ITPI20080097A1 - MEMBRANE FOR EXTERNAL SURFACE COATING AND SOLAR HEAT TREATMENT - Google Patents

Description

â € œMEMBRANE FOR COATING OF EXTERNAL SURFACES AND COLLECTION OF SOLAR HEATâ €,

DESCRIPTION

Scope of the invention

The present invention refers to a bituminous membrane suitable for covering external surfaces, in particular a protective waterproofing membrane, for capturing heat of solar origin, and for transferring said heat to a heat-carrying fluid, usable for example in air conditioning systems for rooms, or to produce sanitary water, or for other uses.

Brief notes on the known art

It is often desirable to integrate external building cladding elements with means of capturing solar heat, to exploit for energy purposes and at the same time isolate the surfaces from humidity, cold, noise, as well as perform aesthetic functions.

This integration has had greater development in the case of photovoltaic vehicles, which do not require the creation of hydraulic circuits inside the elements, and can also be produced in a flexible form. Various cladding solutions of this type are available, for example the materials known as â € œSolar Roofâ €, from Sika / Solar Integrated and â € œGeneral Solar PVâ €, from General Membrane. These are two membranes, in order based on PVC and bitumen-polymer compound, which have a surface partially covered with flexible photovoltaic modules. However, these materials have a price that is still too high for a widespread clientele.

Also known are materials for covering external structures capable of capturing solar heat and transferring it to a heat transfer fluid, suitable for solar thermal systems, used as coatings or integrated in the roofing of building structures, in particular roofs. Some examples are described in US patents 4,098,262, FR2246219 and SE440142, as well as in patent application CA2183376, where rigid panels containing ducts or pipes for the passage of a heat-carrying fluid are described. However, these devices are not easily adaptable to any roofing, in particular in the case of edges or dimensions that are not multiple of the length of the panel, practically limiting the absorbing surface. In particular, in the first of these documents there is an external transparent layer to favor the absorption of radiation, which brings with it a typical complication of common panels.

In the Italian patent n. 1095999, the use as a solar collector of a material commonly used in the form of a membrane to cover buildings, in particular to waterproof roofs, for example a bituminous membrane, is described. The heat captured as solar radiation heats a fluid flowing in an adjacent channel, which is not suitable for integration in a closed circuit of an air conditioning system. Furthermore, the sensor is not easily achievable, requiring the laying of a waterproof covering, a layer of gravel or the like, spacers and therefore the membrane. Considerations of the same type concern the device described in DE 2557895, which has metal tubes placed on the bottom of a container suitable for filling a depression in a roof, and submerged by a layer of a material capable of receiving and storing solar heat, in particular black gravel.

US 4,008,708 describes a roll-up membrane composed of three layers with spacers, all preferably made of silicone rubber. The first layer exposed to the sun is transparent, the second layer, transparent or opaque, is used to transmit the radiation to a heat-carrying fluid that flows within parallel channels delimited by the second and third layer. The space between the first and the second layer is empty to limit thermal losses by conduction between fluid and atmosphere, according to a typical scheme adopted in conventional solar panels. Being available in rolls, the membrane is of practical use; however, it is not suitable for waterproofing, in fact no indications are given on how to join the membranes in a continuous covering.

EP0014192 finally describes a flexible coating consisting of a plastic or elastomer membrane, in which parallel pipes are obtained to expose to the sun, with considerable conductive dispersions between the fluid and the environment, the system is not optimized as a solar collector. The main application is in fact foreseen in a circuit based on a heat pump, in which the coating is used to heat the water that runs through the pipes and which then transfers heat to the pump evaporator: the water obviously has a temperature lower than the environment. It is therefore important to maximize the heat exchange, also conductive and convective, between the environment and the water in the pipes.

Summary of the invention

It is therefore the purpose of the invention to provide a coating for surfaces exposed to the atmosphere, which is capable of capturing solar heat and transferring said heat to a heat transfer fluid, and which at the same time is capable of performing normal functions of a protective coating, especially waterproofing functions.

It is also an object of the invention to provide such a coating which does not have substantial limitations of shape and size of the surface to be coated.

It is also an object of the invention to provide such a coating which does not have substantial limitations of shape and size of the surface to be coated.

It is also an object of the invention to provide such a coating which is simple to lay without requiring substantial modifications to the technique for applying commonly used flexible coatings, in particular bitumen-polymer membranes.

It is also an object of the invention to provide such a coating which does not require substantial modifications to the process and to the production lines of common flexible coatings, in particular of bitumen-polymer membranes.

It is also an object of the invention to provide such a coating which is of low cost and therefore suitable for a wide range of civil constructions.

It is a further object of the invention to provide such a covering, the installation of which does not require the use of particular brackets, and is therefore architecturally integrated.

Finally, it is the purpose of the invention to provide a solar panel for a solar thermal system that allows the creation of a waterproofing coating for buildings and civil works in general.

These and other purposes are achieved through a coating membrane, in particular a membrane for building waterproofing, comprising:

- a layer of a mixture containing a bitumen and a polymeric substance;

- a support armature for said layer of compound, - a surface capable of capturing solar heat;

- a passage duct for a heat transfer fluid, in which

- said layer of mixture is able to conduct said heat from said surface to said duct, so that said fluid, passing through said duct, receives said heat; - said duct is flexible so as not to hinder the winding / unwinding of said membrane into / from a reel according to a winding / unwinding direction; And

- said duct has a portion submerged by said layer of compound.

In another perspective, the aforementioned purposes are achieved by a panel capable of capturing solar heat, including

- a passage duct for a heat-carrying fluid, - a layer suitable for conducting said heat captured by said surface to said duct, so that said fluid, passing through said duct, receives said heat,

in which:

- said layer suitable for conducting is a layer of a mixture containing a bitumen and a polymeric substance - a support reinforcement of said compound layer is provided;

- said duct is flexible so as not to hinder a winding / unwinding operation of said membrane into / from a reel according to a winding / unwinding direction; And

- said duct has a portion submerged by said layer of compound.

In particular, the compound layer is applied on one or two both faces of the reinforcement by means of an impregnation process.

The invention makes it possible to make a large number of building surfaces available for the collection of solar energy, which require protection from atmospheric phenomena, in particular precipitation or humidity, using a product of considerable versatility and simple application. The membranes consisting of a reinforcement impregnated with a bitumen-polymer mixture can be installed by means of procedures well known to waterproofing technicians. The exploitation of solar energy is therefore made possible by means of devices that can be easily integrated into the building structure without resorting to load-bearing structures of onerous construction and considerable visual impact.

The polymeric substance present in the blend can be chosen from a group comprising thermoplastic and / or elastomeric polymers, preferably:

- a polyolefin, in particular atactic polypropylene, - a copolymer based on styrene and butadiene,

- a copolymer based on ethylene, propylene and butene, - a combination of these polymeric substances.

The reinforcement can instead be made of a polymeric material, preferably chosen from:

- a polyester non-woven fabric,

- a polyester film,

- more generally, a material envisaged in the applicable technical standards, in Italy the UNI8818.

In particular, polyester stands out for its dimensional stability, resistance to temperatures in use and is also impermeable to water, a property that allows it to be used to build ducts and extruded armatures with ducts.

The membrane can also comprise a layer of protection from ultraviolet rays, preferably made of glass fiber or by adhesion of slate flakes, exposed in use to solar radiation, delimiting a layer of compound.

Preferably, the band of the membrane is between 60 and 180 centimeters, preferably between 80 and 120 centimeters; these values facilitate the manipulation of the coils, furthermore they constitute a good compromise between the number of longitudinal joints between membranes and the possibility of covering portions of external building structures having the most disparate widths, minimizing the areas that cannot be covered with the membrane according to the invention, and which must in any case be coated, for example with a normal conventional bitumen-polymer, without energy recovery.

Advantageously, a plurality of ducts are provided on each membrane. In this way it is easier to impose a fluid-dynamic regime that allows an adequate heat exchange even with low flow rates of heat-carrying fluid, avoiding stagnant areas or poor distribution of the fluid. Furthermore, the sealing surface to be made at the junctions and in the connection with the flow and return manifolds of the heat transfer fluid is reduced.

Preferably, the armature and the duct constitute a single body made by a procedure chosen from:

- extrusion,

- fixing the duct to a film, in particular gluing,

- connection of at least two films in a plurality of points, in particular by means of spacers of predetermined thickness, between the films remaining unconnected areas that define the duct. Thanks to the spacers, the possibility of deformations that can compromise the function of the ducts, subject to compression and bending actions exerted during packaging, installation, or during general maintenance interventions of a coated roof, is limited, due to the trampling. The dimensional stability of the ducts also facilitates the connection with the flow and return manifolds of the heat transfer fluid. Furthermore, the parallelism of the films that make up the reinforcement allows to eliminate the surface of this reliefs and depressions due to the presence of the ducts, facilitating the deposition process of the bitumen-polymer mixture on the reinforcement. In other words, the mixture can easily be deposited on the reinforcement in a similar way to what is normally done to produce the common bitumen-polymer membranes, in particular by impregnating the reinforcement in a tank containing a bitumen-polymer mixture.

In particular, the connection points between the two films form continuous lines, so that the unconnected areas constitute a plurality of continuous ducts separated by the continuous lines. Thus, also in this embodiment, the fluid-dynamic advantages allowed by a plurality of ducts, as described above, are made possible.

Advantageously, the ducts are parallel, preferably spaced with a constant pitch, with the ratio between the pitch and the width ranging from 1.3 to 1.8. These values represent a compromise between a good surface exposure of the duct to the conductive thermal front, as discussed above, and a good convective exchange coefficient inside the duct.

Preferably, the ducts have a substantially rectangular cross section with width and height respectively parallel and perpendicular to the reinforcement. This shape and this arrangement have considerable advantages. In the first place, the surface exposed to the sun is maximized, or, more precisely, the surface of the pipe that is reached by the heat transmitted by conduction according to the most favorable path, normal to the width of the duct. Secondly, the rectangular shape and its orientation hinder the winding of the membrane on rollers such as coils less than other shapes, ensuring the dimensional stability of the duct in the best possible way. Thirdly, this shape and this orientation facilitate the deposition phase of the compound on the reinforcement, minimizing the disturbance created by the presence of the ducts on the deposition surface. This is an advantage similar to that offered by the spacers between the films making up the reinforcement according to another embodiment. The width is between 10 and 250 millimeters, in particular between 10 and 30 millimeters, easily made possible by the extrusion process, or between 80 and 100 millimeters, and the height is between 2 and 10 mm, in particular between 3 and 5 millimeters.

Preferably, the conduits are parallel to the winding direction of the coil. This allows you to limit or potentially cancel the number of joints on the ducts that involve possible leak points. These junctions, as well as those between the ducts of a membrane and the outgoing and return manifolds of the heat transfer fluid, are in any case made easier with respect to a different or random orientation of the ducts.

In particular, the duct forms a coil or meander having an inlet and an outlet for the heat transfer fluid, the inlet and outlet being arranged on the same side with respect to the membrane. This is particularly indicated when limited flow rates of heat transfer fluid have to be managed, to enhance turbulence and therefore heat exchange; the arrangement of the ports indicated above also facilitates a rational arrangement of the flow and return manifolds of the heat-carrying fluid.

Advantageously, the membrane has two lateral strips parallel to the winding direction in which there is no duct; these strips have a width preferably between 80 and 120 millimeters, to facilitate the hot sealing of the membrane with membranes of the same type or bituminous membranes in general, according to the application technique normally used for this type of products.

In a particular embodiment, the membrane comprises at least two plates, which delimit a layer of compound, and the ducts are enclosed between the two plates. This membrane takes the name of double-armed membrane, and allows to obtain the advantages of a regular surface, free of depressions and reliefs due to the presence of ducts on the reinforcement surface, as already described.

Advantageously, the membrane according to the invention is used with:

- an inlet manifold and a deduction manifold for the heat transfer fluid,

- a fitting adapted to engage a duct of the membrane in a hermetic connection,

- said manifold and the fitting having portions capable of mutually engaging, making a preferably removable hermetic connection, in particular comprising a joint.

In particular, to create a solar panel as defined above, the following phases are foreseen:

- arrangement of an adduction manifold and an abduction manifold of said heat-carrying fluid,

- arrangement of a fitting adapted to engage a duct of said membrane in a hermetic connection such that said manifold and said fitting mutually engage, making a preferably removable hermetic connection, in particular a joint.

Brief description of the drawings

The invention will be illustrated below with the following description of its embodiments, given by way of non-limiting example, with reference to the attached drawings in which:

- figure 1 shows a coil containing a coating according to the invention, and a section of the membrane according to a plane transversal to the winding direction;

â € “figure 2â € ™ is a cross section of a membrane in a first embodiment;

â € “figure 2â € is a partial section on an enlarged scale of the membrane of figure 2â € ™;

â € “figure 2â € â € ™ is a partial section of the armature and ducts of the membrane represented in figures 2â € ™ and 2â €; â € “figures 3â € ™ and 3â € are cross-sections in different scales of a double-armored membrane;

â € “figure 4â € ™ is a cross section of a simple membrane in a second embodiment;

â € “figure 4â € is a partial section on an enlarged scale of the membrane of figure 4â € ™;

â € “figures 4â € â € ™ and 4â € are partial sections of reinforcement layers to make the membrane represented in figures 4â € ™ and 4â €;

â € “Figures 5â € ™ and 5â € schematically show possible shapes of passage ducts for a heat transfer fluid; - figure 6 shows in section a junction between two membranes according to the invention;

- figure 7 schematically shows a membrane arranged between two collectors;

â € “figures 8â € ™, 8â € and 8â € ™ â € show manifolds suitable for coupling with the joint of figure 9;

- figure 9 shows a joint of a duct of a membrane according to the invention with water distribution / collection manifolds;

- Figures 10 and 11 show a joint of the type of figure 9 engaged in an interlocking with a manifold, in axonometric and sectional view.

Description of preferred embodiments

A first embodiment of the membrane according to the invention is schematically represented in figures 1 and 2â € ™ -2â € â € ™. The membrane, packaged in the form of a coil 1, comprises an armor 24, a layer 23 of bitumen-polymer compound for each side of the armor 24, and, preferably, a layer 27 resistant to ultraviolet rays to protect the compound 23 exposed to the atmosphere. The bitumen-polymer compound is a mixture containing a bitumen and a polymeric substance, in particular a thermoplastic polymer such as atactic polypropylene. This mixture is deposited, by means of an impregnation process in the tank, on the reinforcement 24, made from for example a non-woven fabric (TNT) 22, on which the ducts 21 have been previously glued, obtained by extrusion of a thermoplastic material and intended to be crossed by water as a heat transfer fluid; preferably the material that constitutes the TNT and the ducts is polyester based. In the figures only three ducts 21 are shown, in particular in figure 1 a membrane 10 is represented with nine ducts parallel to each other and to the unwinding direction of the reel 1, having the same width; the membrane 20 of figure 2â € ™ -2â € â € ™ instead contains six ducts arranged in the same way as the membrane 10. The dimensions of the membrane 20 are preferentially: band L close to 1000 mm, width l of each duct around 100 mm each, height b equal to 5 mm, and are spaced according to a pitch p equal to 140 mm. The thicknesses of the film 22, of the bituminous layers 23 and of the protective layer 27 respectively are the lowest possible and depend on the production technologies and the operating conditions adopted in production.

Figures 3â € ™ and 3â € represent a double-armored membrane 30, comprising a reinforcement 34, a layer 33 of bitumen-polymer compound for each side of the reinforcement 34, and, preferably, a layer 37 resistant to rays ultraviolet to protect the compound of layer 33 exposed to the atmosphere; like the armor 24, the armor 34 is made by gluing the ducts 31 on the non-woven fabric layer 32. The membrane 30 also comprises a second armor 35 consisting of a nonwoven layer substantially parallel to the layer 32, so that a bituminous layer 33 is enclosed between the two reinforcements 34 and 35. A further bituminous layer 36 is deposited on the face of the reinforcement 35 opposite the reinforcement 32. Compared to the simple membrane 20, the double-reinforced membrane 30 has the face 38 to be placed on the more regular surface to be coated, since the compound is laid on a smooth surface, devoid of the irregularities created by the pipes 21.

Figures 4â € -4â € represents a membrane 40 comprising a reinforcement 44 or 46, a bitumen-polymer compound layer 43, and a layer 47 to protect the bituminous layer 43 from ultraviolet radiation from the sun . Unlike the membranes 20 and 30, the ducts 41 are not welded onto the film, but incorporated into the armature itself. In the case of figure 4â € â € ™, the armature 44 including the ducts 41 is obtained by extrusion, preferably again of polyester, while in the case of figure 4â € â € the ducts 41 are obtained by arranging the longitudinal spacers 45, all having the same height, between two films, preferably again of polyester 42 and 47, and subsequently welding said films and said spacers. In any case, the flexibility of the armature is such as not to prevent winding the membrane 40 according to a coil like the one shown in figure 1. The dimensions of the membrane 20 are preferably: band L close to 1000 mm, width l of each duct around 100 mm, height b equal to 5 mm, and are spaced according to a pitch p equal to 140 mm. The thicknesses of the film 22, of the bituminous layers 23 and of the protective layer 27 respectively are the lowest possible and depend on the production technologies and the operating conditions adopted in production.

Figure 4â € â € can refer both to the case of parallel ducts defined by longitudinal spacers 45, as shown in figure 5â € ™, and to the case of figure 5â €, in which a membrane 50 has cylinders as spacers 48, preferably still in polyester, distributed according to an assigned pattern, to form a single branched duct 54 in each membrane sheet. This scheme is preferable, for example, when high pressure drops cannot be tolerated.

Figure 5 shows a membrane 60 in which said duct forms a coil 62 or a â € œmeanderâ € which has an inlet 63 and an outlet 64 for the heat transfer fluid arranged on the same side with respect to the membrane. This solution is indicated when it is necessary to manage limited flow rates of heat transfer fluid, to enhance turbulence and therefore heat exchange; the arrangement of the lights indicated above also facilitates a rational arrangement of the flow and return manifolds of the heat-carrying fluid The coating of a surface, in particular of a roof, takes place by placing sheets of a membrane parallel to each other and then proceeding with the welding of these sheets in order to ensure that the joints are waterproof. The joints are made with the typical techniques of bitumen-polymeter membranes, in particular with the well-known flame method, also known as â € œflamingâ €. As shown in Figure 6, it provides for arranging membrane sheets parallel to each other, so as to create an overlap 61 along the edges to be welded. To allow the application of this technique, the lateral bands of a membrane, for example the two bands 29 and 39 of the membranes 20 and 30, are devoid of ducts. In the case of membranes of the membrane type 40 (Figures 4â € â € ™ and 4â € â €), this is achieved by placing the spacers 45 at a suitable distance from the edges of the membrane, or by designing the profile 46 appropriately.

The single sheets are cut from a continuous membrane in order to minimize the number of transverse joints, compatibly with the shape of the surface to be coated, and any singularity that this presents; in some cases it may be convenient to use, together with the membrane according to the invention, also the traditional bitumen-polymer membrane, that is, without water ducts and having only waterproofing capacity, and suitable to be welded to the membrane according to the ™ invention.

In the case of membranes with parallel ducts, these are conveniently connected to the hydraulic circuit as schematically indicated in figure 7, where three ducts 71 of a membrane 70 are visible, joined to two manifolds 72 and 73, one for distribution, the other for the collection of water, through fittings 74 and 75. As often required by the geometry of the substrates to be coated, the two collectors 72 and 73 are not parallel to each other, nor perpendicular to the pipes 71, with which they form different angles. The fittings 73 and 74 are therefore characterized by an angle Î ±, corresponding in use to the angle formed by a straight duct 71 and by the normal to the manifold 72 or 73.

Figures 8â € ™ and 8â € respectively show sections of two collectors 80 and 81 each of which can be used for the distribution / collection of the water entering / leaving a membrane according to the invention. The manifolds are preferably extruded, for example, from polyester, or from a material that can perform the same functions, and have one or two quadrangular elements 83 suitable for being engaged by an interlocking section 82 of a joint of the type shown in Figure 9 -11. For the passage of water, and in correspondence with the coupling sections 82, openings 93 are made. The manifolds 80 and 81 have a substantially flat lower face 95, suitable for resting without problems on a flat surface. In particular, the double manifold 80 has quadrangular elements 82 and relative openings 93 on opposite sides with respect to the central body 94; this collector is useful, for example, when two sheets of membrane are to be joined according to sides perpendicular to the winding direction of the membrane. Collector 81, on the other hand, is useful for collecting or distributing water to the ducts of a membrane with a flap arranged, for example, parallel to a cornice or a pitch of a sloping roof.

Figure 8â € â € ™ shows a manifold 89 similar to manifold 80 in figure 8â € ™, which differs from this in the presence of a longitudinal partition 96 which divides the central body 94 into two ducts 97 and 98 to be used one for the distribution and the other for the collection of water to / from respective parallel membranes. To limit the heat exchange between the hot water of one duct and the colder water of the other, which would limit the efficiency of the collection system, a longitudinal interspace 99 is made in the septum 97.

Collectors similar to the manifolds 80 and 89 can be made with a different relative inclination of the two parallel quadrangular elements 93, so as to allow the union of membranes arranged on planes having different positions, and incident in the axis of the manifold.

Figure 9 shows a joint 90 suitable for connecting a duct of a membrane according to the invention to a manifold. It can be made by injection molding, for example, of polyester. This joint has an angle Î ± zero, that is, the joint 90 is suitable for connecting a duct 71 orthogonally to a manifold 73 or 74 (figure 7). As also shown in figures 10 and 11, the joint 90 comprises an interlocking section 82, suitable for gripping a quadrangular element, typically on a protuberance 83 of a manifold 80 or 81 (figures 8â € ™ and 8â €), and a tang 84 adapted to be inserted and welded or glued in place in a duct 71. The tang 84 comprises a section 85 for connection with the section 82, and internally houses a through cavity 86, which constitutes the hydraulic extension of the duct 71 and of the which is the outlet visible; around the outlet there is a seat 87 suitable for housing an o-ring 88 to seal between the joint 90 and the quadrangular element 83.

The above description, of specific embodiments, is able to show the invention from the conceptual point of view so that others, using the known technique, will be able to modify and / or adapt these specific embodiments in various applications without further research and without departing from the inventive concept, and, therefore, it is understood that such adaptations and modifications will be considered as equivalent to the specific embodiments. The means and materials for carrying out the various functions described may be of various nature without thereby departing from the scope of the invention. It is understood that the expressions or terminology used have a purely descriptive purpose and therefore not limitative.

Claims (12)

CLAIMS 1. A lining membrane, in particular a building waterproofing membrane, comprising: - a layer of a mixture containing a bitumen and a polymeric substance; - a support reinforcement of said layer of compound, characterized by the fact of comprising: - a surface capable of capturing solar heat; - a passage duct for a heat transfer fluid, and by the fact that: - said layer of mixture is able to conduct said heat from said surface to said duct, so that said fluid, passing through said duct, receives said heat; - said duct is flexible so as not to hinder the winding / unwinding of said membrane into / from a reel according to a winding / unwinding direction; - said duct has a portion submerged by said layer of compound. 2. A solar panel comprising: - a surface capable of capturing solar heat, - a passage duct for a heat-carrying fluid, - a layer suitable for conducting said heat captured by said surface to said duct, so that said fluid, passing through said duct, receives said heat, characterized in that said layer able to conduct à ̈ a layer of a compound containing a bitumen and a polymeric substance, by the fact that it comprises a support reinforcement of said compound layer and by the fact that: - said duct is flexible so as not to hinder a winding / unwinding operation of said membrane into / from a reel according to a winding / unwinding direction; And - said duct has a portion submerged by said layer of compound. 3. A membrane according to claim 1, in which said layer of mixture is applied on one or both faces of said reinforcement, in particular by means of an impregnation process. 4. A membrane as per claim 1, in which said armature and said duct constitute a single body made by a method chosen from: - extrusion, - fixing said duct to a film, preferably by gluing, - connection of at least two films of predetermined thickness in a plurality of points, in particular by means of spacers of predetermined thickness, between said films there being unconnected areas which define said duct, said or each film being in particular a polyester film, in particular a polyester non-woven fabric film. 5. A membrane as per claim 4, in which said points form continuous lines, so that said unconnected areas constitute a plurality of continuous ducts separated by said continuous lines. 6. A membrane according to claim 1, in which there is a plurality of parallel ducts having an assigned width, preferably spaced with a constant pitch and in which the ratio between said pitch and said width is between 1.3 and 1 , 8. 7. A membrane according to claim 6 wherein said ducts have a substantially rectangular cross-section with width and height respectively parallel and perpendicular to said reinforcement, said width being between 10 and 250 millimeters, in particular between 10 and 30 millimeters or between 80 and 100 millimeters, and said height is between 2 and 10 mm, in particular between 3 and 5 millimeters. 8. A membrane as per claim 6 in which said ducts are parallel to said winding / unwinding direction of said reel. 9. A membrane as per claim 1, wherein said duct forms a coil or meander having an inlet and an outlet for said heat-carrying fluid, said inlet and said outlet being arranged on the same side with respect to said membrane. 10. A membrane as per claim 1, in which said duct or ducts extend out of a lateral strip parallel to said winding / unwinding direction, said strip having a width preferably between 80 and 120 millimeters, said lateral strip being weldable to hot with a similar lateral strip of another bituminous membrane according to claim 1. 11. A membrane according to claim 1, comprising at least two plates, such that said layer of mixture is delimited by said two plates, and said ducts are enclosed between said two plates. 12. Method for making a solar panel according to claim 2 comprising the steps of: - arrangement of an adduction manifold and an abduction manifold of said heat-carrying fluid, - arrangement of a fitting adapted to engage a duct of said membrane in a hermetic connection such that said manifold and said fitting mutually engage, making a preferably removable hermetic connection, in particular a joint.