AU2004100619A4 - A cover system for a body of liquid - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION INNOVATION PATENT Applicant(s): HAYDEN JOHN STEIN Invention Title: A COVER SYSTEM FOR A BODY OF LIQUID The following statement is a full description of this invention, including the best method of performing it known to me/us: 2 Field of the Invention The present invention relates to a floating cover system for a body of a liquid such as a dam, a pond, a lake or the like. The floating cover system may be used either to reduce evaporation or encourage evaporation of, for example, a body of water.

Background to the Invention It is not uncommon for 25 to 60% of the water collected in dams in rural areas of Australia to be lost to evaporation caused by the sun or wind or the combination of the two. With long summer periods during which no rainfall occurs, after the water has been evaporated from the dams, fresh water for livestock and farm personnel must be transported to these remote rural areas at great expense.

For other industries, evaporation is encouraged. For example, salt producers typically use a series of evaporation ponds as a first step in a process for recovering salt from seawater. The seawater flows through the series of evaporation ponds and is allowed to evaporate naturally due to the action of the sun and wind. The salt concentration of the water progressively increases, forming a brine. When this brine is saturated with salt, it is pumped into crystallisation ponds where further evaporation causes crystals of the salt to form.

Several ways of reducing evaporation from a body of liquid have been proposed. Backyard swimming pools are routinely provided with covers or "pool blankets" which are formed from a single continuous layer of an insulating material sized to cover the full surface area of the pool. Such pool blankets are often cumbersome to Kirstie/keep/speci/Innovation P53899 02/08/04 3 maneuver and so made of thin plastic material that is prone to tearing during installation or removal of the blanket. Such pool blankets are ill-adapted for use for large bodies of liquid.

US Patent 5,861,095 and US 5,400,549 each described a system for covering sewage lagoons using a series of large rectangular insulated panels connected to each other by a -complex arrangement of grommets and weighted cables. The insulated panels are used to retain the heat generated during degradation of organic material within the sewerage lagoon.

US 6,673,241 describes the use of a flexible, foldable cover system also particularly suited for sewage lagoons to reduce emission of offensive odours and gases. The cover system is made up of a series of separate foldable cover strips that are connected together using welding or sewing to match the size of the lagoon. Each strip has a complex arrangement of layers of materials designed to impart buoyancy and strength to the strips such that the strips are able to support the growth of an aerobic biomass on the upper surface of the strips in use. The flexible strips described in US 6,673,241 must be fixedly attached to each other to prevent the strips from folding over themselves in use in high winds.

For each of the above described cover systems, considerable time is required to connect the units together when installing the cover or to disconnect the units to remove the cover to, for example, conduct a dredging operation on the sewage lagoon.

The present invention was developed to provide an alternative to existing floating cover systems for bodies of liquid to either encourage or discourage evaporation.

Kirstie/keep/speci/Innovation P53899 02/08/04 4 It will be clearly understood that, although prior art use and publications are referred to herein, this reference does not constitute an admission that any of these form a part of the common general knowledge in the art, in Australia or in any other country.

In the statement of invention, the claims and the description of the invention which follow, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Summary of the Invention The present invention provides a cover system for a body of liquid comprising: a plurality of floatable units, each unit dimensioned to cover at least a portion of the body and able to move freely relative to one or more like units, wherein the plurality of floatable units are able to self-arrange to form a substantially uniform cover over at least a portion of the body of liquid.

Thus, when floating on the surface of the body of liquid, the floatable unit are able to tessellate to form a substantially uniform cover over at least a portion of the body of liquid.

Preferably, each floatable unit has a variable buoyancy.

In a preferred embodiment of the cover system as each unit comprises a plate oriented substantially parallel to the surface of the body of liquid.

Kirstie/keep/speci/Innovation P53899 02/08/04 5 Preferably, the plate of each unit is provided with at least one hole to allow fluid communication between opposing sides of the plate.

The cover system can further comprise a barrier which delineates a portion of the body of liquid to be covered from a portion of the body of liquid to be uncovered.

Brief Description of the Drawings In order that the invention may be more easily understood, embodiments will now the described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an isometric view of a first preferred embodiment of one of the floatable units in the shape of an equilateral triangle; Figure 2 is a plan view of the floatable unit of Figure 1 illustrating the location of cross-section A-A; Figure 3 is a cross-sectional representation through section A-A of Figure 2 showing the height of the plate relative to the width of the floatable unit; Figure 4 illustrates a plurality of the floatable units tessellating with respect to each other when placed into a body of water; Figure 5 is an isometric view of a second preferred embodiment of one of the floatable units in the shape of a hexagon; Figure 6 is a plan view of the floatable unit of Figure 5 illustrating the location of cross-section B-B; Figure 7 is a cross-sectional representation through section B-B of Figure 6 showing a plate at the base of the floatable unit; and, Figure 8 illustrates a plurality of the floatable units tessellating with respect to each other when placed into a body of water; Kirstie/keep/speci/Innovation P53899 02/08/04 6 Description of the Preferred Embodiments A first preferred embodiment of the present invention is now described in detail in the context of reducing evaporation from a dam in a rural environment. A second preferred embodiment of the present invention is then described in detail in the context of a cover system used to encourage evaporation of a salt pond used as one stage in the production of salt.

It is to be understood that the cover system of the present invention may equally be used for various purposes on various bodies of liquid, including, but not limited to, ponds, lakes, dams, tailing dams, evaporation ponds, thickeners, swimming pools, fisheries and the like. It is to be understood that the embodiments described in detail below are merely exemplary of the present invention which may be embodied in various forms. The specific structure and functional details described below are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention.

A first preferred embodiment of the present invention is illustrated in Figures 1 to 4 in which there is shown a cover system 10 for a body of liquid 11. The cover system 10 comprises a plurality of floatable units 12, each unit dimensioned to cover at least a portion of the body of liquid 11 and able to move freely relative to one or more like units. By allowing each unit to move independently of the other units, it has been found that the units naturally self-arrange through contact with one or more like units, contact with a boundary surface or through the influence of wave or Brownian motion to form a substantially uniform cover over the body of liquid.

Kirstie/keep/speci/Innovation P53899 02/08/04 7 The term "polygonal footprint" is used through out this specification to indicate that, in overall impression, each unit occupies substantially a single plane and has a plurality of sides and angles. However, it will be appreciated that portions of each unit may occupy more than one plane.

In the embodiment illustrated in Figures 1 to 4, each unit is shaped so as to be able to tessellate with one or more like units 12. As shown in figures 1 to 4 each unit 12 has an overall triangular footprint. More specifically, each unit 12 has three sides 13 each of equal length. In the second preferred embodiment illustrated in Figures 4 to 8, each unit 12 have a hexagonal footprint and each unit has six sides 13 of equal length.

It is to be understood that the floatable units of the present invention need not be triangular, although it is preferred that each unit has a polygonal footprint. The units could equally have a square, rectangular, octagonal, pentagonal or isosceles triangle shaped footprint, provided only that each unit is able to selfarrange relative to one or more like units.

Each unit 12 is substantially rigid in that the unit is able to move relative to or in response to the presence of one or more like units whilst maintaining its original shape. This feature allows the units 12 to be stacked for easy transport, handling and storage.

Each unit 12 must be able to float on the body of liquid 11. When each unit 12 is placed into the body of liquid 11, a first portion 16 of each unit 12 will be positioned above the water line and a second portion 18 of each unit 12 will be below the water line. The water line is marked in the Figures using reference numeral 20. The Kirstie/keep/speci/Innovation P53899 02/08/04 8 relative sizes of the first and second portions 16 and 18 respectively is a function of the buoyancy of each unit 12 and the relative density of the body of liquid 11.

To control the relative sizes of the first and second portions 16 and 18 respectively, the units 12 may be manufactured using materials selected to provide a desired degree of buoyancy given the specific gravity of the body of liquid 11 to be covered. When the liquid is water, the specific gravity is in the order of 1.0. Thus for water, the buoyancy of the unit would need to be at least less than 1.0 in order for the unit 12 to float on the body of water 11.

Appropriate materials which may be used to provide buoyancy to each unit includes: foam, polystyrene, polyvinyl chloride, vacuum plated cardboard, plastic coated wood, cork, silicone coated cardboard, kapok, air, polyethylene and combinations of these materials. However, it will be appreciated that other materials may also be suitable.

In the preferred embodiments, each unit comprises a hollow frame 15 typically manufactured using rotation moulding or any other suitable technique. For longevity, the material should also be UV stable so as to delay degradation of the material by the sun. Typically air is present inside the hollow frame 15. However, the use of a hollow frame 15 allows for the ballast of each unit 12 to be adjustable by adding or removing a quantity of buoyancy-imparting material 14 to the hollow frame 15 if required. This allows for the relative sizes of the first portion 16 and second portion 18 to be adjustable.

The buoyancy of the units should also be set to account for the maximum anticipated weight of salt and/or other debris that may accumulate on the upper surface 28 of the plate 22. In the embodiment where the cover system 10 is Kirstie/keep/speci/Innovation P53899 02/08/04 9 used to reduce the evaporation from a body of liquid, the buoyancy should be such that, under normal operating conditions, a portion of the unit remains at all times above the water line.

In the embodiment illustrated in Figures 1 to 4, the hollow frame 15 has a circular cross-section similar to a tube or pipe. In the second preferred embodiment illustrated in Figures 5 to 8, the hollow frame 15 has a square cross-section, as best seen in Figure 7. Other shapes for the cross-section of the hollow frame are equally applicable. Moreover, it is to be understood that the frame need not be hollow provided only that the buoyancy of each floatable unit 12 is sufficient to allow the unit 12 to float on the body of liquid 11.

Each of the floatable units 12 further comprises a plate 22 having an upper surface 28. In each of the illustrated embodiments, the plate is supported and delimited by the hollow frame 15. In this way, the hollow frame 15 serves the function of a flotation aid for the plate 22. In alternate embodiments, the plate 22 may extend outwardly beyond the hollow frame 15 and need not be planar. The overall buoyancy of each unit 12 may be adjusted in the manner described above to set the position of the plate 22 relative to the water line 20 so as to control the size of the pool of liquid 27.

The plate 22 is further provided with one or more holes 26 to regulate the size of a pool of liquid 27 that forms on the upper surface 28 of the plate 22. The holes allow for flushing of any solids that would otherwise accumulate on the upper surface 28 of the plate 22 such as salt, algae or other debris. The holes 26 also allow each of the floatable units 12 to remain buoyant even after, for example, rainfall. The rainwater drains through the. holes 26 in the plate 22 of each unit 12 as Kirstie/keep/speci/Innovation P53899 02/08/04 10 well as through gaps between units. The holes 26 are preferably evenly distributed across the plate 22 of each cover unit 12, but may equally be arranged in a random distribution.

In the embodiments illustrated in Figures 1 to 4, the plate 22 is positioned midway relative to the width D of the floatable unit 12. It is to be understood that the plate 22 may equally position at any height relative to the width D of the floatable unit 12 depending on the particular application of the cover system 10. In the second preferred embodiment of the present invention illustrated in Figures 5 to 8, the plate 22 is positioned at the base 32 of each hexagonally-shaped floatable unit 12. The advantage of positioning the plate midway relative to the width D of the floatable unit 12 is that each unit 12 may be thrown or otherwise tossed into the body of liquid 11 without regard to the position of the plate.

The use of cover system for reducing evaporation of a body of water, specifically a dam, is now described with reference to the embodiment illustrated in Figures 1 to 4.

In this example, only one designated area of the dam is to be covered, leaving the remainder of the surface of the dam uncovered. It is anticipated that a temperature differential will be developed between the covered designated area and the uncovered areas of the dam or lake, resulting in the artificial generation of currents between the two areas of differing temperature. This circulation of water may be advantageous for plant and fish life living in the lake or pond. The cover system could equally be used to cover the full surface area of the dam if desired.

With reference to Figure 4, a barrier 42 is placed to delineate the boundaries of the designated area of the dam Kirstie/keep/speci/Innovation P53899 02/08/04 11 to be covered. The banks of the dam itself also delineate part of the barrier of the designated area. A plurality of units 12 is then randomly tossed into the designated area.

In this embodiment, the plate 22 is positioned midway relative to the width of the frame 15 and thus the person throwing the units 12 into the dam 11 need not be concerned as to which way up the units 12 are placed into the dam 11.

Each unit 12 covers only a portion of the surface of the dam.

The position of each unit is fully self-adjustable relative to the presence of other like units, the barrier 42 and/or the banks of the dam as the units are not connected to each other. As more and more units 12 are added to the designated area, the units 12 start to bunch up against the barrier 42 to form a substantially contiguous planar cover as illustrated schematically in Figure 4.

The quantity of units 12 required to form the cover system 10 depends on the size and shape of the designated area.

The self-arranging characteristic of the units 12 means that the overall shape of the cover system 10 self-adjusts to suit the shape of the designated area.

Moreover it is anticipated that the water level in a dam may vary during the year in response to rainfall, evaporation, active drainage of the dam or any other cause of a change in water level. If the water level of the dam decreases, the floatable units 12 adjacent to the banks of the dam may end up resting on the banks. These units 12 automatically refloat and reposition themselves in the even that the water level of the dam subsequently increases. Similarly, if the water level increases, the units that have already been placed in the dam reposition themselves to maintain coverage over substantially the full surface of the dam as each unit may move independent of like units. Additional units may be added to the dam Kirstie/keep/speci/Innovation P53899 02/08/04 12 if the water level increases and such additional units will reposition themselves with the units that make up the existing cover system.

In this embodiment, the cover system 10 is being used simply to cover the dam so as to reduce evaporation.

Evaporation is reduced as a result of reducing the exposure of the surface of the dam to the effects of the sun and wind. Covering the surface of the dam in this way is also understood to reduce the harmful production of blue-green algae.

The cover system of the present invention may equally be put to a fundamentally different use, such as to actively encourage evaporation. This use will now be described with reference to the embodiment illustrated in Figures to 8, in which the cover system is used to encourage evaporation of a salt water pond as one step in the production of salt. Again, either the full surface of the salt water pond may be covered or simply one designated area. As above, a plurality of units 12 is placed into the salt water pond and the units are able to move freely relative to one or more like units to form the cover system. As above, sufficient units 12 are placed into the pond to form a substantially contiguous cover with the units self-arranging to suit the size and shape of the pond.

For this application, the plate 22 is positioned at the base X of the unit 12 and each unit is placed into the pond with the plate facing the surface of the water. The buoyancy of each unit is set such that the plate 22 rests below the water line 20. A pool of water forms on the upper surface of the plate 22 and the size of the pool of water remains substantially constant due to the presence of the plurality of holes 26 in each plate 22.

Kirstie/keep/speci/Innovation P53899 02/08/04 13 In this application, the upper surface of the plate 22 is provided with a heat absorbing layer 40 in the form of a simple layer of black paint, black plastic or other suitable material. The only proviso for the heat absorbing layer is that encourages heat to be absorbed so as to heat the pool of liquid with a view to encouraging evaporation or, in the best case scenario, boiling of the water. It is equally possible for the lower surface to also be provided with a heat absorbing layer (not shown).

As the water evaporates, salt is left behind on the upper surface of each plate 22. As more water enters the pool to replace the water that has been lost to evaporation, the salt is flushed out of the pool through these holes 26.

In this way, evaporation of the salt pond is encouraged.

As the level of salty water in the pond goes down, the units arranged around the perimeter of the pond will end up resting on the sides of the pond and the remaining units will continue to self-arrange to maintain coverage of the pond. When the water level has dropped sufficiently and time comes to drain the contents of the salt pond, the units can be removed and stacked ready for subsequent use. Alternatively, the units can be left in place in the pond while the contents are drained, with 'fresh' salt water added to the pond for evaporation.

When this fresh salt water is added, the cover will reestablish itself as the units re-float. The units may equally be floated from one pond to an adjacent pond.

Now that the preferred embodiments of the present invention have been described in detail, the present invention has a number of advantages over the prior art, including: the self-arranging characteristic of the units avoids the need to connect the units to each other at the time of installation and avoids the need to disconnect Kirstie/keep/speci/Innovation P53899 02/08/04 14 the units when the time comes to remove the cover system providing a significant saving in time and energy; the units block sunlight from the surface of the water, thereby decreasing the amount of algae that grows on the surface of the water; the units provide insulation from ambient air temperature to maintain a greater temperature in the body of covered water year round; if one area of the body of water is covered, this area will remain warmer than the remainder, generating artificial currents to increase circulation of the water in the body of liquid; and, evaporation is reduced as a result of the reduced effects of wind blowing across the surface of the body of the water.

Now that an embodiment of the present invention has been described in detail, it will be apparent to those skilled in the relevant arts that numerous modifications and variations may be made without departing from the basic inventive concepts. All such modifications and variations are deemed to be within the scope of the present invention the nature of which is to be determined from the above description.

Kirstie/keep/speci/Innovation P53899 02/08/04

Claims (4)

1. A cover system for a body of liquid comprising: a plurality of floatable units, each unit dimensioned to cover at least a portion of the body and able to move freely relative to one or more like units, wherein the plurality of floatable units are able to self-arrange to form a substantially uniform cover over at least a portion of the body of liquid.

2. A cover system as claimed in claim i, wherein each floatable unit has a variable buoyancy.

3. A cover system as claimed in either claim 1 or 2, wherein each unit comprises a plate oriented substantially parallel to the surface of the body of liquid.

4. A cover system as claimed in claim 3, wherein the plate comprises at least one hole to allow fluid communication between opposing sides of the plate. A cover system as claimed in any one of claims 1 to 4, further comprising a barrier which delineates a portion of the body of liquid to be covered from a portion of the body of liquid to be uncovered. Dated this 2nd day of August 2004 HAYDEN JOHN STEIN By His Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia. Kirstie/keep/speci/Innovation P53899 02/08/04