GB2408320A

GB2408320A - Inflatable solar heat collector panel

Info

Publication number: GB2408320A
Application number: GB0327239A
Authority: GB
Inventors: Stephen Knowles
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-11-22
Filing date: 2003-11-22
Publication date: 2005-05-25
Also published as: GB0327239D0

Abstract

An inflatable solar heat collector panel 1 has four overlying sheets of material of which two are inner sheets 2a,2b joined to one another along an array of join lines 3 and two are outer sheets 7a,7b joined to the inner sheets at selected join lines 3'. The conjoined inner sheets define an array of tubular conduits 4 for a heat exchange fluid, and the inner sheet and outer sheet together define an array of inflation pockets 9 which when inflated impart longitudinal rigidity to the solar panel. The upper of the outer sheets is made from a material substantially transparent to solar energy and at least an upper one of the inner sheets is made from a material that has a high absorptivity for solar energy. The panel may also include inlet and outlet plenum chambers (5 and 6 fig 1), which facilitate supply and return of heat exchange fluid. The panel may include eyelets secured to the border portion for anchorage of the panel, or a further sheet may be added to receive ballast material. The inflation pockets may be connected through a single valve, and the sheets may be joined by thermal welding, cold welding or a suitable adhesive.

Description

TITLE

Inflatable solar heat collector panels

DE SCRIPT ION

Technical Field

The invention provides an inflatable solar heat collector panel that is cheap to produce, lightweight and easy to use. The panel can be stored in a collapsed state and inflated in situ. When inflated, the thermal efficiency of the solar panel is comparable to more conventional rigid solar heat collector panels.

Bakound Inflatable solar heat collector panels are known but they have never been commercially acceptable because they are expensive to manufacture and difficult to use.

French Patent Application 2539493 describes an inflatable solar heat collector panel that is adapted for heating and insulating swimming pools. The panel consists of a series of fluid channels defined by two flexible plastic sheets. A third transparent plastic sheet is joined to the flexible plastic sheets around its periphery to form an inflation pocket. The panel is not provided with any insulation below the fluid channels in use and it is not thermally efficient unless placed directly on water.

Moreover, the panel does not have any structural rigidity.

The pressure of the air in the inflation pocket is only sufficient to lift the transparent plastic sheet off the flexible plastic sheets below. In practice, this will mean that the fluid channels are substantially circular in cross-section. The thermal efficiency of the panel is therefore reduced because there is a relative large difference in the temperature of the heat exchange fluid at the centre and at the edges of each fluid channel. The pressure of the air in the inflation pocket cannot be increased to flatten out the fluid channels because this would cause the whole panel to take on a circular cross-sechon.

United States Patent 4328790 describes an inflatable solar heat collector panel that is constructed from six interconnected flexible plastic sheets. The inner two sheets are joined to one another along spaced join lines to define an array of fluid channels. An array of inner and outer inflation pockets are provided above and below the fluid channels. The panel is constructed in such a way that the fluid channels have approximately the same cross-sectional area as the inner and outer inflation pockets.

They also have a low ratio of surface area to volume. This will result in a relatively large difference in the temperature of the heat exchange fluid at the top and bottom each fluid channel. As with French Patent Application 2539493, this temperature 0 gradient will reduce the thermal efficiency of the panel for a given outlet fluid temperature.

United States Patent 4151830 describes a solar heat collector panel that has an extremely complicated construction. A pair of timer sheets are joined together to define a continuous serpentine fluid channel for receiving a heat exchange fluid. At least one outer sheet defines an inflation pocket but this does not provide structural rigidity to the panel. In fact structural rigidity is maintained by a number of ribs that are attached to the outer surface of the panel.

Summary of Me Invention

The invention provides an inflatable solar heat collector panel comprising four overlying sheets of material of which two are inner sheets joined to one another along an array of join lines to define, between the conjoined timer sheets, an array of tubular conduits for a heat exchange fluid, and the other two are outer sheets joined to the inner sheets along join lines which follow the lines of selected mutually spaced join lines of the inner sheets to define, between the conjoined imer and outer sheets, an array of inflation pockets which, when inflated, impart a degree of longitudinal rigidity to the solar heat collector panel; wherein at least an upper one of the outer sheets is made from a material substantially transparent to solar energy and at least an upper one of the inner sheets is made from a material that has a high absorptivity for solar energy. - 3

Compared to prior art inflatable solar heat collector panels, the invention has a simple and elegant construction that is cheap to produce, lightweight and easy to use. An important technical feature of the invention is that the two outer sheets are joined to the inner sheets along join lines that follow the lines of selected mutually spaced join lines of the inner sheets, i.e. at certain points along the solar heat collector panel, the join lines between the inner sheets and the join lines between the inner and outer sheets coincide with each other. This construction gives the panel the required degree of longitudinal rigidity when the inflation pockets are inflated. In addition this construction is well adapted to be easily compatible with plastic sheet welding processes and machines for rapid, low-cost manufacture.

The solar heat collector panel has an array of inflation pockets on both sides of the tubular conduits. This means that the shape of the panel does not substantially alter as the pressure inside the inflation pockets is increased. When inflated, the array of inflation pockets insulate the tubular conduits from the cooler air outside the panel' Providing an array of inflation pockets reduces the heat losses by convection when compared to a single inflation pocket described in French Patent Application 2539493. Moreover, the panel is constructed so that the tubular conduits are held in tension by the pressure of the inflation pockets and have a high ratio of surface area to volume. The solar heat collector panel according to the present invention is therefore thermally efficient, transferring heat between the hot solar energy absorbing sheet and the fluid with minimal temperature difference.

The inner sheets can be joined to one another at opposite ends thereof along join lines which extend generally transversely to the array of tubular conduits to define, between the conjoined inner sheets, inlet and outlet plenum chambers for the tubular conduits for supplying the heat exchange fluid to and withdrawing it from the solar heat collector panel. The parallel tubular conduits can be made such that each one has a crosssectional area far smaller than that of the plenum chambers in order to encourage uniform fluid flow across the panel.

The width of the part of the outer sheet forming each individual inflation pocket is preferably at least O.S times greater than the linear distance between the selected mutually spaced join lines.

The sheets can be joined to one another by thermal welding, sonic welding, cold welding (i.e. using a chemical solvent) or an adhesive that is compatible with both materials being joined, for example.

The inflation pockets can be interconnected one with another so that the forced introduction of air into the inflation pockets through a single inflation valve, or through dual inflation valves one above and the other below the conjoined inner sheets, is sufficient to inflate all inflation pockets of the panel.

The inflatable solar heat collector panel can further comprise a continuous border portion of the overlying sheets around the whole of the periphery of the panel, with eyelets secured to the border portion for anchorage of the inflated panel.

A fifth sheet can be provided that underlies the panel and is secured thereto around its periphery to define an anchorage pocket beneath the inflated pocket to receive a ballast material such as sand to anchor the inflated panel to the ground.

The solar heat collector panel can further comprise a transparent sheet lying between the outer sheet and the inner sheets of the panel and fixed at additional and/or the common join lines to define one or more intermediate chambers acting to contain the air and thereby reduce convection currents and consequent heat losses.

Drawings Figure 1 is perspective view showing an array of tubular conduits for a heat exchange fluid and inlet and outlet plenum chambers which form part of an inflatable solar heat collector panel according to the present invention; Figure 2 is a perspective view showing an inflatable solar heat collector panel according to the present invention; and - s - Figure 3 is a cross-sectional view of the inflatable solar heat collector panel of Figure 2.

With reference to Figures I to 3, an inflatable solar heat collector panel l is formed from four overlying flexible plastic sheets. Two inner sheets 2a and 2b are thermally welded to one another along an array of join lines 3 to define an array of tubular conduits 4 for receiving a heat exchange fluid such as water. The inner sheets 2a and 2b are also thermally welded to one another at opposite ends of the panel 1 to define an inlet plenum chamber S for supplying the heat exchange fluid to the tubular conduits 4 and an outlet plenum chamber 6 for withdrawing the heat exchange fluid from the tubular conduits 4. The inner sheet 2a that forms the upper surface of the tubular conduits 4 in use is made of a material having a high level of solar energy absorptivity and ideally a low value of transmissivity. The material should also be as thin as possible in order to maximise the heat transfer to the heat exchange fluid and minimise heat loss by conduction. The tubular conduits 4 contain a thin film of heat exchange fluid and have a high ratio of surface area to volume. This means mat the panel l is thermally efficient.

Two outer sheets 7a and 7b are thermally welded to the inner sheets 2a and 2b along join lines 8 that follow the lines of selected mutually spaced join lines 3, of the inner sheets 2a and 2b to define an array of inflation pockets 9. The solar heat collector panel l is provided with a single inflation valve (not shown) that allows all of the inflation pockets 9 to be inflated with air to the required pressure. The inflation valve (not shown) can be of a conventional kind but should be able to keep the panel 1 in the inflated state for at least six months. When inflated, the inflation pockets 9 provide the panel I with a degree of longitudinal rigidity.

The outer sheet 7a that forms the upper surface of the solar heat collector panel 1 is made of a material that is substantially transparent to solar energy.

To improve the insulation of the tubular conduits 4, the solar heat collector panel 1 is constructed so that the adjacent inflation pockets 9 are in contact with each other along contact lines 1 Oa and 10b for a significant extent above and below the inner sheets 2a and 2b. This is achieved by making sure that the width of the outer sheet forming each individual inflation pocket 9 is always at least 0.5 times (preferably significantly more than 0.6 times) greater than the linear distance between adjacent join lines 8. The contact lines lea and lob act to prevent the relatively hot inner sheets 2a and 2b being in contact with the colder outside air and thus reduce heat energy losses.

The solar heat collector panel 1 can be stored in its deflated state. It is lightweight and can be easily transported. To use the panel, the inflation pockets 9 are inflated using the inflation valve (not shown). An inlet pipe (not shownj is connected to the inlet plenum 5 and an outlet pipe (not shown) is connected to the outlet plenum 6 so that the panel 1 fortes part of a fluid circuit. Heat exchange fluid is pumped or gravity fed into the inlet plenum 5 and flows through the tubular conduits 4 where it is heated using solar energy. When the heat exchange fluid reaches the outlet plenum 6 it is withdrawn through the outlet pipe (not shown) and can be used for space heating, washing or as a multi- purpose domestic, industrial or agricultural hot water source.

Several solar heat collection panels I can be used in series such that the outlet pipe of one panel is connected to the inlet plenum 5 of another panel. Alternatively, depending upon the application, several solar heat collector panels I may be connected in parallel with each inlet plenum 5 connected to a common inlet feed pipe and each outlet plenum 6 connected to a common outlet pipe.

The inner sheets 2 and outer sheets 7 are thermally welded together around the periphery of the solar heat collector panel I to form a continuous border portion.

Eyelets (not shown) can be secured to the border portion to allow the panel I to be anchored to the ground using ropes or pegs. An additional sheet (not shown) can also be thermally welded to the underside of the panel I to form an array of pockets between the additional sheet and the outer sheet 7b. The array of pockets can be filled with sand, water or other material to act as a ballast weight to hold the panel 1 in place. The pockets can also be filled with an insulating material such as foam to reduce the heat losses through the underside of the panel 1.

The inflatable solar heat collector panel 1 can be used to heat the water in a swimming s pool. In this case the panel conveniently takes the form of a floating cover that acts as an insulating layer to retain the heat and prevent evaporation.

Claims

1. An inflatable solar heat collector panel comprising four overlying sheets of material of which two are inner sheets joined to one Another along, an array of join lines to define, between the conjoined inner sheets, an array of tubular conduits for a heat exchange fluid, and the other two are outer sheets joined to the inner sheets along join lines which follow the lines of selected mutually spaced join lines of the inner sheets to define, between the conjoined inner and outer sheets, an array of inflation pockets which, when inflated, impaIt a degree of longitudinal rigidity to the solar heat collector panel; wherein at least an upper one of the outer sheets is made from a Senatorial substantially transparent to solar energy and at least an upper one of the inner sheets is made Dam a material that has a high absorptivity for solar energy.

2. An inflatable solar heat collector panel according to claim 1, wherein at least the upper one of the outer sheets is joined to itself along join lines which are parallel to and closely spaced from the lines along which it is joined to the inner sheets.

3. An inflatable solar heat collector panel according to either preceding clann, wherein the inner sheets are joined to one another at opposite ends thereof along join lines which extend generally transversely to the array of tubular conduits to define, between tile conjoined inner sheets, inlet and outlet plenum chambers for the tubular conduits for supDl.g the heat excltange fluid to a,', ..iShrSra'x''n<'r If,m "lee SCAM heat collector panel. q

4. A.n inflatable solar heat collector panel according to any preceding claim, wherein the width of the part of the outer sheet ionrung each individual inflation pocket is at least 0.5 times greater than the linear distance between the selected mutually spaced join lines.

5. An inflatable solar heat collector panel according to any preceding claim, wherein the sheets are joined to one another by thennaJ welding.

6. An inflatable solar heat collector panel according to any of claims I to 4, wherein the sheets are joined to one another by chemical or solvent welding.

7. An inflatable solar heat collector panel according to any of claims 1 to 4, wherein the sheets are joined to one another by adhesive.

8. An inflatable solar heat collector panel according to any preceding claim, vvllerein the inflation pockets are interconnected one with another so that the forced introduction of air into the inflation pockets through a single inflation valve, or tlau dual inflation valves one above and the other below the conjoined isomer sheets, is sufficient to inflate all inflation pockets OT the par el.

9. An inflatable solar heat collector panel according to any preceding claim, further comprising a continuous border portion of the overlying sheets around the whole of the periphery of the panel, with eyelets secured to the border portion for anchorage of the inflated pane}.

10. An inflatable solar heat collector panel according to any preceding claim, further comprising a little sheet underlying the panel and secured thereto around its periphery to define an anchorage pocket- beneath the inhaled pocket to receive a ballast material such as sand to anchor the inflated panel to the ground.

11. An indatalle solar heat collector panel according to ally preceding claim, further comprising, a transparent sheet lying between the outer sheet and the ironer sheets of the pane! and fixed at additional and/or the common join lines to define one ! 1C' or more intermediate chambers acting to contain the air and thereby reduce convect.or, currents and consequent heat losses.

12. An inflatable solar heat collector panel substantially as herein described unto reference to the drawings. *