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Title:
THERMAL SOLAR PANEL
Document Type and Number:
WIPO Patent Application WO/2009/083273
Kind Code:
A1
Abstract:
A thermal solar panel (1) for converting solar energy into heat, the panel having a load-bearing structure (2), structures (3) for flow of fluid, and one or more layers (11) of transparent material, which are firmly fixed to the load-bearing structure (2) and are positioned on top of the structures (3) for flow of fluid; the load-bearing structure (2) being made of composite material; the load-bearing structure (2) being monolithic and having a shape such as to create at least part of the shape of said structures (3) for flow of fluid, thus guaranteeing a considerably economy of production.

Inventors:
FARELLI BRUNO (IT)
Application Number:
PCT/EP2008/011170
Publication Date:
July 09, 2009
Filing Date:
December 18, 2008
Export Citation:
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Assignee:
FARELLI BRUNO (IT)
International Classes:
F24J2/46; F24J2/50; F24S10/50
Foreign References:
US4056092A1977-11-01
GB1526062A1978-09-27
DE3418005A11985-11-21
FR2339144A11977-08-19
FR2406166A11979-05-11
FR2298067A11976-08-13
US4194491A1980-03-25
FR2514873A11983-04-22
FR2500597A11982-08-27
US3974822A1976-08-17
Other References:
DATABASE WPI Section Ch Week 8602, Derwent World Patents Index; Class A93, AN 1986-009822, XP002528092
Attorney, Agent or Firm:
LOTTI, Giorgio (Corso Vittorio Emanuele II 61, Torino, IT)
Download PDF:
Claims:

CLAIMS l.A thermal solar panel (1) (1') (1'') (1''') (I 1 ''') for converting solar energy into heat, the panel comprising a load-bearing structure (2), structures (3) for flow of fluid, and one or more layers (11) of transparent material, which are firmly fixed to the load-bearing structure (2) and are positioned between a light-radiation source and the structures (3) for flow of fluid; the panel (1) (1') (1'') (l' # / ) (1'''') being characterized in that the load-bearing structure (2) is monolithic and is made of composite material; the load-bearing structure (2) having a shape such as to create at least part of the shape of said structures (3) for flow of fluid.

2. The thermal solar panel according to Claim 1, wherein the load-bearing structure (2) is made by means of moulding or injection.

3. The thermal solar panel according to Claim 1, wherein the layers (11) of transparent material comprise a single layer of glass or plastic material .

4. The thermal solar panel according to Claim 1, further characterized in that a layer of thermally conductive material (8) is set in contact

with parts of the shape of the structures (3) for flow of fluid, said layer of thermally conductive material (8) being firmly anchored to said load- bearing structure (2) . 5. The thermal solar panel according to Claim 3 or Claim 4, characterized in that it comprises a chamber (12) set between the layer (11) of glass or plastic material and the layer of thermally conductive material (8); the camber (12) preferably containing air or other gases.

6. The thermal solar panel according to Claim 3 or Claim 4, characterized in that said single layer of glass or plastic material is separated by shim structures (14a, 14b) from said layer of thermally conductive material (8) thus forming a chamber (12') set in vacuum conditions.

7. The thermal solar panel according to Claim 4, characterized in that:

- said layers of transparent material comprise at least a first layer of glass or plastic material (lla) and a second layer of glass or plastic material (lib) ;

- said second layer of glass or plastic material (lib) is separated by shim structures (14a, 14b) from said first layer of glass or plastic

material (lla) ; and

- said second layer of glass or plastic material (lib) is separated from said layer of thermally conductive material by a chamber (12) containing air or other gases.

8. The thermal solar panel according to Claim 5 or Claim 7, wherein the chamber (12) is connected to an external environment by means of a duct (14) to prevent formation of condensate on the surface of glass material facing the chamber (12) .

9. The thermal solar panel according to Claim 1 or Claim 2, characterized in that said composite material comprises glass-reinforced plastic. 10. The thermal solar panel according to Claim 1, characterized in that it further comprises a plurality of hydraulic connectors (7a, 7b) , which are designed, respectively, to receive a cold liquid and to send a hot liquid; said hydraulic connectors (7a, 7b) being in communication with lateral passages for fluid (7c, 7d) at the ends of the load- bearing structure (2) in a direction substantially parallel to a major axis (X) of said thermal solar panel (1) . 11. The thermal solar panel according to

Claim 10, characterized in that it can be connected in a fluid-tight way with other thermal solar panels (1) by means of said hydraulic connectors (7a, 7b) .

12. The thermal solar panel according to Claim 4, wherein said load-bearing structure (2) further comprises a plurality of channels (17) containing in use a layer of adhesive material (16) , which is designed to connect in a firm way said plate of transparent material and to connect in an air-tight way said plate of thermally conductive material (8) to said load-bearing structure (2) .

13. The thermal solar panel according to Claim 4, wherein said plate of thermally conductive material comprises a plurality of projections (8a). 14. The thermal solar panel according to Claim 13, characterized in that it comprises a layer of adhesive material (16a) deposited between the projections (8a) and the load-bearing structure (2) . 15. The thermal solar panel according to Claim 14, wherein in use said layer of adhesive - material (16a) interferes with said plurality of projections (8a) creating a plurality of channels (3") .

Description:

THERMAL SOLAR PANEL

DESCRIPTION The present invention relates to a thermal solar panel forming part, for example, of a solar-energy- system for heating fluids.

Thermal solar panels have mainly the purpose of heating water for sanitary use or for producing hot water to be used for heating environments.

Thermal solar panels exploit the principle of solar irradiation for heating the liquid (typically glycol) that flows in purposely provided pipes present inside the panels themselves, which constitute a so-called primary circuit. Inside the primary circuit the liquid circulates by the convective effect from the coldest areas to the hottest areas .

Said primary circuit further constitutes the heat accumulator. In fact, within the primary circuitthere must be present a given amount of liquid necessary to heat a sufficient amount of water with respect to the operating conditions of the thermal solar panel, such as, for example, the size - and hence the amount of liquid - of the secondary

circuit, formed by pipes flowing within which is the water that is to be used for sanitary purposes and for heating environments. The primary circuit is connected to a secondary circuit by means of a heat exchanger .

Typically, thermal solar panels are arranged in areas in which solar irradiation is maximum, such as, for example, roofs of buildings. On account of the average direction of solar rays with respect to the ground, typically thermal solar panels are set with an inclination depending upon the latidude of positioning, and for temperate-climate areas the best inclination ranges between 30° and 45°.

In general, the accumulator is directly mounted on the thermal solar panel. However, the accumulator can be mounted in places other than the thermal solar panel, for example, in cellars or attics. In these cases, however, it is necessary to equip the thermal solar panel with a pump designed to increase the flow of liquid of the primary circuit in so far as the convective effect alone is no longer sufficient to guarantee an effective circulation.

Known thermal solar panels are constituted by an outer casing made of a material that cannot be attacked by external atmospheric agents, typically a

metal material, such as aluminium.

The internal structure of the panel is instead typically made up of copper pipes flowing within which is the liquid of the primary circuit. The pipes are set in one and the same plane and are arranged parallel to one another to form a coil. In order to exploit better solar irradiation, the pipes of the primary circuit can be equipped with metal fins, designed to increase the pipe surface exposed to solar irradiation.

The primary circuit is not directly exposed to sun rays but is coated with a transparent plate with low thermal absorption, typically tempered glass or plastic, both of a non-reflecting type, set parallel to the plane in which the pipes of the primary circuit lie. Said plate of transparent material hence enables the primary circuit to be protected from atmospheric agents, without moreover significantly reducing the amount of heat received by the primary circuit.

The ends of the pipes of the primary circuit can come out of the panel and are connected to second pipes having a greater diameter by means of a weld designed to guarantee liquid-tightness. Finally, the rear part of the thermal solar panel

is constituted by a markedly insulating material (such as, for example, high-density polyurethane) in order not to disperse the heat stored.

Thermal solar panels of a known type have a structure that requires a high number of machining operations to obtain the end product. These machining operations are long and costly and hence jeopardize the economy of production of the thermal solar panel . Thermal solar panels of a known type have circular pipes, the geometry of which, albeit inexpensive to obtain, does not make it possible to have an optimized surface exposed to irradiation.

Finally, for a further protection of the external casing, known thermal solar panel must be painted. Painting constitutes a processing step that is laborious, costly, and critical. In fact, even the slightest scratching of the paint can in the long term lead to exposure of the underlying ferrous material to atmospheric agents, with the non- negligible risk of oxidation of the external casing with consequent damage to the device.

The purpose of the present invention is to provide a thermal solar panel that will be free from the drawbacks described above.

According to the present invention, a thermal solar panel is provided according to what is specified in Claim 1.

The invention will now be described with reference to the attached plates of drawings, which illustrate a non- limiting example of embodiment thereof and in which:

- Figure 1 shows a first embodiment of a thermal solar panel according to the present invention; - Figure 2 shows a cross section of the thermal solar panel of Figure 1 along the line II -II;

- Figures 3a and 3b show a cross section of the thermal solar panel of Figure 1 along the line III-

III; - Figure 4 shows a cross section of a second embodiment of the thermal solar panel of Figure 1 along the line II -II;

- Figures 5a and 5b show a cross section of the thermal solar panel of Figure 1 along the line III- III;

- Figure 6 shows a cross section of a third embodiment of the thermal solar panel of Figure 1 along the line II -II;

- Figures 7a and 7b show a cross section of the thermal solar panel of Figure 1 along the line III-

I I I ; and, finally,

- Figure 8 shows a cross section of a fourth embodiment of the thermal solar panel of Figure 1 along the line III -II I. With reference to Figure 1, designated as a whole by 1 is a thermal solar panel, which comprises a load-bearing structure 2, a plurality of manifolds, passages, and pipe fittings (not illustrated) , and presents as peculiar characteristic the fact of being made of a thermally insulating composite material, such as, for example, glass-reinforced plastic, in such a way as to obtain, in a single processing step, i.e., in a single monolithic structure, the load-bearing structure 2, the manifolds, passages, and the pipe fittings mentioned previously, considerably reducing the production costs and times.

The panel 1 has a major longitudinal axis X and further comprises a primary circuit 3' provided with a plurality of areas 3, which are set parallel to the axis X, and underlie a plate of glass delimited by a perimeter 4.

Thanks to the material of the load-bearing structure 2, it is no longer necessary to apply further layers of insulating material on a rear wall

of the panel 1, and a greater economy of operation is hence guaranteed.

A further saving is represented by the fact that the load-bearing structure 2 no longer requires painting on the outside in so far as composite materials, in particular, glass-reinforced plastic, can be moulded directly with the desired colour by means of a procedure of initial colouring.

The panel 1 also comprises two connectors 7a and two connectors 7b arranged along the outside of the structure 2 for the passage, respectively, of a cold liquid and a hot liquid, which circulate in the primary circuit 3' and of which the cold liquid comes from a heat exchanger (not illustrated) , whilst the hot liquid flows towards the heat exchanger itself.

As is illustrated in Figure 2, the connectors 7a and 7b can, for example, comprise threaded pipe fittings and are connected in a liquid-tight way with lateral passages 7c and 7d for the fluid, which are substantially parallel to the side walls 5, 6 of the thermal solar panel . In turn, the ducts communicate with the areas 3 of the primary circuit 3' . The presence of the connectors 7a and 7b moreover

guarantees the possibility of connecting in series a number of thermal solar panels 1' by means of connecting elements, such as nipples (not shown) , in such a way as to guarantee a greater surface for heating of the fluid of the primary circuit without the need to design panels of different size.

In the embodiment illustrated in Figures 1 and 2, the area 3 of the primary circuit 3' further comprises channels set underneath a metal plate 8, which is positioned on a first groove 8s of the load-bearing structure 2 and is fixed to the load- bearing structure 2 in the fixing points 10a, 10b. Non-limiting examples of fixing techniques can be gluing or screwing. The panel 1 further comprises a plate 11, which is made of transparent material, for example, plastic or glass of a tempered type, and is set on top of the metal plate 8 and on a second groove 11s of the load-bearing structure 2 in such a way as to leave an air gap 12 between the plates 8 and 11.

The plate 11 is fixed to the load-bearing structure 2 in the points 13a, 13b with the same techniques described for fixing of the metal plate 8. The flow of the liquid of the primary circuit 3' moves in a direction D, from the passage 7c to the

passage 7d. This phenomenon can occur on account of the "thermal -siphon effect" alone (and in this case the thermal solar panel 1 must be inclined in such a way as to have the lateral passage 7d for the fluid at a greater height than the lateral passage Ic for the fluid) or by using, for example, a pump.

Illustrated in Figure 3a is a load-bearing structure 2 characherized in that the areas 3 of the primary circuit are of a "fretted" type, whereas in Figure 3b the areas 3 of the primary circuit are of a linear type. In particular, the shape of the areas 3 of the fret -shaped primary circuit 3 guarantees the best efficiency of the thermal solar panel 1 in so far as the major side of the structure of the triangles that form the fret faces the metal plate. The vertex of the triangles that form the fret faces the side not irradiated by the sun, where it is necessary to disperse the lowest amount of heat possible, with consequent exposure of a smaller area.

The shape of the areas 3 of the primary circuit shown in Figure 3b, instead, guarantees the best economy of production of the thermal solar panel 1 on account of its constructional simplicity. Clearly, in the case where a fret shape is adopted,

the passages 7c, 7d constitute a true lateral duct, substantially parallel to the major axis X of the thermal solar panel 1, and jointly set in communication all the areas 3 of the primary circuit. In the case, instead, where a linear shape is chosen, the passages 7c, 7d identify only a limited portion of the total area of the primary circuit, in so far as, underneath the metal plate 8, the fluid flows in an area without interruptions or obstacles.

In Figures 3a and 3b, there may be noted the presence of anti-condensate passage areas 14, for the purpose reducing the risk of the water vapour condensing on the wall of the glass 11 facing the metal plate 8, thus reducing the efficiency of the thermal solar panel 1.

Figure 4 shows a second embodiment of the panel 1 ' ' of the present invention, in which set on top of the metal plate 8 is a plate of transparent material 11 of a tempered type, positioned on two shim structures 15a, 15b, in turn positioned on the metal plate 8, along its perimeter. The area 12' delimited by the shim structures 15a, 15b, by the surface of the plate of transparent material 11 facing the metal plate 8, and by the metal plate 8 is

characterized in that it is in vacuum conditions. This implies the fact that fixing between the shim structures 15a, 15b and, respectively, the metal plate 8 and the plate of transparent material 11 has to be air-tight. In this case, therefore, given a greater complexity of construction, it is possible to obtain a higher efficiency in so far as, once the sun rays have traversed the plate of transparent material 11, they no longer encounter gases, which could absorb heat, but impinge directly upon the metal plate 8. With this technique the formation of condensate on the internal face of the plate of transparent material 11 is moreover prevented.

The plate of transparent material 11 is fixed to the load-bearing structure 2 in the points 13a, 13b with the same techniques described for fixing the metal plate 8.

The shim structures 15a, 15b are fixed to the load- bearing structure 2 of the thermal solar panel 1 in the fixing points 13a, 13b.

Figure 5a illustrates a structure of the panel 1'', in which the areas 3 of the primary circuit assume a fret shape, whereas in Figure 5b the areas 3 of the primary circuit are of a linear type. The peculiar characteristics of one type of area with respect to

the other are identical to the ones described for the first embodiment of the invention.

The panel 1' ' differs from the panel 1 in that the presence of an area 12' where a vacuum is created enables elimination of the anti -condensate passage areas 14, thus guaranteeing complete insulation of the metal plate 8 from air.

Figure 6 shows a third embodiment of the panel I' 1 '. In the present embodiment there may basically be noted a combination of the first and second embodiments of the invention described previously. In particular, there may be noted the presence of an area 12' where a vacuum is created, which is insulated at the top by a first plate of transparent material 11a, at the bottom by a second plate of transparent material lib (both of a tempered type, as in the other embodiments of the invention) and laterally by the shim structures 14a and 14b.. The second plate of transparent material lib is fixed in the points 10c and 1Od on the groove 8s of the load- bearing structure 2. The shim structures 14a and 14b are fixed to the load-bearing structure 2 in the points 13a, 13b with the techniques described previously. Located underneath the second plate of transparent material lib is an air gap 12, which

separates the second plate of transparent material lib from the metal plate 8. The metal plate 8 is fixed to the load-bearing structure 2 in the points 10a and 10b using the techniques described previously.

Figure 7a shows the solution in which the areas 3 of the primary circuit are fret-shaped, whereas Figure 7b shows the solution in which the areas 3 of the primary circuit are of a linear type. In order to prevent formation of condensate on the bottom face of the second plate of glass lib, the anti-condensate passage area 14 is again present, which sets in communication the air gap 12 with the outside . Finally, Figure 8 illustrates a fourth embodiment of the panel \ < • > • of the present invention.

In particular, the present embodiment has a load- bearing structure 2. It is moreover characterized by the presence of a plurality of channels 17, designed to be filled with an adhesive material 16, which ensure a higher degree of contact with the metal plate 8, on the one hand, and with the plate of transparent material 11, on the other.

Provided underneath the metal plate 8 is a plurality of embossings and/or projections 8a made

of the same material as the metal plate 8, which extend in rows in a direction substantially orthogonal to the line III -III. Deposited underneath the plurality of embossings 8a is a layer of adhesive material 16a, which is also deposited in the direction of the embossings 8a.

The distance between one embossing 8a and the other can vary as a function of different, parameters, amongst which the level of vacuum that is created in the area 12'. Optimal values of distance between adjacent embossings 8a can range between 30 and 150 mm.

The height of the layer of adhesive material 16a must be such that, when the metal plate 8 is rested on the respective grooves, the plurality of embossings 8a is embedded in the layer of adhesive material 16a. Consequently, the plurality of embossings 8a will cause a widening of the layer of adhesive material 16a, as is shown in the figure. The fourth embodiment of the invention is useful both when the thermal solar panel \ < ' > > has a gap 12 filled with air and in the case where there is a area 12' where a vacuum has been created, as described in the previous embodiment . In particular, in the case where the thermal solar

panel is provided with an area 12' where a vacuum has been created, the presence of the adhesive layer 16a guarantees that, when the air is sucked out of the area 12', the metal plate 8 will bend towards the area 12' to a much smaller extent as compared to the case of the second embodiment .

For the same reason, the layer of adhesive material 16 deposited in the plurality of channels 17 ensures a better contact and prevents any leakage of air into the area 12'.

Clearly, it is not important for the layer of adhesive material 16a to insulate perfectly the plurality of channels 3'' that remain following upon its deposition in the area 3 of the primary circuit, in so far as what is really important is that there should in any case be the possibility of circulation of the liquid of the primary circuit.

Thanks to the layers of adhesive material 16a and 16, gluing of the metal plate 8 moreover guarantees a certain degree of sliding thereof with respect to the load-bearing structure 2 of the thermal solar panel, albeit maintaining a vacuum in the area 12', useful for compensating for any possible thermal expansions of the metal plate 8 or of the load- bearing structure 2 itself.

The advantages of the present invention are clear. In particular, the thermal solar panels illustrated can be produced to a major extent by means of moulding or injection of composite material in such a way as to form the load-bearing structure, manifolds, passages, and pipe fittings, and hence reduce considerably the number of operating steps.

The presence of a load-bearing structure made of composite material moreover enables the painting step to be avoided in so far as it is possible to mould material already containing pigments of the desired colour. In addition, the composite materials, unlike the ferrous materials traditionally used, are characherized by the immunity to phenomena of corrosion caused by atmospheric agents.

It is possible to increase the efficiency of the thermal solar panel by means of a fret shape of the area of the primary circuit, where the major sides of the triangles that form the fret are set in contact with the metal surface irradiated by the sun.

It is moreover possible to increase the efficiency of the thermal solar panel using an area where a vacuum has been created between the plate of

transparent material and the metal plate in such a way as to enable complete insulation of the internal structure of the thermal solar panel from external agents. Finally, it is possible to prevent any bending of the metal plate that separates the area where vacuum has been created from the areas of the primary circuit following upon suction of the air from the aforementioned chamber. Some variations may be made to the thermal solar panel, amongst which the use of areas of the primary circuit with a different shape, for example, semicylindrical or ellipsoidal; two or more vacuum areas can be used; the plates of glass may even not be tempered; and the solar panel itself may not be square in shape, but present a wide range of shapes so as to adapt as well as possible to the particular application.