GB2468207A

GB2468207A - Solar thermal collector

Info

Publication number: GB2468207A
Application number: GB1003232A
Authority: GB
Inventors: Keith Wilkinson
Original assignee: SUNDWEL SOLAR Ltd
Current assignee: SUNDWEL SOLAR Ltd
Priority date: 2009-02-27
Filing date: 2010-02-25
Publication date: 2010-09-01
Also published as: GB0903385D0; GB201003232D0

Abstract

A solar thermal collector 2 comprises an outer panel 4 spaced apart from an inner panel 6, and one or more tubes 10, 12, 14 located in the space between the panels. The tubes contain a liquid and are arranged to allow the transfer of heat between the liquid and outer panel. A material 8 is inserted between the panels, where expansion of the material as it cures causes the tubes to be pressed and held against the outer panel by the material. Preferably, the material is isocyanurate or insulating foam, which expands to fill the space between the panels when it is cured, and bonds the panels together. At least one of the panels may be made from aluminium or copper, and the outer panel may be coated with black polyester or photovoltaic paint. Preferably, the liquid contained in the tubes is water and may include propylene glycol. The liquid may be circulated to a swimming pool or collected in a reservoir. Preferably, the panels form part of a roof panel, where a roof may be formed from a number of interconnected solar thermal collectors. In a further aspect, an apparatus for manufacturing a solar thermal collector is disclosed.

Description

Solar thermal collection device and method of manufacture The invention to which this application relates is a solar thermal collector, typically a solar collector for collecting heat by absorbing solar radiation.

Although the following description refers almost exclusively to a solar collector used in a roof, it will be appreciated by persons skilled in the art that the present invention can be used in walls and other structures.

The most common type of solar thermal collector is a flat plate, which is typically used as a solar hot water panel i.e. to heat water using solar energy. This type of collector usually comprises a weatherproofed insulated box with an absorber plate and a series of tubes attached to it for collecting the solar energy. The collector is placed in the path of the sun, typically on a roof, such that solar energy heats up liquid in the tubes.

This energy may then be transferred to a storage cylinder or swimming pooi. * * ** **

It may be desirable to incorporate a solar collector into a roof rather than placing a device on top of a roof for both cosmetic and practical reasons, as for example the device would be less * 25 susceptible to being blown over when embedded in a roof. ** * S

However, such solar collectors can be difficult to fit into roofs and connect together due to the number of connections typically found therein. In addition, it is difficult to manufacture large glass-fronted solar collectors as the glass is relatively fragile.

Furthermore, the tubes must be continuously connected to the absorber plate to ensure efficient heat transfer. However, methods such as ultrasonic or laser welding, or soldering are expensive and can restrict the size of the collectors being man u fa c tu red.

An aim of the present invention is to provide a solar thermal collector for a roof which is simple to manufacture and highly efficient.

In an aspect of the invention, there is provided a solar thermal collector comprising: an outer panel spaced apart from an inner panel, and one or more tubes located in the space between the panels; the tubes being suitable for containing liquid and arranged to allow the transfer of heat between the liquid and outer panel; wherein material is provided between the panels such that the tubes are held against the outer panel by the material substantially along their respective lengths.

Thus the collector can be fitted as a roof panel, as it is compatible with existing twin panel roof systems and may be coloured and/or configured to look similar in shape and/or size. * * ****

In one embodiment the material is insulating material, such as insulating foam. Typically the foam or other material expands as it cures thereby substantially filling the space between the * 25 panels. * S

The insulating material ensures that the tubes are held against the outer panel to ensure efficient transfer of heat therebetween, typically by conduction.

Typically the material presses the tubes against the outer panel.

For example insulating foam material expands as it cures, which presses the tubes into contact with the outer panel.

Typically the foam is an isocyanurate or other expanding foam Typically the material bonds the inner and outer panels together.

In one embodiment, the tubes are biased towards and in contact with the outer panel substantially along their respective lengths.

In one embodiment the inner and outer panels are roof panels or form at least part of the same. Typically the solar thermal collector can be connected to roof panels of a commercial twin skin roofing system. Typically the roof panels can be shaped and sized to suit the user's requirements.

In one embodiment one or both panels are made from aluminium. In a further embodiment one or both panels are made from copper. In a yet further embodiment one or both panels including glazing.

As the panels are metallic, it is more straightforward to make large solar collectors for roofs compared to the known glass-fronted panels, as they are less fragile.

* ** *** * S In one embodiment the outer panel is coated with black * * polyester paint or a selective coating. This promotes the absorption of solar energy or radiation of heat. * *

In a further embodiment the outer panel is coated with a photovoltaic paint. Thus electricity can be generated from solar energy. An advantage of using the tubes in combination with the photovoltaic system is that heat generated from the photovoltaic system is transferred away therefrom by the tubes, so the photovoltaic system does not lose efficiency due to overheating.

In one embodiment each panel is provided with a pair of header tubes, typically running parallel and adjacent to opposite edges of the panel. Typically a plurality of riser tubes are connected between the header tubes. However, it will be appreciated that a number of different tube arrangements are possible.

In one embodiment the riser tubes are provided with bends or curved sections adjacent the header tubes to allow strong contact to be made with the outer panel. As the header tubes tend to be larger in radius than the riser tubes, the bends allow the riser tubes to contact the outer panel simultaneously with the header tubes -if no bends or curves were provided the riser tubes would be spaced from the outer panel by the difference in radius of the header tube.

In one embodiment the header tubes are provided with connection means to allow the header tubes of adjacent solar collectors to be connected together. Typically the connection means are flexible tubes. *e..

S....' In one embodiment the header tubes are provided with bends or curved sections adjacent their ends, such that the ends are spaced apart from the outer panel when the header tubes are embedded in the foam. Typically each end is disposed within a * 25 recess in the foam. Typically the recess is formed from a plastic :. or metallic container located between the panels, although it will be appreciated that there means of forming a recess to limit the expansion of foam may be used. Thus a user is able to manoeuvre the connections between header tubes more easily, as otherwise friction may prevent movement thereof if the ends were pressed up hard against the outer panel.

In one embodiment the outer and/or inner panel is provided with an aperture to allow access to the connection means.

Typically the aperture is covered by cover means.

In one embodiment the solar thermal collectors have sloping edges to allow opposed edges of two solar thermal collectors to fit together in an overlapping manner. The overlap helps make the fit weatherproof.

In one embodiment the ends of the outer panel are provided with complementary hooks and/or recesses to allow interlocking of panels.

In one embodiment the cover means bridges the join between adjacent solar thermal collectors to hold the same in position.

In one embodiment the outer panel and cover means include complementary respective protrusions and/or recesses.

In one embodiment the cover means is provided with securing means to secure the cover means to the outer panel or panels. * *

In one embodiment the liquid is water. In a further embodiment the liquid includes propylene glycol to improve protection against the liquid freezing. It will be appreciated that other :. liquids or heat transfer fluids may be used depending on the ::.::j circumstances and location of the solar collector.

In one embodiment the liquid is circulated to a swimming pooi.

In a further embodiment the liquid is collected in a reservoir.

In one embodiment multiple solar thermal collectors can be connected together to create a roof.

In a further aspect of the invention, there is provided a method of manufacturing a solar thermal collector comprising the steps of: placing one or more tubes between an inner panel and an outer panel; the tubes being suitable for containing liquid and collecting solar energy received by the outer panel; wherein material is inserted between the panels such that expansion thereof as it cures causes the tubes to be pressed against the outer panel.

In one embodiment the material is foam which is injected.

In one embodiment metallic sheets are pressed or otherwise moulded and/or cut to the required shape to form the panels.

In one embodiment one or more tubes may be taped in position prior to the foam or other material being inserted to prevent foam getting between the tubes and outer panel. In a further embodiment one or more tubes are soldered in position prior to the foam being injected. It will be appreciated that other methods are available for securing the tubes in position, to prevent the foam from moving the tubes out of position when it * expands. Sb. * 25

In one embodiment the tubes are embedded in the foam of the ::.::j solar thermal collector.

In one embodiment the panels are conveyed through a curing oven to cure and expand the foam.

In one embodiment the panels are cut to the desired length once the foam is cured.

In one embodiment the tubes within a collector may be connected to the tubes of an adjacent collector via connection means.

In one embodiment a portion of one or both of the panels can be removed to access the connection means.

In a further embodiment a plurality of solar thermal collectors are connected together to form a roof.

In a further embodiment solar thermal collectors can be fitted alongside standard twin skin roof panels of a corresponding shape and size.

In one embodiment the outer panel is coated with a heat absorbing or photovoltaic substance.

In a yet further aspect of the invention, there is provided apparatus for manufacturing a solar thermal collector comprising: *1* means for providing inner and outer sheets of metal for forming respective inner and outer panels; insertion means for distributing material between the inner and outer sheets; conveying means for conveying the sheets through curing : means; wherein means are provided for locating a plurality of interconnected tubes on the outer sheet prior to material being distributed thereonto.

In one embodiment the insertion means is a foam injector.

In one embodiment the curing means is an oven which causes expansion of the material between the panels.

In one embodiment unwinding means are provided to unroll elongate sheets of metal from drums.

In one embodiment cutting means are provided to cut the panels to the desired length.

In one embodiment means are provided to press the panels into the desired shape.

Specific embodiments of the invention are now described wherein: -Figure 1 illustrates a solar thermal collector in accordance with the invention (a) in a schematic plan view; and (b) as a cross-section view along line A-A'.

Figure 2 illustrates a further solar thermal collector in accordance with the invention (a) in a schematic plan view; and (b) as a cross-section view along line A-A'. S... * . S...

Figure 3 illustrates how solar thermal collectors could be :.. connected together (a) in cross-sectional view; (b) as a cross-section view along line A-A'; and (c) a schematic top view * showing the cover plate.

S

Figure 4 schematically illustrates (a) the apparatus used to make a solar thermal collector in accordance with the invention; and (b) a schematic partial side view of the product being made.

With reference to Figures la-b, there is illustrated a solar thermal collector 2 comprising an outer roof panel 4 spaced apart from an inner roof panel 6 by a predetermined space into which insulating foam 8 is injected. The panels are made from pressed aluminium in this example although it will be appreciated that other materials could be used.

The space also includes an upper header tube 10 and a lower header tube 12 with riser tubes 14 connected therebetween. The tubes are taped into position on the internal surface of the outer panel, such that when the foam is injected into the space between the panels, the pressure from the expanding foam presses the tubes hard against the outer panel, thereby ensuring good thermal contact therebetween. Surprisingly, the tubes are not crushed by the expansion of the foam.

Liquid can be circulated between the header tubes and riser tubes, thereby allowing the structure to serve as a solar thermal collector. Multiple solar thermal collectors can be connected together to create a roof with an array of outer panels exposed to sunlight.

The structure can therefore be used to heat water whereby the outer panels absorb heat from solar energy and conduct the heat *. to the liquid in the tubes. The liquid in the tubes can be water which is thus heated directly by the solar collector, or a liquid which can be circulated to a heat exchange system where the * * heat in the liquid is transferred to water separately contained in 25 the system. * *

* Alternatively the structure may be used to radiate heat if hot **S*.* * water is distributed to the structure for dispersion of the thermal energy therefrom.

With reference to Figures 2a-b, there is illustrated a further solar thermal collector 58 which is similar to that described in Figures ia-b but configured as an end section.

The end section is provided with an upper header tube 10 and a lower header tube 12 with riser tubes 14 connected therebetween, but the upper header tube is provided with an end cap 54 at one end, and the lower header tube is provided with a flow or return pipe 56 depending on which end of the roof the section is positioned. It will be appreciated that the end section 58 could be a mirrored to form the end section at the other end of the array.

With reference to Figure 3a, there is illustrated how a first solar thermal collector 2 can be connected to a second solar thermal collector 2' via connection means in the form of flexible joint 16 fitted between respective header tubes 10, 10'. A plastic or tin cup 62 may be located between the panels to provide a recess in the foam 8 for situation of the joint 16 therein, which is thus protected from the foam 8.

Thus a roof can be constructed from multiple solar thermal collectors wherein liquid is able flow between the same, allowing the system to be expanded in a scalar manner. S... $ . S...

As illustrated in Figure 3b, in this example the riser tubes 14 are provided with bends 18 to allow contact to be made with the * outer panel 4. The bends compensate for the difference in radius 25 between the riser tubes 14 and the larger header tubes 10. *5

With respect to Figure 3c, the outer panel is provided with an *S..S.

* aperture 26 to allow access to the joint 16 so that a user can make or adjust the connections between respective header tubes 10, 10'. The aperture 26 is covered by cover means in the form of cover plate 22, the periphery of which is provided with a silicon gasket 24 to form a weatherproof seal between the plate and panel 4.

The panels may be provided with overlapping joins so as to helps hold adjacent collectors 2, 2' together and form airtight seals therebetween. The overlapping portions can be secured together with bolts. The foam typically extends to the ends of the panels.

The cover plate is shaped to match the overlapping join between the panels, such that the ridge 22 of the plate matches the ridge 28 of the panel. The plate 22 may also be secured into position by means such as bolts 60, and extending into the holes used to secure the overlapping portions together, such that the structures are locked in position.

With reference to Figure 4a, the manufacture of the collector is illustrated. Elongate lengths of sheet metal are unwound from drums 28, 30, as indicated by arrows 32, 34, to form respective inner and outer sheets 36, 38, the precursors to the inner and outer panels 6, 4, and are pressed to form the appropriate shape.

It will be appreciated that pre-pressed sheets could also be used to make the panels. * * ***.

The header tubes 10, 12 with riser tubes 14 connected therebetween are placed on the inner surface of the outer sheet * 38, and taped in position. 25

A foam injector 40 then sprays insulating foam 8 on the tubes * and outer sheet 38 before conveying the sheets into a curing * oven 44. The heat of the oven 44 causes the foam to expand as indicated by arrow 64 and press the tubes against the inside of the outer sheet 38, thereby embedding the tubes and connecting the two sheets together.

Figure 4b illustrates how the tapes 66 help prevent foam from getting between the tubes and the outer panel as the foam expands 64 which may otherwise prevent good contact between the tubes and the outer panel 4.

As the dual sheet structure emerges from the oven 44 it can be trimmed to the correct size to match the tube structure embedded therein.

Thus in use a builder can make a large roof exclusively from solar thermal collectors according to the invention, or in combination with compatible twin-skin roofing panels which look similar but are not provided with tubes therein.

The builder can fit the structures together, and in the case of adjacent solar thermal collectors, can simply connect the opposed header tubes using the flexible joints via the aperture, which can subsequently be hidden by a cover plate.

Liquid can then be provided in the tubes such that solar energy can be collected by the roof structures to heat the water, which can then be circulated or collected in a tank depending on the user's requirements.

S

*.55.. * S

It will be appreciated by persons skilled in the art that the : present invention may also include further additional S.. . modifications made to the device which does not affect the overall functioning of the device. *

S.....

Claims

Claims 1. A solar thermal collector (2) comprising: an outer panel (4) spaced apart from an inner panel (6), and one or more tubes (10, 12, 14) located in the space between the panels; the tubes being suitable for containing liquid and arranged to allow the transfer of heat between the liquid and outer panel; wherein material (8) is provided between the panels such that the tubes are held against the outer panel by the material substantially along their respective lengths.
2. A solar thermal collector according to claim 1 wherein the material is insulating and/or expandable material.
3. A solar thermal collector according to claim 1 or 2 wherein the material is isocyanurate or insulating foam.
4. A solar thermal collector according to any preceding claim wherein the material expands to substantially fill the space between the panels when it is cured.S S.... * .
5. A solar thermal collector according to any preceding claim * wherein the material presses the tubes against the outer panel S..* 25 when it expands. * .*
6. A solar thermal collector according to any preceding claim **.**.

* wherein the material bonds the inner and outer panels together.
7. A solar thermal collector according to any preceding claim wherein the tubes are biased towards and in contact with the outer panel substantially along their respective lengths.
8. A solar thermal collector according to any preceding claim wherein the inner and outer panels form at least part of a roof panel.
9. A solar thermal collector according to any preceding claim wherein at least one panel is made from aluminium or copper, and/or includes glazing.
10. A solar thermal collector according to any preceding claim wherein the outer panel is coated with black polyester paint or photovoltaic paint.
ii. A solar thermal collector according to any preceding claim wherein each panel is provided with a pair of header tubes, running parallel and adjacent to opposite edges of the panel.
12. A solar thermal collector according to claim 11 wherein a plurality of riser tubes are connected between the header tubes.
13. A solar thermal collector according to claim 12 wherein S... . . the riser tubes are provided with bends or curved sections adjacent the header tubes to allow strong contact to be made with the outer panel. 25
14. A solar thermal collector according to any of claims 11-13 wherein the header tubes are provided with bends or curved * sections adjacent their ends, such that the ends are spaced apart *...*S * from the outer panel when the header tubes are embedded in the material.
15. A solar thermal collector according to claim 14 wherein each end of each header tube is disposed within a recess in the material.
16. A solar thermal collector according to any of claims 11-15 wherein the header tubes are provided with connection means to allow the header tubes of adjacent solar collectors to be connected together.
17. A solar thermal collector according to claim 16 wherein the outer and/or inner panel is provided with an aperture to allow access to the connection means.
18. A solar thermal collector according to claim 17 wherein the aperture is covered by cover means.
19. A solar thermal collector according to claim 18 wherein the cover means bridges the join between adjacent solar thermal collectors to hold the same in position.
20. A solar thermal collector according to claim 19 wherein the adjacent solar thermal collectors have sloping edges to allow opposed edges of two solar thermal collectors to fit together in an overlapping manner. 0SSS * * ***.
21. A solar thermal collector according to any of claims 18-20 wherein the outer panel and cover means include complementary : . respective protrusions and/or recesses. *** * 2522. A solar thermal collector according to any of claims 18-21 * wherein the cover means is provided with securing means to **.s� * secure the cover means to the outer panel or panels.23. A solar thermal collector according to any preceding claim wherein the ends of the outer panel are provided with complementary hooks and/or recesses to allow interlocking of panels.24. A solar thermal collector according to any preceding claim wherein the liquid is water 25. A solar thermal collector according to any preceding claim wherein the liquid includes propylene glycol.26. A solar thermal collector according to any preceding claim wherein the liquid is circulated to a swimming pool.27. A solar thermal collector according to any preceding claim wherein the liquid is collected in a reservoir.28. A solar thermal collector as herein described with reference to Figures 1-3c 29. A roof or at least a part thereof formed from a plurality of interconnected solar thermal collectors according to any previous claim.30. A method of manufacturing a solar thermal collector S...comprising the steps of: placing one or more tubes (10, 12, 14) between an inner panel (6) and an outer panel (4); the tubes being suitable for containing liquid and *.S * 25 collecting solar energy received by the outer panel; :. wherein material (8) is inserted between the panels such * * that exptnsion thereof as it cures causes the tubes to be pressed 555S*S * against the outer panel.31. A method according to claim 30 wherein the material is foam which is injected.32. A method according to claim 30 or 31 wherein metallic sheets are pressed or otherwise moulded and/or cut to the required shape to form the panels.33. A method according to any of claims 30-32 wherein one or more tubes are taped or soldered in position prior to the material being inserted.34. A method according to any of claims 30-33 wherein the panels are conveyed through a curing oven to cure and expand the foam.35. A method according to any of claims 30-34 wherein the panels are cut to the desired length once the foam is cured.36. A method according to any of claims 30-34 wherein a portion of at least one of the panels can be removed to access connection means for connecting the collectors together.37. A method according to any of claims 30-35 wherein the *::::* outer panel is coated with a heat absorbing or photovoltaic substance. S. *I38. Apparatus for manufacturing a solar thermal collector S..comprising: means for providing inner and outer sheets of metal (36, * 38) for forming respective inner and outer panels (6, 4); * insertion means (40) for distributing material (8) between the inner and outer sheets; conveying means for conveying the sheets through curing means (44); wherein means are provided for locating a plurality of interconnected tubes on the outer sheet prior to material being distributed thereonto.39. Apparatus according to claim 38 wherein the insertion means is a foam injector.40. Apparatus according to claim 38 or 39 wherein the curing means is an oven which causes expansion of the material between the panels 41. Apparatus according to any of claims 38-40 wherein unwinding means are provided to unroll elongate sheets of metal from drums.42. Apparatus according to any of claims 38-41 wherein cutting means are provided to cut the panels to the desired length.43. Apparatus according to any of claims 38-42 wherein pressing means are provided to press the panels into the desired shape. S...44. Apparatus as herein described with reference to Figure 4a.S..... * . S. ** * . . * aI I. * a * *..S15*1.5 S *