. Ziebold’s condenser
was a pile of sea pebbles(10-40 cm diam.), 20 meters in diameter and 1.15
meters high. The construction yielded up to 360 liters/day until 1915,
when it began to leak due to a crack in the wall.

Friedrich Zibold’s Atmospheric Condenser (Feodosia, Crimea, 1912)

( Photo: International
Organization For Dew Utilization )

Calice Courneya patented an air well
in 1982 (USP #4,351,651):

“A heat exchanger at or near subsurface
temperature… is in air communication with the atmosphere for allowing
atmospheric moisture-laden air to enter, pass through, cool, arrive at
its dew point, allow the moisture to precipitate out, and allow the air
to pass outward to the atmosphere again. Suitable apparatus may be provided
to restrict air flow and allow sufficient residence time of the air in
the heat exchanger to allow sufficient precipitation. Furthermore, filtration
may be provided on the air input, and a means for creating a [negative]
movement pressure, in the preferred form of a turbine, may be provided
on the output…

“The air well is buried about 9 feet
deep. The entrance pipe is 3-inch diameter PVC pipe (10 ft long), terminating
just near the ground… This is an advantage because the greatest humidity
in the atmosphere is near the surface.” (7, (Figure 4)

Figure 4: Courneya’s Air Well
~

In a preferred embodiment, the intake
is provided with a cyclone separator to precipitate dust before the air
enters the pipe. In addition, a flow restrictor device can beinstalled
before the exit port.

Air flows through the pipes at 2,000
cubic feet per hour at 45oF with a 5 mph wind. This translates
to about 48,000 ft3/day (over 3,000 lb of air daily). Courneya?s
first air well used a turbine fan to pull air through the pipes. Later
designs employed an electric fan for greater airflow. At 90oF
and 80% Relative Humidity (RH), the air well yields about 60 lb water daily.
At 20% RH, the yield is only about 3 lb/day. The yield is even lower at
lower temperatures.

It is difficult to calculate the
amount of water that can be collected. The yield depends on the amount
of air and its relative and specific humidity, and the soil temperature,
thermal conductivity, and moisture. Acoustic resonance within the pipes
might enhance condensation. The more recent invention of acoustic refrigeration
could be used to advantage, as well as the Hilsch-Ranque vortex tube.

The water collected by the Courneya
air well is relatively pure, equivalent to single-distilled water. Analysis
of water collected by an air well near a busy street found no sulfur or
lead (measured in ppm).

In the 1950s, the French inventor
Henri Coanda designed an elegant method to produce pure water from saline.
He designed an enormous silo with reflective walls, which was mounted several
inches over a tidal pool. The silo was angled so as to catch and multiply
the sunlight, thus superheating the air in the chimney. The rising hot
air drew in cold air from the bottom, and became super-saturated with moisture
by the time it reached the top. Fans then pulled the air through a condenser
from which pure water flowed. The residual brine also is of great value
to chemical industry and in the construction of solar ponds. The French
government forced Coanda to cease operations because his device threatened
their monopoly on salt production. Coanda described his “Apparatus for
Purification of Undrinkable Water” as follows in the abstract of his USP
# 2,803,591:

“Apparatus for the purification of
non-potable water comprising, in combination, an installation for heating
a circulating mass of air, said installation comprising at least one tubular
element through which said air circulates and at least one trough-like
mirror of parabolic section having the focal axis thereof horizontally
disposed, with said tubular element disposed along said focal axis of said
mirror, said mirror with its associated tubular element being mounted in
the plane of symmetry of said mirror, and also being mounted to rotate
about a vertical axis…” (9, 10)

Coanda also received USP #2,761,292
for his “Device for Obtaining Drinkable Water”. He offered the following
explanation:

“It is known that the air contains
water and according to my invention the energy for precipitating this water
can be taken from the air itself in motion. It is known that for a given
temperature a given volume of air may not contain more than a certain quantity
of water vapor. When it contains this quantity it is said to have reached
its saturation point. Moreover, this point varies with the temperature,
and the cooler the air, the less water vapor it may contain for a given
volume.

“Consequently, when a relatively
warm volume of moist air is cooled to a sufficiently low temperature, it
yields the water it contained in excess over the quantity permitted by
the saturation point at the temperature to which it has been cooled.

“In a continuous process of producing
fresh water, it is necessary to absorb the heat derived from the warm moist
air at a speed corresponding to the rate of cooling…”

Coanda recommended that the condenser
be buried so the earth could absorb the heat:

“For example, one cubic meter of
air from a wind whose temperature is about 40oC can contain
up to about 50 grams of water vapor; if the wind is forced to enter a certain
space by passing along… a radiator in which a fluid circulates at the
temperature existing 7 or 8 meters below the round level, that is of about
11oC, this wind will immediately precipitate on the radiator
walls the portion of the water content which is in excess of that permitted
by its saturation point at the cooler temperature, that is, about 40 grams
per cubic meter of air, as the saturation point of air at 11oC
is 10 grams per cubic meter. The heat given off, which must be carried
away by the fluid in the radiator, represents approximately 32 calories
for said one cubic meter of air… It is advisable to pass the fluid through
a second radiator of larger dimension disposed in the ground at a certain
depth.

“If the humidity of the warm air
is definitely below 50 grams of water per cubic meter, that is, if the
air is far from its saturation limit, and if the device for obtaining fresh
water is disposed near the sea, it is possible to use [windmills] for spraying
sea water into the warm air in fine droplets, thereby increasing the amount
of water contained in the warm air through the partial evaporation of the
sea water thereinto..”(Figures 5, 6)

Figure 5: Water in Air ~

Figure 6: Coanda’s Air Well ~

Other humidity condensers have been
built in recent years. Soviet cosmonauts aboard space station Mir used
a system that

recovered water from the air. The
Aqua-Cycle, invented by William Madison, was introduced in 1992. It resembles
a drinking fountain and functions as such, but it is not connected to any
plumbing. It contains a refridgerated dehumidifier and a triple-purification
system (carbon, deionization, and UV light) that produces water as pure
as triple-distilled. Under optimal operating conditions (80o/60%
humidity) the unit can produce up to 5 gallons daily.

Fog
Fences ~

In 1945, South Africa’s chief meteorologist,
Theodore Schumann, proposed the construction of a unique cloud-condenser
on top of 3,000 ft. Table Mountain on the south side of Capetown. Schumann’s
design comprised two large parallel fences of wire netting, one insulated
and one grounded, which would be charged with a potential difference of
50-100 KV. The wire screens were to be about 150-ft. high, 9,000 ft. long,
and 1 foot apart. He estimated that the electrified fence would condense
as much as 30,000,000 gallons daily from “The Cloth”, a perpetual cloud
that crowns the peak. The fence was never built. (Figure 7)

Figure 7: Schumann’s Fog Fence
~

Alvin Marks invented the “Power Fence”
to generate electricity from the wind by means of a charged aerosol which
was dispersed from microscopic holes in the tubing of the fence. Marks
calculated that if the wind averaged 25 mph, a mile of fence would generate
about 40 megawatts. The towers would be 500 feet high, strung with a grid
of steel bars in a rectangular array, subdivided into a lattice of 4-inch
squares. The squares are divided by a mesh of perforated tubules through
which the water flows. Marks? patent states that the system can be used
to modify weather and to clear fog. (11, 12)

The EGD Fog Dispersal System invented
by Meredith Gourdine has been used at Los Angeles and Ontario International
Airports and by the Air Force since 1986. The system uses an electrically
charged mist that is sprayed into the fog over runways, thus clearing them
for landing:

“[The system is comprised of] an
array of charged submicron water droplet nozzles {and select] characteristics
of a cloud of charged droplets… including a field strength… a charge
concentration, a time constant, [etc.,] whereby clearing of the airborne
particles occurs…by attachment of the emitted submicron droplets to the
airborne particles to the ground.” (13, 14)

A similar system was invented by
Hendricus Loos (USP 4,475,927):

?[The system consists of] gapped
air jets laden with electrically charged droplets of low mobility, a ground
corona guard in the form of a shallow water-and-oil basin, and a charged-collector-drops
emitting device on the ground, arranged in such a manner that the low-mobility
charged droplets blown aloft by the air jets form a virtual electrode suspended
at an appropriate height above the ground, toward which the oppositely
charged high-mobility collector drops move, thereby collecting the neutral
fog drops in their paths?? (15)

Chilean scientists have developed
a revolutionary “fog trap” at Chungungo, Chile. A group of 50 fog-traps
made of plastic mesh stand atop a 2,600 ft. mountain and collect up to
2,000 gallons daily. The villagers call it “harvesting the clouds”. Walter
Canto, regional director of Chile’s national Forest Corporation, said:

“We’re not only giving Chungongo
all the water it needs, but we have enough water to start forests around
the area that within 5 or 6 years will be totally self-sustaining.”

Another 21 sites (1,000 acres total)
on the Pacific coast of Latin America also have fog traps. Some of the
locations have become self-sufficient because the trees have become large
enough to collect fog for themselves, just as the ecosystem did before
settlers disrupted it. Fog-forest ecosystems survive precariously on droplets
of water collected by their leaves. Some such forests, surrounded by deserts,
have been sustained by fog for millenia. Very little cutting is necessary
to initiate gradual but complete destruction.

The ideal location for fog traps
are arid or semi-arid coastal regions with cold offshore currents and a
mountain range within 15 miles of the coast, rising 1,500 to 3,000 feet
above sea level. Mesh occupying 70% of the space is most effective for
trapping fog droplets. Two layers of mesh, erected so as to rub together,
optimize the collection of water in PVC pipes attached to the bottom of
the nets. Collection varies with the topography and the density of the
fog. The fog trap at Chungongo is 40 x 13 feet and produces 45 gallons/day.
As the fog becomes denser and more frequent in the summertime, water production
doubles.

Air wells, dew ponds and fog fences
offer real hope for thirsty humanity. The quantity of water thus produced
is not likely to meet the needs of large-scale agriculture, yet countless
lives can be saved by this simple, elegant technology.

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