AU2003268848A1 - Evaporation inhibiting device and method - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): ALAN BRUCE WOODING LUCIANO PAPI RONALD GRAHAM DORAN Invention Title: EVAPORATION INHIBITING DEVICE AND METHOD The following statement is a full description of this invention, including the best method of performing it known to me/us: -2- EVAPORATION INHIBITING DEVICE AND METHOD The present invention relates to an evaporation inhibiting device and method, and particularly an evaporation inhibiting device and method for reducing the evaporation rate of an underlying body of liquid.

Regional areas are greatly dependent on natural rainfall as their main water source, in particular for agricultural irrigation, but also for domestic consumption. The rainfall must be stored in specially constructed or natural reservoirs so that it can be accumulated for use, particularly throughout drier periods. As the amount of water in these reservoirs is determined by natural rainfall patterns, levels vary dramatically between seasons resulting in an unreliable water source.

Water levels are also severely reduced by the apparently increasing effects of solar radiation due to global warming, which are significantly increasing evaporation rates which results in increasing salinity. In areas where water from rainfall is such an essential commodity and in particular since limitations are often placed on the size and number of the reservoirs, there is a great need for the use of new methods which will reduce the effect of evaporation so that the stockpiled levels remain at their peak.

US 3,938,338 discloses a float member for use in conjunction with similar float members for blanketing or covering the surface of a liquid to reduce evaporation. The float member comprises a body which is similar to a shaped small ball and has a hexagonal circumferential skirt at least 5mm in depth and which floats with its hexagonal skirt disposed at the level of the liquid. Multiple such float members can be used on the surface of bodies of water such as swimming pools, and due to the hexagonal shape of the float members, the float members tessellate to cover the entire surface of the liquid. Furthermore, the shape of the float members inhibit rotation in the fluid exposing freshly wetted surfaces, from which water can evaporate.

According to the present invention, an evaporation inhibiting device comprises a buoyant polygonal member having opposite first and second major surfaces and a polygonal peripheral portion.

3 5 Preferably, the device is formed from moulded polyolefin thermoplastic, preferably in combination with an endothermic or exothermic blowing agent. The device thus formed will have a smooth surface skin with an internal fine cell structured -3foam. The device will have low weight without any sinks manifest in thick sections.

The cost of tooling is low because the internal pressure required is low. Complete filling of the mould results from the pressure generated inside the mould once the reaction between the polyolefin and the blowing agent has begun. The product will be free of internal stresses and will therefore remain straight and dimensionally stable.

Preferably, the polyolefin is blended with light reflective particles, more preferably aluminium particles. Agricultural products usually use carbon black to stabilise resins against the effects of UV exposure. Carbon black may be used as an additive in the present invention, on a cost basis. However, this renders the resin absorbent to light and heat or sunlight. The reflective particles, preferably aluminium particles, reflect the heat and thereby reduce heating of the device and the underlying body of water. Preferably the polyolefm also includes THT, a UV stabilizer additive.

This additive will provide further UV protection. Preferably, the aluminium is added in a proportion of The THT is preferably added at a rate of between 0.5 and 0.75%.

The device may alternatively be composed of a hydrophobic, particulate material such as a fly-ash based material.

Preferably, the device includes a plurality of vertical projections around its periphery. The projections prevent adjacent floating devices from overlapping.

Preferably, the projections extend vertically from both of the major surfaces, at the same positions. Preferably, the projections are located at corners of the polygonal peripheral portion. Preferably, each projection from the first major surface includes either a stacking projection or a stacking recess, and the corresponding projection from the second major surface includes a mating stacking recess or stacking projection, respectively. Thus, when stacked, stacking projections engage in stacking recesses on an adjacent device.

Preferably, the ratio of the maximum height of the device to the maximum width of the device is at least 1:10 and more preferably at least 1:15.

Preferably, the device has a surface area of at least 0.3m 2 more preferably at 2 least 0.5m 2 Preferably, each device is at least 30cm in diameter, more preferably at least -4 in diameter.

Preferably, the device includes means for attaching the device to an adjacent device. Preferably, the device includes at least one hole passing through the device from its uppermost to its lowermost surface. The holes allow adjacent devices to be linked together by straps or ties.

Preferably, the device includes a plurality of projections extending outwardly from the periphery of the device. These hold adjacent devices slightly spaced from each other when they are floating in a body of water, so that some light permeates to the water below. This is ecologically desirable, to allow light to reach plants and algae growing in the water.

In one embodiment, the device includes a central chamber and an outwardly extending skirt portion. A weight may be included in the central chamber. Weighting the device may be required to prevent wind from lifting the device.

Preferably, the device is generally symmetrical about a central plane parallel to the first and second major surfaces, so that it can be oriented with either of its opposite major surfaces facing upwardly.

In an alternative embodiment, the device includes a downwardly depending skirt portion defining at least one chamber which, in use, traps water under the skirt which then acts as a ballast to prevent the device from being blown from the surface of the reservoir. The underside of the device may also include a layer of foam material.

Accordingly to a seconid aspect of the invention, a method for inhibiting evaporation from a water reservoir comprises, providing a plurality of evaporation inhibiting devices as set out above, arranged to float on the surface of the water in substantially abutting side by side relationship to substantially cover the surface area of the water.

Embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a plan view of an evaporation inhibiting device; Figure 2 shows a sectional side view of the evaporation inhibiting device taken along line I-I in Figure 1; Figure 2A shows an enlarged view of part of the evaporation inhibiting device of Figure 2; Figure 3 shows a plan view of a further embodiment of an evaporation inhibiting device; Figure 3A shows an enlarged side view of a portion of the evaporation inhibiting device of Figure 3; Figure 3B shows an enlarged plan view of a portion of the evaporation inhibiting device of Figure 3; Figure 4 shows a sectional side view of the evaporation inhibiting device taken along line II-II in Figure 3; Figure 4A shows an enlarged view of a part of the evaporation inhibiting device of Figure 4; Figure 4B shows an enlarged view of a part of the evaporation inhibiting device of Figure 4; Figure 5 shows a plan view of another embodiment of an evaporation inhibiting device; and Figure 6 shows a cross-sectional side view of the evaporation inhibiting device of Figure 2 0 Referring initially to Figures 1 and 2 of the drawings, a first embodiment of an evaporation inhibiting device is illustrated and is generally designated by reference numeral 1.

The device includes a central portion 2 defining a cavity 3 being circular in plan view and a peripheral or skirt portion 4 defining a hexagonal outline. The central portion 2 is integrally formed with the skirt portion 4 so that the device includes continuous opposite major surfaces 16,17. The skirt portion 4 includes six fins 5 which project from both major surfaces 16,17 at the corners of the hexagonal skirt 4. A plurality of holes 6 are provided, one in the centre of each edge of the skirt 4. A weight may be included inside cavity 3, to help prevent the device 1 from being blown away by wind.

Holes 7, 8 are formed through the polyolefin by metal pins protruding from the mould "floor" which support a cement ballast weight in position, centrally, during the moulding process.

The device is dimensioned to have an area of each major surface is approximately 1 inm 2 The dimension A is approximately 1240 mm, whereas dimension B is 1075 mm. The maximum height Cof the device 1 excluding the projection 23, is 64 mm.

Figures 3 and 4 show a further embodiment of an evaporation inhibiting device 1. Unlike the embodiment of Figures 1 and 2, this embodiment does not include a central cavity, but has a central peg 22 projecting from both major surfaces 16, 17 and surrounded by a hexagonal skirt 4. The dimensions A and B are the same as the embodiment of Figures 1 and 2, so that the surface area is also approximately 1m 2 The dimension C',being the maximum height of the device 1. The embodiment of Figures 3 and 4 also includes fins 5 projecting from opposite major surfaces 16, 17, and holes 6 provided centrally located along each edge of skirt 4. In this embodiment, each fin includes a projection 23 at the extremity of the portion of the fin 5 which projects from the first major surface 16, and a mating recess 24 at the extremity of the portion of the fin 5 which projects from the second major surface 17. When a plurality of devices are stacked, the projections 23 on one device engage in recesses 24 on an over or underlying device, thus facilitating stacking of devices. This embodiment additionally includes projections 25 extending laterally from each edge of the skirt 4.

In use, a plurality of the devices 1 are placed on the surface of the body of liquid, particularly water contained in a dam or reservoir. As the device is generally symmetrical about a centre plane, either of the major surfaces may face upwardly. Due to their buoyancy, the devices are partially submerged with the upper surface of each device 1 lying just above the water surface. The hexagonal shape of the devices 1 facilitates the tessellation of the devices 1 to form a covering system that is substantially continuous and therefore can almost entirely cover the liquid surface if required. The fins 5 prevent adjacent devices from overlapping when a plurality of devices 1 are floating on the surface of a body of water. The holes 6 are provided so that adjacent devices 1 may be attached together by cable ties or plastic straps. Linking the devices 1 helps to prevent the devices from being blown away in high wind conditions. In the embodiment of Figures 3 and 4, the edge projections 25 maintain a small gap between adjacent floating devices, either when linked or when free floating. This ensures that some light permeates to the water below.

In the embodiment of Figures 1 to 4, the device 1 is formed from a weather resistant, plastics material. The device is formed using a low pressure injection moulding process. The device 1 is moulded in polyolefin thermoplastic in combination -7with endothermic or exothermic blowing agents, which results in a device having a smooth surface skin with an internal fine cell structured foam. The polyolefin includes two additives to provide a life expectancy of the device of over 20 years on each exposed side. The choice of additive is dictated by the requirement that the device reflect rather than absorb the light and heat of sunlight. The UV protection is preferably based on a blend of aluminium particles and THT. The rate of addition of the aluminium is between 1% and and the THT is added in an amount of 0.5-0.75%.

The aluminium can be provided in three particle sizes, 6-8 microns, 12-14 microns and 14-16 microns. The size of the particles control the final appearance of the product. The greater the particle size, the greater the reflective capacity. By reflecting the sunlight, the aluminium particles reduce the heat build-up in the material. This slows the rate of temperature rise of the water which will both reduce evaporation even further and will deter the build-up of algae.

Preliminary tests carried out using a 20mm thick piece of foam backed LDPE two-thirds immersed in water have shown that placed in full sun with a shade temperature of 34*C for 4 hours, the temperature of the upper exposed surface was 37.8 0 C and the lower surface temperature was 29.3 0 C. The trial sample did not contain aluminium particles, which further increases the temperature reduction effect.

Referring to Figures 4 and 5, a second embodiment of an evaporation inhibiting device 1 is shown.

In this embodiment, a hexagonal body portion 10 has a downwardly depending skirt 11 which defines a chamber 12 on the underside of the device 1. A layer of foam material 13 may be included on the underside of the body portion 10 for buoyancy. A 3mm hole 14 is included in the centre of the device. The hole 14 allows air to escape from the chamber so the device can settle on the water until the layer of foam provides buoyancy. The water in the chamber now acts as a ballast weight to prevent the device being blown off the reservoir by wind gusts. This is because air can only enter slowly through the 3mm hole to displace the trapped water from the chamber, and by the time the gust has lifted the device a short way the gust may be exhausted, and the device settles back on the water.

The periphery of the body portion 10 includes a stepped portion 15 to enable stacking of devices for transport. The dimensions A and B of the device are the same as .8 for the first embodiment. The depth C of the device is approximately 90 mm, the depth -of the foam layer 13 being 40 mm. The use of this embodiment is the same as that described above with reference to the first embodiment.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects of illustrative and not restrictive.

In the claims which follow and in the preceding description of the invention, 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.

It is to be understood that a reference herein to a prior art publication does not constitute an admission that the publication forms a part of the common general knowledge in the art in Australia, or any other country.

Claims (20)

1. An evaporation inhibiting device comprises a buoyant polygonal member having opposite first and second major surfaces and a polygonal peripheral portion.

2. A device according to claim 1, which is formed from moulded polyolefin thermoplastic.

3. A device according to claim 2, wherein the device is moulded from polyolefin in combination with an endothermic or exothermic blowing agent.

4. A device according to claim 2 or 3, wherein the polyolefin is blended with light reflective particles. A device according to claim 4, wherein the light reflective particles are aluminium particles.

6. A device according to claim 5, wherein the aluminium is added in a proportion of

7. A device according to any one of claims 2 to 5, wherein the polyolefin also includes THT.

8. A device according to claim 7, wherein the THT is included in a proportion of between 0.5 and 0.75%.

9. A device according to any one of the preceding claims, including a plurality of projections extending vertically from the periphery of at least one of the major surfaces.

10. A device according to claim 9, wherein the projections extend vertically from both of the major surfaces.

11. A device according to claim 10 wherein each projection from the first major surface includes either a stacking projection or a stacking recess, and wherein the corresponding projection from the second major surface includes a mating stacking recess or stacking projection, respectively.

12. A device according to claim 10 or 11, wherein the projections are located at corners of the polygonal peripheral portion. 10

13. A device according to any one of the preceding claims, wherein the ratio of the maximum height of the device to the maximum diameter of the device is at least 1:10

14. A device according to any one of the preceding claims, wherein the ratio of the maximum height of the device to the maximum width of the device is at least 1:15. A device according to any one of the preceding claims, having a surface area of at least 0.3 square metres.

16. A device according to claim 15, having a surface area of at least 0.5 square metres.

17. A device according to any one of the preceding claims, wherein the diameter of the device is at least

18. A device according to any one of the preceding claims, wherein the diameter of the device is at least

19. A device according to any one of the preceding claims, including means for attaching the device to an adjacent device. A device according to any one of the preceding claims, including at least one hole adjacent the periphery of the device and passing through the device from the first to the second major surface.

21. A device according to any one of the preceding claims, including a central chamber and an outwardly extending peripheral portion. 3 0 22. A device according to claim 21, including a weight located in the central chamber.

23. A device according to any one of the preceding claims, including a plurality of projections extending outwardly from the periphery of the device.

24. A method for inhibiting evaporation from a water reservoir comprises, providing a plurality of evaporation inhibiting devices according to any one of claims 1 11 to 23, arranged to float on the surface of the water in a substantially abutting side by side relationship to substantially cover the surface area of the water. An evaporation inhibiting device, substantially as herein described with reference to, or as shown in, the accompanying drawings. Dated this 12th day of December 2003 ALAN BRUCE WOODING, LUCIANO PAPI and RONALD GRAHAM DORAN By their Patent Attorneys GRIFFITH HACK