GB2466340A

GB2466340A - Laminated, gas filled sheet, for swimming pool cover

Info

Publication number: GB2466340A
Application number: GB0919590A
Authority: GB
Inventors: Anthony Peter Adlington
Original assignee: PLASTIPACK Ltd
Current assignee: PLASTIPACK Ltd
Priority date: 2008-11-07
Filing date: 2009-11-09
Publication date: 2010-06-23
Also published as: GB0919590D0

Abstract

The laminated sheet comprises an opaque layer which is shaped so as to trap air bubbles between it, and a dark or reflective layer, to which it is bonded. Preferably the dark or reflective layer comprises polyethylene containing black, dark blue or pale blue, weather resistant pigments, or a metallic, especially aluminium, foil. The air pockets are preferably formed in an array. When the sheet is placed over a swimming pool with the dark or reflective surface facing upwards, it can help the pool maintain a desired temperature (warm or cool) and prevent the growth of algae. The upper layer may have both reflective and dark sections.

Description

Material for Swimming Pool Cover The present invention relates to a material for swimming pool covers.

Conventional swimming pool covers typically reflect away incident solar radiation. In many countries, for example Britain, it is conventionally necessary to use heating systems to heat the pool water to a comfortable temperature. Other conventional swimming pool covers are typically arranged to use solar energy to heat up water underneath the pool cover. However, in some countries, for example, Dubai, the solar energy is such that pool water can become uncomfortably hot. Insome cases, it is conventionally necessary to use heat pumps to remove excess heat from the pool water.

Aspects of the above invention seek to overcome, reduce or balance the above problems.

According to a first aspect of the present invention, there is provided sheet material comprising an upper layer and a substantially opaque lower layer bonded to the upper layer, wherein the lower layer is shaped to trap air bubbles between the upper layer and the lower layer, and wherein the upper layer is reflective or substantially black.

An advantage of a substantially black upper layer is that the material absorbs solar energy.

An advantage of a reflective upper layer is that it reflects away solar energy.

Another advantage is that the lower layer blocks light from reaching the pool water, and thus reduces the growth of algae. This can reduce the quantity of chemicals (e.g. chlorine) needed to suppress algal growth.

The bubbles may be formed in an array similar to "Bubble Wrap" (RTM) packaging material. The bubbles are preferably formed on the underside of the swimming pool cover.

The bubbles provide the cover with buoyancy.

A preferred embodiment of the material with a reflective upper layer has a blue upper layer, preferably a pale blue upper layer. The blue layer preferably comprises a material (for example a white pigment) that scatters light. Thus the upper layer reflects the majority of incident solar energy, The opaque reflective blue colour provides reflective characteristics and reflects the sun's heat away from surface of a pool, and allows the water surface area directly under the cover to stay cool.

In other embodiments, the upper reflective layer is constructed by a white layer or a metallic foil, e.g. aluminium foil. However some pool owners find these alternatives too dazzling.

In some embodiments, the upper layer of the present invention reflects 90%, 99%, 999% or 99.99% or more of the solar energy.

In another preferred embodiment, the present invention has a dark blue upper layer (the term "substantially black" includes dark blue). The dark blue layer preferably comprises a material (for example a pigment) that scatters light, so that after repeated scattering within the upper layer the scattered light is absorbed by the upper layer. Thus this upper layer absorbs the majority of incident solar energy. In some embodiments, the upper layer of the present invention absorbs 90%, 99%, 99.9% or 99.99% or more of the solar energy.

In preferred embodiments, the lower layer may be substantially black. The lower layer is substantially opaque and in some embodiments, is arranged to block 90%, 99%, 99.9%, 99.99 or 99.999% or more of light, thus inhibiting the growth of algae or other photosynthetic microorganisms.

According to a second aspect of the present invention, there is provided a swimming pooi cover comprising sheet material according to the first aspect.

In preferred embodiments, the swimming pool cover is made of polyethylene. The bubbles may have a diameter of 1cm and a height of 4mm.

The pool cover is preferably made from a plastic comprising additives to stabilise the pool cover against degradation by ultraviolet (UV) light and/or against degradation by swimming pool chemicals (such as chlorine). For example, the pool cover may comprise a light stabilisation system on the basis of a synergistic mixture of monomeric and oligomeric hindered amine light stabilisers (HALS) with outstanding extraction resistance and low pigment interaction. In some embodiments, the additives combine weather resistance pigments with high performance light and weather stabilisation. In some embodiments, the additives used are non-toxic and registered in Australia, Canada, China, EU, Japan, Korea, Philippines and USA.

In some embodiments, one or more intermediate layers may be provided between the upper and lower layers, for example to improve the bonding between the upper and tower layers.

The use of additional layers also increases the rigidity of the material, which makes it easier to wind on to and unwind from a roller.

In a modification, a swimming pooi cover is provided in which the material at a first end of the cover has an upper layer which is reflective and the material at a second end of the cover has an upper layer which is substantially black in colour. The ratio of the areas of material at the first and second ends may lie within the range 1:3 to 3:1, preferably substantially 1:1.

According to a third aspect of the present invention, there is provided a swimming pool comprising a swimming pool cover according to the second aspect.

Benefits of a typical cover in accordance with the present invention are that it reduces algae growth, reduces filtration pump time, virtually eliminates water evaporation (98% +), reduces chemical consumption (3 5-60%), reduces energy consumption by over 50%, and/or reduces debris contamination.

By substantially cutting out the light that algae need for photosynthesis the cover of the present invention can prevent algal growth in outdoor and indoor swimming pools. In trials, the present invention has been shown to inhibit algal growth even without chemical treatment. Preventing algal growth is advantageous as harmful bacteria feed off algal waste and dead algae, so this risk of eye, ear skin and gut infections is also greatly reduced.

Algal growth in pools is also unsightly, spoiling the aesthetics of a pool, blocking filter systems and making surfaces slippery and dangerous.

As algal growth is substantially halted when a cover according to the present invention is on the pool the filtration time can be greatly reduced. Filtration is typically still needed to remove dirt (impurities) from the pool and to circulate the water but this could be cut by up to 50%. This can be achieved with regular use/bathing loads, but if there is heavy use of the pool there will need to be greater filtration. Preferably, at least one complete turnover of water through the pump system is achieved per day with or without use, (unless the pooi is out of use during the winter season.) Research carried out in collaboration with Brighton and London Metropolitan Universities indicate that the average loss per square metre of water surface are in the United Kingdom is in the region of 1,000 litres per year. For the average sized pool 4m x 8m, this adds up to a loss of around 32,000 litres per year.

With a pool cover according to the present invention one can virtually eliminate water evaporation, as it will reduce evaporation by over 98%, thus greatly reducing water consumption and one's water bill.

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a graph showing the light remission of different coloured plastic materials as a function of wavelength; and Figure 2 is a top schematic view of a swimming pool cover in accordance with an embodiment of the present invention.

Figure I shows the light remissions in percentage terms of sheets of plastic materials as a function of wavelength in nanometers in the visible range. The lines represent: A -A white material B -A pale blue material in accordance with embodiments of the present invention C -A dark blue material in accordance with embodiments of the present invention D -A black material.

The measurement was undertaken using a spectrophotometer in the visible light range.

It will be seen that the pale blue material approaches the performance of white material at wavelengths near the blue end of the spectrum but tails off towards the red end of the spectrum. Thus it has a light remission of between 40 and 82% towards the blue end of the visible spectrum, and of between 25 and 35% towards the red end of the spectrum.

It will also be seen that the dark blue material has a characteristic which is close to the performance of black material throughout the visible range. Thus it has a light remission of between 5 and 15% throughout the visible spectrum.

Embodiments of the present invention can help reduce chemical losses by evaporation.

With the present invention one can also use less chlorine, as algal growth will be prevented by physical means rather than chemical means. Chemical loss by evaporation is also reduced by a key attribute of the present invention is that chemical degradation by photolysis is reduced. Hypochlorite undergoes rapid photolysis in the presence of UV light from sunlight. About 90% of chlorine consumed by outdoor pools is lost due to photolysis reaction. Algae remove CO2 from the water as they undergo photosynthesis which causes the pH of water to increase. By preventing algae growth the present invention can maintain a more stable pH which will help maintain the correct chlorine equilibrium. The present invention can also reduce the need to use pH plus/pH minus to correct pH imbalance, thus savings of around 35-60% can be expected.

Some embodiments of the present invention have an upper layer with an opaque dark blue colour. This allows the sun's heat to warm the dark blue surface of embodiments of the present invention. This energy is then absorbed into the water surface area directly under the cover. The upper layer may be actually black in colour, but this is not as visually acceptable as dark blue.

The principle source of heat loss in a pool is evaporation, through the surface area, although some is lost by radiation and some by conduction. A cover according to the present invention can substantially eliminate evaporation and greatly reduce radiation. A series of water retention tests carried out in collaboration with the Universities of Brighton and London Metropolitan Universities, showed conclusive energy savings of over 50%.

Whether using an oil, gas, electric heater or heat pump, the present invention can make a huge saving covering a pool, if using solar heating one can half the amount of panel needed.

Debris such as leaves, dirt, insects and bird droppings are not only unsightly in a pool but also provide nutrients for algae and bacteria to feed on. When the pool is covered these contaminants will be kept out of the water greatly improving the quality and appearance of the water.

By reducing the amount of energy needed to heat and filter pool water the present invention can greatly reduce a CO2 footprint. It conserves water, a valuable resource that unlike oil and gas we cannot live without, and reduces the amount of harmful chemicals released into the environment.

Furthermore polyethylene is 100% recyclable and can be turned into other useful products.

This use of recycled product has an enormous impact on the environment; independent studies show that products made form recycled rather than virgin polythene results in a reduction of energy consumption by two thirds, production of only one-third of sulphur dioxide and half of the nitrous oxide and a reduction of water usage by 90%. It is estimated that 1.8 tonnes of oil are saved for every tonne of recycled polythene produced (British Polythene Industries).

With an open pooi or a pooi with a standard transparent solar cover light penetrates the water and allows algae to photosynthesise and grow. A dark blue or black cover substantially inhibits algal growth by preventing light from entering the water therefore stopping photosynthesis.

As an example, pools were compared having a standard solar gain cover and a cover according to the present invention with a black upper layer. The pools were both left for ten days with no chemical treatment, no filtration and with simulated use. The first pool with a standard solar gain cover soon went green due to algal growth. The second pool with a cover according to the present invention, had substantially no algal growth. This pool remained clear of algae for over two months until the test was ceased. A reflective cover in accordance with the invention would demonstrate a similar improvement.

A cover 10 according to an embodiment of the present invention is shown in Figure 2 and has a first area 12 at one end with a substantially black upper layer and a second area 14 at the other end with a reflective upper layer. The two sheets are joined together along an edge 16 to form a single sheet which can be rolled from and back on to rollers at one or both of the short ends 18 of the sheet.

This allows the pool owner to take into account different temperature conditions. For example, where the total cover length is substantially twice the length of the pool with the dividing line 16 between the first and second areas in the middle, the reflective layer 14 may be fully deployed at certain times of the year, or in certain weather conditions, when too much heat absorption is a problem, and the substantially black layer 12 may be fully deployed at other times, when an additional heating of the pool is required. In intermediate conditions, part of each area may be deployed, with the dividing line being located at a variable position along the pool. The cover may be less than twice the length of the pool.

For example if the length "L" of each area is three quarters of the length of the pool, then the ratio of the deployed areas can be varied between 1:3 and 3:1 depending upon the prevailing temperature conditions.

A modification of cover 10 has a common lower layer, with an upper reflective layer being applied to the left-hand part in Figure, and a substantially black layer being applied to the right-hand part of the lower layer.

In all embodiments of the invention, the bubbles may be of any convenient shape, e.g. part spherical, cylindrical etc. They may be arranged in an array having any desired pattern. A preferred size has a diameter of 1cm and a height of 4mm, but any convenient dimensions may be selected.

Claims

CLAIMSI. Sheet material comprising an upper layer and a substantially opaque lower layer bonded to the upper layer, wherein the lower layer is shaped to trap air bubbles between the upper layer and the lower layer, and wherein the upper layer is reflective or substantially black.
2. Sheet material according to claim 1, wherein the bubbles are formed in an array.
3. Sheet material according to claim I or2, wherein the bubbles are formed on the underside of the material.
4. Sheet material according to any preceding claim, wherein one or more intermediate layers are provided between the upper and lower layers.
5. Sheet material according to any preceding claim made of polythene.
6. Sheet material according to any preceding claim, wherein the bubbles have a diameter of 1cm and a height of 4mm.
7. Sheet material according to any preceding claim, wherein the upper layer is reflective and is pale blue in colour.
8. Sheet material according to claim 7 and having a light remission of between 40 and 82% towards the blue end of the visible spectrum, and of between 25 and 35% towards the red end of the spectrum.
9. Sheet material according to any of claims I to 6, wherein the upper layer is reflective and comprises a metallic foil.
10. Sheet material according to claim 9, wherein the metallic foil is aluminium foil.
11. Sheet material according to any of claims I to 6, wherein the upper layer is substantially black and, more particularly, is dark blue in colour.
12. Sheet material according to claim 1] and having a light remission of between 5 and 15% throughout the visible spectrum.
13. Sheet material substantially as herein described.
14. A swimming pool cover comprising sheet material according to any preceding claim.
15. A swimming pool cover according to claim 14, and made from a plastic material comprising weather-resistant pigments.
16. A swimming pooi cover comprising sheet material according to claim 14 or 15, wherein the material at a first end of the cover has an upper layer which is reflective and the material at a second end of the cover has an upper layer which is substantially black in colour.
17. A swimming pool cover according to claim 16, wherein the ratio of the areas of material at the first and second ends lies within the range 1:3 to 3:1.
18. A swimming pool cover according to claim 17, wherein the ratio is substantially 1:1.
19. A swimming pool cover comprising a pale blue upper layer bonded to a substantially opaque lower layer, wherein the lower layer is shaped to trap air bubbles between the upper layer and the lower layer, wherein the bubbles have a diameter of 1cm and a height of 4mm and are formed in an array.
20. A swimming pool cover comprising a dark blue upper layer bonded to a substantially opaque lower layer, wherein the lower layer is shaped to trap air bubbles between the upper layer and the lower layer, wherein the bubbles have a diameter of 1cm and a height of 4mm and are formed in an array.
21. A swimming pool cover substantially as herein described.
22. A swimming pooi comprising a swimming pool cover according to any of claims 14 to 21.