WO2011048342A2

WO2011048342A2 - Solar collector

Info

Publication number: WO2011048342A2
Application number: PCT/FR2010/052260
Authority: WO
Inventors: Julien Sellier; René Gy; Didier Jousse
Original assignee: Saint-Gobain Glass France
Priority date: 2009-10-22
Filing date: 2010-10-22
Publication date: 2011-04-28
Also published as: US20120222669A1; CN102770721A; FR2951812A1; KR20120098643A; EP2491313A2; JP2013508661A; WO2011048342A3; FR2951812B1

Abstract

The invention relates to a solar collector (1) which includes: a first (2) and a second (4) wall placed opposite one another such as to define a housing (3) therebetween, the first wall (2) being transparent and intended for being positioned on the side on which the solar radiation hits the collector; and a means (6, 7) for absorbing energy from the solar radiation arranged inside the housing (3), said absorption means including at least one conduit (7) carrying a heat-transfer fluid. Furthermore, the collector (1) includes at least one transparent spacer arranged between the first wall (2) and the absorption means (6, 7) on the conduit (7).

Description

SOLAR COLLECTOR

The present invention relates to a planar solar collector intended to be mounted on a structure, in particular a roof or a building facade.

A solar collector is a module capable of converting energy from solar radiation into thermal energy recovered in a heat transfer fluid. Conventionally, a planar solar collector comprises two walls facing one another, which delimit between them a housing for receiving energy conversion elements, generally in the form of an absorber panel heat-connected to one or more heat transfer fluid circulation ducts. At least one of the two facing walls is transparent and intended to be directed to the side of incidence of solar radiation on the collector, so as to allow good transmission of solar radiation to the energy conversion elements.

In order to increase the energy conversion efficiency of such a solar collector, it is known to create a vacuum in the receiving housing of the energy conversion elements, which makes it possible to limit the thermal losses by convection and molecular conduction. In this case, in order to counter the compressive force exerted on the walls of the collector due to the external atmospheric pressure, the collector is equipped with spacers to maintain a constant gap between the facing walls. The energy conversion elements are also advantageously maintained at a distance from the walls delimiting their receiving housing, so as to also limit the thermal losses by contact at these walls.

WO-A-87/06328 discloses a vacuum solar collector structure in which the spacers are in the form of rods, which are supported between the two walls facing the collector. These rods are distributed in the manifold remote from the coolant circulation ducts and pass through the absorber panel. When the rods forming spacers are metallic, thermal losses are likely to intervene at the level of these stems. In addition, as the absorber panel is pierced with holes to allow the passage of these rods, the surface of the active panel for the absorption of energy from solar radiation is reduced, which limits the energy conversion efficiency of the collector. Another disadvantage of this known solar collector structure is that the spacer rods must be placed individually in the collector, which increases the time and cost of manufacturing the collector. In addition, this known collector has a large thickness, which does not allow its aesthetic integration on a roof or a building facade.

It is these drawbacks that the invention intends to remedy more particularly by proposing a solar collector having an optimized structure both in terms of thermal distribution in the collector and in terms of mechanical strength of the collector, making it possible to improve the efficiency. energy collector conversion, this solar collector also having a minimized footprint and a simple manufacturing process.

For this purpose, the subject of the invention is a solar collector comprising:

a first and a second wall facing one another, which delimit between them a housing, the first wall being transparent and intended to be directed towards the side of incidence of the solar radiation on the collector, and

means for absorbing energy from the solar radiation arranged in the housing, these absorption means comprising at least one circulation duct for a heat transfer fluid,

characterized in that it further comprises at least one transparent spacer arranged between the first wall and the absorption means at the duct.

Within the meaning of the invention, a transparent element is a transparent element at least in the wavelength ranges of the solar radiation which are useful for the conversion of the energy from solar radiation into thermal energy by the absorption means. . In addition, a spacer is said arranged between the first wall and the means Absorption level, or plumb, of a duct when positioned between the first wall and the duct, with or without interposition of other absorber elements between the spacer and the duct. The spacer is then in thermal contact with a relatively cooler part of the absorption means, since the heat transfer fluid circulates in the conduit.

Thanks to the arrangement of each spacer in line with a coolant circulation duct, that is to say at a cold point of the absorption means, the heat losses through the spacer are limited. In addition, the transparency of the first wall and of each spacer arranged between the first wall and the absorption means ensures a good transmission of solar radiation to the absorption means of the collector. The collection of energy from solar radiation by the absorption means and the energy conversion efficiency of the collector are thus optimized.

According to other advantageous characteristics of a solar collector according to the invention, taken separately or in any technically possible combination:

- The absorption means comprise an absorber panel thermally connected to the conduit, the spacer being arranged between the first wall and a portion of the absorber panel in thermal contact with the conduit;

the spacer has a rounded shape towards the absorption means;

the spacer is made of glass;

the spacer is integral with the first wall;

the first wall and the spacer are made of toughened glass, the spacer being thermally hardened with the first wall;

the first wall is made of glass and the spacer is a pattern in relief with respect to the first wall obtained by rolling the first wall;

the spacer is a spacer made of chemically toughened glass;

the spacer is less than 4 millimeters thick, preferably less than 2 millimeters thick if it is a chemically quenched spacer, and preferably less than 1 millimeter when it is a monoblock spacer with the first wall;

the collector comprises at least one pair of spacers arranged on either side of the duct, comprising the first spacer between the first wall and the absorption means and a second spacer between the second wall and the absorption means;

the first and second spacers of each pair of spacers are arranged in alignment with one another in a direction transverse to the mean planes of the first and second walls;

the second spacer is integral with the second wall;

the second wall is made of metal and the second spacer is a pattern in relief with respect to the second wall obtained by embossing the second wall;

the second wall is identical to the first wall and symmetrical thereof with respect to a median plane of the collector;

the second spacer is a spacer made of chemically toughened glass;

the second spacer has a thickness of less than 4 millimeters, preferably less than 2 millimeters;

the housing is waterproof and adapted to be evacuated;

the collector comprises a spacer frame between the first and second walls;

the collector has a thickness of less than 30 millimeters, preferably less than 25 millimeters;

- A free edge of the first wall protrudes from the corresponding free edge of the second wall so that the first wall of the solar collector is adapted to partially cover the first wall of a second similar solar collector juxtaposed to the first solar collector.

The invention also relates to a covering assembly for a structure, in particular a roof or a building facade, comprising at least one solar collector as described above. The characteristics and advantages of the invention will appear in the following description of four embodiments of a solar collector according to the invention, given solely by way of example and with reference to the appended drawings in which:

- Figure 1 is a section of a solar collector according to a first embodiment of the invention;

FIG. 2 is a section similar to FIG. 1 for a solar collector according to a second embodiment of the invention;

FIG. 3 is a section similar to FIG. 1 for a solar collector according to a third embodiment of the invention;

- Figure 4 is a schematic top view of two solar collectors according to the invention mounted on a structure, for example a roof or a building facade; and

- Figure 5 is a side view of a roof structure on which are mounted solar collectors according to a fourth embodiment of the invention.

For clarity of the drawing, the relative dimensions of the various elements in Figures 1 to 5 have not been strictly observed.

The solar collector 1 of the first embodiment, shown in Figure 1, comprises a transparent upper wall 2, intended to be directed to the side of incidence of solar radiation on the collector, and a lower wall 4 also transparent. The walls 2 and 4 are formed by two identical tempered glass plates of rectangular shape and thickness of the order of 4 to 6 millimeters. The walls 2 and 4 are connected to each other by means of a metal frame 5, so that they delimit between themselves and with the frame 5 a housing 3 for receiving the absorption means of the collector 1. In the assembled configuration of the collector 1, the mean planes π and π 'of the walls 2 and 4 are substantially parallel to each other. Z is a direction of thickness of the collector 1, which is substantially perpendicular to the mean planes π and π '.

Each of the walls 2 and 4 is fixed to the frame 5 by means of a seal seal 10 tight, especially gastight. Of Preferably, the seal 10 between the metal frame 5 and each glass wall 2 or 4 is obtained by brazing, by means of a solder alloy, between the frame and a metal frit deposited on the glass wall. This metal frit, comprising a glass frit and metal particles, is advantageously deposited by screen printing on the periphery of the face of the glass wall 2 or 4 intended to be in contact with the frame 5, and then fired during thermal quenching. of the glass wall 2 or 4. The sealing gasket 10 obtained between the glass and the metal has good characteristics of mechanical strength and sealing in the long term. In particular, the sealing gasket 10 makes it possible to put the housing 3 in vacuo under vacuum and hold it in which the collector absorption means are arranged.

These absorption means comprise a metal panel 6, also called absorber panel, and a conduit 7 for circulating a heat transfer fluid. The coolant is for example water, optionally mixed with an antifreeze. The absorber panel 6 is arranged between the upper wall 2 and the heat transfer fluid circulation duct 7, so that it is able to store heat from the solar radiation passing through the wall 2, this heat being then transferred from the panel absorber 6 to the fluid flowing in the duct 7. For this purpose, the duct 7 is in thermal contact with the lower face 6A of the absorber panel 6 directed towards the lower wall 4. More specifically, the duct 7 is positioned against the lower face 6A the absorber panel 6 in the form of a coil, so as to maximize the thermal contact area between the conduit and the absorber panel. As shown in FIG. 1, the absorption means 6 and 7 are preferably maintained at a median plane P of the collector, at a distance from the walls 2 and 4, so as to limit thermal losses by contact at the level of these walls. The absorber panel 6, in particular made of copper or aluminum, has a thickness in the Z direction of the order of 0.1 to 1 millimeter. The duct 7, in particular made of copper, has a circular section having a diameter of the order of 8 mm. The duct 7 opens outwardly from the collector 1 at two connectors 1 1 for entering and leaving the heat transfer fluid, shown schematically in FIG. 4. Preferably, the two connectors 1 1 are provided on the same wafer. manifold 1, that is to say, are located in the same side 51 of the frame 5 of rectangular shape, being positioned each adjacent a 51 A or 51 B end 51 side. When the collector 1 is mounted on a structure 12 inclined relative to the horizontal, such as a roof or facade, the side 51 of the frame 5 comprising the connectors 1 1 is preferably positioned the highest in relation to the other sides of the frame. It is then easy, when two collectors 1 are juxtaposed on the structure 12 to form a covering assembly 20 as shown in FIG. 4, to connect the input connector of a first collector 1 with the output connector of the second collector 1 juxtaposed, for example by means of a pipe 13 U. This forms a solar collector system in which the heat transfer fluid can flow successively in a plurality of collectors.

A plurality of spacers 8 and 9, in the form of pads, is provided in the manifold 1 to maintain a constant distance between the upper wall 2 and the bottom wall 4 when the collector is evacuated. The collector 1 thus comprises a first series of spacers 8, said upper spacers, which are positioned between the upper wall 2 and the absorption means, and a second series of spacers 9, called lower spacers, which are positioned between the lower wall 4 and the absorption means. The spacers 8, 9 are distributed in the collector 1 so as to form pairs of spacers. Each pair of spacers comprises an upper spacer 8 and a lower spacer 9 which are substantially aligned in the Z direction and arranged on either side of the absorption means, each at the level of the duct 7.

More specifically, each upper spacer 8 is positioned between the upper wall 2 and a portion 61 of the absorber panel 6 which is in thermal contact with the duct 7, while each lower spacer 9 is positioned between the bottom wall 4 and the duct 7. The spatial arrangement spacers 8, 9 each at a portion of the duct 7 limits the heat losses through the spacers from the absorption means 6 and 7. Indeed, the duct 7 and the parts 61 of the panel absorber 6, which are in thermal contact with the conduit 7, are cold zones in the thermal distribution of the absorption means, which limits the risk of thermal leakage through the spacers.

In this first embodiment, each spacer 8 or 9 is a pattern projecting from the corresponding wall 2 or 4, formed by rolling the glass plate constituting the wall 2 or 4. In other words, the series of upper spacers 8 is a surface texturing of the upper wall 2, obtained by rolling the flat surface of the glass plate constituting the wall 2, by heating the glass plate to a temperature at which it is possible to to deform its surface using a solid object such as a metal roller having on its surface the opposite shape of the texturing to be formed. Similarly, the series of lower spacers 9 is a surface texturing of the bottom wall 4, obtained by rolling the flat surface of the glass plate constituting the wall 2. Advantageously, the rolled spacers 8 and 9 are soaked during the thermal quenching of the walls 2 and 4. There are thus obtained spacers 8 and 9 which are incorporated in the glass wall 2 or 4 and which have good characteristics of transparency and mechanical strength.

In the second embodiment shown in FIG. 2, elements similar to those of the first embodiment carry identical references increased by 100. The solar collector 101 according to this second embodiment differs from the solar collector 1 of the first embodiment of FIG. realization by the structure of its spacers 108 and 109. As in the first embodiment, the solar collector 101 comprises a top wall 102 transparent and a bottom wall 104 also transparent, formed by two identical plates tempered glass thermally. The walls 102 and 104 delimit between themselves and with a metal frame 105, to which they are fixed by a sealing gasket 1 10 sealed, a housing 103 sealed receiving means absorption 106 and 107 of the collector. These absorption means, which are similar to those of the first embodiment, comprise an absorber panel 106 and a conduit 107 for circulating a heat transfer fluid. As in the first embodiment, the conduit 107 is in thermal contact with the absorber panel 106 on the underside side 106A thereof.

The manifold 101 includes a plurality of upper spacers 108 and a plurality of lower spacers 109 for maintaining a constant distance between the top wall 102 and the bottom wall 104 when the manifold 101 is evacuated. As in the first embodiment, these spacers 108 and 109 are aligned in pairs along the thickness Z direction of the manifold 101, so that each upper spacer 108 is positioned between the top wall 102 and a portion 161 of the absorber panel. 106 which is in thermal contact with the conduit 107, while each lower spacer 109 is positioned between the lower wall 104 and the conduit 107. However, in this second embodiment, the spacers 108 and 109 are not in the form of relief patterns obtained by rolling, but in the form of glass beads reported on the walls 102 and 104, for example by gluing. In order to resist the compressive force exerted on the walls 102 and 104 when the vacuum is made in the housing 103, the glass beads are reinforced by chemical quenching. This chemical quenching treatment aims, by ion exchange, to replace alkaline ions initially in the glass and close to the surface with other larger alkaline ions, in order to induce high compressive stresses on the surface. Chemical quenching thus makes it possible to significantly increase the mechanical strength of the balls.

For this chemical quenching treatment, the constituent glass of the balls must contain, before quenching, an alkaline oxide. As non-limiting examples, the initial oxide may be Na 2 O, the chemical quenching can then be performed by KNO3 treatment, so as to replace at least partially Na ⁺ ions by K ⁺ ions; the initial oxide can also be Li ₂ O, the chemical quenching can then be carried out by treatment with NaNO3 or KNO3, so as to at least partially replace Li ⁺ ions with Na ⁺ or K ⁺ ions. The chemical quenching leads to a concentration gradient of ions, in particular K ⁺ or Na ⁺ , perpendicular to the treated surfaces and decreasing from these surfaces. In practice, for example in the case of sodium / potassium exchange, the ion exchange is carried out by quenching the glass beads in a potassium salt bath heated to temperatures between 400 and 500 ° C. The parameters of the ion exchange, in particular temperature and duration, are chosen so as to favor a high surface stress. Ion exchange can also be assisted by an electric field.

In the third embodiment shown in FIG. 3, elements similar to those of the first embodiment bear identical references increased by 200. The solar collector 201 according to this third embodiment differs from the solar collector 1 of the first embodiment of FIG. realization in that its lower wall 204 is metallic. More specifically, the solar collector 201 comprises a transparent upper wall 202, formed by a thermally tempered glass plate, and a metal tank 215. The metal tank 215 comprises a bottom 204 which forms a lower wall of the collector 201, as well as a lateral edge 205 which extends substantially perpendicular to the bottom 204. The upper wall 202 is connected to the free edge of the edge 205 by means of a sealing seal 210 sealed, in particular gas-tight. As before, the seal 210 between the metal edge 205 and the top glass wall 202 is preferably obtained by brazing between the free edge of the edge 205 and a metal frit deposited on the upper wall 202. The walls 202 and 204 delimit between them and with the edge 205 a sealed housing 203, in which are received the absorption means 206 and 207 of the collector 201, comprising an absorber panel 206 and a conduit 207 for circulating a heat transfer fluid which is in thermal contact with the absorber panel 206 on the underside side 206A thereof. As in the previous embodiments, the manifold 201 comprises a plurality of upper spacers 208 and a plurality of lower spacers 209, aligned in pairs along the thickness Z direction of the manifold 201 and adapted to maintain a constant distance between the upper wall 202 and the bottom wall 204 when the collector 201 is evacuated. Each upper spacer 208 is positioned between the upper wall 202 and a portion 261 of the absorber panel 206 which is in thermal contact with the conduit 207, while each lower spacer 209 is positioned between the bottom wall 204 and the conduit 207.

In this third embodiment, the upper spacers 208 are patterns projecting from the upper wall 202, formed by rolling the glass plate constituting the wall 202, and which are advantageously quenched during the thermal quenching of the 202. The lower spacers 209 are in turn patterns projecting from the bottom wall 204, formed by embossing the metal wall 204. Advantageously, an insulating plate 214 is added between the conduit 207 and the lower metallic spacers 209. to reduce heat losses. This plate is preferably non-porous to facilitate the evacuation of the collector, and may be for example glass or ceramic, with a thickness of the order of 1 to 4 millimeters. When such an insulating plate is present in the manifold 201 between the conduit 207 and the lower spacers 209, the lower spacers 209 are preferably aligned with the conduit 207 in the Z direction, but not necessarily.

Whatever the embodiment, each upper spacer 8, 108, 208 or lower 9, 109, 209 has a thickness es, eioe, β2οβ or eg, eio9, β209 less than 4 millimeters, preferably less than 2 millimeters. More specifically, when the spacers are glass balls having undergone a chemical quenching treatment as in the second embodiment, these beads preferably have a thickness of less than 2 millimeters. When the spacers are made of glass, monoblocks with a glass wall of the collector and thermally quenched during the thermal quenching of the wall, as is the case for the rolled spacers 8, 9 and 208 of the first and third embodiments, these spacers preferably have a thickness of less than 1 millimeter.

In addition, each spacer 8, 108, 208, 9, 109, 209 preferably has a rounded shape towards the absorption means, in particular a spherical or hemispherical shape, so as to minimize the contact surface between the spacer. and the absorption means and thus to limit heat losses through the spacer. A minimization of the density of the spacers on each of the upper and lower walls is also sought, in particular by maximizing the value of the pitch p between the spacers, in order to limit thermal losses through the spacers. More precisely, the value of the pitch p_ between the spacers on each wall is adjusted so as to achieve a compromise between, on the one hand, the minimization of the thermal losses by the spacers and, on the other hand, the distribution of the stresses in the wall. Indeed, an increase of the pitch p_ between the spacers causes an increase in the concentration of the mechanical stresses generated in the wall, and therefore the risk of breakage of this wall when it is glass. A good compromise is obtained for a value of the pitch p between the spacers of between 20 and 100 millimeters.

As is apparent from the three embodiments described above, a solar collector according to the invention ensures good transmission of solar radiation to the collector absorption means through both the transparency of the upper wall and the transparency of the upper spacers. In particular, thanks to the transparency of the upper spacers, the entire active surface of the absorber panel is exposed to solar radiation, which improves the energy recovery by the absorber panel. Preferably, the upper wall and / or the upper spacers consist of a clear or extra-clear transparent glass, with a very low iron oxide content, such as the glass marketed by Saint-Gobain Glass in the "DIAMOND" range or , especially in the case where the upper spacers are patterns in relief obtained by rolling the upper wall of the collector, in the range "ALBARINO" manufactured by rolling.

A solar collector in accordance with the invention also makes it possible to limit heat losses by, on the one hand, vacuuming the receiving housing of the absorption means and, on the other hand, the specific arrangement of the spacers. in the collector. The positioning of the spacers at the cold points of the absorption means, directly above the heat transfer fluid circulation duct, makes it possible to reduce the heat losses through the spacers, as well as the rounded shape of each spacer. direction of the absorption means, which allows a minimization of the contact surface between the spacer and the absorption means. The reinforcement of the spacers, in particular by thermal or chemical quenching in the case of glass spacers, also makes it possible to reduce the number of spacers necessary to ensure the mechanical strength of the collector, which further contributes to reducing heat losses through the spacers.

Due to the improvement of energy recovery by the absorber panel and the reduction of heat losses, a solar collector according to the invention can have a higher energy conversion efficiency than the solar collector efficiency of the state of the solar collector. technical.

A solar collector according to the invention can also have a very compact structure thanks, on the one hand, to the use of walls and spacers of tempered glass or metal which, even when they have relatively small thicknesses, have good mechanical strength and, secondly, the ability to effectively maintain a vacuum in the receiving housing of the absorption means by the establishment of a glass-metal seal as described above. According to the invention, the thickness ei, eioi, β2οι of the solar collector is less than 30 millimeters, preferably less than 25 millimeters. Thanks to its compactness, a solar collector according to the invention can be integrated easily and aesthetically on a roof or a building facade. The use of a tempered glass plate as the top wall guarantees good collector resistance to weather when mounted on a roof or building facade. In addition, due to its evacuation, a solar collector according to the invention can strengthen the thermal insulation at the roof or facade it equips.

Furthermore, a solar collector according to the invention, when it comprises spacers formed collectively on a wall of the collector, eliminates the need to set up the spacers one by one in the collector. This is particularly the case when the collector comprises rolled or embossed spacers as described above, or spacers formed by screen printing, in a single passage of doctor blade, a glass frit on the wall and then baking this glass frit. Thanks to this collective manufacture of spacers, the manufacturing process of the solar collector is simpler and faster, which is advantageous for manufacturing on an industrial scale.

A solar collector according to the invention is advantageously part of a cladding assembly 20, 320 intended to be mounted on a structure, such as a roof or a building facade, where the cladding assembly 20, 320 comprises other elements, in particular other solar collectors and / or photovoltaic modules and / or conventional tiles or slates. The various elements of the cladding assembly 20, 320 are preferably arranged relative to each other in a staggered arrangement, in the manner of tiles or slates, and assembled together by means of non-adjustable fastening means. shown, for example hooks and rails with sawtooth edges as described in US-A-2003/0213201. As illustrated in the fourth embodiment shown in FIG. 5, the form of solar collectors according to the invention can also be adapted to facilitate a staged arrangement of the collectors on a roof or a building facade, with an overlap in the manner of tiles or slates.

In this fourth embodiment, elements similar to those of the first embodiment carry identical references increased by 300. Each solar collector 301 conforms to this fourth embodiment. embodiment has the same structure as any of the collectors 1, 101, 201 described above, except that the top wall 302 of the manifold 301 is provided with a height h ₃ 02 in a height direction Y of the collector 301, greater than the height in the Y direction of the underlying parts of the collector, and in particular greater than the height h ₃ 04 of the bottom wall 304 of the manifold. Moreover, in the assembled configuration of the collector 301, the walls 302 and 304 are arranged such that two opposite free edges 321 and 323 of the upper wall 302 protrude by a distance d relative to the corresponding free edges 341 and 343 of the bottom wall 304.

When the receiving structure of the collector 301 is inclined relative to the horizontal, as is the case of the structure 312 shown in Figure 5, the collector 301 is intended to be mounted on the structure with its height direction Y substantially aligned with the direction of inclination of the structure relative to the horizontal. Thus, in assembled configuration of the collector 301 on the inclined structure 312, the upper wall 302 of the collector 301 is able to partially cover the upper wall 302 of a second similar collector 301, mounted on the structure 312 being juxtaposed below the first manifold 301 according to the direction of inclination of the structure. This produces a cladding assembly 320 comprising several collectors 301 with the desired staged arrangement, in the manner of tiles, on the structure. Such a staggered arrangement of the collectors 301 allows a good watertightness of the covering assembly 320, even in the event of a strong wind.

The invention is not limited to the examples described and shown. In particular :

- The upper and lower spacers may not be monoblock with the walls of the solar collector, but reported on these walls by any suitable means, including gluing or welding;

- The upper spacers may be made of any transparent material, other than glass and adapted to withstand high mechanical stresses in compression, for example plastic; - The lower spacers may be made of any material, transparent or not, able to withstand high mechanical stresses in compression, for example glass, metal, ceramic;

glass spacers incorporated in a glass wall of the solar collector may be obtained by techniques other than rolling, in particular by depositing a glass frit on the wall, or by screen printing, which allows the deposition of all the spacers in a single doctor blade passage, or by means of a dispenser, which makes it possible to deposit relatively thick spacers, the firing of the frit having in all cases advantageously taking place during the thermal quenching of the wall; as in the case of laminated spacers, these one-piece glass spacers with a glass wall preferably have a thickness of less than 1 millimeter;

in the case where the upper spacers are obtained by rolling the glass top wall of the solar collector, the face of the upper wall intended to be turned towards the outside of the collector can also be laminated so as to present a non-slip texturing; this is particularly interesting when the solar collector is installed on a roof of the building, in order to avoid any fall of a person moving on the roof;

the face of the upper wall intended to be turned towards the outside of the collector can also be laminated so as to present a texturization of lenticular type making it possible to visualize an image on the surface of the solar collector without obstructing the direct solar rays, such as as described in FR-A-2 896 596;

the upper and lower spacers may be of any form adapted to their function, preferably rounded towards the absorption means; the upper and lower spacers may in particular be in the form of circular or polygonal section pads, as described above, or in the form of elongated segments whose longitudinal direction preferably extends transversely to the longitudinal direction of the or each coolant circulation duct; in the case of a collector comprising a metal bottom wall, this wall may be corrugated so as to form projecting segments as lower spacers;

- To improve the mechanical strength of the solar collector, the upper and / or lower wall of the collector when it is made of glass can be assembled with another sheet of glass via a polymeric interlayer to form a laminated glass plate;

- In order to protect the seal between a glass wall and the frame or metal tray of the collector vis-à-vis thermal stresses likely to cause degradation of the seal and thus the sealing of the collector, especially in the vicinity connectors implanted in the frame or metal tray, the frame or metal tray may comprise, for its junction with the glass wall, a thinner wall offset outwardly relative to the seal, beyond the edges of the glass wall, so as to create an insulating empty space directly above the glass-metal junction zone;

the collector may comprise several heat transfer fluid circulation ducts instead of a single serpentine-shaped duct;

the or each heat transfer fluid circulation duct may, instead of being an independent duct of the absorber panel as shown in FIGS. 1 to 3, be formed at least in part by the absorber panel, for example by securing a U-shaped piece with the underside of the absorber panel;

the absorption means arranged in the solar collector housing may comprise, in addition to means for converting energy from solar radiation into thermal energy, such as an absorber panel and a heat transfer fluid circulation duct, as described previously, means for converting energy from solar radiation into electrical energy, such as photovoltaic cells.

Claims

1. Solar collector (1; 101; 201; 301) comprising:

- a first (2; 102; 202; 302) and a second (4; 104; 204; 304) walls facing one another, which delimit between them a housing (3;

103; 203), the first wall (2; 102; 202; 302) being transparent and intended to be directed towards the side of incidence of solar radiation on the collector, and

means (6, 7; 106, 107, 206, 207) for absorbing energy from the solar radiation arranged in the housing (3; 103; 203), said absorption means comprising at least one duct (7; 107, 207) for circulating a heat transfer fluid,

characterized in that it further comprises at least one transparent spacer (8; 108; 208) arranged between the first wall (2; 102; 202; 302) and the absorption means (6,7; 106,107; 206, 207) at the duct (7; 107; 207).

2. Solar collector according to claim 1, characterized in that the absorption means comprise an absorber panel (6; 106; 206) thermally connected to the conduit (7; 107; 207), the spacer (8; 108; 208). ) being arranged between the first wall (2; 102; 202; 302) and a portion (61; 161; 261) of the absorber panel (6; 106; 206) in thermal contact with the conduit (7; 107; 207).

3. solar collector according to any one of claims 1 or 2, characterized in that the spacer (8; 108; 208) has a rounded shape towards the absorption means (6, 7; 106, 107; 206). , 207).

4. solar collector according to any one of the preceding claims, characterized in that the spacer (8; 208) is integral with the first wall (2; 202).

Solar collector according to claim 4, characterized in that the first wall (2; 202) and the spacer (8; 208) are made of toughened glass, the spacer being thermally quenched with the first wall.

6. solar collector according to any one of the preceding claims, characterized in that the first wall (2; 202) is made of glass, the spacer (8; 208) being a pattern in relief with respect to the first wall (2 202) obtained by rolling the first wall.

Solar collector according to any one of claims 1 to 3, characterized in that the spacer (108) is a spacer of chemically hardened glass.

8. solar collector according to any one of the preceding claims, characterized in that the spacer (8; 108; 208) has a thickness (es; eioe; β2οβ) less than 4 millimeters, preferably less than 2 millimeters.

9. solar collector according to any one of the preceding claims, characterized in that it comprises at least one pair of spacers arranged on either side of the conduit (7; 107; 207), comprising the first spacer (8 108; 208) between the first wall (2; 102; 202; 302) and the absorption means and a second spacer (9; 109; 209) between the second wall (4; 104; 204; 304) and absorption means.

10. Solar collector according to claim 9, characterized in that the second wall (204) is metal, the second spacer (209) being a pattern in relief relative to the second wall (204) obtained by embossing the second wall .

1 1. Solar collector according to claim 9, characterized in that the second wall (4; 104) is identical to and symmetrical with the first wall (2; 102) with respect to a median plane (P) of the collector.

12. solar collector according to any one of the preceding claims, characterized in that the housing (3; 103; 203) is sealed and adapted to be evacuated.

13. solar collector according to any one of the preceding claims, characterized in that it comprises a spacer frame (5; 105) between the first (2; 102) and second (4; 104) walls.

14. solar collector according to any one of the preceding claims, characterized in that it has a thickness (ei; ei; θ2οι) less than 30 millimeters, preferably less than 25 millimeters.

15. Cover assembly (20; 320) for a structure (12; 312), in particular a roof or a building facade, characterized in that it comprises at least one solar collector (1; 101; 201; 301). according to any one of claims 1 to 14.