Note: Descriptions are shown in the official language in which they were submitted.
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COLLECTOR FOR RAINWATER FALLING AT SEA
Background-Field of Invention
This invention relates to the collection, storage and distribution of
rainwater
and other forms of fresh water precipitation falling over the seas.
Background-Description of the Prior Art
The collection of rainwater has always been a necessity in many parts of the
world where water is scarce, but this art has primarily been a land-based
activity involving the use of land areas either as catchment sites or as
foundations to support catchment structures such as basins, rooftops,
gutters, tarmacs and fog collecting nets.
The areas of seas where abundant rainwater falls is vast, and is of the order
of billions of hectares. When rainwater falls into the sea, it is no longer
fresh water. Unless rainwater falling over the seas is collected before it
mixes with seawater, fresh water is lost.
Rainwater in the open seas has never been collected to any significant
degree. Conceivably, floating marine structures such as ships and barges
could collect water by utilizing their deck areas to contain precipitation out
at sea. However, these areas are extremely small compared with the areas of
seas over which rainwater falls. Moreover, the costs of construction of such
deck areas and their supporting hull structures would be unfeasibly high
especially if such a method were to be used for the purpose of collecting
precipitation.
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Relatively inexpensive floating vessels, similar in principle to inflatable
dinghies, have been proposed for the collection or storage of rainwater in
sheltered bodies of water such as lakes and coastal bays. To develop on this
principle for use in the open seas, the problem of stability has to be solved.
Essential to this solution is the factor of size of the floating vessels. It
is a
known principle in naval architecture that an increase in the principal
dimensions of a floating vessel, notably the width, generally increases the
metacentric height of the vessel for greater hydrostatic stability.
Furthermore, dynamic stability against the forces of wind and waves is
increased when such floating vessels are flexibly rafted together. Even
then, under sufficiently severe storm conditions, such rafted vessels could
flip over and stack against one another much like the way a folding map
stacks together, unless the individual size of the rafted vessels is large
enough to withstand the capsizing moment of the severest of projected
storms in the area. However, when floating vessels increase in size,
structural stress increases due to the increased bending moments of longer
waves encountered and the increased dynamic forces from motion, such as
rolling, pitching and heaving, acting on these longer structures. A very
large inflatable dinghy would bend and kink in much the same way as an
elongated toy balloon would kink when the ends are pulled towards each
other. Using stronger materials for the vessel's structures may be a solution,
but that would increase costs, and depending on the size of the vessel and
the materials used, these costs could approach that of a conventional
vessel's hull.
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A suitable invention needs to be not only economically feasible, but also
enable large-scale coverage while withstanding the forces of wind, waves
and currents at sea. Additionally, the invention has to be able to
substantially prevent contamination due to seawater spray generated during
stormy conditions.
U.S. Patent 3,230,967 to Castro (1966) discloses a rigid tank open at its top
and bottom supported by a sea borne float and connected to storage bellows.
It requires the use of sumps and pumps to transfer collected water into the
bellows. From stability and cost considerations, it does not allow for large-
scale coverage.
U.S. Patent 3,730,120 to Dobell (1973) discloses an apparatus for collecting
rainwater using a floating collar which supports a deck for rainwater to fall
onto and drain via a non-return valve into a collecting vessel below. The
floating collar incorporates a wave barrier surrounding each collecting
vessel, which is connectable to other collecting vessels using grommets. As
these floating collars are single units without articulating means, if they
are
connected to form a large-scale catchment area at sea, the enormous forces
of wind, waves and current in storm conditions would cause the collectors
to fold over and stack, as explained above, especially if the floating collars
are not large relative to the heights of waves. On the other hand, if the
collars were to be made relatively large, but when subjected to stresses from
heavy seas and long-wave bending moments, use of large floating collars
without articulating means would require the collars to be built from high
strength materials such as steel, as for a modern ship's hull, instead of
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plastics as proposed. Furthermore, the pockets of sea surfaces exposed at
the periphery of each collector will allow seawater spray to be generated by
wind and waves resulting in contamination of collected rainwater. This
renders the apparatus impractical and uneconomical for large-scale use in
the open seas.
U.S. Patent 4,092,827 to Schneider (1977) discloses an apparatus for
capturing rainwater at elevated aerial locations above the seas. It requires
the use of lighter-than-air balloons, aerial funnels and ducts. Since wind
speeds generally tend to be high during times of precipitation, wind forces
combined with the weight of the apparatus and the weight of an appreciable
quantity of fresh water will require the use of many large balloons. These
will in turn generate yet greater wind loads. Even if suitably strong and
light materials were available, the cost of the apparatus would be
uneconomical compared to alternative means of fresh water collection on
land or production through desalination processes presently available.
U.S. Patent 5,010,837 to Hirose (1991) discloses a floating raceway
consisting of a floating bank portion and a raceway portion, all made with
flexible film material, with the intention of storing and transporting water.
While the function of collecting rainwater is not claimed by Hirose, the lack
of stiffness in the structure will not enable the apparatus to maintain the
opening in the floating bank portion to collect rainwater as well as maintain
the necessary volume in the raceway portion to contain the water. Under
the action of wind and forces of the sea, the flexible floating banks would
collapse together and cause the collected water to be squeezed out and over
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the floating banks.
WIPO Patent Application International Publication Number WO 02/40125
A2 issued to Glozman (23 May 2002) discloses a water collection device
essentially similar to Dobell's but without the collecting deck and the non-
return valve. It also uses a single piece buoyant support fastened to an
impermeable membrane collector sheet into which rainwater falls. A
flexible material covers over the collected water under normal conditions to
prevent evaporation and is individually rolled back with a roller for rainfall
collection. It is rolled up or unrolled as necessary with the action and
function similar to that of a cover for a small swimming pool. A baffle is
used to form a shielding wall around a limited group of floating collectors
so as to prevent waves washing over and depositing seawater onto the
collector sheet. The floating collector is towed to a pump station to transfer
the collected water for storage. As in Dobell's collar stated above, the
buoyant support is a single piece frame without articulating means thereby
causing it to fail for the same reasons if used on a large scale in stormy
seas.
Together with the individually operated cover rollers and the baffles, the
design renders the apparatus impractical and uneconomical for large-scale
use in the open seas.
All the above designs do not envisage coverage of substantial areas of the
open seas. They would fail to collect rainwater at sea on a practicable large-
scale and are economically uncompetitive with present day alternatives of
fresh water production such as desalination of seawater.
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Summary
The object of the present invention is to provide a method of rainwater
collection at sea which is technically feasible and economically competitive
with present day alternatives of fresh water production. It provides for
floating booms connected together with flexible joints into a stable and
seaworthy ring, which hold in place a flexible waterproof catchment bag.
Tension ties constrain the shape of the ring to ensure the mouth of the bag
stays open for rainwater to fall into and allows the collected rainwater to be
contained within the bag for storage and subsequent delivery. The
articulated floating boom ring and catchment bag form a modular catchment
unit, which is flexibly rafted together with other units to form larger
catchment networks for increased stability and coverage. The size of
individual catchment networks covering several hundred hectares of sea
surface is envisaged. The design and installation of the system allows for
the adoption of mass-production processes.
Objects and Advantages
Accordingly, the objects and advantages of the invention are:
a) to provide a catchment module consisting of a ring of floating booms
connected by articulating means to form a polygonal shaped boom
ring from which suspends a catchment bag consisting of a flexible
waterproof membrane for catching and storing rainwater and other
forms of weather precipitation;
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b) to provide a plurality of such modules which can be flexibly rafted
together in a modular fashion to form large scale catchment networks
to cover large areas of the seas;
c) the modules may be anchored to the sea bottom at as many points as
necessary to prevent drift due to wind, current and waves;
d) floating pump stations may be joined to the catchment network to
deliver the collected rainwater via flexible piping into tankers or pipe
delivery systems;
e) the use of flexible joints to connect adjacent floating booms together
allows large networks to be built yet reducing the problem of stresses
due to bending and torsional forces, and motion caused by sea waves
on elongated floating structures;
f) the use of tension ties as constraining means for individual catchment
modules enables the modules to maintain their desired shape;
g) the use of flexible waterproof membranes for the catchment bags
allows the collected rainwater to be completely buoyant in the sea
without generating excessive load stresses in the membranes or
floating booms;
h) the use of flexible waterproof membranes for the catchment bags
allows sea waves to be transmitted through the catchment network
without generating excessive dynamic stresses in the membranes or
floating booms;
i) the large scale catchment network using modular units assembled
tightly together minimizes exposed sea surfaces within the catchment
network thereby reducing contamination especially to the inner
modular units due to seawater spray caused by wind and waves;
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j) the use of articulating means to connect floating booms together
allows for the construction of sufficiently large boom rings able to
withstand capsizing moments in stormy seas and yet able to withstand
bending stresses due to long-wave bending moments;
k) the use of articulating floating booms avoids situations inherent in
single-piece buoyant supports where one portion of the buoyant
support is thrust downwards whilst the corresponding opposite
portion is thrust upwards during stormy seas, a motion known as
pitching, resulting in the uprising portion attempting to lift the load of
collected water thereby causing damage to the buoyant support or
membrane;
1) the modular nature of the catchment network allows all parts to be
mass-produced to achieve economies of scale;
m) the modular nature of the catchment network allows any damaged
module to be isolated without contaminating the collected water
contained in the rest of the modules;
n) the modular nature of the catchment network allows any damaged
module to be easily replaced;
o) the simplicity of the invention as designed allows for the use of a
floating factory vessel to rapidly lay and connect the catchment
network modularly onto the sea surface till the required coverage is
achieved;
p) compared with desalination processes for fresh water production,
collection of 'sea rain' by this means is economically competitive and
uses no energy in the large-scale production of fresh water and
therefore does not contribute to global warming.
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Further objects and advantages will become apparent from a consideration
of the ensuing description and drawings.
Drawing Figures
Fig 1 shows a hexagonal catchment module. (Plan View)
Fig 2 shows a vertical cross-section of the catchment module.
Fig 3 shows flexible end joints and tension ties connecting the ends of
booms. (Side Elevation)
Fig 4 shows a catchment network consisting of several modules connected
by rafting ties. (Plan View)
Fig 5 is an expanded view showing a junction of the catchment network.
Fig 6 shows the catchment module equipped with a perforated cover.
Reference Numerals In Drawings
Catchment Module
12 Boom
14 End Joint
16 Tension Tie
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18 Catchment
Bag
20 Wood Log Core
22 Rubber Tube
24 Polymeric
Foam
26 D-Shackle
28 Ringbolt
30 Rafting Tie
32 Suction Pipe
34 Cover
36 Perforation
40 Sea
42 Rainwater
Description
Fig 1 shows a plan view of the preferred embodiment of a catchment
module 10. Although the module has a hexagonal shape, other shapes such
as triangles, rectangles and circles are possible. Module 10 consists of six
buoyant struts or booms 12 connected at their ends to adjacent booms 12 by
flexible end joints 14 to form an articulated boom ring. The boom ring,
floating in the sea 40, is constrained to maintain the hexagonal shape by
tension ties 16 connected across the far ends of every two adjacent booms
12.
Fig 2 is a sectional side view of module 10 with catchment bag 18
suspending downward and attached to booms 12 to contain the collected
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rainwater 42. Bag 18 may be made of any flexible waterproof membrane or
fabric such as polyethylene sheet. Depending on the design load of
collected rainwater and sea conditions, a flexible waterproof material of
appropriate tear strength may be used. Bag 18 may be shallow, essentially a
membrane loosely stretching across the mouth of the boom ring, or it may
be deep, if a larger quantity of water is to be collected and stored.
Booms 12 may be constructed using any flexible or rigid elongated material
that is buoyant in seawater including wood logs, rigid foam core tubes, and
air-inflated and pressurized tubes. Fig 2 shows a preferred embodiment
where boom 12 is of a composite construction consisting of a wood log core
20 within a rubber tube 22 filled with polymeric foam 24.
Fig 3 is a side view of two adjacent ends of booms 12 connected by flexible
end joints 14 which may be any form of flexible joints including universal
joints, swivel joints, hinges, chained links and ropes. In the preferred
embodiment, flexible joints 14 consist of wire ropes with looped ends.
Tension ties 16 may be rods, poles, tubes, ropes or any material capable of
sustaining a tension force. In the preferred embodiment, tension ties 16 also
consist of wire ropes with looped ends. End joints 14 and tension ties 16
are shown attached to the floating booms through D-shackles 26 to ringbolts
28 attached to wood Iog core 20.
Fig 4 shows a plan view of several catchment modules 10 joined together
with rafting ties 30. The modules are positioned within a matrix where
other modules may be added to form a large floating catchment network.
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The number of modules joined together may be any number necessary to
cover an area of sea where rainfall is to be collected.
Fig 5 is an expanded plan view showing a junction of the hexagonal matrix
where a module is joined to other modules. Rafting ties 30 connect the
modules flexibly together. In the preferred embodiment, rafting ties 30 also
consist of wire ropes with looped ends connected through D-shackles to
ringbolts 28.
As shown in Fig 2, a flexible suction pipe 32 is installed with one end
attached to the center of catchment bag 18. Suction pipe 32 is connected to
other suction pipes serving other catchment bags and piped to suction
pumps (not shown).
Fig 6 is a plan view of an alternative embodiment showing an additional
installation of a perforated cover 34 across the mouth of catchment module
and attached to the boom ring. Cover 34 is made from any material, such
as film, fabric or foam board, that is buoyant in fresh water and has
perforations 36 or other means that allow water to drain through.
Operation
Catchment module 10 is deployed individually or in combination with other
modules to form a catchment network over an area of the sea where rainfall
is sufficiently available for collection. Where necessary to prevent drift due
to wind and current, anchors may be installed at as many points as
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appropriate to hold the modules in place.
During rainfall, rainwater falls onto catchment bag 18, which is held afloat
and open by the ring of booms 12. The hexagonal shape of the opening in
this preferred embodiment is constrained by flexible end joints 14 and by
tension ties 16. End joints 14 connect the booms into a ring while tension
ties 16 maintain the angular orientation of adjacent booms. Although six
tension ties 16 are shown in this embodiment, more may be used as
necessary, such as across the far ends of every three adjacent booms, to
further constrain the ring of booms 12 to maintain the desired hexagonal
shape. End joints 14, being flexible, enable said booms 12 to individually
pitch, roll, heave and yaw during storm conditions without transmitting
substantial bending and torsional stresses to adjacent booms. This allows
for the use of longer booms and, in turn, increases the overall size and
stability of the individual modules 10. Other constraining means, such as
installing a rigid floating foam board or a fabric or netting with the size
and
shape of the opening may be used, in place of or in conjunction with tension
ties 16, to maintain the hexagonal shape of the opening and to reduce loss of
collected water through evaporation.
As shown in Fig 2, the accumulated rainwater 42, being less dense
compared to seawater, floats on the sea surface separated from seawater by
the flexible waterproof membrane bag 18. The collected rainwater level
(FWL) is shown above the seawater level (SWL). The freeboard of booms
12 contains the height above the sea surface level of the accumulated
rainwater within bag 18. For every 1 m design depth of collected rainwater,
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approximately 25 mm to 30 mm minimum freeboard is required depending
on the salinity of the location at sea.
For further increased stability and for increased coverage, several catchment
modules 10 may be flexibly rafted together as shown in Fig 4. In the
preferred embodiment, rafting ties 30 consisting of flexible joints connect
adjacent modules and substantially enable the modules to roll and pitch
independently. This reduces the stress load transferred between modules
and allows for larger modules to be used.
Perforated cover 34, as shown in Fig 6, reduces losses of collected rainwater
through evaporation and through spray generated by wind and waves.
Perforations 36 allow rainwater to drain into the collection space below the
cover. An additional function of cover 34, if it is made from high strength
or reinforced material, is to maintain the shape of the opening of the
module.
Although means for transferring collected rainwater to delivery systems is
not claimed, Fig 1 shows suction tube 32 which suck the collected rainwater
by means of suction pumps when sufficient rainwater has accumulated. The
collected water may be pumped to tanker vessels moored nearby or via pipe
delivery systems for use or processing onshore (not shown). In large
catchment networks, contamination due to seawater spray will be very much
reduced in inner catchment modules compared to the outer modules at the
periphery of the network because the inner modules are protected by the
outer modules. This fact allows for the advantageous selection of modules
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in the transfer of collected water to delivery systems and, if necessary, for
the discard of collected water in the peripheral modules.
Conclusion, Ramification, and Scope
Heretofore, rainwater falling at sea has largely not been collected. Seas
cover four-fifths of the earth's surface. Although not all areas of the seas
have abundant rainfall, many areas of seas especially in the equatorial
latitudes and in coastal regions have sufficient rainfall to justify its
collection. The demand for fresh water in many parts of the world has
outstripped supply. Shortages of water caused by population growth, over-
pumping of aquifers, pollution of riparian basins, climate change and global
warming, and the increasing tendency of some jurisdictions to sequester
sources of diminishing water supply previously shared with others have
resulted in many areas of the world suffering from water crises.
This invention of a collector for rainwater falling at sea is presented to
solve
many of the problems faced by others when contemplating the means to
salvage 'sea rain'. Even if they had wondered about the use of an
inexpensive and vast plastic sheeting laid onto the sea surface, problems
such as tearing of the sheeting, spilling of the collected rainwater into the
sea, contamination by seawater spilling onto the sheet, and the drifting of
the sheet away from the designated area are not easily solved.
Accordingly, this invention using catchment modules presents a technically
feasible and economical solution to these and other problems. The module
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may be used singly, such as for the fresh water requirement of a fish farm at
sea, or in combination with other modules to form large networks to collect
the world's 'sea rain', which would otherwise be lost.
The catchment modules floating at sea or in lakes may also be used in
conjunction with many purposes including the following:
- as fresh water reservoirs;
- as ponds for fish and aquatic life;
- as ponds for marshy plants;
- as ponds for migratory birds to rest and feed; and
- as floating platforms to support plant and equipment such as solar
energy conversion cells.
Thus the scope of the invention should be determined by the appended
claims and their legal equivalents, rather than by the examples given.
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